Zoom optical system and optical device

Abstract

To provide a zoom optical system capable of suppressing variation in view angle while focusing.SOLUTION: A zoom optical system ZL provided herein consists of a leading lens group GA having negative refractive power and a succeeding lens group GB having positive refractive power arranged in order from the object side along an optical axis, the leading lens group GA consisting of a negative first lens group G1, and the succeeding lens group GB consisting of a positive second lens group G2, a positive third lens group G3, a positive fourth lens group G4, and a negative fifth lens group G5. The second lens group G2 is a focusing group, and the third through fifth lens groups G3-G5 are located on the image side of the focusing group. The first lens group G1 consists of four lenses, and the succeeding lens group has at least one lens that satisfies the following conditional expression: 75.0<νd. The zoom optical system further satisfies the following conditional expressions: 1.80<fF / fBaw, Fnow<3.40, -5.50<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-1.50.SELECTED DRAWING: Figure 7

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] Japanese Patent Application Publication No. 2018-13685 Summary of the Invention

[0004] A first variable magnification optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a leading lens group having negative refractive power and a trailing lens group having positive refractive power, wherein the distance between the leading lens group and the trailing lens group changes during magnification variation, and the trailing lens group has a focusing group and an image-side group arranged closer to the image than the focusing group, and wherein, during focusing from an object at infinity to an object at a close distance, the focusing group moves toward the image side along the optical axis, and the following conditional expression is satisfied: 1.80 <fF / fBaw FNew<3.40 where fF is the focal length of the focusing group fBaw: the focal length of the lens group in the wide-angle end state, which is made up of lenses arranged on the image side of the focusing group in the subsequent lens group F Now: F number of the variable magnification optical system in the wide-angle end state

[0005] A second variable magnification optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a leading lens group having negative refractive power and a trailing lens group having positive refractive power, wherein the distance between the leading lens group and the trailing lens group changes during magnification variation, and the trailing lens group has a focusing group and an image-side group arranged closer to the image side than the focusing group, and wherein, during focusing from an object at infinity to an object at a close distance, the focusing group moves toward the image side along the optical axis, and the following conditional expression is satisfied: 2.00<βFw / (-βBaw)<15.00 FNew<3.40 where βFw is the magnification of the focusing group in the wide-angle end state. βBaw: Magnification in the wide-angle end state of the lens group consisting of lenses arranged on the image side of the focusing group in the subsequent lens group F Now: F number of the variable magnification optical system in the wide-angle end state

[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] FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system according to Example 6. [Figure 17] 17A and 17B are diagrams showing various aberrations of the variable magnification optical system according to Example 6 when focused on infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 18] 18A and 18B are diagrams showing various aberrations of the variable magnification optical system according to Example 6 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 19] FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system according to Example 7. [Figure 20]20A and 20B are diagrams showing various aberrations of the variable magnification optical system according to Example 7 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 21] 21A and 21B are diagrams showing various aberrations of the variable magnification optical system according to Example 7 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 22] 1 is a diagram showing the configuration of a camera equipped with a variable magnification optical system according to each embodiment. [Figure 23] 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. 22. As shown in FIG. 22, this camera 1 is composed of a main body 2 and a photographic lens 3 attached to the main body 2. The main body 2 is equipped with an image sensor 4, a main 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 the variable magnification optical system (zoom lens) ZL according to the first embodiment is composed of, arranged in order from the object side along the optical axis, a leading lens group GA having negative refractive power and a trailing lens group GB having positive refractive power. During magnification variation, the distance between the leading lens group GA and the trailing lens group GB changes. The trailing lens group GB has a focusing group GF and an image-side group GC arranged closer to the image than the focusing group GF. During focusing from an object at infinity to a close-distance object, the focusing group GF moves toward the image side along the optical axis.

[0011] With the above-described configuration, the variable magnification optical system ZL according to the first embodiment satisfies the following conditional expressions (1-1) and (2). 1.80 <fF / fBaw ···(1-1) FNew<3.40 (2) where fF is the focal length of the focusing group GF fBaw: the focal length of the lens group GB at the wide-angle end, which is made up of lenses located on the image side of the focusing group GF. F Now: F number of the variable magnification optical system ZL at the wide-angle end

[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. Furthermore, the variable magnification optical system ZL according to the first embodiment may be the variable magnification optical system ZL(5) shown in FIG. 13, the variable magnification optical system ZL(6) shown in FIG. 16, or the variable magnification optical system ZL(7) shown in FIG. 19. In the first embodiment, for convenience of explanation, the lens group in the subsequent lens group GB that is composed of lenses arranged on the image side of the focusing group GF may be referred to as the image-side lens group GBa.

[0013] Conditional expression (1-1) defines an appropriate relationship between the focal length of the focusing group GF and the focal length of the image-side lens group GBa (the lens group consisting of the lenses in the subsequent lens group GB that are arranged on the image side of the focusing group GF) in the wide-angle end state. Note that the focal length of the image-side lens group GBa in the wide-angle end state indicates the value when focusing on an object at infinity. Satisfying conditional expression (1-1) makes it possible to reduce fluctuations in the angle of view during focusing.

[0014] If the value corresponding to conditional expression (1-1) 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 (1-1) to 1.90, 2.00, 2.10, 2.20, 2.25, 2.30, or even 2.35, the effects of this embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (1-1) to 10.00, 8.00, or even 6.00, the effects of this embodiment can be further ensured.

[0015] Conditional expression (2) defines an appropriate range for the F-number of the variable magnification optical system ZL in the wide-angle end state. Note that the F-number of the variable magnification optical system ZL in the wide-angle end state indicates the maximum F-number when focusing on an object at infinity. By satisfying conditional expression (2), it is possible to ensure the brightness of the optical system while minimizing fluctuations in the angle of view when focusing.

[0016] If the value corresponding to conditional expression (2) is outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing while ensuring the brightness of the optical system. By setting the upper limit of conditional expression (2) to 3.20, or even 3.00, the effects of this embodiment can be further ensured.

[0017] Next, a variable magnification optical system according to a second embodiment will be described. A variable magnification optical system ZL(1), which is an example of a variable magnification optical system (zoom lens) ZL according to the second embodiment, is composed of, as shown in FIG. 1, a leading lens group GA having negative refractive power and a trailing lens group GB having positive refractive power, arranged in order from the object side along the optical axis. During magnification variation, the distance between the leading lens group GA and the trailing lens group GB changes. The trailing lens group GB has a focusing group GF and an image-side group GC arranged closer to the image than the focusing group GF. During focusing from an object at infinity to a close-distance object, the focusing group GF moves toward the image side along the optical axis.

[0018] With the above-described configuration, the variable magnification optical system ZL according to the second embodiment satisfies the following conditional expressions (1-2) and (2). 2.00<βFw / (-βBaw)<15.00 (1-2) FNew<3.40 (2) βFw: Magnification of the focusing group GF at the wide-angle end βBaw: Magnification in the wide-angle end state of the lens group consisting of the lens arranged on the image side of the focusing group GF in the subsequent lens group GB F Now: F number of the variable magnification optical system ZL at the wide-angle end

[0019] 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, or the variable magnification optical system ZL(4) shown in FIG. 10. Furthermore, the variable magnification optical system ZL according to the second embodiment may be the variable magnification optical system ZL(5) shown in FIG. 13, the variable magnification optical system ZL(6) shown in FIG. 16, or the variable magnification optical system ZL(7) shown in FIG. 19. In the second embodiment, for convenience of explanation, the lens group in the subsequent lens group GB that is composed of lenses arranged on the image side of the focusing group GF may be referred to as the image-side lens group GBa.

[0020] Conditional expression (1-2) defines an appropriate relationship between the magnification of the focusing group GF in the wide-angle end state and the magnification of the image-side lens group GBa (a lens group consisting of lenses in the subsequent lens group GB that are arranged on the image side of the focusing group GF) in the wide-angle end state. Note that the magnification of the focusing group GF in the wide-angle end state indicates the value when focusing on an object at infinity. The magnification of the image-side lens group GBa in the wide-angle end state indicates the value when focusing on an object at infinity. Satisfying conditional expression (1-2) can reduce fluctuations in the angle of view when focusing.

[0021] If the value corresponding to conditional expression (1-2) 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 (1-2) to 2.15, 2.30, 2.50, 2.80, 3.00, 3.30, 3.50, 3.80, 4.00, 4.50, 5.00, or even 5.50. Furthermore, the effects of this embodiment can be further ensured by setting the upper limit of conditional expression (1-2) to 14.50, 14.00, 13.50, 13.00, 12.00, 11.00, 10.00, 9.50, 9.00, 8.50, or even 8.00.

[0022] Conditional expression (2) defines an appropriate range for the F-number of the variable magnification optical system ZL in the wide-angle end state. Note that the F-number of the variable magnification optical system ZL in the wide-angle end state indicates the maximum F-number when focusing on an object at infinity. By satisfying conditional expression (2), it is possible to ensure the brightness of the optical system while reducing fluctuations in the angle of view when focusing.

[0023] If the value corresponding to conditional expression (2) is outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing while ensuring the brightness of the optical system. By setting the upper limit of conditional expression (2) to 3.20, or even 3.00, the effects of this embodiment can be made even more certain.

[0024] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expressions (3) and (4). 1.50<βFw<15.00 (3) 0.00 <fBaw / fCw<1.00 ···(4) βFw: Magnification of the focusing group GF at the wide-angle end fCw: focal length of the image-side group GC at the wide-angle end fBaw: the focal length of the lens group GB at the wide-angle end, which is made up of lenses located on the image side of the focusing group GF.

[0025] Conditional expression (3) defines an appropriate range for the magnification of the focusing group GF in the maximum wide-angle state. Note that the magnification of the focusing group GF in the maximum wide-angle state indicates the value when focusing on an object at infinity. By satisfying conditional expression (3), fluctuations in the angle of view during focusing can be reduced.

[0026] 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 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 2.00, 2.40, 2.50, 2.55, 2.60, or even 2.65, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (3) to 14.50, 13.50, 12.50, 11.00, 10.00, 9.00, 8.00, 7.00, or even 6.00, the effects of each embodiment can be further ensured.

[0027] Conditional expression (4) defines an appropriate relationship between the focal length of the image-side lens group GBa (a lens group consisting of lenses in the subsequent lens group GB that are arranged closer to the image than the focusing group GF) in the wide-angle end state and the focal length of the image-side lens group GC in the wide-angle end state. Note that the focal length of the image-side lens group GBa in the wide-angle end state indicates the value when focusing on an object at infinity. The focal length of the image-side lens group GC in the wide-angle end state indicates the value when focusing on an object at infinity. Satisfying conditional expression (4) makes it possible to reduce fluctuations in the angle of view during focusing.

[0028] 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. By setting the lower limit of conditional expression (4) to 0.20, 0.35, 0.45, 0.50, 0.55, 0.58, or even 0.60, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (4) to 0.99, 0.95, 0.93, 0.90, or even 0.88, the effects of each embodiment can be more reliably achieved.

[0029] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (5). 0.60 <Bfw / fw<4.00 ···(5) where fw is the focal length of the variable magnification optical system ZL at the wide-angle end Bfw: Back focus of variable magnification optical system ZL in the wide-angle end state

[0030] Conditional expression (5) defines an appropriate range for the back focus of the variable magnification optical system ZL in the wide-angle end state. Note that the focal length of the variable magnification optical system ZL in the wide-angle end state indicates the value when focused on an object at infinity. By satisfying conditional expression (5), various aberrations such as coma in the wide-angle end state can be effectively corrected.

[0031] If the value corresponding to conditional expression (5) falls outside the above range, it becomes difficult to correct various aberrations, such as coma aberration, in the wide-angle end state. It also becomes difficult to ensure sufficient peripheral light intensity. By setting the lower limit of conditional expression (5) to 0.70, 0.73, 0.75, 0.85, 0.93, 1.00, 1.10, or even 1.15, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (5) to 3.50, 3.00, 2.80, 2.50, 2.20, 2.00, 1.80, or even 1.60, the effects of each embodiment can be further ensured.

[0032] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (6). 0.05 <Bfw / TLw<0.22 ···(6) TLw: total length of variable magnification optical system ZL in wide-angle end state Bfw: Back focus of variable magnification optical system ZL in the wide-angle end state

[0033] Conditional expression (6) defines an appropriate relationship between the overall length of the variable magnification optical system ZL in the wide-angle end state and the back focus of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (6), various aberrations, such as spherical aberration, in the wide-angle end state can be effectively corrected.

[0034] If the value corresponding to conditional expression (6) falls outside the above range, it becomes difficult to correct various aberrations, such as spherical aberration, in the wide-angle end state. By setting the lower limit of conditional expression (6) to 0.06, 0.07, 0.10, 0.12, or even 0.13, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (6) to 0.20, 0.18, or even 0.17, the effects of each embodiment can be more reliably achieved.

[0035] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that an aperture stop S is disposed in the subsequent lens group GB and that the following conditional expression (7) is satisfied: 0.40 <STLw / TLw<0.70 ···(7) TLw: total length of variable magnification optical system ZL in wide-angle end state STLw: The distance on the optical axis from the lens surface closest to the object side of the variable magnification optical system ZL to the aperture stop S in the wide-angle end state

[0036] Conditional expression (7) defines an appropriate relationship between the overall length of the variable magnification optical system ZL in the wide-angle end state and the distance on the optical axis from the lens surface of the variable magnification optical system ZL closest to the object in the wide-angle end state to the aperture stop S. By satisfying conditional expression (7), distortion and curvature of field can be effectively corrected.

[0037] If the value corresponding to conditional expression (7) falls outside the above range, it becomes difficult to correct distortion and curvature of field. By setting the lower limit of conditional expression (7) to 0.42, 0.44, 0.48, 0.50, 0.52, or even 0.55, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (7) to 0.68, 0.66, 0.64, or even 0.62, the effects of each embodiment can be more reliably achieved.

[0038] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (8). 0.00 <TLt / TLw<1.00 ···(8) TLw: total length of variable magnification optical system ZL in wide-angle end state TLt: total length of variable magnification optical system ZL in the telephoto end state

[0039] Conditional expression (8) defines an appropriate relationship between the overall 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 telephoto end state. By satisfying conditional expression (8), the overall length of the variable magnification optical system ZL in the telephoto end state is shorter than the overall length of the variable magnification optical system ZL in the wide-angle end state.

[0040] The effects of each embodiment can be further ensured by setting the lower limit of conditional expression (8) to 0.25, 0.40, 0.50, 0.60, 0.70, 0.75, 0.80, or even 0.85. Also, the effects of each embodiment can be further ensured by setting the upper limit of conditional expression (8) to 0.98 or even 0.97.

[0041] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that the leading lens group GA includes the first lens group G1 arranged closest to the object side, and satisfy the following conditional expression (9). 1.00<(-f1) / fw<1.80 (9) where f1 is the focal length of the first lens group G1 fw: focal length of variable magnification optical system ZL at wide-angle end

[0042] Conditional expression (9) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the variable magnification optical system ZL in the wide-angle end state. Note that the focal length of the variable magnification optical system ZL in the wide-angle end state indicates the value when focused on an object at infinity. By satisfying conditional expression (9), various aberrations such as spherical aberration and coma in the wide-angle end state can be effectively corrected.

[0043] If the value corresponding to conditional expression (9) falls outside the above range, it becomes difficult to correct various aberrations, such as spherical aberration and coma, in the wide-angle end state. By setting the lower limit of conditional expression (9) to 1.05, 1.10, 1.15, 1.20, or even 1.25, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (9) to 1.75, 1.70, 1.65, 1.60, 1.55, or even 1.50, the effects of each embodiment can be further ensured.

[0044] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that the leading lens group GA includes the first lens group G1 arranged closest to the object side, and satisfy the following conditional expression (10). 0.42<(-f1) / ft<1.20 (10) where f1 is the focal length of the first lens group G1 ft: focal length of variable magnification optical system ZL at telephoto end

[0045] Conditional expression (10) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the variable magnification optical system ZL in the telephoto end state. Note that the focal length of the variable magnification optical system ZL in the telephoto end state indicates the value when focused on an object at infinity. By satisfying conditional expression (10), various aberrations such as spherical aberration and coma in the telephoto end state can be effectively corrected.

[0046] If the value corresponding to conditional expression (10) falls outside the above range, it becomes difficult to correct various aberrations, such as spherical aberration and coma, in the telephoto end state. By setting the lower limit of conditional expression (10) to 0.45, 0.48, 0.50, 0.52, 0.55, 0.58, 0.60, or even 0.62, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (10) to 1.15, 1.10, 1.05, 1.00, 0.98, or even 0.95, the effects of each embodiment can be further ensured.

[0047] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (11). -3.00<(rL1R2+rL1R1) / (rL1R2-rL1R1)<-0.80 ···(11) where rL1R1 is the radius of curvature of the lens surface on the object side of the lens arranged closest to the object side in the variable magnification optical system ZL. rL1R2: Radius of curvature of the image-side lens surface of the lens located closest to the object in the variable magnification optical system ZL

[0048] Condition (11) defines an appropriate shape factor for the lens located closest to the object in the variable magnification optical system ZL. By satisfying condition (11), distortion can be effectively corrected.

[0049] If the value corresponding to conditional expression (11) falls outside the above range, it becomes difficult to correct distortion. By setting the lower limit of conditional expression (11) to -2.80, -2.50, -2.30, -2.00, or even -1.80, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (11) to -0.85, -0.90, -0.95, or even -1.00, the effects of each embodiment can be more reliably achieved.

[0050] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (12). -5.50<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-1.50 ···(12) where rL2R1 is the radius of curvature of the object-side lens surface of the second lens element from the object side of the variable magnification optical system ZL. rL2R2: Radius of curvature of the image-side lens surface of the second lens element from the object side of the variable magnification optical system ZL

[0051] Conditional expression (12) defines the appropriate shape factor for the second lens element from the object side of the variable magnification optical system ZL. Satisfying conditional expression (12) enables good correction of coma and curvature of field.

[0052] If the value corresponding to conditional expression (12) falls outside the above range, it becomes difficult to correct coma and curvature of field. By setting the lower limit of conditional expression (12) to -5.40, -5.30, -5.15, -5.00, -4.50, -4.25, -4.00, -3.80, or even -3.50, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (12) to -1.60, -1.70, -1.75, -1.80, or even -1.85, the effects of each embodiment can be further ensured.

[0053] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (13). -0.50<(rL3R2+rL3R1) / (rL3R2-rL3R1)<0.50 ···(13) where rL3R1 is the radius of curvature of the object-side lens surface of the third lens element from the object side of the variable magnification optical system ZL. rL3R2: Radius of curvature of the image-side lens surface of the third lens element from the object side of the variable magnification optical system ZL

[0054] Condition (13) defines an appropriate shape factor for the third lens element counting from the object side of the variable magnification optical system ZL. Satisfying condition (13) enables good correction of coma.

[0055] If the value corresponding to conditional expression (13) falls outside the above range, it becomes difficult to correct coma. By setting the lower limit of conditional expression (13) to -0.45, -0.40, -0.38, -0.35, or even -0.33, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (13) to 0.48, 0.45, 0.43, 0.40, or even 0.38, the effects of each embodiment can be more reliably achieved.

[0056] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (14). 1.50<|(rLeR2+rLeR1) / (rLeR2-rLeR1)| ···(14) where rLeR1 is the radius of curvature of the object-side lens surface of the lens located closest to the image side in the variable magnification optical system ZL. rLeR2: Radius of curvature of the image-side lens surface of the lens located closest to the image in the variable magnification optical system ZL

[0057] Conditional expression (14) defines an appropriate shape factor for the lens element located closest to the image side in the variable magnification optical system ZL. By satisfying conditional expression (14), curvature of field and distortion can be effectively corrected.

[0058] If the value corresponding to conditional expression (14) is outside the above range, it becomes difficult to correct curvature of field and distortion. By setting the lower limit of conditional expression (14) to 1.80, 2.00, or even 2.30, the effects of each embodiment can be further ensured.

[0059] In the variable magnification optical system ZL according to the first and second embodiments, the leading lens group GA preferably includes a first lens group G1 disposed closest to the object, and when varying magnification from the wide-angle end state to the telephoto end state, the first lens group G1 preferably moves toward the image along the optical axis, thereby making the overall length of the variable magnification optical system ZL in the telephoto end state shorter than the overall length of the variable magnification optical system ZL in the wide-angle end state.

[0060] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable for the subsequent lens group GB to have at least one aspherical lens, which allows for excellent correction of field curvature and distortion.

[0061] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that the subsequent lens group GB has at least one lens that satisfies the following conditional expression (15): In the first and second embodiments, the lens that satisfies the conditional expression (15) is sometimes referred to as a specific lens in order to distinguish it from other lenses. 75.0<νd (15) νd: Abbe number of a particular lens

[0062] Condition (15) defines the anomalous dispersion of the glass material of a specific lens in the subsequent lens group GB. By satisfying condition (15), lateral chromatic aberration can be effectively corrected.

[0063] If the value corresponding to conditional expression (15) is outside the above range, it becomes difficult to effectively correct lateral chromatic aberration. By setting the lower limit of conditional expression (15) to 78.0, 80.0, or even 81.0, the effects of each embodiment can be further ensured.

[0064] Next, referring to FIG. 23, a manufacturing method for the variable magnification optical system ZL according to the first embodiment will be outlined. First, a leading lens group GA having negative refractive power and a trailing lens group GB having positive refractive power are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is made in which the distance between the leading lens group GA and the trailing lens group GB changes during magnification (Step ST2). Next, a focusing group GF and an image-side group GC located closer to the image than the focusing group GF are arranged in the trailing lens group GB (Step ST3). Next, a configuration is made in which the focusing group GF moves toward the image side along the optical axis during focusing from an object at infinity to a close-distance object (Step ST4). Then, the lenses are arranged in the lens barrel so as to satisfy at least the above conditional expressions (1-1) and (2) (Step ST5). This manufacturing method makes it possible to manufacture a variable magnification optical system with minimal fluctuation in the angle of view during focusing.

[0065] Next, a manufacturing method for the variable magnification optical system ZL according to the second embodiment will be outlined. The manufacturing method for the variable magnification optical system ZL according to the second embodiment is similar to that described in the first embodiment, and will be described with reference to FIG. 23, as in the first embodiment. First, a leading lens group GA having negative refractive power and a trailing lens group GB having positive refractive power are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is established in which the distance between the leading lens group GA and the trailing lens group GB changes during magnification change (Step ST2). Next, a focusing group GF and an image-side group GC located closer to the image than the focusing group GF are arranged in the trailing lens group GB (Step ST3). Next, a configuration is established in which the focusing group GF moves toward the image side along the optical axis during focusing from an object at infinity to a close-distance object (Step ST4). Then, the lenses are arranged within the lens barrel so as to satisfy at least the above-mentioned conditional expressions (1-2) and (2) (Step ST5). This manufacturing method makes it possible to manufacture a variable magnification optical system with minimal fluctuation in the angle of view during focusing. [Example]

[0066] Variable magnification optical systems ZL according to examples of each embodiment will be described below with reference to the drawings. FIGS. 1, 4, 7, 10, 13, 16, and 19 are cross-sectional views showing the configuration and refractive power distribution of variable magnification optical systems ZL {ZL(1) to ZL(7)} according to Examples 1 to 7. In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(7) according to Examples 1 to 7, 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(7) according to Examples 1 to 7, 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.

[0067] 1, 4, 7, 10, 13, 16, and 19, 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.

[0068] Tables 1 to 7 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, Table 5 in Example 5, Table 6 in Example 6, and Table 7 in Example 7. 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.

[0069] 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: °, where ω is half the angle of view), and Y is the 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 on the optical axis to the image plane I when focused at infinity (back focus). These values ​​are shown for both the wide-angle (W) and telephoto (T) magnification settings. Also, in the [Overall Specifications] table, fBaw is the focal length of the image-side lens group (the lens group consisting of the lenses in the subsequent lens group located closer to the image than the focusing group) in the wide-angle position. fCw is the focal length of the image-side lens group in the wide-angle position. fF is the focal length of the focusing group. βBaw indicates the magnification of the image-side lens group (the lens group consisting of the lenses in the subsequent lens group arranged closer to the image than the focusing group) in the wide-angle end state. βFw indicates the magnification of the focusing group in the wide-angle end state. STLw indicates the distance on the optical axis from the lens surface closest to the object in the variable magnification optical system to the aperture stop in the wide-angle end state.

[0070] In the [Lens Specifications] table, the surface number indicates the order of the optical surface 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 relative to the d-line, and νd is the Abbe number of the optical element material relative to the d-line. The "∞" in the radius of curvature indicates a flat surface or an aperture, (Stop S) indicates the aperture stop S, and (Stop Sa) indicates the secondary stop Sa. The refractive index of air, nd = 1.00000, is omitted. If the optical surface is aspherical, an * is added to the surface number, and the paraxial radius of curvature is shown in the "R" column.

[0071] In the [Aspherical Data] table, the shape of the aspherical surface shown in [Lens Specifications] is shown by the following formula (A). X(y) is the distance (amount of sag) along the optical axis from the tangent plane at the vertex of the aspherical surface to the position on the aspherical surface at height y, R is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and Ai is the ith aspherical coefficient. "En" is the square root of the square root of the aspherical surface. -n For example, 1.234E-05 = 1.234 x 10 -5 The second-order aspherical coefficient A2 is 0, and its description is omitted. When the fourteenth-order aspherical coefficient A14 is 0, its description is omitted.

[0072] X(y)=(y 2 / R) / {1+(1-κ×y 2 / R 2 ) 1 / 2}+A4×y 4 +A6×y 6 +A8×y 8 +A10×y 10 +A12×y 12 +A14×y 14 …(A)

[0073] The [Variable Distance Data] table shows the surface spacing for surface number i, which is indicated as (Di) in the [Lens Specifications] table. The [Variable Distance Data] table also shows the surface spacing when focused at infinity, when focused at intermediate distances, and when focused at close range.

[0074] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0075] 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.

[0076] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0077] (First Example) The first embodiment will be described with reference to FIGS. 1 to 3 and Table 1. FIG. 1 shows the lens configuration of a variable magnification optical system according to the first embodiment. The variable magnification optical system ZL(1) according to the first embodiment is composed of, arranged along the optical axis from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 and the second lens group G2 move toward the image side along the optical axis, and the third lens group G3 and the fourth lens group G4 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed within the fourth lens group G4. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of the lens group, and this is the same in all the following embodiments.

[0078] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, a biconcave negative lens L13, and a positive meniscus lens L14 with a convex surface facing the object side. The negative meniscus lens L11 has aspheric lens surfaces on both sides. The negative meniscus lens L12 has an aspheric lens surface facing the image side. The negative lens L13 is made of optical glass with anomalous dispersion.

[0079] The second lens group G2 is composed of a biconvex positive lens L21. The third lens group G3 is composed of a cemented lens consisting of a negative meniscus lens L31 with its convex surface facing the object side and a positive meniscus lens L32 with its convex surface facing the object side.

[0080] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a negative meniscus lens L41 with a convex surface facing the object side and a positive meniscus lens L42 with a convex surface facing the object side, a cemented lens of a biconcave negative lens L43 and a biconvex positive lens L44, a biconvex positive lens L45, a cemented lens of a negative meniscus lens L46 with a convex surface facing the object side and a positive meniscus lens L47 with a convex surface facing the object side, a cemented lens of a biconvex positive lens L48 and a biconcave negative lens L49, and a negative meniscus lens L50 with a concave surface facing the object side. An image plane I is located on the image side of the fourth lens group G4. An aperture diaphragm S is located between the positive meniscus lens L42 and the negative lens L43 in the fourth lens group G4. A secondary diaphragm Sa is located between the positive lens L44 and the positive lens L45 in the fourth lens group G4. The negative meniscus lens L50 has an aspheric lens surface on the object side. The positive lens L45, the positive meniscus lens L47, and the positive lens L48 are made of optical glass having anomalous dispersion.

[0081] In this embodiment, the first lens group G1 and the second lens group G2 constitute the leading lens group GA, which has a negative refractive power as a whole. The third lens group G3 and the fourth lens group G4 constitute the trailing lens group GB, which has a positive refractive power as a whole. The third lens group G3 constitutes the focusing group GF in the trailing lens group GB, and the fourth lens group G4 constitutes the image-side group GC in the trailing lens group GB. The lenses in the trailing lens group GB arranged on the image side from the focusing group GF, i.e., the lenses in the third lens group G3 and the lenses in the fourth lens group G4, constitute the image-side lens group GBa. When focusing from an object at infinity to a close object, the third lens group G3, which constitutes the focusing group GF, moves toward the image side along the optical axis. The positive lens L45, the positive meniscus lens L47, and the positive lens L48 in the fourth lens group G4 correspond to specific lenses in the trailing lens group GB.

[0082] Table 1 below lists the values ​​of the specifications of the variable magnification optical system according to the first example.

[0083] (Table 1) [Overall specifications] Magnification ratio=1.62 fBaw=34.296 fCw=40.351 fF=123.557 βBaw=-0.633 βFw=2.430 STLw=85.087 WT f 14.4 23.3 FNO 2.91 2.91 2ω 115.2 84.8 Y 21.6 21.6 TL 144.665 134.869 Bf 21.126 34.082 [Lens specifications] Surface number RD nd νd 1* 577.31 3.00 1.588870 61.1 2* 16.50 11.57 3 50.25 2.00 1.820980 42.5 4* 27.05 12.09 5 -43.22 1.50 1.497820 82.6 6 58.13 0.20 7 39.37 5.42 1.673000 38.2 8 1346.43 (D8) 9 8106.07 3.06 1.663820 27.4 10 -101.81 (D10) 11 38.33 2.30 1.963000 24.1 12 20.48 5.15 1.647690 33.7 13 291.48 (D13) 14 23.67 1.20 1.846660 23.7 15 17.23 5.92 1.516800 64.1 16 505.08 1.12 17 ∞ 2.83 (Aperture S) 18 -50.94 1.20 1.953750 32.3 19 23.48 5.62 1.846660 23.7 20 -62.85 0.40 21 ∞ -0.30 (Aperture Sa) 22 24.30 6.05 1.497820 82.6 23 -54.67 0.20 24 50.54 1.20 1.834810 42.7 25 17.41 4.82 1.497820 82.6 26 120.47 0.20 27 32.87 6.32 1.497820 82.6 28 -19.70 1.20 1.834810 42.7 29 82.19 5.21 30* -59.71 3.50 1.860999 37.0 31 -59.99 Bf [Aspherical Data] First Surface κ = 1.000, A4 = 1.20E-05, A6 = -1.77E-08, A8 = 1.69E-11, A10 = -8.86E-15, A12 = 1.98E-18 Second Surface κ = 0.000, A4 = 7.01E-06, A6 = 2.78E-08, A8 = 3.97E-11, A10 = -5.16E-13, A12 = 6.21E-16 Fourth Surface κ = 1.363, A4 = 1.35E-05, A6 = -1.71E-09, A8 = 5.11E-11, A10 = 3.88E-13, A12 = 1.19E-18 Thirtieth Surface κ = 1.000, A4 = -2.05E-05, A6 = -5.87E-08, A8 = 3.00E-10, A10 = -3.42E-12, A12 = 7.38E-15 [Variable Interval Data] Infinity Focus State W M1 M2 T Focal Length 14.40 16.00 18.00 23.30 Object Distance ∞ ∞ ∞ ∞ D8 1.60 1.41 1.29 0.35 D10 17.64 7.99 4.40 1.50 D13 11.32 9.18 8.09 5.95 Bf 21.13 26.37 29.24 34.08 Middle distance focusing state W M1 M2 T Magnification 0.025 0.025 0.025 0.025 Object distance 555 699 781 915 D8 1.60 1.41 1.29 0.35 D10 18.52 8.83 5.11 2.12 D13 10.36 8.28 7.25 5.15 Bf 21.13 26.37 29.24 34.08 Closest distance focusing state W M1 M2 T Magnification 0.094 0.112 0.124 0.144 Object distance 135 142 144 145 D8 1.60 1.41 1.29 0.35 D10 21.51 12.04 8.56 5.80 D13 7.45 5.13 3.93 1.65 Bf 21.13 26.37 29.24 34.08 [Lens group data] Group Starting surface Focal length G1 1 -16.41 G2 9 151.48 G3 11 123.56 G4 14 40.35

[0084] 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.

[0085] 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.

[0086] (Second Example) The second example will be described with reference to FIGS. 4 to 6 and Table 2. FIG. 4 shows the lens configuration of the variable magnification optical system of the second example. The variable magnification optical system ZL(2) of the second example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves toward the image side along the optical axis, and the second lens group G2, the third lens group G3, and the fourth lens group G4 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed within the third lens group G3.

[0087] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, a biconcave negative lens L13, and a biconvex positive lens L14. The negative meniscus lens L11 has aspheric lens surfaces on both sides. The negative meniscus lens L12 has an aspheric lens surface facing the image side. The negative lens L13 is made of optical glass with anomalous dispersion.

[0088] The second lens group G2 is composed of a cemented lens consisting of a negative meniscus lens L21 with a convex surface facing the object side and a positive meniscus lens L22 with a convex surface facing the object side. A secondary aperture stop Sa is located near the object side of the negative meniscus lens L21. When varying magnification or focusing, the secondary aperture stop Sa moves along the optical axis together with the second lens group G2.

[0089] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a negative meniscus lens L31 with a convex surface facing the object side and a positive meniscus lens L32 with a convex surface facing the object side, a cemented lens of a biconcave negative lens L33 and a biconvex positive lens L34, a biconvex positive lens L35, and a cemented lens of a negative meniscus lens L36 with a convex surface facing the object side and a biconvex positive lens L37. An aperture diaphragm S is disposed between the positive meniscus lens L32 and the negative lens L33 in the third lens group G3. A secondary diaphragm Sa is disposed between the positive lens L34 and the positive lens L35 in the third lens group G3. The positive lens L35 and the positive lens L37 are made of optical glass having anomalous dispersion.

[0090] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a cemented lens consisting of a biconvex positive lens L41 and a biconcave negative lens L42, and a positive meniscus lens L43 with its concave surface facing the object side. An image plane I is located on the image side of the fourth lens group G4. The object-side lens surface of the positive meniscus lens L43 is aspherical. The positive lens L41 is made of optical glass with anomalous dispersion.

[0091] In this embodiment, the first lens group G1 constitutes the leading lens group GA, which has negative refractive power as a whole. The second lens group G2, the third lens group G3, and the fourth lens group G4 constitute the trailing lens group GB, which has positive refractive power as a whole. The second lens group G2 constitutes the focusing group GF in the trailing lens group GB, and the third lens group G3 and the fourth lens group G4 constitute the image-side group GC in the trailing lens group GB. The lenses in the trailing lens group GB arranged on the image side of the focusing group GF, i.e., the lenses in the second lens group G2, the lenses in the third lens group G3, and the lenses in the fourth lens group G4, constitute the image-side lens group GBa. When focusing from an object at infinity to a close object, the second lens group G2, which constitutes the focusing group GF, moves toward the image side along the optical axis. The positive lens L35 and the positive lens L37 in the third lens group G3 and the positive lens L41 in the fourth lens group G4 correspond to the specific lenses in the subsequent lens group GB.

[0092] Table 2 below lists the values ​​of the specifications of the variable magnification optical system according to the second example.

[0093] (Table 2) [Overall specifications] Magnification ratio=1.62 fBaw=32.710 fCw=43.782 fF=88.43 βBaw=-0.671 βFw=5.116 STLw=78.53 WT f 14.4 23.3 FNO 2.91 2.91 2ω 115.2 84.8 Y 21.6 21.6 TL 137.42 129.49 Bf 21.81 34.22 [Lens specifications] Surface number RD nd νd 1* 211.83 3.00 1.588870 61.1 2* 16.00 11.62 3 48.68 2.00 1.820980 42.5 4* 25.71 11.53 5 -43.59 1.50 1.497820 82.6 6 54.13 0.57 7 40.33 6.61 1.625844 34.2 8 -86.60 (D8) 9 ∞ 0.00 (Aperture Sa) 10 36.98 1.10 1.963000 24.1 11 19.61 4.30 1.680196 30.7 12 1248.24 (D12) 13 26.09 1.10 1.846660 23.8 14 17.50 6.20 1.489456 69.9 15 1516.29 1.54 16 ∞ 2.69 (Aperture S) 17 -46.01 1.10 1.953750 32.3 18 26.50 5.40 1.846660 23.8 19 -55.71 0.37 20 ∞ -0.30 (Aperture Sa) 21 25.77 6.00 1.497820 82.6 22 -51.72 0.20 23 53.18 1.10 1.834810 42.7 24 17.71 5.00 1.497820 82.6 25 -115.03 (D25) 26 57.48 7.00 1.497820 82.6 27 -18.97 1.10 1.834810 42.7 28 69.64 3.91 29* -41.36 2.00 1.860999 37.1 30 -35.53 Bf [Aspherical data] Front page κ=1.000,A4=1.09E-05,A6=-1.70E-08,A8=1.67E-11,A10=-8.87E-15,A12=1.93E-18 2nd side κ=0.000,A4=9.21E-06,A6=2.31E-08,A8=1.30E-11,A10=-4.06E-13,A12=4.84E-16 Side 4 κ=1.318,A4=1.28E-05,A6=-2.13E-09,A8=9.99E-11,A10=8.40E-14,A12=6.41E-16 Page 29 κ=1.000,A4=-1.74E-05,A6=-5.18E-08,A8=1.22E-10,A10=-2.24E-12,A12=2.49E-15 [Variable Interval Data] Infinity focus W M1 M2 T Focal lengths: 14.40, 16.00, 18.00, 23.30 Object distances: ∞, ∞, ∞, ∞ D8: 19.84, 14.93, 10.08, 1.68 D12: 7.63, 7.20, 6.53, 5.03 D25: 1.50, 1.62, 1.79, 1.92 Bf: 21.81, 24.03, 26.72, 34.22 Focus state at intermediate distance W, M1, M2, T Magnification: 0.025, 0.025, 0.025, 0.025 Object distances: 547, 611, 692, 904 D8: 20.67, 15.70, 10.78, 2.26 D12: 6.80, 6.43, 5.83, 4.44 D25: 1.50, 1.62, 1.79, 1.92 Bf: 21.81, 24.03, 26.72, 34.22 Focus state at closest distance W, M1, M2, T Magnification: 0.091, 0.099, 0.110, 0.142 Object distances: 136, 139, 141, 144 D8: 22.71, 17.82, 13.​​​​​​​​​​​​​​​​​​​​​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.

[0095] (Third Example) The third example will be described with reference to FIGS. 7 to 9 and Table 3. FIG. 7 shows the lens configuration of the variable magnification optical system of the third example. The variable magnification optical system ZL(3) of the third example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power. When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves toward the image side along the optical axis, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed between the third lens group G3 and the fourth lens group G4.

[0096] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, and a cemented lens consisting of a biconcave negative lens L13 and a positive meniscus lens L14 with a convex surface facing the object side. Both lens surfaces of the negative meniscus lens L11 are aspheric. The lens surface of the negative meniscus lens L12 facing the image side is aspheric.

[0097] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a biconvex positive lens L21 and a biconcave negative lens L22, and a biconvex positive lens L23.

[0098] The third lens group G3 is composed of a cemented lens consisting of a negative meniscus lens L31 with a convex surface facing the object side and a positive meniscus lens L32 with a convex surface facing the object side. A secondary aperture stop Sa is located near the object side of the negative meniscus lens L31. When varying magnification, the secondary aperture stop Sa moves along the optical axis together with the third lens group G3.

[0099] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L41 and a biconvex positive lens L42, a biconvex positive lens L43, and a cemented lens of a negative meniscus lens L44 with its convex surface facing the object side and a biconvex positive lens L45. An aperture diaphragm S is located near the object side of the negative lens L41. During magnification variation, the aperture diaphragm S moves along the optical axis together with the fourth lens group G4. The positive lens L42 and the positive lens L45 are made of optical glass with anomalous dispersion.

[0100] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens consisting of a biconcave negative lens L51 and a biconvex positive lens L52, and a positive meniscus lens L53 with its concave surface facing the object side. An image surface I is located on the image side of the fifth lens group G5. The image-side lens surface of the positive meniscus lens L53 is aspherical.

[0101] In this embodiment, the first lens group G1 constitutes the leading lens group GA, which has a negative refractive power as a whole. The second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the trailing lens group GB, which has a positive refractive power as a whole. The positive lens L23 of the second lens group G2 constitutes the focusing group GF of the trailing lens group GB, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the image-side group GC of the trailing lens group GB. The lenses in the trailing lens group GB that are located closer to the image side than the focusing group GF, i.e., the positive lens L23 of the second lens group G2, the lenses of the third lens group G3, the lenses of the fourth lens group G4, and the lenses of the fifth lens group G5, constitute the image-side lens group GBa. When focusing from an object at infinity to an object at a close distance, the positive lens L23 of the second lens group G2 constituting the focusing group GF moves toward the image along the optical axis, and the positive lenses L42 and L45 of the fourth lens group G4 correspond to the specific lenses in the subsequent lens group GB.

[0102] Table 3 below lists the values ​​of the specifications of the variable magnification optical system according to the third example.

[0103] (Table 3) [Overall specifications] Magnification ratio=1.62 fBaw=29.379 fCw=47.692 fF=53.757 βBaw=-1.010 βFw=13.381 STLw=87.283 WT f 14.4 23.3 FNO 2.91 2.91 2ω 115.2 84.8 Y 21.6 21.6 TL 144.802 133.372 Bf 20.14 33.38 [Lens specifications] Surface number RD nd νd 1* 64.00 3.50 1.588870 61.1 2* 14.38 13.77 3 65.31 1.20 1.860999 37.1 4* 29.79 10.56 5 -59.81 1.80 1.433848 95.2 6 31.48 6.27 1.806100 33.3 7 346.05 (D7) 8 54.45 4.40 1.698950 30.1 9 -50.78 1.20 1.963000 24.1 10 68.50 (D10) 11 74.83 3.56 1.728250 28.4 12 -80.45 (D12) 13 ∞ 0.00 (Aperture Sa) 14 24.95 1.20 1.834000 37.2 15 16.99 5.80 1.487490 70.3 16 638.04 (D16) 17 ∞ 5.96 (Aperture S) 18 -36.03 1.20 1.834810 42.7 19 45.21 4.32 1.497820 82.6 20 -34.72 0.20 21 40.69 3.42 1.749500 35.3 22 -134.06 0.20 23 30.00 1.20 1.834000 37.2 24 19.99 6.27 1.497820 82.6 25 -51.98 (D25) 26 -48.67 1.20 1.953747 32.3 27 20.07 5.51 1.672700 32.2 28 -149.29 2.93 29 -55.36 1.30 1.860999 37.1 30* -46.85 Bf [Aspherical surface] Page 1 κ=1.000,A4=-8.79E-06,A6=2.17E-08,A8=-2.83E-11,A10=2.14E-14,A12=-8.62E-18 A14=1.45E-21 Page 2 κ=0.000,A4=-2.40E-06,A6=9.20E-09,A8=6.55E-11,A10=8.23E-13,A12=-2.48E-15 A14=2.37E-18 Page 4 κ=2.000,A4=5.35E-06,A6=1.13E-08,A8=-1.30E-11,A10=-1.43E-13,A12=1.36E-15 A14=-2.65E-18 Page 30 κ=1.000,A4=1.70E-05,A6=-1.10E-09,A8=2.84E-10,A10=-1.42E-12,A12=3.03E-15 [Can change the interval データ] Infinity focus state W M1 M2 T Focus distance 14.40 18.00 20.00 23.30 Object distance ∞ ∞ ∞ ∞ D7 22.75 11.02 6.71 1.50 D10 1.10 1.10 1.10 1.10 D12 3.61 4.07 3.94 3.64 D16 6.57 4.21 3.24 1.91 D25 3.66 4.37 4.60 4.87 Bf 20.14 25.54 28.52 33.38 Middle distance focus state W M1 M2 T Magnification 0.025 0.025 0.025 0.025 Object distance 556 696 776 909 D7 22.75 11.02 6.71 1.50 D10 1.45 1.43 1.40 1.37 D12 3.22 3.74 3.64 3.37 D16 6.57 4.21 3.24 1.91 D25 3.66 4.37 4.60 4.87 Bf 20.14 25.54 28.52 33.38 To the close-focus state W M1 M2 T Magnification 0.090 0.108 0.119 0.138 Object distance 135 142 144 146 D7 22.75 11.02 6.71 1.50 D10 2.42 2.52 2.54 2.59 D12 2.28 2.65 2.50 2.15<000​​​​​​​​​​​​​​​​​​​​​​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.

[0105] (Fourth Example) Example 4 will be described with reference to FIGS. 10 to 12 and Table 4. FIG. 10 shows the lens configuration of a variable magnification optical system according to Example 4. Example 4's variable magnification optical system ZL(4) is composed of, arranged along the optical axis from the object side, a first lens group G1 with negative refractive power, a second lens group G2 with positive refractive power, and a third lens group G3 with positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves toward the image side along the optical axis, and the second lens group G2 and the third lens group G3 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed within the third lens group G3.

[0106] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, a biconcave negative lens L13, and a biconvex positive lens L14. The negative meniscus lens L11 has aspheric lens surfaces on both sides. The negative meniscus lens L12 has an aspheric lens surface facing the image side. The negative lens L13 is made of optical glass with anomalous dispersion.

[0107] The second lens group G2 is composed of a cemented lens made up of a negative meniscus lens L21 with a convex surface facing the object side and a positive meniscus lens L22 with a convex surface facing the object side.

[0108] The third lens group G3 is composed of, arranged along the optical axis from the object side, a cemented lens of a negative meniscus lens L31 with a convex surface facing the object side and a positive meniscus lens L32 with a convex surface facing the object side, a cemented lens of a biconcave negative lens L33 and a biconvex positive lens L34, a biconvex positive lens L35, a cemented lens of a negative meniscus lens L36 with a convex surface facing the object side and a positive meniscus lens L37 with a convex surface facing the object side, a cemented lens of a biconvex positive lens L38 and a biconcave negative lens L39, and a positive meniscus lens L40 with a concave surface facing the object side. An image plane I is located on the image side of the third lens group G3. An aperture stop S is located between the positive meniscus lens L32 and the negative lens L33 in the third lens group G3. The object-side lens surface of the positive meniscus lens L40 is aspheric. The positive lens L35, the positive meniscus lens L37, and the positive lens L38 are made of optical glass having anomalous dispersion.

[0109] In this embodiment, the first lens group G1 constitutes the leading lens group GA, which has a negative refractive power as a whole. The second lens group G2 and the third lens group G3 constitute the trailing lens group GB, which has a positive refractive power as a whole. The second lens group G2 constitutes the focusing group GF in the trailing lens group GB, and the third lens group G3 constitutes the image-side group GC in the trailing lens group GB. The lenses in the trailing lens group GB arranged on the image side of the focusing group GF, i.e., the lenses in the second lens group G2 and the lenses in the third lens group G3, constitute the image-side lens group GBa. When focusing from an object at infinity to a close object, the second lens group G2, which constitutes the focusing group GF, moves toward the image side along the optical axis. The positive lens L35, the positive meniscus lens L37, and the positive lens L38 in the third lens group G3 correspond to specific lenses in the trailing lens group GB.

[0110] Table 4 below lists the values ​​of the specifications of the variable magnification optical system according to the fourth example.

[0111] (Table 4) [Overall specifications] Magnification ratio=1.62 fBaw=32.727 fCw=39.261 fF=105.275 βBaw=-0.674 βFw=2.687 STLw=80.664 WT f 14.4 23.3 FNO 2.91 2.91 2ω 115.2 84.8 Y 21.6 21.6 TL 138.261 132.362 Bf 22.54 35.22 [Lens specifications] Surface number RD nd νd 1* 151.50 3.00 1.588870 61.1 2* 16.04 13.37 3 88.74 2.00 1.743104 49.4 4* 27.44 10.00 5 -74.77 1.50 1.497820 82.6 6 57.87 0.15 7 37.08 5.77 1.737999 32.3 8 -644.56 (D8) 9 32.64 1.10 2.000600 25.4 10 19.01 5.30 1.647690 33.7 11 210.30 (D11) 12 28.61 1.10 1.850000 27.0 13 18.19 6.08 1.593490 67.0 14 522.90 1.95 15 ∞ 2.88 (Aperture S) 16 -66.86 1.10 1.953750 32.3 17 25.72 5.35 1.846660 23.7 18 -78.70 0.40 19 24.36 6.27 1.497820 82.6 20 -54.74 0.15 21 43.10 1.10 1.834810 42.7 22 16.90 4.40 1.497820 82.6 23 73.95 0.20 24 31.23 5.73 1.497820 82.6 25 -23.20 1.10 1.834810 42.7 26 55.41 3.93 27* -68.43 2.00 1.851080 40.1 28 -54.15 Bf [Aspherical surface] Page 1 κ=1.000,A4=4.50E-06,A6=-3.56E-09,A8=2.17E-12,A10=-5.59E-16,A12=0.00E+00 Page 2 κ=0.000,A4=3.63E-06,A6=7.91E-09,A8=2.28E-11,A10=-1.36E-13,A12=1.21E-16 Page 4 κ=0.000,A4=2.15E-05,A6=2.23E-08,A8=2.16E-11,A10=1.77E-13,A12=-1.00E-16 Page 27 κ=1.000,A4=-2.41E-05,A6=-4.89E-08,A8=-1.02E-10,A10=-7.59E-13,A12=-3.14E-15 [Can change the interval データ] Infinity focus state W M1 M2 T Focus distance 14.42 18.00 20.00 23.29 Object distance ∞ ∞ ∞ ∞ D8 19.11 10.32 6.94 2.78 D11 10.68 8.35 7.26 5.72 Bf 22.54 27.74 30.59 35.22 Middle distance focusing state W M1 M2 T Magnification 0.025 0.025 0.025 0.025 Object distance 553 697 777 909 D8 20.03 11.12 7.69 3.46 D11 9.77 7.55 6.52 5.04 Bf 22.54 27.74 30.59 35.22 Closest distance focusing state W M1 M2 T Magnification 0.088 0.106 0.117 0.135 Object distance 141 147 149 150 D8 22.29 13.66 10.37 6.38 D11 7.50 5.02 3.83 2.13 Bf 22.​​​​​​​​​​​​​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.

[0113] (Fifth Example) The fifth example will be described with reference to FIGS. 13 to 15 and Table 5. FIG. 13 shows the lens configuration of the variable magnification optical system of the fifth example. The variable magnification optical system ZL(5) of the fifth example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves toward the image side along the optical axis, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed between the third lens group G3 and the fourth lens group G4.

[0114] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, a biconcave negative lens L13, and a biconvex positive lens L14. The negative meniscus lens L11 has aspheric lens surfaces on both sides, and the negative meniscus lens L12 has an aspheric lens surface on the image side.

[0115] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L21 and a cemented lens of a biconvex positive lens L22 and a biconcave negative lens L23.

[0116] The third lens group G3 is composed of a cemented lens consisting of a negative meniscus lens L31 with a convex surface facing the object side and a positive meniscus lens L32 with a convex surface facing the object side. A secondary aperture stop Sa is located near the object side of the negative meniscus lens L31. When varying magnification, the secondary aperture stop Sa moves along the optical axis together with the third lens group G3.

[0117] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a biconcave negative lens L41 and a biconvex positive lens L42, a biconvex positive lens L43, and a cemented lens of a negative meniscus lens L44 with its convex surface facing the object side and a biconvex positive lens L45. An aperture diaphragm S is located near the object side of the negative lens L41. During magnification variation, the aperture diaphragm S moves along the optical axis together with the fourth lens group G4. The positive lens L42 and the positive lens L45 are made of optical glass with anomalous dispersion.

[0118] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens consisting of a biconcave negative lens L51 and a biconvex positive lens L52, and a positive meniscus lens L53 with its concave surface facing the object side. An image surface I is located on the image side of the fifth lens group G5. The image-side lens surface of the positive meniscus lens L53 is aspherical.

[0119] In this embodiment, the first lens group G1 constitutes the leading lens group GA, which has a negative refractive power as a whole. The second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the trailing lens group GB, which has a positive refractive power as a whole. The second lens group G2 constitutes the focusing group GF in the trailing lens group GB, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the image-side group GC in the trailing lens group GB. The lenses in the trailing lens group GB arranged on the image side from the focusing group GF, i.e., the lenses in the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5, constitute the image-side lens group GBa. When focusing from an object at infinity to a close object, the second lens group G2, which constitutes the focusing group GF, moves toward the image along the optical axis. The positive lens L42 and the positive lens L45 in the fourth lens group G4 correspond to the specific lenses in the subsequent lens group GB.

[0120] Table 5 below lists the values ​​of the specifications of the variable magnification optical system according to the fifth example.

[0121] (Table 5) [Overall specifications] Magnification ratio=1.62 fBaw=34.9 fCw=39.261 fF=83.88 βBaw=-0.702 βFw=4.267 STLw=87.277 WT f 14.4 23.3 FNO 2.91 2.91 2ω 115.0 84.2 Y 21.6 21.6 TL 143.628 133.3 Bf 20.07 33.17 [Lens specifications] Surface number RD nd νd 1* 71.95 3.20 1.588870 61.1 2* 14.51 13.55 3 61.90 2.00 1.860999 37.0 4* 29.57 10.97 5 -50.12 1.80 1.433848 95.2 6 39.08 0.92 7 39.32 5.73 1.806100 33.3 8 -2630.42 (D8) 9 102.26 3.51 1.728250 28.3 10 -67.66 0.20 11 45.26 4.78 1.698950 30.1 12 -44.14 1.20 1.963000 24.1 13 53.69 (D13) 14 ∞ 0.00 (Aperture Sa) 15 23.84 1.20 1.834000 37.1 16 16.67 5.13 1.487490 70.3 17 169.89 (D17) 18 ∞ 3.68 (Aperture S) 19 -75.47 1.20 1.850260 32.3 20 32.29 4.36 1.497820 82.6 21 -56.96 0.20 22 36.85 3.92 1.749500 35.2 23 -94.60 0.20 24 29.88 1.20 1.834000 37.1 25 18.28 5.81 1.497820 82.6 26 -92.45 (D26) 27 -67.55 1.20 1.953747 32.3 28 18.47 5.74 1.672700 32.1 29 -131.73 4.54 30 -42.81 1.30 1.860999 37.0 31* -40.24 Bf [Aspherical surface] Page 1 κ=1.000,A4=-8.11E-06,A6=2.22E-08,A8=-3.09E-11,A10=2.50E-14,A12=-1.09E-17 A14=2.04E-21 Page 2 κ=0.000,A4=-1.69E-06,A6=3.53E-11,A8=2.41E-11,A10=4.17E-13,A12=-1.56E-15 A14=1.45E-18 Page 4 κ=2.000,A4=4.30E-06,A6=1.19E-08,A8=-1.88E-11,A10=-1.27E-13,A12=1.26E-15 A14=-2.10E-18 Page 31 κ=1.000,A4=1.40E-05,A6=3.24E-09,A8=1.91E-10,A10=-1.08E-12,A12=2.54E-15 [Can change the interval データ] Infinity focus state W M1 M2 T Focus distance 14.40 18.00 20.00 23.30 Object distance ∞ ∞ ∞ ∞ D8 22.07 10.81 6.77 1.50 D13 5.69 5.68 5.31 5.57 D17 5.31 3.58 2.91 1.50 D21 0.93 0.50 0.35 0.20 D26 2.93 3.61 3.79 4.01 Bf 20.07 25.18 28.12 33.17 Middle distance focus state W M1 M2 T Magnification 0.025 0.025 0.025 0.025 Object distance 554 696 777 910 D8 22.81 11.47 7.39 2.06 D13 4.94 5.02 4.69 5.01 D17 5.31 3.58 2.91 1.50 D21 0.93 0.50 0.35 0.20 D26 2.93 3.61 3.79 4.01 Bf 20.07 25.18 28.12 33.17 To the close focusing state W M1 M2 T Magnification 0.090 0.108 0.119 0.138 Object distance 136 143 145 146 D8 24.58 13.62 9.64 4.56 D13 3.17 2.86 2.44 2.52 D17 5.31 3.58 2.91 1.50 D21 0.93 0.50 0.35 0.20 D26 2.93 3.61 3.79 4.01 Bf 20.07 25.18 28.12 33.17 [Lens group data] Group Starting surface Focal length G1 1 -20.50 G2 9 83.88 G3 14 83.19 G4 18 30.00 G5 27 -46.50

[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] (Sixth Example) Example 6 will be described with reference to FIGS. 16 to 18 and Table 6. FIG. 16 shows the lens configuration of a variable magnification optical system according to Example 6. The variable magnification optical system ZL(6) according to Example 6 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 and the second lens group G2 move toward the image side along the optical axis, and the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed between the second lens group G2 and the third lens group G3.

[0124] The first lens group G1 is composed of, arranged along the optical axis from the object side, a negative meniscus lens L11 with a convex surface facing the object side, a positive meniscus lens L12 with a concave surface facing the object side, and a cemented lens consisting of a biconcave negative lens L13 and a positive meniscus lens L14 with a convex surface facing the object side. Both lens surfaces of the negative meniscus lens L11 are aspherical. The negative lens L13 is made of optical glass with anomalous dispersion.

[0125] The second lens group G2 is composed of a cemented lens consisting of a biconvex positive lens L21 and a negative meniscus lens L22 with its concave surface facing the object side. The third lens group G3 is composed of a biconvex positive lens L31. An aperture diaphragm S is located near the object side of the positive lens L31. When varying magnification, the aperture diaphragm S moves along the optical axis together with the third lens group G3. The positive lens L31 is made of optical glass with anomalous dispersion.

[0126] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a biconcave negative lens L41 and a positive meniscus lens L42 with its convex surface facing the object side. A secondary aperture stop Sa is located near the image side of the positive meniscus lens L42. When varying magnification, the secondary aperture stop Sa moves along the optical axis together with the fourth lens group G4.

[0127] The fifth lens group G5 is composed of, arranged along the optical axis from the object side, a cemented lens of a biconvex positive lens L51 and a negative meniscus lens L52 with a concave surface facing the object side, a cemented lens of a negative meniscus lens L53 with a convex surface facing the object side and a positive meniscus lens L54 with a convex surface facing the object side, a biconvex positive lens L55, a biconcave negative lens L56, and a positive meniscus lens L57 with a concave surface facing the object side. The negative lens L56 has an aspheric lens surface facing the object side. The positive lens L51, the positive meniscus lens L54, and the positive meniscus lens L57 are made of optical glass with anomalous dispersion.

[0128] The sixth lens group G6 is composed of, arranged in order from the object side along the optical axis, a biconcave negative lens L61 and a positive meniscus lens L62 with its concave surface facing the object side. An image plane I is located on the image side of the sixth lens group G6. The negative lens L61 has an aspherical lens surface facing the object side. The positive meniscus lens L62 has an aspherical lens surface facing the object side.

[0129] In this embodiment, the first lens group G1 constitutes the leading lens group GA, which has a negative refractive power as a whole. The second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 constitute the trailing lens group GB, which has a positive refractive power as a whole. The second lens group G2 constitutes the focusing group GF in the trailing lens group GB, and the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 constitute the image-side group GC in the trailing lens group GB. The lenses in the trailing lens group GB that are located closer to the image side than the focusing group GF, i.e., the lenses in the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6, constitute the image-side lens group GBa. When focusing from an object at infinity to a close object, the second lens group G2 constituting the focusing group GF moves toward the image along the optical axis. When focusing from an object at infinity to a close object, the negative lens L56 and positive meniscus lens L57 of the fifth lens group G5 constituting the second focusing group GF2 move toward the object along the optical axis. The positive lens L31 of the third lens group G3 and the positive lens L51, positive meniscus lens L54, and positive meniscus lens L57 of the fifth lens group G5 correspond to specific lenses in the subsequent lens group GB.

[0130] Table 6 below lists the values ​​of the specifications of the variable magnification optical system according to the sixth example.

[0131] (Table 6) [Overall specifications] Magnification ratio=2.06 fBaw=38.120 fCw=38.813 fF=113.314 βBaw=-0.770 βFw=1.834 STLw=72.551 WT f 16.5 34.0 FNO 2.91 2.91 2ω 108.2 63.0 Y 21.6 21.6 TL 157.65 139.68 Bf 12.48 32.74 [Lens specifications] Surface number RD nd νd 1* 101.86 2.80 1.790630 44.9 2* 17.50 15.42 3 -86.28 2.33 1.755200 27.5 4 -56.75 0.49 5 -51.79 1.70 1.497820 82.6 6 35.60 4.74 1.854505 25.1 7 79.30 (D7) 8 281.88 3.62 1.834801 42.7 9 -59.25 1.10 1.922860 20.8 10 -124.87 (D10) 11 ∞ 1.50 (Aperture S) 12 30.00 6.70 1.497820 82.6 13 -57.17 (D13) 14 -56.59 1.10 1.870705 40.7 15 66.46 0.20 16 43.96 2.53 1.922860 20.8 17 124.88 1.50 18∞ (D18) (Aperture Sa) 19 42.12 8.18 1.497820 82.6 20 -25.33 1.20 2.001000 29.1 21 -469.54 0.20 22 33.67 1.20 1.953747 32.3 23 21.47 6.99 1.497820 82.6 24 93.49 0.20 25 35.65 7.53 1.850260 32.3 26 -62.05 (D26) 27* -500.00 1.40 1.870705 40.7 28 459.53 1.20 29 -141.51 4.75 1.497820 82.6 30 -30.90 (D30) 31* -79.23 1.40 1.851080 40.1 32 34.18 7.09 33* -500.00 2.22 1.922860 20.8 34 -201.44 Bf [Aspherical surface] Page 1 κ=1.000,A4=-4.56E-07,A6=1.02E-09,A8=-1.24E-12,A10=7.97E-16,A12=-2.87E-19 Page 2 κ=0.000,A4=9.94E-06,A6=1.24E-08,A8=-8.79E-12,A10=5.99E-14,A12=-4.00E-17 Page 27 κ=1.000,A4=-2.12E-05,A6=-1.66E-09,A8=7.73E-11,A10=-1.53E-13,A12=1.07E-16 Page 31 κ=1.000,A4=-1.01E-05,A6=-1.21E-08,A8=-1.82E-10,A10=1.01E-12,A12=-1.31E-15 Page 33 κ=1.000,A4=-9.51E-07,A6=-4.11E-09,A8=7.09E-12,A10=-5.94E-14,A12=-2.83E-16 [Can change the interval データ] Infinity focus state W M1 M2 T Focus distance 16.50 20.00 24.00 34.00 Object distance ∞ ∞ ∞ ∞ D7 12.04 5.91 2.94 2.30 D10 28.31 22.58 17.45 5.39 D13 2.32 2.86 3.79 5.78 D18 8.63 6.49 4.10 0.00 D26 2.47 2.47 2.47 2.47 D30 2.10 2.43 2.31 1.70 Bf 12.48 16.82 21.70 32.74 Middle distance focusing state W M1 M2 T Magnification 0.033 0.033 0.033 0.033 Object distance 472 698 578 998 D7 13.28 7.00 3.88 2.94 D10 27.07 21.49 16.51 4.76 D13 2.32 2.86 3.79 5.78 D18 8.63 6.49 4.10 0.00 D26 2.44 2.41 2.40 2.37 D30 2.14 2.49 2.38 1.81 Bf 12.48 16.82 21.70 32.74 Closest distance focusing state W M1 M2 T Magnification 0.115 0.132 0.153 0.176 Object distance 121 130 138 139 D7 16.20 10.09 7.11 6.19 D10 24.14 18.40 13.28 1.50 D13 2.32 2.86 3.79 5.78 D18 8.63 6.49 4.10 0.00 D26 2.33 2.22 2.13 1.80 D30 2.24 2.68 2.66 2.37 Bf 12.48 16.82 21.70 32.74 [Lens group data] Group Starting surface Focal length G1 1 -21.432 G2 8 113.314 G3 11 40.562 G4 14 -67.240 G5 19 28.11 G6 31 -31.068

[0132] FIG. 17(A) is a diagram showing various aberrations of the variable magnification optical system of Example 6 when focusing at infinity in the wide-angle end state. FIG. 17(B) is a diagram showing various aberrations of the variable magnification optical system of Example 6 when focusing at infinity in the telephoto end state. FIG. 18(A) is a diagram showing various aberrations of the variable magnification optical system of Example 6 when focusing at a close distance in the wide-angle end state. FIG. 18(B) is a diagram showing various aberrations of the variable magnification optical system of Example 6 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 6 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.

[0133] (Seventh Example) Example 7 will be described with reference to FIGS. 19 to 21 and Table 7. FIG. 19 shows the lens configuration of a variable magnification optical system according to Example 7. Example 7's variable magnification optical system ZL(7) is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves toward the image side along the optical axis, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed between the second lens group G2 and the third lens group G3.

[0134] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, a biconcave negative lens L13, and a biconvex positive lens L14. The negative meniscus lens L11 has aspheric lens surfaces on both sides. The negative meniscus lens L12 has an aspheric lens surface facing the image side. The negative lens L13 is made of optical glass with anomalous dispersion.

[0135] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a negative meniscus lens L21 with a convex surface facing the object side and a biconvex positive lens L22, a positive meniscus lens L23 with a convex surface facing the object side, and a cemented lens of a negative meniscus lens L24 with a convex surface facing the object side and a biconvex positive lens L25. A secondary aperture stop Sa is disposed between the positive lens L22 and the positive meniscus lens L23 in the second lens group G2.

[0136] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L31 with its concave surface facing the object side, a biconcave negative lens L32, and a biconvex positive lens L33. An aperture diaphragm S is located near the object side of the negative meniscus lens L31. A secondary diaphragm Sa is located near the image side of the positive lens L33. When varying magnification, the aperture diaphragm S and the secondary diaphragm Sa move along the optical axis together with the third lens group G3.

[0137] The fourth lens group G4 is composed of, arranged along the optical axis from the object side, a cemented lens of a negative meniscus lens L41 with a convex surface facing the object side and a biconvex positive lens L42, a cemented lens of a biconvex positive lens L43 and a negative meniscus lens L44 with a concave surface facing the object side, a biconvex positive lens L45, and a biconcave negative lens L46. The image-side lens surface of the negative lens L46 is aspherical. The positive lens L42 and the positive lens L43 are made of optical glass with anomalous dispersion.

[0138] The fifth lens group G5 is composed of a negative meniscus lens L51 with its concave surface facing the object side. An image surface I is located on the image side of the fifth lens group G5. The negative meniscus lens L51 has an aspherical lens surface on the image side.

[0139] In this embodiment, the first lens group G1 constitutes the leading lens group GA, which has a negative refractive power as a whole. The second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the trailing lens group GB, which has a positive refractive power as a whole. The negative meniscus lens L21 and the positive lens L22 of the second lens group G2 constitute the focusing group GF of the trailing lens group GB, and the positive meniscus lens L23, the negative meniscus lens L24, and the positive lens L25 of the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the image-side group GC of the trailing lens group GB. The lenses in the trailing lens group GB arranged on the image side of the focusing group GF, i.e., the lenses of the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5, constitute the image-side lens group GBa. When focusing from an object at infinity to a close object, the negative meniscus lens L21 and positive lens L22 of the second lens group G2 that constitutes the focusing group GF move toward the image along the optical axis. When focusing from an object at infinity to a close object, the positive lens L45 and negative lens L46 of the fourth lens group G4 that constitutes the second focusing group GF2 move toward the object along the optical axis. The positive lens L42 and positive lens L43 of the fourth lens group G4 correspond to specific lenses in the subsequent lens group GB.

[0140] Table 7 below lists the values ​​of the specifications of the variable magnification optical system according to the seventh example.

[0141] (Table 7) [Overall specifications] Magnification ratio=2.06 fBaw=37.589 fCw=50.452 fF=113.314 βBaw=-0.707 βFw=4.383 STLw=89.22 WT f 16.5 34.0 FNO 2.91 2.91 2ω 108.2 63.0 Y 21.6 21.6 TL 157.56 147.45 Bf 19.36 32.89 [Lens specifications] Surface number RD nd νd 1* 104.57 2.80 1.820980 42.5 2* 17.08 9.90 3 60.02 2.00 1.820980 42.5 4* 39.88 8.96 5 -47.04 1.70 1.456000 91.3 6 99.56 0.20 7 69.77 4.42 2.000600 25.4 8 -360.61 (D8) 9 51.00 1.10 1.963000 24.1 10 26.00 5.60 1.672700 32.1 11 -344.00 (D11) 12 ∞ 0.00 (Aperture Sa) 13 51.32 3.60 1.816659 29.2 14 546.18 0.20 15 55.66 1.20 1.846660 23.7 16 25.97 8.10 1.487490 70.3 17 -49.86 (D17) 18 ∞ 3.69 (Aperture S) 19 -47.28 1.10 1.953750 32.3 20 -294.71 1.39 21 -67.34 1.10 1.953750 32.3 22 97.38 0.20 23 40.32 3.30 1.922860 20.8 24 -773.06 1.50 25 ∞ (D25) 26 73.81 1.10 1.953750 32.3 27 20.74 6.00 1.497820 82.6 28 -161.32 0.20 29 26.70 9.30 1.497820 82.6 30 -23.87 1.20 1.953750 32.3 31 -34.06 (D31) 32 636.03 3.55 1.808090 22.7 33 -42.69 0.20 34 -54.47 1.40 1.851080 40.1 35* 98.18 (D35) 36 -22.05 1.40 1.820980 42.5 37* -32.00 Bf [Aspherical surface] Page 1 κ=1.000,A4=-1.01E-06,A6=5.63E-09,A8=-7.40E-12,A10=3.87E-15,A12=-5.67E-19 Page 2 κ=0.000,A4=3.61E-06,A6=9.15E-09,A8=1.27E-11,A10=1.52E-13,A12=-3.00E-16 Page 4 κ=1.000,A4=4.88E-06,A6=4.08E-09,A8=-1.88E-11,A10=-1.60E-14,A12=1.46E-16 Page 35 κ=1.000,A4=1.17E-05,A6=1.03E-08,A8=-1.15E-10,A10=1.05E-12,A12=-3.70E-15 Page 37 κ=1.000,A4=6.03E-06,A6=7.34E-09,A8=2.29E-10,A10=-9.55E-13,A12=3.17E-15 [Can change the interval データ] Infinity focus state W M1 M2 T Focus distance 16.50 20.00 24.00 34.00 Object distance ∞ ∞ ∞ ∞ D8 31.43 20.54 12.49 1.50 D11 7.01 7.01 7.01 7.01 D17 1.00 1.56 2.36 4.70 D25 6.55 4.76 3.13 0.00 D31 2.85 4.09 4.91 5.70 D35 7.41 7.41 7.41 7.41 Bf 19.36 24.65 27.69 32.89 Focus state at middle distance W M1 M2 T Magnification 0.033 0.034 0.029 0.034 Object distance 465 566 801 980 D8 32.61 21.57 13.40 2.30 D11 5.83 5.99 6.11 6.26 D17 1.00 1.56 2.36 4.70 D25 6.55 4.76 3.13 0.00 D31 2.61 3.89 4.65 5.47 D35 7.64 7.59 7.67 7.63 Bf 19.36 24.65 27.69 32.89 Close focus W M1 M2 T Magnification 0.113 0.132 0.156 0.222 Object distance 116 122 125 125 D8 35.53 24.70 16.98 6.55 D11 2.90 2.85 2.52 2.00 D17 1.00 1.56 2.36 4.70 D25 6.55 4.76 3.13 0.00 D31 2.00 3.33 3.86 4.38 D35 8.28 8.16 8.47 8.72 Bf 19.36 24.65 27.69 32.89 [Lens group data] Group starting plane focal length G1 1 -23.35 G2 9 32.35 G3 18 -61.43 G4 26 52.78 G5 36 -92.26

[0142] FIG. 20(A) is a diagram showing various aberrations of the variable magnification optical system of Example 7 when focusing at infinity in the wide-angle end state. FIG. 20(B) is a diagram showing various aberrations of the variable magnification optical system of Example 7 when focusing at infinity in the telephoto end state. FIG. 21(A) is a diagram showing various aberrations of the variable magnification optical system of Example 7 when focusing at a close distance in the wide-angle end state. FIG. 21(B) is a diagram showing various aberrations of the variable magnification optical system of Example 7 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 7 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.

[0143] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below. This table summarizes the values ​​corresponding to conditional expressions (1-1), (1-2), and (2) to (14) for all examples (Examples 1 to 7). Condition (1-1) 1.80 <fF / fBaw Conditional expression (1-2) 2.00<βFw / (-βBaw)<15.00 Condition (2) FNow<3.40 Condition (3) 1.50<βFw<15.00 Conditional expression (4) 0.00 <fBaw / fCw<1.00 Condition (5) 0.60 <Bfw / fw<4.00 Condition (6) 0.05 <Bfw / TLw<0.22 Condition (7) 0.40 <STLw / TLw<0.70 Conditional expression (8) 0.00 <TLt / TLw<1.00 Conditional expression (9) 1.00<(-f1) / fw<1.80 Conditional expression (10) 0.42<(-f1) / ft<1.20 Conditional expression (11) -3.00<(rL1R2+rL1R1) / (rL1R2-rL1R1)<-0.80 Conditional expression (12) -5.50<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-1.50 Conditional expression (13) -0.50<(rL3R2+rL3R1) / (rL3R2-rL3R1)<0.50 Conditional expression (14) 1.50<|(rLeR2+rLeR1) / (rLeR2-rLeR1)| Conditional expression (15) 75.0<νd

[0144] [Conditional Expression Corresponding Values] (First to Fourth Examples) Conditional Expression 1st Example 2nd Example 3rd Example 4th Example (1-1) 3.603 2.703 1.830 3.217 (1-2) 3.837 7.630 13.253 3.989 (2) 2.91 2.91 2.91 2.91 (3) 2.430 5.116 13.381 2.687 (4) 0.850 0.747 0.616 0.834 (5) 1.467 1.515 1.399 1.563 (6) 0.146 0.159 0.139 0.163 (7) 0.588 0.571 0.603 0.583 (8) 0.932 0.942 0.921 0.957 (9) 1.139 1.491 1.436 1.484 (10) 0.704 0.922 0.888 0.919 (11) -1.059 -1.163 -1.579 -1.237 (12) -3.333 -3.239 -2.678 -1.895 (13) 0.147 0.108 -0.310 -0.127 (14) 414.337 13.194 12.013 8.579 (15) 82.6 82.6 82.6 82.6 [Conditional Expression Corresponding Values] (Fifth to Seventh Examples) Conditional Expression 5th Example 6th Example 7th Example (1-1) 2.403 2.973 2.737 (1-2) 6.075 2.382 6.202 (2) 2.91 2.91 2.91 (3) 4.267 1.834 4.383 (4) 0.827 0.982 0.745 (5) 1.394 0.756 1.173 (6) 0.140 0.079 0.123 (7) 0.608 0.460 0.566 (8) 0.928 0.886 0.936 (9) 1.424 1.299 1.415 (10) 0.880 0.630 0.687 (11) -1.505 -1.415 -1.390 (12) -2.830 -4.843 -4.962 (13) -0.124 -0.185 0.358 (14) 32.243 2.349 5.433 (15) 82.6 82.6 82.6

[0145] 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.

[0146] The above-described examples are merely illustrative examples of the present invention, and the present invention is not limited to these.

[0147] 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.

[0148] Although examples of the variable magnification optical system of this embodiment have been shown to have a three-group configuration, a four-group configuration, a five-group configuration, and a six-group configuration, the present application is not limited to these, and variable magnification optical systems with other group configurations (e.g., seven groups, etc.) can also be configured. Specifically, a lens or lens group can 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] The aperture stop is preferably located in or near the third lens group or in or near the fourth lens group, but it is also possible to use the lens frame to fulfill that role instead of providing a member serving as an aperture stop.

[0154] 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]

[0155] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group I Image plane S Aperture stop

Claims

1. The optical system comprises a leading lens group having negative refractive power and a trailing lens group having positive refractive power, which are arranged in order from the object side along the optical axis, the leading lens group is made up of a first lens group having negative refractive power, the subsequent lens group comprises, in order from the object side, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power; the second lens group is a focusing group that moves during focusing, the third lens group, the fourth lens group, and the fifth lens group are image-side groups arranged closer to the image side than the focusing group, When the magnification is changed, the distance between the leading lens group and the trailing lens group changes, and the distance between adjacent lens groups in the trailing lens group changes, When focusing from an object at infinity to an object at a close distance, the focusing group moves toward the image side along the optical axis, The first lens group is composed of four lenses, The subsequent lens group has at least one lens that satisfies the following condition: 75.0<νd where νd is the Abbe number of the lens. Furthermore, the variable magnification optical system satisfies the following conditional expression: 1.80<fF / fBaw FNow<3.40 -5.50<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-1.50 where fF is the focal length of the focusing group fBaw: the focal length in the wide-angle end state of the lens group in the subsequent lens group, which is composed of lenses arranged on the image side from the focusing group FNow: F-number of the variable magnification optical system in the wide-angle end state rL2R1: the radius of curvature of the object-side lens surface of the second lens element from the object side of the variable magnification optical system rL2R2: the radius of curvature of the image-side lens surface of the second lens element from the object side of the variable magnification optical system

2. The optical system comprises a leading lens group having negative refractive power and a trailing lens group having positive refractive power, which are arranged in order from the object side along the optical axis, the leading lens group is made up of a first lens group having negative refractive power, the subsequent lens group comprises, in order from the object side, a second lens group having positive refractive power, a third lens group having positive refractive power, and a fourth lens group having negative refractive power, the second lens group being a focusing group that moves during focusing, and the third lens group and the fourth lens group being image-side groups that are arranged closer to the image side than the focusing group, Alternatively, the subsequent lens group may comprise, in order from the object side, a second lens group formed of one cemented lens and having positive refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, a fifth lens group having positive refractive power, and a sixth lens group having negative refractive power, wherein the second lens group is a focusing group that moves during focusing, and the third lens group, the fourth lens group, the fifth lens group, and the sixth lens group are image-side groups that are arranged closer to the image side than the focusing group, When the magnification is changed, the distance between the leading lens group and the trailing lens group changes, and the distance between adjacent lens groups in the trailing lens group changes, When focusing from an object at infinity to an object at a close distance, the focusing group moves toward the image side along the optical axis, The subsequent lens group has at least one lens that satisfies the following condition: 75.0<νd where νd is the Abbe number of the lens. Furthermore, the variable magnification optical system satisfies the following conditional expression: 1.80<fF / fBaw FNow<3.40 -5.50<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-1.50 where fF is the focal length of the focusing group fBaw: the focal length in the wide-angle end state of the lens group in the subsequent lens group, which is composed of lenses arranged on the image side from the focusing group FNow: F-number of the variable magnification optical system in the wide-angle end state rL2R1: the radius of curvature of the object-side lens surface of the second lens element from the object side of the variable magnification optical system rL2R2: the radius of curvature of the image-side lens surface of the second lens element from the object side of the variable magnification optical system

3. The optical system comprises a leading lens group having negative refractive power and a trailing lens group having positive refractive power, which are arranged in order from the object side along the optical axis, the leading lens group is made up of a first lens group having negative refractive power, the subsequent lens group comprises, in order from the object side, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power; The two lenses in the second lens group arranged on the object side are a focusing group that moves during focusing, a lens in the second lens group that is closer to the image side than the two lenses, and the third lens group; the fourth lens group and the fifth lens group are image-side groups disposed closer to the image side than the focusing group, When the magnification is changed, the distance between the leading lens group and the trailing lens group changes, and the distance between adjacent lens groups in the trailing lens group changes, When focusing from an object at infinity to an object at a close distance, the focusing group moves toward the image side along the optical axis, The subsequent lens group has at least one lens that satisfies the following condition: 75.0<νd where νd is the Abbe number of the lens. Furthermore, the variable magnification optical system satisfies the following conditional expression: 1.80<fF / fBaw FNow<3.40 -5.50<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-1.50 where fF is the focal length of the focusing group fBaw: the focal length in the wide-angle end state of the lens group in the subsequent lens group, which is composed of lenses arranged on the image side from the focusing group FNow: F-number of the variable magnification optical system in the wide-angle end state rL2R1: the radius of curvature of the object-side lens surface of the second lens element from the object side of the variable magnification optical system rL2R2: the radius of curvature of the image-side lens surface of the second lens element from the object side of the variable magnification optical system

4. The variable magnification optical system according to any one of claims 1 to 3, which satisfies the following conditional expression: 1.50<βFw<15.00 0.00<fBaw / fCw<1.00 where βFw is the magnification of the focusing group in the wide-angle end state. fCw: focal length of the image-side lens group in the wide-angle end state fBaw: the focal length in the wide-angle end state of the lens group in the subsequent lens group, which is composed of lenses arranged on the image side from the focusing group

5. 5. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.60<Bfw / fw<4.00 where fw is the focal length of the variable magnification optical system in the wide-angle end state Bfw: back focus of the variable magnification optical system in the wide-angle end state

6. an aperture stop is disposed in the subsequent lens group; 6. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.40<STLw / TLw<0.70 where TLw is the total length of the variable magnification optical system in the wide-angle end state. STLw: the distance on the optical axis from the lens surface closest to the object side of the variable magnification optical system to the aperture stop in the wide-angle end state

7. 7. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.00<TLt / TLw<1.00 where TLw is the total length of the variable magnification optical system in the wide-angle end state. TLt: total length of the variable magnification optical system in the telephoto end state

8. the leading lens group includes a first lens group arranged closest to the object, 8. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 1.00<(-f1) / fw<1.80 where f1 is the focal length of the first lens group fw: focal length of the variable magnification optical system in the wide-angle end state

9. the leading lens group includes a first lens group arranged closest to the object, 9. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.42<(-f1) / ft<1.20 where f1 is the focal length of the first lens group ft: focal length of the variable magnification optical system in the telephoto end state

10. 10. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: -3.00<(rL1R2+rL1R1) / (rL1R2-rL1R1)<-0.80 where rL1R1 is the radius of curvature of the object-side lens surface of the lens arranged closest to the object side in the variable magnification optical system. rL1R2: Radius of curvature of the image-side lens surface of the lens arranged closest to the object side in the variable magnification optical system

11. 11. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: -0.50<(rL3R2+rL3R1) / (rL3R2-rL3R1)<0.50 where rL3R1 is the radius of curvature of the object-side lens surface of the third lens element from the object side of the variable magnification optical system. rL3R2: the radius of curvature of the image-side lens surface of the third lens element from the object side of the variable magnification optical system

12. 12. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 1.50<|(rLeR2+rLeR1) / (rLeR2−rLeR1)| where rLeR1 is the radius of curvature of the object-side lens surface of the lens arranged closest to the image side in the variable magnification optical system. rLeR2: the radius of curvature of the image-side lens surface of the lens arranged closest to the image side in the variable magnification optical system

13. the leading lens group includes a first lens group arranged closest to the object, 13. The variable magnification optical system according to claim 1, wherein the first lens group moves toward the image side along the optical axis when varying magnification from the wide-angle end state to the telephoto end state.

14. 14. The variable magnification optical system according to claim 1, wherein the subsequent lens group has at least one aspherical lens.

15. An optical instrument comprising the variable magnification optical system according to any one of claims 1 to 14.

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