Zoom lens and imaging apparatus having the same

Abstract

To provide a compact zoom lens that satisfactorily corrects aberration fluctuation in image blur correction and can obtain high optical performance during image blur correction over an entire zoom range.SOLUTION: A zoom lens comprises a front group (LN) having negative refractive power and a rear group (LP) having positive refractive power as a whole, arranged in order from an object side to an image side. The rear group has a first subgroup (SL1) having positive refractive power, a second subgroup (SL2) having positive refractive power, a third subgroup (SL3) having negative refractive power, and a fourth subgroup (SL4), arranged in order from the object side to the image side. The front group has a positive meniscus lens with a convex surface facing the object side. A distance between the front group and the rear group changes when zooming, and a distance between the third subgroup and the fourth subgroup changes when either zooming or focusing. The first subgroup, the third subgroup, and the fourth subgroup do not move in image blur correction, and the second subgroup moves so as to have a component in a direction perpendicular to an optical axis in image blur correction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a zoom lens and an imaging device having the same, and is particularly suitable for imaging devices such as digital still cameras, video cameras, surveillance cameras, and vehicle-mounted cameras. [Background technology]

[0002] In recent years, there has been a demand for zoom lenses with a small overall system and high resolution (high optical performance) in digital still cameras and video cameras.

[0003] There is also a demand for zoom lenses to be equipped with a mechanism (anti-vibration mechanism) that compensates for image blur (image shake) that occurs when accidental vibrations such as camera shake are transmitted to the zoom lens. A known zoom lens that meets these demands is a negative-lead zoom lens, in which a lens group with negative refractive power is positioned closest to the object. Among these negative-lead zoom lenses, there is also known a zoom lens that has an anti-vibration mechanism that compensates for image blur by moving some of the lens groups (anti-vibration group, image stabilization group) so that they have a component perpendicular to the optical axis (Patent Document 1, Patent Document 2).

[0004] Patent Document 1 discloses a zoom lens with a three- or four-group configuration having, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent group with negative or positive refractive power. The zoom lens disclosed in Patent Document 1 performs image blur correction by moving some of the lens elements in the second lens group in a direction perpendicular to the optical axis.

[0005] Patent Document 2 discloses a zoom lens with a four-group configuration consisting of, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power, and a fourth lens group with negative refractive power. The zoom lens in Patent Document 2 discloses a zoom lens in which image shake correction is performed by a lens portion in the second lens group, and focusing is performed by moving the third lens group in the optical axis direction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-025572 [Patent Document 2] Japanese Patent Application Publication No. 2019-008235 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, when image blur correction is performed by moving an image blur correction group in a direction perpendicular to the optical axis, there has been a demand for the image blur correction group to be small and lightweight in order to reduce the size of the movement mechanism (anti-vibration mechanism) and to save power. There has also been a demand for small aberration fluctuations, particularly chromatic aberration fluctuations, during image blur correction, and for good optical performance to be maintained even during image blur correction.

[0008] Generally, some lens groups in a zoom lens are designated as image stabilization groups, and image stabilization can be achieved by moving them perpendicular to the optical axis. However, if the lens configuration of the zoom lens and the lens configuration of the image stabilization group that is moved for image stabilization are not appropriate, the amount of movement of the image stabilization group will be large to achieve the desired amount of image stabilization. Alternatively, the optical performance during image stabilization may be significantly reduced, or the lens diameter of the image stabilization group may become large. For this reason, in a zoom lens with an image stabilization mechanism, it is important to appropriately set the overall zoom configuration and the lens configuration of the image stabilization group. In particular, it is necessary to appropriately set the number of lens groups that make up the zoom lens, the refractive power of each lens group, the configuration of the image stabilization group, and the like.

[0009] The present invention provides a compact zoom lens that satisfactorily corrects aberration fluctuations during image blur correction and provides high optical performance during image blur correction over the entire zoom range. [Means for solving the problem]

[0010] One aspect of the present invention provides a zoom lens comprising: a front group having negative refractive power and a rear group having positive refractive power overall, arranged in order from the object side to the image side, the rear group having, arranged in order from the object side to the image side, a first subgroup having positive refractive power, a second subgroup having positive refractive power, a third subgroup having negative refractive power, and a fourth subgroup, the distance between the front group and the rear group changing during zooming, the distance between the third subgroup and the fourth subgroup changing during at least one of zooming and focusing, the first subgroup, the third subgroup, and the fourth subgroup remaining stationary during image shake correction, the second subgroup being a cemented lens formed by cementing a positive lens and a negative lens, and moving during the image shake correction so as to have a component perpendicular to the optical axis. Other objects and features of the present invention will be described in the following embodiments. [Effects of the Invention]

[0011] According to the present invention, it is possible to realize a compact zoom lens that satisfactorily corrects aberration fluctuations during image shake correction and has high optical performance during image shake correction over the entire zoom range. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a lens cross-sectional view of a zoom lens of Example 1 at a wide-angle 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] 4A to 4C are diagrams showing lateral aberrations after an image position is displaced by 0.3 degrees at the telephoto end of the zoom lens of Example 1. [Figure 4] FIG. 10 is a cross-sectional view of a zoom lens according to a second embodiment at the wide-angle end. [Figure 5] 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 6] 10A and 10B are diagrams illustrating lateral aberrations after an image position is displaced by 0.3 degrees at the telephoto end of the zoom lens according to the second embodiment. [Figure 7]FIG. 10 is a cross-sectional view of a zoom lens at the wide-angle end according to a third embodiment. [Figure 8] 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 9] 10A and 10B are diagrams illustrating lateral aberrations after an image position is displaced by 0.3 degrees at the telephoto end of the zoom lens according to the third embodiment. [Figure 10] FIG. 10 is a lens cross-sectional view of a zoom lens of Example 4 at the wide-angle end. [Figure 11] 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 12] 10A and 10B are diagrams illustrating lateral aberrations after an image position displacement of 0.3 degrees at the telephoto end of the zoom lens according to Example 4. FIG. [Figure 13] FIG. 10 is a lens cross-sectional view of a zoom lens of Example 5 at the wide-angle end. [Figure 14] 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 15] 10A and 10B are diagrams illustrating lateral aberrations after an image position displacement of 0.3 degrees at the telephoto end of the zoom lens of Example 5. [Figure 16] 1 is a schematic diagram illustrating a main part of an imaging device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0014] FIG. 1 is a cross-sectional view of a zoom lens according to a first embodiment of the present invention at the wide-angle end (short focal length end). FIGS. 2A, 2B, and 2C are aberration diagrams of the zoom lens according to the first embodiment at the wide-angle end, at a middle zoom position, and at the telephoto end, respectively. The zoom lens according to the first embodiment has a zoom ratio of 2.74 and an aperture ratio of approximately 4.1 to 7.3. FIG. 3 is a lateral aberration diagram of the zoom lens according to the first embodiment at the telephoto end after an image position displacement of 0.3 degrees.

[0015] Fig. 4 is a lens cross-sectional view of a zoom lens according to a second embodiment of the present invention at the wide-angle end. Figs. 5(A), (B), and (C) are aberration diagrams of the zoom lens according to the second embodiment at the wide-angle end, at the intermediate zoom position, and at the telephoto end, respectively. The zoom lens according to the second embodiment has a zoom ratio of 2.77 and an aperture ratio of approximately 4.1 to 7.3. Fig. 6 is a lateral aberration diagram of the zoom lens according to the second embodiment at the telephoto end after an image position displacement of 0.3 degrees.

[0016] Fig. 7 is a lens cross-sectional view of a zoom lens according to Example 3 of the present invention at the wide-angle end. Figs. 8(A), (B), and (C) are aberration diagrams of the zoom lens according to Example 3 at the wide-angle end, at the intermediate zoom position, and at the telephoto end, respectively. The zoom lens according to Example 3 has a zoom ratio of 2.35 and an aperture ratio of approximately 4.1 to 7.2. Fig. 9 is a lateral aberration diagram of the zoom lens according to Example 3 at the telephoto end after an image position displacement of 0.3 degrees.

[0017] Fig. 10 is a lens cross-sectional view of a zoom lens according to Example 4 of the present invention at the wide-angle end. Figs. 11(A), (B), and (C) are aberration diagrams of the zoom lens according to Example 4 at the wide-angle end, at the intermediate zoom position, and at the telephoto end, respectively. The zoom lens according to Example 4 is a zoom lens with a zoom ratio of 2.77 and an aperture ratio of approximately 4.1 to 7.3. Fig. 12 is a lateral aberration diagram of the zoom lens according to Example 4 at the telephoto end after an image position displacement of 0.3 degrees.

[0018] Fig. 13 is a lens cross-sectional view of a zoom lens according to Example 5 of the present invention at the wide-angle end. Figs. 14(A), (B), and (C) are aberration diagrams of the zoom lens according to Example 5 at the wide-angle end, at the intermediate zoom position, and at the telephoto end, respectively. The zoom lens according to Example 5 is a zoom lens with a zoom ratio of 2.78 and an aperture ratio of approximately 4.1 to 7.3. Fig. 15 is a lateral aberration diagram of the zoom lens according to Example 5 at the telephoto end after an image position displacement of 0.3 degrees.

[0019] The zoom lens as the optical system of each embodiment is used in imaging devices such as digital still cameras, video cameras, surveillance cameras, and vehicle-mounted cameras.

[0020] In the lens cross-sectional views of each embodiment, the left side is the object side (front) and the right side is the image side (rear). SP is the aperture. IP is the image plane, on which the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed when used as the photographic optical system of a digital still camera or video camera. Furthermore, when used as the photographic optical system of a silver halide film camera, the photosensitive surface of the film surface is placed.

[0021] In the zoom lenses of Examples 1 and 2, the rear group LP includes, in order from the object side to the image side, a first subgroup SL1 with positive refractive power, a second subgroup SL2 with positive refractive power, a third subgroup SL3 with negative refractive power, a fourth subgroup SL4 with positive refractive power, and a fifth subgroup SL5 with negative refractive power. The second subgroup SL2 moves during image blur correction. During zooming, the spacing between adjacent subgroups from the first subgroup SL1 to the third subgroup SL3 is fixed, while the spacing between the third subgroup SL3 and the fourth subgroup SL4 and the spacing between the fourth subgroup SL4 and the fifth subgroup SL5 change. During focusing from infinity to a close distance, the fourth subgroup moves from the image side to the object side. The rear group LP also includes a diaphragm disposed between the first subgroup SL1 and the second subgroup SL2.

[0022] In the zoom lens of Example 3, the rear group LP includes, in order from the object side to the image side, a first subgroup SL1 with positive refractive power, a second subgroup SL2 with positive refractive power, a third subgroup SL3 with negative refractive power, and a fourth subgroup SL4 with positive refractive power. The second subgroup SL2 moves during image shake correction. During zooming, the spacing between adjacent subgroups from the first subgroup SL1 to the third subgroup SL3 is fixed, while the spacing between the third subgroup SL3 and the fourth subgroup SL4 changes. During focusing from infinity to a close distance, some lenses in the fourth subgroup SL4 move from the image side to the object side. The rear group LP also includes a diaphragm disposed between the first subgroup SL1 and the second subgroup SL2.

[0023] In the zoom lens of Example 4, the rear group LP includes, in order from the object, a first subgroup SL1 with positive refractive power, a second subgroup SL2 with positive refractive power, a third subgroup SL3 with negative refractive power, a fourth subgroup SL4 with positive refractive power, and a fifth subgroup SL5 with negative refractive power. The second subgroup SL2 moves during image shake correction. During zooming, the spacing between adjacent subgroups changes from the first subgroup SL1 to the fifth subgroup SL5. During focusing from infinity to a close distance, the fourth subgroup SL4 moves from the image side to the object side. The rear group LP also includes a diaphragm disposed between the first subgroup SL1 and the second subgroup SL2.

[0024] In the zoom lens of Example 5, the rear group LP includes, in order from the object, a first subgroup SL1 with positive refractive power, a second subgroup SL2 with positive refractive power, a third subgroup SL3 with negative refractive power, a fourth subgroup SL4 with positive refractive power, and a fifth subgroup SL5 with negative refractive power. The second subgroup SL2 moves during image blur correction. During zooming, the distance between the first subgroup SL1 and the second subgroup SL2 is fixed, while the distances between the second subgroup SL2 and the third subgroup SL3, the distance between the third subgroup SL3 and the fourth subgroup SL4, and the distance between the fourth subgroup SL4 and the fifth subgroup SL5 change. During focusing from infinity to a close distance, the fourth subgroup SL4 moves from the image side to the object side. The rear group LP also includes a diaphragm disposed between the first subgroup SL1 and the second subgroup SL2.

[0025] Each subgroup may be made up of one lens or a plurality of lenses.

[0026] In the aberration diagrams of each example, Fno is the F-number and ω is the half angle of view (°). In the spherical aberration diagrams, d is the d-line (wavelength 587.56 nm) and g is the g-line (wavelength 435.835 nm).

[0027] In the astigmatism diagram, ΔS is the sagittal image plane at the d-line, and ΔM is the meridional image plane at the d-line. Distortion is shown for the d-line. The lateral chromatic aberration diagram is shown for the g-line.

[0028] The zoom lens of the present invention is composed of, in order from the object side to the image side, a front group LN having negative refractive power and a rear group LP having positive refractive power overall. The rear group LP also has, in order from the object side to the image side, at least a first subgroup SL1 having positive refractive power, a second subgroup SL2 having positive refractive power, a third subgroup SL3 having negative refractive power, and a fourth subgroup SL4. During image blur correction, the first subgroup SL1, the third subgroup SL3, and the fourth subgroup SL4 remain stationary, but the second subgroup SL2 moves so as to have a component perpendicular to the optical axis. During zooming, at least the distance between the front group LN and the rear group LP changes.

[0029] In a negative-lead zoom lens, by appropriately arranging lens subgroups with image stabilization mechanisms, it is possible to increase the number of image stabilization stages and reduce the lens size by suppressing the amount of movement during image stabilization. By arranging the first subgroup SL1 with positive refractive power on the object side of the second subgroup SL2, which is an image stabilization group with positive refractive power, it is possible to prevent the positive refractive power of the image stabilization group SL2 from becoming too strong. This makes it possible to achieve both correction of axial chromatic aberration and spherical aberration and correction of optical performance during image stabilization.

[0030] Furthermore, by disposing the third sub-unit SL3 having negative refractive power on the image side of the vibration reduction unit SL2, the positive refractive power of the vibration reduction unit SL2 can be optimized, making it possible to ensure both optical performance during image blur correction and an increase in the number of vibration reduction stages.

[0031] Furthermore, in the zoom lens of each embodiment, a fourth sub-unit SL4 is disposed on the image side of the third sub-unit SL3, which has negative refractive power. The distance between the third sub-unit SL3 and the fourth sub-unit SL4 changes during at least one of zooming and focusing. When focusing is performed on the image side of the third sub-unit SL3, it is possible to appropriately correct field curvature and lateral chromatic aberration, which are primarily caused by off-axial rays, while maintaining good optical performance from infinity shooting to close-up shooting. Furthermore, by changing the distance between the third sub-unit SL3 and the fourth sub-unit SL4 during zooming, it is possible to effectively correct fluctuations in various aberrations that occur during zooming.

[0032] As described above, a small negative lead type zoom lens can be obtained that satisfactorily corrects aberration fluctuations during image blur correction and has high optical performance even during image blur correction.

[0033] In each embodiment, it is more preferable to satisfy one or more of the following conditional expressions (1) to (7).

[0034] Here, the lateral magnification of the second sub-unit SL2 at the telephoto end is β22t, and the lateral magnification of all lenses on the image side of the second sub-unit SL2 at the telephoto end is β22rt. The focal length of the first sub-unit SL1 is f21p, the focal length of the second sub-unit SL2 is f22p, and the focal length of the third sub-unit SL3 is f23n. The combined focal length of the first sub-unit SL1 to the third sub-unit SL3 at the wide-angle end is f2w. The distance from the aperture stop SP to the object-side vertex of the second sub-unit SL2 at the wide-angle end is dw, and the total optical length of the entire system at the wide-angle end is Lw. The radius of curvature of the lens surface closest to the object in the third sub-unit SL3 is rn1, and the radius of curvature of the surface closest to the image in the third sub-unit SL3 is rn2.

[0035] 1.0<(1-β22t)×β22rt<3.0 (1) 0.5 <f21p / f22p<2.0 ···(2) -1.5 <f22p / f23n<-0.5 ···(3) 0.5 <f22p / f2w<2.0 ···(4) -2.0 <f23n / f2w<-0.5 ···(5) 0.01<|dw / Lw|<0.10 (6) -8.0<(rn1+rn2) / (rn1-rn2)<2.0 (7) Conditional formula (1) defines the image shift sensitivity of the second subunit SL2 at the telephoto end. Here, the image shift sensitivity TS is the ratio (TS=ΔI / ΔL) of the amount of vertical movement ΔL of the image blur correction unit when the image blur correction unit is moved in a direction perpendicular to the optical axis to the amount of movement ΔI of the image (imaging position) on the image plane at that time in a direction perpendicular to the optical axis.

[0036] By optimizing conditional expression (1), the amount of vertical movement of the second sub-unit SL2 during image blur correction can be reduced, making it possible to reduce the size of the lens.

[0037] If the upper limit of conditional expression (1) is exceeded, the amount of movement of the vibration reduction mechanism during image blur correction can be reduced, but the refractive power of the second sub-unit SL2 becomes stronger, leading to deterioration of spherical aberration.If the lower limit of conditional expression (1) is exceeded, the refractive power of the second sub-unit SL2 becomes weaker, the amount of movement of the second sub-unit SL2 required to achieve a predetermined amount of image blur correction increases, leading to an increase in the size of the vibration reduction mechanism, which is undesirable.

[0038] Conditional formula (2) defines the ratio between the focal length f21p of the first sub-unit SL1 and the focal length f22p of the second sub-unit SL2. By optimizing the refractive power of the two sub-units with positive refractive power, mainly within the rear unit LP, it is possible to suppress the amount of movement of the image stabilization mechanism while achieving good optical performance.

[0039] If the upper limit of conditional expression (2) is exceeded, the refractive power of the second sub-unit SL2 becomes strong, which can reduce the amount of movement of the vibration reduction mechanism during image blur correction, but this leads to an increase in spherical aberration. If the lower limit of conditional expression (2) is exceeded, the refractive power of the first sub-unit SL1 becomes strong, which is advantageous for reducing the overall lens length, but the angle of incidence of marginal rays among on-axis rays onto the second sub-unit SL2 having the vibration reduction mechanism becomes large. As a result, optical performance during image blur correction is likely to deteriorate.

[0040] Conditional formula (3) defines the ratio between the focal length f22p of the second sub-unit SL2 and the focal length f23n of the third sub-unit SL3. Mainly within the rear unit LP, the third sub-unit SL3 with negative refractive power is located on the image side of the second sub-unit SL2 with positive refractive power and equipped with an image stabilization mechanism, and by optimizing its focal length, it is possible to achieve both a reduction in the amount of movement of the image stabilization mechanism and good optical performance.

[0041] Exceeding the upper limit of conditional expression (3) undesirably weakens the refractive power of the second sub-unit SL2, which has an image stabilization mechanism, and increases the amount of movement of the second sub-unit SL2 during image blur correction. Exceeding the lower limit of conditional expression (3) undesirably strengthens the refractive power of the third sub-unit SL3, which is advantageous for reducing the overall lens length, but causes off-axial rays to diverge significantly, resulting in an increase in the effective diameter of the sub-units on the image side of the third sub-unit SL3.

[0042] Conditional expression (4) defines the ratio of the focal length f22p of the second sub-unit SL2 to the combined focal length f2w of the first to third sub-units SL1 to SL3 at the wide-angle end. By optimizing the focal length of the second sub-unit SL2, it is possible to suppress the amount of movement during image shake correction while also achieving good optical performance.

[0043] If the upper limit of conditional expression (4) is exceeded, the refractive power of the second sub-unit SL2 will be weakened, which is advantageous for suppressing the occurrence of various aberrations, but this is undesirable because the amount of movement of the second sub-unit SL2 during image blur correction will increase.If the lower limit of conditional expression (4) is exceeded, the refractive power of the second sub-unit SL2 will be strong, which will make it possible to suppress the amount of movement of the second sub-unit SL2 during image blur correction, but this will result in an increase in spherical aberration.

[0044] Conditional expression (5) defines the ratio of the focal length f23n of the third sub-unit SL3 to the combined focal length f2w of the first to third sub-units SL1 to SL3 at the wide-angle end. By optimizing the focal length of the third sub-unit SL3, it is possible to suppress the amount of movement during image shake correction while also achieving good optical performance.

[0045] If the upper limit of conditional expression (5) is exceeded, the refractive power of the third sub-group SL3 becomes strong, the refractive power of the second sub-group SL2 can be optimized, and the amount of movement of the second sub-group SL2 can be reduced, but this is undesirable because it leads to deterioration of optical performance due to the occurrence of field curvature and distortion aberrations caused mainly by off-axial rays.If the lower limit of conditional expression (5) is exceeded, the refractive power of the third sub-group SL3 becomes weak, and the occurrence of field curvature and distortion aberrations caused mainly by off-axial rays can be reduced, but it becomes difficult to optimize the refractive power of the second sub-group SL2, and the amount of movement of the second sub-group SL2 during image shake correction increases, which is undesirable.

[0046] Conditional expression (6) defines the ratio of the distance dw from the aperture stop SP at the wide-angle end to the vertex of the object side surface of the second subunit SL2 to the total optical length Lw of the entire system at the wide-angle end.

[0047] If the upper limit of conditional expression (6) is exceeded, the distance between the aperture stop SP and the second sub-unit SL2 becomes long, and the on-axis marginal rays become high, which undesirably leads to a deterioration in optical performance during image blur correction.If the lower limit of conditional expression (6) is exceeded, the distance between the aperture stop SP and the second sub-unit SL2 becomes short, which undesirably makes it difficult to arrange an image blur prevention mechanism.

[0048] Condition (7) defines the shape factor (lens shape) of the third subgroup SL3.

[0049] If the upper limit of conditional expression (7) is exceeded, the refractive power of the third sub-group SL3 becomes too strong, making it difficult to correct field curvature and distortion aberrations that occur mainly due to off-axial rays, which is undesirable.If the lower limit of conditional expression (7) is exceeded, the refractive power of the third sub-group SL3 becomes too weak, making it difficult to optimize the refractive power of the second sub-group SL2, and the amount of movement of the second sub-group SL2 during image shake correction increases, which is undesirable.

[0050] It is preferable to set the numerical ranges of the conditional expressions (1) to (7) as follows:

[0051] 1.3<(1-β22)×β22r<2.7 (1a) 0.7 <f21p / f22p<1.7 ···(2a) -1.4 <f22p / f23n<-0.6 ···(3a) 0.7 <f22p / f2w<1.7 ···(4a) -1.8 <f23n / f2w<-0.8 ···(5a) 0.015<|dw / Lw|<0.080 ···(6a) -7.0<(rn1+rn2) / (rn1-rn2)<-2.5 (7a) It is more preferable to set the numerical ranges of the conditions (1a) to (7a) as follows:

[0052] 1.4<(1-β22)×β22r<2.6 (1b) 0.75 <f21p / f22p<1.60 ···(2b) -1.30 <f22p / f23n<-0.75 ···(3b) 0.90 <f22p / f2w<1.55 ···(4b) -1.7 <f23n / f2w<-0.9 ···(5b) 0.018<|dw / Lw|<0.070 ···(6b) -6.3<(rn1+rn2) / (rn1-rn2)<-3.0 (7b) It is desirable for the front lens unit LN to move in the direction of the optical axis during zooming, which allows the overall lens length to be reduced at the wide-angle end or at the intermediate zoom position.

[0053] It is desirable for the front lens unit LN to have at least one negative lens and at least one positive lens, which makes it possible to correct chromatic aberration of magnification at the wide-angle end and optimize distortion.

[0054] It is desirable that the first sub-unit SL1 in the rear group LP has at least one positive lens and at least one negative lens, which makes it possible to correct axial chromatic aberration while increasing the refractive index of the first sub-unit SL1.

[0055] The third sub-group SL3 is preferably made up of a single lens having negative refractive power, which makes it possible to shorten the overall lens length while suppressing various aberrations that occur mainly due to off-axis rays.

[0056] It is desirable that the fourth sub-group SL4 has positive refractive power and that some or all of the lenses in the fourth sub-group SL4 move in the optical axis direction during focusing, which makes it possible to more effectively suppress aberration fluctuations during focusing.

[0057] Numerical Examples 1 to 5 corresponding to Examples 1 to 5, respectively, are shown below.

[0058] In the surface data of each numerical example, ri is the radius of curvature of the ith surface, counting from the object side; di (mm) is the axial distance (distance on the optical axis) between the ith and (i+1)th surfaces, counting from the object side; and ndi is the refractive index of the material of the ith optical element, counting from the object side, at the d-line. νdi is the Abbe number of the material of the ith optical element, counting from the object side. The Abbe number νd of a material is expressed as νd = (Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the Fraunhofer d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm).

[0059] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values when the optical system of each example is focused on an object at infinity. "Back focus" 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 length 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.

[0060] 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.

[0061] (Numerical Example 1) Unit: mm Surface Data Surface number rd nd νd 1 123.708 1.20 1.83481 42.7 2 21.374 5.46 3 120.122 1.20 1.60311 60.6 4 34.846 0.78 5 26.625 3.00 1.92286 20.9 6 40.918 (variable) 7 49.621 2.14 1.77250 49.6 8 -159.258 0.50 9 13.760 4.50 1.49700 81.5 10 -134.994 1.00 1.78590 44.2 11 23.310 6.69 12 (Aperture) ∞ (Variable) 13 19.343 1.04 1.74077 27.8 14 12.179 4.75 1.51742 52.4 15 -93.662 (variable) 16 -11.456 1.20 1.96300 24.1 17 -17.629 (variable) 18 -98.079 4.12 1.80000 29.8 19 -20.057 (variable) 20* -19.075 2.50 1.53110 55.9 21* -19.677 2.86 22 -17.003 2.00 1.88300 40.8 23 -44.739 (variable) Image plane ∞ Aspheric data Page 20 K=0.00000e+000 A4=4.20157e-006 A6=5.72660e-007 A8=-6.94053e-010 Page 21 K=0.00000e+000 A4=6.01118e-006 A6=4.23733e-007 Various data Zoom ratio 2.74 Wide-angle Mid-range Telephoto Focal length 24.86 38.85 68.13 F-number 4.12 5.10 7.31 Angle of view 38.31 29.11 17.62 Image height 19.64 21.64 21.64 Lens length 102.91 97.95 104.95 BF 13.00 22.13 37.46 d6 30.06 14.38 1.41 d12 3.72 3.72 3.72 d15 4.00 4.00 4.00 d17 5.68 4.71 4.51 d19 1.50 4.07 8.90 d23 13.00 22.13 37.46 Zoom lens group data Group starting plane focal length 1 1 -31.10 2 7 36.27 3 13 39.34 4 16 -37.56 5 18 30.79 June 20 -31.13 (Numerical Example 2) Unit: mm Surface Data Surface number rd nd νd 1 108.586 1.20 1.80400 46.6 2 21.327 5.86 3 169.244 1.20 1.51633 64.1 4 28.330 0.50 5 24.780 3.42 1.85478 24.8 6 40.442 (variable) 7 74.376 2.00 1.51633 64.1 8 -73.781 0.51 9 14.459 4.50 1.49700 81.5 10 -60.889 1.00 1.81600 46.6 11 51.262 6.01 12 (Aperture) ∞ (Variable) 13 25.706 2.45 1.48749 70.2 14 -67.886 (variable) 15 -12.288 1.20 1.84666 23.8 16 -24.422 (variable) 17 -128.155 4.27 1.77047 29.7 18 -21.345 (variable) 19* -18.859 2.50 1.53110 55.9 20* -19.913 2.89 21 -16.231 2.00 1.88300 40.8 22 -36.115 (variable) Image plane ∞ Aspheric data Page 19 K=0.00000e+000 A4=-1.96892e-005 A6=5.89993e-007 A8=-4.51652e-010 Page 20 K=0.00000e+000 A4=-1.91709e-005 A6=4.20764e-007 Various data Zoom ratio 2.77 Wide-angle Mid-range Telephoto Focal length 24.60 37.07 68.20 F-number 4.12 5.06 7.31 Angle of view 38.60 30.27 17.60 Image height 19.64 21.64 21.64 Lens length 103.78 98.47 104.49 BF 13.00 21.01 35.63 d6 31.23 16.31 1.43 d12 6.29 6.29 6.29 d14 4.00 4.00 4.00 d16 6.24 5.27 5.08 d18 1.50 4.08 10.55 d22 13.00 21.01 35.63 Zoom lens group data Group starting plane focal length 1 1 -31.00 2 7 33.01 3 13 38.58 4 15 -30.60 5 17 32.67 6 19 -33.19 (Numerical Example 3) Unit: mm Surface Data Surface number rd nd νd 1 1336.663 1.30 1.77250 49.6 2 20.570 1.41 3* 28.036 1.50 1.58313 59.4 4* 21.838 2.53 5 23.042 4.46 2.00100 29.1 6 37.777 (variable) 7* 12.861 4.00 1.58313 59.4 8* 12.683 2.14 9 14.404 7.00 1.49700 81.5 10 -15.409 1.00 1.61340 44.3 11 70.334 2.00 12 (Aperture) ∞ (Variable) 13 28.878 1.04 1.96300 24.1 14 16.340 3.00 1.80100 35.0 15 430.130 (variable) 16 -9.734 1.20 1.62041 60.3 17 -15.681 (variable) 18 -137.087 4.74 1.87070 40.7 19 -25.226 3.19 20 -22.989 2.00 1.85478 24.8 21 -68.069 1.20 22 -295.419 2.50 1.92286 20.9 23 -92.087 (variable) Image plane ∞ Aspheric data 3rd page K=0.00000e+000 A4=5.21412e-005 A6=-2.20073e-007 A8=5.43077e-010 Side 4 K=0.00000e+000 A4=4.72381e-005 A6=-2.55452e-007 A8=5.94739e-010 Side 7 K=0.00000e+000 A4=-1.55805e-005 A6=-5.36694e-008 A8=-1.62591e-010 Side 8 K=0.00000e+000 A4=-7.68425e-007 A6=-3.05208e-008 A8=1.00578e-009 Various data Zoom ratio 2.35 Wide-angle Mid-range Telephoto Focal length 28.68 42.81 67.45 F-number 4.12 5.25 7.16 Angle of view 34.41 26.81 17.78 Image height 19.64 21.64 21.64 Lens length 105.26 102.53 115.51 BF 13.00 20.64 36.88 d6 29.19 13.69 1.44 d12 2.00 2.00 2.00 d15 7.64 7.64 7.64 d17 7.24 12.37 21.36 d23 13.00 20.64 36.88 Zoom lens group data Group starting plane focal length 1 1 -43.14 2 7 42.73 3 13 45.77 4 16 -44.83 5 18 80.93 (Numerical Example 4) Unit: mm Surface Data Surface number rd nd νd 1 120.883 1.20 1.77250 49.6 2 21.592 5.17 3 122.600 1.20 1.60311 60.6 4 26.671 0.64 5 24.605 3.37 1.85478 24.8 6 41.898 (variable) 7 52.842 1.93 1.72916 54.7 8 -119.758 0.84 9 15.021 4.50 1.49700 81.5 10 -119.427 1.00 1.85150 40.8 11 30.787 4.89 12 (Aperture) ∞ (Variable) 13 28.451 1.04 1.72047 34.7 14 12.857 3.46 1.63854 55.4 15 -174.840 (variable) 16 -11.274 1.20 2.00100 29.1 17 -15.540 (variable) 18 -104.670 3.91 1.72825 28.5 19 -21.550 (variable) 20* -29.913 2.50 1.53110 55.9 21* -28.530 3.33 22 -18.626 2.00 1.95375 32.3 23 -46.003 (variable) Image plane ∞ Aspheric data Page 20 K=0.00000e+000 A4=-5.61900e-006 A6=3.75750e-007 A8=-3.79977e-010 Page 21 K=0.00000e+000 A4=-3.66808e-006 A6=3.08570e-007 Various data Zoom ratio 2.77 Wide-angle Mid-range Telephoto Focal length 24.50 39.36 67.92 F-number 4.12 5.17 7.31 Angle of view 38.72 28.80 17.67 Image height 19.64 21.64 21.64 Lens length 100.87 96.84 103.49 BF 13.00 19.58 32.75 d6 28.68 12.85 1.70 d12 5.44 5.50 3.37 d15 6.26 6.99 9.15 d17 3.81 5.01 5.57 d19 1.50 4.74 8.77 d23 13.00 19.58 32.75 Zoom lens group data Group starting plane focal length 1 1 -30.23 2 7 36.12 3 13 44.45 4 16 -47.74 5 18 36.54 6 20 -34.81 (Numerical Example 5) Unit: mm Surface Data Surface number rd nd νd 1 161.056 1.20 1.77250 49.6 2 21.356 5.11 3 78.020 1.20 1.78800 47.4 4 30.696 1.11 5 26.430 4.03 1.85478 24.8 6 56.461 (variable) 7 36.811 2.04 1.74320 49.3 8 -991.629 0.50 9 13.277 4.50 1.49700 81.5 10 -148.848 1.00 1.80400 46.6 11 17.826 5.13 12 (Aperture) ∞ (Variable) 13 22.846 1.04 1.80518 25.4 14 12.936 4.28 1.63854 55.4 15 -73.785 (variable) 16 -11.221 1.20 1.90043 37.4 17 -16.862 (variable) 18 -85.938 3.77 1.70585 30.2 19 -19.442 (variable) 20* -27.738 2.50 1.53110 55.9 21* -23.379 5.61 22 -20.950 2.00 1.88300 40.8 23 -119.884 (variable) Image plane ∞ Aspheric data Page 20 K=0.00000e+000 A4=6.95149e-005 A6=6.67973e-007 A8=-1.48716e-009 Page 21 K=0.00000e+000 A4=7.78983e-005 A6=6.15996e-007 Various data Zoom ratio 2.78 Wide-angle Mid-range Telephoto Focal length 24.56 39.58 68.24 F-number 4.12 5.34 7.31 Angle of view 38.66 28.66 17.59 Image height 19.64 21.64 21.64 Lens length 102.04 98.69 105.78 BF 13.00 23.10 38.31 d6 28.77 13.92 1.43 d12 4.42 4.42 4.42 d15 4.96 5.64 6.57 d17 3.10 3.88 4.93 d19 1.57 1.50 3.90 d23 13.00 23.10 38.31 Zoom lens group data Group starting plane focal length 1 1 -34.65 2 7 47.62 3 13 32.69 4 16 -41.43 5 18 34.78 6 20 -32.83 The various values in each numerical example are summarized in Table 1 below.

[0062] [Table 1]

[0063] [Imaging device] Next, an embodiment of a digital still camera (imaging device) using the optical system of the present invention as an imaging optical system will be described with reference to Fig. 16. In Fig. 16, 10 denotes a camera body, and 11 denotes an imaging optical system configured using any of the optical systems described in Examples 1 to 5. 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 the imaging optical system 11. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror.

[0064] In this way, by applying the optical system of the present invention to an imaging device such as a digital still camera, an imaging device with a small lens can be obtained.

[0065] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0066] LN front group LP rear group SL1 1st subgroup SL2 2nd subgroup SL3 3rd subgroup

Claims

1. A zoom lens comprising, arranged in order from the object side to the image side, a front group having negative refractive power and a rear group having positive refractive power as a whole, the rear group includes, arranged in order from the object side to the image side, a first subgroup having positive refractive power, a second subgroup having positive refractive power, a third subgroup having negative refractive power, and a fourth subgroup; The distance between the front group and the rear group changes during zooming, a distance between the third subgroup and the fourth subgroup changes during at least one of zooming and focusing; the first partial group, the third partial group, and the fourth partial group are stationary during image blur correction, a second lens subgroup including a cemented lens formed by cementing a positive lens and a negative lens, the second lens subgroup moving during image blur correction so as to have a component perpendicular to the optical axis;

2. When the lateral magnification of the second sub-group at the telephoto end is β22t and the lateral magnification of all lenses on the image side of the second sub-group at the telephoto end is β22rt, 1.0<(1-β22t)×β22rt<3.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

3. When the focal length of the first subgroup is f21p and the focal length of the second subgroup is f22p, 0.5<f21p / f22p<2.0 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. When the focal length of the second subgroup is f22p and the focal length of the third subgroup is f23n, -1.5<f22p / f23n<-0.5 4. The zoom lens according to claim 1, wherein the following condition is satisfied:

5. When the focal length of the second sub-group is f22p and the composite focal length of the first sub-group to the third sub-group at the wide-angle end is f2w, 0.5<f22p / f2w<2.0 5. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. When the focal length of the third partial group is f23n and the composite focal length from the first partial group to the third partial group at the wide-angle end is f2w, -2.0<f23n / f2w<-0.5 6. The zoom lens according to claim 1, wherein the following condition is satisfied:

7. further comprising a diaphragm disposed between the first subgroup and the second subgroup; When the distance from the stop to the object-side vertex of the second subgroup at the wide-angle end is dw and the total optical length of the entire system at the wide-angle end is Lw, 0.01<|dw / Lw|<0.10 7. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. When the radius of curvature of the lens surface closest to the object side in the third sub-unit is rn1 and the radius of curvature of the lens surface closest to the image side in the third sub-unit is rn2, -8.0<(rn1+rn2) / (rn1-rn2)<-2.0 8. The zoom lens according to claim 1, wherein the following condition is satisfied:

9. the fourth subgroup has a positive refractive power, 9. The zoom lens according to claim 1, wherein some or all of the lenses in the fourth subgroup move during focusing.

10. 10. The zoom lens according to claim 1, wherein the front group moves during zooming.

11. 11. The zoom lens according to claim 1, wherein the front group comprises a negative lens and a positive lens.

12. 12. The zoom lens according to claim 1, wherein the first sub-group includes a positive lens and a negative lens.

13. 13. The zoom lens according to claim 1, wherein the third sub-group is made up of a single lens having negative refractive power.

14. 14. The zoom lens according to claim 1, wherein the rear group is made up of the first subgroup, the second subgroup, the third subgroup, and the fourth subgroup.

15. the rear group includes the first subgroup, the second subgroup, the third subgroup, the fourth subgroup, and a fifth subgroup arranged on the image side of the fourth subgroup, 14. The zoom lens according to claim 1, wherein the distance between the fourth and fifth subgroups changes during zooming.

16. 16. The zoom lens according to claim 15, wherein the fifth subgroup has negative refractive power.

17. a zoom lens according to any one of claims 1 to 16; and an image sensor that receives an image formed by the zoom lens.

Images