Variable magnification optical system, optical instrument, and method for manufacturing variable magnification optical system

Abstract

A variable magnification optical system (ZL) comprises a plurality of lens groups including: a first lens group (G1) having a positive refractive power and disposed closest to the object side; and a terminal lens group (GL) having a negative refractive power and disposed closest to the image surface side. The plurality of lens groups include at least six lens groups. When varying magnification, the intervals between adjacent lens groups change, and the following conditional expression is satisfied.　2.00 < f1 / (- fL) < 20.00. f1 is the focal length of the first lens group (G1), and fL is the focal length of the terminal lens group (GL).

Description

Variable magnification optical system, optical device, and method for manufacturing variable magnification optical system

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

[0002] Variable magnification optical systems suitable for photo cameras, electronic still cameras, video cameras, etc. have been proposed (see, for example, Patent Document 1). However, it is difficult to achieve good optical performance while realizing a small and lightweight variable magnification optical system.

[0003] Japanese Patent Application Laid-Open No. 2021-182053

[0004] A first variable power optical system according to the present invention has a plurality of lens groups including a first lens group having positive refractive power and arranged closest to the object side, and a final lens group having negative refractive power and arranged closest to the image side, the plurality of lens groups having at least six lens groups, the spacing between adjacent lens groups changing during variable power, and satisfying the following condition: 2.00<f1 / (-fL)<20.00, where f1 is the focal length of the first lens group and fL is the focal length of the final lens group.

[0005] A variable magnification optical system according to a second aspect of the present invention has a plurality of lens groups including a first lens group having positive refractive power and arranged closest to the object side, and a final lens group having negative refractive power and arranged closest to the image plane side, wherein the spacing between adjacent lens groups changes during magnification variation, and the following conditional expressions are satisfied: 8.00<f1 / fw<20.00 0.50<Bfw / fw<1.40 80.0°<2ωw where f1 is the focal length of the first lens group, fw is the focal length of the variable magnification optical system in the wide-angle end state, Bfw is the back focus of the variable magnification optical system in the telephoto end state, and 2ωw is the total angle of view of the variable magnification optical system in the wide-angle end state.

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

[0007] A first method for manufacturing a variable magnification optical system according to the present invention includes a plurality of lens groups including a first lens group having positive refractive power and arranged closest to the object side, and a final lens group having negative refractive power and arranged closest to the image side, the plurality of lens groups including at least six lens groups, and the lenses are arranged in a lens barrel so that the spacing between adjacent lens groups changes during magnification variation and the following condition is satisfied: 2.00<f1 / (-fL)<20.00, where f1 is the focal length of the first lens group and fL is the focal length of the final lens group.

[0008] 1 is a cross-sectional view of a variable magnification optical system according to Example 1 in a wide-angle end state (W), a middle distance focal state (M), and a telephoto end state (T). FIG. 2 is a diagram of various aberrations when the variable magnification optical system according to Example 1 is focused on infinity in the wide-angle end state. FIG. 3 is a diagram of various aberrations when the variable magnification optical system according to Example 1 is focused on infinity in the middle distance focal length state. FIG. 4 is a diagram of various aberrations when the variable magnification optical system according to Example 1 is focused on infinity in the telephoto end state. FIG. 5 is a cross-sectional view of a variable magnification optical system according to Example 2 in a wide-angle end state (W), a middle distance focal state (M), and a telephoto end state (T). FIG. 6 is a diagram of various aberrations when the variable magnification optical system according to Example 2 is focused on infinity in the middle distance focal length state. FIG. 7 is a diagram of various aberrations when the variable magnification optical system according to Example 2 is focused on infinity in the telephoto end state. FIG. 8 is a cross-sectional view of a variable magnification optical system according to Example 3 in a wide-angle end state (W), a middle distance focal state (M), and a telephoto end state (T). 10A and 10B are diagrams illustrating various aberrations of the variable magnification optical system of Example 3 when focusing on infinity in the wide-angle end state. FIG. 10B are diagrams illustrating various aberrations of the variable magnification optical system of Example 3 when focusing on infinity in the middle focal length state. FIG. 10C are diagrams illustrating various aberrations of the variable magnification optical system of Example 3 when focusing on infinity in the telephoto end state. FIG. 10D are cross-sectional views of the variable magnification optical system of Example 4 in the wide-angle end state (W), middle focal length state (M), and telephoto end state (T). FIG. 10E are diagrams illustrating various aberrations of the variable magnification optical system of Example 4 when focusing on infinity in the middle focal length state. FIG. 10F are diagrams illustrating various aberrations of the variable magnification optical system of Example 4 when focusing on infinity in the telephoto end state. FIG. 10H are cross-sectional views of the variable magnification optical system of Example 5 in the wide-angle end state (W), middle focal length state (M), and telephoto end state (T). FIG. 10H are diagrams illustrating various aberrations of the variable magnification optical system of Example 5 when focusing on infinity in the wide-angle end state. FIG. 10 is a diagram illustrating various aberrations when the variable magnification optical system according to Example 5 is focused on infinity in a medium focal length state. FIG. 11 is a diagram illustrating various aberrations when the variable magnification optical system according to Example 5 is focused on infinity in a telephoto end state. FIG. 12 is a diagram illustrating the configuration of a camera equipped with the variable magnification optical system according to each embodiment. FIG. 13 is a flowchart illustrating a method for manufacturing the variable magnification optical system according to the first embodiment. FIG. 14 is a flowchart illustrating a method for manufacturing the variable magnification optical system according to the second embodiment.

[0009] 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. 21 . As shown in FIG. 21 , this camera 1 is composed of a body 2 and a photographic lens 3 attached to the body 2. The body 2 includes an image sensor 4, a body control unit (not shown) that controls the operation of the digital camera, and an LCD screen 5. The photographic lens 3 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, and the like.

[0010] Light from a 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. Furthermore, the variable magnification optical system ZL shown in FIG. 21 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.

[0011] 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, has a plurality of lens groups, including a first lens group G1 having positive refractive power and positioned closest to the object, and a final lens group GL having negative refractive power and positioned closest to the image plane, as shown in FIG. 1 . The plurality of lens groups is configured to include at least six lens groups. When the magnification is changed, the spacing between adjacent lens groups changes.

[0012] With the above-described configuration, the variable magnification optical system ZL according to the first embodiment satisfies the following conditional expression (1): 2.00<f1 / (-fL)<20.00 (1) where f1 is the focal length of the first lens group G1, and fL is the focal length of the final lens group GL.

[0013] According to the first embodiment, it is possible to obtain a variable magnification optical system that is small and lightweight and 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. 5, the variable magnification optical system ZL(3) shown in Fig. 9, the variable magnification optical system ZL(4) shown in Fig. 13, or the variable magnification optical system ZL(5) shown in Fig. 17.

[0014] Conditional expression (1) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the final lens group GL, which is located closest to the image plane in the variable magnification optical system. By satisfying conditional expression (1), it is possible to effectively correct curvature of field, coma, and chromatic aberration of magnification.

[0015] If the corresponding value of conditional expression (1) exceeds the upper limit, the refractive power of the first lens group G1 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. It will also be difficult to correct fluctuations in aberrations due to magnification. By setting the upper limit of conditional expression (1) to 19.00, 18.00, 17.00, or 16.00, the effects of this embodiment can be further ensured.

[0016] If the corresponding value of conditional expression (1) is below the lower limit, the refractive power of the first lens group G1 becomes strong, making it difficult to correct curvature of field, coma, and chromatic aberration of magnification. By setting the lower limit of conditional expression (1) to 2.20, 2.40, 2.80, 3.00, or even 3.20, the effect of this embodiment can be further ensured.

[0017] Next, a variable magnification optical system according to a second embodiment will be described. A variable magnification optical system ZL(1), which is an example of a variable magnification optical system (zoom lens) ZL according to the second embodiment, is configured with a plurality of lens groups, including a first lens group G1 having positive refractive power and positioned closest to the object, and a final lens group GL having negative refractive power and positioned closest to the image plane, as shown in FIG. When the magnification is changed, the spacing between adjacent lens groups changes.

[0018] With the above configuration, the variable magnification optical system ZL according to the second embodiment satisfies the following conditional expressions (2) to (4): 8.00<f1 / fw<20.00 (2) 0.50<Bfw / fw<1.40 (3) 80.0°<2ωw (4) where f1: focal length of the first lens group G1 fw: focal length of the variable magnification optical system ZL in the wide-angle end state Bfw: back focus of the variable magnification optical system ZL in the telephoto end state 2ωw: total angle of view of the variable magnification optical system ZL in the wide-angle end state

[0019] According to the second embodiment, it is possible to obtain a variable magnification optical system that is small and lightweight and 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. 5, the variable magnification optical system ZL(3) shown in Fig. 9, the variable magnification optical system ZL(4) shown in Fig. 13, or the variable magnification optical system ZL(5) shown in Fig. 17.

[0020] Conditional expression (2) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (2), the variable magnification optical system ZL can be made compact.

[0021] If the value corresponding to conditional expression (2) exceeds the upper limit, the refractive power of the first lens group G1 will be weak, and the amount of movement during reflexion will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (2) to 19.00, 18.50, 18.00, 17.50, or even 17.00, the effect of this embodiment can be made more certain.

[0022] If the corresponding value of conditional expression (2) falls below the lower limit, the refractive power of the first lens group G1 becomes strong, making it difficult to correct curvature of field, coma, and chromatic aberration of magnification. By setting the lower limit of conditional expression (2) to 8.05, 8.10, 8.15, 8.20, or even 8.25, the effect of this embodiment can be further ensured.

[0023] Conditional expression (3) 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 variable magnification optical system ZL in the wide-angle end state. The back focus of the variable magnification optical system ZL is the air-equivalent distance on the optical axis from the lens surface of the variable magnification optical system ZL closest to the image plane to the image plane I. By satisfying conditional expression (3), the variable magnification optical system ZL can be made compact.

[0024] If the corresponding value of conditional expression (3) exceeds the upper limit, the back focus becomes long, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (3) to 1.38, 1.36, 1.34, 1.32, or even 1.30, the effect of this embodiment can be made more certain.

[0025] If the corresponding value of conditional expression (3) is below the lower limit, the refractive power of the variable-magnification optical system ZL will be weak, making it difficult to reduce the size of the optical system. By setting the lower limit of conditional expression (3) to 0.51, 0.52, 0.53, or even 0.55, the effect of this embodiment can be made more certain.

[0026] Conditional expression (4) defines an appropriate range for the full angle of view of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (4), it is possible to obtain a wide angle of view while effectively correcting various aberrations such as curvature of field, coma, and chromatic aberration of magnification.

[0027] If the corresponding value of conditional expression (4) falls below the lower limit, it becomes difficult to correct curvature of field, coma, and lateral chromatic aberration. By setting the lower limit of conditional expression (4) to 85.0° or even 90.0°, the effect of this embodiment can be further ensured.

[0028] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (2): 8.00<f1 / fw<20.00 (2) where fw is the focal length of the variable magnification optical system ZL in the wide-angle end state.

[0029] Conditional expression (2) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (2), the variable magnification optical system ZL can be made compact.

[0030] If the value corresponding to conditional expression (2) exceeds the upper limit, the refractive power of the first lens group G1 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (2) to 19.00, 18.50, 18.00, 17.50, or even 17.00, the effect of this embodiment can be made more certain.

[0031] If the corresponding value of conditional expression (2) falls below the lower limit, the refractive power of the first lens group G1 becomes strong, making it difficult to correct curvature of field, coma, and chromatic aberration of magnification. By setting the lower limit of conditional expression (2) to 8.05, 8.10, 8.15, 8.20, or even 8.25, the effect of this embodiment can be further ensured.

[0032] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (5): 2.50<f1 / ft<5.00 (5) where ft is the focal length of the variable magnification optical system ZL in the telephoto end state.

[0033] Conditional expression (5) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the variable magnification optical system ZL in the telephoto end state. By satisfying conditional expression (5), it is possible to obtain good optical performance while miniaturizing the optical system.

[0034] If the value corresponding to conditional expression (5) exceeds the upper limit, the refractive power of the first lens group G1 will be weak, and the amount of movement required for zooming will increase, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (5) to 4.90, 4.80, 4.70, 4.60, or even 4.50, the effect of this embodiment can be made even more certain.

[0035] If the corresponding value of conditional expression (2) is below the lower limit, the refractive power of the first lens group G1 becomes strong, making it difficult to correct curvature of field, coma, chromatic aberration of magnification, etc. By setting the lower limit of conditional expression (5) to 2.52, 2.54, 2.56, or even 2.58, the effect of this embodiment can be made more certain.

[0036] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (6): 0.040<dg1 / TLw<0.080 (6), where dg1 is the distance on the optical axis from the lens surface of the first lens group G1 closest to the object to the lens surface of the first lens group G1 closest to the image plane, and TLw is the total length of the variable magnification optical system ZL in the wide-angle end state.

[0037] Conditional expression (6) defines an appropriate relationship between the axial distance from the lens surface of the first lens group G1 closest to the object to the lens surface of the first lens group G1 closest to the image plane, and the overall length of the variable magnification optical system ZL in the wide-angle end state. The overall length of the variable magnification optical system ZL is the axial distance from the lens surface of the variable magnification optical system ZL closest to the object to the image plane I (however, the axial distance from the lens surface of the variable magnification optical system ZL closest to the image plane to the image plane I is the air-equivalent distance). Satisfying conditional expression (6) allows the variable magnification optical system ZL to be made compact.

[0038] If the value corresponding to conditional expression (6) exceeds the upper limit, the distance on the optical axis from the lens surface in the first lens group G1 closest to the object to the lens surface in the first lens group G1 closest to the image plane becomes long, making it difficult to reduce the size of the variable-magnification optical system ZL. By setting the upper limit of conditional expression (6) to 0.079, 0.078, 0.077, or even 0.076, the effects of this embodiment can be further ensured.

[0039] If the corresponding value of conditional expression (6) is below the lower limit, the overall length of the variable magnification optical system ZL becomes long, making it difficult to reduce the size of the variable magnification optical system ZL. By setting the lower limit of conditional expression (3) to 0.041, 0.042, or even 0.043, the effect of this embodiment can be made more certain.

[0040] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable to satisfy the following conditional expression (7): 2.00<f1 / fpB<15.00 (7), where fpB is the focal length of the image-side positive lens group GpB, which is arranged closest to the image side among the lens groups having positive refractive power included in the plurality of lens groups.

[0041] Conditional expression (7) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the image-side positive lens group GpB, which is the lens group having positive refractive power and is located closest to the image plane. By satisfying conditional expression (7), it is possible to effectively correct curvature of field, coma, chromatic aberration of magnification, and the like.

[0042] If the value corresponding to conditional expression (7) exceeds the upper limit, the refractive power of the image-side positive lens group GpB, which is arranged furthest to the image side among the lens groups having positive refractive power, becomes strong, making it difficult to correct curvature of field and chromatic aberration of magnification. By setting the upper limit of conditional expression (7) to 14.50, 14.00, 13.50, or even 13.00, the effects of this embodiment can be made more certain.

[0043] If the corresponding value of conditional expression (7) is below the lower limit, the refractive power of the first lens group G1 becomes strong, making it difficult to correct curvature of field, coma, and chromatic aberration of magnification. By setting the lower limit of conditional expression (4) to 2.50, 3.00, 3.50, or even 4.00, the effect of this embodiment can be made more certain.

[0044] In the variable magnification optical system ZL according to the first and second embodiments, it is desirable that the multiple lens groups include, arranged along the optical axis in order from the object side, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

[0045] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups includes, arranged along the optical axis in order from the object side, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and it is desirable to satisfy the following conditional expression (8): 1.00<(-f2) / fw<2.00 (8), where f2 is the focal length of the second lens group G2.

[0046] Conditional expression (8) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (8), it is possible to achieve a compact and lightweight lens while effectively correcting spherical aberration, lateral chromatic aberration, and the like.

[0047] If the value corresponding to conditional expression (8) exceeds the upper limit, the refractive power of the second lens group G2 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (8) to 1.90, 1.85, 1.80, 1.75, or even 1.70, the effect of this embodiment can be made more certain.

[0048] If the corresponding value of conditional expression (8) falls below the lower limit, the refractive power of the second lens group G2 becomes strong, making it difficult to correct high-order spherical aberration, lateral chromatic aberration, etc. By setting the lower limit of conditional expression (8) to 1.01, or even 1.02, the effect of this embodiment can be made even more certain.

[0049] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups includes, in order from the object side along the optical axis, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and it is desirable to satisfy the following conditional expression (9): 0.500<f2 / fL<1.200 (9), where f2 is the focal length of the second lens group G2.

[0050] Conditional expression (9) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the final lens group GL. By satisfying conditional expression (9), it is possible to achieve a compact and lightweight lens while effectively correcting spherical aberration and lateral chromatic aberration.

[0051] If the value corresponding to conditional expression (9) exceeds the upper limit, the refractive power of the second lens group G2 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (9) to 1.180, 1.140, or even 1.100, the effect of this embodiment can be made even more certain.

[0052] If the corresponding value of conditional expression (9) falls below the lower limit, the refractive power of the second lens group G2 becomes too strong, making it difficult to correct high-order spherical aberration and lateral chromatic aberration. Furthermore, the refractive power of the final lens group GL becomes too weak, making it difficult to reduce the size of the optical system. By setting the lower limit of conditional expression (9) to 0.510, 0.515, 0.520, 0.540, 0.560, 0.580, or even 0.600, the effects of this embodiment can be further ensured.

[0053] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups includes, arranged along the optical axis in order from the object side, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and it is desirable to satisfy the following conditional expression (10): 0.70<f3 / (−fL)<3.00 (10), where f3 is the focal length of the third lens group G3.

[0054] Conditional expression (10) defines an appropriate relationship between the focal length of the third lens group G3 and the focal length of the final lens group GL. By satisfying conditional expression (10), it is possible to achieve a compact and lightweight lens while effectively correcting spherical aberration and axial chromatic aberration.

[0055] If the value corresponding to conditional expression (10) exceeds the upper limit, the refractive power of the third lens group G3 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (10) to 2.98, 2.96, 2.94, or even 2.92, the effect of this embodiment can be made more certain.

[0056] If the corresponding value of conditional expression (10) falls below the lower limit, the refractive power of the third lens group G3 becomes strong, causing spherical aberration and axial chromatic aberration, making it difficult to correct these aberrations during zooming. Furthermore, the refractive index of the final lens group GL becomes weak, making it difficult to reduce the size of the optical system. By setting the lower limit of conditional expression (9) to 0.73, 0.74, or even 0.75, the effects of this embodiment can be further ensured.

[0057] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups preferably includes, in order from the object side along the optical axis, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and preferably satisfies the following conditional expression (11): 4.00<f1 / (-f2)<14.00 (11), where f2 is the focal length of the second lens group G2.

[0058] Conditional expression (11) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the second lens group G2. By satisfying conditional expression (11), it is possible to achieve a compact and lightweight lens while effectively correcting curvature of field, coma, and chromatic aberration of magnification.

[0059] If the value corresponding to conditional expression (11) exceeds the upper limit, the refractive power of the first lens group G1 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (10) to 13.80, 13.60, 13.40, 13.20, or even 13.00, the effect of this embodiment can be made more certain.

[0060] If the corresponding value of conditional expression (11) is below the lower limit, the refractive power of the first lens group G1 becomes strong, making it difficult to correct curvature of field, coma, and chromatic aberration of magnification. By setting the lower limit of conditional expression (11) to 4.20, 4.40, 4.60, 4.80, or even 5.00, the effect of this embodiment can be made more certain.

[0061] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups includes, arranged along the optical axis in order from the object side, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and it is desirable to satisfy the following conditional expression (12): 3.00<f1 / f3<6.00 (12), where f3 is the focal length of the third lens group G3.

[0062] Conditional expression (12) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the third lens group G3. By satisfying conditional expression (12), it is possible to achieve a compact and lightweight lens while effectively correcting curvature of field, coma, and chromatic aberration of magnification.

[0063] If the value corresponding to conditional expression (12) exceeds the upper limit, the refractive power of the first lens group G1 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (12) to 5.80, 5.60, 5.40, 5.20, 5.00, or even 4.80, the effect of this embodiment can be made more certain.

[0064] If the corresponding value of conditional expression (12) is below the lower limit, the refractive power of the first lens group G1 becomes strong, making it difficult to correct curvature of field, coma, and chromatic aberration of magnification. By setting the lower limit of conditional expression (12) to 3.10, 3.20, 3.30, 3.40, or even 3.50, the effect of this embodiment can be made more certain.

[0065] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups preferably includes, in order from the object side along the optical axis, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and preferably satisfies the following conditional expression (13): 0.15<(-f2) / f3<1.20 (13), where f2 is the focal length of the second lens group G2 and f3 is the focal length of the third lens group G3.

[0066] Conditional expression (13) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the third lens group G3. By satisfying conditional expression (13), it is possible to achieve a compact and lightweight lens while effectively correcting high-order spherical aberration and lateral chromatic aberration.

[0067] If the value corresponding to conditional expression (13) exceeds the upper limit, the refractive power of the second lens group G2 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (13) to 1.15, 1.12, 1.09, 1.06, 1.03, 1.00, or even 0.97, the effect of this embodiment can be made more certain.

[0068] If the corresponding value of conditional expression (13) falls below the lower limit, the refractive power of the second lens group G2 becomes strong, making it difficult to correct high-order spherical aberration and lateral chromatic aberration. By setting the lower limit of conditional expression (13) to 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, or even 0.30, the effect of this embodiment can be further ensured.

[0069] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups preferably includes, in order from the object side along the optical axis, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and preferably satisfies the following conditional expression (14): 0.70<f3 / fpB<3.00 (14), where f3 is the focal length of the third lens group G3, and fpB is the focal length of the image-side positive lens group GpB that is arranged closest to the image side among the lens groups having positive refractive power included in the plurality of lens groups.

[0070] Conditional expression (14) defines an appropriate relationship between the focal length of the third lens group G3 and the focal length of the image-side positive lens group GpB, which is the lens group having positive refractive power and is located closest to the image side. By satisfying conditional expression (14), various aberrations such as spherical aberration, axial chromatic aberration, curvature of field, and chromatic aberration of magnification can be effectively corrected.

[0071] If the value corresponding to conditional expression (14) exceeds the upper limit, the refractive power of the positive lens group GpB, which is positioned furthest to the image side among the lens groups having positive refractive power, becomes strong, making it difficult to correct curvature of field and chromatic aberration of magnification. By setting the upper limit of conditional expression (14) to 2.98, 2.96, 2.94, or even 2.92, the effects of this embodiment can be made more certain.

[0072] If the corresponding value of conditional expression (14) falls below the lower limit, the refractive power of the third lens group G3 becomes strong, causing spherical aberration and axial chromatic aberration, making it difficult to correct fluctuations in these aberrations during zooming. By setting the lower limit of conditional expression (14) to 0.74, 0.78, 0.82, 0.86, or even 0.90, the effect of this embodiment can be made even more certain.

[0073] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups includes, in order from the object side along the optical axis, a first lens group G1, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4, and it is desirable to satisfy the following conditional expression (15): 0.07<f3 / f4<0.40 (15), where f3 is the focal length of the third lens group G3 and f4 is the focal length of the fourth lens group G4.

[0074] Conditional expression (15) defines an appropriate relationship between the focal length of the third lens group G3 and the focal length of the fourth lens group G4. By satisfying conditional expression (15), it is possible to achieve a compact and lightweight lens while effectively correcting spherical aberration, axial chromatic aberration, and the like.

[0075] If the value corresponding to conditional expression (15) exceeds the upper limit, the refractive power of the third lens group G3 will be weak, and the amount of movement during magnification will be large, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (15) to 0.38, 0.36, 0.34, or even 0.32, the effect of this embodiment can be made more certain.

[0076] If the corresponding value of conditional expression (15) falls below the lower limit, the refractive power of the third lens group G3 becomes strong, causing spherical aberration and axial chromatic aberration, making it difficult to correct fluctuations in these aberrations during zooming. By setting the lower limit of conditional expression (15) to 0.09, 0.10, 0.12, 0.14, 0.16, or even 0.18, the effects of this embodiment can be further ensured.

[0077] In the variable magnification optical systems ZL according to the first and second embodiments, the multiple lens groups include, arranged along the optical axis in order from the most object side, a first lens group G1, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a final lens group GL, and it is desirable to satisfy the following conditional expression (16): 0.20<dg1 / dg2<0.50 (16), where dg1 is the distance on the optical axis from the lens surface of the first lens group G1 closest to the object to the lens surface of the first lens group G1 closest to the image plane, and dg2 is the distance on the optical axis from the lens surface of the second lens group G2 closest to the object to the lens surface of the second lens group G2 closest to the image plane.

[0078] Conditional expression (16) defines an appropriate relationship between the thickness of the first lens group G1 and the thickness of the second lens group G2. By satisfying conditional expression (16), it is possible to achieve a compact and lightweight lens system.

[0079] If the value corresponding to conditional expression (16) exceeds the upper limit, the thickness of the first lens group G1 increases, making it difficult to reduce the size of the optical system. By setting the upper limit of conditional expression (16) to 0.49, 0.48, 0.47, 0.46, or even 0.45, the effect of this embodiment can be further ensured.

[0080] If the corresponding value of conditional expression (16) is below the lower limit, the thickness of the second lens group G2 increases, making it difficult to reduce the size of the optical system. By setting the lower limit of conditional expression (16) to 0.21, 0.22, 0.23, or even 0.24, the effect of this embodiment can be made more certain.

[0081] In the variable magnification optical systems ZL according to the first and second embodiments, the plurality of lens groups includes, arranged along the optical axis in order from the object side, a first lens group G1, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and it is desirable that the lens group arranged closer to the image plane than the second lens group has at least one lens La that satisfies the following conditional expression (17): 70.00<νd (17), where νd is the Abbe number of the lens La with reference to the d line.

[0082] Conditional expression (17) defines an appropriate range of the Abbe number, based on the d-line, of lens La included in the lens group located closer to the image plane than the second lens group. By satisfying conditional expression (17), fluctuations in axial chromatic aberration and lateral chromatic aberration due to magnification variation can be effectively corrected.

[0083] If the corresponding value of conditional expression (17) falls below the lower limit, it becomes difficult to correct fluctuations in axial chromatic aberration and lateral chromatic aberration that accompany zooming. By setting the lower limit of conditional expression (17) to 71.00, 71.50, 72.00, 72.50, 73.00, 73.50, or even 74.0, the effects of this embodiment can be further ensured. It is preferable that lens La satisfying conditional expression (17) be used in a cemented lens. It is also preferable that lens La satisfying conditional expression (17) be disposed closer to the object side than the final lens group GL.

[0084] The variable-magnification optical system ZL according to the first and second embodiments is preferably configured to include, in order from the object side along the optical axis, a first lens group G1, a second lens group G2 having negative refractive power, multiple lens groups having positive refractive power, and multiple lens groups having negative refractive power arranged consecutively including a final lens group GL. By using such a configuration, it is possible to ensure a large variable-magnification ratio while suppressing fluctuations in various aberrations during magnification variation.

[0085] The variable magnification optical system ZL according to the first and second embodiments is composed of, arranged along the optical axis in order from the object side, a first lens group G1, a second lens group G2 having negative refractive power, a plurality of lens groups having positive refractive power, and a plurality of lens groups having negative refractive power arranged successively including a final lens group GL, and it is desirable that the lens groups having positive refractive power consist of three lens groups having positive refractive power. By adopting such a configuration, it is possible to achieve compactness while obtaining good optical performance.

[0086] In the variable-magnification optical systems ZL according to the first and second embodiments, it is desirable that the lens group arranged adjacent to the final lens group GL on the object side move during focusing, as this configuration can suppress fluctuations in field curvature during focusing.

[0087] In the variable magnification optical system ZL according to the first and second embodiments, it is desirable to satisfy the following conditional expression (18): 2.80<ft / fw<4.50 (18) where fw is the focal length of the variable magnification optical system ZL in the wide-angle end state, and ft is the focal length of the variable magnification optical system ZL in the telephoto end state.

[0088] Conditional expression (18) defines an 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 variable magnification optical system ZL in the telephoto end state. By satisfying conditional expression (18), it is possible to achieve a compact and lightweight lens while obtaining good optical performance.

[0089] If the value corresponding to conditional expression (18) exceeds the upper limit, the amount of movement during magnification change becomes large, making it difficult to correct aberration fluctuations. By setting the upper limit of conditional expression (18) to 4.30, 4.10, 3.90, or even 3.80, the effect of this embodiment can be made more certain.

[0090] If the corresponding value of conditional expression (18) falls below the lower limit, the difference between the focal length of the variable magnification optical system ZL in the wide-angle end state and the focal length of the variable magnification optical system ZL in the telephoto end state becomes small, which is undesirable because the usable focal length range becomes too narrow. By setting the lower limit of conditional expression (18) to 2.90, 2.95, 3.00, 3.05, 3.10, or even 3.15, the effects of this embodiment can be made more certain.

[0091] In the variable magnification optical system ZL according to the first and second embodiments, it is desirable to satisfy the following conditional expression (4-1): 80.0°<2ωw<110.0° (4-1), where 2ωw is the total angle of view of the variable magnification optical system ZL in the wide-angle end state.

[0092] Condition (4-1) defines an appropriate range for the entire angle of view of the variable magnification optical system ZL in the wide-angle end state. By satisfying condition (4-1), it is possible to obtain a wide angle of view while effectively correcting various aberrations such as curvature of field, coma, and chromatic aberration of magnification.

[0093] If the corresponding value of conditional expression (4-1) exceeds the upper limit, it becomes difficult to obtain a wide angle of view while satisfactorily correcting various aberrations such as curvature of field, coma, and chromatic aberration of magnification. By setting the upper limit of conditional expression (4-1) to 105.0° or even 100.0°, the effect of this embodiment can be made even more certain.

[0094] If the corresponding value of conditional expression (4-1) is below the lower limit, it becomes difficult to obtain a wide angle of view while satisfactorily correcting various aberrations such as curvature of field, coma, and chromatic aberration of magnification. By setting the lower limit of conditional expression (4-1) to 85.0° or even 90.0°, the effect of this embodiment can be made even more certain.

[0095] In the variable magnification optical system ZL according to the first and second embodiments, it is desirable to satisfy the following conditional expression (19): 30.0°<2ωt<50.0° (19) where 2ωt is the total angle of view of the variable magnification optical system ZL in the telephoto end state.

[0096] Conditional expression (19) defines an appropriate range for the full angle of view of the variable-magnification optical system ZL in the telephoto end state. By satisfying conditional expression (19), it is possible to ensure a large variable-magnification ratio while suppressing fluctuations in various aberrations during magnification.

[0097] If the corresponding value of conditional expression (19) exceeds the upper limit, it becomes difficult to suppress fluctuations in various aberrations during zooming while ensuring a large zoom ratio. By setting the upper limit of conditional expression (19) to 45.0°, or even 40.0°, the effect of this embodiment can be made even more certain.

[0098] If the corresponding value of conditional expression (19) falls below the lower limit, it becomes difficult to suppress fluctuations in various aberrations during zooming while ensuring a large zoom ratio. By setting the lower limit of conditional expression (19) to 32.0°, or even 33.0°, the effects of this embodiment can be made even more certain.

[0099] Next, with reference to FIG. 22 , a manufacturing method for the variable magnification optical system ZL according to the first embodiment will be outlined. First, the lens system has a plurality of lens groups, including a first lens group G1 having positive refractive power and positioned closest to the object, and a final lens group GL having negative refractive power and positioned closest to the image plane, and the plurality of lens groups is arranged to have at least six lens groups (Step ST1). Next, the lens groups are configured so that the spacing between adjacent lens groups changes during magnification (Step ST2). Then, the lenses are arranged within the lens barrel so as to satisfy at least the following conditional expression (1) (Step ST3). This manufacturing method makes it possible to manufacture a variable magnification optical system that is compact and lightweight while also having good optical performance: 2.00<f1 / (−fL)<20.00 (1), where f1 is the focal length of the first lens group G1, and fL is the focal length of the final lens group GL.

[0100] Next, a manufacturing method for a variable-magnification optical system ZL according to the second embodiment will be outlined with reference to FIG. 23 . First, a plurality of lens groups are arranged, including a first lens group G1 having positive refractive power and positioned closest to the object, and a final lens group GL having negative refractive power and positioned closest to the image plane (step ST11). Next, a configuration is established in which the spacing between adjacent lens groups changes during magnification (step ST12). Then, the lenses are arranged within the lens barrel so as to satisfy at least the following conditional expressions (2) to (4) (step ST13). This manufacturing method makes it possible to manufacture a variable-magnification optical system that is compact and lightweight while also having excellent optical performance. 8.00<f1 / fw<20.00 (2) 0.50<Bfw / fw<1.40 (3) 80.0°<2ωw (4) where f1: focal length of the first lens group fw: focal length of the variable magnification optical system ZL in the wide-angle end state Bfw: back focus of the variable magnification optical system ZL in the wide-angle end state 2ωw: total angle of view of the variable magnification optical system ZL in the wide-angle end state

[0101] Variable-magnification optical systems ZL according to examples of each embodiment will be described below with reference to the drawings. FIGS. 1, 5, 9, 13, and 17 are cross-sectional views showing the configuration and refractive power distribution of variable-magnification optical systems ZL {ZL(1) to ZL(5)} according to Examples 1 to 5. In the cross-sectional views of the variable-magnification optical systems ZL(1) to ZL(5) according to Examples 1 to 5, arrows indicate the movement direction of each lens group when changing magnification from the wide-angle end state (W) to the intermediate focal length state (M) and the telephoto end state (T). Additionally, an arrow along with the word "focus" indicates the movement direction of the focusing lens group when focusing from infinity to a close-distance object.

[0102] 1, 5, 9, 13, and 17, each lens group is represented by a combination of a symbol G and a number, and each lens is represented by a combination of a 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 groups, 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.

[0103] Tables 1 to 5 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, and Table 5 for Example 5. In each example, the d-line (wavelength λ=587.6 nm) and g-line (wavelength λ=435.8 nm) were selected as the targets for calculating aberration characteristics.

[0104] In the table of [Overall Specifications], fw is the focal length of the variable magnification optical system in the wide-angle end state, dg1 is the axial distance from the lens surface of the first lens group G1 closest to the object to the lens surface of the first lens group G1 closest to the image plane, and dg2 is the axial distance from the lens surface of the second lens group G2 closest to the object to the lens surface of the second lens group G2 closest to the image plane. FNO is the F-number, 2ω is the total angle of view (unit: ° (degrees)), Y is the image height, TL is the axial distance from the lens surface of the variable magnification optical system closest to the object to the lens surface of the second lens group G2 closest to the image plane plus BF (back focus), and BF is the axial distance (air-equivalent distance) from the lens surface of the variable magnification optical system closest to the image plane I, all of which show values ​​in the wide-angle end state (W), the intermediate focal length state (M), and the telephoto end state (T).

[0105] 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 located 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 material of the optical element with respect to the d-line, and vd is the Abbe number of the material of the optical element with respect to the d-line. The "∞" next to the radius of curvature indicates a plane 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.

[0106] In the table of [Aspherical Surface Data], the shape of the aspherical surface shown in [Lens Specifications] is expressed 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 spherical surface (paraxial radius of curvature), κ is the conic constant, and Ai is the ith aspherical coefficient. "E-n" is "×10 -n For example, 1.234E-05 = 1.234 x 10 -5 The second-order aspherical coefficient A2 is 0, and is therefore omitted.

[0107] X(y)=(y 2 / R) / {1+(1-κ×y 2 / R2 ) 1 / 2} + A4 × y 4 +A6×y 6 +A8×y 8 +A10×y 10 …(A)

[0108] The "Variable Distance Data" table shows the surface spacing for surface number i, where the surface spacing in the "Lens Specifications" table is (di). The "Variable Distance Data" table also shows the surface spacing when focused at infinity and when focused at close range. f indicates the focal length of the variable magnification optical system, and β indicates the magnification.

[0109] The table of [Lens Group Data] shows the first surface (the surface closest to the object) and focal length of each lens group.

[0110] 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.

[0111] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0112] First Example The first example will be described with reference to FIGS. 1 to 4 and Table 1. FIG. 1 shows the lens configuration of a variable magnification optical system according to the first example. The variable magnification optical system ZL(1) according to the first example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power. When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the spacing between adjacent lens groups changes. That is, the spacing between the first lens group G1 and the second lens group G2, between the second lens group G2 and the third lens group G3, between the third lens group G3 and the fourth lens group G4, between the fourth lens group G4 and the fifth lens group G5, and between the fifth lens group G5 and the sixth lens group G6 changes. An aperture diaphragm S is disposed between the second lens group G2 and the third lens group G3, and when varying the magnification, the aperture diaphragm S moves along the optical axis together with the third lens group G3. Furthermore, when focusing from an object at infinity to a close object, the entire fifth lens group G5 moves toward the object along the optical axis. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of that lens group, and this also applies to all of the following examples.

[0113] The first lens group G1 is composed of a cemented lens formed by cementing together a meniscus negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, which are arranged in order from the object side along the optical axis.

[0114] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L21 with its convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a meniscus negative lens L24 with its concave surface facing the object side. The image-side lens surface of the negative lens L21 is aspheric.

[0115] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a meniscus positive lens L31 with its convex surface facing the object side, and a cemented lens formed by cementing together a biconvex positive lens L32 and a meniscus negative lens L33 with its concave surface facing the object side. The object-side lens surface of the positive lens L31 is aspheric. A diaphragm S is disposed on the object side of the third lens group G3.

[0116] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a meniscus negative lens L41 with its convex surface facing the object side and a biconvex positive lens L42. The object-side lens surface of the negative lens L41 is aspherical.

[0117] The fifth lens group G5 is composed of a biconvex positive lens L51. When focusing from an object at infinity to a close object, the entire fifth lens group G5 moves toward the object along the optical axis. The image-side lens surface of the positive lens L51 is aspherical.

[0118] The sixth lens group G6 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L61 with its convex surface facing the object side, a biconvex positive lens L62, and a biconcave negative lens L63. An aspheric surface is formed on the object side lens surface of the positive lens L62. An image plane I is located on the image side of the negative lens L63. A filter FL is located between the sixth lens group G6 and the image plane I.

[0119] In this embodiment, the sixth lens group G6 constitutes the final lens group GL, and the fifth lens group G5 constitutes the image-side positive lens group GpB. In addition, among the lens groups located closer to the image side than the second lens group G2, the lenses La that satisfy conditional expression (17) are the positive lens L32 and the positive lens L42, and are located closer to the object side than the final lens group GL.

[0120] The following Table 1 lists the specifications of the variable magnification optical system according to Example 1. Note that the data in [Lens specifications] does not include the filter FL, and TL (total length of the variable magnification optical system) and BF (back focus) in [Overall specifications] indicate air-equivalent distances.

[0121] (Table 1) [Overall specifications] Magnification ratio = 3.71 dg1 = 5.574 dg2 = 22.302 W M T FNO 4.000 4.000 4.000 2ω 51.261 22.341 16.718 Y 20.98 21.60 21.70 TL 125.098 153.244 180.113 BF 17.828 47.070 62.155 [Lens specifications] Surface number R D nd νd 1 364.671 1.200 1.84666 23.80 2 228.565 4.374 1.77250 49.62 3 -597.104 d1 (variable) 4 90.749 1.200 1.74389 49.53 5* 16.976 9.034 6 -126.919 1.200 1.87733 41.02 7 47.914 0.200 8 31.179 6.687 1.80518 25.45 9 -106.647 2.781 10 -28.331 1.200 1.59349 67.00 11 -70.145 d2 (variable) 12 ∞ 2.000 (Aperture) 13* 38.645 3.234 1.85108 40.12 14 367.795 1.427 15 291.470 5.033 1.49782 82.57 16 -27.073 1.200 1.94305 33.50 17 -96.612 d3(variable) 18* 49.699 1.200 2.00100 29.12 19 19.978 7.900 1.55032 75.50 20 -80.418 d4(can be changed) 21 32.510 7.545 1.83391 43.94 22* -44.974 d5(can be changed) 23 32.145 1.200 1.89429 39.03 24 16.964 5.363 25* 323.637 6.013 1.80301 25.53 26 -28.010 0.200 27 -28.260 1.200 1.92099 35.73 28 58.692 BF (can be changed) [Aspherical surface data] Surface 5 κ=0.0000,A4=2.00192E-05,A6=1.05578E-08,A8=1.01341E-10,A10=-1.12924E-13 Surface 13 κ=1.0000,A4=-3.36047E-06,A6=-6.38709E-09,A8=-2.88936E-11,A10=-7.27546E-14 Surface 18 κ=1.0000,A4=-3.28153E-06,A6=1.09801E-08,A8=8.09630E-11,A10=-1.14564E-13 For the 22nd surface, κ=1.0000, A4=1.34092E-05, A6=-2.15527E-08, A8=6.58653E-11, A10=-8.46737E-14. For the 25th surface, κ=1.0000, A4=-2.44664E-06, A6=-1.56539E-08, A8=-1.10040E-10, A10=6.27084E-13 [Variable distance data] Focused at infinity Focused at close range W M T W M T f 18.500 50.080 68.600 - - - β - - - - -0.0927 -0.2509 -0.3410 d1 1.000 26.723 43.106 1.000 26.723 43.106 d2 21.355 2.010 0.200 21.355 2.010 0.200 d3 9.961 2.271 0.200 9.961 2.271 0.200 d4 0.614 1.774 1.662 0.187 0.632 0.200 d5 2.950 2.006 1.400 3.377 3.147 2.818 BF 17.828 47.070 62.155 17.828 47.070 62.155 [Lens Group Data] Group Initial Surface Focal Length G1 1 304.585 G2 4 -23.938 G3 13 64.139 G4 18 213.170 G5 21 23.676 G6 23 -22.465.

[0122] FIG. 2 shows various aberration diagrams of the variable magnification optical system of Example 1 when focused at infinity in the wide-angle end state. FIG. 3 shows various aberration diagrams of the variable magnification optical system of Example 1 when focused at infinity at a mid-range focal length. FIG. 4 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 represents the F-number, and Y represents 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 represents the d-line (wavelength λ=587.6 nm), and g represents the g-line (wavelength λ=435.8 nm). In the astigmatism diagram, the solid line represents the sagittal image plane, and the dashed line represents 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.

[0123] 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.

[0124] Second Example The second example will be described with reference to FIGS. 5 to 8 and Table 2. FIG. 5 shows the lens configuration of a variable magnification optical system according to the second example. The variable magnification optical system ZL(2) according to the second example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the spacing between adjacent lens groups changes. That is, the distances between the first lens group G1 and the second lens group G2, between the second lens group G2 and the third lens group G3, between the third lens group G3 and the fourth lens group G4, between the fourth lens group G4 and the fifth lens group G5, and between the fifth lens group G5 and the sixth lens group G6 change. An aperture stop S is disposed between the second lens group G2 and the third lens group G3, and moves along the optical axis together with the third lens group G3 during zooming. When focusing from an object at infinity to a close object, the entire fifth lens group G5 moves toward the object along the optical axis.

[0125] The first lens group G1 is composed of a cemented lens formed by cementing together a meniscus negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, which are arranged in order from the object side along the optical axis.

[0126] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L21 with its convex surface facing the object side, a biconcave negative lens L22, and a biconvex positive lens L23. The image-side lens surface of the negative lens L21 is aspheric.

[0127] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L31, a cemented lens formed by cementing together a meniscus positive lens L32 with its concave surface facing the object side and a biconcave negative lens L33. The object-side lens surface of the positive lens L31 is aspheric. A diaphragm S is disposed on the object side of the third lens group G3.

[0128] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a negative meniscus lens L41 with its convex surface facing the object side and a positive meniscus lens L42 with its convex surface facing the object side. The lens surface of the positive lens L42 facing the image plane side is aspherical.

[0129] The fifth lens group G5 is composed of a biconvex positive lens L51. The image-side lens surface of the positive lens L51 is aspherical. When focusing from an object at infinity to a close object, the entire fifth lens group G5 moves toward the object along the optical axis.

[0130] The sixth lens group G6 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L61 with its convex surface facing the object side, a biconvex positive lens L62, and a biconcave negative lens L63. An image plane I is located on the image side of the negative lens L63. A filter FL is located between the sixth lens group G6 and the image plane I.

[0131] In this embodiment, the sixth lens group G6 constitutes the final lens group GL, and the fifth lens group G5 constitutes the image-side positive lens group GpB. In addition, among the lens groups located closer to the image side than the second lens group G2, the lenses La that satisfy conditional expression (17) are the positive lens L32 and the positive lens L42, and are located closer to the object side than the final lens group GL.

[0132] The values ​​of the specifications of the variable magnification optical system according to Example 2 are listed below in Table 2. Note that the data for [Lens specifications] does not include the filter FL, and TL (total length of the variable magnification optical system) and BF (back focus) in [Overall specifications] indicate air-equivalent distances.

[0133] (Table 2) [Overall specifications] Magnification ratio = 3.17 dg1 = 7.54 dg2 = 18.69 W M T FNO 4.000 4.000 4.000 2ω 51.048 26.409 19.058 Y 20.72 21.59 20.30 TL 134.755 146.923 166.329 BF 19.695 39.326 50.740 [Lens specifications] Surface number R D nd νd 1 121.487 1.200 1.89157 27.14 2 100.251 6.340 1.49782 82.57 3 -556.022 d1 (variable) 4 1619.784 1.200 1.74389 49.53 5* 16.866 10.094 6 -57.563 1.200 1.53350 73.40 7 44.531 0.200 8 34.807 6.000 1.74419 28.02 9 -799.085 d2 (variable) 10 ∞ 2.000 (stop) 11* 22.350 6.650 1.65448 34.30 12 -82.943 1.577 13 -169.855 3.853 1.49782 82.57 14 -24.663 1.200 1.88637 28.10 15 156.229 d3(variable) 16 21.636 1.200 1.97758 30.69 17 12.867 9.260 1.49782 82.57 18* 84.284 d4(can be changed) 19 26.695 6.270 1.88072 40.82 20* -59.386 d5(can be changed) 21 238.638 1.200 2.00100 29.12 22 19.523 2.177 23 28.813 6.577 1.84913 26.33 24 -33.520 1.284 25 -40.253 1.200 1.93392 34.32 26 33.441 BF (can be changed) [Aspherical surface] Surface 5 κ=0.0000,A4=1.58905E-05,A6=2.61686E-08,A8=-5.23651E-11,A10=3.41143E-13 Surface 11 κ=1.0000,A4=-2.82337E-06,A6=4.98559E-09,A8=-2.89761E-11,A10=1.08399E-13 Surface 18 κ=1.0000,A4=1.29248E-05,A6=-6.57159E-08,A8=5.60798E-10,A10=-4.27741E-12 Surface 20: κ=1.0000, A4=1.83192E-05, A6=-1.70783E-08, A8=-1.72480E-10, A10=5.36904E-13 [Variable interval date] Infinity focus state Close focus state W M T W M T f 18.500 41.000 58.600 - - - β - - - -0.0991 -0.2050 -0.2802 d1 1.000 21.042 36.611 1.000 21.042 36.611 d2 33.346 10.532 5.307 33.346 10.532 5.307 d3 5.729 1.438 0.200 5.729 1.438 0.200 d4 4.108 3.703 2.590 3.648 2.691 1.147 d5 0.195 0.200 0.200 0.655 1.212 1.643 BF 19.695 39.326 50.740 19.695 39.326 50.740 [Lens Group Data] Group Initial Surface Focal Length G1 1 232.147 G2 4 -24.289 G3 11 55.276 G4 16 285.623 G5 19 21.649 G6 21 -22.996.

[0134] Fig. 6 is a diagram showing various aberrations when the variable magnification optical system of Example 2 is focused at infinity in the wide-angle end state, Fig. 7 is a diagram showing various aberrations when the variable magnification optical system of Example 2 is focused at infinity at a medium focal length, and Fig. 8 is a diagram showing various aberrations when the variable magnification optical system of Example 2 is focused at infinity in the telephoto end state. It can be seen from each aberration diagram that the variable magnification optical system of Example 2 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0135] Third Example A third example will be described with reference to FIGS. 9 to 12 and Table 3. FIG. 9 shows the lens configuration of a variable magnification optical system according to the third example. The variable magnification optical system ZL(3) according to the third example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the spacing between adjacent lens groups changes. That is, the distances between the first lens group G1 and the second lens group G2, between the second lens group G2 and the third lens group G3, between the third lens group G3 and the fourth lens group G4, between the fourth lens group G4 and the fifth lens group G5, and between the fifth lens group G5 and the sixth lens group G6 change. An aperture stop S is disposed between the second lens group G2 and the third lens group G3, and the aperture stop S moves along the optical axis together with the third lens group G3 during zooming. When focusing from an object at infinity to a close object, the fourth lens group G4 and the fifth lens group G5 move toward the image plane along different trajectories in the wide-angle end state, and the fourth lens group G4 and the fifth lens group G5 move toward the object along different trajectories in the telephoto end state.

[0136] The first lens group G1 is composed of a cemented lens formed by cementing together a negative meniscus lens L11 with its convex surface facing the object side and a positive meniscus lens L12 with its convex surface facing the object side, which are arranged in order from the object side along the optical axis.

[0137] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L21 with its convex surface facing the object side, a biconcave negative lens L22, and a biconvex positive lens L23. The image-side lens surface of the negative lens L21 is aspheric.

[0138] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a meniscus positive lens L31 with its convex surface facing the object side, a cemented lens formed by cementing a meniscus negative lens L32 with its convex surface facing the object side and a biconvex positive lens L33, and a cemented lens formed by cementing a biconcave negative lens L34 and a biconvex positive lens L35. The object-side lens surface of the positive lens L31 is aspheric. A diaphragm S is arranged on the object side of the third lens group G3.

[0139] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L41 with its concave surface facing the object side, and a biconvex positive lens L42. The image-side lens surface of the positive lens L42 is aspheric. When focusing from an object at infinity to a close distance, in the wide-angle end state, the fourth lens group G4 moves along the optical axis toward the image side, and in the telephoto end state, the fourth lens group G4 moves toward the object side.

[0140] The fifth lens group G5 is composed of a biconcave negative lens L51. The image-side lens surface of the negative lens L51 is aspherical. When focusing from an object at infinity to a close object, the fifth lens group G5 moves toward the image side in the wide-angle end state, and moves toward the object side in the telephoto end state.

[0141] The sixth lens group G6 is composed of a biconcave negative lens L61. An image plane I is disposed on the image side of the negative lens L61. A filter FL is disposed between the sixth lens group G6 and the image plane I.

[0142] In this embodiment, the sixth lens group G6 constitutes the final lens group GL, and the fourth lens group G4 constitutes the image-side positive lens group GpB. In addition, among the lens groups located closer to the image plane than the second lens group G2, the lens La that satisfies conditional expression (17) is the positive lens L31, which is located closer to the object than the final lens group GL.

[0143] The values ​​of the specifications of the variable magnification optical system according to Example 3 are listed in Table 3 below. Note that the data for [Lens specifications] does not include the filter FL, and TL (total length of the variable magnification optical system) and BF (back focus) in [Overall specifications] indicate air-equivalent distances.

[0144] (Table 3) [Overall specifications] Magnification ratio = 3.19 dg1 = 9.39 dg2 = 21.44 W M T FNO 4.100 4.101 4.101 2ω 47.203 22.123 16.968 Y 20.3 21.60 21.60 TL 124.758 136.264 158.371 BF 11.858 41.614 46.555 [Lens specifications] Surface number R D nd νd 1 110.087 1.200 1.84666 23.80 2 70.609 8.187 1.75500 52.34 3 1103.816 d1 (variable) 4 404.571 1.200 1.74320 49.26 5* 18.500 13.74 6 -73.983 1.500 1.75500 52.34 7 150.520 0.927 8 68.342 3.938 2.00060 25.45 9 -187.019 d2 (variable) 10 ∞ 1.500 (stop) 11* 20.337 5.928 1.55332 71.68 12 -155.682 0.200 13 52.522 1.200 1.83481 42.73 14 18.022 5.560 1.61800 63.34 15 -364.417 3.498 16 -36.567 1.200 1.81600 46.59 17 16.471 7.602 1.59319 67.90 18 -25.023 d3 (variable) 19 -19.987 2.729 1.80100 34.92 20 -29.306 0.268 21 44.530 6.866 1.59201 67.02 22* -29.087 d4 (can be changed) 23 -115.389 1.200 1.58913 61.25 24* 167.290 d5 (can be changed) 25 -75.976 1.200 1.61800 63.34 26 53.229 BF (can be changed) [Aspherical surface] Surface 5 κ=0.0000,A4=1.29802E-05,A6=3.83971E-08,A8=-2.16742E-10,A10=1.70945E-12,A12=-5.90280E-15,A14=8.65000E-18 Surface 11 κ=1.0000,A4=-7.87897E-06,A6=-1.10557E-08,A8=-6.74840E-12,A10=-1.00151E-13 Surface 22: κ=1.0000,A4=1.94566E-05,A6=-3.94811E-08,A8=,1.95344E-10,A10=-4.33950E-13 Surface 24: κ=1.0000,A4=-2.55762E-08,A6=3.79897E-08,A8=-1.77831E-10,A10=4.30255E-13 [Variable interval date] Infinity focus state Close focus state W M T W M T f 21.000 51.506 67.009 - - - β - - - -0.0812 -0.2051 -0.2548 d1 1.500 9.665 29.904 1.500 9.665 29.904 d2 28.306 3.888 0.809 28.306 3.888 0.809 d3 0.743 7.142 8.050 0.799 4.678 4.338 d4 5.108 0.971 0.287 8.783 3.569 3.937 d5 7.465 3.206 2.988 3.717 3.172 3.017 BF 11.858 41.614 46.555 11.858 41.614 46.555 [Lens Group Data] Group Initial Surface Focal Length G1 1 174.246 G2 4 -34.783 G3 11 38.081 G4 19 40.920 G5 23 -115.730 G6 25 -50.468

[0145] Fig. 10 is a diagram showing various aberrations when the variable magnification optical system of Example 3 is focused at infinity in the wide-angle end state, Fig. 11 is a diagram showing various aberrations when the variable magnification optical system of Example 3 is focused at infinity at a medium focal length, and Fig. 12 is a diagram showing various aberrations when the variable magnification optical system of Example 3 is focused at infinity in the telephoto end state. It can be seen from each aberration diagram that the variable magnification optical system of Example 3 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0146] Fourth Example The fourth example will be described with reference to FIGS. 13 to 16 and Table 4. FIG. 13 shows the lens configuration of a variable magnification optical system according to the fourth example. The variable magnification optical system ZL(4) according to the fourth example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G3 having positive refractive power, and a seventh lens group G7 having negative refractive power. When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the spacing between adjacent lens groups changes. That is, the distances change between the first lens group G1 and the second lens group G2, between the second lens group G2 and the third lens group G3, between the third lens group G3 and the fourth lens group G4, between the fourth lens group G4 and the fifth lens group G5, between the fifth lens group G5 and the sixth lens group G6, and between the sixth lens group G6 and the seventh lens group G7. An aperture diaphragm S is disposed between the second lens group G2 and the third lens group G3, and moves along the optical axis together with the third lens group G3 during zooming. When focusing from an object at infinity to a close object, the sixth lens group G6 moves toward the object along the optical axis.

[0147] The first lens group G1 is composed of a cemented lens formed by cementing together a negative meniscus lens L11 with its convex surface facing the object side and a positive meniscus lens L12 with its convex surface facing the object side, which are arranged in order from the object side along the optical axis.

[0148] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L21 with its convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a biconcave negative lens L24. The image-side lens surface of the negative lens L21 is aspheric.

[0149] The third lens group G3 is composed of a meniscus-shaped positive lens L31 with its convex surface facing the object side. The object-side lens surface of the positive lens L31 is aspheric. A diaphragm S is disposed on the object side of the third lens group G3.

[0150] The fourth lens group G4 is composed of a cemented lens in which a biconvex positive lens L41 and a meniscus negative lens L42 with a concave surface facing the object side are cemented together, in order from the object side along the optical axis.

[0151] The fifth lens group G5 is composed of a cemented lens, in which a negative meniscus lens L51 with its convex surface facing the object side and a positive biconvex lens L52 are cemented together, arranged in order from the object side along the optical axis. The object-side lens surface of the negative lens L51 is aspherical.

[0152] The sixth lens group G6 is composed of a biconvex positive lens L61. The image-side lens surface of the positive lens L61 is aspherical. When focusing from an object at infinity to an object at a close distance, the sixth lens group G6 moves toward the object.

[0153] The seventh lens group G7 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L71 with its convex surface facing the object side, a biconvex positive lens L72, and a biconcave negative lens L73. The object-side lens surface of the positive lens L72 is aspheric. An image plane I is located on the image side of the negative lens L73.

[0154] In this embodiment, the seventh lens group G7 constitutes the final lens group GL, and the sixth lens group G6 constitutes the image-side positive lens group GpB. In addition, among the lens groups located closer to the image side than the second lens group G2, the lenses La that satisfy conditional expression (17) are the positive lens L41 and the positive lens L52, and are located closer to the object side than the final lens group GL.

[0155] The values ​​of the specifications of the variable magnification optical system according to Example 4 are listed below in Table 4. Note that the data for [Lens specifications] does not include the filter FL, and TL (total length of the variable magnification optical system) and BF (back focus) in [Overall specifications] indicate air-equivalent distances.

[0156] (Table 4) [Overall specifications] Magnification ratio = 3.19 dg1 = 5.88 dg2 = 20.60 W M T FNO 3.997 3.998 4.039 2ω 51.072 22.774 17.177 Y 20.6 21.60 21.60 TL 127.478 153.567 169.746 BF 22.937 51.855 66.002 [Lens specifications] Surface number R D nd νd 1 169.601 1.200 1.84666 23.80 2 128.117 4.676 1.77250 49.62 3 6573.800 d1 (variable) 4 941.038 1.200 1.74389 49.53 5* 16.708 9.504 6 -245.551 1.200 1.81788 45.22 7 68.680 0.200 8 32.915 5.887 1.77275 26.70 9 -314.267 1.407 10 -126.268 1.200 1.59349 67.00 11 143.324 d2 (variable) 12 ∞ 2.000 (stop) 13* 33.238 3.161 1.85108 40.12 14 79.521 d3 (variable) 15 39.906 5.727 1.49782 82.57 16 -33.006 1.200 1.89509 38.38 17 -1197.476 d4 (variable) 18* 55.212 1.200 2.00090 29.13 19 18.750 6.604 1.55032 75.50 20 -131.793 d5 (can be changed) 21 34.795 6.765 1.86580 40.09 22* -39.748 d6 (can be changed) 23 86.003 1.200 1.87997 40.87 24 31.707 2.765 25* 84.682 3.504 1.80301 25.53 26 -47.909 0.200 27 -88.171 1.200 1.94962 32.91 28 25.742 BF (can be changed) [Aspherical surface] Surface 5 κ=0.0000, A4=1.72072E-05, A6=1.69790E-08, A8=-7.09327E-12, A10=1.60910E-13 Surface 13 κ=1.0000, A4=-2.52370E-06, A6=-1.36591E-08, A8=3.57785E-11, A10=-2.23174E-13 Surface 18 κ=1.0000, A4=-2.91477E-06, A6=1.48649E-08, A8=1.42849E-11, A10=7.69334E-14 Surface 22: κ=1.0000,A4=1.40921E-05,A6=-2.64615E-08,A8=5.85752E-11,A10=-8.01156E-14 Surface 25: κ=1.0000,A4=-8.23763E-06,A6=-3.26087E-08,A8=3.26381E-11,A10=-2.04009E-13 [Variable interval date] Infinity focus state Close focus state W M T W M T f 18.499 48.995 66.992 - - - β - - - -0.0969 -0.2584 -0.3681 d1 1.000 27.485 36.456 1.000 27.485 36.456 d2 26.528 4.663 1.455 26.528 4.663 1.455 d3 2.182 2.210 0.200 2.182 2.210 0.200 d4 9.354 0.933 0.200 9.354 0.933 0.200 d5 0.680 2.694 2.034 0.229 1.402 0.200 d6 2.796 1.727 1.400 3.248 3.019 3.234 BF 22.937 51.855 66.002 22.937 51.855 66.002 [Lens Group Data] Group Initial Surface Focal Length G1 1 232.594 G2 4 -23.918 G3 13 65.059 G4 15 580.092 G5 18 -708.794 G6 21 22.371 G7 23 -24.988

[0157] Fig. 14 is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focused on infinity in the wide-angle end state, Fig. 15 is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focused on infinity at a medium focal length, and Fig. 16 is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focused on infinity in the telephoto end state. It can be seen from each aberration diagram that the variable magnification optical system of Example 4 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0158] Fifth Example A fifth example will be described with reference to FIGS. 17 to 20 and Table 5. FIG. 17 shows the lens configuration of a variable magnification optical system according to the fifth example. The variable magnification optical system ZL(5) according to the fifth example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, and a seventh lens group G7 having negative refractive power. When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the spacing between adjacent lens groups changes. That is, the distances change between the first lens group G1 and the second lens group G2, between the second lens group G2 and the third lens group G3, between the third lens group G3 and the fourth lens group G4, between the fourth lens group G4 and the fifth lens group G5, between the fifth lens group G5 and the sixth lens group G6, and between the sixth lens group G6 and the seventh lens group G7. An aperture stop S is disposed between the second lens group G2 and the third lens group G3, and the aperture stop S moves along the optical axis together with the third lens group G3 during zooming. When focusing from an object at infinity to a close object, the fifth lens group G5 and the sixth lens group G6 move toward the object along the optical axis on different trajectories.

[0159] The first lens group G1 is composed of a cemented lens formed by cementing together a meniscus negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, which are arranged in order from the object side along the optical axis.

[0160] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a meniscus negative lens L21 with its convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a biconcave negative lens L24. The image-side lens surface of the negative lens L21 is aspheric.

[0161] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a meniscus positive lens L31 with its convex surface facing the object side, and a cemented lens formed by cementing together a biconvex positive lens L32 and a biconcave negative lens L33. The object-side lens surface of the positive lens L31 is aspheric. A diaphragm S is disposed on the object side of the third lens group G3.

[0162] The fourth lens group G4 is composed of a cemented lens, in which a negative meniscus lens L41 with its convex surface facing the object side and a positive biconvex lens L42 are cemented together, arranged in order from the object side along the optical axis. The lens surface of the positive lens L42 facing the image plane side is aspheric.

[0163] The fifth lens group G5 is composed of a biconvex positive lens L51. The image-side lens surface of the positive lens L51 is aspherical. When focusing from an object at infinity to an object at close range, the fifth lens group G5 moves toward the object.

[0164] The sixth lens group G6 is composed of a negative meniscus lens L61 with its convex surface facing the object side. When focusing from an object at infinity to an object at a close distance, the sixth lens group G6 moves toward the object side.

[0165] The seventh lens group G7 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L71 and a biconcave negative lens L72. An image plane I is located on the image plane side of the negative lens L72.

[0166] In this embodiment, the seventh lens group G7 constitutes the final lens group GL, and the fifth lens group G5 constitutes the image-side positive lens group GpB. In addition, among the lens groups located closer to the image side than the second lens group G2, the lenses La that satisfy conditional expression (17) are the positive lens L32 and the positive lens L42, and are located closer to the object side than the final lens group GL.

[0167] The values ​​of the specifications of the variable magnification optical system according to Example 5 are listed in Table 5 below. Note that the data for [Lens specifications] does not include the filter FL, and TL (total length of the variable magnification optical system) and BF (back focus) in [Overall specifications] indicate air-equivalent distances.

[0168] (Table 5) [Overall specifications] Magnification ratio = 3.19 dg1 = 7.52 dg2 = 20.90 W M T FNO 4.000 4.000 4.000 2ω 48.180 22.748 16.907 Y 20.60 21.6 21.60 TL 134.116 152.525 169.755 BF 19.734 44.209 51.862 [Lens specifications] Surface number R D nd νd 1 164.920 1.200 1.84666 23.80 2 90.374 6.322 1.77250 49.62 3 -1382.218 d1 (variable) 4 151.771 1.200 1.74389 49.53 5* 17.187 9.264 6 -65.938 1.200 1.70519 53.30 7 86.222 0.200 8 35.433 5.433 1.87281 27.78 9 -114.778 2.398 10 -34.330 1.200 1.59349 67.00 11 371.860 d2 (variable) 12 ∞ 2.000 (stop) 13* 33.190 6.297 1.85108 40.12 14 2015.055 3.350 15 41.144 7.736 1.55032 75.50 16 -17.809 1.200 1.88708 33.93 17 287.919 d3 (variable) 18 33.461 1.200 1.87471 32.66 19 15.944 8.004 1.55032 75.50 20* -130.957 d4 (variable) 21 57.364 6.501 1.85108 40.12 22* -37.929 d5 (variable) 23 179.417 1.200 1.79940 46.85 24 27.580 d6 (variable) 25 48.106 6.378 1.80518 25.45 26 -31.622 0.280 27 -35.642 1.200 1.93929 33.85 28 31.976 BF (variable) [Aspheric data] Surface 5 κ=0.0000,A4=1.93031E-05,A6=2.90532E-08,A8=-3.02299E-12,A10=2.90219E-13 Page 13 κ=1.0000,A4=2.38661E-06,A6=1.26121E-08,A8=-5.90319E-12,A10=1.64506E-13 20th side κ=1.0000,A4=2.38347E-05,A6=-1.96150E-08,A8=9.34023E-11,A10=-3.86048E-13 Page 22 κ=1.0000,A4=3.13829E-06,A6=-5.75224E-10,A8=-4.52054E-11,A10=-1.98362E-14 [Variable interval data] Infinity focus state Close focus state W M T W M T f 20.500 49.000 67.000 - - - β - - - -0.1057 -0.2494 -0.3378 d1 1.000 19.543 32.283 1.000 19.543 32.283 d2 24.932 6.650 2.800 24.932 6.650 2.800 d3 9.236 1.687 0.200 9.236 1.687 0.200 d4 1.264 1.469 1.000 1.631 2.092 1.872 d5 0.200 0.176 0.368 1.325 2.329 3.349 d6 3.983 5.025 7.474 2.492 2.249 3.622 BF 19.734 44.209 51.862 19.734 44.209 51.862 [Lens group data] Group Initial surface Focal length G1 1 205.579 G2 4 -21.198 G3 13 45.131 G4 18 98.663 G5 21 27.696 G6 23 -40.911 G7 25 -92.510.

[0169] Fig. 18 is a diagram showing various aberrations when the variable magnification optical system of Example 5 is focused at infinity in the wide-angle end state, Fig. 19 is a diagram showing various aberrations when the variable magnification optical system of Example 5 is focused at infinity at a medium focal length, and Fig. 20 is a diagram showing various aberrations when the variable magnification optical system of Example 5 is focused at infinity in the telephoto end state. It can be seen from each of the aberration diagrams that the variable magnification optical system of Example 5 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0170] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below, which summarizes the values ​​corresponding to each of the conditional expressions (1) to (19) for all the examples (Examples 1 to 5). Conditional expression (1) 2.00<f1 / (-fL)<20.00 Conditional expression (2) 8.00<f1 / fw<20.00 Conditional expression (3) 0.50<Bfw / fw<1.40 Conditional expression (4) 80.0°<2ωw Conditional expression (4-1) 80.0°<2ωw<110.0° Conditional expression (5) 2.50<f1 / ft<5.00 Conditional expression (6) 0.040<dg1 / TLw<0.080 Conditional expression (7) 2.00<f1 / fpB<15.00 Conditional expression (8) 1.00<(-f2) / fw<2.00 Conditional expression (9) 0.500<f2 / fL<1.200 Conditional expression (10) 0.70<f3 / (-fL)<3.00 Conditional Expression (11) 4.00<f1 / (-f2)<14.00 Conditional Expression (12) 3.00<f1 / f3<6.00 Conditional Expression (13) 0.15<(-f2) / f3<1.20 Conditional Expression (14) 0.70<f3 / fpB<3.00 Conditional Expression (15) 0.07<f3 / f4<0.40 Conditional Expression (16) 0.20<dg1 / dg2<0.50 Conditional Expression (17) 70.00<νd Conditional Expression (18) 2.80<ft / fw<4.50 Conditional Expression (19) 30.0°<2ωt<50.0°

[0171] [Conditional Expression Corresponding Values] (Examples 1 to 5) Conditional Expression Example 1 Example 2 Example 3 Example 4 Example 5 (1) 13.558 10.095 3.453 10.397 5.025 (2) 16.464 12.549 8.297 12.573 10.028 (3) 0.964 1.065 0.585 1.268 0.989 (4), (4-1) 102.52 102.10 94.41 102.14 96.36 (5) 4.440 3.962 2.601 3.472 3.068 (6) 0.044 0.056 0.075 0.046 0.056 (7) 12.865 10.723 4.258 10.397 7.423 (8) 1.294 1.313 1.656 1.293 1.034 (9) 1.066 1.056 0.689 1.069 0.518 (10) 2.855 2.404 0.755 2.908 1.103 (11) 12.724 9.558 5.009 9.725 9.698 (12) 4.749 4.200 4.576 3.575 4.555 (13) 0.373 0.439 0.913 0.368 0.470 (14) 2.709 2.553 0.931 2.908 1.629 (15) 0.301 0.194 0.931 0.112 0.457 (16) 0.250 0.403 0.438 0.285 0.360 (17) First embodiment (L32) 82.57, (L42) 75.50 Second embodiment (L32) 82.57, (L42) 82.57 Third embodiment (L31) 71.68 Fourth embodiment (L41) 82.57, (L52) 75.50 Fifth embodiment (L32) 75.50, (L42) 75.50 (18) 3.708 3.168 3.190 3.621 3.268 (19) 33.44 38.12 33.94 34.35 33.81.

[0172] 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.

[0173] The above-described examples are merely illustrative examples of the present invention, and the present invention is not limited to these.

[0174] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the variable magnification optical system of each embodiment.

[0175] Although examples of the variable magnification optical system of each embodiment have been shown with a six-group configuration and a seven-group configuration, the present application is not limited to these, and variable magnification optical systems with other group configurations (e.g., eight groups, nine groups, ten groups, etc.) may also be configured. For example, a variable magnification optical system of each embodiment may have an additional lens or lens group on the most object side or the most image side. 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.

[0176] 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.

[0177] When the lens surface is aspherical, the aspherical surface may be any of a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, and 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.

[0178] The aperture stop is preferably disposed between the second lens group and the third lens group, but it is also possible to use the lens frame to fulfill that role instead of providing a member serving as an aperture stop.

[0179] 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.

[0180] G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group G6 Sixth lens group G7 Seventh lens group I Image plane S Aperture stop FL Filter

Claims

1. a first lens group having a positive refractive power and disposed closest to the object side; and a final lens group having a negative refractive power and disposed closest to the image plane side; the plurality of lens groups includes at least six lens groups; When changing magnification, the spacing between adjacent lens groups changes, A variable magnification optical system that satisfies the following condition: 2.00<f1 / (-fL)<20.00 where f1 is the focal length of the first lens group fL: focal length of the final lens group

2. a first lens group having a positive refractive power and disposed closest to the object side; and a final lens group having a negative refractive power and disposed closest to the image plane side; When changing magnification, the spacing between adjacent lens groups changes, A variable magnification optical system that satisfies the following condition: 8.00<f1 / fw<20.00 0.50<Bfw / fw<1.40 80.0°<2ωw where f1 is the focal length of the first lens group fw: focal length of the variable magnification optical system in the wide-angle end state Bfw: back focus of the variable magnification optical system in the wide-angle end state 2ωw: full angle of view of the variable magnification optical system in the wide-angle end state

3. 2. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 8.00<f1 / fw<20.00 where fw is the focal length of the variable magnification optical system in the wide-angle end state

4. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 2.50<f1 / ft<5.00 where ft is the focal length of the variable magnification optical system in the telephoto end state.

5. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.040<dg1 / TLw<0.080 where dg1 is the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the first lens group closest to the image plane. TLw: total length of the variable magnification optical system in the wide-angle end state

6. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 2.00<f1 / fpB<15.00 where fpB is the focal length of the image-side positive lens group that is disposed closest to the image side among the lens groups having positive refractive power that are included in the plurality of lens groups.

7. 3. The variable magnification optical system according to claim 1, wherein the plurality of lens groups include, arranged in order from the object side along the optical axis, the first lens group, a second lens group having negative refractive power, and a third lens group having positive refractive power.

8. 8. The variable magnification optical system according to claim 7, which satisfies the following condition: 1.00<(-f2) / fw<2.00 where f2 is the focal length of the second lens group

9. 8. The variable magnification optical system according to claim 7, which satisfies the following condition: 0.500<f2 / fL<1.200 where f2 is the focal length of the second lens group

10. 8. The variable magnification optical system according to claim 7, which satisfies the following condition: 0.70<f3 / (-fL)<3.00 where f3 is the focal length of the third lens group

11. 8. The variable magnification optical system according to claim 7, which satisfies the following condition: 4.00<f1 / (-f2)<14.00 where f2 is the focal length of the second lens group

12. 8. The variable magnification optical system according to claim 7, which satisfies the following condition: 3.00<f1 / f3<6.00 where f3 is the focal length of the third lens group

13. 8. The variable magnification optical system according to claim 7, which satisfies the following condition: 0.15<(-f2) / f3<1.20 where f2 is the focal length of the second lens group f3: focal length of the third lens group

14. 8. The variable magnification optical system according to claim 7, which satisfies the following condition: 0.70<f3 / fpB<3.00 where f3 is the focal length of the third lens group fpB: focal length of the image-side positive lens group that is located closest to the image plane among the lens groups having positive refractive power included in the plurality of lens groups

15. 8. A variable magnification optical system according to claim 7, further comprising a fourth lens group disposed adjacent to the third lens group on the image plane side thereof, and satisfying the following condition: 0.07<f3 / f4<0.40 where f3 is the focal length of the third lens group f4: focal length of the fourth lens group

16. 8. The variable magnification optical system according to claim 7, which satisfies the following condition: 0.20<dg1 / dg2<0.50 where dg1 is the distance on the optical axis from the lens surface of the first lens group closest to the object to the lens surface of the first lens group closest to the image plane. dg2: the distance on the optical axis from the lens surface of the second lens group closest to the object to the lens surface of the second lens group closest to the image plane

17. 8. The variable magnification optical system according to claim 7, wherein the lens group arranged closer to the image plane than the second lens group includes at least one lens that satisfies the following conditional expression: 1 / (f / f<1 / f)<f / f<1 / f) 1 / ( ... 70.00<νd where νd is the Abbe number of the lens based on the d line.

18. 3. The variable magnification optical system according to claim 1, comprising, arranged along the optical axis in order from the object side, the first lens group, a second lens group having negative refractive power, a plurality of lens groups having positive refractive power, and a plurality of lens groups having negative refractive power arranged successively including the final lens group.

19. 19. The variable magnification optical system according to claim 18, wherein the plurality of lens groups each having a positive refractive power are made up of three lens groups each having a positive refractive power.

20. 3. A variable magnification optical system according to claim 1, wherein the lens group arranged adjacent to the final lens group on the object side moves during focusing.

21. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 2.80<ft / fw<4.50 where fw is the focal length of the variable magnification optical system in the wide-angle end state ft: focal length of the variable magnification optical system in the telephoto end state

22. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 80.0°<2ωw<110.0° where 2ωw is the total angle of view of the variable magnification optical system in the wide-angle end state.

23. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 30.0°<2ωt<50.0° where 2ωt is the total angle of view of the variable magnification optical system in the telephoto end state.

24. 3. An optical instrument comprising the variable magnification optical system according to claim 1.

25. a first lens group having a positive refractive power and disposed closest to the object side; and a final lens group having a negative refractive power and disposed closest to the image plane side; the plurality of lens groups includes at least six lens groups; When changing magnification, the spacing between adjacent lens groups changes, A method for manufacturing a variable magnification optical system, comprising the step of arranging lenses in a lens barrel so as to satisfy the following conditional expression: 2.00<f1 / (-fL)<20.00 where f1 is the focal length of the first lens group fL: focal length of the final lens group