Variable power optical system and optical device

Abstract

To provide a variable power optical system capable of restraining a variations in an angle of field at the time of focusing.SOLUTION: A variable power optical system ZL comprises a front group GA and a rear group GB, the front group GA includes a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power in order from the furthest object side, the rear group GA includes a first focusing lens group GF1 having positive refractive power disposed in the furthest object side of the rear group GB, a second focusing lens group GF2 having negative refractive power disposed in the image surface side, and a lens group having positive refractive power disposed in the image surface side, the interval between respective adjacent lens groups is changed at the time of scaling, a lens group disposed in the furthest image surface side travels along a light axis, the first focusing lens group GF1 and the second focusing lens group GF2 travel along a light axis with each different trajectory at the time of focusing from an object at infinity to a short-distance object, and the following conditional expression is satisfied, namely 0.25<βF1t / βF1w<2.00 0.25<βF2w / βF2t<2.00.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a variable magnification optical system and an optical apparatus. [Background technology]

[0002] Variable magnification optical systems suitable for photo cameras, electronic still cameras, video cameras, etc. have been proposed (see, for example, Patent Document 1). In such variable magnification optical systems, it is required to suppress fluctuations in the angle of view when focusing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 196022 Summary of the Invention

[0004] A first variable magnification optical system according to the present invention comprises a front group and a rear group arranged in order from the object side along the optical axis, the rear group having a first focusing lens group arranged closest to the object side of the rear group, and a second focusing lens group arranged on the image plane side of the first focusing lens group, the spacing between adjacent lens groups changing during magnification variation, and when focusing from an object at infinity to an object at a close distance, the front group is fixed with respect to the image plane, and the first focusing lens group and the second focusing lens group move along the optical axis on different trajectories, and the following conditional expression is satisfied: 0.25<βF1t / βF1w<2.00 0.25<βF2w / βF2t<2.00 where βF1t is the magnification of the first focusing lens group when focused on infinity in the telephoto end state. βF1w: Magnification of the first focusing lens group when focused on infinity in the wide-angle end state βF2t: Magnification of the second focusing lens group when focused at infinity in the telephoto end state βF2w: Magnification of the second focusing lens group when focused on infinity in the wide-angle end state

[0005] A second variable magnification optical system according to the present invention comprises a front group and a rear group arranged in order from the object side along the optical axis, the rear group having a focusing lens group that is located closest to the object side of the rear group and moves along the optical axis during focusing, the spacing between adjacent lens groups changing during magnification variation, and the following conditional expression is satisfied: 0.35 <fF2 / fBF2w<0.75 where fF2 is the focal length of the focusing lens group, and if the rear group has a plurality of focusing lens groups including the focusing lens group, the focal length of the focusing lens group that is located closest to the image plane among the plurality of focusing lens groups. fBF2w: composite focal length of each lens group from the focusing lens group to the lens group closest to the image plane in the wide-angle end state; if the rear group has multiple focusing lens groups including the focusing lens group, composite focal length of each lens group from the focusing lens group closest to the image plane among the multiple focusing lens groups to the lens group closest to the image plane

[0006] An optical apparatus according to the present invention is configured to include the variable magnification optical system described above. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram showing the lens configuration of a variable magnification optical system according to Example 1. [Figure 2] 2A and 2B are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 3] 3A and 3B are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 4] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 2. [Figure 5] 5A and 5B are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focused on infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 6]6A and 6B are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 7] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 3. [Figure 8] 8A and 8B are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focused on infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 9] 9A and 9B are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 10] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 4. [Figure 11] 11A and 11B are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 12] 12A and 12B are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 13] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 5. [Figure 14] 14A and 14B are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focused on infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 15] 15A and 15B are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 16] 1 is a diagram showing the configuration of a camera equipped with a variable magnification optical system according to each embodiment. [Figure 17] 10 is a flowchart illustrating a method for manufacturing a variable magnification optical system according to each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present invention will now be described. First, a camera (optical device) equipped with a variable magnification optical system according to each embodiment will be described with reference to FIG. 16. As shown in FIG. 16, this camera 1 is composed of a body 2 and a photographic lens 3 attached to the body 2. The body 2 is equipped with an image sensor 4, a body control unit (not shown) that controls the operation of the digital camera, and an LCD screen 5. The photographic lens 3 is equipped with a variable magnification optical system ZL consisting of multiple lens groups, and a lens position control mechanism (not shown) that controls the position of each lens group. The lens position control mechanism is composed of a sensor that detects the position of the lens groups, a motor that moves the lens groups back and forth along the optical axis, a control circuit that drives the motor, etc.

[0009] Light from the subject is collected by the variable magnification optical system ZL of the photographing lens 3 and reaches the image plane I of the image sensor 4. The light from the subject that reaches the image plane I is photoelectrically converted by the image sensor 4 and recorded as digital image data in a memory (not shown). The digital image data recorded in the memory can be displayed on the liquid crystal screen 5 in response to a user operation. Note that this camera may be a mirrorless camera or a single-lens reflex camera with a quick-return mirror.

[0010] Next, a variable magnification optical system according to the first embodiment will be described. As shown in FIG. 1, a variable magnification optical system ZL(1) as an example of a variable magnification optical system (zoom lens) ZL according to the first embodiment is composed of a front group GA and a rear group GB, arranged in order from the object side along the optical axis. The rear group GB has a first focusing lens group GF1 arranged closest to the object side of the rear group GB, and a second focusing lens group GF2 arranged on the image plane side of the first focusing lens group GF1. When varying magnification, the spacing between adjacent lens groups changes. When focusing from an object at infinity to a close-up object, the front group GA is fixed relative to the image plane, and the first focusing lens group GF1 and the second focusing lens group GF2 move along the optical axis along different trajectories. It is preferable that the first focusing lens group GF1 have positive refractive power. It is preferable that the second focusing lens group GF2 have negative refractive power. When focusing from an object at infinity to a close-up object, it is preferable that the first focusing lens group GF1 move toward the image plane side. When focusing from an object at infinity to an object at a close distance, it is desirable that the second focusing lens group GF2 moves toward the image plane side.

[0011] With the above-described configuration, the variable magnification optical system ZL according to the first embodiment satisfies the following conditional expressions (1) and (2). 0.25<βF1t / βF1w<2.00 (1) 0.25<βF2w / βF2t<2.00 (2) where βF1t is the magnification of the first focusing lens group GF1 at the telephoto end when focused on infinity. βF1w: Magnification of the first focusing lens group GF1 at the wide-angle end when focused at infinity βF2t: Magnification of the second focusing lens group GF2 at the telephoto end when focused on infinity βF2w: Magnification of the second focusing lens group GF2 at the wide-angle end when focused on infinity

[0012] According to the first embodiment, it is possible to obtain a variable magnification optical system with little fluctuation in the angle of view during focusing, and an optical apparatus equipped with this variable magnification optical system. The variable magnification optical system ZL according to the first embodiment may be the variable magnification optical system ZL(2) shown in Fig. 4, the variable magnification optical system ZL(3) shown in Fig. 7, or the variable magnification optical system ZL(4) shown in Fig. 10.

[0013] Conditional formula (1) defines an appropriate relationship between the magnification of the first focusing lens group GF1 at the telephoto end when focusing at infinity and the magnification of the first focusing lens group GF1 at the wide-angle end when focusing at infinity. Conditional formula (2) defines an appropriate relationship between the magnification of the second focusing lens group GF2 at the telephoto end when focusing at infinity and the magnification of the second focusing lens group GF2 at the wide-angle end when focusing at infinity.

[0014] By satisfying conditional expressions (1) and (2), the changes in magnification of the first focusing lens group GF1 and the second focusing lens group GF2 during focusing are canceled out, and fluctuations in the angle of view during focusing can be reduced.

[0015] If the value corresponding to conditional expression (1) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. The effects of this embodiment can be further ensured by setting the lower limit of conditional expression (1) to 0.30, 0.40, 0.50, 0.55, 0.60, 0.65, 0.68, 0.70, or even 0.73. Furthermore, the effects of this embodiment can be further ensured by setting the upper limit of conditional expression (1) to 1.85, 1.70, 1.60, 1.50, 1.40, 1.35, 1.30, 1.25, 1.20, or even 1.18.

[0016] If the value corresponding to conditional expression (2) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. The effects of this embodiment can be further ensured by setting the lower limit of conditional expression (2) to 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, or even 0.80. Furthermore, the effects of this embodiment can be further ensured by setting the upper limit of conditional expression (2) to 1.98, 1.95, 1.93, 1.90, 1.88, 1.85, 1.80, 1.70, 1.60, 1.50, 1.40, 1.35, or even 1.30.

[0017] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (3). 0.01<βF1w / βF2w<0.25 (3)

[0018] Conditional expression (3) defines an appropriate relationship between the magnification of the first focusing lens group GF1 when focusing at infinity in the wide-angle end state and the magnification of the second focusing lens group GF2 when focusing at infinity in the wide-angle end state. By satisfying conditional expression (3), fluctuations in the angle of view during focusing can be reduced.

[0019] If the value corresponding to conditional expression (3) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (3) to 0.02, 0.03, or even 0.04, the effects of this embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (3) to 0.23, 0.20, 0.19, 0.18, or even 0.17, the effects of this embodiment can be more reliably achieved.

[0020] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (4). 0.10<ΔX1w / ΔX2w<0.75 (4) where ΔX1w: the amount of movement of the first focusing lens group GF1 when focusing from an object at infinity to an object at a close distance in the wide-angle end state ΔX2w: the amount of movement of the second focusing lens group GF2 when focusing from an object at infinity to an object at a close distance in the wide-angle end state

[0021] Conditional expression (4) defines an appropriate relationship between the amount of movement of the first focusing lens group GF1 when focusing from an object at infinity to an object at a close distance in the wide-angle end state and the amount of movement of the second focusing lens group GF2 when focusing from an object at infinity to an object at a close distance in the wide-angle end state. By satisfying conditional expression (4), fluctuations in the angle of view during focusing can be reduced.

[0022] If the value corresponding to conditional expression (4) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. The effects of this embodiment can be further ensured by setting the lower limit of conditional expression (4) to 0.12, 0.14, 0.15, 0.20, 0.23, 0.25, 0.30, 0.35, or even 0.40. Furthermore, the effects of this embodiment can be further ensured by setting the upper limit of conditional expression (4) to 0.73, 0.70, 0.68, 0.65, 0.63, or even 0.62.

[0023] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (5). 0.001<1 / fAt<0.020 (5) where fAt is the focal length of the front group GA at the telephoto end

[0024] Condition (5) defines an appropriate range for the focal length of the front group GA in the telephoto end state. By satisfying condition (5), fluctuations in the angle of view during focusing can be reduced.

[0025] If the value corresponding to conditional expression (5) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (5) to 0.002, or even 0.003, the effect of this embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (5) to 0.018, 0.015, 0.013, or even 0.010, the effect of this embodiment can be more reliably achieved.

[0026] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (6). 0.001<1 / fAF2w<0.015 (6) where fAF2w is the composite focal length of each lens group from the lens group closest to the object to the second focusing lens group GF2 in the wide-angle end state.

[0027] Condition (6) defines an appropriate range for the combined focal length of each lens group from the lens group closest to the object to the second focusing lens group GF2 in the wide-angle end state. By satisfying condition (6), fluctuations in the angle of view during focusing can be reduced.

[0028] If the value corresponding to conditional expression (6) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (6) to 0.002, the effect of this embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (6) to 0.013, 0.010, 0.008, or even 0.006, the effect of this embodiment can be more reliably achieved.

[0029] In the variable magnification optical system ZL according to the first embodiment, the second focusing lens group GF2 preferably has one positive lens and one negative lens arranged in order from the object side along the optical axis, thereby reducing fluctuations in aberrations such as chromatic aberration during focusing.

[0030] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (7). 0.35 <fF2 / fBF2w<0.75 ···(7) where fF2 is the focal length of the second focusing lens group GF2 fBF2w: the composite focal length of each lens group from the second focusing lens group GF2 to the lens group closest to the image plane in the wide-angle end state

[0031] Condition (7) defines an appropriate relationship between the focal length of the second focusing lens group GF2 and the combined focal length of each lens group from the second focusing lens group GF2 to the lens group closest to the image plane in the wide-angle end state. By satisfying condition (7), fluctuations in the angle of view during focusing can be reduced.

[0032] If the value corresponding to conditional expression (7) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (7) to 0.36, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.54, or even 0.55, the effects of this embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (7) to 0.73 or even 0.70, the effects of this embodiment can be further ensured.

[0033] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (8). -2.00 <fBF2w / fBrw<-0.15 ···(8) where fBF2w is the composite focal length of each lens group from the second focusing lens group GF2 to the lens group closest to the image plane in the wide-angle end state. fBrw: The composite focal length of the lens group located closer to the image plane than the second focusing lens group GF2 in the wide-angle end state

[0034] Conditional expression (8) defines an appropriate relationship between the composite focal length of each lens group from the second focusing lens group GF2 to the lens group closest to the image plane in the wide-angle end state and the composite focal length of the lens group located closer to the image plane than the second focusing lens group GF2 in the wide-angle end state. By satisfying conditional expression (8), fluctuations in the angle of view during focusing can be reduced.

[0035] If the value corresponding to conditional expression (8) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. The effects of this embodiment can be further ensured by setting the lower limit of conditional expression (8) to -1.90, -1.80, -1.70, -1.65, -1.35, -1.20, -1.10, or even -1.05. Furthermore, the effects of this embodiment can be further ensured by setting the upper limit of conditional expression (8) to -0.20, -0.25, -0.30, -0.35, -0.40, -0.45, -0.50, -0.55, or even -0.58.

[0036] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (9). 0.10<βBF2w / βF2w<0.80 (9) where βBF2w is the composite magnification of each lens group from the second focusing lens group GF2 to the lens group closest to the image plane in the wide-angle end state.

[0037] Condition (9) defines an appropriate relationship between the combined magnification of the lens groups from the second focusing lens group GF2 to the lens group closest to the image plane in the wide-angle end state, and the magnification of the second focusing lens group GF2 in the wide-angle end state. By satisfying condition (9), fluctuations in the angle of view during focusing can be reduced.

[0038] If the value corresponding to conditional expression (9) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (9) to 0.13, 0.15, 0.18, 0.20, or even 0.23, the effects of this embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (9) to 0.78, 0.75, 0.73, or even 0.70, the effects of this embodiment can be more reliably achieved.

[0039] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (10). 0.05<βBrw / βBF2w<0.50 (10) where βBrw is the combined magnification of the lens group arranged closer to the image plane than the second focusing lens group GF2 in the wide-angle end state. βBF2w: composite magnification of each lens group from the second focusing lens group GF2 to the lens group closest to the image plane in the wide-angle end state

[0040] Condition (10) defines an appropriate relationship between the combined magnification of the lens group located closer to the image plane than the second focusing lens group GF2 in the wide-angle end state and the combined magnification of each lens group from the second focusing lens group GF2 to the lens group closest to the image plane in the wide-angle end state. By satisfying condition (10), fluctuations in the angle of view during focusing can be reduced.

[0041] If the value corresponding to conditional expression (10) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (10) to 0.06, 0.08, 0.10, or even 0.12, the effects of this embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (10) to 0.48, 0.45, 0.43, 0.41, or even 0.40, the effects of this embodiment can be more reliably achieved.

[0042] Next, a variable magnification optical system according to the second embodiment will be described. As shown in FIG. 1, a variable magnification optical system ZL(1) as an example of a variable magnification optical system (zoom lens) ZL according to the second embodiment is composed of a front group GA and a rear group GB, arranged in order from the object side along the optical axis. The rear group GB has a focusing lens group that is located closest to the object side of the rear group GB and moves along the optical axis during focusing. When the magnification is changed, the spacing between adjacent lens groups changes.

[0043] With the above-described configuration, the variable-magnification optical system ZL according to the second embodiment satisfies the following conditional expression (11). 0.35 <fF2 / fBF2w<0.75 ···(11) where fF2 is the focal length of the focusing lens group, and if the rear group GB has a plurality of focusing lens groups including the focusing lens group, the focal length of the focusing lens group that is located closest to the image plane among the plurality of focusing lens groups. fBF2w: the composite focal length of each lens group from the focusing lens group to the lens group closest to the image plane in the wide-angle end state; if the rear group GB has multiple focusing lens groups including the focusing lens group, the composite focal length of each lens group from the focusing lens group closest to the image plane among the multiple focusing lens groups to the lens group closest to the image plane

[0044] According to the second embodiment, it is possible to obtain a variable magnification optical system with little fluctuation in the angle of view during focusing, and an optical apparatus equipped with this variable magnification optical system. The variable magnification optical system ZL according to the second embodiment may be the variable magnification optical system ZL(2) shown in Fig. 4, the variable magnification optical system ZL(3) shown in Fig. 7, the variable magnification optical system ZL(4) shown in Fig. 10, or the variable magnification optical system ZL(5) shown in Fig. 13.

[0045] Condition (11) defines the appropriate relationship between the focal length of the focusing lens group and the combined focal length of each lens group from the focusing lens group to the lens group closest to the image plane in the wide-angle end state. By satisfying condition (11), fluctuations in the angle of view during focusing can be reduced.

[0046] If the value corresponding to conditional expression (11) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (11) to 0.36, 0.38, 0.40, 0.42, 0.45, 0.48, 0.50, 0.54, or even 0.55, the effects of this embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (11) to 0.73 or even 0.70, the effects of this embodiment can be further ensured.

[0047] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (12). -2.00 <fBF2w / fBrw<-0.15 ···(12) where fBrw is the composite focal length of the lens group arranged closer to the image plane than the focusing lens group in the wide-angle end state. If the rear group GB has multiple focusing lens groups including the focusing lens group, fBrw is the composite focal length of the lens group arranged closer to the image plane than the focusing lens group closest to the image plane among the multiple focusing lens groups.

[0048] Condition (12) defines an appropriate relationship between the composite focal length of each lens group from the focusing lens group to the lens group closest to the image plane in the wide-angle end state and the composite focal length of the lens group located closer to the image plane than the focusing lens group in the wide-angle end state. By satisfying condition (12), fluctuations in the angle of view during focusing can be reduced.

[0049] If the value corresponding to conditional expression (12) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. The effects of this embodiment can be further ensured by setting the lower limit of conditional expression (12) to -1.90, -1.80, -1.70, -1.65, -1.35, -1.20, -1.10, or even -1.05. Furthermore, the effects of this embodiment can be further ensured by setting the upper limit of conditional expression (12) to -0.20, -0.30, -0.35, -0.40, -0.45, -0.50, -0.55, or even -0.58.

[0050] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (13). 0.10<βBF2w / βF2w<0.80 (13) where βBF2w is the composite magnification of each lens group from the focusing lens group to the lens group closest to the image plane in the wide-angle end state, and if the rear group GB has multiple focusing lens groups including the focusing lens group, the composite magnification of each lens group from the focusing lens group located closest to the image plane among the multiple focusing lens groups to the lens group closest to the image plane. βF2w: the magnification of the focusing lens group in the wide-angle end state. If the rear group GB has a plurality of focusing lens groups including the focusing lens group, the magnification of the focusing lens group located closest to the image plane among the plurality of focusing lens groups.

[0051] Condition (13) defines an appropriate relationship between the combined magnification of each lens group from the focusing lens group to the lens group closest to the image plane in the wide-angle end state and the magnification of the focusing lens group in the wide-angle end state. By satisfying condition (13), fluctuations in the angle of view during focusing can be reduced.

[0052] If the value corresponding to conditional expression (13) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (13) to 0.13, 0.15, 0.18, 0.20, or even 0.23, the effects of this embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (13) to 0.78, 0.75, 0.73, or even 0.70, the effects of this embodiment can be more reliably achieved.

[0053] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (14). 0.05<βBrw / βBF2w<0.50 ···(14) where βBrw is the composite magnification of the lens group arranged closer to the image plane than the focusing lens group in the wide-angle end state, and if the rear group GB has a plurality of focusing lens groups including the focusing lens group, the composite magnification of the lens group arranged closer to the image plane than the focusing lens group located closest to the image plane among the plurality of focusing lens groups. βBF2w: composite magnification of each lens group from the focusing lens group to the lens group closest to the image plane in the wide-angle end state; if the rear group GB has multiple focusing lens groups including the focusing lens group, composite magnification of each lens group from the focusing lens group closest to the image plane among the multiple focusing lens groups to the lens group closest to the image plane

[0054] Condition (14) defines an appropriate relationship between the composite magnification of the lens group located closer to the image plane than the focusing lens group in the wide-angle end state and the composite magnification of each lens group from the focusing lens group to the lens group closest to the image plane in the wide-angle end state. By satisfying condition (14), fluctuations in the angle of view during focusing can be reduced.

[0055] If the value corresponding to conditional expression (14) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (14) to 0.06, 0.08, 0.10, or even 0.12, the effects of this embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (14) to 0.48, 0.45, 0.43, 0.41, or even 0.40, the effects of this embodiment can be more reliably achieved.

[0056] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (15). 0.001<1 / fAF2w<0.015 (15) where fAF2w is the composite focal length of each lens group from the lens group closest to the object to the focusing lens group in the wide-angle end state, and if the rear group GB has multiple focusing lens groups including the focusing lens group, the composite focal length of each lens group from the lens group closest to the object to the focusing lens group located closest to the image plane among the multiple focusing lens groups.

[0057] Condition (15) defines an appropriate range for the composite focal length of each lens group from the lens group closest to the object to the focusing lens group in the wide-angle end state. By satisfying condition (15), fluctuations in the angle of view during focusing can be reduced.

[0058] If the value corresponding to conditional expression (15) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (15) to 0.002, the effect of this embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (15) to 0.013, 0.010, 0.008, or even 0.006, the effect of this embodiment can be more reliably achieved.

[0059] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (16). 0.15<(ftinf-ftmod) / ftinf<0.40 ···(16) where ftinf is the focal length of the variable magnification optical system ZL at the telephoto end when focused at infinity ftmod: focal length of the variable magnification optical system ZL at the telephoto end when focusing at the closest distance

[0060] Condition (16) defines the appropriate relationship between the focal length of the variable magnification optical system ZL when focused at infinity in the telephoto end state and the focal length of the variable magnification optical system ZL when focused at a close distance in the telephoto end state. By satisfying condition (16), fluctuations in the angle of view during focusing can be reduced.

[0061] If the value corresponding to conditional expression (16) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (16) to 0.18, 0.20, 0.22, 0.24, 0.25, or even 0.26, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (16) to 0.38, 0.36, 0.35, or even 0.33, the effects of each embodiment can be more reliably achieved.

[0062] The variable magnification optical system ZL according to the first and second embodiments has an aperture stop S, and it is desirable that the following conditional expression (17) be satisfied: 0.35 <STw / TLw<0.65 ···(17) Where STw is the distance on the optical axis from the aperture stop S to the image plane in the wide-angle end state. TLw: Total length of the variable magnification optical system ZL in the wide-angle end state

[0063] Conditional expression (17) defines an appropriate relationship between the distance on the optical axis from the aperture stop S to the image plane in the wide-angle end state and the overall length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (17), various aberrations such as distortion and curvature of field in the wide-angle end state can be effectively corrected.

[0064] If the value corresponding to conditional expression (17) falls outside the above range, it becomes difficult to correct various aberrations, such as distortion and curvature of field, in the wide-angle end state. By setting the lower limit of conditional expression (17) to 0.33, 0.35, 0.38, 0.40, 0.43, 0.45, or even 0.46, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (17) to 0.63, 0.60, 0.58, 0.56, or even 0.55, the effects of each embodiment can be further ensured.

[0065] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (18). 0.04 <Bft / TLt<0.35 ···(18) However, Bft: back focus of the variable magnification optical system ZL in the telephoto end state TLt: total length of variable magnification optical system ZL in the telephoto end state

[0066] Conditional expression (18) defines an appropriate relationship between the back focus of the variable magnification optical system ZL in the telephoto end state and the overall length of the variable magnification optical system ZL in the telephoto end state. By satisfying conditional expression (18), various aberrations, such as spherical aberration, in the telephoto end state can be effectively corrected.

[0067] If the value corresponding to conditional expression (18) falls outside the above range, it becomes difficult to correct various aberrations, such as spherical aberration, in the telephoto end state. By setting the lower limit of conditional expression (18) to 0.05, 0.06, 0.08, 0.10, 0.13, 0.15, or even 0.16, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (18) to 0.33, 0.30, or even 0.28, the effects of each embodiment can be further ensured.

[0068] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (19). 0.25 <Bfw / fw<0.70 ···(19) Bfw: back focus of the variable magnification optical system ZL in the wide-angle end state TLw: Total length of the variable magnification optical system ZL in the wide-angle end state

[0069] Condition (19) defines the appropriate relationship between the back focal length of the variable magnification optical system ZL in the wide-angle end state and the overall length of the variable magnification optical system ZL in the wide-angle end state. By satisfying condition (19), various aberrations, including coma in the wide-angle end state, can be effectively corrected.

[0070] If the value corresponding to conditional expression (19) falls outside the above range, it becomes difficult to correct various aberrations, including coma at the wide-angle end. By setting the lower limit of conditional expression (19) to 0.28, 0.30, 0.33, 0.35, 0.38, 0.40, 0.43, 0.45, 0.48, or even 0.50, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (19) to 0.68, 0.65, 0.63, 0.60, 0.58, or even 0.55, the effects of each embodiment can be further ensured.

[0071] Next, with reference to FIG. 17, a manufacturing method for the variable magnification optical system ZL according to the first embodiment will be outlined. First, the front group GA and the rear group GB are arranged, starting from the object side along the optical axis (Step ST1). Next, the first focusing lens group GF1 is arranged closest to the object side of the rear group GB, and the second focusing lens group GF2 is arranged on the image plane side of the first focusing lens group GF1 of the rear group GB (Step ST2). Next, the system is configured so that the spacing between adjacent lens groups changes during magnification (Step ST3). Furthermore, during focusing from an object at infinity to a close object, the front group GA is fixed relative to the image plane, and the first focusing lens group GF1 and the second focusing lens group GF2 move along the optical axis along different trajectories. Then, the lenses are arranged within the lens barrel so as to satisfy at least the above conditional expressions (1) and (2) (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system with minimal fluctuation in the angle of view during focusing. Next, as with the first embodiment, a manufacturing method for a variable magnification optical system ZL according to the second embodiment will be outlined with reference to FIG. 17. First, the front group GA and the rear group GB are arranged in order from the object side along the optical axis (Step ST1). Next, a focusing lens group is arranged closest to the object side of the rear group GB (Step ST2). Next, the system is configured so that the spacing between adjacent lens groups changes during magnification (Step ST3). Also, the focusing lens group is configured so that it moves along the optical axis during focusing. Then, the lenses are arranged within the lens barrel so as to satisfy at least conditional expression (11) above (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system with little fluctuation in the angle of view during focusing. [Example]

[0072] Variable-magnification optical systems ZL according to examples of each embodiment will be described below with reference to the drawings. Examples 1 to 4 correspond to the first embodiment, and Examples 1 to 5 correspond to the second embodiment. FIGS. 1, 4, 7, 10, and 13 are cross-sectional views showing the configuration and refractive power distribution of variable-magnification optical systems ZL {ZL(1) to ZL(5)} according to Examples 1 to 5. In the cross-sectional views of the variable-magnification optical systems ZL(1) to ZL(5) according to Examples 1 to 5, the direction of movement of the focusing group along the optical axis when focusing from infinity to a close-distance object is indicated by an arrow accompanied by the word "focusing." In the cross-sectional views of the variable-magnification optical systems ZL(1) to ZL(5) according to Examples 1 to 5, the direction of movement of each lens group along the optical axis when changing magnification from the wide-angle end state (W) to the telephoto end state (T) is indicated by an arrow.

[0073] 1, 4, 7, 10, and 13, each lens group and each group is represented by a combination of the symbol G and a number, and each lens is represented by a combination of the symbol L and a number. In this case, to prevent the symbols and numbers from becoming too numerous and complicated, each embodiment uses its own independent combination of symbols and numbers to represent the lens groups, etc. Therefore, even if the same combination of symbols and numbers is used between embodiments, this does not mean that the embodiments have the same configuration.

[0074] Tables 1 to 5 are shown below, with Table 1 showing data on the various elements in Example 1, Table 2 in Example 2, Table 3 in Example 3, Table 4 in Example 4, and Table 5 in Example 5. In each example, the d-line (wavelength λ=587.6 nm) and g-line (wavelength λ=435.8 nm) were selected as the targets for calculating aberration characteristics.

[0075] In the [Overall Specifications] table, f is the focal length of the entire lens system, FNO is the F-number, 2ω is the angle of view (unit: ° (degrees), where ω is half the angle of view), and Ymax is the maximum image height. TL is the distance from the frontmost lens surface to the last lens surface on the optical axis when focused at infinity plus Bf, and Bf is the distance from the last lens surface to the image plane I on the optical axis when focused at infinity (back focus). Note that these values ​​are shown for both the wide-angle end (W) and the telephoto end (T) magnification settings.

[0076] In the table of "Overall Specifications" for Examples 1 to 4, βF1t indicates the magnification of the first focusing lens group when focusing at infinity in the telephoto end state. βF1w indicates the magnification of the first focusing lens group when focusing at infinity in the wide-angle end state. βF2t indicates the magnification of the second focusing lens group when focusing at infinity in the telephoto end state. βF2w indicates the magnification of the second focusing lens group when focusing at infinity in the wide-angle end state. βBF2w indicates the combined magnification of each lens group from the second focusing lens group to the lens group closest to the image plane in the wide-angle end state. βBrw indicates the combined magnification of the lens group located closer to the image plane than the second focusing lens group in the wide-angle end state. ΔX1w indicates the amount of movement of the first focusing lens group when focusing from an object at infinity to an object at a close distance in the wide-angle end state. ΔX2w indicates the amount of movement of the second focusing lens group when focusing from an object at infinity to an object at a close distance in the maximum wide-angle state. fF2 indicates the focal length of the second focusing lens group. fAF2w indicates the composite focal length of each lens group from the lens group closest to the object to the second focusing lens group in the maximum wide-angle state. fBF2w indicates the composite focal length of each lens group from the second focusing lens group to the lens group closest to the image plane in the maximum wide-angle state. fBrw indicates the composite focal length of the lens group located closer to the image plane than the second focusing lens group in the maximum wide-angle state. fAt indicates the focal length of the front group in the maximum telephoto state.

[0077] In the table of "Overall Specifications" for the fifth embodiment, βF2w indicates the magnification of the focusing lens group in the wide-angle end state. βBF2w indicates the composite magnification of each lens group from the focusing lens group to the lens group closest to the image surface in the wide-angle end state. βBrw indicates the composite magnification of the lens group located closer to the image surface than the focusing lens group in the wide-angle end state. fF2 indicates the focal length of the focusing lens group. AF2w indicates the composite focal length of each lens group from the lens group closest to the object surface to the focusing lens group in the wide-angle end state. fBF2w indicates the composite focal length of each lens group from the focusing lens group to the lens group closest to the image surface in the wide-angle end state. fBrw indicates the composite focal length of the lens group located closer to the image surface than the focusing lens group in the wide-angle end state.

[0078] In the [Lens Specifications] table, the surface number indicates the order of the optical surfaces from the object side along the direction of light ray travel, R is the radius of curvature of each optical surface (surfaces whose center of curvature is on the image side have a positive value), D is the surface spacing, which is the distance on the optical axis from each optical surface to the next optical surface (or image plane), nd is the refractive index of the optical element material with respect to the d-line, and νd is the Abbe number of the optical element material with respect to the d-line. The "∞" in the radius of curvature indicates a plane or an aperture, and (S) indicates the aperture stop S. The refractive index of air, nd = 1.00000, is omitted.

[0079] The [Variable Distance Data] table shows the surface spacing for surface number i, which has a surface spacing of (Di) in the [Lens Specifications] table. The [Variable Distance Data] table also shows the surface spacing when focused at infinity and when focused at close range.

[0080] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0081] In the following, for all specifications, the focal length f, radius of curvature R, surface spacing D, and other lengths are generally expressed in "mm" unless otherwise specified, but this is not limited to this, as the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0082] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0083] (First Example) Example 1 will be described with reference to FIGS. 1, 2, 3, and Table 1. FIG. 1 shows the lens configuration of a variable magnification optical system ZL(1) according to Example 1. The variable magnification optical system ZL(1) is composed of, arranged in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, an aperture stop S, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having positive refractive power. An image plane I is located behind the sixth lens group G6.

[0084] In this embodiment, the fourth lens group G4 functions as the first focusing lens group GF1, and the fifth lens group G5 functions as the second focusing lens group GF2. That is, the first lens group G1, the second lens group G2, and the third lens group G3 form a front group GA that is fixed relative to the image plane I during focusing. The fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 form a rear group GB.

[0085] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 move along the locus indicated by the arrows in the lower part of Figure 1. This changes the spacing between adjacent lens groups, changing the imaging magnification (variation of magnification occurs). The second lens group G2 is fixed and does not move during magnification. When focusing from an object at infinity to a close object, the fourth lens group G4 and the fifth lens group G5 move toward the image plane along different loci, as indicated by the arrows in the upper part of Figure 1.

[0086] The first lens group G1 is composed of a cemented positive lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side, and a biconvex positive lens L13. The second lens group G2 is composed of a biconcave negative lens L21, a biconvex positive lens L22, a biconcave negative lens L23, and a biconcave negative lens L24. The third lens group G3 is composed of a biconvex positive lens L31, a cemented positive lens consisting of a negative meniscus lens L32 with a convex surface facing the object side and a biconvex positive lens L33, and a cemented positive lens consisting of a biconvex positive lens L34 and a biconcave negative lens L35.

[0087] The fourth lens group G4 is composed of a biconvex positive lens L41, a negative meniscus lens L42 with its convex surface facing the object side, and a positive meniscus lens L43 with its convex surface facing the object side. The fifth lens group G5 is composed of a positive meniscus lens L51 with its concave surface facing the object side, and a biconcave negative lens L52.

[0088] The sixth lens group G6 is composed of a positive meniscus lens L61 with its concave surface facing the object side, and a negative meniscus lens L62 with its concave surface facing the object side. A parallel plate PP is disposed in front of the image plane I.

[0089] Table 1 shows the values ​​of the specifications of the variable magnification optical system according to the first example. (Table 1) [Overall specifications] Magnification ratio=2.691 βF1t=0.39 βF1w=0.42 βF2t=3.10 βF2w=2.56 βBF2w=1.73 βBrw=0.68 ΔX1w=2.93 ΔX2w=4.92 fF2=-41.42 fAF2w=272.76 fBF2w=-72.93 fBrw=116.51 fAt=106.58 WMT f 72.10 102.64 194.00 FNO 4.10 4.10 4.11 2ω 33.77 23.58 12.36 Ymax 21.60 21.60 21.60 TL 167.56 185.12 204.48 BF 37.76 40.23 51.42 [Lens Specifications] Surface No. R D nd νd Object Surface ∞ 1 144.8366 1.00 1.8000 29.84 2 73.1116 5.85 1.5952 67.73 3 302.7125 0.10 4 68.5085 7.10 1.4970 81.14 5 -2151.2492 (D5) 6 -1656.3 * 1.00 1.7200 46.02 7 33.5940 1.06 8 34.1723 7.56 1.8414 24.56 9 -119.9733 0.78 10 -139.3696 1.00 1.8062 40.91 11 53.2947 4.69 12 -43.3327 1.00 1.7620 40.10 13 295.7341 (D13) 14 265.1264 3.48 1.6400 60.08 15 -69.2515 2.00 16 60.6882 1.00 1.8010 34.92 17 29.8803 5.94 1.6400 60.08 18 -155.7130 2.00 19 30.4340 5.81 1.4875 70.32 20 -100.4347 1.59 1.8061 40.93 21 46.2910 2.11 22(S) ∞ (D22) Notes: 1. In the translation of "6 -1656.3 * 1.00 1.7200 46.02", there seems to be an extra "*" in the original text. It's translated as it is for now, but it might be a formatting error in the original. 2. The unit information is not clear in the original text. For example, the values of "R", "D", etc. don't have specified units. In a proper patent context, these units should be clearly defined. The translation assumes the values are in some appropriate optical or dimensional units relevant to lens specifications. 23 99.4135 2.72 1.6204 60.29 24 -317.0281 0.27 25 51.7395 1.00 1.8850 30.16 26 27.3631 6.31 27 32.8360 4.31 1.7200 43.69 28 3964.4455 (D28) 29 -295.2690 3.45 1.7618 26.52 30 -47.8221 3.63 31 -37.3306 1.00 1.7725 49.62 32 41.6899 (D32) 33 -197.5318 4.59 1.7645 49.10 34 -33.3333 0.41 35 -36.7436 1.00 1.6129 37.00 36 -102.1283 (D36) 37 ∞ 1.60 1.5168 64.13 38∞2.00 Image plane ∞ [Lens group data] Group starting plane focal length 1 1 122.414 2 6 -31.567 3 14 44.395 4 23 63.962 5 29 -41.417 6 33 116.512 [Variable Interval Data] Infinity Close WMTWMT F 72.100 102.642 194.000 67.277 91.500 139.931 D5 2.000 19.657 39.000 2.000 19.656 39.000 D13 22.402 17.047 2.100 22.402 17.047 2.100 D22 11.833 8.529 8.879 14.761 11.609 10.640 D28 2.330 1.793 2.000 4.318 5.420 13.231 D32 6.916 13.556 16.771 2.000 6.848 3.780 D36 34.707 37.174 48.360 34.708 37.174 48.360

[0090] FIG. 2(A) is a diagram showing various aberrations of the variable magnification optical system of Example 1 when focusing at infinity in the wide-angle end state. FIG. 2(B) is a diagram showing various aberrations of the variable magnification optical system of Example 1 when focusing at infinity in the telephoto end state. FIG. 3(A) is a diagram showing various aberrations of the variable magnification optical system of Example 1 when focusing at close distances in the wide-angle end state. FIG. 3(B) is a diagram showing various aberrations of the variable magnification optical system of Example 1 when focusing at close distances in the telephoto end state. In each aberration diagram when focusing at infinity, FNO represents the F-number, and Y represents the image height. In each aberration diagram when focusing at close distances, NA represents the numerical aperture, and Y represents the image height. Note that spherical aberration diagrams show the F-number or numerical aperture value corresponding to the maximum aperture, astigmatism diagrams and distortion diagrams show the maximum value of image height, and coma diagrams show the value of each image height. "d" indicates the d-line (wavelength λ=587.6 nm), and "g" indicates the g-line (wavelength λ=435.8 nm). In the astigmatism diagrams, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. Note that the same symbols as in this embodiment are used in the aberration diagrams of the following embodiments, and redundant explanations will be omitted.

[0091] From the various aberration diagrams, it can be seen that the variable magnification optical system of Example 1 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close distances. As a result, even when focusing on close objects, good optical performance can be maintained and fluctuations in the angle of view during focusing can be reduced.

[0092] (Second Example) Example 2 will be described with reference to FIGS. 4, 5, 6, and Table 2. FIG. 4 shows the lens configuration of a variable magnification optical system ZL(2) according to Example 2. The variable magnification optical system ZL(2) is composed of, arranged in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, an aperture stop S, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having positive refractive power. An image plane I is located behind the sixth lens group G6.

[0093] In this embodiment, the fourth lens group G4 functions as the first focusing lens group GF1, and the fifth lens group G5 functions as the second focusing lens group GF2. That is, the first lens group G1, the second lens group G2, and the third lens group G3 form a front group GA that is fixed relative to the image plane I during focusing. The fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 form a rear group GB.

[0094] When transitioning from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 move along the locus indicated by the arrows in the lower part of Figure 4. This changes the spacing between adjacent lens groups, changing the imaging magnification (variation of magnification). The second lens group G2 is fixed and does not move during magnification. When focusing from an object at infinity to a close object, the fourth lens group G4 and the fifth lens group G5 move toward the image plane along different loci, as indicated by the arrows in the upper part of Figure 4.

[0095] The first lens group G1 is composed of a cemented positive lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side, and a positive meniscus lens L13 with a convex surface facing the object side. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side, a biconvex positive lens L22, a biconcave negative lens L23, and a biconcave negative lens L24. The third lens group G3 is composed of a biconvex positive lens L31, a cemented positive lens consisting of a negative meniscus lens L32 with a convex surface facing the object side and a biconvex positive lens L33, and a cemented positive lens consisting of a biconvex positive lens L34 and a biconcave negative lens L35.

[0096] The fourth lens group G4 is composed of a biconvex positive lens L41, a negative meniscus lens L42 with its convex surface facing the object side, and a biconvex positive lens L43. The fifth lens group G5 is composed of a positive meniscus lens L51 with its concave surface facing the object side, and a biconcave negative lens L52.

[0097] The sixth lens group G6 is composed of a positive meniscus lens L61 with its concave surface facing the object side, and a negative meniscus lens L62 with its concave surface facing the object side. A parallel plate PP is disposed in front of the image plane I.

[0098] Table 2 shows the values ​​of the specifications of the variable magnification optical system according to the second example. (Table 2) [Overall specifications] Magnification ratio=2.691 βF1t=0.32 βF1w=0.37 βF2t=3.37 βF2w=3.02 βBF2w=1.70 βBrw=0.56 ΔX1w=3.31 ΔX2w=5.65 fF2=-37.31 fAF2w=317.67 fBF2w=-85.60 fBrw=83.79 fAt=128.32 WMT f 72.10 105.00 194.00 FNO 4.10 4.10 4.10 2ω 33.64 22.98 12.30 Ymax 21.60 21.60 21.60 TL 167.32 186.91 205.27 BF 37.23 37.15 37.11 [Lens Specifications] Surface No. R D nd νd Object Surface ∞ 1 164.2107 1.00 1.7950 28.69 2 81.6916 5.44 1.5932 67.90 3 541.7710 0.10 4 64.6180 6.69 1.4970 81.61 5 1556.5885 (D5) 6 372.6279 1.00 1.7200 46.02 7 31.3950 0.58 8 32.1189 8.32 1.7847 25.64 9 -93.6053 0.11[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​ 23 76.0467 2.62 1.6700 47.23 24 -457.2754 0.13 25 93.1674 1.00 1.9020 25.10 26 31.2834 4.96 27 37.8776 3.87 1.8919 37.13 28 -3745.9359 (D28) 29 -78.4678 2.39 1.8467 23.78 30 -44.3923 6.95 31 -34.1777 1.00 1.7725 49.62 32 53.9288 (D32) 33 -268.3415 4.47 1.7550 52.32 34 -47.4541 0.10 35 -47.1341 1.00 1.6398 34.47 36 -52.0094 (D36) 37 ∞ 1.60 1.5168 63.88 38∞1.00 Image plane ∞ [Lens group data] Group starting plane focal length 1 1 116.302 2 6 -27.897 3 14 42.018 4 23 63.113 5 29 -37.306 6 33 83.793 [Variable Interval Data] Infinity Close WMTWMT F 72.100 105.000 194.000 66.728 93.257 133.735 D5 2.000 21.665 40.000 2.000 21.664 39.999 D13 18.985 14.768 2.100 18.986 14.768 2.100 D22 10.417 6.804 12.049 13.730 9.913 16.049 D28 3.010 2.588 4.969 5.345 6.845 18.954 D32 7.649 15.901 20.943 2.000 8.534 2.958 D36 35.170 35.093 35.120 35.170 35.094 35.120

[0099] FIG. 5(A) is a diagram showing various aberrations of the variable magnification optical system according to Example 2 when focusing at infinity in the wide-angle end state. FIG. 5(B) is a diagram showing various aberrations of the variable magnification optical system according to Example 2 when focusing at infinity in the telephoto end state. FIG. 6(A) is a diagram showing various aberrations of the variable magnification optical system according to Example 2 when focusing at a close distance in the wide-angle end state. FIG. 6(B) is a diagram showing various aberrations of the variable magnification optical system according to Example 2 when focusing at a close distance in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 2 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close distances. Therefore, even when focusing on a close-distance object, it is possible to reduce fluctuations in the angle of view during focusing while maintaining good optical performance.

[0100] (Third Example) Example 3 will be described with reference to FIGS. 7, 8, 9, and Table 3. FIG. 7 shows the lens configuration of a variable magnification optical system ZL(3) according to Example 3. The variable magnification optical system ZL(3) is composed of, arranged in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, an aperture stop S, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, a seventh lens group G7 having positive refractive power, and an eighth lens group G8 having negative refractive power. An image plane I is located behind the eighth lens group G8.

[0101] In this embodiment, the fifth lens group G5 functions as the first focusing lens group GF1, and the sixth lens group G6 functions as the second focusing lens group GF2. That is, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 form a front group GA that is fixed relative to the image plane I during focusing. The fifth lens group G5, the sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 form a rear group GB.

[0102] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the second lens group G2, the third lens group G3, the fifth lens group G5, the sixth lens group G6, and the eighth lens group G8 move along the locus indicated by the arrows in the lower part of Figure 7. This changes the spacing between adjacent lens groups, changing the imaging magnification (variation of magnification occurs). The first lens group G1, the fourth lens group G5, and the seventh lens group G7 are fixed and do not move during magnification. When focusing from an object at infinity to a close object, the fifth lens group G5 and the sixth lens group G6 move toward the image plane along different loci, as indicated by the arrows in the upper part of Figure 7.

[0103] The first lens group G1 consists of a cemented positive lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a biconvex positive lens L12, and a positive meniscus lens L13 with a convex surface facing the object side. The second lens group G2 consists of a negative meniscus lens L21 with a convex surface facing the object side, a cemented negative lens consisting of a biconcave negative lens L22 and a biconvex positive lens L23, and a biconcave negative lens L24. The third lens group G3 consists of a positive meniscus lens L31 with a concave surface facing the object side. The fourth lens group G4 consists of a biconvex positive lens L41 and a cemented positive lens consisting of a biconvex positive lens L42 and a biconcave negative lens L43.

[0104] The fifth lens group G5 is composed of a negative meniscus lens L51 with its convex surface facing the object side and a biconvex positive lens L52. The sixth lens group G6 is composed of a cemented negative lens consisting of a biconvex positive lens L61 and a biconcave negative lens L62.

[0105] The seventh lens group G7 is composed of a negative meniscus lens L71 with its convex surface facing the object side and a biconvex positive lens L72. The eighth lens group G8 is composed of a biconcave negative lens L81. A parallel plate PP is placed in front of the image plane I.

[0106] Table 3 shows the values ​​of the specifications of the variable magnification optical system according to the third example. (Table 3) [Overall specifications] Magnification ratio=2.708 βF1t=0.44 βF1w=0.38 βF2t=3.33 βF2w=4.29 βBF2w=1.78 βBrw=0.41 ΔX1w=1.52 ΔX2w=3.50 fF2=-47.48 fAF2w=208.32 fBF2w=-69.91 fBrw=117.19 fAt=174.21 WMT f 72.01 131.40 195.00 FNO 4.10 4.10 4.11 2ω 33.51 18.53 12.50 Ymax 21.60 21.60 21.60 TL 190.10 191.04 190.02 BF 37.67 42.70 46.99 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 90.2355 1.00 1.9500 29.37 2 60.7702 6.89 1.4970 81.64 3 -2196.2816 0.10 4 51.3148 10.01 1.4970 81.61 5 179.5132 (D5) 6 434.7890 1.49 1.8503 32.35 7 29.2567 6.81 8 -72.2823 1.00 1.4970 81.64 9 34.2350 7.14 2.0007 25.46 10 -94.3337 1.07 11 -56.0853 1.00 1.8061 33.34 12 165.1965 (D12) 13 -248.3690 3.29 1.7000 48.10 14 -52.8624 (D14) 15 89.5312 3.40 1.5168 64.13 16 -155.4452 0.10 17 36.4241 5.38 1.4875 70.32 18 -64.2538 1.00 2.0010 29.12 19 89.8281 1.77 20(S) ∞ (D20) 21 73.1095 1.00 1.7995 42.09 22 54.6786 0.10 23 51.1000 4.20 1.4970 81.64 24 -68.2409 (D24) 25 99.5195 4.17 1.7847 25.64 26 -37.0958 2.83 1.8485 43.79 27 30.2592 (D27) 28 278.5010 1.00 1.7174 29.57 29 51.0864 3.14 30 54.9583 6.33 1.7550 52.33 31 -46.7106 (D31) 32 -69.7842 1.00 1.8340 37.18 33 306.8074 (D33) 34 ∞ 1.60 1.5168 63.88 35 ∞ 1.00 Image plane∞ [Lens group data] Group starting plane focal length 1 1 96.608 2 6 -35.022 3 13 95.276 4 15 199.774 5 21 75.812 6 25 -47.481 7 28 51.745 8 32 -68.087 [Variable Interval Data] Infinity Close WMTWMT F 72.010 131.396 195.000 67.773 110.730 138.226 D5 2.678 23.180 35.000 2.678 23.180 35.000 D12 34.322 15.720 2.000 34.322 15.720 2.000 D14 2.100 0.200 2.100 2.100 0.200 2.100 D20 12.892 3.238 2.000 14.414 4.678 4.082 D24 3.423 5.836 2.248 5.401 11.525 13.631 D27 6.791 14.033 18.859 3.291 6.903 5.394 D31 14.888 9.803 5.493 14.889 9.803 5.493 D33 35.176 40.197 44.490 35.176 40.197 44.490

[0107] FIG. 8(A) is a diagram showing various aberrations of the variable magnification optical system according to Example 3 when focusing at infinity in the wide-angle end state. FIG. 8(B) is a diagram showing various aberrations of the variable magnification optical system according to Example 3 when focusing at infinity in the telephoto end state. FIG. 9(A) is a diagram showing various aberrations of the variable magnification optical system according to Example 3 when focusing at a close distance in the wide-angle end state. FIG. 9(B) is a diagram showing various aberrations of the variable magnification optical system according to Example 3 when focusing at a close distance in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 3 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close distances. Therefore, even when focusing on a close-distance object, it is possible to reduce fluctuations in the angle of view during focusing while maintaining good optical performance.

[0108] (Fourth Example) Example 4 will be described with reference to FIGS. 10, 11, 12, and Table 4. FIG. 10 shows the lens configuration of a variable magnification optical system ZL(4) according to Example 4. The variable magnification optical system ZL(4) is composed of, arranged in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, an aperture stop S located within the fifth lens group G5, a sixth lens group having negative refractive power, a seventh lens group G7 having positive refractive power, and an eighth lens group having negative refractive power. An image plane I is located behind the eighth lens group G8.

[0109] In this embodiment, the fifth lens group G5 functions as the first focusing lens group GF1, and the sixth lens group G6 functions as the second focusing lens group GF2. That is, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 form a front group GA that is fixed relative to the image plane I during focusing. The fifth lens group G5, the sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 form a rear group GB.

[0110] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1, the second lens group G2, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the eighth lens group G8 move along the locus indicated by the arrows in the lower part of Figure 10. This changes the spacing between adjacent lens groups, changing the imaging magnification (variation of magnification occurs). The second lens group G2 is fixed and does not move during magnification. When focusing from an object at infinity to a close object, the fifth lens group G5 and the sixth lens group G6 move toward the image plane along different loci, as indicated by the arrows in the upper part of Figure 10.

[0111] The first lens group G1 consists of a positive meniscus lens L11 with a convex surface facing the object side, and a cemented positive lens consisting of a negative meniscus lens L12 with a convex surface facing the object side and a positive meniscus lens L13 with a convex surface facing the object side. The second lens group G2 consists of a negative meniscus lens L21 with a convex surface facing the object side, a cemented positive lens consisting of a negative meniscus lens L22 with a convex surface facing the object side and a positive meniscus lens L23 with a convex surface facing the object side, and a biconcave negative lens L24. The third lens group G3 consists of a biconvex positive lens L31. The fourth lens group G4 consists of a biconvex positive lens L41 and a cemented positive lens consisting of a biconvex positive lens L42 and a biconcave negative lens L43.

[0112] The fifth lens group G5 is composed of a positive meniscus lens L51 with a concave surface facing the object side, an aperture stop S, and a biconvex positive lens L52. The sixth lens group G6 is composed of a cemented negative lens consisting of a positive meniscus lens L61 with a concave surface facing the object side and a biconcave negative lens L62.

[0113] The seventh lens group G7 is composed of a negative meniscus lens L71 with its convex surface facing the object side and a biconvex positive lens L72. The eighth lens group G8 is composed of a biconcave negative lens L81. A parallel plate PP is placed in front of the image plane I.

[0114] Table 4 shows the values ​​of the specifications of the variable magnification optical system according to the fourth example. (Table 4) [Overall specifications] Magnification ratio=2.708 βF1t=0.28 βF1w=0.37 βF2t=4.03 βF2w=7.39 βBF2w=1.86 βBrw=0.25 ΔX1w=0.32 ΔX2w=1.98 fF2=-40.33 fAF2w=300.05 fBF2w=-62.42 fBrw=91.39 fAt=281.46 WMT f 72.01 131.83 195.00 FNO 4.10 4.10 4.10 2ω 33.18 18.31 12.41 Ymax 21.60 21.60 21.60 TL 190.10 196.42 202.79 BF 37.81 43.31 52.83 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 79.0842 5.95 1.4875 70.32 2 264.5438 0.10 3 76.9959 1.00 1.6200 36.40 4 48.0525 8.95 1.4970 81.64 5 237.0010 (D5) 6 212.5326 1.00 1.9537 32.32 7 35.1692 2.15 8 52.5161 1.00 1.5935 67.00 9 25.5276 6.40 1.9630 24.11 10 56.3526 4.91 11 -81.6868 1.00 1.7550 52.32 12 117.0223 (D12) 13 229.9072 3.32 2.0007 25.46 14 -149.7696 (D14) 15 108.7396 4.23 1.5186 69.89 16 -81.0701 0.10 17 44.1054 6.79 1.4971 81.56 18 -43.2444 1.00 1.9229 20.88 19 208.7919 6.96 20(S) ∞ (D20) 21 -123.9327 2.46 2.0027 19.32 22 -59.8965 0.10 23 76.0756 2.78 1.4971 81.56 24 -9120.5459 (D24) 25 -400.9124 3.38 1.7847 25.64 26 -35.1385 1.00 1.7440 44.90 27 31.1285 (D27) 28 86.5286 1.00 1.8513 40.10 29 46.8866 3.27 30 51.7194 5.85 1.6976 55.51 31 -51.0112 (D31) 32 -83.2716 1.00 1.7296 54.07 33 200.0000 (D33) 34 ∞ 1.60 1.5168 63.88 35∞1.00 Image plane ∞ [Lens group data] Group starting plane focal length 1 1 127.643 2 6 -32.627 3 13 91.026 4 15 104.204 5 21 64.670 6 25 -40.331 7 28 51.908 8 32 -80.459 [Variable Interval Data] Infinity Close WMTWMT F 72.100 105.000 194.000 66.728 93.257 133.735 D5 2.000 22.798 35.000 2.000 22.798 35.000 D12 22.209 6.752 2.000 22.209 6.752 2.000 D14 19.979 9.878 2.100 19.979 9.878 2.100 D20 8.931 3.262 3.460 9.340 4.223 4.748 D24 2.155 10.230 12.617 3.818 15.216 21.949 D27 4.073 11.769 16.961 2.000 5.820 6.341 D31 17.106 11.180 2.000 17.106 11.181 2.000 D33 35.348 41.260 50.363 35.442 41.365 50.363

[0115] FIG. 11(A) is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focusing at infinity in the wide-angle end state. FIG. 11(B) is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focusing at infinity in the telephoto end state. FIG. 12(A) is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focusing at a close distance in the wide-angle end state. FIG. 12(B) is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focusing at a close distance in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system of Example 4 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close distances. Therefore, even when focusing on a close-distance object, good optical performance can be maintained and fluctuations in the angle of view during focusing can be reduced.

[0116] (Fifth Example) Example 5 will be described with reference to FIGS. 13, 14, 15, and Table 5. FIG. 13 shows the lens configuration of a variable magnification optical system ZL(5) according to Example 5. The variable magnification optical system ZL(5) is composed of, arranged in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, an aperture stop S located within the third lens group G3, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power. An image plane I is located behind the fifth lens group G5.

[0117] In this embodiment, the fourth lens group G4 functions as the focusing lens group GF. That is, the first lens group G1, the second lens group G2, and the third lens group G3 form a front group GA that is fixed relative to the image plane during focusing. The fourth lens group G4 and the fifth lens group G5 form a rear group GB.

[0118] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move along the locus indicated by the arrows in the lower part of Figure 13. This changes the spacing between adjacent lens groups, changing the imaging magnification (changing magnification). The second lens group G2 is fixed and does not move during magnification. When focusing from an object at infinity to a close object, the fourth lens group G4 moves toward the image plane, as indicated by the arrow in the upper part of Figure 13.

[0119] The first lens group G1 is composed of a cemented lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a biconvex positive lens L12, and a positive meniscus lens L13 with a convex surface facing the object side. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side, a biconvex positive lens L22, a biconcave negative lens L23, and a negative meniscus lens L24 with a concave surface facing the object side. The third lens group G3 is composed of a biconvex positive lens L31, a cemented lens of a negative meniscus lens L32 with its convex surface facing the object side and a biconvex positive lens L33, a cemented lens of a biconvex positive lens L34 and a biconcave negative lens L35, an aperture stop S, a positive meniscus lens L36 with its concave surface facing the object side, a negative meniscus lens L37 with its convex surface facing the object side, and a positive meniscus lens L38 with its convex surface facing the object side.

[0120] The fourth lens group G4 is composed of a positive meniscus lens L41 with a concave surface facing the object side and a biconcave negative lens L42. The fifth lens group G5 is composed of a positive meniscus lens L51 with a concave surface facing the object side and a positive meniscus lens L52 with a concave surface facing the object side. A parallel plate PP is disposed in front of the image plane I.

[0121] Table 5 shows the values ​​of the specifications of the variable magnification optical system according to the fifth example. (Table 5) [Overall specifications] Magnification ratio=2.701 βF2w=2.19 βBF2w=1.45 βBrw=0.66 fF2=-42.46 fAF2w=109.06 fBF2w=-126.62 fBrw=78.93 WMT f 72.10 111.59 194.00 FNO 4.10 4.10 4.11 2ω 33.07 21.21 12.29 Ymax 21.60 21.60 21.60 TL 170.62 194.98 204.57 BF 26.33 26.34 26.41 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 153.0418 1.00 1.7950 28.69 2 81.289 8.42 1.5932 67.90 3 -319.7357 0.10 4 51.972 5.48 1.4970 81.61 5 68.9954 (D5) 6 102.4213 1.00 1.7570 47.82 7 28.2387 2.64 8 30.1162 7.69 1.8052 25.46 9 -120.6517 0.10 10 -275.1702 1.00 1.7725 49.62 11 35.0678 5.57 12 -34.6195 1.00 1.8588 30.00 13 -166.953 (D13) 14 432.4033 3.78 1.6385 55.38 15 -58.0996 0.10 16 43.8656 1.56 1.8010 34.92 17 26.9447 5.92 1.6400 60.19 18 -1604.8469 0.10 19 30.6714 6.26 1.4875 70.32 20 -65.1694 1.60 1.8061 40.97 21 45.6195 2.00 22(S) ∞ 10.68 23 -198.2201 2.52 1.6850 49.22 24 -61.4817 0.43 25 63.3773 1.00 1.9020 25.10 26 29.9748 8.62 27 42.2467 3.43 1.8919 37.13 28 313.3184 (D28) 29 -59.9421 2.43 1.8467 23.78 30 -37.5377 8.57 31 -28.2576 1.00 1.8061 40.93 32 139.4046 (D32) 33 -295.2748 3.37 1.6700 51.72 34 -81.284 0.10 35 -500.48 3.53 1.7283 28.41 36 -89.2134 (D36) 37 ∞ 1.60 1.5168 63.88 38∞1.00 Image plane ∞ [Lens group data] Group starting plane focal length 1 1 138.365 2 6 -33.239 3 14 41.795 4 29 -42.455 5 33 78.928 [Variable Interval Data] Infinity Close WMTWMT F 72.100 111.593 194.000 67.313 97.936 129.512 D5 6.128 30.481 40.000 6.128 30.481 40.000 D13 25.026 19.401 2.100 25.025 19.401 2.100 D28 3.317 1.297 12.305 6.664 8.143 32.524 D32 8.282 15.926 22.219 4.934 9.079 2.000 D36 24.274 24.285 24.357 24.275 24.286 24.357

[0122] FIG. 14(A) is a diagram showing various aberrations of the variable magnification optical system of Example 5 when focusing at infinity in the wide-angle end state. FIG. 14(B) is a diagram showing various aberrations of the variable magnification optical system of Example 5 when focusing at infinity in the telephoto end state. FIG. 15(A) is a diagram showing various aberrations of the variable magnification optical system of Example 5 when focusing at close range in the wide-angle end state. FIG. 15(B) is a diagram showing various aberrations of the variable magnification optical system of Example 5 when focusing at close range in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system of Example 5 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close range. Therefore, even when focusing on close-distance objects, it is possible to reduce fluctuations in the angle of view during focusing while maintaining good optical performance.

[0123] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below: This table shows the values ​​corresponding to each of the conditional expressions (1) to (19) for all the examples (Examples 1 to 5). Conditional expression (1) 0.25<βF1t / βF1w<2.00 Conditional expression (2) 0.25<βF2w / βF2t<2.00 Conditional expression (3) 0.01<βF1w / βF2w<0.25 Conditional expression (4) 0.10<ΔX1w / ΔX2w<0.75 Conditional expression (5) 0.001<1 / fAt<0.020 Condition (6) 0.001<1 / fAF2w<0.015 Condition (7) 0.35 <fF2 / fBF2w<0.75 Condition (8) -2.00 <fBF2w / fBrw<-0.15 Condition (9) 0.10<βBF2w / βF2w<0.80 Conditional expression (10) 0.05<βBrw / βBF2w<0.50 Condition (11) 0.35 <fF2 / fBF2w<0.75 Condition (12) -2.00 <fBF2w / fBrw<-0.15 Condition (13) 0.10<βBF2w / βF2w<0.80 Conditional expression (14) 0.05<βBrw / βBF2w<0.50 Condition (15) 0.001<1 / fAF2w<0.015 Conditional expression (16) 0.15<(ftinf-ftmod) / ftinf<0.40 Condition (17) 0.35 <STw / TLw<0.65 Condition (18) 0.04 <Bft / TLt<0.35 Condition (19) 0.25 <Bfw / fw<0.70

[0124] [Conditional expression corresponding value] Conditional Expression 1st Example 2nd Example 3rd Example 4th Example 5th Example (1) 0.944 0.862 1.152 0.754 - (2) 0.826 0.896 1.290 1.832 0.868 (3) 0.163 0.124 0.089 0.050 - (4) 0.596 0.587 0.435 0.160 - (5) 0.009 0.008 0.006 0.004 - (6) 0.004 0.003 0.005 0.003 - (7) 0.568 0.436 0.679 0.646 - (8) -0.626 -1.022 -0.597 -0.683 - (9) 0.677 0.562 0.413 0.251 - (10) 0.391 0.331 0.233 0.135 - (11) 0.568 0.436 0.679 0.646 0.335 (12) -0.626 -1.022 -0.597 -0.683 -1.604 (13) 0.677 0.562 0.413 0.251 0.661 (14) 0.391 0.331 0.233 0.135 0.457 (15) 0.004 0.003 0.005 0.003 0.009 (16) 0.279 0.311 0.291 0.274 0.332 (17) 0.526 0.522 0.524 0.479 0.493 (18) 0.251 0.181 0.247 0.260 0.129 (19) 0.524 0.516 0.523 0.525 0.365

[0125] According to each of the above embodiments, it is possible to realize a variable magnification optical system with little fluctuation in the angle of view during focusing.

[0126] The above-described examples are merely illustrative examples of the present invention, and the present invention is not limited to these.

[0127] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the variable magnification optical system of this embodiment.

[0128] Although five-group, six-group, and eight-group configurations have been shown as examples of the variable magnification optical system of this embodiment, the present application is not limited to these, and variable magnification optical systems with other group configurations (e.g., seven-group, nine-group, etc.) can also be configured. Specifically, a lens or lens group may be added to the most object-side or most image-plane-side of the variable magnification optical system of this embodiment. Note that a lens group refers to a portion having at least one lens separated by an air gap that changes when the magnification is changed.

[0129] A single lens group, multiple lens groups, or a partial lens group may be moved in the optical axis direction to function as a focusing lens group that focuses from an object at infinity to a close object. The focusing lens group can also be used for autofocusing, and is suitable for driving a motor (using an ultrasonic motor, etc.) for autofocusing.

[0130] The lens group or partial lens group may be moved so as to have a component in a direction perpendicular to the optical axis, or may be rotated (oscillated) in a plane including the optical axis, to serve as an image stabilization lens group that corrects image blur caused by camera shake.

[0131] The lens surface may be spherical, flat, or aspherical. Spherical or flat lens surfaces are preferred because they facilitate lens processing and assembly adjustment, and prevent degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, they are preferred because they minimize degradation of imaging performance even when the image plane is misaligned.

[0132] If the lens surface is aspherical, the aspherical surface may be any of the following: a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, or a hybrid aspherical surface in which a resin is formed into an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, or the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0133] It is preferable that the aperture stop be disposed in the third or fourth lens group, but it is also possible to use the lens frame to perform the role of the aperture stop instead of providing a member serving as the aperture stop.

[0134] Each lens surface may be coated with an anti-reflection coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high-contrast optical performance. [Explanation of symbols]

[0135] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group G7 7th lens group G8 8th lens group I Image plane S Aperture stop

Claims

[Claim 1] It consists of a front group and a rear group, arranged in order from the object side along the optical axis, the front group includes, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power; the rear group includes a first focusing lens group having positive refractive power and arranged closest to the object side of the rear group, a second focusing lens group having negative refractive power and arranged on the image plane side of the first focusing lens group, and a lens group having positive refractive power and arranged on the image plane side of the second focusing lens group, When changing magnification, the spacing between adjacent lens groups changes, and the lens group closest to the image plane moves along the optical axis. When focusing from an object at infinity to an object at a close distance, the first focusing lens group and the second focusing lens group move along different loci along the optical axis, A variable magnification optical system that satisfies the following condition: 0.25<βF1t / βF1w<2.00 0.25<βF2w / βF2t<2.00 where βF1t is the magnification of the first focusing lens group when focused on infinity in the telephoto end state. βF1w: Magnification of the first focusing lens group when focused on infinity in the wide-angle end state βF2t: Magnification of the second focusing lens group when focused on infinity in the telephoto end state βF2w: Magnification of the second focusing lens group when focused on infinity in the wide-angle end state

Images