Variable magnification optical system and optical equipment

Abstract

To provide a zoom optical system which allows for reducing the weight of a focusing lens group to suppress aberration variations while focusing.SOLUTION: A zoom optical system ZL (1) comprises multiple lens groups G1-G7. Distances between each pair of adjacent lens groups change while zooming. The multiple lens groups comprise a first focusing lens group G5 configured to move while focusing, and a second focusing lens group G6 disposed on the image plane side of the first focusing lens group and configured to move on a trajectory different from that of the first focusing lens group while focusing. Both the first focusing lens group and the second focusing lens group have negative refractive power. The first focusing lens group or the second focusing lens group comprises at least one lens with positive refractive power, and is configured to satisfy the following conditional expression: 1.40<fFP / (-fFN)<3.50, where fFP represents a focal length of a lens with greatest positive refractive power in the first focusing lens group or the second focusing lens group, and fFN represents a focal length of a lens with greatest negative refractive power in the first focusing lens group or the second focusing lens group.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, variable magnification optical systems suitable for photo cameras, electronic still cameras, video cameras, etc. have been proposed (see, for example, Patent Document 1). In variable magnification optical systems, there is a demand for reducing the weight of the focusing lens group and suppressing fluctuations in aberration during focusing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-160944 A Summary of the Invention

[0004] The present invention proposes a variable power optical system described below and an optical device equipped with the variable power optical system. The variable power optical system of the present invention has a plurality of lens groups and an aperture stop, and the distance between adjacent lens groups of the plurality of lens groups changes during variable power. The plurality of lens groups include a first focusing lens group that moves during focusing, and a second focusing lens group that is disposed closer to the image surface than the first focusing lens group and moves on a different trajectory from the first focusing lens group during focusing. Both the first focusing lens group and the second focusing lens group have negative refractive power. The first focusing lens group is disposed closer to the image surface than the aperture stop. The first focusing lens group or the second focusing lens group includes at least one lens having positive refractive power and is configured to satisfy the following conditional expression. 1.40 <fFP / (-fFN)<3.50 1.05<βWF2<1.80 however, fFP: The focal length of the lens with the strongest positive refractive power among the lenses constituting the first and second focusing lens groups. fFN: focal length of the lens with the strongest negative refractive power in the first or second focusing lens group βWF2: lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state [Brief description of the drawings]

[0005] [Figure 1] FIG. 2 is a diagram showing a lens configuration in a first example of a variable magnification optical system. [Diagram 2] 1A, 1B, and 1C are diagrams showing various aberrations of the variable magnification optical system of the first example when focused on infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Diagram 3] 1A, 1B, and 1C are diagrams showing various aberrations of the variable magnification optical system of the first example when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 4] FIG. 4 is a diagram showing a lens configuration in a second embodiment of a variable magnification optical system. [Diagram 5] 13A, 13B and 13C are diagrams showing various aberrations when the variable magnification optical system of the second example is focused on infinity in the wide-angle end state, the intermediate focal length state and the telephoto end state, respectively. [Figure 6] 13A, 13B and 13C are diagrams showing various aberrations of the variable magnification optical system of the second example when focused on a close object in the wide-angle end state, the intermediate focal length state and the telephoto end state, respectively. [Figure 7] FIG. 13 is a diagram showing a lens configuration in a third example of a variable magnification optical system. [Figure 8] 13A, 13B and 13C are diagrams showing various aberrations of the variable magnification optical system of the third example when focused on infinity in the wide-angle end state, the intermediate focal length state and the telephoto end state, respectively. [Figure 9] 13A, 13B and 13C are diagrams showing various aberrations of the variable magnification optical system of the third example when focused on a close object in the wide-angle end state, the intermediate focal length state and the telephoto end state, respectively. [Figure 10] FIG. 13 is a diagram showing a lens configuration in a fourth embodiment of a variable magnification optical system. [Figure 11]13A, 13B and 13C are diagrams showing various aberrations of the variable magnification optical system of the fourth example when focused on infinity in the wide-angle end state, the intermediate focal length state and the telephoto end state, respectively. [Figure 12] 13A, 13B and 13C are diagrams showing various aberrations of the variable magnification optical system of the fourth example when focused on a close object in the wide-angle end state, the intermediate focal length state and the telephoto end state, respectively. [Figure 13] FIG. 13 is a diagram showing a lens configuration in a fifth embodiment of a variable magnification optical system. [Figure 14] 13A, 13B and 13C are diagrams showing various aberrations when the variable magnification optical system of the fifth embodiment is focused on an object at infinity in the wide-angle end state, the intermediate focal length state and the telephoto end state, respectively. [Figure 15] 13A, 13B and 13C are diagrams showing various aberrations of the variable magnification optical system of the fifth example when focused on a close object in the wide-angle end state, the intermediate focal length state and the telephoto end state, respectively. [Figure 16] FIG. 1 is a diagram showing a configuration of a digital camera as an embodiment of an optical device. [Figure 17] 10 is a flowchart showing a method for manufacturing a variable magnification optical system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Preferred embodiments for carrying out the present invention are described below.

[0007] 16 shows a schematic configuration of a digital camera, which is an embodiment of the optical device of the present invention. This camera is composed of a body 1 equipped with an image sensor 3, and a photographing lens 2, which corresponds to an embodiment of the variable magnification optical system of the present invention. Light from an object (subject) (not shown) is collected by the photographing lens 2 and reaches the image sensor 3. As a result, the light from the subject is imaged by the image sensor 3 and recorded in a memory (not shown) as a subject image. Details of the photographing lens 2 will be described below as an embodiment of the variable magnification optical system.

[0008] A variable power optical system according to an embodiment of the present invention has a plurality of lens groups, and the distance between adjacent lens groups changes during variable power. The plurality of lens groups includes a first focusing lens group that moves during focusing, and a second focusing lens group that is disposed closer to the image plane than the first focusing lens group and moves on a different trajectory from the first focusing lens group during focusing. Both the first focusing lens group and the second focusing lens group have negative refractive power. The first focusing lens group or the second focusing lens group includes at least one lens having positive refractive power, and is configured to satisfy the following conditional expression (1). 1.40 <fFP / (-fFN)<3.50 ···(1) however, fFP: The focal length of the lens with the strongest positive refractive power among the lenses constituting the first and second focusing lens groups. fFN: focal length of the lens with the strongest negative refractive power in the first or second focusing lens group

[0009] The above conditional expression (1) defines the ratio between the focal length of the lens with the strongest positive refractive power in the first or second focusing lens group and the focal length of the lens with the strongest negative refractive power in the first or second focusing lens group. By satisfying this conditional expression (1), it is possible to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance.

[0010] If the value of conditional expression (1) exceeds the upper limit of 3.50, the refractive power of the lens with the strongest negative refractive power in the first focusing lens group or the second focusing lens group becomes strong, making it difficult to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance. In order to ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (1) to 3.45. If the upper limit of conditional expression (1) is set to a smaller value, for example, 3.40, 3.30, 3.20, 3.15, 3.10, 3.05, 3.00, 2.95, or 2.90, the effect of this embodiment will be even more certain.

[0011] On the other hand, when the value of condition (1) is below the lower limit of 1.40, the refractive power of the lens with the strongest positive refractive power in the first focusing lens group or the second focusing lens group becomes strong, and the distance from an object at infinity becomes large. Therefore, it becomes difficult to suppress the fluctuation of various aberrations including spherical aberration when focusing on a close object. In order to ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (1) to 1.45. Setting the lower limit of conditional expression (1) to a larger value, for example, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.90, or 2.00, will further ensure the effect of this embodiment.

[0012] The variable magnification optical system configured as described above achieves good aberration correction by changing the spacing between adjacent lens groups when varying the magnification, and by arranging multiple focusing lens groups with refractive power, it is possible to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance, without increasing the size of the focusing lens group.

[0013] It is preferable that the first focusing lens group moves toward the image plane when focusing from an object at infinity to an object at a close distance, which makes it possible to effectively suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance.

[0014] It is preferable that the second focusing lens group moves toward the image plane when focusing from an object at infinity to an object at a close distance, which makes it possible to more effectively suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance.

[0015] It is also preferable that the variable magnification optical system further satisfies the following conditional expression (2). 1.00<(-fFs) / fw<4.00 (2) however, fFs: focal length of the lens group with the stronger refractive power between the first and second focusing lens groups fw: focal length of the variable magnification optical system at the wide-angle end

[0016] Conditional expression (2) specifies the ratio between the focal length of the lens group having the stronger refractive power between the first focusing lens group and the second focusing lens group, and the focal length of the variable magnification optical system in the wide-angle end state. By satisfying this conditional expression (2), it is possible to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance in the wide-angle end state, without increasing the size of the lens barrel.

[0017] If the corresponding value of conditional expression (2) exceeds the upper limit value 4.00, the refractive power of the focusing lens group will be weak, and the amount of movement of the focusing lens group when focusing from an object at infinity to an object at a close distance will be large, resulting in an increase in the size of the lens barrel. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (2) to 3.90. If the upper limit value of conditional expression (2) is set to a smaller value, for example, 3.80, 3.50, 3.30, 3.15, 3.00, 2.80, 2.50, 2.20, or 2.00, the effect of this embodiment will be even more certain.

[0018] On the other hand, if the corresponding value of conditional expression (2) is below the lower limit value 1.00, the refractive power of the focusing lens group becomes strong, and it becomes difficult to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance in the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the lower limit value of conditional expression (2) to 1.10. If the lower limit value of conditional expression (2) is set to a larger value, for example, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, or 1.60, the effect of this embodiment will be even more certain.

[0019] It is also preferable that the variable magnification optical system further satisfies the following conditional expression (3). 0.10 <MWF1 / MWF2<3.00 ···(3) however, MWF1: Absolute value of the movement of the first focusing lens group when focusing from an object at infinity to a close object at the wide-angle end MWF2: Absolute value of the movement of the second focusing lens group when focusing from an object at infinity to a close object in the wide-angle end state

[0020] Conditional expression (3) defines the ratio between the absolute value of the movement amount of the first focusing lens group when focusing from an object at infinity to a close object in the wide-angle end state and the absolute value of the movement amount of the second focusing lens group when focusing from an object at infinity to a close object in the wide-angle end state. By satisfying this conditional expression (3), it is possible to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the wide-angle end state.

[0021] If the corresponding value of conditional expression (3) exceeds the upper limit value 3.00, the movement amount of the first focusing lens group becomes too large, and it becomes difficult to suppress the fluctuation of various aberrations including spherical aberration when focusing from an object at infinity to an object at a close distance in the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (3) to 2.50. If the upper limit value of conditional expression (3) is set to a smaller value, for example, 2.00, 1.75, 1.50, 1.30, 1.15, 1.00, 0.85, 0.80, or 0.75, the effect of this embodiment will be more certain.

[0022] On the other hand, if the corresponding value of conditional expression (3) falls below the lower limit of 0.10, the movement amount of the second focusing lens group becomes too large, making it difficult to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an infinitely distant object to a close object in the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.13, 0.15, 0.18, 0.20, 0.21, or 0.23. If the lower limit of conditional expression (3) is set to a larger value, for example, 0.25, 0.30, 0.35, or 0.38, the effect of this embodiment will be even more certain.

[0023] It is also preferable that the variable magnification optical system further satisfies the following conditional expression (4). 0.20<βWF1 / βWF2<5.00 (4) however, βWF1: Lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state βWF2: Lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state

[0024] Conditional expression (4) defines the ratio of the lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state to the lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state. By satisfying this conditional expression (4), it is possible to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the wide-angle end state.

[0025] If the value of conditional expression (4) exceeds the upper limit of 5.00, the lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state becomes too large, making it difficult to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (4) to 4.80. If the upper limit of conditional expression (4) is set to a smaller value, for example, 4.60, 4.00, 3.50, 3.30, 3.00, 2.50, 2.00, 1.50, or 1.25, the effect of this embodiment will be even more certain.

[0026] On the other hand, if the corresponding value of conditional expression (4) falls below the lower limit of 0.20, the lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state becomes too large, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the wide-angle end state. In order to ensure the effects of this embodiment, the lower limit of conditional expression (4) should be set to 0. It is preferable to set the lower limit of conditional expression (4) to a larger value, for example, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, or 0.75, the effect of this embodiment becomes even more certain.

[0027] It is also preferable that the plurality of lens groups includes a subsequent lens group arranged closer to the image plane than the second focusing lens group, and the subsequent lens group is composed of at least one lens group, which makes it possible to effectively suppress fluctuations in various aberrations including spherical aberration when focusing from an object at infinity to an object at a close distance.

[0028] It is also preferable that the variable magnification optical system further satisfies the following condition (5). -2.00<(-fFs) / fR<2.00 (5) however, fFs: focal length of the lens group with the stronger refractive power between the first and second focusing lens groups fR: focal length of the subsequent lens group

[0029] Conditional expression (5) defines the ratio of the focal length of the lens group having the stronger refractive power between the first and second focusing lens groups to the focal length of the succeeding lens group. By satisfying conditional expression (5), it is possible to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object.

[0030] If the corresponding value of conditional expression (5) exceeds the upper limit value 2.00, the positive refractive power of the subsequent lens group becomes strong, and it becomes difficult to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (5) to 1.90. Furthermore, if the upper limit value of conditional expression (5) is set to a smaller value, for example, 1.80, 1.65, 1.50, 1.35, 1.20, 1.10, 1.10, 0.90, or 0.80, the effect of this embodiment will be even more certain.

[0031] On the other hand, if the corresponding value of conditional expression (5) falls below the lower limit value of -2.00, the negative refractive power of the subsequent lens group becomes strong, making it difficult to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance. In order to ensure the effect of this embodiment, it is preferable to set the lower limit value of conditional expression (5) to -1.90. Furthermore, if the lower limit value of conditional expression (5) is set to a larger value, for example, -1.80, -1.65, -1.50, -1.25, -1.00, -0.75, -0.50, -0.25, or -0.10, the effect of this embodiment will be even more certain.

[0032] It is also preferable that the plurality of lens groups includes a leading lens group arranged closer to the object side than the first focusing lens group, and the leading lens group is composed of at least one lens group, which makes it possible to effectively suppress fluctuations in various aberrations including spherical aberration when changing magnification from the wide-angle end state to the telephoto end state.

[0033] It is also preferable that the variable magnification optical system further satisfies the following condition (6): 0.30<(-fFs) / fF<3.00 (6) however, fFs: focal length of the lens group with the stronger refractive power between the first and second focusing lens groups fF: The first focusing lens in the preceding lens group Lens group The focal length of the lens group adjacent to

[0034] Conditional expression (6) defines the ratio of the focal length of the lens group having the stronger refractive power between the first focusing lens group and the second focusing lens group to the focal length of the preceding lens group. ) is satisfied, it is possible to suppress fluctuations in various aberrations, including spherical aberration, when changing the magnification from the wide-angle end state to the telephoto end state without increasing the size of the lens barrel.

[0035] If the corresponding value of conditional expression (6) exceeds the upper limit value 3.00, the refractive power of the leading lens group becomes strong, and it becomes difficult to suppress the fluctuation of various aberrations, including spherical aberration, when changing the magnification from the wide-angle end state to the telephoto end state. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (6) to 2.90. Furthermore, if the upper limit value of conditional expression (6) is set to a smaller value, for example, 2.80, 2.65, 2.50, 2.30, 2.15, 2.00, 1.90, 1.85, or 1.80, the effect of this embodiment will be even more certain.

[0036] On the other hand, if the corresponding value of conditional expression (6) falls below the lower limit of 0.30, the refractive power of the leading lens group will be weak, and the amount of movement of the leading lens group during zooming from the wide-angle end state to the telephoto end state will be large, resulting in an increase in the size of the lens barrel. In order to ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (6) to 0.40. If the lower limit of conditional expression (6) is set to a larger value, for example, 0.50, 0.70, 0.85, 1.00, 1.10, 1.15, 1.20, 1.25, or 1.30, the effect of this embodiment will be even more certain.

[0037] It is also preferable that the leading lens group has a first lens group having positive refractive power that is disposed closest to the object, which makes it possible to effectively suppress fluctuations in various aberrations, including spherical aberration, when changing magnification from the wide-angle end state to the telephoto end state.

[0038] It is also preferable that the leading lens group has a second lens group having negative refractive power adjacent to the first lens group, which makes it possible to effectively suppress fluctuations in various aberrations, including spherical aberration, when changing magnification from the wide-angle end state to the telephoto end state.

[0039] It is also preferable that the variable magnification optical system further satisfies the following condition (7): 4.00 <f1 / (-f2)<8.00 ···(7) however, f1: focal length of the first lens group f2: focal length of the second lens group

[0040] Conditional expression (7) defines the ratio of the focal length of the first lens group to the focal length of the second lens group. By satisfying conditional expression (7), it is possible to suppress fluctuations in various aberrations, including spherical aberration, when changing magnification from the wide-angle end state to the telephoto end state.

[0041] If the corresponding value of conditional expression (7) exceeds the upper limit value 8.00, the refractive power of the second lens group becomes strong, making it difficult to suppress the fluctuation of various aberrations, including spherical aberration, when changing magnification from the wide-angle end state to the telephoto end state. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (7) to 7.80. If the upper limit value of conditional expression (7) is set to a smaller value, for example, 7.50, 7.25, 7.00, 6.75, 6.50, 6.30, 6.20, 6.10, or 6.00, the effect of this embodiment will be even more certain.

[0042] On the other hand, if the corresponding value of conditional expression (7) is below the lower limit value 4.00, the refractive power of the first lens group becomes strong, making it difficult to suppress the fluctuation of various aberrations, including spherical aberration, when changing magnification from the wide-angle end state to the telephoto end state. In order to ensure the effect of this embodiment, it is preferable to set the lower limit value of conditional expression (7) to 4.20. If the lower limit value of conditional expression (7) is set to a larger value, for example, 4.50, 4.70, 4.85, 5.00, 5.20, 5.40, 5.50, 5.60, or 5.70, the effect of this embodiment will be even more certain.

[0043] Moreover, by adopting the above-mentioned configuration, the variable magnification optical system can be changed from the wide-angle end state to the telephoto end state. It is possible to satisfactorily suppress aberration fluctuations during zooming to and from the zoom lens, while satisfying the following conditional expression (8). 2ωw>75.0° (8) however, ωw: Half angle of view of the variable magnification optical system in the wide-angle end state

[0044] In the above-described configuration, by narrowing the range of values ​​corresponding to each conditional expression, the lower limit of conditional expression (8) can be set to a larger value, for example, 77.0°, 80.0°, 82.0°, or 83.5°.

[0045] It is also preferable that the variable magnification optical system further satisfies the following condition (9). 0.10 <BFw / fw<1.00 ···(9) however, BFw: Air equivalent distance (back focus) of the variable magnification optical system at the wide-angle end fw: focal length of the variable magnification optical system at the wide-angle end

[0046] Condition (9) defines the ratio of the back focus of the variable magnification optical system in the wide-angle end state to the focal length of the variable magnification optical system in the wide-angle end state. By satisfying condition (9), various aberrations including coma in the wide-angle end state can be effectively corrected.

[0047] If the corresponding value of conditional expression (9) exceeds the upper limit value 1.00, the back focus at the wide-angle end state becomes large relative to the focal length at the wide-angle end state, making it difficult to correct various aberrations including coma at the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (9) to 0.90 or 0.85. If the upper limit value of conditional expression (9) is set to a smaller value, for example, 0.80, 0.75, 0.70, 0.65, 0.60, or 0.55, the effect of this embodiment will be even more certain.

[0048] On the other hand, if the corresponding value of conditional expression (9) falls below the lower limit of 0.10, the back focus at the wide-angle end state becomes small relative to the focal length at the wide-angle end state, making it difficult to correct various aberrations, including coma aberration, at the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (9) to 0.15, 0.20, or 0.25. Setting the lower limit of conditional expression (9) to a larger value, for example, 0.30, 0.35, 0.38, 0.40, 0.42, or 0.45, will further ensure the effect of this embodiment.

[0049] Moreover, it is preferable that the second focusing lens group has a lens component having negative refractive power, and that the lens component satisfies the following conditional expression (10). Here, the term "lens component" is used to mean both a single lens and a cemented lens. -2.00<(r2+r1) / (r2-r1)<6.00 ···(10) however, r1: radius of curvature of the lens surface on the object side of the lens component r2: radius of curvature of the lens surface on the image side of the lens component

[0050] Conditional expression (10) defines the shape factor of the lens having negative refractive power in the second focusing lens group. By satisfying conditional expression (10), it is possible to suppress fluctuations in various aberrations, including coma, when focusing from an object at infinity to a close object.

[0051] If the value of conditional expression (10) exceeds the upper limit of 6.00, the second focusing lens group will be insufficient in correcting coma aberration, making it difficult to suppress fluctuations in various aberrations, including coma aberration, when focusing from an object at infinity to an object at a close distance. It is preferable to set the upper limit of condition (10) to 5.50. Furthermore, if the upper limit of condition (10) is set to a smaller value, for example, 5.00, 4.75, 4.50, 4.25, 4.00, 3.70, 3.50, or 3.20, the effect of this embodiment will be more certain.

[0052] On the other hand, if the corresponding value of conditional expression (10) falls below the lower limit value of -2.00, the second focusing lens group will be insufficient in correcting coma aberration, and it will be difficult to suppress the fluctuation of various aberrations, including coma aberration, when focusing from an object at infinity to an object at a close distance. In order to ensure the effect of this embodiment, it is preferable to set the lower limit value of conditional expression (10) to -1.50. If the lower limit value of conditional expression (10) is set to a larger value, for example, -1.00, -0.50, -0.10, -0.05, 0.05, 0.08, 0.12, 0.40, or 0.55, the effect of this embodiment will be even more certain.

[0053] It is also preferable that the variable magnification optical system further satisfies the following condition (11): 1.05<βWF1<1.80 (11) however, βWF1: Lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state

[0054] Conditional expression (11) defines the lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state. By satisfying conditional expression (11), it is possible to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the wide-angle end state.

[0055] If the corresponding value of conditional expression (11) exceeds the upper limit value 1.80, the lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state becomes too large, making it difficult to suppress the fluctuation of various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (11) to 1.75. The effect of this embodiment can be further ensured by setting the upper limit value of conditional expression (11) to a smaller value, for example, 1.70, 1.65, 1.60, 1.58, 1.55, 1.53, 1.50, 1.49, or even 1.48.

[0056] If the value of conditional expression (11) falls below the lower limit of 1.05, the lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state becomes too small, making it difficult to suppress the variation of the spherical aberration, distortion aberration, and coma aberration when focusing from an object at infinity to a close object in the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (11) to 1.06. The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (11) to 1.08, 1.10, 1.12, 1.15, 1.16, 1.20, 1.22, or even 1.25.

[0057] It is also preferable that the variable magnification optical system further satisfies the following condition (12): 1.05<βWF2<1.80 (12) however, βWF2: Lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state

[0058] Conditional expression (12) defines the lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state. By satisfying conditional expression (12), it is possible to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the wide-angle end state.

[0059] If the value of condition (12) exceeds the upper limit of 1.80, the lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state becomes too large. Therefore, it becomes difficult to suppress the fluctuation of various aberrations including spherical aberration when focusing on a close object. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (12) to 1.75. The effect of this embodiment can be further ensured by setting the upper limit value of conditional expression (12) to 1.70, 1.68, 1.65, 1.63, 1.60, 1.58, 1.55, or even 1.54.

[0060] If the value of conditional expression (12) falls below the lower limit of 1.05, the lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state becomes too small, making it difficult to suppress the variation of the spherical aberration, distortion aberration, and coma aberration when focusing from an object at infinity to a close object in the wide-angle end state. In order to ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (12) to 1.08. The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (12) to 1.10, 1.13, 1.15, 1.18, 1.20, 1.23, 1.24, 1.28, or even 1.30.

[0061] It is also preferable that the variable magnification optical system further satisfies the following condition (13): (βWF1+1 / βWF1) -2 <0.250 ···(13) however, βWF1: Lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state

[0062] Conditional expression (13) specifies the condition that the lateral magnification of the first focusing lens group must satisfy when focusing on an object at infinity in the wide-angle end state. By satisfying conditional expression (13), it is possible to reduce the amount of movement of the first focusing lens group while suppressing fluctuations in various aberrations, including spherical aberration, distortion, and coma, when focusing from an object at infinity to a close object in the wide-angle end state.

[0063] If the corresponding value of conditional expression (13) exceeds the upper limit value 0.250, the amount of movement of the first focusing lens group when focusing on an object at infinity in the wide-angle end state becomes too large, which is undesirable. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (13) to 0.249. The effect of this embodiment can be further ensured by setting the upper limit value of conditional expression (13) to 0.248, 0.247, 0.246, or even 0.245.

[0064] It is also preferable that the variable magnification optical system further satisfies the following condition (14): (βWF2+1 / βWF2)-2 <0.250 ···(14) however, βWF2: Lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state

[0065] Conditional expression (14) defines the lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state. By satisfying conditional expression (14), it is possible to reduce the amount of movement of the second focusing lens group while suppressing fluctuations in various aberrations, including spherical aberration, distortion, and coma, when focusing from an object at infinity to a close object in the wide-angle end state.

[0066] If the corresponding value of conditional expression (14) exceeds the upper limit value 0.249, the amount of movement of the second focusing lens group when focusing on an object at infinity in the wide-angle end state becomes too large, which is undesirable. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (14) to 0.248. The effect of this embodiment can be further ensured by setting the upper limit value of conditional expression (14) to 0.245, 0.240, 0.238, 0.235, 0.233, 0.230, 0.228, or even 0.225.

[0067] The optical device described above is equipped with the variable magnification optical system described above, thereby realizing high-speed and quiet autofocus without increasing the size of the lens barrel, and also realizing high-speed and quiet autofocus without increasing the size of the lens barrel. It is possible to effectively suppress aberration fluctuations when zooming to the telephoto end state, as well as aberration fluctuations when focusing from an object at infinity to a close object.

[0068] Next, referring to FIG. 17, a manufacturing method of the variable magnification optical system will be outlined. The variable magnification optical system is manufactured by constructing a plurality of lens groups (ST1) and arranging the constructed lens groups in the lens barrel under the following conditions (ST2). The plurality of lens groups are arranged so that the interval between adjacent lens groups changes during magnification. The lens groups arranged here include a first focusing lens group that moves during focusing, and a second focusing lens group that is arranged closer to the image plane than the first focusing lens group and moves on a different trajectory from the first focusing lens group during focusing. Both the first focusing lens group and the second focusing lens group have negative refractive power. The first focusing lens group or the second focusing lens group includes at least one lens having positive refractive power and is configured to satisfy the above-mentioned conditional expression (1).

[0069] The variable magnification optical system manufactured by the above procedure and an optical device equipped with the variable magnification optical system can achieve high-speed and quiet autofocus without increasing the size of the lens barrel, and can effectively suppress aberration fluctuations when changing magnification from the wide-angle end state to the telephoto end state, as well as aberration fluctuations when focusing from an object at infinity to an object at a close distance. EXAMPLES

[0070] The variable magnification optical system will be described in further detail below by showing five numerical examples, from Example 1 to Example 5. First, how to read the charts and tables referred to in the description of each example will be described.

[0071] 1, 4, 7, 10, and 13 are diagrams showing the lens configuration and operation of the variable magnification optical system in each embodiment. In the center of each figure, the arrangement of the lens group is shown in a cross-sectional view. In the lower part of each figure, the movement locus of the lens group G and the aperture S along the optical axis when zooming (changing magnification) from the wide-angle end state (W) to the telephoto end state (T) is shown by arrows on a two-dimensional plane. The horizontal axis of the two-dimensional plane is the position on the optical axis, and the vertical axis is the state of the variable magnification optical system. In addition, in the upper part of each figure, the movement locus (movement direction and movement amount) of the focusing lens group when focusing from infinity to a close-distance object is shown by arrows together with the characters "focus" and "∞".

[0072] 1, 4, 7, 10, and 13, 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 specification, numbers are assigned to each embodiment to prevent complication due to an increase in the number of symbols. For this reason, the same combination of symbols and numbers may be used in multiple embodiments, but this does not mean that the configurations indicated by the combination of symbols and numbers are the same.

[0073] 2, 5, 8, 11, and 14 are diagrams showing various aberrations of the variable magnification optical system in each embodiment when focusing at infinity, and FIG. 3, 6, 9, 12, and 15 are diagrams showing various aberrations of the variable magnification optical system in each embodiment when focusing at a close distance. In these diagrams, FNO indicates the F-number, NA indicates the numerical aperture, and Y indicates the image height. In the spherical aberration diagrams, the F-number or numerical aperture value corresponding to the maximum aperture is shown, in the astigmatism diagrams and distortion aberration diagrams, the maximum value of the image height is shown, and in the coma aberration diagrams, the value of each image height is shown. d indicates the d-line (λ=587.6 nm), and g indicates the g-line (λ=435.8 nm). In the astigmatism diagrams, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. In the lateral chromatic aberration diagrams, the lateral chromatic aberration based on the g-line is shown.

[0074] Next, the tables used in the explanation of each embodiment will be explained. In the [Overall Specifications] table, f is the focal length of the entire lens system, FNO is the F-number, 2ω is the angle of view (unit is ° (degrees), ω is half angle of view), and Ymax is the maximum image height. TL is the distance from the frontmost lens surface to the last lens surface on the optical axis when focusing at infinity plus BF, and BF is the optical It indicates the air-equivalent distance (back focus) from the last lens surface on the axis to the image plane I. Note that these values ​​are shown for each of the magnification change states: wide-angle end (W), mid-focal length (M), and telephoto end (T).

[0075] In the table of [Overall Specifications], MWF1 indicates the absolute value of the movement amount of the first focusing lens group when focusing from an object at infinity to a close object (the closest object) in the wide-angle end state. MWF2 indicates the absolute value of the movement amount of the second focusing lens group when focusing from an object at infinity to a close object (the closest object) in the wide-angle end state. βWF1 indicates the lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state. βWF2 indicates the lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state.

[0076] In the [Lens specifications] table, the surface numbers indicate the order of the optical surfaces from the object side along the direction of light travel, R is the radius of curvature of each optical surface (surfaces whose center of curvature is on the image surface 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 surface), nd is the refractive index for the d-line of the material of the optical component, and νd is the Abbe number based on the d-line of the material of the optical component. (Aperture S) indicates the aperture stop, and the "∞" in the radius of curvature indicates a flat surface or an aperture. The refractive index of air, nd=1.00000, has been omitted. The lens surface is aspherical If it is a surface, an * is added to the surface number and the paraxial radius of curvature is shown in the radius of curvature R column.

[0077] In the [Aspherical Data] table, the shape of the aspherical surface shown in [Lens Specifications] is shown by the following formula (A). X(y) is the distance (amount of sag) along the optical axis direction from the tangent plane at the apex of the aspherical surface to the position on the aspherical surface at height y, R is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and Ai is the ith aspherical coefficient. "En" is the ratio of "×10 -n For example, 1.234E-05=1.234×10 -5 In addition, the second-order aspheric coefficient A2 is 0, and is omitted. X(y)=(y 2 / R) / {1+(1-κ×y 2 / R 2 ) 1 / 2}+A4×y 4 +A6×y 6 +A8×y 8+A10×y 10 +A12×y 12 (A)

[0078] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0079] The [Variable Distance Data] table shows the surface spacing for the surface numbers that are marked as "variable" in the [Lens Specifications] table. The surface spacing is shown here for each magnification state at the wide-angle end (W), mid-focal length (M), and telephoto end (T) when focused at infinity and close distances.

[0080] The table "Conditional Expression Corresponding Values" shows the values ​​corresponding to each conditional expression.

[0081] In addition, since "mm" is generally used as the unit of length for focal length f, radius of curvature R, surface separation D, and other measurements, the units of length in each table in this specification are also "mm." However, since the same optical performance can be obtained even when proportionally enlarged or reduced, the unit of length is not necessarily limited to "mm."

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

[0083] (First Example) The first embodiment will be described with reference to Figs. 1, 2, 3 and Table 1. Fig. 1 is a diagram showing the lens configuration of a variable magnification optical system according to the first embodiment. The variable magnification optical system ZL(1) according to the first embodiment comprises, in order from the object side, a first lens group G1 having positive refractive power and a second lens group G2 having negative refractive power. The optical system is made up of a second lens group G2 having a first focusing lens group G3, an aperture stop S, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 (first focusing lens group) having negative refractive power, a sixth lens group G6 (second focusing lens group) having negative refractive power, and a seventh lens group G7 having positive refractive power. Here, the first to fourth lens groups G1 to G4 correspond to the leading lens group GF, and the seventh lens group G7 corresponds to the trailing lens group GR. The image surface I is located behind the seventh lens group G7.

[0084] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first to seventh lens groups G1 to G7 move along the locus shown by the arrows in the lower part of Fig. 1, changing the interval between adjacent lens groups and changing magnification. When focusing, the fifth lens group G5 and the sixth lens group G6 move independently (on different loci) in the direction shown by the arrows in the upper part of Fig. 1 (towards the image plane), thereby performing focusing from an object at infinity to an object at a close distance.

[0085] The first lens group G1 is composed of, arranged in order from the object side, a cemented negative lens made of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side, and a positive meniscus lens L13 with a convex surface facing the object side.

[0086] The second lens group G2 is composed of, arranged in order from the object side, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a positive meniscus lens L23 with a convex surface facing the object side, and a negative meniscus lens L24 with a concave surface facing the object side. The surface facing the object side of the negative meniscus lens L21 is aspheric.

[0087] The third lens group G3 is composed of, in order from the object side, a biconvex positive lens L31 and a cemented negative lens consisting of a biconvex positive lens L32 and a biconcave negative lens L33.

[0088] The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens L41, a cemented negative lens consisting of a biconcave negative lens L42 and a biconvex positive lens L43, and a biconvex positive lens L44. The positive lens L41 has an aspheric surface on the object side. The positive lens L44 has an aspheric surface on the image side.

[0089] The fifth lens group G5 is composed of, arranged in order from the object side, a biconvex positive lens L51 and a biconcave negative lens L52.

[0090] The sixth lens group G6 is composed of a biconcave negative lens L61, the object-side surface of which is aspheric.

[0091] The seventh lens group G7 is composed of a biconvex positive lens L71.

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

[0093] (Table 1) [Overall specifications] Magnification ratio=2.74 fFP=53.823(L51) fFN=-26.346(L52) MWF1=0.255 MWF2=0.618 βWF1=1.418 βWF2=1.530 WMT f 24.8 50.0 67.9 FNO 2.92 2.92 2.92 2ω 85.14 45.20 34.12 Ymax 21.60 21.60 21.60 TL 135.45 153.76 169.45 BF 13.08 25.53 33.89 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 11820.3050 2.500 1.84666 23.80 2 254.8436 3.832 1.59319 67.90 3 1938.9860 0.200 4 81.3609 6.634 1.81600 46.59 5 717.8392 D5(variable) 6* 170.2224 2.000 1.67798 54.89 7 19.0228 8.030 8 -102.7918 1.200 1.59319 67.90 9 39.9274 0.200 10 30.7705 3.844 1.85000 27.03 11 120.7450 4.556 12 -26.6990 1.200 1.60300 65.44 13 -48.1940 D13(variable) 14 (Aperture S) ∞ 1.500 15 51.8883 3.971 1.90265 35.73 16 -335.1012 0.200 17 34.2757 7.394 1.49782 82.57 18 -32.4829 1.300 1.81600 46.59 19 124.5969 D19(variable) 20* 73.3752 4.605 1.82098 42.50 21 -40.9497 0.222 22 -60.6253 1.200 1.85478 24.80 23 23.2350 6.747 1.49782 82.57 24 -68.9735 0.930 25 51.1526 5.532 1.80604 40.74 26* -59.8674 D26(variable) 27 364.3227 3.545 1.94595 17.98 28 -58.9057 0.200 29 -87.4737 1.200 1.77250 49.62 30 26.6831 D30(variable) 31* -54.3769 1.300 1.95150 29.83 32 226.2913 D32(variable) 33 84.9939 5.357 1.83481 42.73 34 -133.1562 BF Image plane ∞ [Aspheric data] Side 6 K=1.0000 A4=2.79734E-06, A6=-1.48626E-09, A8=2.33651E-12, A10=-3.91747E-17 Page 20 K=1.0000 A4=-1.24053E-05, A6=2.41375E-10, A8=1.23614E-11, A10=-2.66251E-14 Page 26 K=1.0000 A4=1.94712E-06, A6=-7.52657E-09, A8=-2.53945E-12, A10=9.10643E-15 Page 31 K=1.0000 A4=-5.72467E-06, A6=-2.85790E-08, A8=9.21679E-11, A10=-4.86764E-13 [Lens group data] Group starting plane focal length 1 1 129.519 2 6 -21.862 3 14 47.382 4 20 28.141 5 27 -53.501 6 31 -45.973 7 33 62.847 [Variable interval data] WMTWMT Infinity Infinity Infinity Short distance Short distance Short distance D5 2.000 20.511 30.687 2.000 20.511 30.687 D13 18.977 5.779 2.000 18.977 5.779 2.000 D19 9.078 3.248 2.000 9.078 3.248 2.000 D26 2.614 2.197 2.001 2.869 2.555 2.431 D30 7.108 7.282 6.363 7.472 7.442 6.438 D32 3.198 9.812 13.117 2.579 9.294 12.612 [Conditional formula corresponding value] Conditional formula (1) fFP / (-fFN) = 2.043 Conditional formula (2) (-fFs) / fw = 1.857 Conditional formula (3) MWF1 / MWF2 = 0.412 Conditional formula (4) βWF1 / βWF2 = 0.927 Conditional formula (5) (-fFs) / fR = 0.732 Conditional formula (6) (-fFs) / fF = 1.634 Conditional formula (7) f1 / (-f2) = 5.924 Conditional formula (8) 2ωw = 85.14 Conditional formula (9) BFw / fw = 0.529 Conditional formula (10) (r2+r1) / (r2-r1) = 0.613 Conditional formula (11) βWF1 = 1.418 Conditional formula (12) βWF2 = 1.530 Conditional formula (13) (βWF1+1 / βWF1) -2 = 0.2218 Conditional formula (14) (βWF2+1 / βWF2) -2 = 0.2097

[0094] Fig. 2 shows various aberrations of the variable magnification optical system of Example 1 when focusing on infinity in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C). Fig. 3 shows various aberration values ​​of the variable magnification optical system of Example 1 when focusing on a close distance in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C).

[0095] It can be seen from each of the aberration diagrams that the variable magnification optical system of Example 1 has excellent imaging performance with excellent correction of aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close objects.

[0096] (Second Example) The second embodiment will be described with reference to FIG. 4, FIG. 5, FIG. 6, and Table 2. FIG. 4 is a diagram showing the lens configuration of the variable magnification optical system according to the second embodiment. The variable magnification optical system ZL(2) according to the second embodiment is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 (first focusing lens group) having negative refractive power, a sixth lens group G6 (second focusing lens group) having negative refractive power, and a seventh lens group G7 having positive refractive power. Here, the first to fourth lens groups G1 to G4 correspond to the leading lens group GF, and the seventh lens group G7 corresponds to the trailing lens group GR. The image surface I is located behind the seventh lens group G7.

[0097] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first to seventh lens groups G1 to G7 move along the locus shown by the arrows in the lower part of Fig. 4, changing the interval between adjacent lens groups and changing magnification. When focusing, the fifth lens group G5 and the sixth lens group G6 move independently (on different loci) in the direction shown by the arrows in the upper part of Fig. 4 (towards the image plane), thereby focusing from a distant object to a close object.

[0098] The first lens group G1 is composed of, arranged in order from the object side, a cemented negative lens made of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side, and a positive meniscus lens L13 with a convex surface facing the object side.

[0099] The second lens group G2 is composed of, arranged in order from the object side, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a positive meniscus lens L23 with a convex surface facing the object side, and a negative meniscus lens L24 with a concave surface facing the object side. The surface facing the object side of the negative meniscus lens L21 is aspheric.

[0100] The third lens group G3 is composed of, in order from the object side, a positive meniscus lens L31 with a convex surface facing the object side, and a cemented negative lens consisting of a biconvex positive lens L32 and a biconcave negative lens L33.

[0101] The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens L41, a cemented negative lens consisting of a biconcave negative lens L42 and a biconvex positive lens L43, and a biconvex positive lens L44. The object side surface of the positive lens L41 is aspheric.

[0102] The fifth lens group G5 is composed of, arranged in order from the object side, a biconvex positive lens L51 and a biconcave negative lens L52.

[0103] The sixth lens group G6 is composed of a negative meniscus lens L61 with a concave surface facing the object side. The negative meniscus lens L61 has an aspheric surface facing the object side.

[0104] The seventh lens group G7 is composed of a biconvex positive lens L71, the object-side surface of which is aspheric.

[0105] (Table 2) [Overall specifications] Magnification ratio=2.74 fFP=61.860(L51) fFN=-26.486(L52) MWF1=0.274 MWF2=0.666 βWF1=1.466 βWF2=1.399 WMT f 24.8 50.0 67.9 FNO 2.92 2.92 2.92 2ω 85.14 45.14 33.98 Ymax 21.60 21.60 21.60 TL 136.45 152.83 166.55 BF 11.75 22.94 28.76 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 11836.0180 2.500 1.84666 23.80 2 263.6060 3.519 1.81600 46.59 3 996.8722 0.200 4 97.5302 5.847 1.81600 46.59 5 894.1609 D5(variable) 6* 469.8262 2.000 1.58887 61.13 7 20.0932 8.459 8 -202.0263 1.200 1.77250 49.62 9 46.2591 0.200 10 32.7348 4.789 1.75520 27.57 11 757.6545 3.868 12 -30.1213 1.200 1.60300 65.44 13 -58.1128 D13(variable) 14 (Aperture S) ∞ 1.500 15 43.9945 3.971 1.90265 35.73 16 1479.7660 0.603 17 33.0299 7.156 1.49782 82.57 18 -34.0457 1.300 1.81600 46.59 19 92.8728 D19(variable) 20* 124.2240 4.029 1.77387 47.25 21 -37.2228 0.200 22 -64.0093 1.200 1.85478 24.80 23 21.9014 6.529 1.59319 67.90 24 -90.1349 0.921 25 48.3180 5.294 1.83400 37.18 26 -66.0132 D26(variable) 27 -1051.5067 3.250 1.94595 17.98 28 -55.5153 0.431 29 -85.9904 1.200 1.69680 55.52 30 23.6335 D30(variable) 31* -49.1357 1.300 1.95150 29.83 32 -2454.5649 D32(variable) 33* 121.4403 4.780 1.88202 37.22 34 -126.7893 BF Image plane ∞ [Aspheric data] Side 6 K=1.0000 A4=3.12101E-06, A6=-1.77766E-09, A8=2.07046E-12, A10=-3.82388E-16 Page 20 K=1.0000 A4=-1.59181E-05, A6=-3.41748E-10, A8=5.24280E-11, A10=-1.12143E-13 Page 31 K=1.0000 A4=-8.64573E-06, A6=-1.85220E-08, A8=3.17657E-11, A10=-2.40014E-13 Page 33 K=1.0000 A4=1.15695E-06, A6=7.52900E-10, A8=-4.19329E-12, A10=4.10233E-15 [Lens group data] Group starting plane focal length 1 1 151.194 2 6 -25.501 3 14 49.576 4 20 27.755 5 27 -47.512 6 31 -52.709 7 33 70.966 [Variable interval data] WMT Infinity Infinity Infinity Close distance Close distance Close distance D5 2.000 21.966 33.591 2.000 21.966 33.591 D13 23.054 7.122 2.000 23.054 7.122 2.000 D19 8.670 3.016 2.000 8.670 3.016 2.000 D26 2.760 2.196 2.542 3.034 2.530 2.948 D30 7.661 8.136 7.640 8.053 8.378 7.816 D32 3.109 10.012 12.574 2.444 9.436 11.991 [Conditional expression corresponding value] Conditional expression (1) fFP / (-fFN) = 2.336 Conditional expression (2) (-fFs) / fw = 1.920 Conditional expression (3) MWF1 / MWF2 = 0.412 Conditional expression (4) βWF1 / βWF2 = 1.048 Conditional expression (5) (-fFs) / fR = 0.670 Conditional expression (6) (-fFs) / fF = 1.712 Conditional expression (7) f1 / (-f2) = 5.929 Conditional expression (8) 2ωw = 85.14 Conditional expression (9) BFw / fw = 0.475 Conditional expression (10) (r2+r1) / (r2-r1) = 1.041 Conditional expression (11) βWF1 = 1.466 Conditional expression (12) βWF2 = 1.399 Conditional expression (13) (βWF1+1 / βWF1) -2 = 0.2167 Conditional expression (14) (βWF2+1 / βWF2) -2 = 0.2238

[0106] Fig. 5 shows various aberrations of the variable magnification optical system of Example 2 when focusing on infinity in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C). Fig. 6 shows various aberration values ​​of the variable magnification optical system of Example 2 when focusing on a close distance in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C).

[0107] From the various aberration diagrams, the variable magnification optical system according to the second embodiment has the following characteristics: It can be seen that the lens has excellent imaging performance with excellent correction of various aberrations, and also has excellent imaging performance when focusing on close objects.

[0108] (Third Example) The third embodiment will be described with reference to FIG. 7, FIG. 8, FIG. 9, and Table 3. FIG. 7 is a diagram showing the lens configuration of the variable magnification optical system according to the third embodiment. The variable magnification optical system ZL(3) according to the third embodiment is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, a fourth lens group G4 (first focusing lens group) having negative refractive power, a fifth lens group G5 (second focusing lens group) having negative refractive power, and a sixth lens group G6 having positive refractive power. Here, the first to third lens groups G1 to G3 correspond to the leading lens group GF, and the sixth lens group G6 corresponds to the trailing lens group GR. The image surface I is located behind the sixth lens group G6.

[0109] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first to sixth lens groups G1 to G6 move along the locus indicated by the arrows in the lower part of Fig. 7, thereby changing the distance between adjacent lens groups and changing magnification. When focusing, the fourth lens group G4 and the fifth lens group G5 move independently (on different loci) in the direction indicated by the arrows in the upper part of Fig. 7 (towards the image plane), thereby focusing from a distant object to a close object.

[0110] The first lens group G1 is composed of, arranged in order from the object side, a cemented negative lens made of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side, and a positive meniscus lens L13 with a convex surface facing the object side.

[0111] The second lens group G2 is composed of, arranged in order from the object side, a negative meniscus lens L21 with a convex surface facing the object side, a negative meniscus lens L22 with a concave surface facing the object side, a biconvex positive lens L23, and a negative meniscus lens L24 with a concave surface facing the object side. The surface facing the object side of the negative meniscus lens L21 is aspheric.

[0112] The third lens group G3 is composed of, in order from the object side, a biconvex positive lens L31, a cemented negative lens of a biconvex positive lens L32 and a biconcave negative lens L33, a biconvex positive lens L34, a cemented negative lens of a biconcave negative lens L35 and a biconvex positive lens L36, and a biconvex positive lens L37. The positive lens L34 has an aspheric surface on the object side. The positive lens L37 has an aspheric surface on the image side.

[0113] The fourth lens group G4 is composed of, arranged in order from the object side, a positive meniscus lens L41 with a concave surface facing the object side, and a negative meniscus lens L42 with a convex surface facing the object side.

[0114] The fifth lens group G5 is composed of a negative meniscus lens L51 with a concave surface facing the object side. The negative meniscus lens L51 has an aspheric surface facing the object side.

[0115] The sixth lens group G6 is composed of a biconvex positive lens L61.

[0116] Table 3 below lists the values ​​of the specifications of the variable magnification optical system according to the third example.

[0117] (Table 3) [Overall specifications] Magnification ratio=2.74 fFP=119.327(L41) fFN=-43.472(L51) MWF1=0.419 MWF2=0.625 βWF1=1.168 βWF2=1.427 WMT f 24.8 50.0 67.9 FNO 3.50 3.50 3.50 2ω 85.10 45.60 34.40 Ymax 21.60 21.60 21.60 TL 135.45 152.59 169.45 BF 11.75 18.25 23.91 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 800.0000 2.500 1.84666 23.80 2 149.2823 3.000 1.59319 67.90 3 205.0385 0.200 4 75.1891 6.257 1.81600 46.59 5 947.1276 D5(variable) 6* 500.0000 2.000 1.67798 54.89 7 18.8391 14.459 8 -25.1985 1.200 1.59319 67.90 9 -118.4665 0.200 10 97.8539 3.812 1.85000 27.03 11 -61.2035 1.947 12 -28.1128 1.200 1.60300 65.44 13 -45.1446 D13(variable) 14 (Aperture S) ∞ 1.500 15 39.0407 5.431 1.75520 27.57 16 -150.5310 0.200 17 27.2134 6.774 1.49782 82.57 18 -75.8975 1.300 2.00069 25.46 19 65.0385 2.024 20* 112.8457 3.574 1.66755 41.87 21 -42.5203 ​​0.290 22 -65.7387 1.200 1.85478 24.80 23 18.5000 7.483 1.49782 82.57 24 -72.5400 3.463 25 94.8511 5.524 1.72825 28.38 26* -33.9997 D26(variable) 27 -157.1254 2.312 1.94594 17.98 28 -66.1574 0.200 29 77.0731 1.200 1.80400 46.60 30 30.1840 D30(variable) 31* -20.0000 1.300 1.95150 29.83 32 -39.9506 D32(variable) 33 389.0189 2.631 1.84666 23.80 34 -287.6232 BF Image plane ∞ [Aspheric data] Side 6 K=1.0000 A4=9.81697E-06, A6=-1.08680E-08, A8=1.23597E-11, A10=-2.17136E-15 Page 20 K=1.0000 A4=-2.26533E-05, A6=5.36979E-09, A8=1.47314E-11, A10=-1.43415E-14 Page 26 K=1.0000 A4=2.62785E-07, A6=-1.29286E-08, A8=-4.74230E-12, A10=-5.79020E-14 Page 31 K=1.0000 A4=1.10646E-06, A6=-1.33919E-08, A8=2.15561E-11, A10=-5.38428E-13 [Lens group data] Group starting plane focal length 1 1 154.131 2 6 -25.881 3 14 30.388 4 27 -131.942 5 31 -43.472 6 33 195.660 [Variable interval data] W M T W M T Infinity Infinity Infinity Close distance Close distance Close distance D5 2.000 18.585 26.409 2.000 18.585 26.409 D13 22.225 5.535 2.000 22.225 5.535 2.000 D26 2.386 3.229 2.000 2.805 3.825 2.582 D30 10.756 9.234 9.377 10.962 9.079 9.166 D32 3.151 14.573 22.575 2.526 14.132 22.204 [Conditional expression corresponding value] Conditional expression (1) fFP / (-fFN) = 2.745 Conditional expression (2) (-fFs) / fw = 1.756 Conditional expression (3) MWF1 / MWF2 = 0.671 Conditional expression (4) βWF1 / βWF2 = 0.819 Conditional expression (5) (-fFs) / fR = 0.222 Conditional expression (6) (-fFs) / fF = 1.431 Conditional expression (7) f1 / (-f2) = 5.955 Conditional expression (8) 2ωw = 85.10 Conditional expression (9) BFw / fw = 0.475 Conditional expression (10) (r2+r1) / (r2-r1) = 3.005 Conditional expression (11) βWF1 = 1.168 Conditional expression (12) βWF2 = 1.427 Conditional expression (13) (βWF1+1 / βWF1) -2 = 0.2440 Conditional expression (14) (βWF2+1 / βWF2) -2 = 0.2096

[0118] Fig. 8 shows various aberrations of the variable magnification optical system of Example 3 when focusing on infinity in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C). Fig. 9 shows various aberration values ​​of the variable magnification optical system of Example 3 when focusing on a close distance in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C).

[0119] From the various aberration diagrams, the variable magnification optical system according to the third embodiment has the following characteristics: It can be seen that the lens has excellent imaging performance with excellent correction of various aberrations, and also has excellent imaging performance when focusing on close objects.

[0120] (Fourth Example) The fourth embodiment will be described with reference to Figs. 10, 11, 12 and Table 4. Fig. 10 is a diagram showing the lens configuration of the variable magnification optical system according to the fourth embodiment. The variable magnification optical system ZL(4) according to the fourth embodiment is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having negative refractive power, an aperture stop S, a fourth lens group G4 having positive refractive power, a fifth lens group G5 (first focusing lens group) having negative refractive power, a sixth lens group G6 (second focusing lens group) having negative refractive power, and a seventh lens group G7 having positive refractive power. Here, the first to fourth lens groups G1 to G4 correspond to the leading lens group GF, and the seventh lens group G7 corresponds to the trailing lens group GR. The image surface I is located behind the seventh lens group G7.

[0121] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first to seventh lens groups G1 to G7 move along the locus indicated by the arrows in the lower part of Fig. 10, thereby changing the interval between adjacent lens groups and changing magnification. When focusing, the fifth lens group G5 and the sixth lens group G6 move independently (on different loci) in the direction indicated by the arrows in the upper part of Fig. 10 (towards the image plane), thereby performing focusing from a distant object to a close object.

[0122] The first lens group G1 is composed of, arranged in order from the object side, a cemented negative lens made of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side, and a positive meniscus lens L13 with a convex surface facing the object side.

[0123] The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side. The negative meniscus lens L21 has an aspheric surface facing the object side.

[0124] The third lens group G3 is composed of, arranged in order from the object side, a negative meniscus lens L31 with a concave surface facing the object side, a biconvex positive lens L32, and a negative meniscus lens L33 with a concave surface facing the object side.

[0125] The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens L41, a cemented negative lens of a biconvex positive lens L42 and a biconcave negative lens L43, a biconvex positive lens L44, a cemented negative lens of a biconcave negative lens L45 and a biconvex positive lens L46, and a biconvex positive lens L47. The positive lens L44 has an aspheric surface on the object side. The positive lens L47 has an aspheric surface on the image side.

[0126] The fifth lens group G5 is composed of, arranged in order from the object side, a positive meniscus lens L51 with a concave surface facing the object side, and a negative meniscus lens L52 with a convex surface facing the object side.

[0127] The sixth lens group G6 is composed of a negative meniscus lens L61 with a concave surface facing the object side. The negative meniscus lens L61 has an aspheric surface facing the object side.

[0128] The seventh lens group G7 is composed of a biconvex positive lens L71.

[0129] Table 4 below lists the values ​​of the specifications of the variable magnification optical system according to the fourth example.

[0130] (Table 4) [Overall specifications] Magnification ratio=2.74 fFP=104.146(L51) fFN=-39.924(L61) MWF1=0.375 MWF2=0.564 βWF1=1.173 βWF2=1.459 WMT f 24.8 50.0 67.9 FNO 3.50 3.50 3.50 2ω 85.08 45.84 34.44 Ymax 21.60 21.60 21.60 TL 135.43 152.96 169.45 BF 11.75 20.53 22.23 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 800.0000 2.500 1.84666 23.80 2 161.6173 3.000 1.59319 67.90 3 233.4567 0.200 4 88.3647 5.578 1.81600 46.59 5 1494.7667 D5(variable) 6* 500.0000 2.000 1.67798 54.89 7 20.0442 D7(variable) 8 -23.6909 1.200 1.59319 67.90 9 -99.5585 0.200 10 130.0428 3.826 1.85000 27.03 11 -52.3275 1.221 12 -32.7025 1.200 1.60300 65.44 13 -46.7034 D13(variable) 14 (Aperture S) ∞ 1.658 15 42.4477 4.725 1.75520 27.57 16 -240.9219 1.366 17 27.1858 6.996 1.49782 82.57 18 -51.9273 1.300 2.00069 25.46 19 50.0514 2.382 20* 108.1669 2.719 1.66755 41.87 21 -76.2004 0.200 22 -3410.9598 1.200 1.85478 24.80 23 20.2029 7.635 1.49782 82.57 24 -49.1628 1.439 25 149.7679 6.074 1.72825 28.38 26* -30.1914 D26(variable) 27 -162.6654 2.460 1.94594 17.98 28 -61.8074 0.200 29 86.8437 2.035 1.80400 46.60 30 28.2564 D30(variable) 31* -20.2693 1.300 1.95150 29.83 32 -44.8147 D32(variable) 33 15425.4800 2.506 1.84666 23.80 34 -190.6511 BF Image plane ∞ [Aspheric data] Side 6 K=1.0000 A4=7.50942E-06, A6=-6.77248E-09, A8=6.81523E-12, A10=-1.86349E-15 Page 20 K=1.0000 A4=-2.45608E-05, A6=-6.09341E-09, A8=4.23890E-11, A10=-3.30984E-13 Page 26 K=1.0000 A4=-1.46127E-06, A6=-1.78339E-08, A8=1.84178E-11, A10=-1.65357E-13 Page 31 K=1.0000 A4=-1.14793E-07, A6=-2.17369E-08, A8=6.66752E-11, A10=-6.03155E-13 [Lens group data] Group starting plane focal length 1 1 176.909 2 6 -30.851 3 8 -1135.437 4 14 29.673 5 27 -109.998 6 31 -39.925 7 33 222.447 [Variable interval data] WMT Infinity Infinity Infinity Close distance Close distance Close distance D5 2.000 19.897 29.314 2.000 19.897 29.314 D7 17.679 14.397 13.852 17.679 14.397 13.852 D13 20.371 5.813 2.000 20.371 5.813 2.000 D26 4.463 2.867 2.000 4.838 3.299 2.417 D30 8.754 8.749 8.885 8.943 8.714 8.824 D32 3.289 13.586 24.053 2.725 13.189 23.697 [Conditional expression corresponding value] Conditional expression (1) fFP / (-fFN) = 2.609 Conditional expression (2) (-fFs) / fw = 1.613 Conditional expression (3) MWF1 / MWF2 = 0.665 Conditional expression (4) βWF1 / βWF2 = 0.804 Conditional expression (5) (-fFs) / fR = 0.179 Conditional expression (6) (-fFs) / fF = 1.346 Conditional expression (7) f1 / (-f2) = 5.734 Conditional expression (8) 2ωw = 85.08 Conditional expression (9) BFw / fw = 0.475 Conditional expression (10) (r2+r1) / (r2-r1) = 2.652 Conditional expression (11) βWF1 = 1.1727 Conditional expression (12) βWF2 = 1.4585 Conditional expression (13) (βWF1+1 / βWF1) -2 = 0.2438 Conditional expression (14) (βWF2+1 / βWF2) -2 = 0.2175

[0131] FIG. 11 shows various aberrations of the variable magnification optical system according to the fourth embodiment when focused on infinity in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C). 13A and 13B show various aberration values ​​of the variable magnification optical system according to Example 4 when focusing on a close object in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C).

[0132] It can be seen from each of the aberration diagrams that the variable magnification optical system of Example 4 has excellent imaging performance with excellent correction of aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close objects.

[0133] (Fifth Example) The fifth embodiment will be described with reference to Figs. 13, 14, 15 and Table 5. Fig. 13 is a diagram showing the lens configuration of the variable magnification optical system according to the fifth embodiment. The variable magnification optical system ZL(5) according to the fifth embodiment is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 (first focusing lens group) having negative refractive power, a sixth lens group G6 (second focusing lens group) having negative refractive power, a seventh lens group G7 having positive refractive power, and an eighth lens group G8 having positive refractive power. Here, the first to fourth lens groups G1 to G4 correspond to the leading lens group GF, and the seventh lens group G7 and the eighth lens group G8 correspond to the trailing lens group GR. The image plane I is located behind the eighth lens group G8.

[0134] When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first to eighth lens groups G1 to G8 move along the locus indicated by the arrows in the lower part of Fig. 13, thereby changing the interval between adjacent lens groups and changing magnification. When focusing, the fifth lens group G5 and the sixth lens group G6 move independently (on different loci) in the direction indicated by the arrows in the upper part of Fig. 13 (towards the image plane), thereby performing focusing from a distant object to a close object.

[0135] The first lens group G1 is composed of, arranged in order from the object side, a cemented negative lens made of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side, and a positive meniscus lens L13 with a convex surface facing the object side.

[0136] The second lens group G2 is composed of, arranged in order from the object side, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a positive meniscus lens L23 with a convex surface facing the object side, and a negative meniscus lens L24 with a concave surface facing the object side. The surface facing the object side of the negative meniscus lens L21 is aspheric.

[0137] The third lens group G3 is composed of, in order from the object side, a biconvex positive lens L31, and a cemented positive lens of a biconvex positive lens L32 and a biconcave negative lens L33.

[0138] The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens L41, a cemented negative lens consisting of a biconcave negative lens L42 and a biconvex positive lens L43, and a biconvex positive lens L44. The positive lens L41 has an aspheric surface on the object side. The positive lens L44 has an aspheric surface on the image side.

[0139] The fifth lens group G5 is composed of, arranged in order from the object side, a biconvex positive lens L51 and a biconcave negative lens L52.

[0140] The sixth lens group G6 is composed of a biconcave negative lens L61, the object-side surface of which is aspheric.

[0141] The seventh lens group G7 is composed of a biconvex positive lens L71.

[0142] The eighth lens group G8 is composed of a positive meniscus lens L81 with its concave surface facing the object side.

[0143] Table 5 below lists the values ​​of the specifications of the variable magnification optical system according to the fifth example.

[0144] (Table 5) [Overall specifications] Magnification ratio=2.74 fFP=60.229(L51) fFN=-28.641(L52) MWF1=0.201 MWF2=0.694 βWF1=1.405 βWF2=1.534 WMT f 24.8 50.0 67.9 FNO 2.92 2.92 2.92 2ω 85.18 45.24 34.12 Ymax 21.60 21.60 21.60 TL 135.45 154.15 169.45 BF 11.38 23.63 31.35 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 11891.6830 2.500 1.84666 23.80 2 259.8551 3.953 1.59319 67.90 3 4532.4082 0.200 4 82.2793 6.511 1.81600 46.59 5 637.5320 D5(variable) 6* 166.9549 2.000 1.67798 54.89 7 18.9915 7.826 8 -128.0661 1.200 1.59319 67.90 9 39.3297 0.200 10 30.2329 3.805 1.85000 27.03 11 108.1671 4.249 12 -26.7310 1.200 1.60300 65.44 13 -50.1190 D13(variable) 14 (Aperture S) ∞ 1.500 15 52.2117 3.906 1.90265 35.72 16 -426.9813 0.200 17 36.5119 7.383 1.49782 82.57 18 -31.0542 1.300 1.81600 46.59 19 191.2416 D19(variable) 20* 83.3066 4.681 1.82098 42.50 21 -38.9988 0.299 22 -52.7599 1.200 1.85478 24.80 23 26.2315 6.594 1.49782 82.57 24 -62.9470 0.212 25 52.3086 5.490 1.80604 40.74 26* -58.3708 D26(variable) 27 592.1811 3.338 1.94594 17.98 28 -62.8662 0.200 29 -106.8070 1.200 1.77250 49.62 30 28.0432 D30(variable) 31* -84.0436 1.300 1.95150 29.83 32 101.0812 D32(variable) 33 76.7980 4.332 1.83481 42.73 34 -571.5236 D34(variable) 35 -84.4248 2.428 1.67252 26.52 36 -64.1857 BF Image plane ∞ [Aspheric data] Side 6 K=1.0000 A4=2.89860E-06, A6=-1.09792E-09, A8=1.24848E-12, A10=1.65714E-15 Page 20 K=1.0000 A4=-1.21758E-05, A6=2.33795E-10, A8=1.34229E-11, A10=-2.74633E-14 Page 26 K=1.0000 A4=2.89243E-06, A6=-6.52485E-09, A8=1.47471E-14, A10=1.05852E-14 Page 31 K=1.0000 A4=-5.73632E-06, A6=-2.30482E-08, A8=6.15426E-11, A10=-2.77958E-13 [Lens group data] Group starting plane focal length 1 1 130.490 2 6 -21.991 3 14 47.900 4 20 27.873 5 27 -56.211 6 31 -48.064 7 33 81.345 8 35 379.801 [Variable interval data] WMT Infinity Infinity Infinity Close distance Close distance Close distance D5 2.000 20.708 31.055 2.000 20.708 31.055 D13 18.835 5.825 2.000 18.835 5.825 2.000 D19 9.480 3.315 2.000 9.480 3.315 2.000 D26 2.777 2.126 2.000 2.977 2.460 2.419 D30 6.407 6.601 5.787 6.901 6.815 5.893 D32 3.039 10.144 13.339 2.345 9.596 12.814 D34 2.329 2.594 2.721 2.329 2.594 2.721 [Conditional expression corresponding value] Conditional expression (1) fFP / (-fFN) = 2.103 Conditional expression (2) (-fFs) / fw = 1.942 Conditional expression (3) MWF1 / MWF2 = 0.289 Conditional expression (4) βWF1 / βWF2 = 0.916 Conditional expression (5) (-fFs) / fR = 0.702 Conditional expression (6) (-fFs) / fF = 1.724 Conditional expression (7) f1 / (-f2) = 5.934 Conditional expression (8) 2ωw = 85.18 Conditional expression (9) BFw / fw = 0.460 Conditional expression (10) (r2+r1) / (r2-r1) = 0.092 Conditional expression (11) βWF1 = 1.405 Conditional expression (12) βWF2 = 1.534 Conditional expression (13) (βWF1+1 / βWF1) -2 = 0.2232 Conditional expression (14) (βWF2+1 / βWF2) -2 = 0.2093

[0145] Fig. 14 shows various aberrations of the variable magnification optical system of Example 5 when focusing on infinity in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C). Also, Fig. 15 shows various aberration values ​​of the variable magnification optical system of Example 5 when focusing on a close distance in the wide-angle end state (A), the intermediate focal length state (B), and the telephoto end state (C).

[0146] It can be seen from each of the aberration diagrams that the variable magnification optical system of Example 5 has excellent imaging performance with excellent correction of aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close objects.

[0147] According to each of the embodiments described above, by making the focusing lens group small and lightweight, it is possible to achieve high-speed AF and quiet AF without increasing the size of the lens barrel, and further to realize a variable magnification optical system in which aberration fluctuations when changing magnification from the wide-angle end state to the telephoto end state, as well as aberration fluctuations when focusing from an object at infinity to a close object, are effectively suppressed.

[0148] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without impairing the optical performance specified by the claims.

[0149] In addition, while the above embodiments show variable magnification optical systems having six, seven, and eight groups, it is also possible to use variable magnification optical systems having other group configurations (for example, a nine-group configuration in which a lens or lens group is added to the most object side or the most image side of the variable magnification optical system). Here, a lens group refers to a portion having at least one lens separated by an air gap that changes when the magnification is changed.

[0150] In addition, the lens surface of the lens constituting the variable magnification optical system of the present application may be any of spherical, flat, and aspherical. A spherical or flat lens surface has the advantage that lens processing and assembly adjustment are easy, deterioration of optical performance due to errors in lens processing and assembly adjustment can be prevented, and even if the image plane is displaced, deterioration of image performance is small. The aspherical lens surface may be any of an aspherical surface obtained by grinding, a glass molded aspherical surface in which glass is molded into an aspherical shape using a mold, and a composite aspherical surface in which a resin provided on a glass surface is formed into an aspherical shape. In addition, the lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0151] In addition, the lens surfaces of the lenses constituting the variable magnification optical system of the present application may be coated with an anti-reflection coating having a high transmittance over a wide wavelength range, thereby reducing flare and ghosting and achieving high optical performance with high contrast. [Explanation of symbols]

[0152] G1 First lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group G7 7th lens group G8 8th lens group I image plane S aperture stop

Claims

1. The optical system includes a plurality of lens groups and an aperture stop. When the magnification is changed, the intervals between adjacent lens groups change. the plurality of lens groups include a first focusing lens group that moves during focusing, and a second focusing lens group that is disposed closer to an image plane than the first focusing lens group and moves along a different trajectory from that of the first focusing lens group during focusing, the first focusing lens group and the second focusing lens group both have negative refractive power, the first focusing lens group is disposed closer to the image plane than the aperture stop; the first focusing lens group or the second focusing lens group includes at least one lens having a positive refractive power; A variable magnification optical system that satisfies the following condition: 1.40<fFP / (-fFN)<3.50 1.05<βWF2<1.80 however, fFP: focal length of the lens having the strongest positive refractive power among the lenses constituting the first focusing lens group and the second focusing lens group fFN: focal length of the lens with the strongest negative refractive power in the first focusing lens group or the second focusing lens group βWF2: lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state

2. 2. The variable magnification optical system according to claim 1, wherein the first focusing lens group moves in the image plane direction during focusing from an object at infinity to an object at a close distance.

3. 3. A variable magnification optical system according to claim 1, wherein the second focusing lens group moves in a direction toward an image plane when focusing from an object at infinity to an object at a close distance.

4. 4. The variable magnification optical system according to claim 1, which satisfies the following condition: 1.00<(-fFs) / fw<4.00 however, fFs: focal length of the lens group having stronger refractive power between the first focusing lens group and the second focusing lens group fw: focal length of the variable magnification optical system in the wide-angle end state

5. 5. The variable magnification optical system according to claim 1, which satisfies the following condition: 0.10<MWF1 / MWF2<3.00 however, MWF1: Absolute value of the movement amount of the first focusing lens group when focusing from an object at infinity to an object at a close distance in the wide-angle end state MWF2: Absolute value of the movement amount of the second focusing lens group when focusing from an object at infinity to an object at a close distance in the wide-angle end state

6. 6. The variable magnification optical system according to claim 1, which satisfies the following condition: 0.20<βWF1 / βWF2<5.00 however, βWF1: lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state βWF2: lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state

7. The variable magnification optical system according to any one of claims 1 to 6, wherein the plurality of lens groups includes a subsequent lens group arranged closer to the image plane than the second focusing lens group, and the subsequent lens group is composed of at least one lens group.

8. the plurality of lens groups includes a subsequent lens group disposed closer to an image plane than the second focusing lens group, 7. The variable magnification optical system according to claim 1, which satisfies the following condition: -2.00<(-fFs) / fR<2.00 however, fFs: focal length of the lens group having stronger refractive power between the first focusing lens group and the second focusing lens group fR: focal length of the subsequent lens group

9. 9. The variable magnification optical system according to claim 1, wherein the plurality of lens groups includes a leading lens group arranged closer to the object than the first focusing lens group, the leading lens group being composed of at least one lens group.

10. the plurality of lens groups includes a leading lens group disposed closer to the object side than the first focusing lens group, 9. The variable magnification optical system according to claim 1, which satisfies the following condition: 0.30<(-fFs) / fF<3.00 however, fFs: focal length of the lens group having stronger refractive power between the first focusing lens group and the second focusing lens group fF: focal length of the lens group adjacent to the first focusing lens group among the lens groups constituting the preceding lens group

11. the plurality of lens groups includes a leading lens group disposed closer to the object side than the first focusing lens group, 9. The variable magnification optical system according to claim 1, wherein the preceding lens group includes a first lens group having positive refractive power and arranged closest to the object side.

12. the plurality of lens groups includes a leading lens group disposed closer to the object side than the first focusing lens group, the preceding lens group includes a first lens group having a positive refractive power and disposed closest to the object side; 9. The variable magnification optical system according to claim 1, wherein the leading lens group includes a second lens group having negative refractive power and arranged adjacent to the image surface side of the first lens group.

13. the plurality of lens groups include, in order from the object side, a first lens group having positive refractive power and a second lens group having negative refractive power; 13. The variable magnification optical system according to claim 1, which satisfies the following condition: 4.00<f1 / (-f2)<8.00 however, f1: focal length of the first lens group f2: the focal length of the second lens group

14. 14. The variable magnification optical system according to claim 1, which satisfies the following condition: 2ωw>75.0° however, ωw: half angle of view of the variable magnification optical system in the wide-angle end state

15. 15. The variable magnification optical system according to claim 1, which satisfies the following condition: 0.10<BFw / fw<1.00 however, BFw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state

16. 16. The variable magnification optical system according to claim 1, wherein the second focusing lens group has a lens component having a negative refractive power, and the lens component satisfies the following conditional expression: 1<x<1 / ... -2.00<(r2+r1) / (r2-r1)<6.00 however, r1: radius of curvature of the object-side lens surface of the lens component r2: radius of curvature of the lens surface on the image side of the lens component

17. 17. The variable magnification optical system according to claim 1, which satisfies the following condition: 1.05<βWF1<1.80 however, βWF1: lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state

18. A variable magnification optical system according to any one of claims 1 to 17, which satisfies the following conditional expression. (βWF1+1 / βWF1) -2 <0.250 however, βWF1: lateral magnification of the first focusing lens group when focusing on an object at infinity in the wide-angle end state

19. 19. The variable magnification optical system according to claim 1, which satisfies the following condition: (βWF2+1 / βWF2) -2 <0.250 however, βWF2: lateral magnification of the second focusing lens group when focusing on an object at infinity in the wide-angle end state

20. An optical instrument comprising the variable magnification optical system according to any one of claims 1 to 19.

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