Scaling optical system, optical device, and manufacturing method of scaling optical system

Abstract

To provide a scaling optical system having excellent optical performance while realizing miniaturization and reduced weight.SOLUTION: A scaling optical system (ZL) has 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, and a fifth lens group (G5) having negative refractive power lined up in sequence from an object side along a light axis, the interval between the respective, adjacent lens groups is changed in scaling, the fourth lens group (G4) is a focusing lens group traveling along a light axis at the time of focusing, and the following conditional expression is satisfied, namely 0.11<f4 / f5<0.70, where f4 is a focal length of the fourth lens group (G4) and f5 is a focal length of the fifth lens group (G5).SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-228808 Summary of the Invention

[0004] A first variable power optical system according to the present invention has, arranged in order from the object side along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power, wherein the spacing between adjacent lens groups changes during variable power, and the fourth lens group is a focusing lens group that moves along the optical axis during focusing, and satisfies the following conditional expression: 0.11 <f4 / f5<0.70 where f4 is the focal length of the fourth lens group f5: focal length of the fifth lens group

[0005] A second variable power optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group having at least one lens group and having positive refractive power, a focusing lens group having negative refractive power, and a rear group having at least one lens group, wherein the spacing between adjacent lens groups changes during variable power, and the focusing lens group moves along the optical axis during focusing, and the following conditional expression is satisfied: 0.30<(-f2) / fMt<0.80 0.01 <Bfw / fw<0.95 where f2 is the focal length of the second lens group fMt: focal length of the intermediate group in the telephoto end state Bfw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state

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

[0007] The method for manufacturing a variable magnification optical system according to the present invention is a method for manufacturing a variable magnification optical system having, arranged in order from the object side along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power, wherein the spacing between adjacent lens groups changes during magnification variation, and the fourth lens group is a focusing lens group that moves along the optical axis during focusing, and wherein each lens is arranged within the lens barrel so as to satisfy the following conditional expression: 0.11 <f4 / f5<0.70 where f4 is the focal length of the fourth lens group f5: focal length of the fifth lens group [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing the lens configuration of a variable magnification optical system according to Example 1. [Figure 2]2A and 2B are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 3] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 2. [Figure 4] 4A and 4B are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 5] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 3. [Figure 6] 6A and 6B are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 7] FIG. 10 is a diagram showing the lens configuration of a variable magnification optical system according to Example 4. [Figure 8] 8A and 8B are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focused on infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 9] 1 is a diagram showing the configuration of a camera equipped with a variable magnification optical system according to each embodiment. [Figure 10] 4 is a flowchart showing a method for manufacturing a variable magnification optical system according to the first embodiment. [Figure 11] 10 is a flowchart showing a method for manufacturing a variable magnification optical system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present invention will now be described. First, a camera (optical device) equipped with a variable magnification optical system according to each embodiment will be described with reference to FIG. 9. As shown in FIG. 9, this camera 1 is composed of a main body 2 and a photographic lens 3 attached to the main body 2. The main body 2 is equipped with an image sensor 4, a main body control unit (not shown) that controls the operation of the digital camera, and an LCD screen 5. The photographic lens 3 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.

[0010] 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. 9 is a schematic representation of a variable magnification optical system provided in the photographing lens 3, and the lens configuration of the variable magnification optical system ZL is not limited to this configuration.

[0011] Next, a variable magnification optical system according to the first embodiment will be described. 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 the first embodiment is configured to include, 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, and a fifth lens group G5 having negative refractive power. When varying magnification, the spacing between adjacent lens groups changes. The fourth lens group G4 is a focusing lens group GF that moves along the optical axis during focusing.

[0012] With the above-described configuration, the variable-magnification optical system ZL according to the first embodiment satisfies the following conditional expression (1). 0.11 <f4 / f5<0.70 ···(1) However, f4: focal length of the fourth lens group G4 f5: Focal length of the fifth lens group G5

[0013] According to the first embodiment, it is possible to obtain a variable magnification optical system that is small and lightweight while having good optical performance, and an optical device equipped with this variable magnification optical system. The variable magnification optical system ZL according to the first embodiment may be the variable magnification optical system ZL(2) shown in Figure 3 or the variable magnification optical system ZL(3) shown in Figure 5.

[0014] Conditional expression (1) defines an appropriate relationship between the focal length of the fourth lens group G4 and the focal length of the fifth lens group G5. By satisfying conditional expression (1), spherical aberration, coma, and curvature of field can be effectively corrected.

[0015] If the corresponding value of conditional expression (1) exceeds the upper limit, the focal length of the fourth lens group G4 becomes longer, which increases the amount of movement of the fourth lens group G4, which is the focusing lens group, during focusing, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature during focusing. Furthermore, the focal length of the fifth lens group G5 becomes shorter, making it difficult to correct field curvature that occurs in the fifth lens group G5. Setting the upper limit of conditional expression (1) to 0.65, or even 0.60, can further ensure the effects of this embodiment.

[0016] If the corresponding value of conditional expression (1) falls below the lower limit, the focal length of the fourth lens group G4 becomes short, making it difficult to correct spherical aberration, coma, and field curvature that occur in the fourth lens group G4. Furthermore, if the focal length of the fifth lens group G5 becomes long, the effect of correcting field curvature by the fifth lens group G5 becomes small, making it difficult to obtain good optical performance. Setting the lower limit of conditional expression (1) to 0.15, or even 0.20, can further ensure the effects of this embodiment.

[0017] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (2). 0.01<(-f4) / f3<5.00 (2) However, f3 is the focal length of the third lens group G3.

[0018] Conditional expression (2) defines an appropriate relationship between the focal length of the fourth lens group G4 and the focal length of the third lens group G3. By satisfying conditional expression (2), spherical aberration, coma, and curvature of field can be effectively corrected.

[0019] If the corresponding value of conditional expression (2) exceeds the upper limit, the focal length of the fourth lens group G4 becomes longer, which increases the amount of movement of the fourth lens group G4, which is the focusing lens group, during focusing, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature during focusing. Furthermore, if the focal length of the third lens group G3 becomes shorter, it becomes difficult to correct the spherical aberration and coma that occur in the third lens group G3. The effects of this embodiment can be further ensured by setting the upper limit of conditional expression (2) to 4.50, 4.20, 3.90, 3.50, 3.00, 2.75, 2.50, or even 2.30.

[0020] If the value corresponding to conditional expression (2) falls below the lower limit, the focal length of the fourth lens group G4 becomes short, making it difficult to correct the spherical aberration, coma, and curvature of field that occur in the fourth lens group G4. Furthermore, if the focal length of the third lens group G3 becomes long, the amount of movement of the third lens group G3 during zooming increases, making it difficult to suppress fluctuations in spherical aberration and coma during zooming. Setting the lower limit of conditional expression (2) to 0.05, 1.00, 1.25, or even 1.50 further ensures the effects of this embodiment.

[0021] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (3). 0.01 <f3 / (-f5)<1.00 ···(3) However, f3 is the focal length of the third lens group G3.

[0022] Conditional expression (3) defines an appropriate relationship between the focal length of the third lens group G3 and the focal length of the fifth lens group G5. By satisfying conditional expression (3), spherical aberration, coma, and curvature of field can be effectively corrected.

[0023] If the corresponding value of conditional expression (3) exceeds the upper limit, the focal length of the third lens group G3 becomes longer, which increases the amount of movement of the third lens group G3 during zooming, making it difficult to suppress fluctuations in spherical aberration and coma during zooming. Furthermore, the focal length of the fifth lens group G5 becomes shorter, making it difficult to correct curvature of field that occurs in the fifth lens group G5. Setting the upper limit of conditional expression (3) to 0.75, 0.50, 0.29, or even 0.25 can further enhance the effects of this embodiment.

[0024] If the value corresponding to conditional expression (3) falls below the lower limit, the focal length of the third lens group G3 becomes short, making it difficult to correct spherical aberration and coma aberration that occur in the third lens group G3. Also, if the focal length of the fifth lens group G5 becomes long, the effect of correcting field curvature by the fifth lens group G5 becomes small, making it difficult to obtain good optical performance. By setting the lower limit of conditional expression (3) to 0.05, or even 0.09, the effects of this embodiment can be further ensured.

[0025] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (4). 0.01 <f3 / (-f45t)<2.00 ···(4) However, f3 is the focal length of the third lens group G3. f45t: The combined focal length of the fourth lens group G4 and the fifth lens group G5 at the telephoto end

[0026] Conditional expression (4) defines an appropriate relationship between the focal length of the third lens group G3 and the combined focal length of the fourth lens group G4 and the fifth lens group G5 at the telephoto end. By satisfying conditional expression (4), spherical aberration, coma, and field curvature can be effectively corrected.

[0027] If the value corresponding to conditional expression (4) exceeds the upper limit, the focal length of the third lens group G3 becomes longer, which increases the amount of movement of the third lens group G3 during zooming, making it difficult to suppress fluctuations in spherical aberration and coma during zooming. Furthermore, the combined focal length of the fourth lens group G4 and the fifth lens group G5 at the telephoto end state becomes shorter, making it difficult to correct the spherical aberration, coma, and field curvature that occur in the fourth lens group G4 and the fifth lens group G5. Setting the upper limit of conditional expression (4) to 1.75, 1.50, 1.25, 0.90, or even 0.76 can further enhance the effects of this embodiment.

[0028] If the value corresponding to conditional expression (4) falls below the lower limit, the focal length of the third lens group G3 becomes shorter, making it difficult to correct the spherical aberration and coma aberration that occur in the third lens group G3. Furthermore, if the combined focal length of the fourth lens group G4 and the fifth lens group G5 at the telephoto end state becomes longer, the movement amount of the fourth lens group G4 and the fifth lens group G5 during zooming increases, making it difficult to suppress fluctuations in spherical aberration, coma aberration, and field curvature during zooming. Setting the lower limit of conditional expression (4) to 0.10, 0.25, 0.33, 0.45, or even 0.56 can further enhance the effects of this embodiment.

[0029] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (5). 0.01<β5t / β5w<2.00 (5) β5t: lateral magnification of the fifth lens group G5 in the telephoto end state β5w: Lateral magnification of the fifth lens group G5 at the wide-angle end

[0030] Conditional expression (5) defines an appropriate relationship between the lateral magnification of the fifth lens group G5 in the telephoto end state and the lateral magnification of the fifth lens group G5 in the wide-angle end state. Satisfying conditional expression (5) is preferable because it results in a variable-magnification optical system that is compact and lightweight while also providing excellent optical performance. Setting the upper limit of conditional expression (5) to 1.80, 1.65, 1.55, 1.49, or even 1.30 can further enhance the effects of this embodiment. Setting the lower limit of conditional expression (5) to 0.10, 0.25, 0.50, 0.75, 0.90, or even 1.07 can further enhance the effects of this embodiment.

[0031] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (6). 0.01 <Bfw / fw<0.95 ···(6) Bfw: back focus of the variable magnification optical system ZL in the wide-angle end state fw: focal length of variable magnification optical system ZL at wide-angle end

[0032] Conditional expression (6) 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. In each embodiment, the back focus of the variable magnification optical system ZL is the air-equivalent distance on the optical axis from the lens surface of the variable magnification optical system ZL closest to the image plane to the image plane I. Satisfying conditional expression (6) is preferable because it allows for a variable magnification optical system that is compact and lightweight while also providing excellent optical performance. Setting the upper limit of conditional expression (6) to 0.90, 0.85, 0.80, 0.78, 0.75, 0.65, or even 0.58 can further enhance the effects of this embodiment. Setting the lower limit of conditional expression (6) to 0.10, 0.30, 0.40, or even 0.50 can further enhance the effects of this embodiment.

[0033] In the variable magnification optical system ZL according to the first embodiment, it is desirable that the fifth lens group G5 consists of two lenses, which makes it possible to effectively suppress fluctuations in field curvature during magnification.

[0034] In the variable magnification optical system ZL according to the first embodiment, it is desirable that the third lens group G3 has a lens that satisfies the following conditional expression (7). 75.00<ν3L ···(7) where ν3L is the Abbe number of the lens in the third lens group G3

[0035] Conditional expression (7) defines an appropriate range for the Abbe number of the lens in the third lens group G3. If the third lens group G3 includes a lens that satisfies conditional expression (7), a variable magnification optical system with good optical performance and corrected chromatic aberration can be obtained, which is preferable. By setting the lower limit of conditional expression (7) to 77.00, 80.00, or even 82.00, the effects of this embodiment can be further ensured.

[0036] In the variable magnification optical system ZL according to the first embodiment, it is desirable that the third lens group G3 includes a vibration reduction group GVR as part of the third lens group G3, which is movable so as to have a displacement component in a direction perpendicular to the optical axis. This is desirable because it allows for a variable magnification optical system that is compact and lightweight while also having good vibration reduction performance.

[0037] It is desirable that the variable magnification optical system ZL according to the first embodiment satisfy the following conditional expression (8). 0.01 <f3 / fVR<2.00 ···(8) However, f3 is the focal length of the third lens group G3. fVR: Focal length of the vibration isolation group GVR

[0038] Conditional expression (8) defines an appropriate relationship between the focal length of the third lens group G3 and the focal length of the image stabilization group GVR. By satisfying conditional expression (8), decentering coma and asymmetric curvature of field can be suppressed when correcting image blur, thereby achieving good image stabilization performance.

[0039] If the corresponding value of conditional expression (8) exceeds the upper limit, the focal length of the image stabilization group GVR becomes short, making it difficult to suppress decentering coma and asymmetric curvature of field that occur in the image stabilization group GVR when correcting image blur. By setting the upper limit of conditional expression (8) to 1.75, 1.50, 1.25, or even 1.00, the effects of this embodiment can be made more certain.

[0040] If the corresponding value of conditional expression (8) falls below the lower limit, the focal length of the image stabilization group GVR becomes longer, which increases the amount of movement of the image stabilization group GVR when correcting image blur, making it difficult to suppress decentering coma and asymmetric field curvature. By setting the lower limit of conditional expression (8) to 0.10, 0.30, 0.40, or even 0.45, the effects of this embodiment can be further ensured.

[0041] In the variable magnification optical system ZL according to the first embodiment, it is desirable that the vibration reduction group GVR be positioned closest to the image plane of the third lens group G3, thereby achieving good vibration reduction performance while maintaining the optical performance of the variable magnification optical system.

[0042] Next, a variable magnification optical system according to a second 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 the second 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, an intermediate group GM having at least one lens group and having positive refractive power, a focusing lens group GF having negative refractive power, and a rear group GR having at least one lens group. When varying magnification, the spacing between adjacent lens groups changes. The focusing lens group GF moves along the optical axis during focusing.

[0043] With the above-described configuration, the variable magnification optical system ZL according to the second embodiment satisfies the following conditional expression (9) and the above-described conditional expression (6). 0.30<(-f2) / fMt<0.80 (9) 0.01 <Bfw / fw<0.95 ···(6) However, f2 is the focal length of the second lens group G2. fMt: focal length of the middle group GM at the telephoto end Bfw: Back focus of variable magnification optical system ZL at the wide-angle end fw: focal length of variable magnification optical system ZL at wide-angle end

[0044] According to the second embodiment, it is possible to obtain a variable magnification optical system that is small and lightweight and has good optical performance, and an optical device equipped with this variable magnification optical system. The variable magnification optical system ZL according to the second embodiment may be the variable magnification optical system ZL(2) shown in Fig. 3, the variable magnification optical system ZL(3) shown in Fig. 5, or the variable magnification optical system ZL(4) shown in Fig. 7.

[0045] Condition (9) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the middle group GM at the maximum telephoto position. By satisfying condition (9), spherical aberration, coma, curvature of field, and other aberrations can be effectively corrected.

[0046] If the value corresponding to conditional expression (9) exceeds the upper limit, the focal length of the second lens group G2 becomes longer, which increases the amount of movement of the second lens group G2 during zooming, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature during zooming. Furthermore, the focal length of the middle group GM in the maximum telephoto state becomes shorter, making it difficult to correct the spherical aberration and coma that occur in the middle group GM. Setting the upper limit of conditional expression (9) to 0.75, or even 0.70, can further ensure the effects of this embodiment.

[0047] If the corresponding value of conditional expression (9) falls below the lower limit, the focal length of the second lens group G2 becomes shorter, making it difficult to correct the spherical aberration, coma, and curvature of field that occur in the second lens group G2. Furthermore, if the focal length of the middle group GM in the telephoto end state becomes longer, the amount of movement of the middle group GM during zooming increases, making it difficult to suppress fluctuations in spherical aberration and coma during zooming. Setting the lower limit of conditional expression (9) to 0.40, or even 0.50, can further ensure the effects of this embodiment.

[0048] As described above, conditional expression (6) 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. Satisfying conditional expression (6) is preferable because it results in a variable magnification optical system that is compact and lightweight while also having excellent optical performance. Setting the upper limit of conditional expression (6) to 0.90, 0.85, 0.80, 0.78, 0.75, 0.65, or even 0.58 can further enhance the effects of this embodiment. Setting the lower limit of conditional expression (6) to 0.10, 0.30, 0.40, or even 0.50 can further enhance the effects of this embodiment.

[0049] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (10). 0.01<(-fF) / fMt<5.00 (10) where fF is the focal length of the focusing lens group GF

[0050] Condition (10) defines an appropriate relationship between the focal length of the focusing lens group GF and the focal length of the middle lens group GM at the maximum telephoto position. By satisfying condition (10), spherical aberration, coma, and curvature of field can be effectively corrected.

[0051] If the value corresponding to conditional expression (10) exceeds the upper limit, the focal length of the focusing lens group GF becomes longer, which increases the amount of movement of the focusing lens group GF during focusing, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature during focusing. Furthermore, the focal length of the middle group GM in the maximum telephoto state becomes shorter, making it difficult to correct the spherical aberration and coma that occur in the middle group GM. Setting the upper limit of conditional expression (10) to 4.50, 4.00, 3.50, 3.00, or even 2.30 can further enhance the effects of this embodiment.

[0052] If the corresponding value of conditional expression (10) falls below the lower limit, the focal length of the focusing lens group GF becomes short, making it difficult to correct spherical aberration, coma, and field curvature that occur in the focusing lens group GF. Furthermore, if the focal length of the middle lens group GM in the maximum telephoto state becomes long, the amount of movement of the middle lens group GM during zooming increases, making it difficult to suppress fluctuations in spherical aberration and coma during zooming. The effects of this embodiment can be further enhanced by setting the lower limit of conditional expression (10) to 0.10, 0.50, 0.70, 1.00, 1.25, or even 1.50.

[0053] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (11). 0.01 <fMt / |fRt|<1.00 ···(11) where fRt is the focal length of the rear group GR at the telephoto end

[0054] Conditional expression (11) defines an appropriate relationship between the focal length of the middle group GM at the maximum telephoto position and the focal length of the rear group GR at the maximum telephoto position. By satisfying conditional expression (11), spherical aberration, coma, and curvature of field can be effectively corrected.

[0055] If the corresponding value of conditional expression (11) exceeds the upper limit, the focal length of the middle group GM in the maximum telephoto state becomes longer, which increases the amount of movement of the middle group GM during zooming, making it difficult to suppress fluctuations in spherical aberration and coma during zooming. Furthermore, the focal length of the rear group GR in the maximum telephoto state becomes shorter, making it difficult to correct curvature of field that occurs in the rear group GR. The effects of this embodiment can be further enhanced by setting the upper limit of conditional expression (11) to 0.85, 0.70, 0.60, 0.50, 0.35, or even 0.25.

[0056] If the corresponding value of conditional expression (11) falls below the lower limit, the focal length of the middle group GM in the maximum telephoto state becomes short, making it difficult to correct spherical aberration and coma that occur in the middle group GM. Furthermore, if the focal length of the rear group GR in the maximum telephoto state becomes long, the effect of correcting curvature of field by the rear group GR becomes small, making it difficult to obtain good optical performance. By setting the lower limit of conditional expression (11) to 0.03, or even 0.04, the effects of this embodiment can be further ensured.

[0057] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (12). 0.01<(-fF) / |fRt|<1.00 ···(12) where fF is the focal length of the focusing lens group GF fRt: focal length of rear group GR at telephoto end

[0058] Condition (12) defines the appropriate relationship between the focal length of the focusing lens group GF and the focal length of the rear group GR at the maximum telephoto position. By satisfying condition (12), spherical aberration, coma, and curvature of field can be effectively corrected.

[0059] If the value corresponding to conditional expression (12) exceeds the upper limit, the focal length of the focusing lens group GF becomes longer, which increases the amount of movement of the focusing lens group GF during focusing, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature during focusing. Furthermore, the focal length of the rear group GR becomes shorter in the telephoto end state, making it difficult to correct field curvature that occurs in the rear group GR. The effects of this embodiment can be further ensured by setting the upper limit of conditional expression (12) to 0.85, 0.75, 0.65, 0.60, or even 0.55.

[0060] If the value corresponding to conditional expression (12) falls below the lower limit, the focal length of the focusing lens group GF becomes short, making it difficult to correct spherical aberration, coma, and field curvature that occur in the focusing lens group GF. Furthermore, if the focal length of the rear group GR in the telephoto end state becomes long, the effect of correcting field curvature by the rear group GR becomes small, making it difficult to obtain good optical performance. Setting the lower limit of conditional expression (12) to 0.06, or even 0.075, can further ensure the effects of this embodiment.

[0061] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (13). 0.01 <fMt / (-fFRt)<1.00 ···(13) where fFRt is the composite focal length of at least one of the focusing lens group GF and the rear lens group GR in the telephoto end state.

[0062] Condition (13) defines the appropriate relationship between the focal length of the middle group GM at the maximum telephoto state and the combined focal length of at least one of the focusing lens group GF and the rear group GR at the maximum telephoto state. By satisfying condition (13), spherical aberration, coma, and curvature of field can be effectively corrected.

[0063] If the value corresponding to conditional expression (13) exceeds the upper limit, the focal length of the middle group GM in the maximum telephoto state becomes longer, which increases the amount of movement of the middle group GM during zooming, making it difficult to suppress fluctuations in spherical aberration and coma during zooming. Furthermore, if the combined focal length of at least one of the focusing lens group GF and rear group GR becomes shorter in the maximum telephoto state, it becomes difficult to correct spherical aberration, coma, and field curvature that occur in the lens group located closer to the image plane than the middle group GM. Setting the upper limit of conditional expression (13) to 0.90, or even 0.80, can further enhance the effects of this embodiment.

[0064] If the value corresponding to conditional expression (13) falls below the lower limit, the focal length of the middle group GM in the maximum telephoto state becomes short, making it difficult to correct the spherical aberration and coma that occur in the middle group GM. Furthermore, if the composite focal length of at least one of the focusing lens group GF and rear group GR in the maximum telephoto state becomes long, the amount of movement of the lens group located closer to the image plane than the middle group GM during zooming increases, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature during zooming. Setting the lower limit of conditional expression (13) to 0.10, 0.25, 0.35, or even 0.45 further enhances the effects of this embodiment.

[0065] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (14). 0.10<βRt / βRw<2.00 (14) βRt: Lateral magnification of rear group GR at telephoto end βRw: Lateral magnification of rear group GR at the wide-angle end

[0066] Conditional expression (14) defines an appropriate relationship between the lateral magnification of the rear group GR in the telephoto end state and the lateral magnification of the rear group GR in the wide-angle end state. Satisfying conditional expression (14) is preferable because it results in a variable-magnification optical system that is compact and lightweight while also having excellent optical performance. Setting the upper limit of conditional expression (14) to 1.80, 1.65, 1.50, 1.45, 1.35, or even 1.25 can further enhance the effects of this embodiment. Setting the lower limit of conditional expression (14) to 0.10, 0.25, 0.40, 0.50, or even 0.70 can further enhance the effects of this embodiment.

[0067] In the variable magnification optical system ZL according to the second embodiment, it is desirable that the rear group GR be made up of two lenses, which makes it possible to effectively suppress fluctuations in field curvature during magnification.

[0068] In the variable magnification optical system ZL according to the second embodiment, it is desirable that the middle group GM consists of one lens group, which is preferable because it allows for a variable magnification optical system that is compact and lightweight while also having good optical performance.

[0069] In the variable magnification optical system ZL according to the second embodiment, it is desirable that the rear group GR consists of one lens group, which is desirable because it allows for a variable magnification optical system that is compact and lightweight while also having good optical performance.

[0070] In the variable magnification optical system ZL according to the second embodiment, it is desirable that the rear group GR has negative refractive power, which is desirable because it allows for a variable magnification optical system that is small and lightweight while also having good optical performance.

[0071] In the variable magnification optical system ZL according to the second embodiment, it is desirable that the middle group GM has a lens that satisfies the following conditional expression (15). 75.00<νML ···(15) where νML is the Abbe number of the lens in the middle group GM

[0072] Conditional expression (15) defines an appropriate range for the Abbe number of the lens in the middle group GM. If the middle group GM includes a lens that satisfies conditional expression (15), a variable magnification optical system with good optical performance and corrected chromatic aberration can be obtained, which is preferable. By setting the lower limit of conditional expression (15) to 76.00, 77.50, 78.50, or even 80.00, the effects of this embodiment can be further ensured.

[0073] In the variable magnification optical system ZL according to the second embodiment, it is desirable that the intermediate group GM includes a vibration reduction group GVR as part of the intermediate group GM, which is movable so as to have a displacement component in a direction perpendicular to the optical axis, which is desirable because it allows for a variable magnification optical system that is compact and lightweight while also having good vibration reduction performance.

[0074] It is desirable that the variable magnification optical system ZL according to the second embodiment satisfy the following conditional expression (16). 0.01 <fMt / fVR<1.00 ···(16) where fVR is the focal length of the vibration reduction group GVR

[0075] Conditional expression (16) defines the appropriate relationship between the focal length of the middle group GM at the maximum telephoto position and the focal length of the image stabilization group GVR. By satisfying conditional expression (16), decentering coma and asymmetric curvature of field can be suppressed when correcting image blur, thereby achieving good image stabilization performance.

[0076] If the corresponding value of conditional expression (16) exceeds the upper limit, the focal length of the image stabilization group GVR becomes short, making it difficult to suppress decentering coma and asymmetric curvature of field that occur in the image stabilization group GVR when correcting image blur. By setting the upper limit of conditional expression (16) to 0.85, or even 0.75, the effects of this embodiment can be made even more certain.

[0077] If the corresponding value of conditional expression (16) falls below the lower limit, the focal length of the image stabilization group GVR becomes longer, which increases the amount of movement of the image stabilization group GVR when correcting image blur, making it difficult to suppress decentering coma and asymmetric field curvature. By setting the lower limit of conditional expression (16) to 0.10, 0.25, 0.45, or even 0.60, the effects of this embodiment can be further ensured.

[0078] In the variable magnification optical system ZL according to the second embodiment, it is desirable that the vibration reduction group GVR be positioned closest to the image plane of the intermediate group GM, thereby achieving good vibration reduction performance while maintaining the optical performance of the variable magnification optical system.

[0079] Furthermore, it is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (17). 0.01 <fVR / (-fF)<2.50 ···(17) where fVR is the focal length of the vibration reduction group GVR fF: focal length of the focusing lens group GF

[0080] Conditional expression (17) defines an appropriate relationship between the focal length of the image stabilization group GVR and the focal length of the focusing lens group GF. By satisfying conditional expression (17), decentering coma and asymmetric curvature of field can be suppressed when correcting image blur, thereby achieving good image stabilization performance.

[0081] If the corresponding value of conditional expression (17) exceeds the upper limit, the focal length of the image stabilization group GVR becomes longer, which increases the amount of movement of the image stabilization group GVR when correcting image blur, making it difficult to suppress decentering coma and asymmetric curvature of field. Furthermore, if the focal length of the focusing lens group GF becomes shorter, it becomes difficult to correct spherical aberration, coma, and curvature of field that occur in the focusing lens group GF. By setting the upper limit of conditional expression (17) to 2.00, 1.80, 1.65, or even 1.60, the effects of each embodiment can be further ensured.

[0082] If the corresponding value of conditional expression (17) falls below the lower limit, the focal length of the image stabilization group GVR becomes shorter, making it difficult to suppress decentering coma and asymmetric curvature of field that occur in the image stabilization group GVR when correcting image blur. Furthermore, if the focal length of the focusing lens group GF becomes longer, the amount of movement of the focusing lens group GF during focusing increases, making it difficult to suppress fluctuations in spherical aberration, coma, and curvature of field during focusing. Setting the lower limit of conditional expression (17) to 0.10, 0.40, 0.63, 0.70, or even 1.00 can further ensure the effects of each embodiment.

[0083] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that the vibration reduction group GVR be made up of two lenses, which makes it possible to suppress fluctuations in chromatic aberration when correcting image blur.

[0084] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (18). 0.01<(-f2) / f1<1.00 (18) where f1 is the focal length of the first lens group G1 f2: Focal length of the second lens group G2

[0085] Conditional expression (18) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the first lens group G1. By satisfying conditional expression (18), spherical aberration, coma, and curvature of field can be effectively corrected.

[0086] If the corresponding value of conditional expression (18) exceeds the upper limit, the focal length of the second lens group G2 becomes longer, which increases the amount of movement of the second lens group G2 during zooming, making it difficult to suppress fluctuations in spherical aberration, coma, and field curvature during zooming. Furthermore, if the focal length of the first lens group G1 becomes shorter, it becomes difficult to correct the spherical aberration, coma, and field curvature that occur in the first lens group G1. Setting the upper limit of conditional expression (18) to 0.75, 0.50, 0.30, 0.25, 0.20, or even 0.18 can further ensure the effects of each embodiment.

[0087] If the corresponding value of conditional expression (18) falls below the lower limit, the focal length of the second lens group G2 becomes shorter, making it difficult to correct the spherical aberration, coma, and curvature of field that occur in the second lens group G2. Furthermore, if the focal length of the first lens group G1 becomes longer, the amount of movement of the first lens group G1 during zooming increases, making it difficult to suppress fluctuations in spherical aberration, coma, and curvature of field that occur during zooming. Setting the lower limit of conditional expression (18) to 0.05, 0.10, or even 0.16 can further ensure the effects of each embodiment.

[0088] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (19). 0.01 <TLt / ft<2.00 ···(19) where TLt is the total length of the variable magnification optical system ZL in the telephoto end state ft: focal length of variable magnification optical system ZL at telephoto end

[0089] Conditional expression (19) defines an appropriate relationship between the overall 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 telephoto end state. In each embodiment, the overall length of the variable magnification optical system ZL is the distance on the optical axis from the lens surface of the variable magnification optical system ZL closest to the object to the image plane I (note that the distance on the optical axis from the lens surface of the variable magnification optical system ZL closest to the image plane to the image plane I is the air-equivalent distance). Satisfying conditional expression (19) is preferable because it allows for a variable magnification optical system that is compact and lightweight while also having good optical performance. Setting the upper limit of conditional expression (19) to 1.75, 1.50, 1.35, 1.20, or even 1.19 can further enhance the effects of each embodiment. Setting the lower limit of conditional expression (19) to 0.10, 0.50, or even 1.00 can further enhance the effects of each embodiment.

[0090] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (20). 0.01<βFt / βFw<2.00 (20) where βFt is the lateral magnification of the focusing lens group GF in the telephoto end state. βFw: Lateral magnification of the focusing lens group GF at the wide-angle end

[0091] Conditional expression (20) defines an appropriate relationship between the lateral magnification of the focusing lens group GF in the telephoto end state and the lateral magnification of the focusing lens group GF in the wide-angle end state. Satisfying conditional expression (20) is preferable because it results in a variable-magnification optical system that is compact and lightweight while also having excellent optical performance. Setting the upper limit of conditional expression (20) to 1.80, 1.65, 1.50, or even 1.35 can further enhance the effects of each embodiment. Setting the lower limit of conditional expression (20) to 0.10, 0.50, 0.85, 0.90, 1.20, or even 1.21 can further enhance the effects of each embodiment.

[0092] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that the focusing lens group GF be made up of two lenses, which makes it possible to suppress fluctuations in chromatic aberration during focusing.

[0093] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that the first lens group G1 has a lens that satisfies the following conditional expression (21). 75.00<ν1L ···(21) where ν1L is the Abbe number of the lens in the first lens group G1.

[0094] Conditional expression (21) defines an appropriate range for the Abbe number of the lens in the first lens group G1. If the first lens group G1 includes a lens that satisfies conditional expression (21), a variable magnification optical system with good optical performance and corrected chromatic aberration can be obtained, which is preferable. By setting the lower limit of conditional expression (21) to 76.00, 77.50, 78.50, or even 80.00, the effect of this embodiment can be further ensured.

[0095] Next, a manufacturing method of the variable magnification optical system ZL according to the first embodiment will be outlined with reference to FIG. 10. First, 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, and a fifth lens group G5 having negative refractive power are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is made in which the spacing between adjacent lens groups changes during magnification (Step ST2). Next, a configuration is made in which the fourth lens group G4 is a focusing lens group that moves along the optical axis during focusing (Step ST3). Then, each lens is arranged within the lens barrel so as to satisfy at least the above conditional expression (1) (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system that is compact and lightweight while also having excellent optical performance.

[0096] Next, a manufacturing method of the variable-magnification optical system ZL according to the second embodiment will be outlined with reference to FIG. 11. First, 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, an intermediate group GM having at least one lens group and positive refractive power, a focusing lens group GF having negative refractive power, and a rear group GR having at least one lens group are arranged (Step ST11). Next, the spacing between adjacent lens groups is configured to change during magnification (Step ST12). Next, the focusing lens group GF is configured to move along the optical axis during focusing (Step ST13). Finally, the lenses are arranged within the lens barrel so as to satisfy at least the above conditional expressions (9) and (6) (Step ST14). This manufacturing method makes it possible to manufacture a variable-magnification optical system that is compact and lightweight while also having excellent optical performance. [Example]

[0097] Variable magnification optical systems ZL according to examples of each embodiment will be described below with reference to the drawings. FIGS. 1, 3, 5, and 7 are cross-sectional views showing the configuration and refractive power distribution of variable magnification optical systems ZL {ZL(1) to ZL(4)} according to Examples 1 to 4. Examples 1 to 3 correspond to the first embodiment, and Examples 1 to 4 correspond to the second embodiment. In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(4) according to Examples 1 to 4, arrows indicate the movement direction of each lens group when changing magnification from the wide-angle end state (W) to the telephoto end state (T). The movement direction of the focusing lens group when focusing from infinity to a close-distance object is indicated by an arrow along with the word "focusing." The movement direction of the vibration-proof group when correcting image blur is indicated by an arrow along with the word "vibration-proof."

[0098] 1, 3, 5, and 7, each lens group is represented by a combination of the symbol G and a number, and each lens is represented by a combination of the symbol L and a number. In this case, to prevent the symbols and numbers from becoming too numerous and complicated, each example uses its own independent combination of symbols and numbers to represent the lens group, etc. Therefore, even if the same combination of symbols and numbers is used between examples, this does not mean that the examples have the same configuration.

[0099] Tables 1 to 4 are shown below, with Table 1 showing data on various elements in Example 1, Table 2 in Example 2, Table 3 in Example 3, and Table 4 in Example 4. 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.

[0100] In the [Overall Specifications] table, f is the focal length of the entire lens system, FNO is the F-number, ω is the half angle of view (unit: °), and Y is the image height. TL is the distance on the optical axis from the lens surface closest to the object in the variable magnification optical system to the lens surface closest to the image plane when focused at infinity, plus Bf (back focus), and Bf is the distance on the optical axis from the lens surface closest to the image plane in the variable magnification optical system to the image plane when focused at infinity (equivalent to air). fM is the focal length of the middle group, and fR is the focal length of the rear group. Note that these values ​​are shown for both the wide-angle (W) and telephoto (T) ends of the magnification range.

[0101] Also, in the [Overall Specifications] table, fF indicates the focal length of the focusing lens group. fVR indicates the focal length of the vibration reduction group. fFRt indicates the composite focal length of the focusing lens group and at least one of the rear lens groups in the telephoto end state. f45t indicates the composite focal length of the fourth lens group and the fifth lens group in the telephoto end state. βFw indicates the lateral magnification of the focusing lens group in the wide-angle end state. βFt indicates the lateral magnification of the focusing lens group in the telephoto end state. βRw indicates the lateral magnification of the rear group in the wide-angle end state. βRt indicates the lateral magnification of the rear group in the telephoto end state. β4w indicates the lateral magnification of the fourth lens group in the wide-angle end state. β4t indicates the lateral magnification of the fourth lens group in the telephoto end state. β5w indicates the lateral magnification of the fifth lens group in the wide-angle end state. β5t represents the lateral magnification of the fifth lens group in the telephoto end state.

[0102] 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.

[0103] 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.

[0104] 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)

[0105] 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.

[0106] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0107] 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.

[0108] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0109] (First Example) The first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. 1 shows the lens configuration of a variable magnification optical system according to the first embodiment. The variable magnification optical system ZL(1) according to the first embodiment is composed of, arranged 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, and a fifth lens group G5 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves toward the object side along the optical axis, the second lens group G2 moves along the optical axis toward the image plane side and then toward the object side, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object side along the optical axis, 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, and when the magnification is changed, 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 the following embodiments.

[0110] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented lens 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.

[0111] 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 biconcave negative lens L22, a biconvex positive lens L23, and a negative meniscus lens L24 with a concave surface facing the object side.

[0112] The third lens group G3 is composed of, arranged along the optical axis from the object side, a biconvex positive lens L31, a biconvex positive lens L32, a cemented lens formed by cementing a negative meniscus lens L33 with its convex surface facing the object side and a biconvex positive lens L34, and a cemented lens formed by cementing a biconvex positive lens L35 and a negative meniscus lens L36 with its concave surface facing the object side. The positive lens L31 is a hybrid lens formed by a glass lens body with a resin layer provided on the object side surface. The object side surface of the resin layer is aspherical, and the positive lens L31 is a hybrid aspherical lens. In the "Lens Specifications" described below, surface number 15 indicates the object side surface of the resin layer, surface number 16 indicates the image side surface of the resin layer and the object side surface of the lens body (the surface where the two are cemented), and surface number 17 indicates the image side surface of the lens body. The positive lens L35 is also a hybrid lens constructed by providing a resin layer on the object-side surface of a glass lens body. The object-side surface of the resin layer is aspherical, making the positive lens L35 a hybrid aspherical lens. In the "Lens Specifications" described below, surface number 23 indicates the object-side surface of the resin layer, surface number 24 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the two are cemented), and surface number 25 indicates the image-side surface of the lens body (the surface cemented with the negative meniscus lens L36).

[0113] The fourth lens group G4 is composed of a cemented lens in which, in order from the object side, a biconvex positive lens L41 and a biconcave negative lens L42 are cemented together.

[0114] 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 positive meniscus lens L52 with its concave surface facing the object side. An image plane I is located on the image side of the fifth lens group G5. A parallel plate PP is located between the fifth lens group G5 and the image plane I.

[0115] In this embodiment, the third lens group G3 constitutes the middle group GM, which has positive refractive power as a whole. The positive lens L35 and negative meniscus lens L36, which are arranged closest to the image plane in the third lens group G3 (i.e., the middle group GM), constitute the vibration reduction group GVR, which is movable so as to have a displacement component in a direction perpendicular to the optical axis. The fourth lens group G4 corresponds to the focusing lens group GF, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing lens group GF (the entire fourth lens group G4) moves toward the image plane along the optical axis. The fifth lens group G5 constitutes the rear group GR, which has negative refractive power as a whole.

[0116] Table 1 below lists the values ​​of the specifications of the variable magnification optical system according to the first example.

[0117] (Table 1) [Overall specifications] Magnification ratio=7.327 fF=-44.045 fVR=28.900 fFRt=-26.761 f45t=-26.761 βFw=1.530 βFt=1.951 βRw=1.182 βRt=1.461 β4w=1.530 β4t=1.951 β5w=1.182 β5t=1.461 WMT f 18.540 50.034 135.845 FNO 3.604 4.938 6.486 ω 39.178 15.279 5.740 Y 13.741 14.200 14.200 TL 102.842 118.968 150.558 Bf 10.327 20.923 35.271 fM 19.995 19.995 19.995 fR -89.364 -89.364 -89.364 [Lens specifications] Surface number RD nd νd 1 78.364 1.650 1.80518 25.45 2 51.125 6.080 1.49782 82.57 3 -1387.433 0.100 4 51.002 3.950 1.48749 70.31 5 408.278 (D5) 6 105.667 1.000 1.83481 42.73 7 13.538 5.877 8 -40.384 1.000 1.74400 44.81 9 40.384 0.710 10 26.016 3.250 1.80809 22.74 11 -43.626 0.840 12 -21.186 0.900 1.77250 49.62 13 -113.505 (D13) 14 ∞ 1.500 (Aperture S) 15* 16.582 0.150 1.56093 36.64 16 17.341 3.350 1.51742 52.20 17 -499.849 1.000 18 54.519 1.560 1.60342 38.03 19 -1162.912 4.249 20 287.817 0.950 2.00100 29.12 21 15.000 3.900 1.49782 82.57 22 -33.047 1.000 23* 20.944 0.150 1.56093 36.64 24 20.408 4.560 1.51680 64.14 25 -27.508 0.900 1.66755 41.87 26 -40.524 (D26) 27 164.872 1.800 2.00100 29.12 28 -37.498 0.900 1.80400 46.60 29 23.384 (D29) 30 -16.370 1.100 1.90265 35.77 31 -32.544 0.100 32 -502.457 2.080 1.84666 23.80 33 -52.880 (D33) 34 ∞ 1.600 1.51680 64.14 35 ∞ 1.000 [Aspherical surface] Page 15 κ=1.0000,A4=-2.96855E-05,A6=-5.04688E-08,A8=-4.78359E-12,A10=0.00000E+00 Page 23 κ=1.0000,A4=-1.94678E-05,A6=-1.10034E-08,A8=-1.10745E-10,A10=0.00000E+00 [Can change the interval データ] Infinity focus state WMT Focus distance 18.540 50.034 135.845 Object distance ∞ ∞ ∞ D5 1.137 18.064 38.687 D13 20.855 6.402 2.040 D26 1.935 6.290 1.909 D29 13.983 12.681 18.046 D33 8.272 18.869 33.216 Close focus WMT Magnification -0.151 -0.147 -0.333 Object distance 96.613 280.487 248.897 D5 1.137 18.064 38.687 D13 20.855 6.402 2.040 D26 3.492 8.922 10.681 D29 12.425 10.049 9.274 D33 8.272 18.869 33.216 [Lens group data] Group starting plane focal length G1 1 77.833 G2 6 -13.200 G3 14 19.995 G4 27 -44.045 G5 30 -89.364

[0118] FIG. 2(A) shows various aberration diagrams of the variable magnification optical system of Example 1 when focused at infinity in the wide-angle end state. FIG. 2(B) shows various aberration diagrams of the variable magnification optical system of Example 1 when focused at infinity in the telephoto end state. In each aberration diagram, FNO indicates the F-number, and Y indicates the image height. Note that the spherical aberration diagram indicates the F-number value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram indicate the maximum image height, and the coma diagram indicates the value of each image height. d indicates the d-line (wavelength λ=587.6 nm), and g indicates the g-line (wavelength λ=435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. Note that the same symbols as in this example are used in the aberration diagrams of each example shown below, and redundant explanations will be omitted.

[0119] From the various aberration diagrams, it can be seen that the variable magnification optical system according to Example 1 has excellent correction of various aberrations from the wide-angle end state to the telephoto end state, and has excellent imaging performance.

[0120] (Second Example) The second example will be described with reference to FIGS. 3 and 4 and Table 2. FIG. 3 shows the lens configuration of the variable magnification optical system of the second example. The variable magnification optical system ZL(2) of the second example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having 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, and a fifth lens group G5 having negative refractive power. When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 moves toward the object side along the optical axis, the second lens group G2 moves along the optical axis toward the image plane side and then toward the object side, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object side along the optical axis, 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, and moves along the optical axis together with the third lens group G3 during magnification.

[0121] In the second embodiment, the first lens group G1, the second lens group G2, the fourth lens group G4, and the fifth lens group G5 are configured in the same manner as in the first embodiment, and therefore the same reference numerals as in the first embodiment are used, and detailed descriptions of each of these lenses will be omitted.

[0122] The third lens group G3 is composed of, arranged along the optical axis from the object side, a biconvex positive lens L31, a positive meniscus lens L32 with a convex surface facing the object side, a cemented lens formed by cementing a negative meniscus lens L33 with a convex surface facing the object side and a biconvex positive lens L34, and a cemented lens formed by cementing a biconvex positive lens L35 and a negative meniscus lens L36 with a concave surface facing the object side. The positive lens L31 is a hybrid lens formed by a glass lens body with a resin layer provided on the object side surface. The object side surface of the resin layer is aspherical, and the positive lens L31 is a hybrid aspherical lens. In the "Lens Specifications" described below, surface number 15 indicates the object side surface of the resin layer, surface number 16 indicates the image side surface of the resin layer and the object side surface of the lens body (the surface where the two are cemented), and surface number 17 indicates the image side surface of the lens body. The positive lens L35 is also a hybrid lens constructed by providing a resin layer on the object-side surface of a glass lens body. The object-side surface of the resin layer is aspherical, making the positive lens L35 a hybrid aspherical lens. In the "Lens Specifications" described below, surface number 23 indicates the object-side surface of the resin layer, surface number 24 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the two are cemented), and surface number 25 indicates the image-side surface of the lens body (the surface cemented with the negative meniscus lens L36).

[0123] In this embodiment, the third lens group G3 constitutes the middle group GM, which has positive refractive power as a whole. The positive lens L35 and negative meniscus lens L36, which are arranged closest to the image plane in the third lens group G3 (i.e., the middle group GM), constitute the vibration reduction group GVR, which is movable so as to have a displacement component in a direction perpendicular to the optical axis. The fourth lens group G4 corresponds to the focusing lens group GF, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing lens group GF (the entire fourth lens group G4) moves toward the image plane along the optical axis. The fifth lens group G5 constitutes the rear group GR, which has negative refractive power as a whole.

[0124] Table 2 below lists the values ​​of the specifications of the variable magnification optical system according to the second example.

[0125] (Table 2) [Overall specifications] Magnification ratio=7.313 fF=-40.918 fVR=30.427 fFRt=-29.177 f45t=-29.177 βFw=1.592 βFt=2.058 βRw=1.154 βRt=1.338 β4w=1.592 β4t=2.058 β5w=1.154 β5t=1.338 WMT f 18.540 50.000 135.580 FNO 3.605 4.898 6.487 ω 39.148 15.062 5.697 Y 13.734 14.200 14.200 TL 102.355 119.632 150.055 Bf 10.305 20.056 33.956 fM 19.597 19.597 19.597 fR -128.502 -128.502 -128.502 [Lens specifications] Surface number RD nd νd 1 77.089 1.650 1.80518 25.45 2 50.017 5.759 1.49700 81.61 3 -3731.534 0.100 4 55.411 3.987 1.51680 63.88 5 606.340 (D5) 6 71.182 1.000 1.83481 42.73 7 12.765 5.103 8 -32.874 1.000 1.83481 42.73 9 57.757 0.599 10 29.824 2.802 1.92286 20.88 11 -53.069 1.055 12 -19.343 1.000 1.83481 42.73 13 -54.386 (D13) 14 ∞ 1.500 (Aperture S) 15* 17.533 0.200 1.56093 36.64 16 19.709 2.971 1.51742 52.20 17 -532.437 1.000 18 36.670 1.847 1.59270 35.27 19 141.326 3.709 20 118.256 1.000 2.00100 29.13 21 14.872 3.665 1.49700 81.61 22 -35.608 1.000 23* 23.806 0.200 1.56093 36.64 24 27.593 3.799 1.51680 63.88 25 -28.440 0.900 2.00069 25.46 26 -34.910 (D26) 27 132.182 2.693 1.85000 27.03 28 -17.587 1.000 1.80100 34.92 29 23.474 (D29) 30 -15.338 1.200 1.83481 42.73 31 -28.528 0.100 32 -150.496 2.229 1.84666 23.78 33 -40.999 (D33) 34 ∞ 1.600 1.51680 64.13 35∞1.000 [Aspherical data] Page 15 κ=1.0000,A4=-2.77917E-05,A6=-3.74974E-08,A8=5.24965E-11,A10=0.00000E+00 Page 23 κ = 1.0000, A4 = -1.89584E-05, A6 = 1.08869E-08, A8 = -1.42329E-10, A10 = 0.00000E+00 [Variable interval data] Infinity focus state W M T Focal length 18.540 50.000 135.580 Object distance ∞ ∞ ∞ D5 1.150 20.019 39.281 D13 21.142 7.098 2.000 D26 2.000 6.706 3.303 D29 14.691 12.686 18.448 D33 8.250 18.001 31.901 Closest focus state W M T ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Fig. 4(A) is a diagram showing various aberrations when the variable magnification optical system according to Example 2 is focused at infinity in the wide-angle end state. Fig. 4(B) is a diagram showing various aberrations when the variable magnification optical system according to Example 2 is focused at infinity in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 2 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0127] (Third Example) Example 3 will be described with reference to FIGS. 5 and 6 and Table 3. FIG. 5 shows the lens configuration of a variable magnification optical system according to Example 3. The variable magnification optical system ZL(3) according to Example 3 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having 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, and a fifth lens group G5 having negative refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move toward the object side along the optical axis, 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, and moves along the optical axis together with the third lens group G3 during magnification.

[0128] In the third embodiment, the first lens group G1, the second lens group G2, and the fourth lens group G4 are configured in the same manner as in the first embodiment, and therefore the same reference numerals as in the first embodiment are used, and detailed description of each of these lenses will be omitted.

[0129] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L31, a cemented lens formed by cementing a biconvex positive lens L32 and a biconcave negative lens L33, a biconvex positive lens L34, and a cemented lens formed by cementing a biconvex positive lens L35 and a negative meniscus lens L36 with its concave surface facing the object side. The positive lens L31 is a hybrid lens formed by a glass lens body with a resin layer on the object side surface. The object side surface of the resin layer is aspherical, and the positive lens L31 is a hybrid aspherical lens. In the "Lens Specifications" section described below, surface number 15 indicates the object side surface of the resin layer, surface number 16 indicates the image side surface of the resin layer and the object side surface of the lens body (the surface where the two are cemented), and surface number 17 indicates the image side surface of the lens body. The positive lens L35 is also a hybrid lens formed by a glass lens body with a resin layer on the object side surface. The object-side surface of the resin layer is aspherical, and the positive lens L35 is also a composite aspherical lens. In the [Lens Specifications] described below, surface number 23 indicates the object-side surface of the resin layer, surface number 24 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the two are cemented), and surface number 25 indicates the image-side surface of the lens body (the surface cemented with the negative meniscus lens L36).

[0130] 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. An image plane I is located on the image side of the fifth lens group G5. A parallel plate PP is located between the fifth lens group G5 and the image plane I.

[0131] In this embodiment, the third lens group G3 constitutes the middle group GM, which has positive refractive power as a whole. The positive lens L35 and negative meniscus lens L36, which are arranged closest to the image plane in the third lens group G3 (i.e., the middle group GM), constitute the vibration reduction group GVR, which is movable so as to have a displacement component in a direction perpendicular to the optical axis. The fourth lens group G4 corresponds to the focusing lens group GF, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing lens group GF (the entire fourth lens group G4) moves toward the image plane along the optical axis. The fifth lens group G5 constitutes the rear group GR, which has negative refractive power as a whole.

[0132] Table 3 below lists the values ​​of the specifications of the variable magnification optical system according to the third example.

[0133] (Table 3) [Overall specifications] Magnification ratio=7.312 fF=-37.129 fVR=29.958 fFRt=-26.127 f45t=-26.127 βFw=1.607 βFt=2.123 βRw=1.159 βRt=1.351 β4w=1.607 β4t=2.123 β5w=1.159 β5t=1.351 WMT f 18.540 49.998 135.573 FNO 3.605 5.012 6.453 ω 39.122 15.336 5.783 Y 13.794 14.200 14.200 TL 101.754 121.465 149.451 Bf 10.304 21.804 32.615 fM 19.253 19.253 19.253 fR -115.716 -115.716 -115.716 [Lens specifications] Surface number RD nd νd 1 73.519 1.650 1.80518 25.45 2 48.434 6.102 1.49700 81.61 3 -2804.506 0.100 4 56.181 3.859 1.51680 63.88 5 464.308 (D5) 6 61.160 1.000 1.83481 42.73 7 12.720 5.196 8 -34.365 1.000 1.83481 42.73 9 57.322 0.401 10 29.582 2.704 1.92286 20.88 11 -59.703 1.156 12 -19.306 1.000 1.75500 52.34 13 -67.886 (D13) 14 ∞ 1.500 (Aperture S) 15* 18.139 0.200 1.56093 36.64 16 20.458 3.028 1.51742 52.20 17 -119.805 4.590 18 25.116 2.965 1.57501 41.51 19 -275.984 1.000 2.00100 29.14 20 17.695 0.247 21 21.205 2.858 1.49700 81.61 22 -42.496 1.111 23* 24.421 0.200 1.56093 36.64 24 28.545 4.380 1.51680 63.88 25 -18.889 0.900 2.00100 29.14 26 -26.089 (D26) 27 193.701 3.264 1.85000 27.03 28 -14.147 1.000 1.80100 34.92 29 22.767 (D29) 30 -13.687 1.200 1.83481 42.73 31 -26.599 0.100 32 95.577 2.601 1.85000 27.03 33 -87.080 (D33) 34 ∞ 1.600 1.51680 63.88 35 ∞ 1.000 [Aspherical surface] Page 15 κ=1.0000,A4=-2.46352E-05,A6=-6.76098E-08,A8=3.13409E-10,A10=0.00000E+00 Page 23 κ=1.0000,A4=-2.19056E-05,A6=4.43054E-08,A8=-1.00568E-10,A10=0.00000E+00 [Can change the interval データ] Infinity focus state WMT Focus distance 18.540 49.998 135.573 Object distance ∞ ∞ ∞ D5 1.050 19.709 39.182 D13 20.412 7.734 2.000 D26 2.000 4.819 2.752 D29 12.676 12.086 17.589 D33 8.249 19.749 30.560 Close focus WMT Magnification -0.150 -0.146 -0.331 Object distance 97.701 277.990 250.004 D5 1.050 19.709 39.182 D13 20.412 7.734 2.000 D26 3.364 6.963 10.836 D29 11.313 9.942 9.505 D33 8.249 19.749 30.560 [Lens group data] Group starting plane focal length G1 1 78.669 G2 6 -12.882 G3 14 19.253 G4 27 -37.129 G5 30 -115.716

[0134] Fig. 6(A) is a diagram showing various aberrations when the variable magnification optical system according to Example 3 is focused at infinity in the wide-angle end state. Fig. 6(B) is a diagram showing various aberrations when the variable magnification optical system according to Example 3 is focused at infinity in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 3 has excellent imaging performance, with various aberrations being well corrected from the wide-angle end state to the telephoto end state.

[0135] (Fourth Example) Example 4 will be described with reference to FIGS. 7 to 8 and Table 4. FIG. 7 shows the lens configuration of a variable magnification optical system according to Example 4. 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, and a sixth lens group G6 having positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 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, and moves along the optical axis together with the third lens group G3 during magnification.

[0136] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented lens 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.

[0137] 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 biconcave negative lens L22, a biconvex positive lens L23, and a biconcave negative lens L24.

[0138] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L31, a positive meniscus lens L32 with its convex surface facing the object side, and a biconcave negative lens L33.

[0139] 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 lens formed by cementing a negative meniscus lens L42 with its convex surface facing the object side and a biconvex positive lens L43. The positive lens L41 is a hybrid lens formed by providing a resin layer on the object-side surface of a glass lens body. The object-side surface of the resin layer is aspherical, and the positive lens L41 is a hybrid aspherical lens. In the "Lens Specifications" described below, surface number 21 indicates the object-side surface of the resin layer, surface number 22 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the two are cemented), and surface number 23 indicates the image-side surface of the lens body.

[0140] The fifth lens group G5 is composed of a cemented lens in which, in order from the object side, a biconvex positive lens L51 and a biconcave negative lens L52 are cemented together.

[0141] 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. An image plane I is located on the image side of the sixth lens group G6. A parallel plate PP is located between the sixth lens group G6 and the image plane I.

[0142] In this embodiment, the third lens group G3 and the fourth lens group G4 constitute a middle group GM having positive refractive power as a whole. The positive lens L41 of the fourth lens group G4 constitutes a vibration reduction group GVR that is movable so as to have a displacement component in a direction perpendicular to the optical axis. The fifth lens group G5 corresponds to a focusing lens group GF that moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the focusing lens group GF (the entire fifth lens group G5) moves toward the image plane along the optical axis. The sixth lens group G6 constitutes a rear group GR having positive refractive power as a whole.

[0143] Table 4 below lists the values ​​of the specifications of the variable magnification optical system according to the fourth example.

[0144] (Table 4) [Overall specifications] Magnification ratio=7.348 fF=-29.503 fVR=25.327 fFRt=-35.547 βFw=1.801 βFt=2.880 βRw=1.012 βRt=0.941 WMT f 18.507 69.967 135.991 FNO 3.592 5.646 6.346 ω 38.657 11.301 5.911 Y 14.200 14.200 14.200 TL 103.497 130.917 148.519 Bf 10.783 28.603 36.638 fM 19.220 17.885 17.861 fR 365.857 365.857 365.857 [Lens specifications] Surface number RD nd νd 1 68.597 1.650 1.80518 25.45 2 44.486 6.390 1.48749 70.31 3 2147.717 0.100 4 48.948 4.164 1.58913 61.22 5 240.577 (D5) 6 129.624 1.000 1.83481 42.73 7 11.939 5.096 8 -32.648 1.000 1.80400 46.60 9 102.523 0.100 10 23.122 4.390 1.78472 25.64 11 -30.169 0.363 12 -23.466 1.000 1.80400 46.60 13 125.146 (D13) 14 ∞ 1.500 (Aperture S) 15 40.213 2.735 1.48749 70.31 16 -23.799 0.100 17 15.287 2.541 1.48749 70.31 18 46.241 1.281 19 -26.779 1.000 1.65160 58.62 20 44.829 (D20) 21* 24.441 0.250 1.56093 36.64 22 25.854 3.563 1.51680 64.14 23 -26.825 0.500 24 32.072 1.200 2.00100 29.12 25 12.533 4.110 1.51680 64.14 26 -33.308 (D26) 27 123.803 2.716 1.90200 25.26 28 -20.927 1.000 1.80100 34.92 29 17.132 (D29) 30 -17.414 1.200 1.80400 46.60 31 -30.030 0.150 32 42.914 3.585 1.62004 36.40 33 -101.277 (D33) 34 ∞ 1.600 1.51680 64.14 35∞1.000 [Aspherical data] Page 21 κ=1.0000,A4=-5.28036E-05,A6=8.22302E-08,A8=0.00000E+00,A10=0.00000E+00 [Variable Interval Data] Infinity focus WMT Focal length 18.507 69.967 135.991 Object distance ∞ ∞ ∞ D5 2.100 24.867 37.551 D13 19.139 5.971 2.854 D20 4.666 1.099 1.030 D26 3.058 4.591 2.000 D29 11.068 13.102 15.761 D33 8.728 26.549 34.583 Close focus state WMT Magnification -0.151 -0.201 -0.341 Object distance 95.958 268.538 250.936 D5 2.100 24.867 37.551 D13 19.139 5.971 2.854 D20 4.666 1.099 1.030 D26 4.313 7.653 10.037 D29 9.812 10.040 7.724 D33 8.728 26.549 34.583 [Lens group data] Group starting plane focal length G1 1 72.234 G2 6 -12.115 G3 14 42.713 G4 21 21.508 G5 27 -29.503 G6 30 365.857

[0145] Fig. 8(A) is a diagram showing various aberrations when the variable magnification optical system according to Example 4 is focused at infinity in the wide-angle end state. Fig. 8(B) is a diagram showing various aberrations when the variable magnification optical system according to Example 4 is focused at infinity in the telephoto end state. From these aberration diagrams, it can be seen that the variable magnification optical system according to Example 4 has excellent correction of various aberrations from the wide-angle end state to the telephoto end state, and has excellent imaging performance.

[0146] 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 (21) for all the examples (Examples 1 to 4). Condition (1) 0.11 <f4 / f5<0.70 Conditional expression (2) 0.01<(-f4) / f3<5.00 Condition (3) 0.01 <f3 / (-f5)<1.00 Condition (4) 0.01 <f3 / (-f45t)<2.00 Conditional expression (5) 0.01<β5t / β5w<2.00 Condition (6) 0.01 <Bfw / fw<0.95 Conditional expression (7) 75.00<ν3L Condition (8) 0.01 <f3 / fVR<2.00 Condition (9) 0.30<(-f2) / fMt<0.80 Condition (10) 0.01<(-fF) / fMt<5.00 Condition (11) 0.01 <fMt / |fRt|<1.00 Conditional expression (12) 0.01<(-fF) / |fRt|<1.00 Condition (13) 0.01 <fMt / (-fFRt)<1.00 Conditional expression (14) 0.10<βRt / βRw<2.00 Condition (15) 75.00<νML Condition (16) 0.01 <fMt / fVR<1.00 Condition (17) 0.01 <fVR / (-fF)<2.50 Conditional expression (18) 0.01<(-f2) / f1<1.00 Condition (19) 0.01 <TLt / ft<2.00 Conditional expression (20) 0.01<βFt / βFw<2.00 Conditional expression (21) 75.00<ν1L

[0147] [Conditional Expression Corresponding Values] (First to Fourth Examples) Conditional Expression 1st Example 2nd Example 3rd Example 4th Example (1) 0.493 0.318 0.321 - (2) 2.203 2.088 1.928 - (3) 0.224 0.153 0.166 - (4) 0.747 0.672 0.737 - (5) 1.236 1.159 1.166 - (6) 0.557 0.556 0.556 0.583 (7) 82.57 81.61 81.61 - (8) 0.692 0.644 0.643 - (9) 0.660 0.660 0.669 0.678 (10) 2.203 2.088 1.928 1.652 (11) 0.224 0.153 0.166 0.049 (12) 0.493 0.318 0.321 0.081 (13) 0.747 0.672 0.737 0.502 (14) 1.236 1.159 1.166 0.930 (15) 82.57 81.61 81.61 - (16) 0.692 0.644 0.643 0.705 (17) 1.524 1.345 1.239 1.165 (18) 0.170 0.165 0.164 0.168 (19) 1.112 1.111 1.106 1.096 (20) 1.275 1.293 1.321 1.599 (21) 82.57 81.61 81.61 -

[0148] According to each of the above embodiments, it is possible to realize a variable magnification optical system that is compact yet has good optical performance.

[0149] The above-described examples are merely illustrative examples of the present invention, and the present invention is not limited to these.

[0150] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the variable magnification optical system of each embodiment.

[0151] Although examples of the variable magnification optical system of each embodiment have been shown with a five-group configuration and a six-group configuration, the present application is not limited to these, and variable magnification optical systems with other group configurations (e.g., seven groups, eight groups, nine groups, etc.) may also be configured. For example, a lens or lens group may be added to the most object-side or most image-side of the variable magnification optical system of each embodiment. Furthermore, for example, the middle group may be configured with three or more lens groups, and the rear group may be configured with two or more lens groups. 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.

[0152] In the variable magnification optical systems of each embodiment, instead of the fourth or fifth lens group, a single or multiple lens groups, or a partial lens group, may be moved in the optical axis direction to function as a focusing lens group that focuses from an object at infinity to an object at a close distance. The focusing lens group can also be applied to autofocus, and is suitable for motor drive (using an ultrasonic motor, etc.) for autofocus.

[0153] In the variable magnification optical system of each embodiment, not only some lenses in the third lens group or some lenses in the fourth lens group, but also a lens group or a 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 an in-plane direction including the optical axis to serve as an image stabilization lens group that corrects image blur caused by camera shake.

[0154] 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.

[0155] 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.

[0156] The aperture diaphragm is preferably disposed between the second lens group and the third lens group, but it is also possible to use the lens frame to fulfill that role instead of providing a member serving as an aperture diaphragm.

[0157] 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]

[0158] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group I Image plane S Aperture stop

Claims

1. The lens comprises, arranged in order from the object side along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power; When changing magnification, the spacing between adjacent lens groups changes, the fourth lens group is a focusing lens group that moves along the optical axis during focusing, A variable magnification optical system that satisfies the following condition: 0.11<f4 / f5<0.70 0.01<Bfw / fw<0.58 0.01<(-f2) / f1<0.30 where f4 is the focal length of the fourth lens group f5: focal length of the fifth lens group Bfw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state f1: focal length of the first lens group f2: focal length of the second lens group

2. The lens comprises, arranged in order from the object side along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power; When changing magnification, the spacing between adjacent lens groups changes, the fourth lens group is a focusing lens group that moves along the optical axis during focusing, A variable magnification optical system that satisfies the following condition: 0.11<f4 / f5<0.70 75.00<ν3L 0.01<(-f2) / f1<0.30 0.01<TLt / ft<1.20 where f4 is the focal length of the fourth lens group f5: focal length of the fifth lens group ν3L: Abbe number of the lens in the third lens group f1: focal length of the first lens group f2: focal length of the second lens group TLt: total length of the variable magnification optical system in the telephoto end state ft: focal length of the variable magnification optical system in the telephoto end state

3. The lens comprises, arranged in order from the object side along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power; When changing magnification, the spacing between adjacent lens groups changes, the fourth lens group is a focusing lens group that moves along the optical axis during focusing, A variable magnification optical system that satisfies the following condition: 0.20<f4 / f5<0.60 0.01<Bfw / fw<0.58 where f4 is the focal length of the fourth lens group f5: focal length of the fifth lens group Bfw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state

4. The lens comprises, arranged in order from the object side along the optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power; When changing magnification, the spacing between adjacent lens groups changes, the fourth lens group is a focusing lens group that moves along the optical axis during focusing, A variable magnification optical system that satisfies the following conditional expression: 0.20<f4 / f5<0.60 75.00<ν3L 0.01<TLt / ft<1.35 where ν3L is the Abbe number of the lens in the third lens group. where f4 is the focal length of the fourth lens group f5: focal length of the fifth lens group ν3L: Abbe number of the lens in the third lens group TLt: total length of the variable magnification optical system in the telephoto end state ft: focal length of the variable magnification optical system in the telephoto end state

5. 5. A variable magnification optical system according to claim 1, which satisfies the following condition: 0.01<(-f4) / f3<5.00 where f3 is the focal length of the third lens group

6. 6. A variable magnification optical system according to claim 1, which satisfies the following condition: 0.01<f3 / (-f5)<1.00 where f3 is the focal length of the third lens group

7. 7. A variable magnification optical system according to claim 1, which satisfies the following condition: 0.01<f3 / (-f45t)<2.00 where f3 is the focal length of the third lens group f45t: composite focal length of the fourth lens group and the fifth lens group in the telephoto end state

8. 8. A variable magnification optical system according to claim 1, which satisfies the following condition: 0.01<β5t / β5w<2.00 where β5t is the lateral magnification of the fifth lens group in the telephoto end state. β5w: lateral magnification of the fifth lens group in the wide-angle end state

9. 4. The variable magnification optical system according to claim 1, wherein the third lens group has a lens that satisfies the following condition: 1 / (f / f<f<1 / f)<f<f<1 / f< ... 75.00<ν3L where ν3L is the Abbe number of the lens in the third lens group.

10. 4. A variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.01<TLt / ft<2.00 where TLt is the total length of the variable magnification optical system in the telephoto end state. ft: focal length of the variable magnification optical system in the telephoto end state

11. 11. A variable magnification optical system according to claim 1, which satisfies the following condition: 0.01<βFt / βFw<2.00 where βFt is the lateral magnification of the focusing lens group in the telephoto end state. βFw: lateral magnification of the focusing lens group in the wide-angle end state

12. 12. The variable magnification optical system according to claim 1, wherein the focusing lens group is made up of two lenses.

13. 13. The variable magnification optical system according to claim 1, wherein the first lens group has a lens that satisfies the following conditional expression: 1 / (f / f<1 / f)<f / f<1 / f; 75.00<ν1L where ν1L is the Abbe number of the lens in the first lens group.

14. 5. A variable magnification optical system according to claim 2, wherein the following condition is satisfied: 0.01<Bfw / fw<0.95 where Bfw is the back focus of the variable magnification optical system in the wide-angle end state. fw: focal length of the variable magnification optical system in the wide-angle end state

15. 5. A variable magnification optical system according to claim 3, wherein the following condition is satisfied: 0.01<(-f2) / f1<1.00 where f1 is the focal length of the first lens group f2: focal length of the second lens group

16. An optical instrument comprising the variable magnification optical system according to any one of claims 1 to 15.

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