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 disclosed 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 succeeding lens group GB consisting of a focusing group GF and an image-side group GC located on the image side of the focusing group GF, where the focusing group GF moves along the optical axis while shifting focus from an object at infinity to a nearby object. The zoom optical system satisfies the following conditional expressions: 1.80<fF / fBaw, FNow<3.40, where fF represents a focal length of the focusing group GF, fBaw represents a focal length of an image-side lens group Gba consisting of lenses located on the image side of the focusing group GF at the wide-angle end, and FNow represents an F-number of the zoom optical system ZL at the wide-angle end.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a variable magnification optical system and an optical instrument. [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, there is a demand for suppressing fluctuations in the angle of view during focusing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-13685 A Summary of the Invention

[0004] A variable magnification optical system according to a first aspect of 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 on the image side of the focusing group, and wherein, during focusing from an object at infinity to an object at a close distance, the focusing group moves along the optical axis toward the image side, 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, 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

[0005] A variable magnification optical system according to a second aspect of 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 on the image side of the focusing group, and wherein, during focusing from an object at infinity to an object at a close distance, the focusing group moves along the optical axis toward the image side, 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 composed of the lenses arranged on the image side of the focusing group in the subsequent lens group FNow: F-number of the variable magnification optical system in the wide-angle end state

[0006] An optical device according to the present invention includes the variable magnification optical system described above. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram showing a lens configuration of a variable magnification optical system according to a first example. [Diagram 2] 2A and 2B are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focused on infinity in the wide-angle end state and in the telephoto end state, respectively. [Diagram 3] 3A and 3B are diagrams showing various aberrations in the variable magnification optical system according to Example 1 when focusing on a close object in the wide-angle end state and the telephoto end state, respectively. [Figure 4] FIG. 13 is a diagram showing a lens configuration of a variable magnification optical system according to Example 2. [Diagram 5] 5A and 5B are diagrams showing various aberrations of the variable magnification optical system according to the second example when focused on infinity in the wide-angle end state and in the telephoto end state, respectively. [Figure 6] 6A and 6B are diagrams showing various aberrations of the variable magnification optical system according to the second example when focusing on a close object in the wide-angle end state and the telephoto end state, respectively. [Figure 7] FIG. 13 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 in 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 object in the wide-angle end state and in the telephoto end state, respectively. [Figure 10] FIG. 13 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 on infinity in the wide-angle end state and in 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 focused on a close object in the wide-angle end state and the telephoto end state, respectively. [Figure 13] FIG. 13 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 in 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 object 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 in 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 object 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 on infinity in the wide-angle end state and in 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 object in the wide-angle end state and in the telephoto end state, respectively. [Figure 22] FIG. 1 is a diagram showing the configuration of a camera equipped with a variable magnification optical system according to each embodiment. [Diagram 23] 4 is a flowchart illustrating a method for manufacturing a variable magnification optical system according to each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Preferred embodiments of the present invention will be described below. 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 body 2 and a photographing lens 3 attached to the body 2. The body 2 is equipped with an image sensor 4, a body control unit (not shown) that controls the operation of the digital camera, and a liquid crystal screen 5. The photographing lens 3 is equipped with a variable magnification optical system ZL consisting of a plurality of 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 group, a motor that moves the lens group back and forth along the optical axis, a control circuit that drives the motor, and the like.

[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's operation. This camera may be a mirrorless camera or a single-lens reflex camera having a quick-return mirror.

[0010] Next, a variable magnification optical system according to the first embodiment will be described. A variable magnification optical system ZL(1) as an example of the variable magnification optical system (zoom lens) ZL according to the first embodiment has optical components as shown in FIG. It is composed of a leading lens group GA with negative refractive power and a trailing lens group GB with positive refractive power, arranged in order from the object side along the axis. When varying magnification, 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 that is arranged on the image side of the focusing group GF. When focusing from an object at infinity to a close object, the focusing group GF moves toward the image side along the optical axis.

[0011] With the above-mentioned 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 in the wide-angle end state, which is made up of lenses arranged on the image side of the focusing group GF FNow: 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 device 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. 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 consisting of the lenses arranged on the image side from the focusing group GF in the subsequent lens group GB may be referred to as the image side lens group GBa.

[0013] Conditional formula (1-1) specifies the appropriate relationship between the focal length of the focusing group GF and the focal length of the image-side lens group GBa (a lens group consisting of lenses arranged on the image side of the focusing group GF in the subsequent lens group GB) 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. By satisfying conditional formula (1-1), it is possible to reduce fluctuations in the angle of view when focusing.

[0014] If the corresponding value of conditional formula (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 formula (1-1) to 1.90, 2.00, 2.10, 2.20, 2.25, 2.30, or even 2.35, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional formula (1-1) to 10.00, 8.00, or even 6.00, the effect of this embodiment can be made more certain.

[0015] Conditional expression (2) specifies an appropriate range for the F-number of the variable magnification optical system ZL in the wide-angle end state. 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 reduce the fluctuation in the angle of view when focusing while ensuring the brightness of the optical system.

[0016] If the value of conditional expression (2) falls 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 effect of this embodiment can be made more certain.

[0017] Next, a variable magnification optical system according to the second embodiment will be described. The variable magnification optical system ZL(1) as an example of the variable magnification optical system (zoom lens) ZL according to the second embodiment is composed of 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, as shown in FIG. The distance between the group GB and the subsequent lens group GB changes. The subsequent lens group GB has a focusing group GF and an image-side group GC that is arranged on the image side of the focusing group GF. When focusing from an object at infinity to a close object, the focusing group GF moves toward the image side along the optical axis.

[0018] With the above-mentioned 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) where βFw is the 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 lenses arranged on the image side of the focusing group GF in the subsequent lens group GB FNow: 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 device 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. 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 consisting of the lenses arranged on the image side from the focusing group GF in the subsequent lens group GB may be referred to as the image side lens group GBa.

[0020] Conditional formula (1-2) specifies 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 arranged on the image side of the focusing group GF in the subsequent lens group GB) 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 formula (1-2) can reduce fluctuations in the angle of view when focusing.

[0021] If the corresponding value of conditional formula (1-2) falls outside the above range, it becomes difficult to suppress the fluctuation of the angle of view during focusing. By setting the lower limit of conditional formula (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, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional formula (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, the effect of this embodiment can be made more certain.

[0022] Conditional expression (2) specifies an appropriate range for the F-number of the variable magnification optical system ZL in the wide-angle end state. 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 reduce the fluctuation in the angle of view when focusing while ensuring the brightness of the optical system.

[0023] If the value of conditional expression (2) falls 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 effect of this embodiment can be made more certain.

[0024] It is desirable for the variable magnification optical system ZL according to the first and second embodiments to satisfy the following conditional expressions (3) and (4). 1.50<βFw<15.00 (3) 0.00 <fBaw / fCw<1.00 ···(4) where βFw is the magnification of the focusing group GF at the wide-angle end. fCw: focal length of the image-side group GC in the wide-angle end state fBaw: the focal length of the lens group GB in the wide-angle end state, which is made up of lenses arranged 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 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. By satisfying conditional expression (3), it is possible to reduce fluctuations in the angle of view when focusing.

[0026] If the corresponding value of conditional expression (3) falls outside the above range, it becomes difficult to suppress the fluctuation of 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 more certain. Also, 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 more certain.

[0027] Conditional formula (4) specifies an appropriate relationship between the focal length of the image side lens group GBa (a lens group consisting of lenses arranged on the image side of the focusing group GF in the subsequent lens group GB) in the wide-angle end state and the focal length of the image side 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 group GC in the wide-angle end state indicates the value when focusing on an object at infinity. Satisfying conditional formula (4) can reduce fluctuations in the angle of view when focusing.

[0028] If the corresponding value of 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. Also, 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 for the variable magnification optical system ZL according to the first and second embodiments to 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 the variable magnification optical system ZL at the wide-angle end state

[0030] Conditional expression (5) specifies the appropriate range of the back focus of the variable magnification optical system ZL in the wide-angle end state. The focal length of the variable magnification optical system ZL in the wide-angle end state indicates the value when focusing 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 corresponding value of 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 the amount of peripheral light. 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 made more certain. 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 made more certain.

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

[0033] Condition (6) defines an appropriate relationship between the total 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 condition (6), various aberrations such as spherical aberration in the wide-angle end state can be well corrected.

[0034] If the value of 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 made more certain. Also, 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 made more certain.

[0035] In the variable magnification optical system 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) Where TLw: total length of the variable magnification optical system ZL 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 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 corrected satisfactorily.

[0037] If the value of 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. Also, 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 for the variable magnification optical system ZL according to the first and second embodiments to satisfy the following conditional expression (8). 0.00 <TLt / TLw<1.00 ···(8) Where TLw: total length of the variable magnification optical system ZL in the wide-angle end state TLt: Total length of the variable magnification optical system ZL in the telephoto end state

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

[0040] The effects of each embodiment can be more reliably achieved 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. The effects of each embodiment can be more reliably achieved 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 satisfies 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 the variable magnification optical system ZL at the wide-angle end

[0042] Conditional expression (9) specifies the 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. The focal length of the variable magnification optical system ZL in the wide-angle end state indicates the value when focusing 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 of conditional expression (9) falls outside the above range, it becomes difficult to correct various aberrations such as spherical aberration and coma aberration 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 more reliably achieved. Also, 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 more reliably achieved.

[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 satisfies 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 the variable magnification optical system ZL at the telephoto end

[0045] Conditional expression (10) specifies the 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. 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 of conditional expression (10) falls outside the above range, it becomes difficult to correct various aberrations such as spherical aberration and coma aberration 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 made more certain. Also, 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 made more certain.

[0047] It is desirable for the variable magnification optical system ZL according to the first and second embodiments to 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 the appropriate shape factor of the lens located closest to the object side in the variable magnification optical system ZL. By satisfying condition (11), distortion can be controlled favorably. It can be corrected.

[0049] If the corresponding value of 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 -1.80, the effects of each embodiment can be more reliably achieved. Also, by setting the upper limit of conditional expression (11) to -0.85, -0.90, -0.95, or -1.00, the effects of each embodiment can be more reliably achieved.

[0050] It is desirable for the variable magnification optical system ZL according to the first and second embodiments to 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 located 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 located from the object side of the variable magnification optical system ZL

[0051] Condition (12) defines an appropriate shape factor for the second lens element from the object side of the variable magnification optical system ZL. By satisfying condition (12), coma and curvature of field can be effectively corrected.

[0052] If the corresponding value of conditional expression (12) falls outside the above range, it becomes difficult to correct coma aberration 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 -3.50, the effects of each embodiment can be more certain. Also, by setting the upper limit of conditional expression (12) to -1.60, -1.70, -1.75, -1.80, or -1.85, the effects of each embodiment can be more certain.

[0053] It is desirable for the variable magnification optical system ZL according to the first and second embodiments to 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 located 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 located from the object side of the variable magnification optical system ZL

[0054] Condition (13) defines an appropriate shape factor for the third lens element from the object side of the variable magnification optical system ZL. By satisfying condition (13), coma can be effectively corrected.

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

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

[0057] Condition (14) defines an appropriate shape factor for the lens located closest to the image side in the variable magnification optical system ZL. By satisfying condition (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 more reliably achieved.

[0059] In the variable magnification optical system ZL according to the first and second embodiments, the leading lens group GA includes a first lens group G1 arranged closest to the object, and it is preferable that the first lens group G1 moves toward the image side along the optical axis when changing magnification from the wide-angle end state to the telephoto end state. This makes it possible to characterize the variable magnification optical system ZL in the telephoto end state as having a shorter overall length than the variable magnification optical system ZL in the wide-angle end state.

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

[0061] In the variable magnification optical system ZL according to the first and second embodiments, it is desirable for the rear lens group GB to have 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) may be 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 rear 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 satisfactorily 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 more reliably achieved.

[0064] Next, referring to FIG. 23, a manufacturing method of the variable magnification optical system ZL according to the first embodiment will be outlined. First, a leading lens group GA having a negative refractive power and a trailing lens group GB having a positive refractive power are arranged in order from the object side along the optical axis (step ST1). Next, the arrangement is made so that 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 on the image side of the focusing group GF are arranged in the trailing lens group GB (step ST3). Next, the arrangement is made so that the focusing group GF moves toward the image side along the optical axis during focusing from an object at infinity to a close object (step ST4). Then, each lens is arranged in the lens barrel so as to satisfy at least the above conditional formula (1-1) and conditional formula (2) (step ST5). According to such a manufacturing method, it is possible to manufacture a variable magnification optical system with little fluctuation in the angle of view during focusing.

[0065] Next, a manufacturing method of the variable magnification optical system ZL according to the second embodiment will be outlined. The manufacturing method of the variable magnification optical system ZL according to the second embodiment is the same as the manufacturing method described in the first embodiment, so it will be described with reference to FIG. 23, which is the same as the first embodiment. First, a leading lens group GA having a negative refractive power and a trailing lens group GB having a positive refractive power are arranged in order from the object side along the optical axis (step ST1). Next, a configuration is made such that 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 on the image side of the focusing group GF are arranged in the trailing lens group GB (step ST3). Next, a configuration is made such that the focusing group GF moves toward the image side along the optical axis during focusing from an object at infinity to an object at a close distance (step ST4). Then, each lens is arranged in the lens barrel so as to satisfy at least the above conditional formula (1-2) and conditional formula (2) (step ST5). According to such a manufacturing method, it is possible to manufacture a variable magnification optical system with little fluctuation in the angle of view during focusing. EXAMPLES

[0066] The variable magnification optical system ZL according to the 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 the variable magnification optical system ZL {ZL(1) to ZL(7)} according to the first to seventh examples. In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(7) according to the first to seventh examples, the movement direction along the optical axis of the focusing group when focusing from infinity to a close-distance object is indicated by an arrow together with the word "focusing". In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(7) according to the first to seventh examples, the movement direction along the optical axis of each lens group 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 large and becoming complicated in number, the lens groups, etc. are represented by their own combinations of symbols and numbers for each embodiment. Therefore, even if the same combinations of symbols and numbers are used between embodiments, this does not mean that they have the same configuration.

[0068] Tables 1 to 7 are shown below, with Table 1 showing data on the various elements in the first embodiment, Table 2 showing data on the second embodiment, Table 3 showing data on the third embodiment, Table 4 showing data on the fourth embodiment, Table 5 showing data on the fifth embodiment, Table 6 showing data on the sixth embodiment, and Table 7 showing data on the seventh embodiment. In each embodiment, the d-line (wavelength λ=587.6 nm) and g-line (wavelength λ=435.8 nm) are selected as the targets for calculating the 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: ° (degrees), ω is half 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 focusing at infinity plus Bf, and Bf is the distance (back focus) from the last lens surface on the optical axis to the image plane I when focusing at infinity. These values ​​are shown for each of the magnification change states, the wide-angle end (W) and the telephoto end (T). In addition, in the [Overall Specifications] table, fBaw is the focal length of the image-side lens group (the lens group composed of the lenses arranged on the image side from the focusing group in the subsequent lens group) in the wide-angle end state. fCw is the focal length of the image-side group in the wide-angle end state. 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 arranged on the image side of the focusing group in the subsequent lens 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 side of 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 surfaces from the object side along the direction of light travel, and R is the radius of curvature of each optical surface (surfaces whose center of curvature is located on the image side have a positive value). (In this case, the surface spacing is the distance on the optical axis from each optical surface to the next optical surface (or image surface), nd is the refractive index of the material of the optical component with respect to the d-line, and νd is the Abbe number with the d-line of the material of the optical component as the reference. The "∞" in the radius of curvature indicates a plane or an aperture, (aperture S) indicates the aperture aperture S, and (aperture Sa) indicates the secondary aperture Sa. The description of the refractive index of air, nd=1.00000, is omitted. If the optical surface is aspheric, an * is added to the surface number, and the paraxial radius of curvature is shown in the radius of curvature 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 (sag amount) along the optical axis direction from the tangent plane at the apex 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 ratio of "×10 -n For example, 1.234E-05=1.234×10 -5 In addition, the second-order aspheric coefficient A2 is 0, When the 14th-order aspheric 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 has a surface spacing of (Di) in the [Lens Specifications] table. The [Variable Distance Data] table also shows the surface spacing when focused at infinity, 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 separation D, and other lengths are generally in "mm" unless otherwise specified; however, this is not limited to this because the optical system can provide the same optical performance even when proportionally enlarged or reduced.

[0076] The above explanation of the tables is common to all the embodiments, and therefore, 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 is a diagram showing the lens configuration of the variable magnification optical system according to the first embodiment. The variable magnification optical system ZL(1) according to the first embodiment is composed of 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, which are arranged in order from the object side along the optical axis. When changing 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, and the interval between the adjacent lens groups changes. The aperture stop S is disposed in the fourth lens group G4. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of each 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 on the image side. The negative lens L13 is made of optical glass having 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 of a negative meniscus lens L31 having a convex surface facing the object side and a positive meniscus lens L32 having a 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 negative lens L43 with a biconcave shape and a positive lens L44 with a biconvex shape, a positive lens L45 with a biconvex shape, 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 positive lens L48 with a biconcave shape and a negative lens L49 with a biconcave shape, and a negative meniscus lens L50 with a concave surface facing the object side. An image surface I is disposed on the image side of the fourth lens group G4. An aperture stop S is disposed between the positive meniscus lens L42 and the negative lens L43 in the fourth lens group G4. A secondary stop Sa is disposed 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 having a negative refractive power as a whole. The third lens group G3 and the fourth lens group G4 constitute the trailing lens group GB having 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 arranged on the image side from the focusing group GF in the trailing lens group GB, that is, the lenses of the third lens group G3 and the lenses of the fourth lens group G4, constitute the image side lens group GBa described above. When focusing from an infinite object to a close object, the third lens group G3 constituting the focusing group GF moves toward the image side along the optical axis. In addition, the positive lens L45, the positive meniscus lens L47, and the positive lens L48 of the fourth lens group G4 correspond to the 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 W.T. 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 Mid-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 when the variable magnification optical system according to the first embodiment is focused on infinity in the wide-angle end state. FIG. 2(B) is a diagram showing various aberrations when the variable magnification optical system according to the first embodiment is focused on infinity in the telephoto end state. FIG. 3(A) is a diagram showing various aberrations when the variable magnification optical system according to the first embodiment is focused on a close distance in the wide-angle end state. FIG. 3(B) is a diagram showing various aberrations when the variable magnification optical system according to the first embodiment is focused on a close distance in the telephoto end state. In each aberration diagram when focusing on infinity, FNO indicates the F-number, and Y indicates the image height. In each aberration diagram when focusing on a close distance, NA indicates the numerical aperture, and Y indicates the image height. In the spherical aberration diagram, the F-number or numerical aperture value corresponding to the maximum aperture is shown, in the astigmatism diagram and the distortion diagram, the maximum value of the image height is shown, and in the coma aberration diagram, the value of each image height is shown. 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 surface, and the dashed line indicates the meridional image surface. Note that in the aberration diagrams of the following examples, the same symbols as in this example are used, and duplicated explanations will be omitted.

[0085] From the various aberration diagrams, it can be seen that the variable power optical system of Example 1 has excellent imaging performance with various aberrations well corrected over the entire range from focusing at infinity to focusing at close distances. Therefore, even when focusing on a close object, it is possible to reduce fluctuations in the angle of view when focusing while maintaining good optical performance.

[0086] (Second Example) The second embodiment will be described with reference to FIGS. 4 to 6 and Table 2. FIG. 4 is a diagram showing the lens configuration of the variable magnification optical system according to the second embodiment. The variable magnification optical system ZL(2) according to the second embodiment is composed of 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, which are arranged in order from the object side along the optical axis. 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, and the intervals between the adjacent lens groups change. An aperture stop S is disposed in the third lens group G3.

[0087] The first lens group G1 is a negative lens group having a convex surface facing the object side, which is arranged in order from the object side along the optical axis. It is composed of a niscus lens L11, 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 on 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 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 Sa is disposed near the object side of the negative meniscus lens L21. During magnification change or focusing, the secondary aperture 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 stop S is disposed between the positive meniscus lens L32 and the negative lens L33 in the third lens group G3. A secondary stop 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 a cemented lens of a biconvex positive lens L41 and a biconcave negative lens L42, which are arranged in order from the object side along the optical axis, and a positive meniscus lens L43 with its concave surface facing the object side. An image surface I is disposed on the image side of the fourth lens group G4. The lens surface of the positive meniscus lens L43 facing the object side is aspheric. The positive lens L41 is made of optical glass having anomalous dispersion.

[0091] In this embodiment, the first lens group G1 constitutes the leading lens group GA having a 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 having 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 and the fourth lens group G4 constitute the image side group GC in the trailing lens group GB. The lenses arranged on the image side from the focusing group GF in the trailing lens group GB, that is, the lenses of the second lens group G2, the lenses of the third lens group G3, and the lenses of the fourth lens group G4, constitute the image side lens group GBa described above. 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 side along the optical axis. Moreover, 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 lens 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 W.T. 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 [Aspheric 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] Focused at infinity W M1 M2 T Focal length 14.40 16.00 18.00 23.30 Object distance ∞ ∞ ∞ ∞ 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 distance 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 distance 136 139 141 144 D8 22.71 17.82 13.02 4.81 D12 4.76 4.30 3.59 1.90 D25 1.50 1.62 1.79 1.92 Bf 21.81 24.03 26.72 34.22 [Lens group data] Group Starting surface Focal length G1 1 -21.48 G2 9 88.43 G3 13 32.84 G4 26 -65.35

[0094] FIG. 5(A) is a diagram showing various aberrations of the variable magnification optical system according to the second embodiment when focusing on infinity in the wide-angle end state. FIG. 5(B) is a diagram showing various aberrations of the variable magnification optical system according to the second embodiment when focusing on infinity in the telephoto end state. FIG. 6(A) is a diagram showing various aberrations of the variable magnification optical system according to the second embodiment when focusing on 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 the second embodiment when focusing on a close distance in the telephoto end state. From each aberration diagram, it can be seen that the variable magnification optical system according to the second embodiment has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing on infinity to focusing on a close distance. Therefore, even when focusing on a close object, it is possible to reduce the variation in the angle of view when focusing while maintaining good optical performance.

[0095] (Third Example) The third embodiment will be described with reference to FIGS. 7 to 9 and Table 3. FIG. 7 is a diagram showing the lens configuration of the variable magnification optical system according to the third embodiment. The variable magnification optical system ZL(3) according to the third embodiment is composed of 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, which are arranged in order from the object side along the optical axis. 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, and the intervals between the adjacent lens groups change. The aperture stop S is disposed between the third lens group G3 and the fourth lens group G4.

[0096] The first lens group G1 is a negative lens group having a convex surface facing the object side, which is arranged in order from the object side along the optical axis. It is composed of a niscus lens L11, a negative meniscus lens L12 with a convex surface facing the object side, and a cemented lens of 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 on the image side.

[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 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 disposed near the object side of the negative meniscus lens L31. When varying the 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 a convex surface facing the object side and a biconvex positive lens L45. An aperture diaphragm S is disposed near the object side of the negative lens L41. During magnification change, 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 having anomalous dispersion.

[0100] The fifth lens group G5 is composed of, in order from the object side along the optical axis, a cemented lens 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 disposed on the image side of the fifth lens group G5. The lens surface on the image side of the positive meniscus lens L53 is aspheric.

[0101] In this embodiment, the first lens group G1 constitutes the leading lens group GA having 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 having a positive refractive power as a whole. The positive lens L23 of 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 arranged on the image side from the focusing group GF in the trailing lens group GB, that is, the positive lens L23 of the second lens group G2, each lens of the third lens group G3, each lens of the fourth lens group G4, and each lens of the fifth lens group G5, constitute the image side lens group GBa described above. During 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 side along the optical axis. 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 W.T. 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 closest focusing 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 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 [Lens group data] Group Starting surface Focal length G1 1 -20.68 G2 8 80.626 G3 13 78.24 G4 17 30.00 G5 26 -40.50

[0104] FIG. 8(A) is a diagram showing various aberrations of the variable magnification optical system according to the third embodiment when focusing on infinity in the wide-angle end state. FIG. 8(B) is a diagram showing various aberrations of the variable magnification optical system according to the third embodiment when focusing on infinity in the telephoto end state. FIG. 9(A) is a diagram showing various aberrations of the variable magnification optical system according to the third embodiment when focusing on 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 the third embodiment when focusing on a close distance in the telephoto end state. From each aberration diagram, it can be seen that the variable magnification optical system according to the third embodiment has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing on infinity to focusing on a close distance. Therefore, even when focusing on a close object, it is possible to reduce the fluctuation in the angle of view when focusing while maintaining good optical performance.

[0105] (Fourth Example) The fourth embodiment will be described with reference to Figs. 10 to 12 and Table 4. Fig. 10 is a diagram showing the lens configuration of the variable magnification optical system according to the fourth embodiment. The variable magnification optical system ZL(4) according to the fourth embodiment is composed of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having positive refractive power, which are arranged in order from the object side along the optical axis. 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 and the third lens group G3 move toward the object side along the optical axis, and the interval between the adjacent lens groups changes. An aperture stop S is disposed in 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 on the image side. The negative lens L13 is made of optical glass having anomalous dispersion.

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

[0108] 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 negative lens L33 with a biconcave shape and a positive lens L34 with a biconvex shape, a positive lens L35 with a biconvex shape, 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 positive lens L38 with a biconcave shape and a negative lens L39 with a biconcave shape, and a positive meniscus lens L40 with a concave surface facing the object side. An image surface I is disposed on the image side of the third lens group G3. An aperture stop S is disposed between the positive meniscus lens L32 and the negative lens L33 in the third lens group G3. The lens surface of the positive meniscus lens L40 on the object side 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 having a negative refractive power as a whole. The second lens group G2 and the third lens group G3 constitute the trailing lens group GB having 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 arranged on the image side from the focusing group GF in the trailing lens group GB, that is, the lenses of the second lens group G2 and the lenses of the third lens group G3 constitute the image side lens group GBa. When focusing from an infinite object to a close object, the second lens group G2 constituting the focusing group GF moves toward the image side along the optical axis. In addition, the positive lens L35, the positive meniscus lens L37, and the positive lens L38 of the third lens group G3 correspond to the 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 W.T. 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 Side 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 Mid-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 22.54 27.74 30.59 35.22 [Lens group data] Group Starting surface Focal length G1 1 -21.401 G2 9 105.275 G3 12 39.261

[0112] FIG. 11(A) is a diagram showing various aberrations of the variable magnification optical system according to the fourth embodiment when focusing on infinity in the wide-angle end state. FIG. 11(B) is a diagram showing various aberrations of the variable magnification optical system according to the fourth embodiment when focusing on infinity in the telephoto end state. FIG. 12(A) is a diagram showing various aberrations of the variable magnification optical system according to the fourth embodiment when focusing on a close distance in the wide-angle end state. FIG. 12(B) is a diagram showing various aberrations of the variable magnification optical system according to the fourth embodiment when focusing on a close distance in the telephoto end state. From each aberration diagram, it can be seen that the variable magnification optical system according to the fourth embodiment has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing on infinity to focusing on a close distance. Therefore, even when focusing on a close object, it is possible to reduce the variation in the angle of view when focusing while maintaining good optical performance.

[0113] (Fifth Example) The fifth embodiment will be described with reference to FIGS. 13 to 15 and Table 5. FIG. 13 is a diagram showing the lens configuration of the variable magnification optical system according to the fifth embodiment. The variable magnification optical system ZL(5) according to the fifth embodiment is composed of 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, which are arranged in order from the object side along the optical axis. 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, and the interval between the adjacent lens groups changes. The 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 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 disposed near the object side of the negative meniscus lens L31. When varying the 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 a convex surface facing the object side and a biconvex positive lens L45. An aperture diaphragm S is disposed near the object side of the negative lens L41. During magnification change, 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 having anomalous dispersion.

[0118] The fifth lens group G5 is composed of, in order from the object side along the optical axis, a cemented lens 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 disposed on the image side of the fifth lens group G5. The lens surface on the image side of the positive meniscus lens L53 is aspheric.

[0119] In this embodiment, the first lens group G1 constitutes the leading lens group GA having 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 having 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 arranged on the image side from the focusing group GF in the trailing lens group GB, that is, the lenses 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 described above. When focusing from an infinite object to a close object, the second lens group G2 constituting the focusing group GF moves toward the image side along the optical axis. Moreover, the positive lens L42 and the positive lens L45 in the fourth lens group G4 correspond to the specific lens in the rear 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 W.T. 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 Side 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 according to the fifth embodiment when focusing on infinity in the wide-angle end state. FIG. 14(B) is a diagram showing various aberrations of the variable magnification optical system according to the fifth embodiment when focusing on infinity in the telephoto end state. FIG. 15(A) is a diagram showing various aberrations of the variable magnification optical system according to the fifth embodiment when focusing on a close distance in the wide-angle end state. FIG. 15(B) is a diagram showing various aberrations of the variable magnification optical system according to the fifth embodiment when focusing on a close distance in the telephoto end state. From each aberration diagram, it can be seen that the variable magnification optical system according to the fifth embodiment has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing on infinity to focusing on a close distance. Therefore, even when focusing on a close object, it is possible to reduce the fluctuation in the angle of view when focusing while maintaining good optical performance.

[0123] (Sixth Example) The sixth example will be described with reference to Figs. 16 to 18 and Table 6. Fig. 16 is a diagram showing the lens configuration of a variable magnification optical system according to the sixth example. 6) is composed of 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, arranged in order from the object side along the optical axis. When changing the 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 interval between the adjacent lens groups. The 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 in order from the object side along the optical axis, 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 of 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 lens L13 is made of optical glass having 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 a concave surface facing the object side. The third lens group G3 is composed of a biconvex positive lens L31. An aperture diaphragm S is disposed near the object side of the positive lens L31. When varying the 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 having anomalous dispersion.

[0126] The fourth lens group G4 is composed of a biconcave negative lens L41 and a positive meniscus lens L42 with a convex surface facing the object side, arranged in order from the object side along the optical axis. A secondary aperture stop Sa is disposed near the image side of the positive meniscus lens L42. When varying the 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 in order from the object side along the optical axis, 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 lens surface facing the object side of the negative lens L56 is aspheric. The positive lens L51, the positive meniscus lens L54, and the positive meniscus lens L57 are made of optical glass having anomalous dispersion.

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

[0129] In this embodiment, the first lens group G1 constitutes the leading lens group GA having 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 having 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 arranged on the image side from the focusing group GF in the trailing lens group GB, that is, the lenses of the second lens group G2, the lenses of the third lens group G3, the lenses of the fourth lens group G4, the lenses of the fifth lens group G5, and the lenses of the sixth lens group G6 constitute the image side lens group GBa described above. During focusing from an object at infinity to a close object, the second lens group G2 constituting the focusing group GF moves toward the image side along the optical axis. The negative lens L56 and the positive meniscus lens L57 of the fifth lens group G5 move toward the object side along the optical axis. The positive lens L31 of the third lens group G3 and the positive lens L51, the positive meniscus lens L54, and the positive meniscus lens L57 of the fifth lens group G5 correspond to the specific lens 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 W.T. 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 Side 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 according to Example 6 when focusing on infinity in the wide-angle end state. FIG. 17(B) is a diagram showing various aberrations of the variable magnification optical system according to Example 6 when focusing on infinity in the telephoto end state. FIG. 18(A) is a diagram 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. FIG. 18(B) is a diagram showing various aberrations of the variable magnification optical system according to Example 6 when focusing on a close distance in the telephoto end state. From each aberration diagram, it can be seen that the variable magnification optical system according to Example 6 has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing on infinity to focusing on a close distance. Therefore, even when focusing on a close object, it is possible to reduce the fluctuation in the angle of view when focusing while maintaining good optical performance.

[0133] (Seventh Example) The seventh embodiment will be described with reference to FIGS. 19 to 21 and Table 7. FIG. 19 is a diagram showing the lens configuration of the variable magnification optical system according to the seventh embodiment. The variable magnification optical system ZL(7) according to the seventh embodiment is composed of 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, which are arranged in order from the object side along the optical axis. 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, and the interval between the adjacent lens groups changes. The 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 on the image side. The negative lens L13 is made of optical glass having 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 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 a negative meniscus lens L31 with a concave surface facing the object side, a biconcave negative lens L32, and a biconvex positive lens L33, arranged in order from the object side along the optical axis. An aperture stop S is disposed near the object side of the negative meniscus lens L31. A secondary stop Sa is disposed near the image side of the positive lens L33. When varying the magnification, the aperture stop S and the secondary stop Sa moves along the optical axis together with the third lens group G3.

[0137] 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 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 lens surface of the negative lens L46 facing the image side is aspheric. The positive lens L42 and the positive lens L43 are made of optical glass having anomalous dispersion.

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

[0139] In this embodiment, the first lens group G1 constitutes the leading lens group GA having 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 having 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 in 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 in the trailing lens group GB. The lenses arranged on the image side from the focusing group GF in the trailing lens group GB, that is, the lenses 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 described above. During focusing from an object at infinity to an object at a close distance, the negative meniscus lens L21 and the positive lens L22 of the second lens group G2 constituting the focusing group GF move toward the image side along the optical axis. During focusing from an object at infinity to an object at a close distance, the positive lens L45 and the negative lens L46 of the fourth lens group G4 constituting the second focusing group GF2 move toward the object side along the optical axis. The positive lens L42 and the positive lens L43 of the fourth lens group G4 correspond to the specific lens 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 W.T. 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 Side 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 according to Example 7 when focusing on infinity in the wide-angle end state. FIG. 20(B) is a diagram showing various aberrations of the variable magnification optical system according to Example 7 when focusing on infinity in the telephoto end state. FIG. 21(A) is a diagram 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. FIG. 21(B) is a diagram showing various aberrations of the variable magnification optical system according to Example 7 when focusing on a close distance in the telephoto end state. From each aberration diagram, it can be seen that the variable magnification optical system according to Example 7 has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing on infinity to focusing on a close distance. Therefore, even when focusing on a close object, it is possible to reduce the variation in the angle of view when focusing while maintaining good optical performance.

[0143] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below. In this table, values ​​corresponding to conditional expressions (1-1), (1-2), and (2) to (14) are shown for all examples (Examples 1 to 7). ) are summarized below. 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 Condition (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 Condition (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-mentioned embodiments are merely examples of the present invention, and the present invention is not limited to these.

[0147] The following contents can be appropriately adopted within a range that does not impair the optical performance of the variable magnification optical system of this embodiment.

[0148] Although three-group, four-group, five-group, and six-group configurations have been shown as examples of the variable magnification optical system of this embodiment, the present application is not limited thereto, and a variable magnification optical system of other group configurations (e.g., seven groups, etc.) can also be configured. Specifically, a lens or lens group may be added to the most object side or the most image 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 or 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 an object at a close distance. The focusing lens group can also be applied to 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 (rocked) in a plane including the optical axis to serve as an anti-vibration lens group that corrects image blur caused by camera shake.

[0151] The lens surface may be spherical or flat, or aspherical. A spherical or flat lens surface is preferable because it facilitates lens processing and assembly adjustment, and prevents deterioration of optical performance due to errors in processing and assembly adjustment. It is also preferable because there is little deterioration in image quality even if the image plane is shifted.

[0152] When the lens surface is aspheric, the aspheric surface may be any of the following: an aspheric surface formed by grinding, a glass molded aspheric surface formed by molding glass into an aspheric shape, or a composite aspheric surface formed by molding a resin into an aspheric 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 diaphragm 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 diaphragm.

[0154] Each lens surface may be coated with an anti-reflection coating having 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 1st lens group G2 2nd 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 a negative refractive power and a trailing lens group having a positive refractive power, which are arranged in order from the object side along an optical axis, When the magnification is changed, the distance between the leading lens group and the trailing lens group changes. the subsequent lens group includes a focusing group and an image-side group disposed on the image side of the focusing group, 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, A variable magnification optical system that satisfies the following condition: 1.80<fF / fBaw 0.00<fBaw / fCw<1.00 where fF is the focal length of the focusing group. fBaw: focal length in the wide-angle end state of the lens group composed of the lens arranged on the image side of the focusing group in the subsequent lens group fCw: the focal length of the image-side lens group in the wide-angle end state fBaw: focal length in the wide-angle end state of the lens group composed of the lens arranged on the image side of the focusing group in the subsequent lens group

2. 2. The variable magnification optical system according to claim 1, wherein the lens group arranged closest to the object side among the subsequent lens groups includes the focusing group.

3. the leading lens group is a first lens group having a negative refractive power, the subsequent lens group includes, in order from the object side, a second lens group having positive refractive power and a third lens group having positive refractive power; the focusing group comprises the second lens, 2. The variable magnification optical system according to claim 1, wherein the third lens group comprises, in order from the object side, a cemented lens made of a negative lens arranged on the object side and a positive lens arranged on the image side, a cemented lens made of a negative lens arranged on the object side and a positive lens arranged on the image side, a positive lens, and a cemented lens made of a negative lens arranged on the object side and a positive lens arranged on the image side.

4. 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 1.50<βFw<15.00 where βFw is the magnification of the focusing group in the wide-angle end state. fCw: the focal length of the image-side lens group in the wide-angle end state fBaw: focal length in the wide-angle end state of the lens group composed of the lens arranged on the image side of the focusing group in the subsequent lens group

5. 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 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. 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 0.05<Bfw / TLw<0.22 where TLw is the total 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

7. An aperture stop is disposed in the subsequent lens group; 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 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 in the wide-angle end state to the aperture stop

8. 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 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

9. the leading lens group includes a first lens group disposed closest to the object, 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 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

10. the leading lens group includes a first lens group disposed closest to the object, 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 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

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

12. 2. The variable magnification optical system according to claim 1, which satisfies the following condition: -5.50<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-1.50 where rL2R1 is the radius of curvature of the object-side lens surface of the second lens located 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 located from the object side of the variable magnification optical system

13. 2. The variable magnification optical system according to claim 1, which satisfies the following condition: -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 located 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 located from the object side of the variable magnification optical system

14. 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 1.50<|(rLeR2+rLeR1) / (rLeR2−rLeR1)| where rLeR1 is the radius of curvature of the object-side lens surface of the lens disposed closest to the image side of 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 of the variable magnification optical system

15. the leading lens group includes a first lens group disposed closest to the object, 2. The variable magnification optical system according to claim 1, wherein, when varying magnification from the wide-angle end state to the telephoto end state, the first lens group moves toward the image side along the optical axis.

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

17. 2. The variable magnification optical system according to claim 1, wherein the subsequent lens group has at least one lens that satisfies the following condition: 1 / 2 ... 75.0<νd where νd is the Abbe number of the lens.

18. An optical instrument comprising the variable magnification optical system according to any one of claims 1 to 16.

Images