Variable power optical system, optical apparatus and method for manufacturing variable power optical system

Abstract

To provide a variable power optical system compact yet and excellent in optical performance.SOLUTION: A variable power optical system ZL consists of a first lens group G1 having negative refractive power; and a rear group GR having at least three lens groups. A space between lens groups adjacent to each other changes when varying power; at least one of the at least three lens groups in the rear group GR is a focusing group GF having negative refractive power and moving along the optical axis when focusing; and the following conditional expression is satisfied, 1.00<fFRw / (-fF)<7.00, where fFRw: the focal distance of a lens group constituted of lenses arranged on the image side from the focusing group GF in a wide angle end state, and fF: the focal distance of the focusing group GF.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a variable magnification optical system, an optical instrument, and a method for manufacturing a variable magnification optical system. [Background technology]

[0002] Variable magnification optical systems suitable for photo cameras, electronic still cameras, video cameras, etc. have been proposed in the past (see, for example, Patent Document 1). However, it is difficult to achieve good optical performance while making such variable magnification optical systems compact. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 012638 Summary of the Invention

[0004] A first variable magnification optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a first lens group having negative refractive power and a rear group having at least one lens group, wherein the spacing between adjacent lens groups changes during magnification variation, and at least a portion of any of the lens groups in the at least one lens group in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, and satisfies the following conditional expression: 1.50 <ft / (-fF)<10.00 where ft is the focal length of the variable magnification optical system in the telephoto end state fF: focal length of the focusing group

[0005] A second variable magnification optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a first lens group having negative refractive power and a rear group having at least one lens group, wherein the spacing between adjacent lens groups changes during magnification variation, and at least a portion of any one of the at least one lens group in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, and satisfies the following conditional expression: 0.70 <fw / (-fF)<7.00 where fw is the focal length of the variable magnification optical system in the wide-angle end state fF: focal length of the focusing group

[0006] A third variable magnification optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a first lens group having negative refractive power and a rear group having at least one lens group, wherein the spacing between adjacent lens groups changes during magnification variation, and at least a portion of any one of the at least one lens group in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, and satisfies the following conditional expression: 1.00 <fFRw / (-fF)<7.00 where fFRw is the focal length of the lens group formed of lenses arranged closer to the image than the focusing group in the wide-angle end state. fF: focal length of the focusing group

[0007] A fourth variable magnification optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a first lens group having negative refractive power and a rear group having at least one lens group, wherein the spacing between adjacent lens groups changes during magnification variation, and at least a portion of any one of the at least one lens group in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, and satisfies the following conditional expression: 1.00 <fFRt / (-fF)<7.00 where fFRt is the focal length of the lens group formed of lenses arranged closer to the image than the focusing group in the telephoto end state. fF: focal length of the focusing group

[0008] An optical apparatus according to the present invention is configured to include the variable magnification optical system described above.

[0009] A first method for manufacturing a variable magnification optical system according to the present invention is a method for manufacturing a variable magnification optical system consisting of a first lens group having negative refractive power and a rear group having at least one lens group, arranged in order from the object side along the optical axis, wherein the spacing between adjacent lens groups changes during magnification variation, and at least a portion of any of the lens groups in the at least one lens group in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, and wherein each lens is arranged within the lens barrel so as to satisfy the following conditional expression: 1.50 <ft / (-fF)<10.00 where ft is the focal length of the variable magnification optical system in the telephoto end state fF: focal length of the focusing group

[0010] A second manufacturing method of a variable magnification optical system according to the present invention is a manufacturing method of a variable magnification optical system consisting of a first lens group having negative refractive power and a rear group having at least one lens group, arranged in order from the object side along the optical axis, wherein the spacing between adjacent lens groups changes during magnification variation, and at least a portion of any of the lens groups in the at least one lens group in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, and wherein each lens is arranged within the lens barrel so as to satisfy the following conditional expression: 0.70 <fw / (-fF)<7.00 where fw is the focal length of the variable magnification optical system in the wide-angle end state fF: focal length of the focusing group

[0011] A third method for manufacturing a variable magnification optical system according to the present invention is a method for manufacturing a variable magnification optical system consisting of a first lens group having negative refractive power and a rear group having at least one lens group, arranged in order from the object side along the optical axis, wherein the spacing between adjacent lens groups changes during magnification variation, and at least a portion of any of the lens groups in the at least one lens group in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, and wherein each lens is arranged within the lens barrel so as to satisfy the following conditional expression: 1.00 <fFRw / (-fF)<7.00 where fFRw is the focal length of the lens group formed of lenses arranged closer to the image than the focusing group in the wide-angle end state. fF: focal length of the focusing group

[0012] A fourth method for manufacturing a variable magnification optical system according to the present invention is a method for manufacturing a variable magnification optical system consisting of a first lens group having negative refractive power and a rear group having at least one lens group, arranged in order from the object side along the optical axis, wherein the spacing between adjacent lens groups changes during magnification variation, and at least a portion of any of the lens groups in the at least one lens group in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, and wherein each lens is arranged within the lens barrel so as to satisfy the following conditional expression: 1.00 <fFRt / (-fF)<7.00 where fFRt is the focal length of the lens group formed of lenses arranged closer to the image than the focusing group in the telephoto end state. fF: focal length of the focusing group [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram showing the lens configuration of a variable magnification optical system according to Example 1. [Figure 2] 2A and 2B are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 3] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 2. [Figure 4] 4A and 4B are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 5] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 3. [Figure 6] 6A and 6B are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 7] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 4. [Figure 8] 8A and 8B 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 the telephoto end state, respectively. [Figure 9] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 5. [Figure 10] 10A and 10B are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 11] FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system according to Example 6. [Figure 12] 12A and 12B are diagrams showing various aberrations of the variable magnification optical system according to Example 6 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 13] 1 is a diagram showing the configuration of a camera equipped with a variable magnification optical system according to each embodiment. [Figure 14] 10 is a flowchart illustrating a method for manufacturing a variable magnification optical system according to each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will now be described. First, a camera (optical device) equipped with a variable magnification optical system according to each embodiment will be described with reference to FIG. 13. As shown in FIG. 13, this camera 1 is composed of a main body 2 and a photographic lens 3 attached to the main body 2. The main body 2 includes an image sensor 4, a main body control unit (not shown) that controls the operation of the digital camera, and an LCD screen 5. The photographic lens 3 includes a variable magnification optical system ZL consisting of multiple lens groups, and a lens position control mechanism (not shown) that controls the position of each lens group. The lens position control mechanism is composed of a sensor that detects the position of the lens groups, a motor that moves the lens groups back and forth along the optical axis, a control circuit that drives the motor, etc.

[0015] 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 LCD screen 5 in response to a user operation. Note that this camera may be a mirrorless camera or a single-lens reflex camera with a quick-return mirror. Also, the variable magnification optical system ZL shown in FIG. 13 is a schematic representation of a variable magnification optical system provided in the photographing lens 3, and the lens configuration of the variable magnification optical system ZL is not limited to this configuration.

[0016] Next, a variable magnification optical system according to the first embodiment will be described. A variable magnification optical system ZL(1), which is an example of a variable magnification optical system (zoom lens) ZL according to the first embodiment, is composed of, as shown in FIG. 1, a first lens group G1 having negative refractive power and a rear group GR having at least one lens group, arranged in order from the object side along the optical axis. The spacing between adjacent lens groups changes during magnification. Furthermore, at least a portion of one of the lens groups in the at least one lens group in the rear group GR is a focusing group GF having negative refractive power that moves along the optical axis during focusing.

[0017] With the above-described configuration, the variable-magnification optical system ZL according to the first embodiment satisfies the following conditional expression (1). 1.50 <ft / (-fF)<10.00 ···(1) where ft is the focal length of the variable magnification optical system ZL at the telephoto end fF: focal length of focusing group GF

[0018] According to the first embodiment, it is possible to obtain a variable magnification optical system that is small yet has good optical performance, and an optical apparatus equipped with this variable magnification optical system. The variable magnification optical system ZL according to the first embodiment may be the variable magnification optical system ZL(2) shown in Fig. 3, the variable magnification optical system ZL(3) shown in Fig. 5, the variable magnification optical system ZL(4) shown in Fig. 7, the variable magnification optical system ZL(5) shown in Fig. 9, or the variable magnification optical system ZL(6) shown in Fig. 11.

[0019] Conditional formula (1) defines the appropriate relationship between the focal length of the variable magnification optical system ZL at the telephoto end and the focal length of the focusing group GF. By satisfying conditional formula (1), it is possible to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on close objects, while still maintaining a compact size.

[0020] If the value corresponding to conditional expression (1) falls outside the above range, the amount of movement of the focusing group GF becomes large, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on a close object. The effects of this embodiment can be further enhanced by setting the upper limit of conditional expression (1) to 8.50, 7.00, 6.00, 5.00, 4.75, 4.50, 4.25, 4.00, 3.85, or even 3.70. Furthermore, the effects of this embodiment can be further enhanced by setting the lower limit of conditional expression (1) to 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, or even 1.95.

[0021] Next, a variable magnification optical system according to the second embodiment will be described. A variable magnification optical system ZL(1), which is an example of a variable magnification optical system (zoom lens) ZL according to the second embodiment, is composed of, as shown in FIG. 1, a first lens group G1 having negative refractive power and a rear group GR having at least one lens group, arranged in order from the object side along the optical axis. The spacing between adjacent lens groups changes during magnification. Furthermore, at least a portion of one of the lens groups in the at least one lens group in the rear group GR is a focusing group GF having negative refractive power that moves along the optical axis during focusing.

[0022] With the above-described configuration, the variable-magnification optical system ZL according to the second embodiment satisfies the following conditional expression (2). 0.70 <fw / (-fF)<7.00 ···(2) where fw is the focal length of the variable magnification optical system ZL at the wide-angle end fF: focal length of focusing group GF

[0023] According to the second embodiment, it is possible to obtain a variable magnification optical system that is small yet has good optical performance, and an optical apparatus equipped with this variable magnification optical system. The variable magnification optical system ZL according to the second embodiment may be the variable magnification optical system ZL(2) shown in Fig. 3, the variable magnification optical system ZL(3) shown in Fig. 5, the variable magnification optical system ZL(4) shown in Fig. 7, the variable magnification optical system ZL(5) shown in Fig. 9, or the variable magnification optical system ZL(6) shown in Fig. 11.

[0024] Conditional expression (2) defines the appropriate relationship between the focal length of the variable magnification optical system ZL in the wide-angle end state and the focal length of the focusing group GF. By satisfying conditional expression (2), it is possible to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on close objects, while still maintaining a compact size.

[0025] If the value corresponding to conditional expression (2) falls outside the above range, the amount of movement of the focusing group GF becomes large, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on a close object. The effects of this embodiment can be further enhanced by setting the upper limit of conditional expression (2) to 6.50, 6.00, 5.50, 5.00, 4.50, 4.00, 3.50, 3.00, 2.75, 2.50, 2.35, or even 2.25. The effects of this embodiment can be further enhanced by setting the lower limit of conditional expression (2) to 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, or even 1.15.

[0026] Next, a variable magnification optical system according to a third embodiment will be described. A variable magnification optical system ZL(1), which is an example of a variable magnification optical system (zoom lens) ZL according to the third embodiment, is composed of, as shown in FIG. 1, a first lens group G1 having negative refractive power and a rear group GR having at least one lens group, arranged in order from the object side along the optical axis. The spacing between adjacent lens groups changes during magnification. Furthermore, at least a portion of one of the lens groups in the at least one lens group in the rear group GR is a focusing group GF having negative refractive power that moves along the optical axis during focusing.

[0027] With the above-described configuration, the variable-magnification optical system ZL according to the third embodiment satisfies the following conditional expression (3). 1.00 <fFRw / (-fF)<7.00 ···(3) where fFRw is the focal length of the lens group consisting of lenses arranged closer to the image than the focusing group GF in the wide-angle end state. fF: focal length of focusing group GF

[0028] According to the third embodiment, it is possible to obtain a variable magnification optical system that is small yet has good optical performance, and an optical apparatus equipped with this variable magnification optical system. The variable magnification optical system ZL according to the third embodiment may be the variable magnification optical system ZL(2) shown in Fig. 3, the variable magnification optical system ZL(3) shown in Fig. 5, the variable magnification optical system ZL(4) shown in Fig. 7, the variable magnification optical system ZL(5) shown in Fig. 9, or the variable magnification optical system ZL(6) shown in Fig. 11.

[0029] Conditional expression (3) defines an appropriate relationship between the focal length of the lens group composed of lenses arranged closer to the image than the focusing group GF in the wide-angle end state and the focal length of the focusing group GF. Hereinafter, the lens group composed of lenses arranged closer to the image than the focusing group GF may be referred to as the image-side lens group GFR. By satisfying conditional expression (3), it is possible to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on close objects, while maintaining a compact size.

[0030] If the corresponding value of conditional expression (3) exceeds the upper limit, the focal length of the focusing group GF becomes too short relative to the focal length of the image-side lens group GFR, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on a close object. The effects of this embodiment can be further ensured by setting the upper limit of conditional expression (3) to 6.50, 6.00, 5.50, 5.00, 4.50, 4.00, 3.50, 3.25, 3.00, 2.75, or even 2.50.

[0031] If the corresponding value of conditional expression (3) falls below the lower limit, the amount of movement of the focusing group GF becomes large, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on a close object. By setting the lower limit of conditional expression (3) to 1.10, 1.20, 1.30, 1.40, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, or even 1.80, the effects of this embodiment can be further ensured.

[0032] Next, a variable magnification optical system according to a fourth embodiment will be described. A variable magnification optical system ZL(1), which is an example of a variable magnification optical system (zoom lens) ZL according to the fourth embodiment, is composed of, as shown in FIG. 1, a first lens group G1 having negative refractive power and a rear group GR having at least one lens group, arranged in order from the object side along the optical axis. The spacing between adjacent lens groups changes during magnification. Furthermore, at least a portion of one of the lens groups in the at least one lens group in the rear group GR is a focusing group GF having negative refractive power that moves along the optical axis during focusing.

[0033] With the above-described configuration, the variable-magnification optical system ZL according to the fourth embodiment satisfies the following conditional expression (4). 1.00 <fFRt / (-fF)<7.00 ···(4) where fFRt is the focal length of the lens group that is composed of lenses that are arranged closer to the image than the focusing group GF in the telephoto end state. fF: focal length of focusing group GF

[0034] According to the fourth embodiment, it is possible to obtain a variable magnification optical system that is small yet has good optical performance, and an optical apparatus equipped with this variable magnification optical system. The variable magnification optical system ZL according to the fourth embodiment may be the variable magnification optical system ZL(2) shown in Fig. 3, the variable magnification optical system ZL(3) shown in Fig. 5, the variable magnification optical system ZL(4) shown in Fig. 7, the variable magnification optical system ZL(5) shown in Fig. 9, or the variable magnification optical system ZL(6) shown in Fig. 11.

[0035] Conditional expression (4) defines an appropriate relationship between the focal length of the focusing group GF and the focal length of the lens group (image-side lens group GFR) composed of lenses arranged closer to the image than the focusing group GF in the maximum telephoto state. By satisfying conditional expression (4), it is possible to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on close objects, while maintaining a compact size.

[0036] If the corresponding value of conditional expression (4) exceeds the upper limit, the focal length of the focusing group GF becomes too short relative to the focal length of the image-side lens group GFR, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on a close object. The effects of this embodiment can be further ensured by setting the upper limit of conditional expression (4) to 6.50, 6.00, 5.50, 5.00, 4.50, 4.00, 3.50, 3.25, 3.00, 2.75, or even 2.50.

[0037] If the corresponding value of conditional expression (4) falls below the lower limit, the amount of movement of the focusing group GF becomes large, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on a close object. By setting the lower limit of conditional expression (4) to 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, or even 1.95, the effects of this embodiment can be further ensured.

[0038] It is desirable that the variable magnification optical systems ZL according to the first to fourth embodiments satisfy the following conditional expression (5). 0.50 <fRw / (-fF)<4.00 ···(5) where fRw is the focal length of the rear group GR at the wide-angle end

[0039] Condition (5) defines the appropriate relationship between the focal length of the rear group GR and the focal length of the focusing group GF at the maximum wide-angle position. By satisfying condition (5), various aberrations can be effectively corrected despite the compact size.

[0040] If the value corresponding to conditional expression (5) falls outside the above range, it becomes difficult to correct various aberrations while miniaturizing the variable-magnification optical system ZL. By setting the upper limit of conditional expression (5) to 3.75, 3.50, 3.25, 3.00, 2.75, 2.50, 2.25, 2.00, 1.90, 1.80, or even 1.70, the effects of each embodiment can be further ensured. Furthermore, by setting the lower limit of conditional expression (5) to 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, or even 0.90, the effects of each embodiment can be further ensured.

[0041] It is desirable that the variable magnification optical systems ZL according to the first to fourth embodiments satisfy the following conditional expression (6). 0.50 <fRt / (-fF)<5.00 ···(6) where fRt is the focal length of the rear group GR at the telephoto end

[0042] Condition (6) defines the appropriate relationship between the focal length of the rear group GR at the maximum telephoto position and the focal length of the focusing group GF. By satisfying condition (6), various aberrations can be effectively corrected despite the compact size.

[0043] If the value corresponding to conditional expression (6) falls outside the above range, it becomes difficult to correct various aberrations while miniaturizing the variable-magnification optical system ZL. By setting the upper limit of conditional expression (6) to 4.75, 4.50, 4.25, 4.00, 3.75, 3.50, 3.25, 3.00, 2.75, 2.50, or even 2.25, the effects of each embodiment can be further ensured. Furthermore, by setting the lower limit of conditional expression (6) to 0.60, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, or even 1.15, the effects of each embodiment can be further ensured.

[0044] In the variable magnification optical systems ZL according to the first to fourth embodiments, it is desirable that at least one lens group in the rear group GR is made up of multiple lens groups, which allows for good correction of field curvature.

[0045] In the variable magnification optical systems ZL according to the first to fourth embodiments, it is desirable that at least one lens group in the rear group GR includes a second lens group G2 having positive refractive power that is positioned closest to the object side of the rear group GR, thereby enabling excellent correction of spherical aberration and coma.

[0046] In the variable magnification optical systems ZL according to the first to fourth embodiments, it is desirable that at least one lens group in the rear group GR includes a final lens group GE having positive refractive power and located closest to the image side of the rear group GR, thereby enabling excellent correction of field curvature.

[0047] It is desirable that the variable magnification optical systems ZL according to the first to fourth embodiments satisfy the following conditional expression (7). 0.10 <fRPF / fRPR<0.60 ···(7) However, fRPF: the focal length of the lens group closest to the object that has positive refractive power among at least one lens group in the rear group GR. fRPR: the focal length of the lens group closest to the image among at least one lens group in the rear group GR that has positive refractive power

[0048] Conditional expression (7) defines an appropriate relationship between the focal length of the lens group having positive refractive power and located closest to the object among the at least one lens group in the rear group GR, and the focal length of the lens group having positive refractive power and located closest to the image among the at least one lens group in the rear group GR. By satisfying conditional expression (7), it is possible to achieve good correction of curvature of field, spherical aberration, coma, and other aberrations while maintaining a compact size.

[0049] If the value corresponding to conditional expression (7) exceeds the upper limit, the focal length of the lens group having positive refractive power in the rear group GR that is closest to the image becomes short, making it difficult to correct curvature of field. By setting the upper limit of conditional expression (7) to 0.55, 0.50, 0.48, 0.45, 0.43, or even 0.40, the effects of each embodiment can be more reliably achieved.

[0050] If the value corresponding to conditional expression (7) falls below the lower limit, the focal length of the lens group having positive refractive power in the rear group GR that is closest to the object becomes short, making it difficult to correct spherical aberration and coma. By setting the lower limit of conditional expression (7) to 0.13, 0.15, 0.18, or even 0.20, the effects of each embodiment can be more reliably achieved.

[0051] It is desirable that the variable magnification optical systems ZL according to the first to fourth embodiments satisfy the following conditional expression (8). 0.50 <fRPF / (-fF)<3.00 ···(8) However, fRPF: the focal length of the lens group closest to the object that has positive refractive power among at least one lens group in the rear group GR.

[0052] Conditional expression (8) defines an appropriate relationship between the focal length of the focusing group GF and the focal length of the lens group having positive refractive power that is closest to the object, among at least one lens group in the rear group GR. By satisfying conditional expression (8), it is possible to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on close objects, even while maintaining a compact size.

[0053] If the corresponding value of conditional expression (8) exceeds the upper limit, the focal length of the focusing group GF becomes short, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature when focusing on a close object. By setting the upper limit of conditional expression (8) to 2.75, 2.50, 2.25, 2.00, 1.85, 1.70, 1.60, 1.55, 1.50, or even 1.48, the effects of each embodiment can be further ensured.

[0054] If the value corresponding to conditional expression (8) falls below the lower limit, the focal length of the lens group having positive refractive power in the rear group GR that is closest to the object will become short, making it difficult to correct spherical aberration and coma. By setting the lower limit of conditional expression (8) to 0.53, 0.55, 0.58, 0.60, 0.63, 0.65, or even 0.68, the effects of each embodiment can be more reliably achieved.

[0055] It is desirable that the variable magnification optical systems ZL according to the first to fourth embodiments satisfy the following conditional expression (9). 0.05 <Bfw / fRPR<0.35 ···(9) Bfw: back focus of the variable magnification optical system ZL in the wide-angle end state fRPR: the focal length of the lens group closest to the image among at least one lens group in the rear group GR that has positive refractive power

[0056] Conditional expression (9) defines an appropriate relationship between the back focus of the variable magnification optical system ZL in the wide-angle end state and the focal length of the lens group having positive refractive power and located closest to the image side among at least one lens group in the rear group GR. By satisfying conditional expression (9), it is possible to effectively correct various aberrations such as field curvature while maintaining a compact size. Note that in each embodiment, the back focus of the variable magnification optical system ZL is the distance on the optical axis (air-equivalent distance) from the lens surface of the variable magnification optical system ZL located closest to the image side to the image plane I when focused at infinity.

[0057] If the value corresponding to conditional expression (9) exceeds the upper limit, the focal length of the lens group having positive refractive power in the rear group GR that is closest to the image becomes short, making it difficult to correct field curvature. By setting the upper limit of conditional expression (9) to 0.33, 0.30, 0.28, 0.25, or even 0.23, the effects of each embodiment can be more reliably achieved.

[0058] If the value corresponding to conditional expression (9) falls below the lower limit, the focal length of the lens group having positive refractive power in the rear group GR that is closest to the image becomes too long, making it difficult to sufficiently correct field curvature. By setting the lower limit of conditional expression (9) to 0.06, or even 0.08, the effects of each embodiment can be made more certain.

[0059] In the variable magnification optical systems ZL according to the first to fourth embodiments, it is desirable that the lens in the rear group GR located closest to the object side be a positive lens, which allows for good correction of field curvature.

[0060] The variable magnification optical systems ZL according to the first to fourth embodiments preferably have a diaphragm disposed between the first lens group G1 and the rear lens group GR, thereby enabling good correction of coma.

[0061] It is desirable that the variable magnification optical systems ZL according to the first to fourth embodiments satisfy the following conditional expression (10). 60.00°<2ωw<90.00° ···(10) However, 2ωw: the total angle of view of the variable magnification optical system ZL in the wide-angle end state

[0062] Conditional expression (10) defines an appropriate range for the total angle of view of the variable magnification optical system ZL in the wide-angle end state. Satisfying conditional expression (10) is preferable because it makes it possible to obtain a variable magnification optical system that is compact yet has good optical performance. By setting the upper limit of conditional expression (10) to 85.00°, 83.00°, 80.00°, or even 78.00°, the effects of each embodiment can be made more certain. By setting the lower limit of conditional expression (10) to 63.00°, 65.00°, 68.00°, or even 70.00°, the effects of each embodiment can be made more certain.

[0063] It is desirable that the variable magnification optical systems ZL according to the first to fourth embodiments satisfy the following conditional expression (11). 1.50<(-f1) / fRw<3.00 (11) where f1 is the focal length of the first lens group G1 fRw: focal length of rear group GR at wide-angle end

[0064] Conditional expression (11) defines the appropriate relationship between the focal length of the first lens group G1 and the focal length of the rear group GR at the wide-angle end. By satisfying conditional expression (11), it is possible to obtain good optical performance over the entire zoom range, despite the compact size.

[0065] If the corresponding value of conditional expression (11) exceeds the upper limit, it becomes difficult to correct spherical aberration and coma. By setting the upper limit of conditional expression (11) to 2.90, 2.80, 2.70, 2.60, 2.50, 2.40, 2.30, 2.20, 2.10, or even 2.00, the effects of each embodiment can be further ensured.

[0066] If the corresponding value of conditional expression (11) falls below the lower limit, it becomes difficult to correct spherical aberration and curvature of field. By setting the lower limit of conditional expression (11) to 1.55, 1.60, 1.65, 1.70, 1.75, or even 1.80, the effects of each embodiment can be further ensured.

[0067] It is desirable that the variable magnification optical systems ZL according to the first to fourth embodiments satisfy the following conditional expression (12). 0.50<(-f1) / fRt<2.50 (12) where f1 is the focal length of the first lens group G1 fRt: focal length of rear group GR at telephoto end

[0068] Conditional expression (12) defines the appropriate relationship between the focal length of the first lens group G1 and the focal length of the rear group GR at the telephoto end. By satisfying conditional expression (12), it is possible to obtain good optical performance over the entire zoom range, despite the compact size.

[0069] If the corresponding value of conditional expression (12) exceeds the upper limit, it becomes difficult to correct spherical aberration and coma. By setting the upper limit of conditional expression (12) to 2.40, 2.30, 2.20, 2.10, 2.00, 1.90, 1.80, 1.70, or even 1.60, the effects of each embodiment can be further ensured.

[0070] If the corresponding value of conditional expression (12) falls below the lower limit, it becomes difficult to correct spherical aberration and curvature of field. By setting the lower limit of conditional expression (12) to 0.55, 0.65, 0.75, 0.85, 0.95, 1.00, 1.10, 1.20, 1.30, or even 1.40, the effects of each embodiment can be further ensured.

[0071] Next, a manufacturing method for the variable magnification optical system ZL according to the first embodiment will be outlined with reference to FIG. 14. First, a first lens group G1 having negative refractive power and a rear group GR having at least one lens group are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is made in which the spacing between adjacent lens groups changes during magnification (Step ST2). Next, at least a portion of at least one lens group in the rear group GR is arranged to become a focusing group GF having negative refractive power that moves along the optical axis during focusing (Step ST3). Then, each lens is arranged within the lens barrel so as to satisfy at least the above-mentioned conditional expression (1) (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system that is compact yet has good optical performance.

[0072] Next, a manufacturing method for the variable magnification optical system ZL according to the second embodiment will be outlined. The manufacturing method for the variable magnification optical system ZL according to the second embodiment is similar to that described in the first embodiment, and will be described with reference to FIG. 14, as in the first embodiment. First, a first lens group G1 having negative refractive power and a rear group GR having at least one lens group are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is established in which the spacing between adjacent lens groups changes during magnification (Step ST2). Next, at least a portion of at least one lens group in the rear group GR is configured as a focusing group GF having negative refractive power that moves along the optical axis during focusing (Step ST3). Then, the lenses are arranged within the lens barrel so as to satisfy at least conditional expression (2) above (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system that is compact yet has excellent optical performance.

[0073] Next, a manufacturing method for the variable magnification optical system ZL according to the third embodiment will be outlined. The manufacturing method for the variable magnification optical system ZL according to the third embodiment is similar to that described in the first embodiment, and will be described with reference to FIG. 14, as in the first embodiment. First, a first lens group G1 having negative refractive power and a rear group GR having at least one lens group are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is established in which the spacing between adjacent lens groups changes during magnification (Step ST2). Next, at least a portion of at least one lens group in the rear group GR is configured as a focusing group GF having negative refractive power that moves along the optical axis during focusing (Step ST3). Then, the lenses are arranged within the lens barrel so as to satisfy at least conditional expression (3) above (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system that is compact yet has excellent optical performance.

[0074] Next, a manufacturing method for the variable magnification optical system ZL according to the fourth embodiment will be outlined. The manufacturing method for the variable magnification optical system ZL according to the fourth embodiment is similar to that described in the first embodiment, and will be described with reference to FIG. 14, as in the first embodiment. First, a first lens group G1 having negative refractive power and a rear group GR having at least one lens group are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is established in which the spacing between adjacent lens groups changes during magnification (Step ST2). Next, at least a portion of at least one lens group in the rear group GR is configured as a focusing group GF having negative refractive power that moves along the optical axis during focusing (Step ST3). Finally, each lens is arranged within the lens barrel so as to satisfy at least conditional expression (4) above (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system that is compact yet has excellent optical performance. [Example]

[0075] Variable magnification optical systems ZL according to examples of each embodiment will be described below with reference to the drawings. FIGS. 1, 3, 5, 7, 9, and 11 are cross-sectional views showing the configuration and refractive power distribution of variable magnification optical systems ZL {ZL(1) to ZL(6)} according to Examples 1 to 6. In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(6) according to Examples 1 to 6, the direction of movement of the focusing group along the optical axis when focusing from infinity to a close-distance object is indicated by an arrow along with the word "focusing." In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(6) according to Examples 1 to 6, the direction of movement of each lens group along the optical axis when changing magnification from the wide-angle end state (W) to the telephoto end state (T) is indicated by an arrow.

[0076] 1, 3, 5, 7, 9, and 11, each lens group is represented by a combination of the symbol G and a number, and each lens is represented by a combination of the symbol L and a number. In this case, to prevent the symbols and numbers from becoming too numerous and complicated, each example uses its own independent combination of symbols and numbers to represent the lens group, etc. Therefore, even if the same combination of symbols and numbers is used between examples, this does not mean that the examples have the same configuration.

[0077] Tables 1 to 6 are shown below, with Table 1 showing data on the various specifications for Example 1, Table 2 for Example 2, Table 3 for Example 3, Table 4 for Example 4, Table 5 for Example 5, and Table 6 for Example 6. In each example, the d-line (wavelength λ=587.6 nm) and g-line (wavelength λ=435.8 nm) were selected as the targets for calculating aberration characteristics.

[0078] In the [Overall Specifications] table, f is the focal length of the entire lens system, FNO is the F-number, ω is the half angle of view (unit: °), and Y is the image height. TL is the distance on the optical axis from the lens surface closest to the object in the variable magnification optical system to the lens surface closest to the image when focused at infinity, plus Bf (back focus), and Bf is the distance on the optical axis from the lens surface closest to the image in the variable magnification optical system to the image plane when focused at infinity (air equivalent distance). Note that these values ​​are shown for both the wide-angle end (W) and the telephoto end (T) of the variable magnification state.

[0079] In the table of overall specifications, fF indicates the focal length of the focusing group. fRw indicates the focal length of the rear group in the maximum wide-angle state. fRt indicates the focal length of the rear group in the maximum telephoto state. fFRw indicates the focal length of the lens group (image-side lens group) composed of lenses located closer to the image than the focusing group in the maximum wide-angle state. fFRt indicates the focal length of the lens group (image-side lens group) composed of lenses located closer to the image than the focusing group in the maximum telephoto state. fRPF indicates the focal length of the lens group with positive refractive power that is closest to the object among at least one lens group in the rear group. fRPR indicates the focal length of the lens group with positive refractive power that is closest to the image among at least one lens group in the rear group. βRw indicates the lateral magnification of the rear group in the maximum wide-angle state. βRt indicates the lateral magnification of the rear group in the maximum telephoto state.

[0080] In the [Lens Specifications] table, the surface number indicates the order of the optical surface from the object side along the direction of light ray travel, R is the radius of curvature of each optical surface (surfaces whose center of curvature is on the image side have a positive value), D is the surface spacing, which is the distance on the optical axis from each optical surface to the next optical surface (or image plane), nd is the refractive index of the optical element material with respect to the d-line, and νd is the Abbe number of the optical element material with respect to the d-line. The "∞" next to the radius of curvature indicates a flat surface or an aperture, and (stop S) indicates the aperture stop S. The refractive index of air, nd = 1.00000, is omitted. If the optical surface is aspherical, an * is added to the surface number, and the paraxial radius of curvature is shown in the "radius of curvature R" column.

[0081] In the [Aspherical Data] table, the shape of the aspherical surface shown in [Lens Specifications] is shown by the following formula (A). X(y) is the distance (amount of sag) along the optical axis from the tangent plane at the vertex of the aspherical surface to the position on the aspherical surface at height y, R is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and Ai is the ith aspherical coefficient. "En" is the square root of the square root of the aspherical surface. -n For example, 1.234E-05 = 1.234 x 10 -5 The second-order aspherical coefficient A2 is 0, and is therefore omitted.

[0082] 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 …(A)

[0083] The [Variable Distance Data] table shows the surface spacing for surface number i, which has a surface spacing of (Di) in the [Lens Specifications] table. The [Variable Distance Data] table also shows the surface spacing when focused at infinity and when focused at close range.

[0084] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0085] In the following, for all specifications, the focal length f, radius of curvature R, surface spacing D, and other lengths are generally expressed in "mm" unless otherwise specified, but this is not limited to this, as the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0086] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0087] (First Example) The first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. 1 shows the lens configuration of a variable magnification optical system according to the first embodiment. The variable magnification optical system ZL(1) according to the first embodiment is composed of, arranged along the optical axis from the object side, a first lens group G1 having negative refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves along the optical axis toward the image side and then toward the object side, while the second lens group G2 and the third lens group G3 move along the optical axis toward the object side, changing the spacing between adjacent lens groups. During magnification variation, the aperture stop S moves along the optical axis together with the second lens group G2, while the position of the fourth lens group G4 is fixed relative to the image plane I. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of the lens group, and this also applies to all the following examples.

[0088] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a plano-convex positive lens L11 with its plane facing the object side and a biconcave negative lens L12, and a biconcave negative lens L13.

[0089] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L21 with a convex surface facing the object side, a biconvex positive lens L22, a cemented lens consisting of a positive meniscus lens L23 with a concave surface facing the object side and a negative meniscus lens L24 with a concave surface facing the object side, a positive meniscus lens L25 with a concave surface facing the object side, and a negative meniscus lens L26 with a concave surface facing the object side. The positive meniscus lens L21 has aspheric lens surfaces on both sides. The positive meniscus lens L25 has aspheric lens surfaces on both sides. The negative meniscus lens L26 has an aspheric lens surface on the image side.

[0090] The third lens group G3 is composed of a positive meniscus lens L31 with its concave surface facing the object side. The fourth lens group G4 is composed of a positive meniscus lens L41 with its concave surface facing the object side. The lens surface of the positive meniscus lens L41 facing the image side is aspheric. An image surface I is located on the image side of the fourth lens group G4. A parallel plate PP is located between the fourth lens group G4 and the image surface I.

[0091] In this embodiment, the second lens group G2, the third lens group G3, and the fourth lens group G4 constitute a rear group GR having positive refractive power overall. The fourth lens group G4 corresponds to the final lens group GE, which is located closest to the image side of the rear group GR. The positive meniscus lens L25 and the negative meniscus lens L26 of the second lens group G2 constitute a focusing group GF that moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing group GF (the positive meniscus lens L25 and the negative meniscus lens L26 of the second lens group G2) moves toward the image side along the optical axis. The third lens group G3 (positive meniscus lens L31) and the fourth lens group G4 (positive meniscus lens L41) constitute an image-side lens group GFR, which is composed of lenses located closer to the image side than the focusing group GF.

[0092] Table 1 below lists the values ​​of the specifications of the variable magnification optical system according to the first example.

[0093] (Table 1) [Overall specifications] Magnification ratio=1.686 fF=-13.469 fRw=22.428 fRt=27.572 fFRw=27.573 fFRt=30.766 fRPF=19.536 fRPR=62.124 βRw=-0.665 βRt=-1.121 WMT f 28.745 40.000 48.481 FNO 4.635 5.749 6.489 ω 37.870 27.025 21.831 Y 19.939 21.700 21.700 TL 55.075 53.822 55.075 Bf 10.305 10.305 10.305 [Lens specifications] Surface number RD nd νd 1 ∞ 1.99620 1.922859 20.88 2 -61.67336 0.87789 1.593190 67.90 3 94.82844 1.52115 4 -37.67366 0.87153 1.799520 42.09 5 775.23425 (D5) 6 ∞ 1.00000 (Aperture S) 7* 6.74413 2.55372 1.497103 81.56 8* 15.34883 1.61262 9 25.17654 2.66678 1.593190 67.90 10 -9.58280 0.30884 11 -12.09204 1.97615 1.497820 82.57 12 -6.39708 0.80000 1.801000 34.92 13 -41.47880 (D13) 14* -15.65263 1.08809 1.693500 53.20 15* -13.65939 4.06569 16 -6.58010 1.00000 1.593190 67.90 17* -81.14295 (D17) 18 -230.52245 2.89238 1.922859 20.88 19 -36.62793 (D19) 20 -40.68082 2.24629 1.768015 49.24 21* -22.48518 8.25000 22 ∞ 1.60000 1.516800 63.88 23 ∞ 1.00000 [Aspherical surface] Page 7 κ=1.0000,A4=1.88915E-04,A6=4.93302E-06,A8=3.01855E-07,A10=0.00000E+00 Page 8 κ=1.0000,A4=7.66909E-04,A6=1.32765E-05,A8=9.83562E-07,A10=0.00000E+00 Page 14 κ=1.0000,A4=9.45995E-04,A6=1.82284E-05,A8=-1.90524E-07,A10=0.00000E+00 Page 15 κ=1.0000,A4=8.64798E-04,A6=1.59927E-05,A8=5.50227E-08,A10=0.00000E+00 Page 17 κ=1.0000,A4=-1.24954E-04,A6=8.78929E-07,A8=-7.97530E-09,A10=0.00000E+00 Page 21 κ=1.0000,A4=3.11712E-05,A6=1.30785E-08,A8=3.17570E-11,A10=0.00000E+00 [Can change the interval データ] Infinity focus state WMT Focus distance 28.745 40.000 48.481 Object distance ∞ ∞ ∞ D5 12.279 4.849 1.513 D13 1.029 1.029 1.029 D17 2.985 2.943 2.795 D19 1.000 7.219 11.955 Close focus WMT Magnification -0.113 -0.164 -0.206 Object distance 244.380 245.633 244.380 D5 12.279 4.849 1.513 D13 2.335 2.925 3.381 D17 1.679 1.046 0.443 D19 1.000 7.219 11.955 [Lens group data] Group starting plane focal length G1 1 -43.251 G2 7 19.536 G3 18 46.852 G4 20 62.124

[0094] FIG. 2(A) shows various aberration diagrams of the variable magnification optical system of Example 1 when focused at infinity in the wide-angle end state. FIG. 2(B) shows various aberration diagrams of the variable magnification optical system of Example 1 when focused at infinity in the telephoto end state. In each aberration diagram, FNO indicates the F-number, and Y indicates the image height. Note that the spherical aberration diagram indicates the F-number value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram indicate the maximum image height, and the coma diagram indicates the value of each image height. d indicates the d-line (wavelength λ=587.6 nm), and g indicates the g-line (wavelength λ=435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. Note that the same symbols as in this example are used in the aberration diagrams of each example shown below, and redundant explanations will be omitted.

[0095] From the various aberration diagrams, it can be seen that the variable magnification optical system according to Example 1 has excellent correction of various aberrations from the wide-angle end state to the telephoto end state, and has excellent imaging performance.

[0096] (Second Example) The second example will be described with reference to FIGS. 3 and 4 and Table 2. FIG. 3 shows the lens configuration of the variable magnification optical system of the second example. The variable magnification optical system ZL(2) of the second example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves along the optical axis toward the image side and then toward the object side, while the second lens group G2 and the third lens group G3 move along the optical axis toward the object side, changing the spacing between adjacent lens groups. During magnification variation, the aperture stop S moves along the optical axis together with the second lens group G2, while the position of the fourth lens group G4 is fixed relative to the image plane I.

[0097] In the second embodiment, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 are configured in the same manner as in the first embodiment, and therefore the same reference numerals are used, and detailed descriptions of these lenses will be omitted. In this embodiment, the second lens group G2, the third lens group G3, and the fourth lens group G4 together form the rear group GR, which has positive refractive power as a whole. The fourth lens group G4 corresponds to the final lens group GE, which is located closest to the image side of the rear group GR. The positive meniscus lens L25 and the negative meniscus lens L26 of the second lens group G2 form the focusing group GF, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing group GF (the positive meniscus lens L25 and the negative meniscus lens L26 of the second lens group G2) moves toward the image side along the optical axis. The third lens group G3 (positive meniscus lens L31) and the fourth lens group G4 (positive meniscus lens L41) form an image-side lens group GFR made up of lenses arranged closer to the image side than the focusing group GF.

[0098] Table 2 below lists the values ​​of the specifications of the variable magnification optical system according to the second example.

[0099] (Table 2) [Overall specifications] Magnification ratio=1.687 fF=-13.491 fRw=22.454 fRt=27.757 fFRw=27.409 fFRt=30.589 fRPF=15.676 fRPR=61.423 βRw=-0.662 βRt=-1.116 WMT f 28.745 40.001 48.482 FNO 4.635 5.736 6.489 ω 37.866 27.032 21.801 Y 19.928 21.700 21.700 TL 55.064 53.621 55.064 Bf 10.305 10.485 10.305 [Lens specifications] Surface number RD nd νd 1 ∞ 1.99725 1.922859 20.88 2 -61.58859 0.87546 1.593190 67.90 3 100.28735 1.49398 4 -37.97558 0.87137 1.799520 42.09 5 550.89033 (D5) 6 ∞ 1.00000 (Aperture S) 7* 6.73949 2.54345 1.497103 81.56 8* 15.13316 1.62404 9 24.63480 2.67430 1.593190 67.90 10 -9.61747 0.31183 11 -12.16080 1.97765 1.497820 82.57 12 -6.40689 0.80000 1.801000 34.92 13 -42.72321 (D13) 14* -15.59490 1.08938 1.693500 53.20 15* -13.62652 4.08182 16 -6.58583 1.00037 1.593190 67.90 17* -80.21449 (D17) 18 -218.94268 2.88641 1.922859 20.88 19 -36.26331 (D19) 20 -40.30806 2.26539 1.768015 49.24 21* -22.26647 8.25000 22 ∞ 1.60000 1.516800 63.88 23 ∞ 1.00000 [Aspherical surface] Page 7 κ=1.0000,A4=1.92075E-04,A6=4.79807E-06,A8=3.11755E-07,A10=0.00000E+00 Page 8 κ=1.0000,A4=7.70170E-04,A6=1.30465E-05,A8=1.00763E-06,A10=0.00000E+00 Page 14 κ=1.0000,A4=9.21586E-04,A6=1.86210E-05,A8=-1.96584E-07,A10=0.00000E+00 Page 15 κ=1.0000,A4=8.40862E-04,A6=1.62428E-05,A8=4.53775E-08,A10=0.00000E+00 Page 17 κ=1.0000,A4=-1.23223E-04,A6=8.46946E-07,A8=-7.60366E-09,A10=0.00000E+00 Page 21 κ=1.0000,A4=3.16515E-05,A6=1.26787E-08,A8=3.70654E-11,A10=0.00000E+00 [Can change the interval データ] Infinity focus state WMT Focal length 28.745 40.001 48.482 Object distance ∞ ∞ ∞ D5 12.308 4.752 1.518 D13 1.041 1.041 1.041 D17 2.917 2.726 2.818 D19 1.000 7.125 11.889 Close focus state WMT Magnification -0.113 -0.164 -0.206 Object distance 244.391 245.833 244.391 D5 12.308 4.752 1.518 D13 2.359 2.966 3.415 D17 1.599 0.801 0.444 D19 1.000 7.125 11.889 [Lens group data] Group starting plane focal length G1 1 -43.446 G2 7 19.566 G3 18 46.740 G4 20 61.423

[0100] Fig. 4(A) is a diagram showing various aberrations when the variable magnification optical system according to Example 2 is focused at infinity in the wide-angle end state. Fig. 4(B) is a diagram showing various aberrations when the variable magnification optical system according to Example 2 is focused at infinity in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 2 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0101] (Third Example) Example 3 will be described with reference to FIGS. 5 and 6 and Table 3. FIG. 5 shows the lens configuration of a variable magnification optical system according to Example 3. The variable magnification optical system ZL(3) according to Example 3 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, an aperture stop S, 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 positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves along the optical axis toward the image side and then toward the object side, while the second lens group G2, the third lens group G3, and the fourth lens group G4 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. Furthermore, when the magnification is changed, the aperture stop S moves along the optical axis together with the second lens group G2, and the position of the fifth lens group G5 relative to the image plane I is fixed.

[0102] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a plano-convex positive lens L11 with its plane facing the object side and a biconcave negative lens L12, and a biconcave negative lens L13.

[0103] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L21 with a convex surface facing the object side, a biconvex positive lens L22, and a cemented lens made up of a positive meniscus lens L23 with a concave surface facing the object side and a negative meniscus lens L24 with a concave surface facing the object side. Both lens surfaces of the positive meniscus lens L21 are aspherical.

[0104] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L31 with its concave surface facing the object side and a negative meniscus lens L32 with its concave surface facing the object side. The positive meniscus lens L31 has aspheric lens surfaces on both sides. The negative meniscus lens L32 has an aspheric lens surface facing the image side.

[0105] The fourth lens group G4 is composed of a positive meniscus lens L41 with its concave surface facing the object side. The fifth lens group G5 is composed of a positive meniscus lens L51 with its concave surface facing the object side. The positive meniscus lens L51 has an aspherical lens surface facing the image side. An image surface I is located on the image side of the fifth lens group G5. In addition, a parallel plate PP is located between the fifth lens group G5 and the image surface I.

[0106] In this embodiment, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GR, which has a positive refractive power as a whole. The fifth lens group G5 corresponds to the final lens group GE, which is arranged closest to the image side of the rear group GR. The entire third lens group G3 constitutes the focusing group GF, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing group GF (the entire third lens group G3) moves toward the image side along the optical axis. The fourth lens group G4 (positive meniscus lens L41) and the fifth lens group G5 (positive meniscus lens L51) constitute an image-side lens group GFR, which is made up of lenses arranged closer to the image side than the focusing group GF.

[0107] Table 3 below lists the values ​​of the specifications of the variable magnification optical system according to the third example.

[0108] (Table 3) [Overall specifications] Magnification ratio=1.686 fF=-13.427 fRw=22.402 fRt=27.702 fFRw=27.256 fFRt=30.400 fRPF=15.664 fRPR=60.598 βRw=-0.666 βRt=-1.123 WMT f 28.754 40.001 48.489 FNO 4.635 5.731 6.489 ω 37.861 26.969 21.751 Y 19.930 21.700 21.700 TL 55.048 53.459 55.048 Bf 10.305 10.305 10.305 [Lens specifications] Surface number RD nd νd 1 ∞ 2.00818 1.922859 20.88 2 -61.03131 0.87438 1.593190 67.90 3 101.77694 1.48276 4 -38.23636 0.87484 1.799520 42.09 5 424.54741 (D5) 6 ∞ 1.00000 (Aperture S) 7* 6.75681 2.55201 1.497103 81.56 8* 15.38664 1.63500 9 25.27764 2.65716 1.593190 67.90 10 -9.63773 0.31417 11 -12.22612 1.96902 1.497820 82.57 12 -6.43133 0.80000 1.801000 34.92 13 -42.16168 (D13) 14* -15.65543 1.08329 1.693500 53.20 15* -13.76558 4.17510 16 -6.61113 1.00000 1.593190 67.90 17* -83.29031 (D17) 18 -259.59884 2.89709 1.922859 20.88 19 -37.19930 (D19) 20 -41.30813 2.25294 1.768015 49.24 21* -22.40267 8.25000 22 ∞ 1.60000 1.516800 63.88 23∞1.00000 [Aspherical surface] Page 7 κ=1.0000,A4=1.92524E-04,A6=4.65523E-06,A8=3.21615E-07,A10=0.00000E+00 Page 8 κ=1.0000,A4=7.70473E-04,A6=1.27785E-05,A8=1.01681E-06,A10=0.00000E+00 Page 14 κ=1.0000,A4=9.42593E-04,A6=1.73477E-05,A8=-1.86967E-07,A10=0.00000E+00 Page 15 κ=1.0000,A4=8.62927E-04,A6=1.54043E-05,A8=3.94933E-08,A10=0.00000E+00 Page 17 κ=1.0000,A4=-1.27386E-04,A6=8.72918E-07,A8=-7.68623E-09,A10=0.00000E+00 Page 21 κ=1.0000,A4=3.23926E-05,A6=1.22601E-08,A8=3.65636E-11,A10=0.00000E+00 [Can change the interval データ] Infinity focus state WMT Focus distance 28.754 40.001 48.489 Object distance ∞ ∞ ∞ D5 12.261 4.701 1.524 D13 1.009 1.111 1.069 D17 2.898 2.781 2.821 D19 1.000 6.986 11.754 Close focus WMT Magnification -0.114 -0.164 -0.206 Object distance 244.407 245.996 244.407 D5 12.261 4.701 1.524 D13 2.325 3.046 3.447 D17 1.582 0.846 0.443 D19 1.000 6.986 11.754 [Lens group data] Group starting plane focal length G1 1 -43.162 G2 7 15.664 G3 14 -13.427 G4 18 46.759 G5 20 60.598

[0109] Fig. 6(A) is a diagram showing various aberrations when the variable magnification optical system according to Example 3 is focused at infinity in the wide-angle end state. Fig. 6(B) is a diagram showing various aberrations when the variable magnification optical system according to Example 3 is focused at infinity in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 3 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0110] (Fourth Example) Example 4 will be described with reference to FIGS. 7 to 8 and Table 4. FIG. 7 shows the lens configuration of a variable magnification optical system according to Example 4. Example 4's variable magnification optical system ZL(4) is composed of, arranged along the optical axis from the object side, a first lens group G1 having negative refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves along the optical axis toward the image side and then toward the object side, while the second lens group G2 and the third lens group G3 move along the optical axis toward the object side, changing the spacing between adjacent lens groups. Furthermore, when varying magnification, the aperture stop S moves along the optical axis together with the second lens group G2, while the position of the fourth lens group G4 is fixed relative to the image plane I.

[0111] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a positive meniscus lens L11 with its concave surface facing the object side and a biconcave negative lens L12, and a negative meniscus lens L13 with its concave surface facing the object side.

[0112] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L21, a negative meniscus lens L22 with its convex surface facing the object side, and a positive meniscus lens L23 with its convex surface facing the object side. Both lens surfaces of the positive lens L21 are aspherical. Both lens surfaces of the positive meniscus lens L23 are aspherical.

[0113] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L31 with a convex surface facing the object side and a negative meniscus lens L32 with a concave surface facing the object side. The negative meniscus lens L31 has an aspherical lens surface facing the image side. The negative meniscus lens L32 has aspherical lens surfaces on both sides.

[0114] The fourth lens group G4 is composed of a positive meniscus lens L41 with its concave surface facing the object side. The lens surface of the positive meniscus lens L41 facing the image side is aspheric. An image plane I is located on the image side of the fourth lens group G4. A parallel plate PP is located between the fourth lens group G4 and the image plane I.

[0115] In this embodiment, the second lens group G2, the third lens group G3, and the fourth lens group G4 constitute the rear group GR, which has positive refractive power as a whole. The fourth lens group G4 corresponds to the final lens group GE, which is arranged closest to the image side of the rear group GR. The entire third lens group G3 constitutes the focusing group GF, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing group GF (the entire third lens group G3) moves toward the image side along the optical axis. The fourth lens group G4 (positive meniscus lens L41) constitutes the image-side lens group GFR, which is made up of lenses arranged closer to the image side than the focusing group GF.

[0116] Table 4 below lists the values ​​of the specifications of the variable magnification optical system according to the fourth example.

[0117] (Table 4) [Overall specifications] Magnification ratio=1.687 fF=-23.773 fRw=23.002 fRt=30.777 fFRw=50.145 fFRt=50.145 fRPF=17.295 fRPR=50.145 βRw=-0.628 βRt=-1.059 WMT f 28.744 40.000 48.486 FNO 4.635 5.719 6.489 ω 37.740 28.080 23.384 Y 19.814 21.700 21.700 TL 53.764 52.719 53.764 Bf 17.555 17.915 17.555 [Lens specifications] Surface number RD nd νd 1 -74.97806 1.57056 1.922859 20.88 2 -43.63293 0.88324 1.593190 67.90 3 225.85772 1.21996 4 -40.81390 0.88014 1.593190 67.90 5 -1801.45150 (D5) 6 ∞ 1.00000 (Aperture S) 7* 7.78171 3.28821 1.497103 81.56 8* -39.66691 0.10000 9 9.42082 0.80000 1.902000 25.26 10 6.67111 1.59048 11* 29.89210 1.17255 1.592014 67.02 12* 64.12762 (D12) 13 14.07861 0.75819 1.497103 81.56 14* 11.49932 7.98047 15* -10.97492 0.99994 1.497103 81.56 16* -43.99636 (D16) 17 -41.88288 5.52332 1.882023 37.22 18* -22.84142 8.25000 19 ∞ 1.60000 1.516800 63.88 20 ∞ 1.00000 [Aspherical surface] Page 7 κ=1.0000,A4=-6.94600E-05,A6=3.33392E-06,A8=-6.22219E-08,A10=0.00000E+00 Page 8 κ=1.0000,A4=7.91449E-04,A6=-9.22475E-06,A8=-2.04863E-08,A10=0.00000E+00 Page 11 κ=1.0000,A4=2.22039E-03,A6=-1.38926E-05,A8=0.00000E+00,A10=0.00000E+00 Page 12 κ=1.0000,A4=1.75015E-03,A6=6.88355E-06,A8=0.00000E+00,A10=0.00000E+00 Page 14 κ=1.0000,A4=-6.73272E-05,A6=3.02052E-07,A8=0.00000E+00,A10=0.00000E+00 Page 15 κ=1.0000,A4=-9.05362E-05,A6=-5.77549E-07,A8=-2.18840E-08,A10=0.00000E+00 Page 16 κ=1.0000,A4=-5.42555E-05,A6=-4.40579E-07,A8=4.88714E-10,A10=0.00000E+00 Side 18 κ=1.0000,A4=9.49522E-06,A6=-1.26832E-08,A8=4.82544E-11,A10=0.00000E+00 [Variable Interval Data] Infinity focus WMT Focal length 28.744 40.000 48.486 Object distance ∞ ∞ ∞ D5 12.155 4.837 1.500 D12 0.831 0.500 0.500 D16 2.707 8.951 13.692 Close focus state WMT Magnification -0.112 -0.161 -0.200 Object distance 245.691 246.736 245.691 D5 12.155 4.837 1.500 D12 3.014 3.465 4.074 D16 0.523 5.986 10.118 [Lens group data] Group starting plane focal length G1 1 -45.779 G2 7 17.295 G3 13 -23.773 G4 17 50.145

[0118] Fig. 8(A) is a diagram showing various aberrations when the variable magnification optical system according to Example 4 is focused at infinity in the wide-angle end state. Fig. 8(B) is a diagram showing various aberrations when the variable magnification optical system according to Example 4 is focused at infinity in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 4 has excellent correction of various aberrations from the wide-angle end state to the telephoto end state, and has excellent imaging performance.

[0119] (Fifth Example) Example 5 will be described with reference to FIGS. 9 and 10 and Table 5. FIG. 9 shows the lens configuration of a variable magnification optical system according to Example 5. The variable magnification optical system ZL(5) according to Example 5 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, an aperture stop S, 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 positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves along the optical axis toward the image side and then toward the object side, the second lens group G2 and the third lens group G3 move along the optical axis toward the object side, and the fourth lens group G4 moves along the optical axis toward the object side and then toward the image side, changing the spacing between adjacent lens groups. Furthermore, when the magnification is changed, the aperture stop S moves along the optical axis together with the second lens group G2, and the position of the fifth lens group G5 relative to the image plane I is fixed.

[0120] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a positive meniscus lens L11 with its concave surface facing the object side and a biconcave negative lens L12, and a negative meniscus lens L13 with its concave surface facing the object side.

[0121] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L21, a negative meniscus lens L22 with its convex surface facing the object side, and a positive meniscus lens L23 with its convex surface facing the object side. Both lens surfaces of the positive lens L21 are aspherical. Both lens surfaces of the positive meniscus lens L23 are aspherical.

[0122] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L31 and a negative meniscus lens L32 with its concave surface facing the object side. The positive lens L31 has an aspherical lens surface facing the image side. The negative meniscus lens L32 has aspherical lens surfaces on both sides.

[0123] The fourth lens group G4 is composed of a positive meniscus lens L41 with its concave surface facing the object side. The positive meniscus lens L41 has an aspherical lens surface facing the image side.

[0124] The fifth lens group G5 is composed of a positive meniscus lens L51 with its concave surface facing the object side. An image plane I is located on the image side of the fifth lens group G5. A parallel plate PP is located between the fifth lens group G5 and the image plane I.

[0125] In this embodiment, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GR, which has a positive refractive power as a whole. The fifth lens group G5 corresponds to the final lens group GE, which is arranged closest to the image side of the rear group GR. The entire third lens group G3 constitutes the focusing group GF, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing group GF (the entire third lens group G3) moves toward the image side along the optical axis. The fourth lens group G4 (positive meniscus lens L41) and the fifth lens group G5 (positive meniscus lens L51) constitute an image-side lens group GFR, which is made up of lenses arranged closer to the image side than the focusing group GF.

[0126] Table 5 below lists the values ​​of the specifications of the variable magnification optical system according to the fifth example.

[0127] (Table 5) [Overall specifications] Magnification ratio=1.687 fF=-23.557 fRw=22.006 fRt=27.853 fFRw=56.322 fFRt=56.322 fRPF=16.507 fRPR=72.338 βRw=-0.711 βRt=-1.200 WMT f 28.736 39.996 48.484 FNO 4.635 5.707 6.489 ω 37.834 27.338 22.307 Y 19.873 21.700 21.700 TL 53.158 52.117 53.446 Bf 10.305 10.499 10.305 [Lens specifications] Surface number RD nd νd 1 -78.94193 1.72137 1.922859 20.88 2 -40.22624 0.88791 1.593190 67.90 3 214.46025 1.47635 4 -31.48425 0.88376 1.593190 67.90 5 -877.76237 (D5) 6 ∞ 1.00001 (Aperture S) 7* 7.88532 3.27835 1.497103 81.56 8* -34.39026 0.23036 9 11.14049 0.80000 1.902000 25.26 10 7.58072 1.30775 11* 28.25287 1.21737 1.592014 67.02 12* 78.20653 (D12) 13 454.51671 1.22144 1.497103 81.56 14* -170.72900 6.54398 15* -7.99852 0.99989 1.693500 53.20 16* -18.66958 (D16) 17 -21.11056 2.02301 1.592014 67.02 18* -19.25768 (D18) 19 -27.35915 3.73536 1.922859 20.88 20 -20.67766 8.25000 21 ∞ 1.60000 1.516800 63.88 22∞1.00000 [Aspherical surface] Page 7 κ=1.0000,A4=-6.17249E-05,A6=3.64790E-06,A8=-9.46230E-08,A10=0.00000E+00 Page 8 κ=1.0000,A4=9.09449E-04,A6=-1.31033E-05,A8=-3.57776E-08,A10=0.00000E+00 Page 11 κ=1.0000,A4=2.30528E-03,A6=-1.53067E-05,A8=0.00000E+00,A10=0.00000E+00 Page 12 κ=1.0000,A4=1.76391E-03,A6=1.29596E-05,A8=0.00000E+00,A10=0.00000E+00 Page 14 κ=1.0000,A4=-1.34128E-04,A6=-2.58817E-06,A8=0.00000E+00,A10=0.00000E+00 Page 15 κ=1.0000,A4=5.19818E-05,A6=-2.82181E-06,A8=-3.64480E-08,A10=0.00000E+00 Page 16 κ=1.0000,A4=4.75476E-05,A6=-2.23750E-06,A8=1.49381E-08,A10=0.00000E+00 Page 18 κ=1.0000,A4=4.49129E-05,A6=-1.00014E-08,A8=1.38726E-10,A10=0.00000E+00 [Can change the interval データ] Infinity focus state WMT Focus distance 28.736 39.996 48.484 Object distance ∞ ∞ ∞ D5 11.148 4.372 1.500 D12 0.803 0.799 0.799 D16 3.074 7.916 13.015 D18 0.500 1.205 0.500 Close focus state WMT Magnification -0.112 -0.160 -0.198 Object distance 246.297 247.338 246.009 D5 11.148 4.372 1.500 D12 2.887 3.704 4.271 D16 0.990 5.010 9.543 D18 0.500 1.205 0.500 [Lens group data] Group starting plane focal length G1 1 -40.394 G2 7 16.507 G3 13 -23.557 G4 17 263.594 G5 19 72.338

[0128] Fig. 10(A) is a diagram showing various aberrations when the variable magnification optical system according to Example 5 is focused at infinity in the wide-angle end state. Fig. 10(B) is a diagram showing various aberrations when the variable magnification optical system according to Example 5 is focused at infinity in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 5 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0129] (Sixth Example) Example 6 will be described with reference to FIGS. 11 and 12 and Table 6. FIG. 11 shows the lens configuration of a variable magnification optical system according to Example 6. The variable magnification optical system ZL(6) according to Example 6 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having negative refractive power, an aperture stop S, 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 positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves along the optical axis toward the image side and then toward the object side, while the second lens group G2, the third lens group G3, and the fourth lens group G4 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. Furthermore, when the magnification is changed, the aperture stop S moves along the optical axis together with the second lens group G2, and the position of the fifth lens group G5 relative to the image plane I is fixed.

[0130] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented lens of a plano-convex positive lens L11 with its plane facing the object side and a biconcave negative lens L12, and a biconcave negative lens L13.

[0131] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L21, a biconcave negative lens L22, a positive meniscus lens L23 with its concave surface facing the object side, and a negative meniscus lens L24 with its concave surface facing the object side. Both lens surfaces of the positive lens L21 are aspherical. Both lens surfaces of the negative lens L22 are aspherical. Both lens surfaces of the negative meniscus lens L24 are aspherical.

[0132] The third lens group G3 is composed of a negative meniscus lens L31 with its concave surface facing the object side, and both lens surfaces of the negative meniscus lens L31 are aspherical.

[0133] The fourth lens group G4 is composed of a positive meniscus lens L41 with its concave surface facing the object side. The fifth lens group G5 is composed of a positive meniscus lens L51 with its concave surface facing the object side. The positive meniscus lens L51 has an aspherical lens surface facing the image side. An image surface I is located on the image side of the fifth lens group G5. In addition, a parallel plate PP is located between the fifth lens group G5 and the image surface I.

[0134] In this embodiment, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GR, which has a positive refractive power as a whole. The fifth lens group G5 corresponds to the final lens group GE, which is arranged closest to the image side of the rear group GR. The entire third lens group G3 constitutes the focusing group GF, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing group GF (the entire third lens group G3) moves toward the image side along the optical axis. The fourth lens group G4 (positive meniscus lens L41) and the fifth lens group G5 (positive meniscus lens L51) constitute an image-side lens group GFR, which is made up of lenses arranged closer to the image side than the focusing group GF.

[0135] Table 6 below lists the values ​​of the specifications of the variable magnification optical system according to the sixth example.

[0136] (Table 6) [Overall specifications] Magnification ratio=1.688 fF=-17.191 fRw=22.576 fRt=28.450 fFRw=31.580 fFRt=34.233 fRPF=17.401 fRPR=62.135 βRw=-0.663 βRt=-1.119 WMT f 28.734 40.000 48.492 FNO 4.635 5.755 6.489 ω 38.247 27.621 22.588 Y 19.934 21.700 21.700 TL 55.196 53.860 55.196 Bf 10.305 10.330 10.305 [Lens specifications] Surface number RD nd νd 1 ∞ 1.62184 1.922859 20.88 2 -98.98277 0.89162 1.593190 67.90 3 77.82625 1.79570 4 -33.56157 0.89112 1.593190 67.90 5 589.10769 (D5) 6 ∞ 1.00000 (Aperture S) 7* 6.70273 3.12536 1.497103 81.56 8* -30.15078 0.57764 9* -55.84253 0.80000 1.635500 23.89 10* 44.80145 2.17402 11 -8.34724 1.43673 1.496997 81.61 12 -6.40691 0.22961 13* -4.92101 0.82001 1.497103 81.56 14* -7.35389 (D14) 15* -10.06431 1.00010 1.851348 40.10 16* -33.69524 (D16) 17 -2610.17570 2.58513 1.922859 20.88 18 -54.86830 (D18) 19 -71.71870 2.86404 1.768015 49.24 20* -29.15141 8.25000 21 ∞ 1.60000 1.516800 63.88 22∞1.00000 [Aspherical data] Side 7 κ=1.0000,A4=6.34976E-06,A6=1.73361E-06,A8=0.00000E+00,A10=0.00000E+00 Page 8 κ=1.0000,A4=4.68148E-04,A6=-8.06904E-06,A8=0.00000E+00,A10=0.00000E+00 Page 9 κ=1.0000,A4=1.27100E-03,A6=-2.18846E-05,A8=0.00000E+00,A10=0.00000E+00 Page 10 κ=1.0000,A4=1.33096E-03,A6=-1.45423E-06,A8=0.00000E+00,A10=0.00000E+00 Page 13 κ=1.0000,A4=2.30483E-03,A6=-1.88231E-05,A8=0.00000E+00,A10=0.00000E+00 Page 14 κ=1.0000,A4=2.04780E-03,A6=-2.37072E-05,A8=0.00000E+00,A10=0.00000E+00 Page 15 κ=1.0000,A4=1.26184E-04,A6=1.03823E-06,A8=1.21180E-08,A10=0.00000E+00 Page 16 κ=1.0000,A4=2.47523E-05,A6=2.27287E-07,A8=-9.41887E-10,A10=0.00000E+00 Page 20 κ=1.0000,A4=2.56873E-05,A6=-1.19279E-08,A8=0.00000E+00,A10=0.00000E+00 [Can change the interval データ] Infinity focus state WMT Focus distance 28.734 40.000 48.492 Object distance ∞ ∞ ∞ D5 12.551 4.940 1.517 D14 7.484 7.721 7.834 D16 2.261 3.253 3.690 D18 0.781 5.803 10.038 Close focus state WMT Magnification -0.113 -0.162 -0.203 Object distance 244.259 245.595 244.259 D5 12.551 4.940 1.517 D14 9.287 10.353 11.105 D16 0.458 0.621 0.419 D18 0.781 5.803 10.038 [Lens group data] Group starting plane focal length G1 1 -43.328 G2 7 17.401 G3 15 -17.191 G4 17 60.702 G5 19 62.135

[0137] Fig. 12(A) is a diagram showing various aberrations when the variable magnification optical system according to Example 6 is focused at infinity in the wide-angle end state. Fig. 12(B) is a diagram showing various aberrations when the variable magnification optical system according to Example 6 is focused at infinity in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 6 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0138] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below: This table shows the values ​​corresponding to each of the conditional expressions (1) to (12) for all the examples (Examples 1 to 6). Condition (1) 1.50 <ft / (-fF)<10.00 Condition (2) 0.70 <fw / (-fF)<7.00 Condition (3) 1.00 <fFRw / (-fF)<7.00 Condition (4) 1.00 <fFRt / (-fF)<7.00 Condition (5) 0.50 <fRw / (-fF)<4.00 Condition (6) 0.50 <fRt / (-fF)<5.00 Condition (7) 0.10 <fRPF / fRPR<0.60 Condition (8) 0.50 <fRPF / (-fF)<3.00 Condition (9) 0.05 <Bfw / fRPR<0.35 Conditional expression (10) 60.00°<2ωw<90.00° Conditional expression (11) 1.50<(-f1) / fRw<3.00 Conditional expression (12) 0.50<(-f1) / fRt<2.50

[0139] [Conditional Expression Corresponding Values] (First to Third Examples) Conditional Expression First Example Second Example Third Example (1) 3.600 3.594 3.611 (2) 2.134 2.131 2.142 (3) 2.047 2.032 2.030 (4) 2.284 2.267 2.264 (5) 1.665 1.664 1.668 (6) 2.047 2.057 2.063 (7) 0.314 0.255 0.258 (8) 1.450 1.162 1.167 (9) 0.166 0.168 0.170 (10) 75.740 75.733 75.722 (11) 1.928 1.935 1.927 (12) 1.569 1.565 1.558 [Conditional Expression Corresponding Values] (Fourth to Sixth Examples) Conditional Expression 4th Example 5th Example 6th Example (1) 2.040 2.058 2.821 (2) 1.209 1.220 1.671 (3) 2.109 2.391 1.837 (4) 2.109 2.391 1.991 (5) 0.968 0.934 1.313 (6) 1.295 1.182 1.655 (7) 0.345 0.228 0.280 (8) 0.728 0.701 1.012 (9) 0.206 0.142 0.166 (10) 75.480 75.669 76.494 (11) 1.990 1.836 1.919 (12) 1.487 1.450 1.523

[0140] According to each of the above embodiments, it is possible to realize a variable magnification optical system that is compact yet has good optical performance.

[0141] The above-described examples are merely illustrative examples of the present invention, and the present invention is not limited to these.

[0142] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the variable magnification optical system of this embodiment.

[0143] Although four-group and five-group configurations have been shown as examples of the variable magnification optical system of this embodiment, the present application is not limited to these, and variable magnification optical systems with other group configurations (for example, six groups, seven groups, etc.) can also be configured. Specifically, a lens or lens group may be added to the most object-side or most image-plane-side of the variable magnification optical system of this embodiment. Note that a lens group refers to a portion having at least one lens separated by an air gap that changes when the magnification is changed.

[0144] A single lens group, multiple lens groups, or a partial lens group may be moved in the optical axis direction to function as a focusing lens group that focuses from an object at infinity to a close object. The focusing lens group can also be used for autofocusing, and is suitable for driving a motor (using an ultrasonic motor, etc.) for autofocusing.

[0145] The lens group or partial lens group may be moved so as to have a component in a direction perpendicular to the optical axis, or may be rotated (oscillated) in a plane including the optical axis, to serve as an image stabilization lens group that corrects image blur caused by camera shake.

[0146] The lens surface may be spherical, flat, or aspherical. Spherical or flat lens surfaces are preferred because they facilitate lens processing and assembly adjustment, and prevent degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, they are preferred because they minimize degradation of imaging performance even when the image plane is misaligned.

[0147] If the lens surface is aspherical, the aspherical surface may be any of the following: a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, or a hybrid aspherical surface in which a resin is formed into an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, or the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0148] The aperture diaphragm is preferably disposed between the first lens group and the second 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.

[0149] Each lens surface may be coated with an anti-reflection coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high-contrast optical performance. [Explanation of symbols]

[0150] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G5 5th lens group I Image plane S Aperture stop

Claims

1. a first lens group having negative refractive power, arranged in order from the object side along the optical axis; a rear group having three lens groups, When changing magnification, the spacing between adjacent lens groups changes, at least a part of any of the at least three lens groups in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, A variable magnification optical system that satisfies the following condition: 1.00<fFRw / (-fF)<7.00 where fFRw is the focal length of the lens group configured with lenses arranged closer to the image side than the focusing group in the wide-angle end state. fF: focal length of the focusing group

2. a first lens group having negative refractive power, arranged in order from the object side along the optical axis; a rear group having three lens groups, When changing magnification, the spacing between adjacent lens groups changes, at least a part of any of the at least three lens groups in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, A variable magnification optical system that satisfies the following condition: 1.00<fFRt / (-fF)<7.00 where fFRt is the focal length of the lens group configured with lenses arranged closer to the image side than the focusing group in the telephoto end state. fF: focal length of the focusing group

3. a first lens group having negative refractive power, arranged in order from the object side along the optical axis; a rear group having three lens groups, When changing magnification, the spacing between adjacent lens groups changes, at least a part of any of the at least three lens groups in the rear group is a focusing group having negative refractive power that moves along the optical axis during focusing, A variable magnification optical system that satisfies the following condition: 0.70<fw / (-fF)<7.00 where fw is the focal length of the variable magnification optical system in the wide-angle end state fF: focal length of the focusing group

4. 4. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.50<fRw / (-fF)<4.00 where fRw is the focal length of the rear group in the wide-angle end state

5. 5. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.50<fRt / (-fF)<5.00 where fRt is the focal length of the rear group in the telephoto end state

6. 6. A variable magnification optical system according to claim 1, wherein the at least one lens group in the rear group is a plurality of lens groups.

7. 7. The variable magnification optical system according to claim 1, wherein the at least one lens group in the rear group includes a second lens group having positive refractive power that is arranged closest to the object side of the rear group.

8. 8. The variable magnification optical system according to claim 1, wherein the at least one lens group in the rear group includes a final lens group having positive refractive power and arranged closest to the image side of the rear group.

9. 9. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.10<fRPF / fRPR<0.60 where fRPF is the focal length of the lens group having positive refractive power and closest to the object side among the at least one lens group in the rear group. fRPR: the focal length of the lens group having positive refractive power and closest to the image side among the at least one lens group in the rear group

10. 10. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.50<fRPF / (-fF)<3.00 where fRPF is the focal length of the lens group having positive refractive power and closest to the object side among the at least one lens group in the rear group.

11. 11. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.05<Bfw / fRPR<0.35 where Bfw is the back focus of the variable magnification optical system in the wide-angle end state. fRPR: the focal length of the lens group having positive refractive power and closest to the image side among the at least one lens group in the rear group

12. 12. The variable magnification optical system according to claim 1, wherein the lens in the rear group arranged closest to the object side is a positive lens.

13. 13. The variable magnification optical system according to claim 12, wherein the lens in the rear group arranged closest to the object side is fixed relative to the image plane during magnification variation.

14. 14. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 60.00°<2ωw<90.00° where 2ωw is the total angle of view of the variable magnification optical system in the wide-angle end state.

15. 15. The variable magnification optical system according to claim 1, which satisfies the following condition: 1.50<(-f1) / fRw<3.00 where f1 is the focal length of the first lens group fRw: focal length of the rear lens group at the wide-angle end

16. 16. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.50<(-f1) / fRt<2.50 where f1 is the focal length of the first lens group fRt: focal length of the rear group in the telephoto end state

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

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