Zoom lens and image pickup apparatus having the same

Abstract

To provide a compact zoom lens having a wide angle of view and capable of obtaining high optical performance while being robust against manufacturing errors.SOLUTION: The zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a rear lens group including two or more lens units, and an interval between adjacent lens units changes during zooming. During zooming, the first lens unit moves. In a case where the third lens group or the lens group disposed successively on the image side with respect to the third lens group is a lens group having a positive refractive power, a lens group consisting of the third lens group and the lens group having a positive refractive power is defined as a positive group, the positive group includes a first cemented lens having a negative refractive power and a second cemented lens having a positive refractive power disposed on the image side of the first cemented lens, and the first cemented lens consists of a first lens having a positive refractive power and a second lens having a negative refractive power. The positive group satisfies a predetermined conditional expression.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, for zoom lenses used in photo cameras, video cameras, etc., inner focus and rear focus methods have been proposed, in which focusing is performed by moving the lens group behind (on the image side) the first lens group on the object side.

[0003] Furthermore, solid-state imaging devices such as CCD and CMOS sensors in digital cameras and video cameras are becoming increasingly high-resolution. Also, photographic lenses are being required to have high optical performance, including chromatic aberration, while also becoming increasingly compact.

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

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

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-102525 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-018124 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, there has been a strong demand for lens systems used in image capture devices that have high optical performance while being compact as a whole. 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, the movement conditions of each lens group associated with zooming, etc. In particular, when miniaturizing a lens system for a camera with a large image sensor, high-refractive-index glass materials are often used extensively, and it is necessary to suppress chromatic aberration while ensuring robustness against lens decentration.

[0008] As 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] When a high zoom ratio and a telephoto focal length are secured as in Patent Document 2, it becomes difficult to suppress various aberrations at the wide-angle side, particularly suppress lateral chromatic aberration, making it difficult to achieve a wide angle of view.

[0010] An object of the present invention is to provide a wide-angle, compact zoom lens that is robust against manufacturing errors and provides high optical performance. [Means for solving the problem]

[0011] A zoom lens according to one aspect of the present invention comprises, in order from the object side to the image side, 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 rear group including two or more lens groups, and the distance 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 increases, the distance between the second lens group and the third lens group decreases, and an image is formed on the third lens group or the third lens group. When the lens group disposed adjacent to the third lens group on the image side is a lens group with positive refractive power, and 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 disposed on the image side of the first cemented lens, and the first cemented lens is made up of a first lens with positive refractive power and a second lens with negative refractive power, and when the focal length of the positive group at the 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 The present invention is characterized in that the following conditional expression is satisfied:

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

[0013] According to the present invention, it is possible to realize a wide-angle, compact zoom lens that is robust against manufacturing errors and provides high optical performance. [Brief explanation of the drawings]

[0014] [Figure 1] 1A to 1C are cross-sectional views of a zoom lens according to a first embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 2] 1A and 1B are aberration diagrams of the zoom lens of Example 1 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 3]10A to 10C are cross-sectional views of a zoom lens according to a second embodiment at a wide-angle end, a middle zoom position, and a telephoto end. [Figure 4] 10A and 10B are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 5] 10A to 10C are cross-sectional views of a zoom lens according to a third embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 6] 10A and 10B are aberration diagrams of the zoom lens of Example 3 at the wide-angle end (A), at the intermediate zoom position (B), and at the telephoto end (C). [Figure 7] 10A to 10C are cross-sectional views of a zoom lens according to a fourth embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 8] 10A and 10B are aberration diagrams of the zoom lens of Example 4 at the wide-angle end (A), at the intermediate zoom position (B), and at the telephoto end (C). [Figure 9] 10A to 10C are cross-sectional views of a zoom lens according to a fifth embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 10] 10A and 10B are aberration diagrams of the zoom lens of Example 5 at the wide-angle end (A), at the intermediate zoom position (B), and at the telephoto end (C). [Figure 11] 13A to 13C are cross-sectional views of a zoom lens according to a sixth embodiment at the wide-angle end, at a middle zoom position, and at the telephoto end. [Figure 12] 10A and 10B are aberration diagrams of the zoom lens of Example 6 at the wide-angle end (A), at the intermediate zoom position (B), and at the telephoto end (C). [Figure 13] FIG. 1 is a schematic diagram of an imaging device. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a zoom lens and an image pickup apparatus having the same according to the present invention will be described with reference to the accompanying drawings.

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

[0017] Fig. 3 is a cross-sectional view of the zoom lens of Example 2 at the wide-angle end, at a middle zoom position, and at the telephoto end. Fig. 4(A), Fig. 4(B), and Fig. 4(C) are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, at a middle zoom position, and at the 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] Fig. 5 is a cross-sectional view of the zoom lens of Example 3 at the wide-angle end, at a middle zoom position, and at the telephoto end. Fig. 6(A), Fig. 6(B), and Fig. 6(C) are aberration diagrams of the zoom lens of Example 3 at the wide-angle end, at a middle zoom position, and at the 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] Fig. 7 is a cross-sectional view of the zoom lens of Example 4 at the wide-angle end, at a middle zoom position, and at the telephoto end. Fig. 8(A), Fig. 8(B), and Fig. 8(C) are aberration diagrams of the zoom lens of Example 4 at the wide-angle end, at a middle zoom position, and at the 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] Fig. 9 is a cross-sectional view of the zoom lens of Example 5 at the wide-angle end, at a middle zoom position, and at the telephoto end. Fig. 10(A), Fig. 10(B), and Fig. 10(C) are aberration diagrams of the zoom lens of Example 5 at the wide-angle end, at a middle zoom position, and at the 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] Fig. 11 is a cross-sectional view of the zoom lens of Example 6 at the wide-angle end, at a middle zoom position, and at the telephoto end. Fig. 12(A), Fig. 12(B), and Fig. 12(C) are aberration diagrams of the zoom lens of Example 6 at the wide-angle end, at a middle zoom position, and at the 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 lens of each embodiment is an imaging optical system used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, etc. The zoom lens of each embodiment can also be used as a projection optical system for a projection device (projector).

[0023] In each lens cross-sectional view, the left side is the object side (front) and the right side is the image side (rear). The zoom lens of each embodiment is configured with multiple lens groups. In this specification, a lens group refers to a group of lenses that move or remain stationary as a unit during zooming. That is, in the zoom lens of each embodiment, the spacing between adjacent lens groups changes during zooming from the wide-angle end to the telephoto end. Note that a lens group may be composed of a single lens or multiple lenses. The lens group may also include an aperture stop.

[0024] In each lens cross-sectional view, if i is the order of the lens groups from the object side, Li indicates the ith lens group. SP is an aperture stop that determines (limits) the light beam at the maximum F-number (Fno). IP is an 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 imaging device (photoelectric conversion device) such as a CCD sensor or CMOS sensor is disposed thereon. When the zoom lens of each embodiment is used as the imaging optical system of a silver halide film camera, a photosensitive surface equivalent to the film surface is disposed at the image plane IP. The focusing arrow indicates the direction of movement of the lens groups when focusing from infinity to close distances.

[0025] In the spherical aberration diagrams, Fno is the F-number and shows the amount of spherical aberration for the d-line (wavelength 587.56 nm) and g-line (wavelength 435.835 nm). In the astigmatism diagrams, 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 diagrams, the amount of distortion for the d-line is shown. In the chromatic aberration diagrams, the amount of chromatic aberration for the g-line is shown. ω is the imaging half angle of view (°), which is the angle of view determined by ray tracing. In the following examples, the wide-angle end and telephoto end refer to zoom positions when the variable magnification lens group is located at both ends of the range of mechanical movement along the optical axis.

[0026] Next, the characteristic configuration of the zoom lens of each embodiment will be described.

[0027] The zoom lens of each embodiment comprises, arranged in order from the object side to the image side, a first lens group L1 with positive refractive power (optical power = the reciprocal of the 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. In other words, a zoom lens comprises four or more lens groups. The spacing between adjacent lens groups changes during zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves, widening the spacing between the first lens group L1 and the second lens group L2 and narrowing the spacing between the second lens group L2 and the third lens group L3. If the third lens group L3 or the lens group adjacent to the third lens group L3 on the image side has positive refractive power, the lens group consisting of the third lens group L3 and this lens group with positive refractive power is referred to as the lens group GP (positive group). In this case, the lens group GP includes, arranged in order from the object side to the image side, a cemented lens A (first cemented lens) with negative refractive power and a cemented lens B (second cemented lens) with positive refractive power. The cemented lens A includes, arranged in order from the object side to the image side, a biconvex lens AP (first lens) with positive refractive power and a lens AN (second lens) with negative refractive power.

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

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

[0030] The zoom lens of each embodiment is configured with first, second, and third lens groups with positive, negative, and positive refractive powers arranged in that order from the object side to the image side to effectively correct aberrations throughout the entire zoom range while shortening the overall lens length at the wide-angle end. By configuring the lens with at least four groups, spherical aberration and coma 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 due to manufacturing errors become significant. For this reason, the zoom lens of each embodiment is a so-called positive-lead zoom type in which the first lens group L1 has positive refractive power, and the height of incidence of axial rays on each lens element closer to the image side than the second lens group L2 is reduced, thereby achieving compactness and improved robustness.

[0031] Furthermore, in order to ensure compactness and a high zoom ratio, zooming is performed by changing the spacing between each lens group so that the spacing between the first lens group L1 and the second lens group L2 is wider at the telephoto end than at the wide-angle end, and the spacing between the second lens group L2 and the third lens group L3 is narrower.

[0032] The lens group GP is composed of the third lens group L3, or, if the lens group arranged adjacent to the third lens group L3 on the image side has positive refractive power, it is composed of the third lens group L3 and that lens group with positive refractive power. Furthermore, the lens group GP includes, arranged in order from the object side to the image side, a cemented lens A with negative refractive power and a cemented lens B with positive refractive power. The lens group GP, which performs magnification, has positive refractive power overall and includes multiple lenses. To achieve compactness and suppress fluctuations in spherical aberration and coma aberration due to zooming, the spacing between some of the lens groups with positive refractive power may be changed.

[0033] The cemented lens A is composed of a biconvex positive lens AP and a negative lens AN, arranged in that order from the object side to the image side. By providing the cemented lens A, it becomes easier to suppress variations in spherical aberration and coma aberration for each wavelength, which can be an issue when increasing the aperture. Furthermore, when the refractive power of the positive lens AP is increased, the radius of curvature becomes smaller. As a result, by providing the cemented lens A, robustness is ensured against manufacturing errors in coma aberration due to decentering, which can be an issue, and good optical performance can be more easily ensured.

[0034] If the refractive index of the negative lens element AN is higher than that of the positive lens element AP, the cemented surface will have divergence, which is unfavorable for correcting chromatic aberration but makes it easier to correct spherical aberration. If the opposite is true, the cemented surface will have convergence, which is advantageous for correcting chromatic aberration but makes it difficult to correct spherical aberration. For this reason, by placing cemented lens element B on the image side of cemented lens element A, and creating a configuration with two cemented lens elements, it is possible to make up for the insufficient correction of various aberrations caused by the selection of glass materials and suppress various aberrations without using many aspherical lenses.

[0035] Conditional formula (1) defines the focal length of the negative lens element AN in terms of the focal length of the lens element GP at the wide-angle end, and is intended to ensure the lens element GP's share of the magnification change and to effectively correct spherical aberration and coma. If the upper limit of conditional formula (1) is exceeded and the refractive power of the negative lens element AN becomes stronger relative to that of the lens element GP, it becomes difficult to ensure the lens element's share of the magnification change, resulting in an increase in the overall lens length at the telephoto end. If the lower limit of conditional formula (1) is exceeded and the refractive power of the negative lens element AN becomes weak, the axial incident light beam on the cemented lens element B becomes strongly convergent, making it difficult to suppress coma at wide-angle ranges.

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

[0037] Furthermore, it is preferable that the numerical ranges of the conditional expressions (1) and (2) satisfy 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 conditional expression (1a), it is possible to suppress axial chromatic aberration at wide angles and to easily suppress coma aberration. By satisfying conditional expression (2a), it is possible to suppress spherical aberration at the telephoto side and to shorten the overall lens length, which is preferable.

[0039] It is more preferable that the numerical ranges of the conditional expressions (1) and (2) be within 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 conditional expressions (1) and (2), it is possible to achieve a wide-angle, compact zoom lens that effectively corrects various aberrations such as chromatic aberration and spherical aberration and is robust against manufacturing errors.

[0041] The zoom lens of each embodiment can also adopt the following configuration as an alternative.

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

[0043] Furthermore, as another means, the zoom lens of each embodiment satisfies the following conditional expressions (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 the wide-angle end, fAN is the focal length of the negative lens AN, and ndAN is the refractive index of the negative lens AN (optical element) at the d-line.

[0045] It should be noted that the description of the above zoom lens configuration and conditions that overlap with the configuration and conditions of the zoom lens described above will be omitted.

[0046] Conditional formula (3) defines the refractive index of the negative lens element AN at the d-line. If the refractive index of the negative lens element AN is increased, spherical aberration is easier to correct, but the cemented surface will have divergence, which is unfavorable for correcting chromatic aberration. To achieve both chromatic aberration and spherical aberration correction with the cemented lens element A, particularly in the wide-angle range, it is important to optimize the refractive index of the negative lens element AN. If the refractive index becomes higher than the upper limit of conditional formula (3), the radius of curvature of the cemented surface of the cemented lens element A will become too large, making it difficult to simultaneously correct first-order chromatic aberration and coma. If the refractive index becomes lower than the lower limit of conditional formula (3), it will become difficult to suppress higher-order spherical aberration.

[0047] Furthermore, it is preferable that the numerical ranges of the conditional expressions (1) and (3) satisfy 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 conditional expression (1a), it is possible to suppress axial chromatic aberration in the wide-angle range while also easily suppressing coma. By satisfying conditional expression (3a), it is possible to easily suppress spherical aberration and coma over the entire zoom range, which is preferable.

[0049] It is more preferable that the numerical ranges of the conditional expressions (1) and (3) be within 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 conditional expressions (1) and (3), it is possible to achieve a wide-angle, compact zoom lens that effectively corrects various aberrations such as chromatic aberration and spherical aberration and is robust against manufacturing errors.

[0051] Next, conditions that are preferably satisfied in the zoom lens of each embodiment will be described: It is preferable that the zoom lens of each embodiment satisfy one or more of the following conditional expressions (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 the positive lens AP. νdAN is the Abbe number of the 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 unit L1, second lens unit L2, and third lens unit L3, respectively. fw and ft are the focal lengths of the zoom lens at the wide-angle end and telephoto end, respectively. νd3P is the average Abbe number of the positive lenses in the third lens unit L3.

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

[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 lens surface on the object side of cemented lens A, and ANR2 is the radius of curvature of the lens surface on the image side. If the lens surface is aspherical, this means its base R (the radius of the reference quadratic curved surface).

[0055] SFA = -(ANR2 + APR1) / (ANR2 - APR1) Conditional formula (4) defines the shape factor of cemented lens A, and is intended to achieve compactness while simultaneously correcting spherical aberration and axial chromatic aberration. When the value of conditional formula (4) is 1, cemented lens A has a plano-concave shape with the concave surface facing the image side. Exceeding the upper limit of conditional formula (4) makes it difficult to effectively correct coma at the wide-angle end and increases the zoom fluctuation of spherical aberration, which is undesirable. Falling below the lower limit of conditional formula (4) undesirably increases spherical aberration and axial chromatic aberration at the telephoto end.

[0056] Conditional formula (5) defines the radius of curvature of the cemented surface of cemented lens A in terms of the focal length of lens group GP at the wide-angle end. Increasing the magnification contribution of lens group GP is effective for reducing the size of a zoom lens, but it is necessary to achieve achromatism at the same time. Conditional formula (5) is intended to optimize the correction of axial chromatic aberration and the magnification contribution. Exceeding the upper limit of conditional formula (5) undesirably results in the radius of curvature of the cemented surface becoming too large relative to the magnification contribution, resulting in insufficient correction of axial chromatic aberration at the telephoto end. Falling below the lower limit of conditional formula (5) undesirably weakens the refractive power of lens group GP, resulting in an increase in the amount of movement of lens group GP from the wide-angle end to the telephoto end in order to ensure a predetermined magnification ratio, undesirably resulting in an increase in the size of the zoom lens.

[0057] Conditional formula (6) defines the Abbe number of the material of the positive lens AP, and is intended to suppress axial chromatic aberration and to compensate for insufficient correction of chromatic aberration in the first lens unit L1 and the second lens unit L2 with the lens unit GP. Exceeding the upper limit of conditional formula (6) is advantageous for correcting axial chromatic aberration, but makes it difficult to ensure the desired refractive power for the glass material. Falling below the lower limit of conditional formula (6) is undesirable because it makes it difficult to achieve first-order achromatism for axial chromatic aberration and lateral chromatic aberration.

[0058] Conditional formula (7) defines the ratio of the Abbe number of the positive lens AP to the Abbe number of the negative lens AN in the cemented lens A, and is intended to achieve both correction of axial chromatic aberration and correction of spherical aberration and coma. If the upper limit of conditional formula (7) is exceeded, the Abbe number of the positive lens AP and the Abbe number of the negative lens AN become close, weakening the achromatic effect due to the characteristics of the glass material. This requires a lens other than the cemented lens A to perform achromatism, undesirably increasing the number of lenses or the overall lens length. If the lower limit of conditional formula (7) is exceeded, the achromatic effect due to the characteristics of the glass material 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 creating problems with correcting chromatic aberration, undesirably.

[0059] Conditional expression (8) defines the ratio between the focal length fA of cemented lens A and the focal length fB of cemented lens B, and is intended to achieve both correction of axial chromatic aberration and correction of spherical aberration and coma. Satisfying conditional expression (8) also optimizes the aberration correction load shared by the two cemented lens sets A and B, making it easier to ensure robustness against decentering, which can be an issue when increasing the aperture and zoom ratio. Exceeding the upper limit of conditional expression (8) is undesirable because the refractive power of cemented lens A becomes too strong, making it more likely that the light beam entering cemented lens B will become divergent and increasing coma due to decentering of cemented lens B. Falling below the lower limit of conditional expression (8) is undesirable because the refractive power of cemented lens A becomes too weak, making it more likely that insufficient correction of spherical aberration will occur, particularly at the telephoto end.

[0060] Conditional expression (9) defines the focal length of the first lens group L1 in terms of the focal length of the second lens group L2, and is intended to maintain an appropriate zoom ratio while minimizing the size of the zoom lens. In a zoom lens with a relatively fast focal length on the telephoto side, if the refractive power of the first lens group L1 is not appropriately maintained within a range that allows for aberration correction, the overall length of the zoom lens on the telephoto side will increase, and the front lens diameter will need to be increased to ensure adequate peripheral illumination. Exceeding the upper limit of conditional expression (9) undesirably increases aberration fluctuations in the first and second lens groups L1 and L2 during zooming, making it particularly difficult to correct spherical aberration. Failing the lower limit of conditional expression (9) undesirably increases the overall length of the zoom lens, making it difficult to ensure adequate peripheral illumination.

[0061] Conditional expression (10) defines the focal length of the first lens unit L1 as the focal length of the zoom lens at the wide-angle end, and is intended to optimize the share of magnification changes while achieving compactness. By setting the desired refractive power for the first lens unit L1, the amount of movement of the first lens unit L1 during zooming can be reduced. Exceeding the upper limit of conditional expression (10) weakens the refractive power of the first lens unit L1, weakening the magnification change effect. Therefore, increasing the amount of movement of the first lens unit L1 during zooming to compensate for the magnification change effect would undesirably increase the overall length at the telephoto end. Furthermore, exceeding the upper limit of conditional expression (10) would require the third lens unit L3 and subsequent lens units to ensure the share of magnification changes, which would result in significant spherical aberration, coma, and other aberrations occurring at the telephoto end. As a result, an increase in the number of lenses and aspherical lenses required for aberration correction would undesirably reduce robustness to manufacturing errors. If the lower limit of conditional expression (10) is not reached, the refractive power of the first lens unit L1 becomes too strong, and more spherical aberration occurs from the first lens unit L1 on the telephoto side, which is undesirable.

[0062] Conditional expression (11) defines the focal length of the third lens unit L3 in terms of the focal length of the second lens unit L2, and is intended to ensure a proper share of the magnification change while favorably correcting spherical aberration and coma. Exceeding the upper limit of conditional expression (11) is undesirable because the refractive power of the third lens unit L3 becomes too weak, weakening the magnification change function and increasing the amount of movement of the third lens unit L3 during zooming. Falling below the lower limit of conditional expression (11) is undesirable because the refractive power of the third lens unit L3 becomes too strong, resulting in spherical aberration, coma, and astigmatic difference at the telephoto end and the center of the image.

[0063] Conditional expression (12) defines the focal length of the third lens group L3 in terms of 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 compactness of the zoom lens. Exceeding the upper limit of conditional expression (12) is undesirable, as the refractive power of the third lens group L3 becomes too weak, which tends to increase field curvature on the telephoto side. Falling below the lower limit of conditional expression (12) is undesirable, as the refractive power of the third lens group L3 becomes too strong, which causes fluctuations in coma aberration with respect to image height on the telephoto side.

[0064] Conditional expression (13) defines the average Abbe number of the positive lenses included in the third lens unit L3, and is intended to reduce the overall lens length and suppress axial chromatic aberration and lateral chromatic aberration. Exceeding the upper limit of conditional expression (13) is advantageous for suppressing axial chromatic aberration and lateral chromatic aberration, but is undesirable because the radius of curvature of the lens approaches zero, resulting in insufficient correction of spherical aberration and coma. Falling below the lower limit of conditional expression (13) is undesirable because chromatic aberration increases, making it difficult to correct aberrations throughout the zoom lens.

[0065] It is more preferable that the numerical ranges of the 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) Satisfying conditional expression (4a) makes it possible to more appropriately correct spherical aberration at wide-angle positions, facilitating the achievement of a larger aperture. Satisfying conditional expression (5a) makes it easy to appropriately correct longitudinal chromatic aberration and allocate magnification. Satisfying conditional expression (6a) makes it easy to more appropriately correct longitudinal chromatic aberration at telephoto positions. Satisfying conditional expression (7a) makes it easy to suppress fluctuations in longitudinal chromatic aberration caused by zooming. Satisfying conditional expression (8a) makes it easy to more appropriately allocate aberration correction between the two cemented lens elements. Satisfying conditional expression (9a) makes it easy to shorten the overall lens length. Satisfying conditional expression (10a) makes it easy to simultaneously correct chromatic aberration of magnification at wide-angle positions and spherical aberration at telephoto positions. Satisfying conditional expression (11a) makes it easy to more appropriately allocate magnification to the third lens unit L3, facilitating the suppression of fluctuations in coma caused by zooming. By satisfying conditional expression (12a), it becomes easier to suppress fluctuations in coma with respect to the angle of view in the telephoto range, and by satisfying conditional expression (13a), it becomes easier to reduce the overall lens length.

[0067] It is more preferable that the numerical ranges of the conditional expressions (4) to (13) satisfy 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, the configurations that are preferably satisfied in the zoom lens of each embodiment will be described.

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

[0070] This configuration allows the number of lenses in the first lens unit L1, which has a large lens diameter, to be reduced, resulting in a smaller and lighter lens.In addition, the height of light rays emerging from the first lens unit L1 can be lowered, allowing for excellent correction of off-axis aberrations such as coma and field curvature.

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

[0072] Preferably, the second lens group L2 is made up of four spherical lenses, arranged in the following 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 using spherical lenses in the second lens group L2, surface shape errors (errors due to astigmatism and quirks) that tend to occur with aspherical lenses can be reduced.

[0073] This configuration enhances the refractive power of the second lens unit L2, while simultaneously correcting chromatic aberration of magnification and curvature of field in the wide-angle range and spherical aberration in the telephoto range. By locating a negative lens closest to the object in the second lens unit L2, the power arrangement within the second lens unit L2 can be made retrofocus, providing excellent correction for curvature of field and coma in the wide-angle range.

[0074] The third lens group L3 preferably includes a single lens with positive refractive power and convex facing the object side, located closest to the object. The light beams incident on the third lens group L3 from the second lens group L2 for the main magnification change are at a high ray height, which can cause high-order spherical aberration and coma. Therefore, to effectively suppress the occurrence of spherical aberration and coma, a single lens with positive refractive power and convex facing the object side is located closest to the object side of the third lens group L3, thereby converging the light beams diverged by the second lens group L2.

[0075] Furthermore, in the lens group arranged closest to the image, it is preferable that the lens arranged closest to the image is a positive lens that is convex toward the image side. This configuration makes it relatively easy to ensure back focus and also makes it possible to suppress the collection of unwanted light (ghosts) caused by the image sensor.

[0076] It is also preferable that the rear group RG has at least one aspherical surface. This configuration makes it possible to effectively correct curvature of field at the wide-angle end while also achieving a compact zoom lens.

[0077] Furthermore, it is preferable that the image-side lens adjacent to the aperture stop SP be made up of a biconvex lens element (single lens or cemented lens) with a strongly convex shape facing the object side. By arranging a lens surface with a strongly convex shape facing the aperture stop SP, it becomes easier to suppress spherical aberration that occurs with larger apertures and to correct various off-axis aberrations in the wide-angle range. Furthermore, by configuring the strongly convex lens element to have an aspherical surface, it becomes easier to correct spherical aberration, coma aberration, and field curvature at the same time.

[0078] In the zoom lens of each embodiment, any of the lens groups may be configured to perform vibration reduction by moving all or part of the lens group as a vibration reduction group so as to include a component in a direction perpendicular to the optical axis, or by rotating (oscillating) the lens group in an in-plane direction including the optical axis. In particular, it is preferable that the cemented lens B be used as the vibration reduction group. There are no particular restrictions on the number or shape of lenses in the vibration reduction group. It is also preferable that the vibration reduction group have positive refractive power. It is also preferable that the vibration reduction group be configured as part of one lens group, and more preferably as the central portion of one lens group divided into three sections.

[0079] In the zoom lens of each embodiment, focusing can also be performed by moving all or part of any of the lens groups as a focus group so as to include a component in the optical axis direction.

[0080] Next, the zoom lens of each embodiment will be described in detail.

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

[0082] In the zoom lens of Example 1, the first lens unit L1 moves monotonically toward the object side during zooming from the wide-angle end to the telephoto end. The lens units move so that, at the telephoto end compared to the wide-angle end, the distance between the first lens unit L1 and the second lens unit L2 is wider, the distance between the second lens unit L2 and the third lens unit L3 is narrower, and the distance between the third lens unit L3 and the fourth lens unit L4 is wider. During focusing, the fifth lens unit L5 moves.

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

[0084] In Examples 2 and 4, cemented lens A is a lens element with negative refractive power formed by cementing together a ninth lens and a tenth lens. Cemented lens B is a lens element with positive refractive power formed by cementing together an eleventh lens and a twelfth lens. In Example 3, cemented lens A is a lens element with negative refractive power formed by cementing together a tenth lens and an eleventh lens, and cemented lens B is a lens element with positive refractive power formed by cementing together a twelfth lens and a thirteenth lens.

[0085] In the zoom lenses of Examples 2, 3, and 4, the first lens unit L1 moves monotonically toward the object side during zooming from the wide-angle end to the telephoto end. The lens units move so that the distance between the first lens unit L1 and the second lens unit L2 is wider at the telephoto end than at the wide-angle end, and the distance between the second lens unit L2 and the third lens unit L3 is narrower. During focusing, the fourth lens unit L4 moves.

[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. Cemented lens A is a lens element with negative refractive power formed by cementing together the ninth and tenth lenses. Cemented lens B is a lens element with positive refractive power formed by cementing together the eleventh and twelfth lenses.

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

[0088] In Example 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. Cemented lens A is a lens element with negative refractive power formed by cementing together the ninth and tenth lenses. Cemented lens B is a lens element with positive refractive power formed by cementing together the eleventh and twelfth lenses.

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

[0090] Numerical Examples 1 to 6 corresponding to Examples 1 to 6, respectively, are shown below.

[0091] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial spacing (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. Also, nd represents the refractive index of each optical element at the d-line, and vd represents the Abbe number of the optical element. Note that the Abbe number vd and partial dispersion ratio θgF of a certain material are given by the following 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, respectively: νd=(Nd-1) / (NF-NC) θgF=(Ng-NF) / (NF-NC) It is expressed as:

[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 object at infinity. "Back focus BF" is the distance on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. "Total lens length" is the distance on the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final lens surface plus the back focus. "Lens group" is not limited to cases where it is composed of multiple lenses, but also includes cases where it is composed of a single lens.

[0093] If the optical surface is aspherical, an asterisk (*) is added to the right of the surface number. The aspherical shape is expressed as follows: X is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10, and A12 are the aspherical coefficients of each order. x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 In addition, "e±XX" in each aspherical coefficient is "×10± XX " means.

[0094] [Numerical Example 1] Unit: mm Surface Data Surface number rd 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 ∞ Aspheric 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 Mid-range Telephoto Focal length 15.45 36.03 67.94 F-number 4.12 4.12 4.12 Half angle of view (°) 41.27 19.59 10.60 Image height 12.66 13.66 13.66 Lens total 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 May 26 -22.29 6 28 -176.06 7 30 60.47 [Numerical Example 2] Unit: mm Surface Data Surface 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 ∞ Aspheric 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 Mid-range Telephoto Focal length 15.45 36.49 68.04 F-number 2.88 3.86 4.12 Half angle of view (°) 41.38 19.53 10.61 Image height 12.66 13.66 13.66 Lens total 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 Surface 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 ∞ Aspheric 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 Mid-range Telephoto Focal length 15.45 36.47 68.05 F-number 2.88 3.81 4.12 Half angle of view (°) 41.28 19.17 10.42 Image height 12.66 13.66 13.66 Lens total 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 Surface 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 ∞ Aspheric 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 Mid-range Telephoto Focal length 15.45 36.29 83.77 F-number 2.88 4.00 5.80 Half angle of view (°) 41.36 19.65 8.71 Image height 12.66 13.66 13.66 Lens total length 101.54 116.35 133.85 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 Surface 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 ∞ Aspheric 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 Mid-range Telephoto Focal length 16.45 36.35 83.81 F-number 2.88 4.00 5.80 Half angle of view (°) 39.72 20.12 8.62 Image height 12.66 13.66 13.66 Lens total 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 Surface 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 ∞ Aspheric 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 Mid-range Telephoto Focal length 16.48 36.15 83.82 F-number 2.88 4.00 5.80 Half angle of view (°) 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 that uses a zoom lens of the present invention as an imaging optical system will be described with reference to Fig. 13. In Fig. 13, 13 denotes a camera body, and 11 denotes an imaging optical system configured with any of the zoom lenses described in Examples 1 to 6. 12 denotes a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the camera body and receives and photoelectrically converts an optical image formed by imaging optical system 11. Camera body 13 may be a so-called single-lens reflex camera that has a quick-turn mirror, or a so-called mirrorless camera that does not have a quick-turn mirror.

[0097] In this way, by applying the zoom lens of the present invention to an imaging device such as a digital still camera, an imaging device with a small lens can be obtained.

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

[0099] L1 First lens group L2 Second lens group L3: Third lens group RG rear group A First cemented lens B Second cemented lens AP 1st lens AN 2nd lens

Claims

1. A zoom lens comprising, arranged in order from the object side to the image side, 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 rear group including two or more lens groups, wherein the spacing between adjacent lens groups changes during zooming, During 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 increases, and the distance between the second lens group and the third lens group decreases. When the third lens group or the lens group disposed adjacent to the third lens group on the image side is a lens group having positive refractive power, and the lens group consisting of the third lens group and the lens group having positive refractive power is defined as a positive group, the positive group includes a first cemented lens having negative refractive power and a second cemented lens having positive refractive power arranged on the image side of the first cemented lens, the first cemented lens is composed of a first lens having a positive refractive power and a second lens having a negative refractive power, When the focal length of the positive group at the 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 A zoom lens characterized by satisfying the following conditional expressions:

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

3. When the Abbe number of the first lens in the first cemented lens is νdAP, 70.5<νdAP<100.0 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

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 4. The zoom lens according to claim 1, wherein the following condition is satisfied:

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 5. The zoom lens according to claim 1, wherein the following condition is satisfied:

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 6. The zoom lens according to claim 1, wherein the following condition is satisfied:

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 7. The zoom lens according to claim 1, wherein the following condition is satisfied:

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 8. The zoom lens according to claim 1, wherein the following condition is satisfied:

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 9. The zoom lens according to claim 1, wherein the following condition is satisfied:

10. When the average Abbe number of the positive lenses in the third lens group is νd3P, 56<νd3P<80 10. The zoom lens according to claim 1, wherein the following condition is satisfied:

11. 11. The zoom lens according to claim 1, wherein the first lens group is made up of three or less lenses.

12. 12. The zoom lens according to claim 1, wherein the first lens group consists of, arranged in order from the object side to the image side, a cemented lens of a negative lens and a positive lens, and a single lens having a meniscus shape and positive refractive power.

13. 13. The zoom lens according to claim 1, wherein the second lens group is composed of four spherical lenses, arranged in order from the object side to the image side: a negative lens, a negative lens, a positive lens, and a negative lens.

14. 14. The zoom lens according to claim 1, wherein the third lens group includes a single lens element having positive refractive power and convex toward the object side, the single lens element being arranged closest to the object side.

15. 15. The zoom lens according to claim 1, wherein in the zoom lens, the lens arranged closest to the image side among the lens group arranged closest to the image side is a positive lens that is convex toward the image side.

16. 16. The zoom lens according to claim 1, wherein the rear group has an aspherical surface.

17. 17. The zoom lens according to claim 1, wherein a lens element on the image side adjacent to the aperture stop is a biconvex lens element.

18. 18. The zoom lens according to claim 1, wherein the rear group includes, in order from the object side to the image side, a fourth lens group and a fifth lens group, each having a positive refractive power.

19. 19. The zoom lens according to claim 1, wherein the rear group includes, in order from the object side to the image side, a fourth lens group and a fifth lens group, each having a negative refractive power.

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

Images