Zoom lens and imaging device having the same

Abstract

To provide a zoom lens that has a high optical performance over an entire zoom range and is compact and light-weighted.SOLUTION: A zoom lens (1a) has 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 fourth lens group (L4) with positive refractive power, which are arranged in this order from an object side to an image side. In zooming from a wide angle end to a telephoto end, the first lens group moves, the second lens group does not move, an interval between the first lens group and the second lens group is increased, an interval between the second lens group and the third lens group is reduced, and an interval between the third lens group and the fourth lens group is reduced. The first lens group has a positive lens and a negative lens. The second lens group is composed of two or less lenses. The third lens group is composed of two or less lenses. The fourth lens group is two or less lenses.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 suitable for imaging devices using solid-state imaging elements such as digital still cameras, video cameras, broadcast cameras, and surveillance cameras, or imaging devices such as cameras using silver halide photographic film. [Background technology]

[0002] In recent years, zoom lenses used in imaging devices are required to have high optical performance, and to be small and lightweight. As a zoom lens that meets these requirements, Patent Document 1 discloses a zoom lens in which the spacing between adjacent lens groups changes during zooming with positive, negative, positive, and positive refractive powers in that order from the object side to the image side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-43607 A Summary of the Invention [Problem to be solved by the invention]

[0004] In general, in order to reduce the size of a zoom lens, it is effective to adopt a telephoto type power arrangement at the telephoto end and to strengthen the positive refractive power on the object side and the negative refractive power on the image side. However, if the refractive power of each lens group is strengthened, the fluctuation of various aberrations accompanying zooming becomes large, and it becomes difficult to satisfactorily correct various aberrations with a small number of lenses. Therefore, in order to obtain high optical performance over the entire zoom range while reducing the size and weight of the entire zoom lens system, it is important to appropriately set each element constituting the zoom lens. For example, it is important to appropriately set the number of lens groups, the movement conditions during zooming, and the lens configuration of each lens group.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a small, lightweight zoom lens and an image pickup apparatus that have high optical performance over the entire zoom range. [Means for solving the problem]

[0006] A zoom lens according to one aspect of the present invention includes, arranged in order from an object side to an 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 fourth lens group having a positive refractive power. , the fifth lens group, having A zoom lens in which 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 and the second lens group remains stationary, 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 the distance between the third lens group and the fourth lens group decreases, the first lens group has a positive lens and a negative lens, the second lens group is composed of two or less lenses, the third lens group is composed of two or less lenses, and the fourth lens group is composed of two or less lenses.

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

[0008] According to the present invention, it is possible to provide a small, lightweight zoom lens and an imaging device that have high optical performance over the entire zoom range. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a zoom lens at a wide-angle end in a first embodiment. [Diagram 2] 4A to 4C are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens in Example 1. [Diagram 3] FIG. 11 is a cross-sectional view of a zoom lens at a wide-angle end in a second embodiment. [Figure 4] 8A to 8C are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens in Example 2. [Diagram 5]FIG. 11 is a cross-sectional view of a zoom lens at a wide-angle end in a third embodiment. [Figure 6] 11A to 11C are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens in Example 3. [Figure 7] FIG. 11 is a cross-sectional view of a zoom lens at a wide-angle end in a fourth embodiment. [Figure 8] 11A to 11C are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens in Example 4. [Figure 9] FIG. 13 is a cross-sectional view of a zoom lens at a wide-angle end in a fifth embodiment. [Figure 10] 13A to 13C are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens in Example 5. [Figure 11] FIG. 13 is a cross-sectional view of a zoom lens at a wide-angle end in a sixth embodiment. [Figure 12] 13A to 13C are longitudinal aberration diagrams at the wide-angle end and the telephoto end of the zoom lens in Example 6. [Figure 13] FIG. 13 is a schematic diagram of an imaging device according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0011] 1, 3, 5, 7, 9, and 11 are cross-sectional views of zoom lenses (optical systems) 1a to 1f of Examples 1 to 6, respectively, when focused on infinity (infinity focused state). The zoom lenses of the respective Examples are used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide cameras, and surveillance cameras, as well as optical devices including interchangeable lenses.

[0012] In each cross-sectional view, the left side is the object side and the right side is the image side. The zoom lens of each embodiment is composed of multiple lens groups. In each embodiment, the lens group is a group of lenses that move together or are stationary during zooming. In the zoom lens of each embodiment, the interval between adjacent lens groups changes when the lens is zoomed from the wide-angle end to the telephoto end. The wide-angle end and the telephoto end are zoom states when the lens group that moves during zooming is located at both ends of the range in which it can move mechanically in the direction along the optical axis OA (optical axis direction). The lens group may be composed of one lens or multiple lenses. The lens group may also include an aperture stop.

[0013] In each cross-sectional view, i (a natural number) indicates the order counted from the object side, and Li indicates the i-th lens group. SP is an aperture stop. IP is an image plane, and when the zoom lenses 1a to 1f of each embodiment are used as an imaging optical system for a digital video camera or digital still camera, the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is disposed on the image plane IP. When the optical systems 1a to 1f of each embodiment are used as an imaging optical system for a silver halide film camera, the photosensitive surface of the film is disposed on the image plane IP.

[0014] In the zoom lenses 1a to 1f of the respective embodiments, when zooming from the wide-angle end to the telephoto end, each lens group moves as shown by the solid arrow in each cross-sectional view, and when focusing from infinity to a close distance, each lens group moves as shown by the dotted arrow.

[0015] 2, 4, 6, 8, 10, and 12 are longitudinal aberration diagrams of the zoom lenses 1a to 1f of Examples 1 to 6, respectively. In each aberration diagram, (A) shows the longitudinal aberration diagram at the wide-angle end and in a state where the lens is focused at infinity, and (B) shows the longitudinal aberration diagram at the telephoto end and in a state where the lens is focused at infinity.

[0016] In the spherical aberration diagram, Fno is the F-number, and the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm) is shown by a solid line and a two-dot chain line, respectively. In the astigmatism diagram, ΔS indicates the amount of astigmatism on the sagittal image plane (solid line), and ΔM indicates the amount of astigmatism on the meridional image plane (dashed line). In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration at the g-line is shown. ω is the half angle of view (°).

[0017] Next, the characteristic configuration and conditions of the zoom lens of each embodiment will be described. The zoom lens of each embodiment has, 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 fourth lens group L4 with positive refractive power. During zooming from the wide-angle end to the telephoto end, the first lens group L1 moves, the distance between the first lens group L1 and the second lens group L2 increases, the distance between the second lens group L2 and the third lens group L3 decreases, and the distance between the third lens group L3 and the fourth lens group L4 decreases. This results in a telephoto type power arrangement at the telephoto end, which makes it easy to shorten the total optical length (the distance from the most object-side surface to the image surface IP). In addition, the negative second lens group L2 does not move during zooming (it is fixed in the optical axis direction). This reduces the amount of relative decentering error between the first lens group L1 and the second lens group L2, thereby reducing performance degradation. Note that in each embodiment, the second lens group L2 may be a vibration-proof lens group that is movable in a direction intersecting the optical axis OA.

[0018] The first lens group L1 has a positive lens and a negative lens. This suppresses the occurrence of chromatic aberration when zooming from the wide-angle end to the telephoto end. The second lens group L2 is composed of two or less lenses. This reduces the weight of the second lens group L2, and when the second lens group L2 is used as an image stabilization lens group, it is easy to reduce the size of the drive mechanism. The third lens group L3 and the fourth lens group L4 each consist of two or less lenses. This reduces the weight of the lens groups that move during zooming, allowing for quick zooming.

[0019] With the above-mentioned configuration, it is possible to obtain a small, lightweight zoom lens that has high optical performance over the entire zoom range.

[0020] It is preferable that the zoom lenses 1a to 1f of each embodiment have the following configuration: Since the amount of movement of the fourth lens group L4 becomes large during zooming from the wide-angle end to the telephoto end, in order to suppress fluctuations in various aberrations, it is preferable that the fourth lens group L4 includes at least one lens having an aspheric surface.

[0021] It is preferable to arrange a lens group with negative refractive power closer to the image side than the fourth lens group L4. This results in a telephoto type power arrangement, which makes it easy to shorten the overall optical length. It is preferable that the lens closer to the image side than the fourth lens group L4 is composed of four or less lenses. This reduces the weight of the lens group that moves during zooming, allowing for quick zooming.

[0022] The lens group on the image side of the aperture diaphragm SP tends to have a small effective diameter of the light beam. For this reason, if the lens group on the image side of the aperture diaphragm SP is used as the focus lens group, the holding mechanism and the drive mechanism can be simplified and the overall system can be made smaller. Furthermore, if the focus lens group is configured with two or fewer lenses, the focusing lens group can be made lighter. In addition, since the magnification change is relatively small on the image side of the aperture diaphragm SP, the change in image magnification can be made small when focusing from infinity to a close distance. This is particularly suitable for video shooting, since the change in the angle of view can be made small when the subject changes from infinity to a close distance.

[0023] By driving all or part of any of the lens groups in a direction perpendicular to the optical axis direction, it is possible to obtain the effect of reducing camera shake. In particular, by using the second lens group L2, which is fixed during zooming, as the camera shake correction lens group, it is possible to reduce the amount of movement of the camera shake correction lens group, which is preferable since it facilitates size reduction.

[0024] It is preferable that the zoom lenses 1a to 1f of each of the embodiments satisfy at least one of the following conditional expressions (1) to (12).

[0025] 0.10 <TLt / ft<0.80 …(1) 1.40 <ndL4ave<1.70 …(2) -0.30 <fL2 / ft<-0.10 …(3) 0.15 <fL3 / ft<0.90 …(4) 0.30 <ML4 / ML1<3.00 …(5) -0.80 <fL2 / fL1<-0.20 …(6) 0.05 <fL4 / ft<0.50 …(7) 0.10 <fL4 / fL1<0.70 …(8) 0.05 <fL4 / fL3<1.00 …(9) 0.90 <SL4ave<2.80 …(10) 55<νdL1Pave<99 …(11) 55<νdL3Pave<99 …(12) Conditional formula (1) specifies the conditions for the total optical length TLt at the telephoto end (the distance from the side closest to the object to the image plane IP) and the focal length ft of the entire zoom lens system at the telephoto end. By appropriately setting these conditions, it becomes easier to make the zoom lens compact. If the lower limit of conditional formula (1) is exceeded, the total optical length at the telephoto end becomes too short relative to the focal length of the entire system at the telephoto end, the refractive power of each lens group becomes strong, and it becomes difficult to suppress the fluctuation of various aberrations accompanying zooming, which is undesirable. On the other hand, if the upper limit of conditional formula (1) is exceeded, the total optical length at the telephoto end becomes too long relative to the focal length of the entire zoom lens system at the telephoto end, which is undesirable, as it becomes difficult to make the zoom lens compact.

[0026] Conditional formula (2) specifies the condition regarding the average refractive index ndL4ave of the fourth lens group L4. Generally, as the refractive index of the lens material increases, the specific gravity of the lens material increases. If the lower limit of conditional formula (2) is exceeded, the curvature of the lens surface becomes strong in order to obtain the necessary refractive power, which is undesirable because it becomes difficult to suppress the fluctuation of various aberrations such as spherical aberration and curvature of field that accompany zooming. On the other hand, if the upper limit of conditional formula (2) is exceeded, the specific gravity of the lens becomes large, which is undesirable because it becomes difficult to reduce the weight.

[0027] Conditional expression (3) specifies the conditions for the focal length ft of the entire zoom lens system at the telephoto end and the focal length fL2 of the second lens group L2. If the lower limit of conditional expression (3) is exceeded, the focal length fL2 becomes too short, making it difficult to suppress the fluctuations in various aberrations such as spherical aberration and curvature of field that accompany zooming, which is undesirable. On the other hand, if the upper limit of conditional expression (3) is exceeded, the focal length ft of the entire system at the telephoto end becomes too short, making it difficult to achieve a high zoom ratio, which is undesirable.

[0028] Conditional expression (4) specifies the conditions for the focal length ft of the entire zoom lens system at the telephoto end and the focal length fL3 of the third lens group L3. If the lower limit of conditional expression (4) is exceeded, the focal length fL3 becomes too short, making it difficult to suppress the fluctuations in various aberrations such as spherical aberration and curvature of field that accompany zooming, which is undesirable. On the other hand, if the upper limit of conditional expression (4) is exceeded, the focal length ft of the entire system at the telephoto end becomes too short, making it difficult to achieve a high zoom ratio, which is undesirable.

[0029] Conditional formula (5) specifies the condition regarding the amount of movement ML1 of the first lens group L1 from the object side to the image side (the amount of movement from the object side to the image side is positive) and the amount of movement ML4 of the fourth lens group L4 from the object side to the image side (the amount of movement from the object side to the image side is positive) during zooming from the wide-angle end to the telephoto end. If the lower limit of conditional formula (5) is exceeded, the amount of movement ML4 of the fourth lens group L4 becomes small, which is undesirable as it becomes difficult to achieve a high zoom ratio. On the other hand, if the upper limit of conditional formula (5) is exceeded, the amount of movement ML4 of the fourth lens group L4 becomes large, which is undesirable as it becomes difficult to achieve a compact size.

[0030] Conditional formula (6) specifies the conditions for the focal length fL1 of the first lens group L1 and the focal length fL2 of the second lens group L2. If the lower limit of conditional formula (6) is exceeded, the focal length fL1 of the first lens group L1 becomes long, the amount of movement of the first lens group L1 during zooming from the wide-angle end to the telephoto end becomes large, and it becomes difficult to reduce the size of the zoom lens, which is undesirable. On the other hand, if the upper limit of conditional formula (6) is exceeded, the focal length fL1 of the first lens group L1 becomes short, and it becomes difficult to correct the spherical aberration generated in the first lens group L1, which is undesirable.

[0031] Conditional expression (7) specifies the conditions for the focal length ft of the entire zoom lens system at the telephoto end and the focal length fL4 of the fourth lens group L4. If the lower limit of conditional expression (7) is exceeded, the focal length fL4 becomes too short, making it difficult to suppress the fluctuations in various aberrations such as spherical aberration and curvature of field that accompany zooming, which is undesirable. On the other hand, if the upper limit of conditional expression (7) is exceeded, the focal length ft of the entire zoom lens system at the telephoto end becomes too short, making it difficult to achieve a high zoom ratio, which is undesirable.

[0032] Conditional expression (8) specifies the conditions related to the focal length fL1 of the first lens group L1 and the focal length fL4 of the fourth lens group L4. If the lower limit of conditional expression (8) is not satisfied, the focal length fL4 becomes short, making it difficult to suppress the fluctuation of various aberrations such as spherical aberration and curvature of field during zooming, which is undesirable. On the other hand, if the upper limit of conditional expression (8) is exceeded, the focal length fL4 of the fourth lens group L4 becomes long, the refractive power of the fourth lens group L4 becomes weak, and the amount of movement of the fourth lens group L4 during zooming becomes long, which is undesirable.

[0033] Conditional expression (9) specifies the conditions related to the focal length fL3 of the third lens group L3 and the focal length fL4 of the fourth lens group L4. If the lower limit of conditional expression (9) is not satisfied, the focal length fL4 becomes short, making it difficult to suppress the fluctuation of various aberrations such as spherical aberration and curvature of field during zooming, which is undesirable. On the other hand, if the upper limit of conditional expression (9) is exceeded, the focal length fL4 of the fourth lens group L4 becomes long, the refractive power of the fourth lens group L4 becomes weak, and the amount of movement of the fourth lens group L4 during zooming becomes long, which is undesirable.

[0034] Conditional formula (10) specifies the condition regarding the average specific gravity SL4ave of the lenses constituting the fourth lens group L4. In general, as the specific gravity of the lens material increases, the refractive index of the lens material increases. If the lower limit of conditional formula (10) is exceeded, the curvature of the lens surface becomes strong in order to obtain the necessary refractive power, which is undesirable because it becomes difficult to suppress fluctuations in various aberrations such as spherical aberration and curvature of field that accompany zooming. On the other hand, if the upper limit of conditional formula (10) is exceeded, the specific gravity of the lens becomes large, which is undesirable because it becomes difficult to reduce the weight.

[0035] Conditional expression (11) is a condition regarding the average Abbe number νdL1Pave for the d-line of the positive lenses included in the first lens group L1. If the lower limit of conditional expression (11) is exceeded, it becomes difficult to correct the axial chromatic aberration and lateral chromatic aberration at the telephoto end, which is undesirable. On the other hand, if the upper limit of conditional expression (11) is exceeded, it becomes difficult to correct the lateral chromatic aberration at the wide-angle end, which is undesirable.

[0036] Conditional expression (12) is a condition regarding the average Abbe number νdL3Pave for the d-line of the positive lenses included in the third lens group L3. If the lower limit of conditional expression (12) is exceeded, it becomes difficult to correct axial chromatic aberration at the telephoto end, which is undesirable. On the other hand, if the upper limit of conditional expression (12) is exceeded, it becomes difficult to correct axial chromatic aberration at the wide-angle end, which is undesirable. In each embodiment, it is more preferable that the numerical ranges of the conditional expressions (1) to (12) be within the ranges of the following conditional expressions (1a) to (12a). 0.40 <TLt / ft<0.79 …(1a) 1.45 <ndL4ave<1.67 …(2a) -0.27 <fL2 / ft<-0.12 …(3a) 0.20 <fL3 / ft<0.85 …(4a) 0.40 <ML4 / ML1<2.50 …(5a) -0.70 <fL2 / fL1<-0.23 …(6a) 0.07 <fL4 / ft<0.40 …(7a) 0.15 <fL4 / fL1<0.60 …(8a) 0.10 <fL4 / fL3<0.90 …(9a) 0.95 <SL4ave<2.75 …(10a) 58<νdL1Pave<90 …(11a) 58<νdL3Pave<90 …(12a) It is even more preferable that the numerical ranges of the conditional expressions (1) to (12) be within the ranges of the following conditional expressions (1b) to (12b). 0.50 <TLt / ft<0.78 …(1b) 1.50 <ndL4ave<1.65 …(2b) -0.25 <fL2 / ft<-0.14 …(3b) 0.25 <fL3 / ft<0.80 …(4b) 0.50 <ML4 / ML1<2.30 …(5b) -0.60 <fL2 / fL1<-0.25 …(6b) 0.09 <fL4 / ft<0.30 …(7b) 0.20 <fL4 / fL1<0.50 …(8b) 0.15 <fL4 / fL3<0.80 …(9b) 1.00 <SL4ave<2.70 …(10b) 60<νdL1Pave<85 …(11b) 60<νdL3Pave<85 …(12b) Next, the zoom lens of each embodiment will be described in detail.

[0037] The zoom lens 1a of the first embodiment is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, and a fifth lens group L5 with negative refractive power. The first lens group L1 is composed of a lens (positive lens) L11, a lens (negative lens) L12, and a lens (positive lens) L13. The second lens group L2 is composed of lenses L21 and L22. The third lens group L3 is composed of an aperture stop SP and lenses L31 and L32. The fourth lens group L4 is composed of lenses L41 and L42. The fifth lens group L5 is composed of lenses L51 and L52. During zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, and the fifth lens group L5 move, and the second lens group L2 does not move. At this time, the distance between the first lens group L1 and the second lens group L2 and the distance between the fourth lens group L4 and the fifth lens group L5 increase, while the distance between the second lens group L2 and the third lens group L3 and the distance between the third lens group L3 and the fourth lens group L4 decrease. Both surfaces of the lens L42 in the fourth lens group L4 are aspheric. The fifth lens group L5 functions as a focus lens group.

[0038] The zoom lens 1b of the second embodiment is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, and a fifth lens group L5 with negative refractive power. The first lens group L1 is composed of lenses L11, L12, and L13. The second lens group L2 is composed of lenses L21 and L22. The third lens group L3 is composed of an aperture stop SP and lenses L31 and L32. The fourth lens group L4 is composed of lenses L41 and L42. The fifth lens group L5 is composed of lenses L51 and L52. During zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, and the fifth lens group L5 move, and the second lens group L2 does not move. At this time, the distance between the first lens group L1 and the second lens group L2 and the distance between the fourth lens group L4 and the fifth lens group L5 are increased, while the distance between the second lens group L2 and the third lens group L3 and the distance between the third lens group L3 and the fourth lens group L4 are decreased. Both surfaces of the lens L42 of the fourth lens group L4 are aspheric. The fifth lens group L5 functions as a focus lens group.

[0039] The zoom lens 1c of the third embodiment is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with positive refractive power, and a sixth lens group L6 with negative refractive power. The first lens group L1 is composed of lenses L11, L12, and L13. The second lens group L2 is composed of lenses L21 and L22. The third lens group L3 is composed of an aperture stop SP and lenses L31 and L32. The fourth lens group L4 is composed of lenses L41 and L42. The fifth lens group L5 is composed of lenses L51 and L52. The sixth lens group L6 is composed of lenses L61 and L62. During zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, the fifth lens group L5, and the sixth lens group L6 move, and the second lens group L2 does not move. During zooming, the distance between the first lens group L1 and the second lens group L2 and the distance between the fourth lens group L4 and the fifth lens group L5 each widens. During zooming, the distance between the second lens group L2 and the third lens group L3, the distance between the third lens group L3 and the fourth lens group L4, and the distance between the fifth lens group L5 and the sixth lens group L6 each narrows. Both surfaces of the lens L42 of the fourth lens group L4 are aspheric. Both surfaces of the lens L42 of the fourth lens group L4 are aspheric. The sixth lens group L6 functions as a focus lens group.

[0040] The zoom lens 1d of the fourth embodiment is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with negative refractive power, and a sixth lens group L6 with positive refractive power. The first lens group L1 is composed of lenses L11, L12, and L13. The second lens group L2 is composed of lenses L21 and L22. The third lens group L3 is composed of an aperture stop SP and lenses L31 and L32. The fourth lens group L4 is composed of lenses L41 and L42. The fifth lens group L5 is composed of lenses L51 and L52. The sixth lens group L6 is composed of a lens L61. During zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, the fifth lens group L5, and the sixth lens group L6 move, and the second lens group L2 does not move. During zooming, the distance between the first lens group L1 and the second lens group L2 and the distance between the fifth lens group L5 and the sixth lens group L6 each widens. During zooming, the distance between the second lens group L2 and the third lens group L3, the distance between the third lens group L3 and the fourth lens group L4, and the distance between the fourth lens group L4 and the fifth lens group L5 each narrows. Both surfaces of the lens L42 in the fourth lens group L4 are aspheric. The fifth lens group L5 functions as a focus lens group.

[0041] The zoom lens 1e of the fifth embodiment is composed of a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 with negative refractive power, and a sixth lens group L6 with negative refractive power. The first lens group L1 is composed of lenses L11, L12, and L13. The second lens group L2 is composed of lenses L21 and L22. The third lens group L3 is composed of an aperture stop SP and lenses L31 and L32. The fourth lens group L4 is composed of a lens L41. The fifth lens group L5 is composed of lenses L51 and L52. The sixth lens group L6 is composed of a lens L61. During zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, the fifth lens group L5, and the sixth lens group L6 move, and the second lens group L2 does not move. During zooming, the distance between the first lens group L1 and the second lens group L2 and the distance between the fifth lens group L5 and the sixth lens group L6 each increase. During zooming, the distance between the second lens group L2 and the third lens group L3, the distance between the third lens group L3 and the fourth lens group L4, and the distance between the fourth lens group L4 and the fifth lens group L5 each decrease. Both surfaces of the lens L41 in the fourth lens group L4 are aspheric. The fifth lens group L5 functions as a focus lens group.

[0042] The zoom lens 1f of the sixth embodiment is composed of a first lens group L1, a second lens group L2, a third lens group L3, a fourth lens group L4, a fifth lens group L5 with negative refractive power, a sixth lens group L6 with positive refractive power, and a seventh lens group L7 with negative refractive power. The first lens group L1 is composed of lenses L11, L12, and L13. The second lens group L2 is composed of lenses L21 and L22. The third lens group L3 is composed of an aperture stop SP and a lens L31. The fourth lens group L4 is composed of lenses L41 and L42. The fifth lens group L5 is composed of lenses L51 and L52. The sixth lens group L6 is composed of a lens L61. The seventh lens group L7 is composed of a lens L71. During zooming from the wide-angle end to the telephoto end, the first lens group L1, the third lens group L3, the fourth lens group L4, the fifth lens group L5, the sixth lens group L6, and the seventh lens group L7 move, and the second lens group L2 does not move. During zooming, the distance between the first lens group L1 and the second lens group L2 and the distance between the fifth lens group L5 and the sixth lens group L6 each widens. During zooming, the distance between the second lens group L2 and the third lens group L3, the distance between the third lens group L3 and the fourth lens group L4, the distance between the fourth lens group L4 and the fifth lens group L5, and the distance between the sixth lens group L6 and the seventh lens group L7 each narrows. Both surfaces of the lens L31 of the third lens group L3 are aspheric. Both surfaces of the lens L42 of the fourth lens group L4 are aspheric. The fifth lens group L5 functions as a focus lens group.

[0043] Numerical Examples 1 to 6 corresponding to Examples 1 to 6, respectively, are shown below. In each numerical example, each surface of the optical system is assigned a surface number i (i is a natural number) from the object side. r is the radius of curvature of each surface (mm), d is the lens thickness or distance (air gap) (mm) on the optical axis between the surface with surface number i and the surface with surface number (i+1), and nd is the refractive index for the d-line of the material of the optical member having each surface. νd is the Abbe number for the d-line of the material of the optical member having each surface. The Abbe number νd of a certain material is given by Nd, NF, and NC, respectively, when the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines are Nd, NF, and NC, respectively. νd=(Nd-1) / (NF-NC) It is expressed as:

[0044] The focal length (mm), F-number, and half angle of view (°) are values ​​when the optical system is focused on an object at infinity. The total lens length is the distance on the optical axis from the front surface (the lens surface closest to the object) to the last surface (the lens surface closest to the image) of the optical system, plus the back focus BF. The back focus BF is the distance from the last surface of the optical system to the image plane.

[0045] An "*" next to a surface number means that the surface has an aspheric shape. An aspheric shape is expressed by the following formula, where x is the displacement from the apex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, the direction of light travel is positive, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10, and A12 are aspheric coefficients. The aspheric coefficient "ex" is expressed by the following formula: -x means.

[0046] 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 Values ​​corresponding to the above-mentioned conditional expressions (1) to (12) in Numerical Examples 1 to 6 are summarized in Table 1.

[0047] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1 103.753 4.61 1.48749 70.2 2∞0.15 3 156.943 1.90 1.61340 44.3 4 53.406 5.96 1.49700 81.5 5 380.919 (variable) 6 -101.313 1.00 1.77250 49.6 7 28.984 2.85 2.05090 26.9 8 55.746 (variable) 9(Aperture) ∞ 0.60 10 29.396 5.49 1.48749 70.2 11 -59.441 5.76 12 -31.194 1.30 2.00100 29.1 13 -75.081 (variable) 14 415.256 3.50 1.48749 70.2 15 -30.719 6.37 16* 49.641 3.00 1.53110 55.9 17* 47.793 (variable) 18 -992.387 2.22 1.84666 23.9 19 -42.688 0.95 1.80400 46.5 20 39.970 (variable) Image plane ∞ Aspheric Data Page 16 K = 0.00000e+000 A 4=-4.71184e-005 A 6=-1.69647e-007 A 8= 6.47160e-010 A10=-6.68961e-012 A12= 3.22858e-014 Page 17 K = 0.00000e+000 A 4=-4.13756e-005 A 6=-1.60763e-007 A 8= 6.71955e-010 A10=-4.98484e-012 A12= 2.62649e-014 Various data Zoom ratio 3.87 Wide Angle Mid-Telephoto Focal length 100.31 200.00 388.00 F-number 5.77 7.17 8.24 Half angle of view 12.17 6.17 3.19 Image height 21.64 21.64 21.64 Lens length 182.61 225.42 258.53 BF 48.26 75.67 110.31 d 5 16.89 59.69 92.80 d 8 41.71 26.23 3.60 d13 11.14 6.27 4.09 d17 18.95 11.89 2.07 d20 48.26 75.67 110.31 Zoom lens group data Group starting plane focal length 1 1 192.87 2 6 -59.32 3 9 107.44 4 14 58.11 5 18 -50.03 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1 125.719 4.61 1.48749 70.2 2∞0.15 3 206.094 1.90 1.61340 44.3 4 61.613 5.96 1.49700 81.5 5 3311.719 (variable) 6 -94.238 1.00 1.77250 49.6 7 29.812 2.85 2.05090 26.9 8 59.746 (variable) 9(Aperture) ∞ 0.60 10 33.800 5.49 1.48749 70.2 11 -59.212 5.76 12 -33.313 1.30 2.00100 29.1 13 -79.764 (variable) 14 669.192 3.50 1.59282 68.6 15 -38.012 8.00 16* 31.365 3.00 1.53110 55.9 17* 27.194 (variable) 18 190.513 2.22 1.95906 17.5 19 -407.020 0.95 1.80400 46.5 20 42.702 (variable) Image plane ∞ Aspheric Data Page 16 K = 0.00000e+000 A 4=-3.77585e-005 A 6=-1.11836e-007 A 8= 2.47802e-010 A10=-1.60309e-012 A12= 7.41207e-015 Page 17 K = 0.00000e+000 A 4=-3.68964e-005 A 6=-1.27560e-007 A 8= 4.90571e-010 A10=-3.52309e-012 A12= 1.66624e-014 Various data Zoom ratio 3.50 Wide Angle Mid-Telephoto Focal length 100.00 187.74 350.00 F-number 5.77 7.05 8.24 Half angle of view 12.21 6.57 3.54 Image height 21.64 21.64 21.64 Lens length 191.90 234.71 267.82 BF 53.88 82.89 117.84 d 5 16.89 59.69 92.80 d 8 41.71 26.23 3.60 d13 11.14 6.27 4.09 d17 21.00 12.34 2.19 d20 53.88 82.89 117.84 Zoom lens group data Group starting plane focal length 1 1 207.37 2 6 -60.76 3 9 126.45 4 14 64.97 5 18 -75.45 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1 72.901 5.00 1.48749 70.2 2 -5116.308 0.15 3 96.485 1.90 1.80610 40.7 4 38.718 5.96 1.59410 60.5 5 151.108 (variable) 6 -138.145 1.00 1.75500 52.3 7 25.532 2.85 2.05090 26.9 8 44.316 (variable) 9(Aperture) ∞ 0.60 10 40.918 3.54 1.59410 60.5 11 -110.268 5.49 12 -40.305 1.30 2.00069 25.5 13 -86.998 (variable) 14 -32.977 2.71 1.59410 60.5 15 -19.917 0.36 16* -28.313 2.50 1.68040 18.1 17* -28.575 (variable) 18 43.490 1.00 1.84666 23.8 19 34.968 2.47 1.49700 81.5 20 73.461 (variable) 21 1108.890 3.10 1.92119 24.0 22 -60.469 0.95 1.83481 42.7 23 47.468 (variable) Image plane ∞ Aspheric Data Page 16 K = 0.00000e+000 A 4=-6.21812e-005 A 6=-6.99576e-008 A 8=-9.13103e-011 A10=-2.47166e-012 A12= 1.49716e-014 Page 17 K = 0.00000e+000 A 4=-4.63866e-005 A 6=-2.29469e-008 A 8=-7.19123e-011 A10=-7.36741e-013 A12= 5.69474e-015 Various data Zoom ratio 4.29 Wide Angle Mid-Telephoto Focal length 70.00 149.64 300.00 F-number 4.20 6.04 7.20 Half angle of view 17.17 8.23 ​​4.12 Image height 21.64 21.64 21.64 Lens length 170.19 199.65 232.45 BF 23.56 62.47 105.22 d 5 4.56 34.02 66.82 d 8 41.56 24.34 5.16 d13 19.67 11.78 3.01 d17 1.00 4.23 7.82 d20 38.95 21.92 3.52 d23 23.56 62.47 105.22 Zoom lens group data Group starting plane focal length 1 1 165.49 2 6 -57.39 3 9 120.57 4 14 77.38 5 18 334.80 6 21 -65.42 [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd 1 137.194 3.32 1.48749 70.2 2 556.213 0.15 3 169.321 1.90 1.61340 44.3 4 59.780 7.39 1.49700 81.5 5 -492.395 (variable) 6 -250.411 1.00 1.75500 52.3 7 25.858 2.85 2.05090 26.9 8 43.298 (variable) 9(Aperture) ∞ 0.60 10 31.879 4.94 1.49700 81.5 11 131.830 9.29 12 -30.439 1.30 2.00069 25.5 13 -43.792 (variable) 14 35.880 4.30 1.49700 81.5 15 -37.877 8.00 16* -26.275 2.50 1.68040 18.1 17* -29.773 (variable) 18 -176.955 2.56 2.00069 25.5 19 -29.993 0.95 1.83481 42.7 20 32.008 (variable) 21 44.117 4.00 1.48749 70.2 22 78.183 (variable) Image plane ∞ Aspheric Data Page 16 K = 0.00000e+000 A 4=-5.75946e-005 A 6= 5.33432e-008 A 8= 7.02179e-010 A10=-4.69444e-012 A12= 1.53060e-014 Page 17 K = 0.00000e+000 A 4=-4.17692e-005 A 6= 6.39652e-008 A 8= 6.52144e-010 A10=-5.41304e-012 A12= 1.71572e-014 Various data Zoom ratio 3.50 Wide Angle Mid-Telephoto Focal length 100.01 181.05 350.01 F-number 5.80 7.02 8.00 Half angle of view 12.21 6.81 3.54 Image height 21.64 21.64 21.64 Lens length 199.48 233.16 270.66 BF 48.68 44.50 39.84 d 5 20.44 54.13 91.63 d 8 36.85 20.92 3.19 d13 17.18 11.36 4.88 d17 11.26 8.69 1.00 d20 10.00 38.50 75.05 d22 48.68 44.50 39.84 Zoom lens group data Group starting plane focal length 1 1 187.56 2 6 -64.18 3 9 259.39 4 14 41.78 5 18 -37.94 6 21 200.00 [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd 1 81.922 6.75 1.59349 67.0 2 271.327 0.15 3 125.880 1.90 1.78885 48.6 4 55.716 8.50 1.43875 94.7 5 1162.628 (variable) 6 -677.896 1.00 1.80400 46.5 7 25.832 2.85 1.80610 33.3 8 100.072 (variable) 9(Aperture) ∞ 0.60 10 27.834 3.38 1.49700 81.5 11 164.466 3.11 12 -115.909 1.30 2.05090 26.9 13 282.269 (variable) 14* 328.394 4.00 1.53110 55.9 15* -36.741 (variable) 16 475.166 2.17 1.64769 33.8 17 -39.030 0.95 1.61800 63.4 18 36.189 (variable) 19 -66.132 1.50 1.49700 81.5 20 -278.665 (variable) Image plane ∞ Aspheric Data Side 14 K = 0.00000e+000 A 4=-1.26376e-005 A 6=-1.19115e-008 A 8= 2.37456e-010 A10=-3.25470e-012 A12= 1.12982e-014 Page 15 K = 0.00000e+000 A 4=-3.00508e-006 A 6=-9.30388e-009 A 8= 2.40835e-010 A10=-3.30499e-012 A12= 1.15799e-014 Various data Zoom ratio 2.40 Wide Angle Mid-Telephoto Focal length 250.00 416.21 600.00 F-number 7.63 9.80 11.33 Half angle of view 4.95 2.98 2.07 Image height 21.64 21.64 21.64 Lens total length 292.59 310.00 329.37 BF 70.11 113.47 161.73 d 5 65.81 83.22 102.60 d 8 78.31 42.49 2.62 d13 10.19 7.87 5.29 d15 20.00 10.35 1.00 d18 10.00 14.43 17.98 d20 70.11 113.47 161.73 Zoom lens group data Group starting plane focal length 1 1 206.90 2 6 -108.94 3 9 303.78 4 14 62.46 5 16 -67.10 6 19 -174.88 [Numerical Example 6] Unit: mm Surface Data Surface number rd nd νd 1 146.960 3.56 1.48749 70.2 2 2970.292 0.15 3 136.612 1.90 1.61340 44.3 4 57.926 5.80 1.49700 81.5 5 1014.952 (variable) 6 -98.695 1.00 1.80400 46.5 7 32.967 2.85 2.05090 26.9 8 83.134 (variable) 9(Aperture) ∞ 0.60 10* 91.871 2.40 1.49710 81.6 11* -108.954 (variable) 12 87.448 3.76 1.49700 81.5 13 -30.162 2.39 14* -19.786 2.00 1.68040 18.1 15* -26.414 (variable) 16 12798.799 2.24 1.96300 24.1 17 -49.891 0.95 1.83481 42.7 18 37.330 (variable) 19 127.306 5.90 1.48749 70.2 20 -50.154 (variable) 21 -52.612 1.50 1.43875 94.7 22 102.645 (variable) Image plane ∞ Aspheric Data Side 10 K = 0.00000e+000 A 4=-1.82591e-005 A 6=-3.28414e-007 A 8= 3.26981e-009 A10=-3.45786e-011 A12= 7.88756e-014 Page 11 K = 0.00000e+000 A 4=-7.18371e-006 A 6=-3.69839e-007 A 8= 4.13299e-009 A10=-4.11120e-011 A12= 1.06406e-013 Side 14 K = 0.00000e+000 A 4= 6.94676e-005 A 6=-3.36098e-007 A 8= 4.13862e-009 A10=-3.50812e-011 A12= 1.18904e-013 Page 15 K = 0.00000e+000 A 4= 5.41469e-005 A 6=-2.50303e-007 A 8= 2.53834e-009 A10=-2.06649e-011 A12= 6.73250e-014 Various data Zoom ratio 3.50 Wide Angle Mid-Telephoto Focal length 100.00 181.29 350.00 F-number 5.80 7.00 8.00 Half angle of view 12.21 6.81 3.54 Image height 21.64 21.64 21.64 Lens length 186.42 225.77 269.57 BF 29.91 45.52 62.89 d 5 14.58 53.93 97.73 d 8 41.50 23.09 2.60 d11 5.00 3.36 1.53 d15 10.16 8.52 1.00 d18 25.67 42.03 65.93 d20 22.61 12.33 0.90 d22 29.91 45.52 62.89 Zoom lens group data Group starting plane focal length 1 1 193.74 2 6 -75.01 3 9 100.67 4 12 70.51 5 16 -50.80 6 19 74.62 7 21 -79.05

[0048] [Table 1]

[0049] [Example 7] Next, an imaging device according to a seventh embodiment of the present invention will be described with reference to Fig. 13. Fig. 13 is a schematic diagram of an imaging device (digital still camera) 10 that uses any one of the zoom lenses 1a to 1f according to the first to sixth embodiments as an imaging optical system.

[0050] In Fig. 13, 13 is a camera body, and 11 is an imaging optical system (interchangeable lens) constituted by any one of the zoom lenses 1a to 1f of Examples 1 to 6. 12 is an imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body 13 and receives light from the imaging optical system 11 (an optical image formed by the imaging optical system 11) and performs photoelectric conversion. The camera body 13 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror.

[0051] By using any one of the zoom lenses according to Examples 1 to 6 in an imaging device such as a digital still camera, an imaging device having a small lens can be obtained. Also, by mounting any one of the zoom lenses according to Examples 1 to 6 in an interchangeable lens (optical device), a small interchangeable lens can be obtained.

[0052] According to each embodiment, it is possible to provide a small, lightweight zoom lens and an imaging device that have high optical performance over the entire zoom range.

[0053] 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]

[0054] 1a~1f zoom lens L1 First lens group L2 Second lens group L3: Third lens group L4 4th lens group

Claims

1. A zoom lens having, in order from an object side to an 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, a fourth lens group having a positive refractive power, and a fifth lens group, in which a distance between adjacent lens groups changes during zooming, During zooming from the wide-angle end to the telephoto end, the first lens group moves and the second lens group remains stationary, 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 the distance between the third lens group and the fourth lens group decreases, the first lens group includes a positive lens and a negative lens, the second lens group is composed of two or less lenses, the third lens group is composed of two or less lenses, The fourth lens group is composed of two or less lenses.

2. When the total optical length of the zoom lens at the telephoto end is TLt and the focal length of the zoom lens at the telephoto end is ft, 0.10<TLt / ft<0.80 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

3. When the average refractive index of the fourth lens group is ndL4ave, 1.40<ndL4ave<1.70 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. When the focal length of the second lens group is fL2 and the focal length of the zoom lens at the telephoto end is ft, -0.30<fL2 / ft<-0.10 4. The zoom lens according to claim 1, wherein the following condition is satisfied:

5. When the focal length of the third lens group is fL3 and the focal length of the zoom lens at the telephoto end is ft, 0.15<fL3 / ft<0.90 5. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. During zooming from the wide-angle end to the telephoto end, when the amount of movement of the first lens group is ML1 and the amount of movement of the fourth lens group is ML4, 0.3<ML4 / ML1<3.0 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 fL1 and the focal length of the second lens group is fL2, -0.80<fL2 / fL1<-0.20 7. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. When the focal length of the fourth lens group is fL4 and the focal length of the zoom lens at the telephoto end is ft, 0.05<fL4 / ft<0.50 8. The zoom lens according to claim 1, wherein the following condition is satisfied:

9. When the focal length of the first lens group is fL1 and the focal length of the fourth lens group is fL4, 0.10<fL4 / fL1<0.70 9. The zoom lens according to claim 1, wherein the following condition is satisfied:

10. When the focal length of the third lens group is fL3 and the focal length of the fourth lens group is fL4, 0.05<fL4 / fL3<1.00 10. The zoom lens according to claim 1, wherein the following condition is satisfied:

11. When the average specific gravity of the lenses constituting the fourth lens group is SL4ave, 0.90<SL4ave<2.80 11. The zoom lens according to claim 1, wherein the following condition is satisfied:

12. When the average Abbe number of the positive lenses included in the first lens group with respect to the d line is νdL1Pave, 55<νdL1Pave<99 12. The zoom lens according to claim 1, wherein the following condition is satisfied:

13. When the average Abbe number of the positive lenses included in the third lens group with respect to the d line is νdL3Pave, 55<νdL3Pave<99 13. The zoom lens according to claim 1, which satisfies the following condition:

14. 14. The zoom lens according to claim 1, wherein the second lens group is made up of, in order from the object side to the image side, two lenses: a negative lens and a positive lens.

15. 15. The zoom lens according to claim 1, wherein the fourth lens group includes a lens having at least one aspheric surface.

16. The zoom lens has an aperture stop, 16. The zoom lens according to claim 1, wherein the fifth lens group is a focus lens group that is disposed closer to the image side than the aperture stop and performs focusing from infinity to a close range.

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

Images