Variable magnification optical system and optical apparatus

Abstract

To provide a variable power optical system in which aberration variation during focusing is suppressed.SOLUTION: In order from an object, a front lens group GA having a positive refractive power, a first intermediate lens group GM1 having a negative refractive power, a second intermediate lens group GM2 having a positive refractive power, and a subsequent lens group GR, wherein a distance between adjacent lens groups changes during zooming, and the rear lens group GR is disposed closest to the object, the zoom lens includes a first focusing lens group GF1 that moves along an optical axis during focusing, and at least one other focusing lens group that is disposed closer to an image side than the first focusing lens group GF1 and moves along the optical axis along a trajectory different from that of the first focusing lens group GF1 during focusing. The second intermediate lens group GM2 includes at least one lens group having a positive refractive power. -6.00 fFs / fw 6.00 Here, fFs is a focal length of a focusing lens group having the highest refractive power among the focusing lens groups included in the subsequent lens group GR, and fw is a focal length of the variable magnification optical system ZL in the wide-angle end state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Variable magnification optical systems suitable for photo cameras, electronic still cameras, video cameras, etc. have been proposed (see, for example, Patent Document 1). In such variable magnification optical systems, it is difficult to suppress aberration fluctuations during focusing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-12243 Summary of the Invention

[0004] The variable magnification optical system according to the present invention has, arranged in order from the object side along the optical axis, a front lens group having positive refractive power, a first intermediate lens group having negative refractive power, a second intermediate lens group having positive refractive power, and a subsequent lens group, wherein the spacing between adjacent lens groups changes during variable magnification, and the subsequent lens group includes a first focusing lens group that is located closest to the object side of the subsequent lens group and moves along the optical axis during focusing, and at least one other focusing lens group that is located closer to the image side than the first focusing lens group and moves along the optical axis along a locus different from that of the first focusing lens group during focusing, and the focusing lens group closest to the first focusing lens group among the other focusing lens groups is composed of a single lens component and satisfies the following conditional expression: -6.00 <fFs / fw<6.00 where fFs is the focal length of the focusing lens group having the strongest refractive power among the focusing lens groups included in the subsequent lens group. fw: focal length of the variable magnification optical system in the wide-angle end state

[0005] An optical apparatus according to the present invention is configured to include the variable magnification optical system described above. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is a diagram showing the lens configuration of a variable magnification optical system according to Example 1. [Figure 2] 2A and 2B are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 3] 3A and 3B are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 4] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 2. [Figure 5] 5A and 5B are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 6] 6A and 6B are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 7] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 3. [Figure 8] 8A and 8B are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 9] 9A and 9B are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 10] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 4. [Figure 11] 11A and 11B are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 12] 12A and 12B are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 13]FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 5. [Figure 14] 14A and 14B are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focused on infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 15] 15A and 15B are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 16] FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system according to Example 6. [Figure 17] 17A and 17B are diagrams showing various aberrations of the variable magnification optical system according to Example 6 when focused on infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 18] 18A and 18B are diagrams showing various aberrations of the variable magnification optical system according to Example 6 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 19] FIG. 13 is a diagram showing the lens configuration of a variable magnification optical system according to Example 7. [Figure 20] 20A and 20B are diagrams showing various aberrations of the variable magnification optical system according to Example 7 when focused on infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 21] 21A and 21B are diagrams showing various aberrations of the variable magnification optical system according to Example 7 when focusing on a close distance in the wide-angle end state and the telephoto end state, respectively. [Figure 22] 1 is a diagram showing the configuration of a camera equipped with a variable magnification optical system according to an embodiment of the present invention. [Figure 23] 10 is a flowchart showing a method for manufacturing a variable magnification optical system according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] A preferred embodiment of the present invention will now be described. First, a camera (optical device) equipped with a variable magnification optical system according to this embodiment will be described with reference to FIG. 22. As shown in FIG. 22, this camera 1 is composed of a body 2 and a photographic lens 3 attached to the body 2. The body 2 is equipped with an image sensor 4, a body control unit (not shown) that controls the operation of the digital camera, and an LCD screen 5. The photographic lens 3 is equipped with a variable magnification optical system ZL consisting of multiple lens groups, and a lens position control mechanism (not shown) that controls the position of each lens group. The lens position control mechanism is composed of a sensor that detects the position of the lens groups, a motor that moves the lens groups back and forth along the optical axis, a control circuit that drives the motor, etc.

[0008] Light from the subject is collected by the variable magnification optical system ZL of the photographing lens 3 and reaches the image plane I of the image sensor 4. The light from the subject that reaches the image plane I is photoelectrically converted by the image sensor 4 and recorded as digital image data in a memory (not shown). The digital image data recorded in the memory can be displayed on the LCD screen 5 in response to a user operation. Note that this camera may be a mirrorless camera or a single-lens reflex camera with a quick-return mirror. Also, the variable magnification optical system ZL shown in FIG. 22 is a schematic representation of a variable magnification optical system provided in the photographing lens 3, and the lens configuration of the variable magnification optical system ZL is not limited to this configuration.

[0009] Next, a variable magnification optical system according to this embodiment will be described. As shown in FIG. 1, a variable magnification optical system ZL(1) as an example of a variable magnification optical system (zoom lens) ZL according to this embodiment includes, in order from the object side along the optical axis, a front lens group GA having positive refractive power, a first intermediate lens group GM1 having negative refractive power, a second intermediate lens group GM2 having positive refractive power, and a rear lens group GR. The spacing between adjacent lens groups changes during magnification. The rear lens group GR includes a first focusing lens group GF1, which is located closest to the object side of the rear lens group GR and moves along the optical axis during focusing, and at least one other focusing lens group, which is located closer to the image side than the first focusing lens group GF1 and moves along the optical axis along a different path from that of the first focusing lens group GF1 during focusing. Furthermore, the other focusing lens group closest to the first focusing lens group GF1 is composed of a single lens component.

[0010] With the above-described configuration, the variable-magnification optical system ZL according to this embodiment satisfies the following conditional expression (1). -6.00 <fFs / fw<6.00 ···(1) where fFs is the focal length of the focusing lens group with the strongest refractive power among the focusing lens groups included in the subsequent lens group GR. fw: focal length of variable magnification optical system ZL at wide-angle end

[0011] According to this embodiment, it is possible to obtain a variable magnification optical system with little aberration fluctuation during focusing, and an optical apparatus equipped with this variable magnification optical system. Incidentally, by including multiple focusing lens groups in the subsequent lens group GR, fluctuations in various aberrations, including spherical aberration, during focusing can be suppressed without increasing the size of the focusing lens group. Furthermore, by changing the spacing between adjacent lens groups during magnification, it is possible to perform good aberration correction during magnification.

[0012] The variable magnification optical system ZL according to this embodiment may be the variable magnification optical system ZL(2) shown in Fig. 4, the variable magnification optical system ZL(3) shown in Fig. 7, or the variable magnification optical system ZL(4) shown in Fig. 10. Furthermore, the variable magnification optical system ZL according to this embodiment may be the variable magnification optical system ZL(5) shown in Fig. 13, the variable magnification optical system ZL(6) shown in Fig. 16, or the variable magnification optical system ZL(7) shown in Fig. 19.

[0013] Conditional expression (1) defines the appropriate relationship between the focal length of the focusing lens group with the strongest refractive power among the focusing lens groups included in the subsequent lens group GR and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (1), fluctuations in various aberrations, including spherical aberration, during focusing can be suppressed.

[0014] If the value corresponding to conditional expression (1) exceeds the upper limit, the difference in refractive power between the focusing lens group with the strongest refractive power and the focusing lens group with the weakest refractive power becomes small, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (1) to 5.50, 5.00, 4.80, 4.50, 4.00, or even 3.80.

[0015] If the corresponding value of conditional expression (1) falls below the lower limit, the refractive power of the focusing lens group with the strongest refractive power becomes too strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing.The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (1) to -5.50, -5.00, -4.50, -4.00, -3.50, -3.00, -2.50, -2.00, or even -1.80.

[0016] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (2). 2.00 <f1 / fw<8.00 ···(2) where f1 is the focal length of the front lens group GA

[0017] Conditional expression (2) defines the appropriate relationship between the focal length of the front lens group GA and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (2), fluctuations in various aberrations, including spherical aberration, that occur when magnification is changed can be suppressed without increasing the size of the lens barrel.

[0018] If the value corresponding to conditional expression (2) exceeds the upper limit, the refractive power of the front lens group GA weakens, which increases the amount of movement of the front lens group GA during magnification change and increases the size of the lens barrel. By setting the upper limit of conditional expression (2) to 7.80, 7.50, 7.40, 7.00, 6.50, 6.30, or even 6.00, the effects of this embodiment can be further ensured.

[0019] If the corresponding value of conditional expression (2) falls below the lower limit, the refractive power of the front lens group GA becomes strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during zooming. By setting the lower limit of conditional expression (2) to 2.30, 2.50, 2.80, 3.00, 3.30, 3.50, or even 3.80, the effects of this embodiment can be further ensured.

[0020] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (3). 0.10 <BFw / fw<1.00 ···(3) BFw: back focus of the variable magnification optical system ZL in the wide-angle end state

[0021] Conditional expression (3) defines an appropriate relationship between the back focus of the variable magnification optical system ZL in the wide-angle end state and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (3), various aberrations, including coma in the wide-angle end state, can be effectively corrected.

[0022] If the corresponding value of conditional expression (3) exceeds the upper limit, the back focus of the variable magnification optical system ZL in the wide-angle end state becomes large relative to the focal length of the variable magnification optical system ZL in the wide-angle end state, making it difficult to correct various aberrations such as coma in the wide-angle end state. By setting the upper limit of conditional expression (3) to 0.95, 0.90, 0.85, 0.80, 0.75, 0.70, 0.65, or even 0.60, the effects of this embodiment can be further ensured.

[0023] If the corresponding value of conditional expression (3) falls below the lower limit, the back focus of the variable magnification optical system ZL in the wide-angle end state becomes small relative to the focal length of the variable magnification optical system ZL in the wide-angle end state, making it difficult to correct various aberrations, including coma aberration, in the wide-angle end state. Furthermore, it becomes difficult to arrange the mechanical components of the lens barrel. The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (3) to 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, or even 0.43.

[0024] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (4). 0.20<|fFs| / f1<2.00 (4) where f1 is the focal length of the front lens group GA

[0025] Conditional expression (4) defines an appropriate relationship between the focal length of the focusing lens group with the strongest refractive power among the focusing lens groups included in the rear lens group GR and the focal length of the front lens group GA. By satisfying conditional expression (4), fluctuations in various aberrations, including spherical aberration, during focusing can be suppressed without increasing the size of the lens barrel. In addition, fluctuations in various aberrations, including spherical aberration, during magnification changes can be suppressed without increasing the size of the lens barrel.

[0026] If the value corresponding to conditional expression (4) exceeds the upper limit, the refractive power of the focusing lens group will be weakened, which will increase the amount of movement of the focusing lens group during focusing and result in a larger lens barrel. Furthermore, the refractive power of the front lens group GA will be strong, which will make it difficult to suppress fluctuations in various aberrations, including spherical aberration, during zooming. The effects of this embodiment can be further enhanced by setting the upper limit of conditional expression (4) to 1.80, 1.50, 1.30, 1.00, 0.85, 0.70, 0.65, 0.60, or even 0.58.

[0027] If the value corresponding to conditional expression (4) falls below the lower limit, the refractive power of the focusing lens group becomes strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing. Furthermore, the refractive power of the front lens group GA becomes weak, increasing the amount of movement of the front lens group GA during magnification change, and the lens barrel becomes larger. The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (4) to 0.22, 0.24, 0.25, or even 0.26.

[0028] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (5). 1.50<|fFs| / (-fM1w)<5.00 (5) where fM1w is the focal length of the first intermediate lens group GM1 in the wide-angle end state

[0029] Conditional expression (5) defines an appropriate relationship between the focal length of the focusing lens group with the strongest refractive power among the focusing lens groups included in the subsequent lens group GR and the focal length of the first intermediate lens group GM1 in the maximum wide-angle state. By satisfying conditional expression (5), fluctuations in various aberrations, including spherical aberration, during focusing can be suppressed. Furthermore, various aberrations, including coma in the maximum wide-angle state, can be effectively corrected.

[0030] If the value corresponding to conditional expression (5) exceeds the upper limit, the refractive power of the first intermediate lens group GM1 in the wide-angle end state becomes strong, making it difficult to correct various aberrations such as coma in the wide-angle end state. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (5) to 4.85, 4.70, 4.50, 4.35, 4.25, 3.85, 3.50, 3.00, or even 2.50.

[0031] If the corresponding value of conditional expression (5) falls below the lower limit, the refractive power of the focusing lens group becomes strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing. By setting the lower limit of conditional expression (5) to 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, or even 1.83, the effects of this embodiment can be further ensured.

[0032] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (6). 0.90<|fFs| / fM2w<4.00 (6) where fM2w is the focal length of the second intermediate lens group GM2 in the wide-angle end state.

[0033] Conditional expression (6) defines an appropriate relationship between the focal length of the focusing lens group with the strongest refractive power among the focusing lens groups included in the subsequent lens group GR and the focal length of the second intermediate lens group GM2 in the maximum wide-angle state. By satisfying conditional expression (6), fluctuations in various aberrations, including spherical aberration, during focusing can be suppressed. Furthermore, various aberrations, including coma in the maximum wide-angle state, can be effectively corrected.

[0034] If the value corresponding to conditional expression (6) exceeds the upper limit, the refractive power of the second intermediate lens group GM2 in the wide-angle end state becomes strong, making it difficult to correct various aberrations such as coma in the wide-angle end state. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (6) to 3.80, 3.50, 3.30, 3.00, 2.80, 2.60, 2.00, 1.80, or even 1.50.

[0035] If the corresponding value of conditional expression (6) falls below the lower limit, the refractive power of the focusing lens group becomes strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing. By setting the lower limit of conditional expression (6) to 0.95, 0.98, 1.00, 1.03, or even 1.05, the effects of this embodiment can be made even more certain.

[0036] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (7). 0.20 <f1 / (-fRw)<5.00 ···(7) where f1 is the focal length of the front lens group GA fRw: focal length of the subsequent lens group GR at the wide-angle end

[0037] Conditional expression (7) defines an appropriate relationship between the focal length of the front lens group GA and the focal length of the rear lens group GR at the maximum wide-angle position. By satisfying conditional expression (7), various aberrations, including coma at the maximum wide-angle position, can be effectively corrected without increasing the size of the lens barrel.

[0038] If the value corresponding to conditional expression (7) exceeds the upper limit, the refractive power of the rear lens group GR in the maximum wide-angle state becomes strong, making it difficult to correct various aberrations, including coma in the maximum wide-angle state. Furthermore, the refractive power of the front lens group GA becomes weak, increasing the amount of movement of the front lens group GA during magnification change and increasing the size of the lens barrel. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (7) to 4.50, 4.00, 3.80, 3.50, 3.30, 3.00, 2.80, or even 2.50.

[0039] If the value corresponding to conditional expression (7) falls below the lower limit, the refractive power of the rear lens group GR in the wide-angle end state will be weak, making it difficult to correct various aberrations, including coma in the wide-angle end state. By setting the lower limit of conditional expression (7) to 0.40, 0.50, 0.60, 0.65, 0.68, or even 0.70, the effect of this embodiment can be further ensured.

[0040] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (8). 0.10 <MTF1 / MTF2<3.00 ···(8) However, MTF1: absolute value of the movement amount of the first focusing lens group GF1 when focusing from an object at infinity to an object at a close distance in the telephoto end state MTF2: Absolute value of the amount of movement of the focusing lens group that is closest to the first focusing lens group GF1 among the other focusing lens groups when focusing from an object at infinity to a close object in the telephoto end state

[0041] Conditional expression (8) defines an appropriate relationship between the amount of movement of the first focusing lens group GF1 when focusing from an object at infinity to an object at a close distance in the telephoto end state and the amount of movement of the focusing lens group closest to the first focusing lens group GF1. By satisfying conditional expression (8), 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 in the telephoto end state.

[0042] If the value corresponding to conditional expression (8) exceeds the upper limit, the movement amount of the first focusing lens group GF1 becomes too large when focusing from an object at infinity to an object at a close distance in the telephoto end state, making it difficult to suppress fluctuations in various aberrations including spherical aberration. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (8) to 2.80, 2.50, 2.30, 2.00, 1.80, 1.65, or even 1.50.

[0043] If the value corresponding to conditional expression (8) falls below the lower limit, when focusing from an object at infinity to a close object in the telephoto end state, the amount of movement of the focusing lens group closest to the first focusing lens group GF1 becomes too large, making it difficult to suppress fluctuations in various aberrations including spherical aberration. The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (8) to 0.13, 0.15, 0.18, 0.20, 0.23, or even 0.25.

[0044] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (9). 0.10<βF1w / βF2w<3.00 (9) where βF1w is the combined lateral magnification of the focusing lens group included in the subsequent lens group GR, which is located closer to the object side than the focusing lens group closest to the image side, when focusing on an object at infinity in the wide-angle end state. βF2w: The lateral magnification of the focusing lens group included in the subsequent lens group GR, which is closest to the image side, when focusing on an object at infinity in the wide-angle end state

[0045] Conditional expression (9) defines an appropriate relationship between the lateral magnification of the focusing lens group closest to the image, among the focusing lens groups included in the subsequent lens group GR, when focusing on an object at infinity in the maximum wide-angle state, and the combined lateral magnification of the focusing lens group located closer to the object than the focusing lens group closest to the image, when focusing on an object at infinity in the maximum wide-angle state. Satisfying conditional expression (9) makes it possible to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the maximum wide-angle state.

[0046] If the value corresponding to conditional expression (9) exceeds the upper limit, the combined lateral magnification of the focusing lens group positioned closer to the object than the focusing lens group closest to the image becomes too large when focusing on an object at infinity in the maximum wide-angle state. This makes it difficult to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the maximum wide-angle state. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (9) to 2.80, 2.50, 2.30, 2.00, 1.80, 1.50, 1.30, 1.00, or even 0.90.

[0047] If the value corresponding to conditional expression (9) falls below the lower limit, the lateral magnification of the focusing lens unit closest to the image side when focusing on an object at infinity in the wide-angle end state becomes too large. As a result, it becomes 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. The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (9) to 0.20, 0.35, 0.50, 0.55, 0.58, or even 0.60.

[0048] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (10). 0.10<βF1t / βF2t<3.00 (10) where βF1t is the combined lateral magnification of the focusing lens group included in the subsequent lens group GR, which is located closer to the object side than the focusing lens group closest to the image side, when focusing on an object at infinity in the telephoto end state. βF2t: The lateral magnification of the focusing lens group included in the subsequent lens group GR, which is closest to the image side, when focusing on an object at infinity in the telephoto end state

[0049] Conditional expression (10) defines an appropriate relationship between the lateral magnification of the focusing lens group closest to the image, among the focusing lens groups included in the subsequent lens group GR, when focusing on an object at infinity in the telephoto end state, and the combined lateral magnification of the focusing lens group located closer to the object than the focusing lens group closest to the image, when focusing on an object at infinity in the telephoto end state. Satisfying conditional expression (10) makes it possible to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the telephoto end state.

[0050] If the value corresponding to conditional expression (10) exceeds the upper limit, the combined lateral magnification of the focusing lens group located closer to the object than the focusing lens group closest to the image becomes too large when focusing on an object at infinity in the maximum telephoto state. This makes it difficult to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the maximum telephoto state. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (10) to 2.80, 2.50, 2.30, 2.00, 1.80, 1.50, 1.30, 1.00, or even 0.80.

[0051] If the value corresponding to conditional expression (10) falls below the lower limit, the lateral magnification of the focusing lens unit closest to the image side when focusing on an object at infinity in the telephoto end state becomes too large. As a result, it becomes difficult to suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to a close object in the telephoto end state. The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (10) to 0.13, 0.15, 0.18, 0.20, 0.23, or even 0.25.

[0052] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (11). 0.50<βF1w<2.60 (11) where βF1w is the combined lateral magnification of the focusing lens group included in the subsequent lens group GR, which is located closer to the object side than the focusing lens group closest to the image side, when focusing on an object at infinity in the wide-angle end state.

[0053] Conditional expression (11) defines an appropriate range for the combined lateral magnification when focusing on an object at infinity in the wide-angle end state of the focusing lens group that is located closer to the object than the focusing lens group closest to the image, among the focusing lens groups included in the subsequent lens group GR. Satisfying conditional expression (11) makes it possible to suppress fluctuations in various aberrations, including spherical aberration and coma, during focusing.

[0054] If the corresponding value of conditional expression (11) exceeds the upper limit, it becomes difficult to suppress fluctuations in various aberrations during focusing. By setting the upper limit of conditional expression (11) to 2.58, 2.55, 2.00, 1.80, 1.50, 1.30, or even 1.20, the effect of this embodiment can be further ensured.

[0055] If the corresponding value of conditional expression (11) falls below the lower limit, it becomes difficult to suppress fluctuations in various aberrations during focusing. By setting the lower limit of conditional expression (11) to 0.55, 0.60, 0.65, 0.70, or even 0.73, the effect of this embodiment can be further ensured.

[0056] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (12). 0.20<βF2w<1.80 (12) where βF2w is the lateral magnification of the focusing lens group closest to the image side among the focusing lens groups included in the subsequent lens group GR when focusing on an object at infinity in the wide-angle end state.

[0057] Conditional expression (12) defines an appropriate range for the lateral magnification of the focusing lens unit closest to the image side among the focusing lens units included in the subsequent lens unit GR when focusing on an object at infinity in the wide-angle end state. By satisfying conditional expression (12), fluctuations in various aberrations, including spherical aberration and coma, during focusing can be suppressed.

[0058] If the corresponding value of conditional expression (12) exceeds the upper limit, it becomes difficult to suppress fluctuations in various aberrations during focusing. By setting the upper limit of conditional expression (12) to 1.78, 1.75, 1.73, 1.70, 1.68, or even 1.60, the effect of this embodiment can be further ensured.

[0059] If the corresponding value of conditional expression (12) falls below the lower limit, it becomes difficult to suppress fluctuations in various aberrations during focusing. By setting the lower limit of conditional expression (12) to 0.23, 0.25, or even 0.28, the effect of this embodiment can be further ensured.

[0060] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (13). {βF1w+(1 / βF1w)} -2 ≦0.25 (13) where βF1w is the combined lateral magnification of the focusing lens group included in the subsequent lens group GR, which is located closer to the object side than the focusing lens group closest to the image side, when focusing on an object at infinity in the wide-angle end state.

[0061] Conditional expression (13) defines an appropriate range for the combined lateral magnification of the focusing lens group included in the subsequent lens group GR, which is located closer to the object than the focusing lens group closest to the image, when focusing on an object at infinity in the wide-angle end state. By satisfying conditional expression (13), fluctuations in various aberrations, including spherical aberration and coma, during focusing can be suppressed. If the value corresponding to conditional expression (13) exceeds the upper limit, it becomes difficult to suppress fluctuations in various aberrations during focusing.

[0062] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (14). {βF2w+(1 / βF2w)} -2 ≦0.25 (14) where βF2w is the lateral magnification of the focusing lens group closest to the image side among the focusing lens groups included in the subsequent lens group GR when focusing on an object at infinity in the wide-angle end state.

[0063] Conditional expression (14) defines an appropriate range for the lateral magnification of the focusing lens group closest to the image among the focusing lens groups included in the subsequent lens group GR when focusing on an object at infinity in the wide-angle end state. By satisfying conditional expression (14), fluctuations in various aberrations, including spherical aberration and coma, during focusing can be suppressed. If the corresponding value of conditional expression (14) exceeds the upper limit, it becomes difficult to suppress fluctuations in various aberrations during focusing.

[0064] In the variable magnification optical system ZL according to this embodiment, it is desirable that the subsequent lens group GR includes at least one lens group that is arranged closer to the image than the focusing lens group closest to the image among the focusing lens groups included in the subsequent lens group GR, thereby making it possible to effectively suppress fluctuations in various aberrations, including spherical aberration, during focusing.

[0065] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (15). 0.10<|fFs| / |fRF|<4.00 ···(15) where fRF is the focal length of the lens group arranged adjacent to the focusing lens group closest to the image side among the at least one lens group.

[0066] Conditional expression (15) defines an appropriate relationship between the focal length of the focusing lens group with the strongest refractive power among the focusing lens groups included in the subsequent lens group GR and the focal length of the lens group arranged adjacent to and on the image side of the focusing lens group closest to the image. By satisfying conditional expression (15), fluctuations in various aberrations, including spherical aberration, during focusing can be suppressed.

[0067] If the corresponding value of conditional expression (15) exceeds the upper limit, the refractive power of the lens group arranged adjacent to the focusing lens group closest to the image becomes strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (15) to 3.80, 3.50, 3.30, 3.00, 2.80, 2.50, 2.30, 2.00, 1.50, 1.30, or even 1.00.

[0068] If the corresponding value of conditional expression (15) falls below the lower limit, the refractive power of the focusing lens group becomes strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing. By setting the lower limit of conditional expression (15) to 0.13, 0.15, or even 0.18, the effect of this embodiment can be made even more certain.

[0069] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (16). 2ωw>75.0° (16) However, 2ωw: the total angle of view of the variable magnification optical system ZL in the wide-angle end state

[0070] Conditional expression (16) defines an appropriate range for the total angle of view of the variable magnification optical system ZL in the wide-angle end state. Satisfying conditional expression (16) is preferable because it provides a variable magnification optical system with a wide angle of view. Setting the lower limit of conditional expression (16) to 78.0°, 80.0°, or even 83.0° can further ensure the effects of this embodiment.

[0071] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (17). ft / fw>3.50 ···(17) where ft is the focal length of the variable magnification optical system ZL at the telephoto end

[0072] Conditional expression (17) defines an appropriate relationship between the focal length of the variable magnification optical system ZL in the telephoto end state and the focal length of the variable magnification optical system ZL in the wide-angle end state. Satisfying conditional expression (17) is preferable because it provides a variable magnification optical system with a high variable magnification ratio. Setting the lower limit of conditional expression (17) to 3.80, 4.00, 4.20, or even 4.40 can further ensure the effects of this embodiment.

[0073] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (18). 0.10<(-fN) / fL<1.00 (18) where fN is the focal length of the second lens element counting from the image side of the variable magnification optical system ZL. fL: focal length of the lens located closest to the image in the variable magnification optical system ZL

[0074] Conditional expression (18) defines an appropriate relationship between the focal length of the second lens element counting from the image side of the variable magnification optical system ZL and the focal length of the lens element closest to the image side of the variable magnification optical system ZL. By satisfying conditional expression (18), various aberrations, including coma in the wide-angle end state, can be effectively corrected.

[0075] If the value corresponding to conditional expression (18) exceeds the upper limit, the refractive power of the lens positioned closest to the image side in the variable magnification optical system ZL becomes strong, making it difficult to correct various aberrations, including coma in the wide-angle end state. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (18) to 0.95, 0.90, 0.85, 0.83, 0.80, 0.78, 0.75, 0.73, or even 0.70.

[0076] If the value corresponding to conditional expression (18) falls below the lower limit, the refractive power of the lens arranged second from the image side of the variable magnification optical system ZL becomes strong, making it difficult to correct various aberrations, including coma in the wide-angle end state. By setting the lower limit of conditional expression (18) to 0.13, 0.15, or even 0.18, the effect of this embodiment can be made more certain.

[0077] Next, a manufacturing method of the variable magnification optical system ZL described above will be outlined with reference to FIG. 23. First, a front lens group GA having positive refractive power, a first intermediate lens group GM1 having negative refractive power, a second intermediate lens group GM2 having positive refractive power, and a rear lens group GR are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is established in which the spacing between adjacent lens groups changes during magnification (Step ST2). Next, a first focusing lens group GF1 that moves along the optical axis during focusing is arranged closest to the rear lens group GR, and at least one other focusing lens group that moves along the optical axis along a different locus from the first focusing lens group GF1 during focusing is arranged closer to the image side of the first focusing lens group GF1 in the rear lens group GR (Step ST3). Next, one lens component is arranged in the focusing lens group closest to the first focusing lens group GF1 among the other focusing lens groups (Step ST4). Then, the lenses are arranged in the lens barrel so as to satisfy at least the above conditional expression (1) (step ST5). This manufacturing method makes it possible to manufacture a variable magnification optical system with little aberration fluctuation during focusing. [Example]

[0078] Variable magnification optical systems ZL according to examples of this embodiment will be described below with reference to the drawings. FIGS. 1, 4, 7, 10, 13, 16, and 19 are cross-sectional views showing the configuration and refractive power distribution of variable magnification optical systems ZL {ZL(1) to ZL(7)} according to Examples 1 to 7. In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(7) according to Examples 1 to 7, the direction of movement of the focusing group along the optical axis when focusing from infinity to a close-distance object is indicated by an arrow accompanied by the word "focusing." In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(7) according to Examples 1 to 7, the direction of movement of each lens group along the optical axis when changing magnification from the wide-angle end state (W) to the telephoto end state (T) is indicated by an arrow.

[0079] 1, 4, 7, 10, 13, 16, and 19, each lens group is represented by a combination of the symbol G and a number, and each lens is represented by a combination of the symbol L and a number. In this case, to prevent the symbols and numbers from becoming too numerous and complicated, each example uses its own unique combination of symbols and numbers to represent the lens groups, etc. Therefore, even if the same combination of symbols and numbers is used between examples, this does not mean that the examples have the same configuration.

[0080] Tables 1 to 7 are shown below, with Table 1 showing data on the various elements in Example 1, Table 2 in Example 2, Table 3 in Example 3, Table 4 in Example 4, Table 5 in Example 5, Table 6 in Example 6, and Table 7 in Example 7. In each example, the d-line (wavelength λ=587.6 nm) and g-line (wavelength λ=435.8 nm) were selected as the targets for calculating aberration characteristics.

[0081] In the [Overall Specifications] table, f is the focal length of the entire lens system, FNO is the F-number, 2ω is the angle of view (unit: ° (degrees), where ω is half the 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 focused at infinity plus BF, and BF is the distance from the last lens surface to the image plane I on the optical axis when focused at infinity (back focus). Note that these values ​​are shown for both the wide-angle end (W) and the telephoto end (T) magnification settings.

[0082] In the table under "Overall Specifications," fM1w indicates the focal length of the first intermediate lens group in the maximum wide-angle state. fM2w indicates the focal length of the second intermediate lens group in the maximum wide-angle state. MTF1 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 in the maximum telephoto state. MTF2 indicates the absolute value of the movement amount of the other focusing lens group closest to the first focusing lens group when focusing from an object at infinity to a close object in the maximum telephoto state. βF1w indicates the combined lateral magnification of the focusing lens group included in the subsequent lens group that is located closer to the object than the focusing lens group closest to the image when focusing on an object at infinity in the maximum wide-angle state. βF2w indicates the lateral magnification of the focusing lens group included in the subsequent lens group that is closest to the image when focusing on an object at infinity in the maximum wide-angle state. βF1t indicates the combined lateral magnification of the focusing lens group included in the subsequent lens group, which is located closer to the object than the focusing lens group closest to the image, when focusing on an object at infinity in the telephoto end state. βF2t indicates the lateral magnification of the focusing lens group included in the subsequent lens group, which is located closest to the image, when focusing on an object at infinity in the telephoto end state. fN indicates the focal length of the second lens counting from the image side of the variable magnification optical system. fL indicates the focal length of the lens closest to the image side of the variable magnification optical system. fRw indicates the focal length of the subsequent lens group in the wide-angle end state.

[0083] In the [Lens Specifications] table, the surface number indicates the order of the optical surface from the object side along the direction of light ray travel, R is the radius of curvature of each optical surface (surfaces whose center of curvature is on the image side have a positive value), D is the surface spacing, which is the distance on the optical axis from each optical surface to the next optical surface (or image plane), nd is the refractive index of the optical element material with respect to the d-line, and νd is the Abbe number of the optical element material with respect to the d-line. The "∞" next to the radius of curvature indicates a flat surface or an aperture, and (stop S) indicates the aperture stop S. The refractive index of air, nd = 1.00000, is omitted. If the optical surface is aspherical, an * is added to the surface number, and the paraxial radius of curvature is shown in the "radius of curvature R" column.

[0084] In the [Aspherical Data] table, the shape of the aspherical surface shown in [Lens Specifications] is shown by the following formula (A). X(y) is the distance (amount of sag) along the optical axis from the tangent plane at the vertex of the aspherical surface to the position on the aspherical surface at height y, R is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and Ai is the ith aspherical coefficient. "En" is the square root of the square root of the aspherical surface. -n For example, 1.234E-05 = 1.234 x 10 -5 The second-order aspherical coefficient A2 is 0, and is therefore omitted.

[0085] X(y)=(y 2 / R) / {1+(1-κ×y 2 / R 2 ) 1 / 2}+A4×y 4 +A6×y 6 +A8×y 8 +A10×y 10 …(A)

[0086] The [Variable Distance Data] table shows the surface spacing for surface number i, which has a surface spacing of (Di) in the [Lens Specifications] table. The [Variable Distance Data] table also shows the surface spacing when focused at infinity and when focused at close range.

[0087] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0088] In the following, for all specifications, the focal length f, radius of curvature R, surface spacing D, and other lengths are generally expressed in "mm" unless otherwise specified, but this is not limited to this, as the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0089] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0090] (First Example) The first embodiment will be described with reference to FIGS. 1 to 3 and Table 1. FIG. 1 shows the lens configuration of the variable magnification optical system of the first embodiment. The variable magnification optical system ZL(1) of the first embodiment is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having negative refractive power, and a seventh lens group G7 having positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first to seventh lens groups G1 to G7 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed between the second lens group G2 and the third lens group G3. During magnification variation, the aperture stop S moves along the optical axis together with the third lens group G3. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of that lens group, and this is the same in all of the following embodiments.

[0091] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L11 with its convex surface facing the object side and a positive meniscus lens L12 with its convex surface facing the object side, and a positive meniscus lens L13 with its convex surface facing the object side.

[0092] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a cemented positive lens consisting of a negative meniscus lens L22 with a convex surface facing the object side and 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 lens surface facing the object side of the negative meniscus lens L21 is aspheric.

[0093] The third lens group G3 is composed of a biconvex positive lens L31, the object-side lens surface of which is aspherical.

[0094] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L41 with its convex surface facing the object side and a biconvex positive lens L42, a cemented positive lens consisting of a biconvex positive lens L43 and a negative meniscus lens L44 with its concave surface facing the object side, and a positive meniscus lens L45 with its concave surface facing the object side. The object side surface of the positive meniscus lens L45 is aspherical.

[0095] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L51 with its concave surface facing the object side, and a biconcave negative lens L52.

[0096] The sixth lens group G6 is composed of a biconcave negative lens L61, the object-side lens surface of which is aspherical.

[0097] The seventh lens group G7 is composed of a positive meniscus lens L71 with its convex surface facing the object side. An image surface I is located on the image side of the seventh lens group G7.

[0098] In this embodiment, the first lens group G1 constitutes the front lens group GA, which has positive refractive power. The second lens group G2 constitutes the first intermediate lens group GM1, which has negative refractive power. The third lens group G3 and the fourth lens group G4 constitute the second intermediate lens group GM2, which has positive refractive power as a whole. The fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 constitute the rear lens group GR, which has negative refractive power as a whole. When focusing from an object at infinity to a close object, the fifth lens group G5 and the sixth lens group G6, which constitute the rear lens group GR, move toward the image side along the optical axis along different loci (movement amounts). That is, the fifth lens group G5 corresponds to the first focusing lens group GF1, which is located closest to the object of the rear lens group GR. The sixth lens group G6 corresponds to the second focusing lens group GF2, which is another focusing lens group located closer to the image side than the first focusing lens group GF1.

[0099] Table 1 below lists the values ​​of the specifications of the variable magnification optical system according to the first example.

[0100] (Table 1) [All Yuan] Multiplication ratio=4.74 fM1w=-17.655 fM2w=29.833 MTF1=0.344 MTF2=0.846 βF1w=1.071 βF2w=1.577 βF1t=1.111 βF2t=3.094 fN=-38.218 fL=129.310 fRw=-46.388 WMT f 24.700 84.962 116.999 FNO 4.07 4.07 4.07 2ω 85.22 27.40 20.32 Ymax 21.60 21.60 21.60 TL 128.45 162.37 178.87 BF 13.699 35.087 35.287 [レンズ Zhugen] Side number RD nd νd Object surface ∞ 1 164.9399 2.000 1.73800 32.26 2 56.4260 7.579 1.59319 67.90 3 329.6967 0.200 4 61.7045 5.273 1.81600 46.59 5 267.7629 (D5) 6* 242.3772 1.500 1.81600 46.59 7 16.6184 5.149 8 879.6675 1.000 1.58913 61.22 9 18.5708 4.233 1.95000 29.37 10 79.8132 2.602 11 -27.5163 1.000 1.77250 49.62 12 -60.4508 (D12) 13 ∞ 2.000 (Aperture S) 14* 33.9421 3.661 1.74310 49.44 15 -231.3985 (D15) 16 30.3875 1.000 1.88300 40.66 17 15.6459 6.192 1.49782 82.57 18 -453.7663 0.776 19 575.4338 5.622 1.51680 64.14 20 -18.7425 1.000 2.00069 25.46 21 -32.0090 1.264 22* -70.8783 5.056 1.55332 71.67 23 -21.6449 (D23) 24 -90.7732 3.558 1.94595 17.98 25 -39.1419 0.200 26 -156.1339 1.000 1.90366 31.27 27 79.8952 (D27) 28* -85.4924 1.500 1.81600 46.59 29 49.4815 (D29) 30 55.2902 3.197 1.90200 25.26 31 102.2388 BF Image plane ∞ [Aspherical Data] Surface 6 κ=1.0000,A4=5.35995E-06,A6=-8.27153E-09,A8=2.12565E-11,A10=-2.60526E-14 Surface 14 κ=1.0000,A4=-7.33442E-06,A6=4.81859E-09,A8=-4.26147E-11,A10=-2.53196E-14 Surface 22 κ=1.0000,A4=-2.36052E-05,A6=6.01748E-09,A8=1.01789E-10,A10=1.24064E-13 Page 28 κ=1.0000,A4=-5.15978E-06,A6=-5.92439E-09,A8=4.45911E-12,A10=-6.10897E-15 [Variable Interval Data] Infinity focus Close focus WMTWMT D5 2.000 31.270 39.333 2.000 31.270 39.333 D12 17.917 3.226 2.000 17.917 3.226 2.000 D15 13.739 3.651 2.000 13.739 3.651 2.000 D23 6.364 2.978 2.000 6.466 3.278 2.344 D27 4.416 6.716 5.540 5.042 7.231 6.042 D29 3.757 12.879 26.147 3.029 12.064 25.302 [Lens group data] Group starting plane focal length G1 1 97.130 G2 6 -17.655 G3 14 40.069 G4 16 35.478 G5 24 -320.573 G6 28 -38.218 G7 30 129.310

[0101] FIG. 2(A) is a diagram showing various aberrations of the variable magnification optical system of Example 1 when focusing at infinity in the wide-angle end state. FIG. 2(B) is a diagram showing various aberrations of the variable magnification optical system of Example 1 when focusing at infinity in the telephoto end state. FIG. 3(A) is a diagram showing various aberrations of the variable magnification optical system of Example 1 when focusing at close distances in the wide-angle end state. FIG. 3(B) is a diagram showing various aberrations of the variable magnification optical system of Example 1 when focusing at close distances in the telephoto end state. In each aberration diagram when focusing at infinity, FNO represents the F-number, and Y represents the image height. In each aberration diagram when focusing at close distances, NA represents the numerical aperture, and Y represents the image height. Note that spherical aberration diagrams show the F-number or numerical aperture value corresponding to the maximum aperture, astigmatism diagrams and distortion diagrams show the maximum value of image height, and coma diagrams show the value of each image height. "d" indicates the d-line (wavelength λ=587.6 nm), and "g" indicates the g-line (wavelength λ=435.8 nm). In the astigmatism diagrams, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. Note that the same symbols as in this embodiment are used in the aberration diagrams of the following embodiments, and redundant explanations will be omitted.

[0102] From the various aberration diagrams, it can be seen that the variable magnification optical system of Example 1 has excellent imaging performance, with various aberrations being well corrected not only when focusing at infinity but also when focusing at close distances, from the wide-angle end state to the telephoto end state.

[0103] (Second Example) The second example will be described with reference to FIGS. 4 to 6 and Table 2. FIG. 4 shows the lens configuration of the variable magnification optical system of the second example. The variable magnification optical system ZL(2) of the second example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, and a seventh lens group G7 having positive refractive power. 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 toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed between the second lens group G2 and the third lens group G3. When the magnification is changed, the aperture stop S moves along the optical axis together with the third lens group G3.

[0104] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L11 with its convex surface facing the object side and a positive meniscus lens L12 with its convex surface facing the object side, and a positive meniscus lens L13 with its convex surface facing the object side.

[0105] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a cemented positive lens consisting of a biconcave negative lens L22 and a biconvex positive lens L23, and a negative meniscus lens L24 with a concave surface facing the object side. The object side surface of the negative meniscus lens L21 is aspheric.

[0106] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L31 with a convex surface facing the object side, a biconvex positive lens L32, a cemented positive lens formed by a negative meniscus lens L33 with a convex surface facing the object side and a biconvex positive lens L34, and a negative meniscus lens L35 with a concave surface facing the object side.

[0107] The fourth lens group G4 is composed of a cemented positive lens consisting of a negative meniscus lens L41 with its convex surface facing the object side and a biconvex positive lens L42.

[0108] The fifth lens group G5 is composed of, arranged along the optical axis from the object side, a biconcave negative lens L51, a cemented positive lens consisting of a biconvex positive lens L52 and a negative meniscus lens L53 with its concave surface facing the object side. The negative meniscus lens L53 has an aspheric lens surface facing the image side.

[0109] The sixth lens group G6 is composed of a biconcave negative lens L61, the object-side lens surface of which is aspherical.

[0110] The seventh lens group G7 is composed of a biconvex positive lens L71. An image surface I is located on the image side of the seventh lens group G7.

[0111] In this embodiment, the first lens group G1 constitutes the front lens group GA, which has positive refractive power. The second lens group G2 constitutes the first intermediate lens group GM1, which has negative refractive power. The third lens group G3 and the fourth lens group G4 constitute the second intermediate lens group GM2, which has positive refractive power as a whole. The fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 constitute the rear lens group GR, which has negative refractive power as a whole. When focusing from an object at infinity to a close object, the fifth lens group G5, which constitutes the rear lens group GR, moves toward the object along the optical axis, and the sixth lens group G6, which constitutes the rear lens group GR, moves toward the image along the optical axis. In other words, the fifth lens group G5 corresponds to the first focusing lens group GF1, which is arranged closest to the object of the rear lens group GR. The sixth lens group G6 corresponds to the second focusing lens group GF2, which is another focusing lens group arranged closer to the image side than the first focusing lens group GF1.

[0112] Table 2 below lists the values ​​of the specifications of the variable magnification optical system according to the second example.

[0113] (Table 2) [Overall specifications] Magnification ratio=4.74 fM1w=-17.052 fM2w=29.062 MTF1=0.279 MTF2=0.983 βF1w=1.045 βF2w=1.670 βF1t=1.038 βF2t=3.943 fN=-31.580 fL=78.519 fRw=-61.009 WMT f 24.700 69.988 117.001 FNO 4.06 4.06 4.07 2ω 85.22 33.90 20.18 Ymax 21.60 21.60 21.60 TL 134.46 162.88 189.46 BF 11.455 31.812 35.779 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 158.1192 2.000 1.73800 32.36 2 69.8101 6.421 1.59319 67.90 3 308.6050 0.200 4 66.9111 5.695 1.81600 46.59 5 207.3443 (D5) 6* 78.5237 1.500 1.81600 46.59 7 16.7218 5.684 8 -172.8187 1.000 1.80400 46.60 9 21.0165 4.905 1.90200 25.26 10 -209.4912 1.624 11 -33.2740 1.000 1.81600 46.59 12 -156.9568 (D12) 13 ∞ 2.000 (Aperture S) 14 37.1973 2.686 1.80518 25.45 15 73.4737 0.200 16 49.8914 3.509 1.59319 67.90 17 -304.2612 0.200 18 35.7712 1.000 1.84850 43.79 19 16.8712 7.999 1.59319 67.90 20 -57.2564 1.355 21 -36.5767 1.000 2.00069 25.46 22 -90.8325 (D22) 23 39.2071 1.000 2.00069 25.46 24 25.6545 6.685 1.59319 67.90 25 -38.5079 (D25) 26 -38.3881 1.000 1.94595 17.98 27 96.5319 0.415 28 37.3704 7.406 1.89286 20.36 29 -30.3636 1.000 1.68893 31.16 30* -185.8364 (D30) 31* -42.4996 1.500 1.81600 46.59 32 66.5016 (D32) 33 148.1143 4.377 1.89286 20.36 34 -131.2552 BF Image plane ∞ [Aspherical surface] Page 6 κ=1.0000,A4=1.23369E-06,A6=-3.23247E-09,A8=-1.36560E-12,A10=3.42111E-15 Page 30 κ=1.0000,A4=2.14045E-05,A6=-7.56199E-10,A8=-2.61800E-11,A10=1.98882E-13 Page 31 κ=1.0000,A4=-3.01641E-06,A6=-1.16781E-08,A8=-5.08849E-11,A10=3.00363E-13 [Variable Interval Data] Infinity focus Close focus WMTWMT D5 2.000 26.048 41.130 2.000 26.048 41.130 D12 21.130 5.163 2.000 21.130 5.163 2.000 D22 12.345 4.345 2.000 12.345 4.345 2.000 D25 2.023 7.035 9.889 2.000 6.858 9.610 D30 7.665 6.668 3.602 8.357 7.660 4.865 D32 4.476 8.453 21.695 3.807 7.637 20.712 [Lens group data] Group starting plane focal length G1 1 111.149 G2 6 -17.052 G3 14 34.545 G4 23 40.961 G5 26 915.545 G6 31 -31.580 G7 33 78.519

[0114] Fig. 5(A) is a diagram showing various aberrations when the variable magnification optical system of Example 2 is focused at infinity in the wide-angle end state. Fig. 5(B) is a diagram showing various aberrations when the variable magnification optical system of Example 2 is focused at infinity in the telephoto end state. Fig. 6(A) is a diagram showing various aberrations when the variable magnification optical system of Example 2 is focused at a close distance in the wide-angle end state. Fig. 6(B) is a diagram showing various aberrations when the variable magnification optical system of Example 2 is focused at a close distance in the telephoto end state. It can be seen from the various aberration diagrams that the variable magnification optical system of Example 2 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state not only when focused at infinity but also when focused at a close distance.

[0115] (Third Example) The third example will be described with reference to FIGS. 7 to 9 and Table 3. FIG. 7 shows the lens configuration of the variable magnification optical system of the third example. The variable magnification optical system ZL(3) of the third example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having negative refractive power. When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first to seventh lens groups G1 to G7 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. An aperture stop S is disposed between the second lens group G2 and the third lens group G3. When the magnification is changed, the aperture stop S moves along the optical axis together with the third lens group G3.

[0116] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a plano-concave negative lens L11 with its flat surface facing the object side and a biconvex positive lens L12, and a positive meniscus lens L13 with its convex surface facing the object side.

[0117] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a cemented positive lens consisting of a biconcave negative lens L22 and a biconvex positive lens L23, and a plano-concave negative lens L24 with a flat surface facing the image side. The object-side lens surface of the negative meniscus lens L21 is aspheric.

[0118] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L31 with a convex surface facing the object side, a biconvex positive lens L32, and a negative meniscus lens L33 with a concave surface facing the object side. The object side surface of the positive meniscus lens L31 is aspherical.

[0119] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L41, and a cemented positive lens consisting of a negative meniscus lens L42 with its convex surface facing the object side and a biconvex positive lens L43.

[0120] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L51 with its concave surface facing the object side, and a biconvex positive lens L52.

[0121] The sixth lens group G6 is composed of a positive meniscus lens L61 with its concave surface facing the object side. The positive meniscus lens L61 has an aspherical lens surface facing the image side.

[0122] The seventh lens group G7 is composed of, arranged along the optical axis from the object side, a biconcave negative lens L71 and a positive meniscus lens L72 with its convex surface facing the object side. An image surface I is located on the image side of the seventh lens group G7.

[0123] In this embodiment, the first lens group G1 constitutes the front lens group GA having positive refractive power. The second lens group G2 constitutes the first intermediate lens group GM1 having negative refractive power. The third lens group G3 and the fourth lens group G4 constitute the second intermediate lens group GM2 having positive refractive power as a whole. The fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 constitute the rear lens group GR having negative refractive power as a whole. When focusing from an object at infinity to a close object, the fifth lens group G5 and the sixth lens group G6 constituting the rear lens group GR move toward the object along the optical axis along different loci (movement amounts). That is, the fifth lens group G5 corresponds to the first focusing lens group GF1, which is arranged closest to the object of the rear lens group GR. The sixth lens group G6 corresponds to the second focusing lens group GF2, which is another focusing lens group arranged closer to the image than the first focusing lens group GF1.

[0124] Table 3 below lists the values ​​of the specifications of the variable magnification optical system according to the third example.

[0125] (Table 3) [Overall specifications] Magnification ratio=4.56 fM1w=-21.004 fM2w=33.500 MTF1=1.413 MTF2=0.980 βF1w=0.770 βF2w=0.954 βF1t=0.658 βF2t=0.946 fN=-29.642 fL=97.753 fRw=-158.485 WMT f 22.600 70.008 103.000 FNO 4.08 4.08 4.08 2ω 91.54 32.98 22.38 Ymax 21.60 21.60 21.60 TL 139.45 164.17 199.46 BF 11.455 38.439 39.811 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 ∞ 2.000 1.84666 23.80 2 205.3318 6.252 1.59319 67.90 3 -265.8961 0.200 4 76.0378 4.794 1.77250 49.62 5 155.1941 (D5) 6* 118.3890 1.500 1.74389 49.53 7 19.9637 7.065 8 -66.8860 1.000 1.59319 67.90 9 24.3441 6.322 1.68893 31.16 10 -44.9916 0.573 11 -35.2853 1.000 1.81600 46.59 12∞ (D12) 13 ∞ 2.000 (Aperture S) 14* 53.1253 2.930 1.69343 53.30 15 3836.4092 0.200 16 51.4447 4.772 1.59319 67.90 17 -49.9261 2.897 18 -36.2339 1.000 1.83481 42.73 19 -1562.5863 (D19) 20 41.8346 4.903 1.59319 67.90 21 -69.8682 0.200 22 94.4862 1.000 1.81600 46.59 23 19.6322 7.665 1.49782 82.57 24 -56.1775 (D24) 25 -29.1264 1.000 1.90200 25.26 26 -57.1334 2.304 27 93.4868 5.411 1.80400 46.60 28 -48.3174 (D28) 29 -85.5900 1.691 1.77387 47.25 30* -67.1935 (D30) 31 -56.6426 1.000 1.83481 42.73 32 44.2945 2.378 33 64.6533 3.175 1.94595 17.98 34 209.7975 BF Image plane ∞ [Aspherical surface] Page 6 κ=1.0000,A4=2.28381E-06,A6=-1.46352E-09,A8=-1.25256E-12,A10=5.36019E-15 Page 14 κ = 1.0000, A4 = -2.87497E-06, A6 = 1.67465E-09, A8 = -4.38683E-12, A10 = -1.60647E-15 Page 30 κ = 1.0000, A4 = 9.04034E-06, A6 = 8.01114E-10, A8 = 6.16585E-12, A10 = -1.63681E-14 [Variable interval data] Infinity focus state, close focus state W M T W M T D5 2.000 16.912 51.168 2.000 16.912 51.168 D12 23.202 2.589 2.000 23.202 2.589 2.000 D19 10.189 2.436 2.000 10.189 2.436 2.000 D24 5.554 14.413 18.443 4.619 13.500 17.030 D28 2.044 8.464 8.285 2.513 8.681 8.718 D30 9.778 5.681 2.517 10.245 6.377 3.497 [Lens group data] Group, starting surface, focal length G1 1 157.131 G2 6 -22.004 G3 14 59.544 G4 20 43.565 G5 25 84.112 G6 29 388.390 G7 31 -43.760

[0126] Fig. 8(A) is a diagram showing various aberrations when the variable magnification optical system of Example 3 is in the wide-angle end state and focusing on infinity. Fig. 8(B) is a diagram showing various aberrations when the variable magnification optical system of Example 3 is in the telephoto end state and focusing on infinity. Fig. 9(A) is a diagram showing various aberrations when the variable magnification optical system of Example 3 is in the wide-angle end state and focusing on a close distance. Fig. 9(B) is a diagram showing various aberrations when the variable magnification optical system of Example 3 is in the telephoto end state and focusing on a close distance. It can be seen from the various aberration diagrams that the variable magnification optical system of Example 3 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state not only when focusing on infinity but also when focusing on a close distance.

[0127] (Fourth Example) Example 4 will be described with reference to FIGS. 10 to 12 and Table 4. FIG. 10 shows the lens configuration of a variable magnification optical system according to Example 4. The variable magnification optical system ZL(4) according to Example 4 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having negative refractive power, and a seventh lens group G7 having positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first to sixth lens groups G1 to G6 move toward the object side along the optical axis, and the seventh lens group G7 moves along the optical axis once toward the object side and then toward the image side, changing the spacing between adjacent lens groups. The aperture stop S is disposed between the second lens group G2 and the third lens group G3. When varying the magnification, the aperture stop S moves along the optical axis together with the third lens group G3.

[0128] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L11 with its convex surface facing the object side and a positive meniscus lens L12 with its convex surface facing the object side, and a positive meniscus lens L13 with its convex surface facing the object side.

[0129] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a cemented positive lens consisting of a negative meniscus lens L22 with a convex surface facing the object side and a positive meniscus lens L23 with a convex surface facing the object side, and a biconcave negative lens L24. The object-side lens surface of the negative meniscus lens L21 is aspheric.

[0130] The third lens group G3 is composed of a positive meniscus lens L31 with a convex surface facing the object side, and a positive meniscus lens L32 with a convex surface facing the object side. The positive meniscus lens L31 has an aspheric lens surface facing the object side.

[0131] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L41 with a convex surface facing the object side and a biconvex positive lens L42, a cemented negative lens consisting of a biconvex positive lens L43 and a negative meniscus lens L44 with a concave surface facing the object side, and a positive meniscus lens L45 with a concave surface facing the object side. The object side surface of the positive meniscus lens L45 is aspherical.

[0132] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L51 and a biconcave negative lens L52.

[0133] The sixth lens group G6 is composed of a biconcave negative lens L61, the object-side lens surface of which is aspherical.

[0134] The seventh lens group G7 is composed of a positive meniscus lens L71 with its convex surface facing the object side. An image surface I is located on the image side of the seventh lens group G7.

[0135] In this embodiment, the first lens group G1 constitutes the front lens group GA, which has positive refractive power. The second lens group G2 constitutes the first intermediate lens group GM1, which has negative refractive power. The third lens group G3 and the fourth lens group G4 constitute the second intermediate lens group GM2, which has positive refractive power as a whole. The fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 constitute the rear lens group GR, which has negative refractive power as a whole. When focusing from an object at infinity to a close object, the fifth lens group G5 and the sixth lens group G6, which constitute the rear lens group GR, move toward the image side along the optical axis along different loci (movement amounts). That is, the fifth lens group G5 corresponds to the first focusing lens group GF1, which is located closest to the object of the rear lens group GR. The sixth lens group G6 corresponds to the second focusing lens group GF2, which is another focusing lens group located closer to the image side than the first focusing lens group GF1.

[0136] Table 4 below lists the values ​​of the specifications of the variable magnification optical system according to the fourth example.

[0137] (Table 4) [Overall specifications] Magnification ratio=7.85 fM1w=-17.910 fM2w=29.807 MTF1=0.411 MTF2=0.952 βF1w=1.005 βF2w=1.561 βF1t=1.019 βF2t=3.610 fN=-35.994 fL=170.661 fRw=-44.489 WMT f 24.700 104.937 194.000 FNO 4.02 5.60 6.42 2ω 85.20 22.32 12.46 Ymax 21.60 21.60 21.60 TL 130.17 173.77 204.45 BF 12.455 42.064 38.864 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 143.1350 2.000 1.73800 32.33 2 54.4612 7.561 1.59319 67.90 3 300.0372 0.200 4 69.5685 5.062 1.77250 49.62 5 409.0849 (D5) 6* 350.7774 1.500 1.88202 37.22 7 18.4546 4.874 8 680.4222 1.000 1.49782 82.57 9 19.1843 4.572 1.85000 27.03 10 106.5036 1.893 11 -45.6629 1.000 1.77250 49.62 12 1027.7309 (D12) 13 ∞ 2.000 (Aperture S) 14* 29.9260 2.529 1.67798 54.89 15 104.6758 0.200 16 37.9415 1.902 1.80809 22.74 17 50.9616 (D17) 18 24.4645 1.758 1.90265 35.77 19 14.5575 6.153 1.49782 82.57 20 -102.7198 0.611 21 1507.9760 4.275 1.51680 64.13 22 -24.0428 1.000 2.00069 25.46 23 -87.8436 0.355 24* -128.1468 4.545 1.55332 71.68 25 -20.7344 (D25) 26 738.8688 4.696 1.80809 22.74 27 -32.2613 0.200 28 -47.0892 1.000 1.81600 46.59 29 81.3412 (D29) 30* -59.9653 1.500 1.77387 47.25 31 52.5852 (D31) 32 51.1837 3.083 1.68893 31.16 33 88.4174 BF Image plane ∞ [Aspherical surface] Page 6 κ=1.0000,A4=3.16658E-06,A6=-5.96049E-09,A8=1.61416E-11,A10=-2.62532E-14 Page 14 κ=1.0000,A4=-7.64081E-06,A6=-1.02540E-08,A8=8.93373E-11,A10=-6.51264E-13 Page 24 κ=1.0000,A4=-3.12885E-05,A6=3.71787E-08,A8=-1.70544E-10,A10=1.40544E-12 Page 30 κ=1.0000,A4=-5.46471E-06,A6=-2.65649E-0,A8=1.47492E-10,A10=-2.98216E-13 [Can change the interval データ] Infinity focus state Close focus state WMTWMT D5 2.010 35.817 51.220 2.010 35.817 51.220 D12 21.188 4.932 2.030 21.188 4.932 2.030 D17 13.539 4.497 2.000 13.539 4.497 2.000 D25 7.124 3.715 2.000 7.265 4.018 2.411 D29 4.593 6.548 4.486 5.167 7.059 5.027 D31 3.794 10.730 38.386 3.078 9.916 37.434 [Lens group data] Group starting plane focal length G1 1 103.273 G2 6 -17.910 G3 14 44.938 G4 18 37.783 G5 26 -980.001 G6 30 -35.994 G7 32 170.661

[0138] Fig. 11(A) is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focusing at infinity in the wide-angle end state. Fig. 11(B) is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focusing at infinity in the telephoto end state. Fig. 12(A) is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focusing at close distances in the wide-angle end state. Fig. 12(B) is a diagram showing various aberrations of the variable magnification optical system of Example 4 when focusing at close distances in the telephoto end state. It can be seen from the various aberration diagrams that the variable magnification optical system of Example 4 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state not only when focusing at infinity but also when focusing at close distances.

[0139] (Fifth Example) Fifth Example will be described with reference to Figures 13 to 15 and Table 5. Figure 13 is a diagram showing the lens configuration of a variable magnification optical system according to the fifth example. The variable magnification optical system ZL(5) according to the fifth example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, a seventh lens group G7 having negative refractive power, and an eighth lens group G8 having positive refractive power. 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 toward the object along the optical axis, and the eighth lens group G8 moves along the optical axis once toward the object and then toward the image, changing the spacing between adjacent lens groups. An aperture diaphragm S is disposed between the third lens group G3 and the fourth lens group G4. When changing magnification, the aperture diaphragm S moves along the optical axis together with the fourth lens group G4.

[0140] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L11 with its convex surface facing the object side and a positive meniscus lens L12 with its convex surface facing the object side, and a positive meniscus lens L13 with its convex surface facing the object side.

[0141] The second lens group G2 is composed of, arranged along the optical axis from the object side, a biconcave negative lens L21, a cemented positive lens consisting of a negative meniscus lens L22 with its convex surface facing the object side and a positive meniscus lens L23 with its convex surface facing the object side. The object side surface of the negative lens L21 is aspheric.

[0142] The third lens group G3 is composed of a biconcave negative lens L31.

[0143] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L41 with its convex surface facing the object side and a positive meniscus lens L42 with its convex surface facing the object side. The object side surface of the positive meniscus lens L41 is aspherical.

[0144] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L51 with a convex surface facing the object side and a biconvex positive lens L52, a cemented negative lens consisting of a positive meniscus lens L53 with a concave surface facing the object side and a negative meniscus lens L54 with a concave surface facing the object side, and a positive meniscus lens L55 with a concave surface facing the object side. The object side surface of the positive meniscus lens L55 is aspherical.

[0145] The sixth lens group G6 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L61 and a biconcave negative lens L62.

[0146] The seventh lens group G7 is composed of a biconcave negative lens L71, the object-side lens surface of which is aspherical.

[0147] The eighth lens group G8 is composed of a positive meniscus lens L81 with its convex surface facing the object side. An image surface I is located on the image side of the eighth lens group G8.

[0148] In this embodiment, the first lens group G1 constitutes the front lens group GA, which has positive refractive power. The second lens group G2 and the third lens group G3 constitute the first intermediate lens group GM1, which has negative refractive power as a whole. The fourth lens group G4 and the fifth lens group G5 constitute the second intermediate lens group GM2, which has positive refractive power as a whole. The sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 constitute the rear lens group GR, which has negative refractive power as a whole. When focusing from an object at infinity to a close object, the sixth lens group G6 and the seventh lens group G7, which constitute the rear lens group GR, move toward the image side along the optical axis along different trajectories (movement amounts). In other words, the sixth lens group G6 corresponds to the first focusing lens group GF1, which is arranged closest to the object side of the rear lens group GR. The seventh lens group G7 corresponds to the second focusing lens group GF2, which is another focusing lens group arranged closer to the image side than the first focusing lens group GF1.

[0149] Table 5 below lists the values ​​of the specifications of the variable magnification optical system according to the fifth example.

[0150] (Table 5) [Overall specifications] Magnification ratio=7.85 fM1w=-17.295 fM2w=29.310 MTF1=0.371 MTF2=0.950 βF1w=1.002 βF2w=1.550 βF1t=1.016 βF2t=3.590 fN=-36.530 fL=180.299 fRw=-44.658 WMT f 24.700 104.916 193.992 FNO 3.98 5.60 6.48 2ω 85.20 22.32 12.46 Ymax 21.60 21.60 21.60 TL 129.45 174.02 204.45 BF 12.454 43.256 39.757 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 140.6369 2.000 1.73800 32.33 2 54.2993 7.774 1.59319 67.90 3 306.9344 0.200 4 70.1192 5.137 1.77250 49.62 5 433.0896 (D5) 6* -348.9741 1.500 1.88202 37.22 7 18.5669 4.368 8 132.2861 1.000 1.49782 82.57 9 19.1562 4.619 1.85000 27.03 10 92.2216 (D10) 11 -59.9587 1.000 1.77250 49.62 12 207.6789 (D12) 13 ∞ 2.000 (Aperture S) 14* 29.0382 2.246 1.67798 54.89 15 56.3251 0.200 16 35.5481 2.153 1.80809 22.74 17 64.9456 (D17) 18 22.8201 1.147 1.90265 35.77 19 14.0716 6.794 1.49782 82.57 20 -62.9717 0.250 21 -578.5647 3.866 1.51680 64.13 22 -26.3104 1.000 2.00069 25.46 23 -262.9123 0.400 24* -252.2011 4.807 1.55332 71.68 25 -20.2354 (D25) 26 406.6131 4.916 1.80809 22.74 27 -31.2178 0.200 28 -44.1001 1.000 1.81600 46.59 29 76.8052 (D29) 30* -65.9674 1.500 1.77387 47.25 31 49.9596 (D31) 32 48.7044 2.979 1.68893 31.16 33 78.1205 BF Image plane ∞ [Aspherical data] Side 6 κ=1.0000,A4=6.01924E-06,A6=-9.78216E-09,A8=1.91188E-11,A10=-2.54581E-14 Page 14 κ = 1.0000, A4 = -8.67328E-06, A6 = -1.41146E-08, A8 = 1.05557E-10, A10 = -7.15518E-13 The 24th surface κ = 1.0000, A4 = -3.58225E-05, A6 = 5.16946E-08, A8 = -2.69722E-10, A10 = 2.25425E-12 The 30th surface κ = 1.0000, A4 = -5.04731E-06, A6 = -3.08030E-08, A8 = 1.84868E-10, A10 = -5.03672E-13 [Variable interval data] Infinity focus state, close focus state W M T W M T D5 2.591 35.849 51.107 2.591 35.849 51.107 D10 2.474 1.925 1.779 2.474 1.925 1.779 D12 19.518 4.834 2.144 19.518 4.834 2.144 D17 13.288 4.561 2.000 13.288 4.561 2.000 D25 7.742 3.790 2.000 7.926 4.060 2.371 D29 4.510 6.280 4.193 5.056 6.817 4.772 D31 3.824 10.476 38.417 3.094 9.669 37.467 [Lens group data] Group, starting surface, focal length G1 1 101.843 G2 6 -28.919 G3 11 -60.130 G4 14 45.188 G5 18 37.275 G6 26 -979.922 G7 30 -36.530 G8 32 180.299

[0151] Fig. 14(A) is a diagram showing various aberrations when the variable magnification optical system of Example 5 is focused at infinity in the wide-angle end state. Fig. 14(B) is a diagram showing various aberrations when the variable magnification optical system of Example 5 is focused at infinity in the telephoto end state. Fig. 15(A) is a diagram showing various aberrations when the variable magnification optical system of Example 5 is focused at a close distance in the wide-angle end state. Fig. 15(B) is a diagram showing various aberrations when the variable magnification optical system of Example 5 is focused at a close distance in the telephoto end state. It can be seen from the various aberration diagrams that the variable magnification optical system of Example 5 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state not only when focused at infinity but also when focused at a close distance.

[0152] (Sixth Example) Example 6 will be described with reference to FIGS. 16 to 18 and Table 6. FIG. 16 shows the lens configuration of a variable magnification optical system according to Example 6. The variable magnification optical system ZL(6) according to Example 6 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having positive refractive power, and an eighth lens group G8 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first to eighth lens groups G1 to G8 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. The aperture stop S is disposed between the second lens group G2 and the third lens group G3. When varying the magnification, the aperture stop S moves along the optical axis together with the third lens group G3.

[0153] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L11 with its convex surface facing the object side and a biconvex positive lens L12, and a positive meniscus lens L13 with its convex surface facing the object side.

[0154] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L21 with its convex surface facing the object side, a cemented positive lens consisting of a biconcave negative lens L22 and a biconvex positive lens L23, and a biconcave negative lens L24. The object-side lens surface of the negative meniscus lens L21 is aspheric.

[0155] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L31 with a convex surface facing the object side, a biconvex positive lens L32, and a negative meniscus lens L33 with a concave surface facing the object side. The object side surface of the positive meniscus lens L31 is aspherical.

[0156] The fourth lens group G4 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L41, and a cemented negative lens made up of a negative meniscus lens L42 with its convex surface facing the object side and a biconvex positive lens L43.

[0157] The fifth lens group G5 is composed of a negative meniscus lens L51 with its concave surface facing the object side.

[0158] The sixth lens group G6 is composed of a biconvex positive lens L61.

[0159] The seventh lens group G7 is composed of a positive meniscus lens L71 with its concave surface facing the object side. The positive meniscus lens L71 has an aspherical lens surface facing the image side.

[0160] The eighth lens group G8 is composed of, arranged in order from the object side along the optical axis, a biconcave negative lens L81 and a positive meniscus lens L82 with its convex surface facing the object side. An image surface I is located on the image side of the eighth lens group G8.

[0161] In this embodiment, the first lens group G1 constitutes the front lens group GA, which has positive refractive power. The second lens group G2 constitutes the first intermediate lens group GM1, which has negative refractive power. The third lens group G3 and the fourth lens group G4 constitute the second intermediate lens group GM2, which has positive refractive power as a whole. The fifth lens group G5, the sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 constitute the rear lens group GR, which has negative refractive power as a whole. When focusing from an object at infinity to a close object, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7, which constitute the rear lens group GR, move toward the object along the optical axis along different trajectories (movement amounts). In other words, the fifth lens group G5 corresponds to the first focusing lens group GF1, which is arranged closest to the object of the rear lens group GR. The sixth lens group G6 corresponds to the second focusing lens group GF2, which is another focusing lens group arranged closer to the image side than the first focusing lens group GF1, and the seventh lens group G7 corresponds to the third focusing lens group GF3, which is another focusing lens group arranged closer to the image side than the first focusing lens group GF1.

[0162] Table 6 below lists the values ​​of the specifications of the variable magnification optical system according to the sixth example.

[0163] (Table 6) [Overall specifications] Magnification ratio=4.70 fM1w=-19.907 fM2w=32.581 MTF1=2.249 MTF2=2.096 βF1w=0.765 βF2w=0.949 βF1t=0.684 βF2t=0.943 fN=-37.608 fL=176.733 fRw=-190.173 WMT f 24.700 70.009 115.999 FNO 4.06 4.02 4.12 2ω 86.44 32.64 19.92 Ymax 21.60 21.60 21.60 TL 139.45 169.68 199.08 BF 12.344 33.226 39.472 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 462.2978 2.000 1.84666 23.80 2 117.9843 7.772 1.59319 67.90 3 -332.8090 0.200 4 68.5981 5.329 1.77250 49.62 5 140.6044 (D5) 6* 102.1762 1.500 1.74389 49.53 7 20.0193 7.301 8 -53.3166 1.000 1.59319 67.90 9 23.3630 6.829 1.68893 31.16 10 -34.9416 0.488 11 -29.8911 1.000 1.81600 46.59 12 771.9204 (D12) 13 ∞ 2.000 (Aperture S) 14* 64.5221 2.313 1.69343 53.30 15 218.6309 0.200 16 42.2294 5.148 1.59319 67.90 17 -50.9166 0.846 18 -38.4211 1.000 1.83481 42.73 19 -121.6787 (D19) 20 50.5091 4.565 1.59319 67.90 21 -73.4692 0.200 22 144.3902 1.000 1.81600 46.59 23 20.8080 7.069 1.49782 82.57 24 -58.5658 (D24) 25 -36.5746 1.000 1.90200 25.26 26 -88.6629 (D26) 27 78.2651 5.215 1.80400 46.60 28 -61.1685 (D28) 29 -115.4337 1.682 1.77387 47.25 30* -84.6141 (D30) 31 -93.1742 1.000 1.83481 42.73 32 47.5819 1.399 33 51.8920 2.458 1.94594 17.98 34 73.5164 BF Image plane ∞ [Aspherical surface] Page 6 κ=1.0000,A4=1.46132E-06,A6=-1.42920E-09,A8=2.79764E-12,A10=5.33710E-15 Page 14 κ=1.0000,A4=-3.76343E-06,A6=1.16052E-09,A8=-1.11309E-11,A10=1.96066E-14 Page 30 κ=1.0000,A4=9.30832E-06,A6=3.85397E-09,A8=-9.94633E-12,A10=2.27044E-14 [Can change the interval データ] Infinity focus state Close focus state WMTWMT D5 2.000 24.468 49.503 2.000 24.468 49.503 D12 20.478 3.818 2.074 20.478 3.818 2.074 D19 8.916 3.265 2.000 8.916 3.265 2.000 D24 6.612 13.356 22.504 5.023 11.937 20.255 D26 3.664 3.898 2.010 3.909 4.002 2.162 D28 3.789 9.856 8.781 4.421 10.371 9.746 D30 11.138 7.275 2.224 11.850 8.075 3.355 [Lens group data] Group starting plane focal length G1 1 134.376 G2 6 -19.907 G3 14 53.036 G4 20 55.179 G5 25 -69.654 G6 27 43.428 G7 29 399.999 G8 31 -47.335

[0164] Fig. 17(A) is a diagram showing various aberrations when the variable magnification optical system of Example 6 is in the wide-angle end state and focusing on infinity. Fig. 17(B) is a diagram showing various aberrations when the variable magnification optical system of Example 6 is in the telephoto end state and focusing on infinity. Fig. 18(A) is a diagram showing various aberrations when the variable magnification optical system of Example 6 is in the wide-angle end state and focusing on a close distance. Fig. 18(B) is a diagram showing various aberrations when the variable magnification optical system of Example 6 is in the telephoto end state and focusing on a close distance. It can be seen from the various aberration diagrams that the variable magnification optical system of Example 6 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state not only when focusing on infinity but also when focusing on a close distance.

[0165] (Seventh Example) Example 7 will be described with reference to FIGS. 19 to 21 and Table 7. FIG. 19 shows the lens configuration of a variable magnification optical system according to Example 7. The variable magnification optical system ZL(7) according to Example 7 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having positive refractive power, and an eighth lens group G8 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first to eighth lens groups G1 to G8 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. The aperture stop S is disposed between the second lens group G2 and the third lens group G3. When varying the magnification, the aperture stop S moves along the optical axis together with the third lens group G3.

[0166] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented positive lens consisting of a negative meniscus lens L11 with its convex surface facing the object side and a biconvex positive lens L12, and a positive meniscus lens L13 with its convex surface facing the object side.

[0167] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a cemented positive lens consisting of a biconcave negative lens L22 and a biconvex positive lens L23, and a plano-concave negative lens L24 with a flat surface facing the image side. The object-side lens surface of the negative meniscus lens L21 is aspheric.

[0168] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L31 and a biconvex positive lens L32. The object side surface of the positive lens L31 is aspherical.

[0169] The fourth lens group G4 is composed of a biconcave negative lens L41.

[0170] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L51, and a cemented positive lens consisting of a negative meniscus lens L52 with its convex surface facing the object side and a biconvex positive lens L53.

[0171] The sixth lens group G6 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L61 with its concave surface facing the object side, and a biconvex positive lens L62.

[0172] The seventh lens group G7 is composed of a positive meniscus lens L71 with its concave surface facing the object side. The positive meniscus lens L71 has an aspherical lens surface facing the image side.

[0173] The eighth lens group G8 is composed of, arranged in order from the object side along the optical axis, a biconcave negative lens L81 and a positive meniscus lens L82 with its convex surface facing the object side. An image surface I is located on the image side of the eighth lens group G8.

[0174] In this embodiment, the first lens group G1 constitutes the front lens group GA, which has positive refractive power. The second lens group G2 constitutes the first intermediate lens group GM1, which has negative refractive power. The third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the second intermediate lens group GM2, which has positive refractive power as a whole. The sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 constitute the rear lens group GR, which has negative refractive power as a whole. When focusing from an object at infinity to a close object, the sixth lens group G6 and the seventh lens group G7, which constitute the rear lens group GR, move toward the object along the optical axis along different trajectories (movement amounts). In other words, the sixth lens group G6 corresponds to the first focusing lens group GF1, which is arranged closest to the object of the rear lens group GR. The seventh lens group G7 corresponds to the second focusing lens group GF2, which is another focusing lens group arranged closer to the image side than the first focusing lens group GF1.

[0175] Table 7 below lists the values ​​of the specifications of the variable magnification optical system according to the seventh example.

[0176] (Table 7) [Overall specifications] Magnification ratio=4.56 fM1w=-20.363 fM2w=33.345 MTF1=1.381 MTF2=0.984 βF1w=0.763 βF2w=0.948 βF1t=0.650 βF2t=0.940 fN=-30.226 fL=100.683 fRw=-177.170 WMT f 22.600 70.004 103.000 FNO 4.09 4.09 4.08 2ω 91.56 33.96 22.38 Ymax 21.60 21.60 21.60 TL 139.45 165.05 199.45 BF 11.779 38.577 39.906 [Lens specifications] Surface number RD nd νd Object plane ∞ 1 6659.3699 2.000 1.84666 23.80 2 195.3556 6.352 1.59319 67.90 3 -273.7600 0.200 4 73.6739 4.876 1.77250 49.62 5 149.1863 (D5) 6* 113.0230 1.500 1.74389 49.53 7 19.5406 7.132 8 -63.0618 1.000 1.59319 67.90 9 24.3284 6.267 1.68893 31.16 10 -43.5952 0.573 11 -34.2926 1.000 1.81600 46.59 12∞ (D12) 13 ∞ 2.000 (Aperture S) 14* 57.8680 3.090 1.69343 53.30 15 -302.2108 0.200 16 48.4547 4.785 1.59319 67.90 17 -53.3050 (D17) 18 -38.1755 1.000 1.83481 42.730 19 616.7068 (D19) 20 42.1940 4.851 1.59319 67.90 21 -69.0643 0.200 22 98.4698 1.000 1.81600 46.59 23 19.6428 7.597 1.49782 82.57 24 -56.1321 (D24) 25 -29.3608 1.000 1.90200 25.26 26 -58.1915 1.995 27 90.0589 5.380 1.80400 46.60 28 -48.9540 (D28) 29 -85.0115 1.709 1.77387 47.25 30* -65.3126 (D30) 31 -62.1123 1.000 1.83481 42.73 32 42.8077 3.227 33 69.1642 3.143 1.94594 17.98 34 247.0342 BF Image plane ∞ [Aspherical surface] Page 6 κ=1.0000,A4=2.33500E-06,A6=-8.92215E-10,A8=-3.76442E-12,A10=9.61354E-15 Page 14 κ=1.0000,A4=-2.41342E-06,A6=1.12249E-09A8=-3.73343E-13,A10=-1.07003E-14 Page 30 κ=1.0000,A4=9.05002E-06,A6=4.53686E-10,A8=5.24788E-12,A10=-1.61841E-14 [Variable Interval Data] Infinity focus Close focus WMTWMT D5 2.000 17.263 50.507 2.000 17.263 50.507 D12 22.632 2.617 2.000 22.632 2.617 2.000 D17 2.327 2.925 2.897 2.327 2.925 2.897 D19 10.846 2.372 2.000 10.846 2.372 2.000 D24 5.406 14.281 18.351 4.526 13.387 16.970 D28 2.000 8.343 8.382 2.443 8.546 8.779 D30 9.389 5.598 2.334 9.827 6.289 3.318 [Lens group data] Group starting plane focal length G1 1 153.821 G2 6 -20.363 G3 14 27.666 G4 18 -43.034 G5 20 44.173 G6 25 84.579 G7 29 350.941 G8 31 -44.997

[0177] Fig. 20(A) is a diagram showing various aberrations of the variable magnification optical system of Example 7 when focusing at infinity in the wide-angle end state. Fig. 20(B) is a diagram showing various aberrations of the variable magnification optical system of Example 7 when focusing at infinity in the telephoto end state. Fig. 21(A) is a diagram showing various aberrations of the variable magnification optical system of Example 7 when focusing at close range in the wide-angle end state. Fig. 21(B) is a diagram showing various aberrations of the variable magnification optical system of Example 7 when focusing at close range in the telephoto end state. It can be seen from the various aberration diagrams that the variable magnification optical system of Example 7 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state not only when focusing at infinity but also when focusing at close range.

[0178] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below: This table shows the values ​​corresponding to each of the conditional expressions (1) to (18) for all the examples (Examples 1 to 7). Condition (1) -6.00 <fFs / fw<6.00 Condition (2) 2.00 <f1 / fw<8.00 Condition (3) 0.10 <BFw / fw<1.00 Conditional expression (4) 0.20<|fFs| / f1<2.00 Conditional expression (5) 1.50<|fFs| / (-fM1w)<5.00 Conditional expression (6) 0.90<|fFs| / fM2w<4.00 Condition (7) 0.20 <f1 / (-fRw)<5.00 Condition (8) 0.10 <MTF1 / MTF2<3.00 Conditional expression (9) 0.10<βF1w / βF2w<3.00 Conditional expression (10) 0.10<βF1t / βF2t<3.00 Condition (11) 0.50<βF1w<2.60 Conditional expression (12) 0.20<βF2w<1.80 Conditional expression (13) {βF1w+(1 / βF1w)} -2 ≦0.25 Conditional expression (14) {βF2w+(1 / βF2w)} -2 ≦0.25 Conditional expression (15) 0.10<|fFs| / |fRF|<4.00 Conditional expression (16) 2ωw>75.0° Condition (17) ft / fw>3.50 Conditional expression (18) 0.10<(-fN) / fL<1.00

[0179] [Conditional Expression Corresponding Values] (First to Fourth Examples) Conditional Expression 1st Example 2nd Example 3rd Example 4th Example (1) -1.547 -1.279 3.722 -1.457 (2) 3.932 4.500 6.953 4.181 (3) 0.555 0.464 0.507 0.504 (4) 0.393 0.284 0.535 0.349 (5) 2.165 1.852 4.005 2.010 (6) 1.281 1.087 2.511 1.208 (7) 2.094 1.822 0.991 2.321 (8) 0.407 0.284 1.442 0.432 (9) 0.679 0.626 0.807 0.644 (10) 0.359 0.263 0.695 0.282 (11) 1.071 1.045 0.770 1.005 (12) 1.577 1.670 0.954 1.561 (13) 0.249 0.250 0.234 0.250 (14) 0.205 0.194 0.249 0.206 (15) 0.296 0.402 1.922 0.211 (16) 85.22 85.22 91.54 85.20 (17) 4.737 4.737 4.558 7.854 (18) 0.296 0.402 0.303 0.211 [Conditional Expression Corresponding Values] (Fifth to Seventh Examples) Conditional Expression 5th Example 6th Example 7th Example (1) -1.479 1.758 3.742 (2) 4.123 5.440 6.806 (3) 0.504 0.500 0.521 (4) 0.359 0.323 0.550 (5) 2.112 2.182 4.154 (6) 1.246 1.333 2.537 (7) 2.280 0.707 0.868 (8) 0.391 1.073 1.403 (9) 0.647 0.806 0.805 (10) 0.283 0.725 0.692 (11) 1.002 0.765 0.763 (12) 1.550 0.949 0.948 (13) 0.250 0.233 0.233 (14) 0.208 0.249 0.249 (15) 0.203 0.917 1.880 (16) 85.20 86.44 91.56 (17) 7.854 4.696 4.558 (18) 0.203 0.213 0.300

[0180] According to each of the above embodiments, by making the focusing lens group smaller and lighter, quiet and high-speed focusing can be achieved without increasing the size of the lens barrel. Also, it is possible to realize a variable magnification optical system with little aberration fluctuation when changing magnification from the wide-angle end state to the telephoto end state and when focusing from an object at infinity to a close object.

[0181] The above-described examples are merely illustrative examples of the present invention, and the present invention is not limited to these.

[0182] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the variable magnification optical system of this embodiment.

[0183] Although seven-group and eight-group configurations have been shown as examples of the variable magnification optical system of this embodiment, the present application is not limited to these, and variable magnification optical systems with other group configurations (for example, nine groups) can also be configured. Specifically, a lens or lens group may be added to the most object-side or most image-plane-side of the variable magnification optical system of this embodiment. Note that a lens group refers to a portion having at least one lens separated by an air gap that changes when the magnification is changed.

[0184] A single lens group, multiple lens groups, or a partial lens group may be moved in the optical axis direction to function as a focusing lens group that focuses from an object at infinity to a close object. The focusing lens group can also be used for autofocusing, and is suitable for driving a motor (using an ultrasonic motor, etc.) for autofocusing.

[0185] The lens group or partial lens group may be moved so as to have a component in a direction perpendicular to the optical axis, or may be rotated (oscillated) in a plane including the optical axis, to serve as an image stabilization lens group that corrects image blur caused by camera shake.

[0186] The lens surface may be spherical, flat, or aspherical. Spherical or flat lens surfaces are preferred because they facilitate lens processing and assembly adjustment, and prevent degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, they are preferred because they minimize degradation of imaging performance even when the image plane is misaligned.

[0187] If the lens surface is aspherical, the aspherical surface may be any of the following: a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, or a hybrid aspherical surface in which a resin is formed into an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, or the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0188] It is preferable that the aperture diaphragm be located between the second and third lens groups, or between the third and fourth lens groups, but it is also possible to use the lens frame as a substitute for an aperture diaphragm member.

[0189] Each lens surface may be coated with an anti-reflection coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high-contrast optical performance. [Explanation of symbols]

[0190] G1 First lens group G2 Second 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 has a front lens group having positive refractive power, a first intermediate lens group having negative refractive power, a second intermediate lens group having positive refractive power, and a rear lens group, which are arranged in this order from the object side along the optical axis, When changing magnification, the spacing between adjacent lens groups changes, the subsequent lens group includes a first focusing lens group that is arranged closest to the object of the subsequent lens group and moves along the optical axis during focusing, and at least one other focusing lens group that is arranged closer to the image than the first focusing lens group and moves along the optical axis along a locus different from that of the first focusing lens group during focusing, the second intermediate lens group includes at least one lens group having positive refractive power; A variable magnification optical system that satisfies the following condition: -6.00<fFs / fw<6.00 where fFs is the focal length of the focusing lens group having the strongest refractive power among the focusing lens groups included in the subsequent lens group. fw: focal length of the variable magnification optical system in the wide-angle end state

2. 2. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 2.00<f1 / fw<8.00 where f1 is the focal length of the front lens group

3. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.10<BFw / fw<1.00 where BFw is the back focus of the variable magnification optical system in the wide-angle end state.

4. 4. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.20<|fFs| / f1<2.00 where f1 is the focal length of the front lens group

5. 5. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 1.50<|fFs| / (-fM1w)<5.00 where fM1w is the focal length of the first intermediate lens group in the wide-angle end state.

6. 6. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.90<|fFs| / fM2w<4.00 where fM2w is the focal length of the two intermediate lens groups in the wide-angle end state.

7. 7. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.20<f1 / (-fRw)<5.00 where f1 is the focal length of the front lens group fRw: focal length of the subsequent lens group in the wide-angle end state

8. 8. The variable magnification optical system according to claim 1, wherein the front lens group is composed of one lens group having positive refractive power.

9. the first intermediate lens group is composed of one lens group having negative refractive power or two lens groups having negative refractive power; 9. The variable magnification optical system according to claim 1.

10. the second intermediate lens group is composed of two lens groups having positive refractive power, or two lens groups having positive refractive power and one lens group having negative refractive power; 10. The variable magnification optical system according to claim 1.

11. 11. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.10<MTF1 / MTF2<3.00 However, MTF1: absolute value of the movement amount of the first focusing lens group MTF2: Absolute value of the movement amount of the focusing lens group that is closest to the first focusing lens group among the other focusing lens groups

12. 12. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.10<βF1w / βF2w<3.00 where βF1w is the lateral magnification of the first focusing lens group when focused on an object at infinity in the wide-angle end state. βF2w: lateral magnification of the focusing lens group that is closest to the first focusing lens group among the other focusing lens groups when focusing on an object at infinity in the wide-angle end state

13. 13. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.10<βF1t / βF2t<3.00 where βF1t is the lateral magnification when the first focusing lens group is in the telephoto end state and focused on an object at infinity. βF2t: lateral magnification of the focusing lens group that is closest to the first focusing lens group among the other focusing lens groups when focusing on an object at infinity in the telephoto end state

14. 14. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.50<βF1w<2.60 where βF1w is the lateral magnification of the first focusing lens when focused on an object at infinity in the wide-angle end state.

15. 15. The variable magnification optical system according to claim 1, which satisfies the following condition: 0.20<βF2w<1.80 where βF2w is the lateral magnification of the focusing lens group that is closest to the first focusing lens group among the other focusing lens groups when focusing on an object at infinity in the wide-angle end state.

16. 16. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: {βF1w+(1 / βF1w)} -2 ≦0.25 where βF1w is the lateral magnification of the first focusing lens when focused on an object at infinity in the wide-angle end state.

17. 17. The variable magnification optical system according to claim 1, which satisfies the following condition: {βF2w+(1 / βF2w)} -2 ≦0.25 where βF2w is the lateral magnification of the focusing lens group that is closest to the first focusing lens group among the other focusing lens groups when focusing on an object at infinity in the wide-angle end state.

18. 18. A variable magnification optical system according to claim 1, which satisfies the following condition: 0.10<|fFs| / |fRF|<4.00 where fRF is the focal length of the lens group arranged adjacent to the focusing lens group closest to the image side among the focusing lens groups included in the subsequent lens group.

19. 19. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 2ωw>75.0° where 2ωw is the total angle of view of the variable magnification optical system in the wide-angle end state.

20. 20. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: ft / fw>3.50 where ft is the focal length of the variable magnification optical system in the telephoto end state.

21. 21. The variable magnification optical system according to claim 1, which satisfies the following condition: 0.10<(-fN) / fL<1.00 where fN is the focal length of the second lens element counting from the image side of the variable magnification optical system. fL: focal length of the lens located closest to the image side in the variable magnification optical system

22. An optical instrument comprising the variable magnification optical system according to any one of claims 1 to 21.

Images