Zoom lens and imaging device having the same

Abstract

To provide a wide-angle, compact zoom lens that is robust against manufacturing errors and yet provides high optical performance. [Solution] The zoom lens comprises, arranged in order from the object side to the image side, 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 rear group including two or more lens groups, and the spacing between adjacent lens groups changes during zooming. The first lens group moves during zooming. If the third lens group or the lens group arranged adjacent to the third lens group on the image side has positive refractive power, the lens group consisting of the third lens group and the lens group with positive refractive power is defined as a positive group. The positive group includes a first cemented lens with negative refractive power and a second cemented lens with positive refractive power arranged on the image side of the first cemented lens, and the first cemented lens consists of a first lens with positive refractive power and a second lens with negative refractive power. The positive group satisfies a predetermined conditional expression.

Description

[Technical Field]

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

[0002] Conventionally, in zoom lenses used in photographic cameras and video cameras, inner focusing and rear focusing methods have been proposed, in which the lens group behind the first lens group on the object side (on the image side) is moved to achieve focusing.

[0003] Furthermore, digital cameras and video cameras are seeing increased pixel counts in solid-state image sensors such as CCDs and CMOS sensors. In addition, photographic lenses are required to have high optical performance, including chromatic aberration, while also becoming smaller.

[0004] Patent Document 1 discloses a zoom lens with a five-group configuration consisting of lens groups with refractive powers of positive, negative, positive, negative, and positive in that order from the object side. Patent Document 1 reduces the number of lenses by employing an aspherical lens in the fourth lens group.

[0005] Patent Document 2 discloses a zoom lens with a five-group configuration, consisting of lens groups with positive, negative, positive, negative, and negative refractive powers, arranged in order from the object side. Patent Document 2 achieves a high zoom ratio by optimizing the refractive power of each group. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-102525 [Patent Document 2] Japanese Patent Publication No. 2015-018124 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, there has been a strong demand for lens systems used in imaging devices that are compact overall while possessing high optical performance. To achieve good optical performance while miniaturizing the entire lens system, it is important to appropriately set the refractive power and configuration of each lens group, as well as the movement conditions of each lens group during zooming. In particular, when miniaturizing the lens system in cameras with large image sensors, high refractive index glass materials are often used extensively, and it is necessary to suppress chromatic aberration while ensuring robustness against lens polarization.

[0008] As shown in Patent Document 1, it is possible to shorten the overall lens length by using many aspherical lenses and increasing the refractive power of each lens, but it is difficult to suppress axial chromatic aberration across the entire zoom range.

[0009] As described in Patent Document 2, when a high zoom ratio is achieved while maintaining a telephoto focal length, it becomes difficult to suppress various aberrations at the wide-angle end, particularly chromatic aberration, making it difficult to achieve a wider field of view.

[0010] The present invention aims to provide a compact, wide-angle zoom lens that is robust against manufacturing errors while achieving high optical performance. [Means for solving the problem]

[0011] A zoom lens as one aspect of the present invention comprises 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 rear group including two or more lens groups, arranged sequentially from the object side to the image side, wherein the spacing between adjacent lens groups changes during zooming, and when zooming from the wide-angle end to the telephoto end, the first lens group moves, the spacing between the first and second lens groups widens, and the spacing between the second and third lens groups narrows, and when the third lens group, or a lens group arranged continuously on the image side relative to the third lens group, is a lens group with positive refractive power, the lens group composed of the third lens group and the lens group with positive refractive power is called the positive group, and the positive group comprises a first cemented lens with negative refractive power and on the image side of the first cemented lens Next to each other It includes a second cemented lens having positive refractive power, wherein the first cemented lens is It consists of a first lens with positive refractive power and a biconvex shape, and a second lens with negative refractive power, arranged sequentially from the object side to the image side. When the focal length of the positive lens group at its wide-angle end is fGP, the focal length of the second lens is fAN, and the refractive index of the second lens at the d-line is ndAN, -1.200 <fAN / fGP<-0.795 1.45 <ndAN<1.64 It is characterized by satisfying the following conditional expression.

[0012] Other objects and features of the present invention are described in the following embodiments. [Effects of the Invention]

[0013] According to the present invention, a compact zoom lens with a wide field of view can be realized that is robust against manufacturing errors while providing high optical performance. [Brief explanation of the drawing]

[0014] [Figure 1] These are cross-sectional views of the zoom lens of Example 1 at its wide-angle end, intermediate zoom position, and telephoto end. [Figure 2] This is an aberration diagram of the zoom lens of Example 1 at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C). [Figure 3]It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 2. [Figure 4] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 2. [Figure 5] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 3. [Figure 6] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 3. [Figure 7] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 4. [Figure 8] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 4. [Figure 9] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 5. [Figure 10] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 5. [Figure 11] It is a lens cross-sectional view at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 6. [Figure 12] It is an aberration diagram at the wide-angle end (A), intermediate zoom position (B), and telephoto end (C) of the zoom lens of Example 6. [Figure 13] It is a schematic diagram of an imaging device.

Modes for Carrying Out the Invention

[0015] Hereinafter, examples of the zoom lens of the present invention and an imaging device having the same will be described based on the accompanying drawings.

[0016] Figure 1 is a cross-sectional view of the zoom lens of Example 1 at its wide-angle end (short focal length end), intermediate zoom position, and telephoto end (long focal length end). Figures 2(A), 2(B), and 2(C) are aberration diagrams of the zoom lens of Example 1 at its wide-angle end, intermediate zoom position, and telephoto end, respectively. The aberration diagrams for each example are for when the zoom lens is focused on an object at infinity. The zoom lens of Example 1 is a zoom lens with a zoom ratio of approximately 4.4 and an aperture ratio of approximately 4.1.

[0017] Figure 3 is a cross-sectional view of the zoom lens of Example 2 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 4(A), 4(B), and 4(C) are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 2 is a zoom lens with a zoom ratio of 4.4 and an aperture ratio of approximately 2.9 to 4.1.

[0018] Figure 5 is a cross-sectional view of the zoom lens of Example 3 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 6(A), 6(B), and 6(C) are aberration diagrams of the zoom lens of Example 3 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 3 is a zoom lens with a zoom ratio of 4.4 and an aperture ratio of approximately 2.9 to 4.1.

[0019] Figure 7 is a cross-sectional view of the zoom lens of Example 4 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 8(A), 8(B), and 8(C) are aberration diagrams of the zoom lens of Example 4 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 4 is a zoom lens with a zoom ratio of 5.4 and an aperture ratio of approximately 2.9 to 5.8.

[0020] Figure 9 is a cross-sectional view of the zoom lens of Example 5 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 10(A), 10(B), and 10(C) are aberration diagrams of the zoom lens of Example 5 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 5 is a zoom lens with a zoom ratio of 5.1 and an aperture ratio of approximately 2.9 to 5.8.

[0021] Figure 11 is a cross-sectional view of the zoom lens of Example 6 at the wide-angle end, intermediate zoom position, and telephoto end. Figures 12(A), 12(B), and 12(C) are aberration diagrams of the zoom lens of Example 6 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. The zoom lens of Example 6 is a zoom lens with a zoom ratio of 5.1 and an aperture ratio of approximately 2.9 to 5.8.

[0022] The zoom lenses in each embodiment are imaging optical systems used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras. Furthermore, the zoom lenses in each embodiment can also be used as projection optical systems for projection devices (projectors).

[0023] In each cross-sectional view of the lens, the left side is the object side (front) and the right side is the image side (rear). The zoom lens of each embodiment is composed of multiple lens groups. In this specification, a lens group is a collection of lenses that move or remain stationary as a whole during zooming. That is, in the zoom lens 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. Furthermore, a lens group may include an aperture diaphragm.

[0024] In each lens cross-sectional view, if i represents the order of the lens group from the object side, then Li represents the i-th lens group. SP is the aperture diaphragm that determines (limits) the light beam at the open F-number (Fno). IP is the image plane, and when the zoom lens of each embodiment is used as the imaging optical system of a digital still camera or digital video camera, the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is located there. When the zoom lens of each embodiment is used as the imaging optical system of a silver halide film camera, a photosensitive surface corresponding to the film plane is placed on the image plane IP. The arrows related to focus indicate the direction of movement of the lens group when focusing from infinity to near distance.

[0025] In the spherical aberration diagram, Fno is the F-number and indicates the amount of spherical aberration for the d-line (wavelength 587.56 nm) and the g-line (wavelength 435.835 nm). In the astigmatism diagram, ΔS indicates the amount of astigmatism on the sagittal image plane, and ΔM indicates the amount of astigmatism on the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration for the g-line is shown. ω is the half-angle of view (°) and is the angle of view determined by ray tracing. In each of the following embodiments, the wide-angle end and telephoto end refer to the zoom positions when the lens group for zooming is located at both ends of the range in which it can move along the optical axis due to the mechanism.

[0026] Next, we will describe the characteristic configurations of the zoom lenses in each embodiment.

[0027] The zoom lens in each embodiment consists of a first lens group L1 with positive refractive power (optical power = reciprocal of focal length), a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, and a rear group RG including one or more lens groups, arranged sequentially from the object side to the image side. In other words, the zoom lens consists of four or more lens groups. The spacing between adjacent lens groups changes when zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves, the spacing between the first lens group L1 and the second lens group L2 widens, and the spacing between the second lens group L2 and the third lens group L3 narrows. If the third lens group L3, or a lens group arranged continuously on the image side relative to the third lens group L3, is a lens group with positive refractive power, the lens group consisting of the third lens group L3 and the lens group with positive refractive power is called lens group GP (positive group). In this case, the lens group GP includes a cemented lens A (first cemented lens) with negative refractive power and a cemented lens B (second cemented lens) with positive refractive power, arranged in order from the object side to the image side. The cemented lens A consists of a biconvex lens AP (first lens) with positive refractive power and a lens AN (second lens) with negative refractive power, arranged in order from the object side to the image side.

[0028] Furthermore, the zoom lens of each embodiment satisfies the following conditions (1) and (2).

[0029] -1.200 <fAN / fGP<-0.795 ···(1) 0.001<|APR2 / APR1|<1.150 ···(2) Here, fGP is the focal length of the lens group GP at its wide-angle end, and fAN is the focal length of the negative lens AN as a single lens. APR1 and APR2 are the object-side and image-side radii of the positive lens AP, respectively.

[0030] Each embodiment of the zoom lens is configured to have first to third lens groups with positive, negative, and positive refractive powers arranged sequentially from the object side to the image side, in order to shorten the overall length of the lens at the wide-angle end while effectively correcting aberrations throughout the entire zoom range. By having a configuration consisting of at least four groups, spherical aberration and coma aberration occurring in the first lens group L1 and the second lens group L2 are effectively corrected. Furthermore, in the telephoto range, variations in spherical aberration and coma aberration due to manufacturing tolerances become larger. For this reason, each embodiment of the zoom lens is a so-called positive-lead type zoom lens in which the first lens group L1 has positive refractive power, and the incident height of on-axial light rays is suppressed for each lens element on the image side from the second lens group L2 onwards, thereby improving miniaturization and robustness.

[0031] Furthermore, in order to achieve miniaturization and ensure a high magnification ratio, the spacing between each lens group is changed so that the distance between the first lens group L1 and the second lens group L2 is wider at the telephoto end compared to the wide-angle end, and the distance between the second lens group L2 and the third lens group L3 is narrower, and zooming is performed accordingly.

[0032] The lens group GP consists of the third lens group L3, or, if the lens group arranged continuously on the image side relative to the third lens group L3 is a lens group with positive refractive power, then the lens group GP consists of the third lens group L3 and the lens group with positive refractive power. Furthermore, the lens group GP includes a cemented lens A with negative refractive power and a cemented lens B with positive refractive power, arranged sequentially from the object side to the image side. The lens group GP that performs zooming has positive refractive power as a whole and has multiple lenses. In order to achieve miniaturization and suppress fluctuations in spherical aberration and coma aberration due to zooming, the spacing of some of the lens groups with positive refractive power may be changed.

[0033] The cemented lens A consists of a biconvex positive lens AP and a negative lens AN, arranged sequentially from the object side to the image side. By incorporating cemented lens A, it becomes easier to suppress wavelength-dependent variations in spherical aberration and coma aberration, which are challenges when increasing aperture size. Furthermore, when the refractive power of the positive lens AP is increased, the radius of curvature decreases. As a result, by incorporating cemented lens A, robustness against manufacturing errors in coma aberration caused by eccentricity is ensured, making it easier to secure good optical performance.

[0034] When the refractive index of the negative lens AN is increased relative to the positive lens AP, the cemented surface exhibits divergence, which is unfavorable for correcting chromatic aberration but makes it easier to correct spherical aberration. Conversely, when the refractive index is increased, the cemented surface exhibits convergence, which is advantageous for correcting chromatic aberration but makes it difficult to correct spherical aberration. Therefore, by placing cemented lens B on the image side of cemented lens A, and using a configuration with two sets of cemented lenses, it is possible to compensate for insufficient correction of various aberrations caused by the selection of glass materials and suppress various aberrations without using many aspherical lenses.

[0035] Conditional equation (1) defines the focal length of the negative lens AN as the focal length of the lens group GP at the wide-angle end, ensuring the magnification sharing of the lens group GP and effectively correcting spherical aberration and coma aberration. If the upper limit of conditional equation (1) is exceeded and the refractive power of the negative lens AN becomes stronger than that of the lens group GP, it becomes difficult to ensure the magnification sharing, leading to an increase in the overall lens length at the telephoto end. If the lower limit of conditional equation (1) is exceeded and the refractive power of the negative lens AN becomes weak, the axially incident light beam to the cemented lens B becomes strongly converged light, making it difficult to suppress coma aberration in the wide-angle range.

[0036] Condition (2) specifies the ratio of the object-side radius of curvature to the image-side radius of curvature of the positive lens AP, optimizing the chromatic aberration correction effect while ensuring the refractive power of the positive lens AP. If the upper limit of condition (2) is exceeded and the object-side radius of curvature of the positive lens AP becomes small, it is advantageous for correcting spherical aberration, but it becomes difficult to suppress the wavelength-dependent variation of coma aberration. If the lower limit of condition (2) is exceeded and the object-side radius of curvature of the positive lens AP becomes large, the radius of curvature of the cemented surface becomes too small, leading to fluctuations in spherical aberration due to zooming.

[0037] Furthermore, it is preferable that the numerical ranges of conditional expressions (1) and (2) be within the ranges of the following conditional expressions (1a) and (2a).

[0038] -1.100 <fAN / fGP<-0.800 ···(1a) 0.100<|APR2 / APR1|<1.100 ···(2a) By satisfying condition (1a), axial chromatic aberration in the wide-angle range is suppressed while coma aberration is easily controlled. By satisfying condition (2a), spherical aberration in the telephoto range is suppressed while the overall length of the lens can be shortened, which is preferable.

[0039] Furthermore, it is even more preferable to set the numerical ranges of conditional expressions (1) and (2) to the ranges of the following conditional expressions (1b) and (2b).

[0040] -1.050 <fAN / fGP<-0.802 ···(1b) 0.150<|APR2 / APR1|<1.095 ···(2b) As described above, by appropriately configuring each lens group and simultaneously satisfying conditions (1) and (2), various aberrations such as chromatic aberration and spherical aberration can be well corrected, and a wide-angle, compact zoom lens can be realized that is robust against manufacturing errors.

[0041] Furthermore, the zoom lens in each embodiment can also adopt the following configuration as an alternative.

[0042] As an alternative, the zoom lens in each embodiment consists 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 RG including one or more lens groups, arranged sequentially from the object side to the image side. In other words, the zoom lens consists of four or more lens groups. The spacing between adjacent lens groups changes with zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves, the spacing between the first lens group L1 and the second lens group L2 widens, and the spacing between the second lens group L2 and the third lens group L3 narrows. If the third lens group L3, or a lens group arranged continuously on the image side relative to the third lens group L3, is a lens group with positive refractive power, the lens group consisting of the third lens group L3 and the lens group with positive refractive power is called lens group GP (positive group). In this case, the lens group GP includes a cemented lens A (first cemented lens) with negative refractive power and a cemented lens B (second cemented lens) with positive refractive power, arranged in order from the object side to the image side. The cemented lens A consists of a biconvex lens AP (first lens) with positive refractive power and a lens AN (second lens) with negative refractive power, arranged in order from the object side to the image side.

[0043] Furthermore, the zoom lens of each embodiment as an alternative means satisfies the following conditions (1) and (3).

[0044] -1.200 <fAN / fGP<-0.795 ···(1) 1.45 <ndAN<1.64 ···(3) Here, fGP is the focal length of the lens group GP at its wide-angle end, and fAN is the focal length of the negative lens AN. ndAN is the refractive index of the negative lens AN (optical element) at the d-line.

[0045] Furthermore, any parts of the above-mentioned zoom lens configuration and conditions that overlap with those previously mentioned will be omitted from the explanation.

[0046] Condition (3) specifies the refractive index of the negative lens AN at the d line. If the refractive index of the negative lens AN is high, spherical aberration is easier to correct, but the cementing surface becomes divergent, which is disadvantageous for correcting chromatic aberration. In particular, in the wide-angle range, optimizing the refractive index of the negative lens AN is important to achieve both chromatic aberration and spherical aberration correction with cemented lens A. If the refractive index is higher than the upper limit of condition (3), the radius of curvature at the cementing surface of cemented lens A becomes too large, making it difficult to achieve both first-order chromatic aberration correction and coma aberration correction. If the refractive index is lower than the lower limit of condition (3), it becomes difficult to suppress higher-order spherical aberration.

[0047] Furthermore, it is preferable that the numerical ranges of conditional expressions (1) and (3) be within the ranges of the following conditional expressions (1a) and (3a).

[0048] -1.100 <fAN / fGP<-0.800 ···(1a) 1.47 <ndAN<1.60 ···(3a) By satisfying condition (1a), axial chromatic aberration in the wide-angle range is suppressed while coma aberration is easily controlled. By satisfying condition (3a), spherical aberration and coma aberration are easily controlled throughout the entire zoom range, which is preferable.

[0049] Furthermore, it is even more preferable to set the numerical ranges of conditional expressions (1) and (3) to the ranges of the following conditional expressions (1b) and (3b).

[0050] -1.050 <fAN / fGP<-0.802 ···(1b) 1.51 <ndAN<1.58 ···(3b) As described above, by appropriately configuring each lens group and simultaneously satisfying conditions (1) and (3), various aberrations such as chromatic aberration and spherical aberration can be well corrected, and a wide-angle, compact zoom lens can be realized that is robust against manufacturing errors.

[0051] Next, we will describe the conditions that are preferably satisfied in the zoom lens of each embodiment. It is preferable that the zoom lens of each embodiment satisfies one or more of the following conditional equations (4) to (13).

[0052] -0.10 <SFA<1.20 ···(4) 0.7 < |APR2 / fGP| < 1.8 ···(5) 70.5 < νdAP < 100.0 ... (6) 0.60<νdAN / νdAP<0.85 (7) -2.00 <fA / fB<-0.50 ···(8) 4.2 < |f1 / f2| < 7.0 ... (9) 3.8 <f1 / fw<5.5 ···(10) 1.0 < |f3 / f2| < 2.8 ···(11) 0.16 <f3 / ft<0.50 ···(12) 56<νd3P<80 ···(13) Here, SFA is the shape factor of cemented lens A. νdAP is the Abbe number of positive lens AP. νdAN is the Abbe number of negative lens AN. fA is the focal length of cemented lens A. fB is the focal length of cemented lens B. f1, f2, and f3 are the focal lengths of the first lens group L1, the second lens group L2, and the third lens group L3, respectively. fw and ft are the focal lengths of the zoom lens at the wide-angle end and the telephoto end, respectively. νd3P is the average Abbe number of the positive lenses in the third lens group L3.

[0053] The Abbe number νd and the partial dispersion ratio θgF are defined by the following equations, where the refractive indices of the Fraunhofer lines d, F, C, and g are Nd, NF, NC, and Ng, respectively.

[0054] νd = (Nd-1) / (NF-NC) θgF = (Ng - NF) / (NF - NC) The shape factor SFA is defined by the following equation, where APR1 is the radius of curvature of the object-side lens surface of cemented lens A, and ANR2 is the radius of curvature of the image-side lens surface. If the lens surface is aspherical, it represents its base R (radius of the reference quadratic surface).

[0055] SFA = -(ANR2 + APR1) / (ANR2 - APR1) Conditional equation (4) is a conditional equation that defines the shape factor of cemented lens A, and is intended to achieve miniaturization while simultaneously correcting spherical aberration and axial chromatic aberration. When the value of conditional equation (4) is 1, cemented lens A has a plano-concave shape with the concave surface facing the image side. If the value exceeds the upper limit of conditional equation (4), it becomes difficult to adequately correct coma aberration at the wide-angle end, and the zoom variation of spherical aberration becomes large, which is undesirable. If the value falls below the lower limit of conditional equation (4), spherical aberration and axial chromatic aberration at the telephoto end become large, which is undesirable.

[0056] Conditional equation (5) is an equation that defines the radius of curvature of the bonding surface of the cemented lens A by the focal length of the lens group GP at the wide-angle end. In order to miniaturize zoom lenses, it is effective to increase the magnification contribution of the lens group GP, but it is necessary to balance this with achromatic aberration, and conditional equation (5) is intended to correct axial chromatic aberration and optimize the magnification contribution. If the upper limit of conditional equation (5) is exceeded, the radius of curvature of the bonding surface becomes too large for the magnification contribution, leading to insufficient correction of axial chromatic aberration at the telephoto end, which is undesirable. If the lower limit of conditional equation (5) is exceeded, the refractive power of the lens group GP becomes weak, and in order to maintain the predetermined magnification ratio, it leads to an increase in the amount of movement of the lens group GP from the wide-angle end to the telephoto end, which is undesirable as it leads to a larger zoom lens.

[0057] Conditional equation (6) specifies the Abbe number of the material for the positive lens AP, and is intended to suppress axial chromatic aberration and correct the insufficient correction of chromatic aberration in the first lens group L1 and the second lens group L2 with lens group GP. Exceeding the upper limit of conditional equation (6) is advantageous for correcting axial chromatic aberration, but it becomes difficult to secure the desired refractive power as a glass material. Exceeding the lower limit of conditional equation (6) is undesirable because it becomes difficult to correct the first-order aberration of axial chromatic aberration and lateral chromatic aberration.

[0058] Conditional equation (7) specifies the ratio of the Abbe number of the positive lens AP to the Abbe number of the negative lens AN in cemented lens A, and is intended to achieve both correction of axial chromatic aberration and correction of spherical and coma aberrations. If the upper limit of conditional equation (7) is exceeded, the Abbe numbers of the positive lens AP and the negative lens AN become closer, the achromatic effect due to the glass material properties weakens, and achromatic correction becomes necessary in lenses other than cemented lens A, leading to an increase in the number of lenses or an increase in the overall length of the lens, which is undesirable. If the lower limit of conditional equation (7) is exceeded, the achromatic effect due to the glass material properties is ensured, but the radius of curvature of the cemented surface becomes large, making it difficult to ensure the refractive power of the positive lens AP, and problems tend to arise in correcting chromatic aberration, which is undesirable.

[0059] Conditional equation (8) defines the ratio of the focal length fA of cemented lens A to the focal length fB of cemented lens B, and is intended to achieve both axial chromatic aberration correction and correction of spherical aberration and coma aberration. Furthermore, satisfying conditional equation (8) optimizes the aberration correction distribution between the two sets of cemented lenses A and B, making it easier to ensure robustness against polarization, which becomes a problem when increasing aperture or zoom ratio. Exceeding the upper limit of conditional equation (8) is undesirable because the refractive power of cemented lens A becomes too strong, the incident light beam to cemented lens B tends to become divergent light, and this tends to lead to an increase in coma aberration due to polarization of cemented lens B. Exceeding the lower limit of conditional equation (8) is undesirable because the refractive power of cemented lens A becomes too weak, which tends to result in insufficient correction of spherical aberration, especially at the telephoto end.

[0060] Conditional equation (9) is an equation that defines the focal length of the first lens group L1 as the focal length of the second lens group L2, and is intended to maintain an appropriate magnification ratio and miniaturize the zoom lens. In zoom lenses with a relatively bright telephoto end, if the refractive power of the first lens group L1 is not appropriately secured within the range where aberration correction is possible, the overall length of the zoom lens on the telephoto end will increase, and furthermore, the diameter of the front element will have to be enlarged in order to secure peripheral illumination. If the upper limit of conditional equation (9) is exceeded, the aberration fluctuations of the first lens group L1 and the second lens group L2 during zooming will become large, making it difficult to correct spherical aberration in particular, which is undesirable. If the lower limit of conditional equation (9) is exceeded, the refractive power of the first lens group L1 will become small, increasing the overall length of the zoom lens, and furthermore, it will become difficult to secure peripheral illumination, which is undesirable.

[0061] Conditional equation (10) defines the focal length of the first lens group L1 as the focal length of the zoom lens at the wide-angle end, and is intended to optimize the distribution of magnification while miniaturizing the lens. By setting a desired refractive power for the first lens group L1, the amount of movement of the first lens group L1 during zooming can be suppressed. If the upper limit of conditional equation (10) is exceeded, the refractive power of the first lens group L1 becomes weak, and the magnification effect weakens. If the amount of movement of the first lens group L1 is increased during zooming to compensate for the magnification effect, the overall length increases at the telephoto end, which is undesirable. Also, if the upper limit of conditional equation (10) is exceeded, the distribution of magnification must be ensured by the lens groups from the third lens group L3 onwards, in which case various aberrations such as spherical aberration and coma aberration will occur at the telephoto end. As a result, the number of lenses and aspherical lenses will increase to correct aberrations, which tends to lead to a loss of robustness against manufacturing errors, and is undesirable. If the value falls below the lower limit of condition (10), the refractive power of the first lens group L1 becomes too strong, and more spherical aberration occurs than in the first lens group L1 at the telephoto end, which is undesirable.

[0062] Conditional equation (11) is an equation that defines the focal length of the third lens group L3 as the focal length of the second lens group L2, and is intended to ensure a good balance between spherical aberration and coma aberration while maintaining a good balance between zoom and refraction. If the upper limit of conditional equation (11) is exceeded, the refractive power of the third lens group L3 becomes too weak, the zoom effect weakens, and it is undesirable because it leads to an increase in the amount of movement of the third lens group L3 during zooming. If the lower limit of conditional equation (11) is exceeded, the refractive power of the third lens group L3 becomes too strong, which is undesirable because it causes spherical aberration, coma aberration, and astigmatism in the center of the image at the telephoto end.

[0063] Conditional equation (12) defines the focal length of the third lens group L3 as the focal length of the zoom lens at the telephoto end, and is intended to achieve both correction of field curvature in the telephoto range and miniaturization of the zoom lens. If the upper limit of conditional equation (12) is exceeded, the refractive power of the third lens group L3 becomes too weak, making it easy for field curvature at the telephoto end to increase, which is undesirable. If the lower limit of conditional equation (12) is exceeded, the refractive power of the third lens group L3 becomes too strong, causing fluctuations in coma aberration with respect to image height at the telephoto end, which is also undesirable.

[0064] Conditional equation (13) is an equation that specifies the average Abbe number of the positive lenses included in the third lens group L3, and is intended to reduce the overall length of the lens and suppress axial chromatic aberration and lateral chromatic aberration. Exceeding the upper limit of conditional equation (13) is advantageous in suppressing axial chromatic aberration and lateral chromatic aberration, but it is undesirable because the radius of curvature of the lens approaches zero, leading to insufficient correction of spherical aberration and coma aberration. Exceeding the lower limit of conditional equation (13) is undesirable because chromatic aberration becomes large, making it difficult to correct aberrations for the zoom lens as a whole.

[0065] Furthermore, it is more preferable that the numerical ranges of conditional expressions (4) to (13) be within the ranges of the following conditional expressions (4a) to (13a).

[0066] -0.07 <SFA<1.00 ···(4a) 0.8 < |APR2 / fGP| < 1.7 ···(5a) 70.6 < νdAP < 96.0 ···(6a) 0.65<νdAN / νdAP<0.80 (7a) -1.70 <fA / fB<-0.54 ···(8a) 4.4 < |f1 / f2| < 6.0 ···(9a) 4.0 <f1 / fw<5.0 ···(10a) 1.1 < |f3 / f2| < 2.4 ···(11a) 0.18 <f3 / ft<0.45 ···(12a) 60 < νd3P < 77 ···(13a) By satisfying condition (4a), spherical aberration correction in the wide-angle range becomes more appropriate, making it easier to achieve a larger aperture. By satisfying condition (5a), correction of axial chromatic aberration and optimization of magnification distribution become easier. By satisfying condition (6a), axial chromatic aberration in the telephoto range becomes easier to correct. By satisfying condition (7a), fluctuations in axial chromatic aberration due to zooming become easier to suppress. By satisfying condition (8a), it becomes easier to optimize the aberration correction distribution of the two sets of cemented lenses. By satisfying condition (9a), the overall length of the lens becomes easier to shorten. By satisfying condition (10a), correction of chromatic aberration at the wide-angle end and spherical aberration at the telephoto end becomes easier to achieve simultaneously. By satisfying condition (11a), the magnification distribution of the third lens group L3 becomes more appropriate, making it easier to suppress zooming fluctuations in coma aberration. By satisfying condition (12a), it becomes easier to suppress variations in coma aberration with respect to the angle of view in the telephoto range. By satisfying condition (13a), it becomes easier to reduce the overall length of the lens.

[0067] Furthermore, it is even more preferable that the numerical ranges of conditional expressions (4) to (13) be within the ranges of the following conditional expressions (4b) to (13b).

[0068] -0.05 <SFA<0.70 ···(4b) 0.90<|APR2 / fGP|<1.65 (5b) 70.69 < νdAP < 83.00 ···(6b) 0.68<νdAN / νdAP<0.75 (7b) -1.60 <fA / fB<-0.57 ···(8b) 4.6 < |f1 / f2| < 5.4 ... (9b) 4.1 <f1 / fw<4.8 ···(10b) 1.2 < |f3 / f2| < 2.2 ···(11b) 0.20 <f3 / ft<0.40 ···(12b) 62<νd3P<74 ···(13b) Next, we will describe the preferred configurations for each embodiment of the zoom lens.

[0069] The first lens group L1 preferably consists of three or fewer lenses.

[0070] This configuration allows for a reduction in the number of elements in the first lens group L1, which has a large lens diameter, thus enabling miniaturization and weight reduction. Furthermore, it lowers the height of the light rays emitted from the first lens group L1, allowing for better correction of off-axis aberrations such as coma and field curvature.

[0071] The first lens group L1 preferably consists of a cemented lens of a negative lens and a positive lens, and a single meniscus-shaped lens with positive refractive power, arranged in order from the object side to the image side. This configuration makes it easy to effectively correct chromatic aberration across the entire zoom range, as well as spherical aberration and axial chromatic aberration at the telephoto end.

[0072] Furthermore, the second lens group L2 preferably consists of four spherical lenses arranged in order from the object side to the image side: a lens with negative refractive power, a lens with negative refractive power, a lens with positive refractive power, and a lens with negative refractive power. By configuring the second lens group L2 with spherical lenses, surface shape errors (so-called asymmetric or quirky component errors) that tend to occur with aspherical lenses can be suppressed.

[0073] This configuration enhances the refractive power of the second lens group L2 while simultaneously correcting chromatic aberration and field curvature in the wide-angle range and spherical aberration in the telephoto range. By positioning the negative lens closest to the object in the second lens group L2, the power distribution within the second lens group L2 can be made retrofocus type, resulting in excellent correction of field curvature and coma aberration in the wide-angle range.

[0074] The third lens group L3 preferably includes a single convex lens with positive refractive power that is positioned closest to the object. The light beam incident on the third lens group from the second lens group L2, which is the main magnification group, has a higher ray height, which causes higher-order spherical aberration and coma aberration. Therefore, in order to effectively suppress the occurrence of spherical aberration and coma aberration, a single convex lens with positive refractive power is positioned closest to the object in the third lens group L3, thereby focusing the light beam diverged by the second lens group L2.

[0075] Furthermore, in the lens group positioned closest to the image sensor, it is preferable that the lens positioned closest to the image sensor is a positive lens that is convex toward the image sensor. This configuration makes it relatively easy to secure back focus and suppresses the collection of unwanted light (ghosting) caused by the image sensor.

[0076] Furthermore, it is preferable that the rear group RG has at least one aspherical surface. This configuration allows for effective correction of field curvature at the wide-angle end while also enabling miniaturization of the zoom lens.

[0077] Furthermore, it is preferable that the image-side lens adjacent to the aperture diaphragm SP consists of a biconvex lens element (single lens or cemented lens) with a strongly convex shape toward the object. By positioning the lens surface with a strongly convex shape facing the aperture diaphragm SP, it becomes easier to suppress spherical aberration associated with large apertures and to correct off-axis aberrations in the wide-angle range. Moreover, by configuring the strongly convex lens element to have an aspherical surface, it becomes easier to correct both spherical aberration and coma aberration, as well as field curvature.

[0078] In the zoom lenses of each embodiment, vibration isolation can be achieved by moving any entire lens group or a part thereof as a vibration isolation group so as to include a component perpendicular to the optical axis, or by rotating (oscillating) it in an in-plane direction including the optical axis. In particular, it is preferable to use cemented lens B as the vibration isolation group. There are no particular restrictions on the number or shape of lenses in the vibration isolation group. Furthermore, it is preferable that the vibration isolation group has a positive refractive power. Furthermore, it is preferable that the vibration isolation group consists of a part of one lens group, and more preferably consists of the central part of one lens group divided into three parts.

[0079] In the zoom lenses of each embodiment, focusing can also be achieved by moving any entire lens group or a part thereof as a focusing group to include a component in the optical axis direction.

[0080] Next, we will describe the zoom lenses of each embodiment in detail.

[0081] In Example 1 of Figure 1, L1 is the first lens group with positive refractive power, L2 is the second lens group with negative refractive power, L3 is the third lens group with positive refractive power, L4 is the fourth lens group with positive refractive power, L5 is the fifth lens group with negative refractive power, L6 is the sixth lens group with negative refractive power, and L7 is the seventh lens group with positive refractive power. Lens group GP consists of the third lens group L3 and the fourth lens group L4. Joined lens A is a negative refractive power lens element formed by joining the ninth lens (counting from the object side) and the tenth lens (counting from the object side). Joined lens B is a positive refractive power lens element formed by joining the eleventh lens (counting from the object side) and the twelfth lens (counting from the object side).

[0082] In the zoom lens of Example 1, when zooming from the wide-angle end to the telephoto end, the first lens group L1 moves monotonically toward the object. At the telephoto end, the distance between the first lens group L1 and the second lens group L2 is wider than at the wide-angle end, the distance between the second lens group L2 and the third lens group L3 is narrower, and the distance between the third lens group L3 and the fourth lens group L4 is wider. The fifth lens group L5 moves when focusing is achieved.

[0083] In Examples 2, 3, and 4 shown in Figures 3, 5, and 7, L1 is the positive first lens group, L2 is the negative second lens group, L3 is the positive third lens group, L4 is the negative fourth lens group, L5 is the negative fifth lens group, and L6 is the positive sixth lens group. Lens group GP is the third lens group L3.

[0084] In Examples 2 and 4, cemented lens A is a negative refractive power lens element formed by joining the 9th lens and the 10th lens. Cemented lens B is a positive refractive power lens element formed by joining the 11th lens and the 12th lens. In Example 3, cemented lens A is a negative refractive power lens element formed by joining the 10th lens and the 11th lens, and cemented lens B is a positive refractive power lens element formed by joining the 12th lens and the 13th lens.

[0085] In the zoom lenses of Examples 2, 3, and 4, the first lens group L1 moves monotonically toward the object when zooming from the wide-angle end to the telephoto end. The lens groups move such that the distance between the first lens group L1 and the second lens group L2 is wider at the telephoto end compared to the wide-angle end, and the distance between the second lens group L2 and the third lens group L3 is narrower. The fourth lens group L4 moves when focusing.

[0086] In Example 5 of Figure 9, L1 is the positive first lens group, L2 is the negative second lens group, L3 is the positive third lens group, L4 is the negative fourth lens group, and L5 is the positive fifth lens group. Lens group GP is the third lens group L3. Bonded lens A is a negative refractive power lens element formed by bonding the ninth lens and the tenth lens. Bonded lens B is a positive refractive power lens element formed by bonding the eleventh lens and the twelfth lens.

[0087] In the zoom lens of Example 5, when zooming from the wide-angle end to the telephoto end, the first lens group L1 moves monotonically toward the object. The lens groups move such that the distance between the first lens group L1 and the second lens group L2 is wider at the telephoto end compared to the wide-angle end, and the distance between the second lens group L2 and the third lens group L3 is narrower. When focusing, the fourth lens group L4 moves.

[0088] In Embodiment 6 of Figure 11, L1 is the positive first lens group, L2 is the negative second lens group, L3 is the positive third lens group, L4 is the positive fourth lens group, L5 is the negative fifth lens group, and L6 is the positive sixth lens group. Lens group GP consists of the third lens group L3 and the fourth lens group L4. Bonded lens A is a negative refractive power lens element formed by bonding the ninth lens and the tenth lens. Bonded lens B is a positive refractive power lens element formed by bonding the eleventh lens and the twelfth lens.

[0089] In the zoom lens of Example 6, the first lens group L1 moves monotonically toward the object when zooming from the wide-angle end to the telephoto end. At the telephoto end, the distance between the first lens group L1 and the second lens group L2 is wider than at the wide-angle end, the distance between the second lens group L2 and the third lens group L3 is narrower, and the distance between the third lens group L3 and the fourth lens group L4 is narrower. When focusing, the fifth lens group L4 moves.

[0090] The numerical values ​​corresponding to Examples 1 to 6 are shown below.

[0091] In the surface data for each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (distance along the optical axis) between the m-th surface and the (m+1)-th surface. Here, m is the surface number counted from the light incidence side. Furthermore, 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 and partial dispersion ratio θgF of a certain material are given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (435.8 nm) are Nd, NF, and NC. νd = (Nd-1) / (NF-NC) θgF = (Ng - NF) / (NF - NC) It is represented as follows.

[0092] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values when the zoom lens of each example is focused on an infinitely distant object. "Back focus BF" 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 length of the lens" is the length obtained by adding the back focus to the distance on the optical axis from the frontmost surface (the lens surface closest to the object side) to the final surface of the zoom lens. "Lens group" shall include cases where it is composed of a single lens as well as cases where it is composed of multiple lenses.

[0093] 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 curvature radius, k is the conic constant, and A4, A6, A8, A10, and A12 are the aspherical coefficients of each order: x=(h / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 +A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 Here, "e±XX" in each aspherical coefficient means "×10± XX ".

[0094] [Numerical Example 1] Unit: mm Surface Data Surface Number r d nd νd θgF 1 123.206 1.50 1.92286 20.88 0.6391 2 66.828 5.58 1.61800 63.40 0.5395 3 -464.077 0.25 4 43.861 4.97 1.69680 55.53 0.5434 5 151.415 (variable) 6 111.979 0.90 1.95375 32.32 0.5898 7 12.847 5.64 8 -27.915 0.80 1.87070 40.73 0.5686 9 48.809 0.20 10 28.449 4.57 1.92119 23.96 0.6203 11 -26.495 0.59 12 -19.303 0.80 1.72916 54.68 0.5444 13 -68.905 (variable) 14 (aperture) ∞ 0.60 15* 15.738 4.27 1.55332 71.69 0.5402 16* -45.933 0.25 17 52.284 4.08 1.49700 81.54 0.5375 18 -15.890 0.80 1.51823 58.90 0.5457 19 13.720 2.31 20 27.621 0.80 1.83400 37.21 0.5807 21 15.339 3.16 1.59282 68.62 0.5458 22 -315.513 (variable) 23 23.005 4.57 1.61800 63.40 0.5395 24 -13.556 0.80 1.91650 31.60 0.5911 25 -24.224 (variable) 26 67.433 0.80 1.74100 52.64 0.5467 27 13.200 (Variable) 28* -219.833 1.80 1.58313 59.38 0.5423 29 * 193.213 (variable) 30 -79.761 3.77 1.62041 60.29 0.5427 31 -25.977 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-2.68014e-005 A 6=-1.51087e-007 A 8= 1.84722e-009 A10 = -2.71938e-011 Page 16 K = 0.00000e+000 A 4= 2.76611e-005 A 6=-1.59524e-007 A 8= 2.00775e-009 A10 = -2.74372e-011 Page 28 K = 0.00000e+000 A 4=-2.04383e-004 A 6=-1.04758e-006 A 8= 4.38595e-008 A10=-6.31993e-010 A12= 3.09385e-012 Page 29 K = 0.00000e+000 A 4=-1.81227e-004 A 6=-3.38180e-007 A 8= 2.34179e-008 A10=-3.02899e-010 A12= 1.25523e-012 Various data Zoom ratio 4.40 Wide-angle, Medium, Telephoto Focal length 15.45 36.03 67.94 F-number 4.12 4.12 4.12 Half-angle (°): 41.27, 19.59, 10.60 Image height 12.66 13.66 13.66 Lens length: 100.14, 108.00, 120.23 BF 10.46 10.79 12.37 d 5 0.70 12.96 25.75 d13 22.92 8.59 3.29 d22 0.80 1.27 1.35 d25 1.56 3.50 3.36 d27 8.85 6.45 6.51 d29 1.05 10.66 13.82 d31 10.46 10.79 12.37 Zoom lens group data Group starting plane focal length 1 1 64.00 2 6 -13.48 3 14 26.77 4 23 24.17 5 26 -22.29 6 28 -176.06 7 30 60.47 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd θgF 1 101.257 1.50 1.92286 20.88 0.6391 2 60.291 5.73 1.59282 68.62 0.5458 3 -4456.172 0.25 4 42.966 4.60 1.69680 55.53 0.5434 5 158.953 (variable) 6 99.609 0.90 1.95375 32.32 0.5898 7 13.291 5.85 8 -32.886 0.80 1.87070 40.73 0.5686 9 38.107 0.20 10 27.182 4.69 1.92119 23.96 0.6203 11 -34.023 1.04 12 -19.649 0.80 1.55200 70.70 0.5421 13 -92.753 (variable) 14 (aperture) ∞ 0.60 15* 16.457 4.63 1.58313 59.38 0.5423 16* -68.118 0.25 17 48.885 3.47 1.53775 74.70 0.5392 18 -19.399 0.80 1.51742 52.43 0.5564 19 15.364 2.05 20 29.727 0.80 1.83481 42.74 0.5648 21 16.042 2.96 1.59282 68.62 0.5458 22 -364.901 0.84 23 29.252 5.18 1.72916 54.68 0.5444 24 -11.979 0.80 1.91650 31.60 0.5911 25 -25.127 (variable) 26 975.106 0.80 1.85150 40.78 0.5695 27 15.191 (Variable) 28* 197.091 1.90 1.53110 55.91 0.5684 29 * 60.563 (variable) 30 4252.772 5.11 1.59410 60.47 0.5550 31 -26.104 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-2.53346e-006 A 6= 1.78537e-007 A 8=-8.04903e-010 A10 = 6.70995e-011 Page 16 K = 0.00000e+000 A 4= 5.48471e-005 A 6= 2.41490e-007 A 8=-1.10585e-009 A10 = 9.23529e-011 Page 28 K = 0.00000e+000 A 4=-2.17094e-004 A 6=-1.28876e-006 A 8= 4.43371e-008 A10=-6.71659e-010 A12= 3.68763e-012 Page 29 K = 0.00000e+000 A 4=-1.88532e-004 A 6=-4.86363e-007 A 8= 2.32061e-008 A10=-2.91056e-010 A12= 1.30530e-012 Various data Zoom ratio 4.40 Wide-angle, Medium, Telephoto Focal length 15.45 36.49 68.04 F-numbers: 2.88, 3.86, 4.12 Half-angle (°): 41.38, 19.53, 10.61 Image height 12.66 13.66 13.66 Lens length: 100.32, 110.44, 118.71 BF 10.62 11.68 15.59 d 5 0.70 14.07 25.79 d13 22.06 8.62 1.17 d25 1.69 3.05 3.66 d27 7.78 6.42 5.81 d29 0.91 10.04 10.13 d31 10.62 11.68 15.59 Zoom lens group data Group starting plane focal length 1 1 64.00 2 6 -13.50 3 14 16.59 4 26 -18.13 5 28 -165.42 6 30 43.69 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd θgF 1 97.661 1.50 1.92286 20.88 0.6391 2 58.555 5.87 1.59282 68.62 0.5458 3 -1996.145 0.25 4 44.217 4.84 1.69680 55.53 0.5434 5 169.020 (variable) 6 130.464 0.90 1.95375 32.32 0.5898 7 13.417 5.61 8 -33.393 0.80 1.87070 40.73 0.5686 9 33.979 0.20 10 25.723 4.84 1.92119 23.96 0.6203 11 -33.108 1.05 12 -19.402 0.80 1.55200 70.70 0.5421 13 -71.066 (variable) 14 (aperture) ∞ 0.60 15 15.204 0.70 1.65160 58.55 0.5425 16 9.870 4.90 1.51633 64.06 0.5333 17* -95.198 0.25 18 22.963 3.84 1.55200 70.70 0.5421 19 -24.345 0.80 1.57099 50.80 0.5588 20 15.024 1.55 21 27.122 0.80 1.85150 40.78 0.5695 22 15.005 3.00 1.59282 68.62 0.5458 23 -233.617 0.58 24 28.481 4.97 1.72916 54.68 0.5444 25 -12.138 0.80 1.83400 37.34 0.5790 26 -30.268 (variable) 27 272.727 0.80 1.85150 40.78 0.5695 28 14.980 (Variable) 29* -304.916 1.90 1.53110 55.91 0.5684 30 * 166.458 (variable) 31 -209.281 3.84 1.59410 60.47 0.5550 32 -28.556 (variable) Image plane ∞ Aspherical data Page 17 K = 0.00000e+000 A 4= 3.94800e-005 A 6=-2.50399e-008 A 8=-1.60986e-010 A10 = -6.81649e-012 Page 29 K = 0.00000e+000 A 4=-2.34513e-004 A 6=-7.30053e-007 A 8= 3.42430e-008 A10=-6.55075e-010 A12= 4.36794e-012 Page 30 K = 0.00000e+000 A 4=-1.90964e-004 A 6=-2.32987e-007 A 8= 1.99577e-008 A10=-3.06930e-010 A12= 1.65135e-012 Various data Zoom ratio 4.40 Wide-angle, Medium, Telephoto Focal length 15.45 36.47 68.05 F-numbers: 2.88, 3.81, 4.12 Half-angle (°): 41.28, 19.17, 10.42 Image height 12.66 13.66 13.66 Lens length: 100.14, 109.96, 118.75 BF 11.46 9.98 13.02 d 5 0.70 14.51 25.88 d13 22.49 9.61 2.72 d26 1.67 2.83 3.01 d28 6.99 5.82 5.65 d30 0.84 11.22 12.49 d32 11.46 9.98 13.02 Zoom lens group data Group starting plane focal length 1 1 63.50 2 6 -13.80 3 14 16.60 4 27 -18.64 5 29 -202.46 6 31 55.22 [Numerical Example 4] Unit: mm Surface data Face number rd nd νd θgF 1 87.053 1.80 1.92119 23.96 0.6203 2 55.246 6.60 1.52841 76.46 0.5396 3 4555.935 0.25 4 51.113 4.99 1.69680 55.53 0.5434 5 211.575 (variable) 6 88.373 0.90 1.95375 32.32 0.5898 7 13.186 5.83 8 -37.162 0.80 1.87070 40.73 0.5686 9 35.339 0.20 10 24.993 4.60 1.92119 23.96 0.6203 11 -39.335 1.20 12 -19.465 0.80 1.49700 81.54 0.5375 13 -141.682 (variable) 14 (aperture) ∞ 0.60 15* 16.997 4.59 1.58313 59.38 0.5423 16* -53.106 0.25 17 92.533 3.52 1.55200 70.70 0.5421 18 -16.940 0.80 1.51742 52.43 0.5564 19 15.864 2.13 20 26.027 0.80 1.83400 37.21 0.5807 21 14.231 3.39 1.59282 68.62 0.5458 22 -180.390 0.91 23 39.643 4.31 1.75500 52.32 0.5474 24 -14.321 0.80 1.91650 31.60 0.5911 25 -27.389 (variable) 26 124.907 0.80 1.85150 40.78 0.5695 27 16.724 (Variable) 28* -310.168 1.90 1.53110 55.91 0.5684 29 * 60.508 (variable) 30 191.151 4.62 1.61800 63.40 0.5395 31 -33.418 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-1.60043e-005 A 6= 2.57695e-007 A 8=-4.70731e-009 A10 = 6.82356e-011 Page 16 K = 0.00000e+000 A 4= 4.50517e-005 A 6= 3.46001e-007 A 8=-6.66873e-009 A10 = 9.29389e-011 Page 28 K = 0.00000e+000 A 4=-2.30614e-004 A 6= 2.60574e-008 A 8= 2.37314e-008 A10=-3.80826e-010 A12= 2.01550e-012 Page 29 K = 0.00000e+000 A 4=-2.06759e-004 A 6= 7.95814e-007 A 8= 5.13152e-009 A10=-1.10127e-010 A12= 5.43574e-013 Various data Zoom ratio 5.42 Wide-angle, Medium, Telephoto Focal length 15.45 36.29 83.77 F-number 2.88 4.00 5.80 Half-angle (°): 41.36, 19.65, 8.71 Image height 12.66 13.66 13.66 Lens length: 101.54 x 116.35 x 133.85 BF 12.12 12.61 16.91 d 5 0.70 15.37 34.25 d13 20.64 8.48 0.93 d25 1.48 2.89 2.93 d27 8.36 6.94 6.91 d29 0.86 12.68 14.53 d31 12.12 12.61 16.91 Zoom lens group data Group starting plane focal length 1 1 73.20 2 6 -13.60 3 14 16.95 4 26 -22.75 5 28 -95.16 6 30 46.39 [Numerical Example 5] Unit: mm Surface data Face number rd nd νd θgF 1 86.086 1.80 1.92119 23.96 0.6203 2 52.542 6.59 1.52841 76.46 0.5396 3 1004.135 0.25 4 47.766 5.32 1.69680 55.53 0.5434 5 205.752 (variable) 6 63.302 0.90 1.95375 32.32 0.5898 7 12.905 6.22 8 -36.053 0.80 1.87070 40.73 0.5686 9 38.451 0.20 10 28.453 4.43 1.92119 23.96 0.6203 11 -35.825 1.22 12 -18.744 0.80 1.49700 81.54 0.5375 13 -180.756 (variable) 14 (aperture) ∞ 0.60 15* 18.234 4.11 1.58313 59.38 0.5423 16* -71.410 0.25 17 26.853 4.09 1.52841 76.46 0.5396 18 -26.171 0.80 1.51742 52.43 0.5564 19 14.660 2.37 20 23.248 0.80 1.83400 37.21 0.5807 21 13.128 3.58 1.59282 68.62 0.5458 22 4631.643 0.98 23 177.568 3.93 1.75500 52.32 0.5474 24 -13.676 0.80 1.91650 31.60 0.5911 25 -27.550 (variable) 26 -37.269 0.80 1.85150 40.78 0.5695 27 43.931 (Variable) 28* -283.811 1.90 1.69350 53.18 0.5482 29* 103.220 0.30 30 42.041 5.62 1.51633 64.14 0.5353 31 -37.748 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-1.41740e-005 A 6= 3.99398e-011 A 8=-4.41008e-011 A10 = 7.66400e-012 Page 16 K = 0.00000e+000 A 4= 1.83828e-005 A 6= 5.05825e-008 A 8=-3.04607e-010 A10 = 8.35527e-012 Page 28 K = 0.00000e+000 A 4=-2.29240e-004 A 6= 3.80091e-007 A 8= 1.87469e-008 A10=-2.85983e-010 A12= 1.26659e-012 Page 29 K = 0.00000e+000 A 4=-1.99561e-004 A 6= 9.53036e-007 A 8= 3.72688e-009 A10=-8.61757e-011 A12= 3.56878e-013 Various data Zoom ratio 5.09 Wide-angle, Medium, Telephoto Focal length 16.45 36.35 83.81 F-number 2.88 4.00 5.80 Half-angle (°): 39.72, 20.12, 8.62 Image height 12.66 13.66 13.66 Lens length: 104.42, 114.62, 126.76 BF 11.42 21.32 15.06 d 5 0.70 14.73 33.41 d13 22.19 8.47 0.86 d25 3.37 5.16 7.88 d27 7.29 5.49 10.10 d31 11.42 21.32 15.06 Zoom lens group data Group starting plane focal length 1 1 72.00 2 6 -13.42 3 14 18.72 4 26 -23.57 5 28 59.66 [Numerical Example 6] Unit: mm Surface data Face number rd nd νd θgF 1 85.769 1.80 1.92119 23.96 0.6203 2 52.890 6.70 1.52841 76.46 0.5396 3 4501.929 0.25 4 49.755 5.07 1.69680 55.53 0.5434 5 219.491 (variable) 6 68.665 0.90 1.95375 32.32 0.5898 7 13.105 6.06 8 -34.525 0.80 1.87070 40.73 0.5686 9 35.789 0.20 10 27.935 4.52 1.92119 23.96 0.6203 11 -35.000 1.26 12 -18.276 0.80 1.49700 81.54 0.5375 13 -108.531 (variable) 14 (aperture) ∞ 0.60 15* 18.233 4.11 1.58313 59.38 0.5423 16* -74.739 0.25 17 28.571 3.68 1.55032 75.50 0.5405 18 -31.238 0.80 1.51742 52.43 0.5564 19 14.821 2.01 20 23.757 0.80 1.83400 37.21 0.5807 21 13.197 3.58 1.59282 68.62 0.5458 22 -294.751 (variable) 23 -12460.363 3.68 1.75500 52.32 0.5474 24 -13.773 0.80 1.91650 31.60 0.5911 25 -27.092 (variable) 26 -44.781 0.80 1.85150 40.78 0.5695 27 42.378 (Variable) 28* -226.791 1.60 1.69350 53.18 0.5482 29* 108.870 0.30 30 41.390 5.47 1.51633 64.14 0.5353 31 -39.101 (variable) Image plane ∞ Aspherical data Page 15 K = 0.00000e+000 A 4=-1.46301e-005 A 6=-8.71553e-009 A 8= 1.00002e-010 A10 = 3.85899e-012 Page 16 K = 0.00000e+000 A 4= 1.92197e-005 A 6= 4.43348e-008 A 8=-3.28205e-010 A10 = 5.72268e-012 Page 28 K = 0.00000e+000 A 4=-2.54596e-004 A 6= 4.00949e-007 A 8= 2.01627e-008 A10=-2.77109e-010 A12= 1.16550e-012 Page 29 K = 0.00000e+000 A 4=-2.28119e-004 A 6= 1.12921e-006 A 8= 3.59935e-009 A10=-8.29769e-011 A12= 3.36865e-013 Various data Zoom ratio 5.09 Wide-angle, Medium, Telephoto Focal length 16.48 36.15 83.82 F-number 2.88 4.00 5.80 Half-angle (°): 39.58, 20.07, 8.56 Image height 12.66 13.66 13.66 Lens length: 104.85, 114.65, 126.77 BF 11.80 21.57 15.84 d 5 0.70 14.45 33.20 d13 22.40 8.58 0.89 d22 1.63 1.91 0.78 d25 3.37 5.38 8.39 d27 8.08 5.92 10.81 d31 11.80 21.57 15.84 Zoom lens group data Group starting plane focal length 1 1 71.50 2 6 -13.42 3 14 22.47 4 23 45.02 5 26 -25.46 6 28 61.60 The various values ​​in each numerical example are summarized in Table 1 below.

[0095] [Table 1]

[0096] [Imaging device] Next, an embodiment of a digital still camera (imaging device) 10 using the zoom lens of the present invention as an imaging optical system will be described with reference to FIG. 13. In FIG. 13, 13 is a camera body, and 11 is an imaging optical system composed of any one of the zoom lenses described in Examples 1 to 6. 12 is a solid-state imaging device (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body and receives the optical image formed by the imaging optical system 11 and performs photoelectric conversion. The camera body 13 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.

[0097] 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.

[0098] As described above, the preferred embodiments and examples of the present invention have been described. However, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist thereof.

Explanation of Reference Numerals

[0099] L1 First lens group L2 Second lens group L3 Third lens group RG Rear group A First joining lens B Second joining lens AP First lens AN Second lens

Claims

1. A zoom lens consisting of 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 rear group containing two or more lens groups, arranged in order from the object side to the image side, wherein the spacing between adjacent lens groups changes during zooming. When zooming from the wide-angle end to the telephoto end, the first lens group moves, the distance between the first lens group and the second lens group widens, and the distance between the second lens group and the third lens group narrows. If the third lens group, or the lens group arranged continuously on the image side relative to the third lens group, is a lens group with positive refractive power, then the lens group composed of the third lens group and the lens group with positive refractive power is considered a positive group. The positive group includes a first cemented lens with negative refractive power and a second cemented lens with positive refractive power, which is positioned adjacent to the image side of the first cemented lens. The first cemented lens consists of a first lens with positive refractive power and a biconvex shape, arranged in order from the object side to the image side, and a second lens with negative refractive power. When the focal length at the wide-angle end of the positive group is fGP, the focal length of the second lens is fAN, and the refractive index of the second lens at the d-line is ndAN, -1.200<fAN / fGP<-0.795 1.45<ndAN<1.64 A zoom lens characterized by satisfying the following conditional equation.

2. When the radius of curvature of the image side of the first cemented lens is APR2, 0.7<|APR2 / fGP|<1.8 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

3. When the Abbe number of the first lens in the first cemented lens is νdAP, 70.5<νdAP<100.0 A zoom lens according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. When the Abbe number of the first lens in the first cemented lens is νdAP and the Abbe number of the second lens in the first cemented lens is νdAN, 0.60<νdAN / νdAP<0.85 A zoom lens according to any one of claims 1 to 3, characterized in that it satisfies the following conditional expression.

5. When the focal length of the first cemented lens is fA and the focal length of the second cemented lens is fB, -2.00<fA / fB<-0.50 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 first lens group is f1 and the focal length of the second lens group is f2, 4.2<|f1 / f2|<7.0 A zoom lens according to any one of claims 1 to 5, characterized in that it satisfies the following conditional expression.

7. When the focal length of the first lens group is f1 and the focal length of the zoom lens at the wide-angle end is fw, 3.8<f1 / fw<5.5 A zoom lens according to any one of claims 1 to 6, characterized in that it satisfies the following conditional expression.

8. When the focal length of the second lens group is f2 and the focal length of the third lens group is f3, 1.0<|f3 / f2|<2.8 A zoom lens according to any one of claims 1 to 7, characterized in that it satisfies the following conditional expression.

9. When the focal length of the third lens group is f3 and the focal length of the zoom lens at the telephoto end is ft, 0.16<f3 / ft<0.50 A zoom lens according to any one of claims 1 to 8, characterized in that it satisfies the following conditional expression.

10. When the average Abbe number of the positive lenses in the third lens group is νd3P, 56 < νd3P < 80 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 first lens group consists of three or fewer lenses.

12. The zoom lens according to any one of claims 1 to 11, characterized in that the first lens group consists of a cemented lens of a negative lens and a positive lens, and a single lens with a meniscus shape and positive refractive power, arranged in order from the object side to the image side.

13. The zoom lens according to any one of claims 1 to 12, characterized in that the second lens group consists of four spherical lenses, arranged in order from the object side to the image side, consisting of a negative lens, a negative lens, a positive lens, and a negative lens.

14. The zoom lens according to any one of claims 1 to 13, characterized in that the third lens group includes a single lens that is positioned closest to the object and has a positive refractive power, and is convex towards the object.

15. The zoom lens according to any one of claims 1 to 14, characterized in that the lens positioned furthest towards the image side among the lens group positioned furthest towards the image side is a positive lens that is convex toward the image side.

16. The zoom lens according to any one of claims 1 to 15, characterized in that the rear group has an aspherical surface.

17. The zoom lens according to any one of claims 1 to 16, characterized in that the image-side lens adjacent to the aperture diaphragm is a biconvex lens element.

18. The zoom lens according to any one of claims 1 to 17, characterized in that the rear group includes a fourth lens group and a fifth lens group having positive refractive power, arranged in order from the object side to the image side.

19. The zoom lens according to any one of claims 1 to 18, characterized in that the rear group includes a fourth lens group and a fifth lens group having negative refractive power, arranged in order from the object side to the image side.

20. An imaging device characterized by having a zoom lens according to any one of claims 1 to 19 and an image sensor that receives an image formed by the zoom lens.

Images