Variable magnification optical system and optical equipment

Abstract

To provide a zoom optical system which is compact and bright and offers good optical performance.SOLUTION: A zoom optical system ZL provided herein consists of a first lens group G1 having positive refractive power and a rear group GR comprising multiple lens groups, and is configured such that a distance between adjacent lens groups changes while zooming. The multiple lens groups of the rear group GR include a second lens group G2 having positive refractive power disposed on the most object side in the rear group GR. The zoom lens satisfies the following conditional expressions: 0.15<f2 / f1<0.80, 1.00<(L1r2+L1r1) / (L1r2-L1r1)<2.50, 1.50<(LEr2+LEr1) / (LEr2-LEr1)<3.00.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-132675 Summary of the Invention

[0004] A variable magnification optical system according to the present invention comprises, arranged in order from the object side along an optical axis, a first lens group having positive refractive power and a rear group having a plurality of lens groups, wherein the spacing between adjacent lens groups changes during magnification variation, and the plurality of lens groups in the rear group include a second lens group having positive refractive power that is arranged closest to the object side of the rear group, and satisfies the following conditional expression: 0.15 <f2 / f1<0.80 1.00<(L1r2+L1r1) / (L1r2-L1r1)<2.50 1.50<(LEr2+LEr1) / (LEr2-LEr1)<3.00 where f1 is the focal length of the first lens group f2: focal length of the second lens group L1r1: the radius of curvature of the object-side lens surface of the lens arranged closest to the object side of the variable magnification optical system L1r2: the radius of curvature of the image-side lens surface of the lens arranged closest to the object side of the variable magnification optical system LEr1: radius of curvature of the object-side lens surface of the lens arranged closest to the image side in the variable magnification optical system LEr2: radius of curvature of the image-side lens surface of the lens arranged closest to the image side in the variable magnification optical system

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

[0006] [Figure 1] FIG. 2 is a diagram showing the lens configuration of a variable magnification optical system according to Example 1. [Figure 2] 2A and 2B are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focused at infinity in the wide-angle end state and the telephoto end state, respectively. [Figure 3] 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

[0007] A preferred embodiment of the present invention will now be described. First, a camera (optical device) equipped with a variable magnification optical system according to this embodiment will be described with reference to FIG. 9. As shown in FIG. 9, this camera 1 is composed of a body 2 and a photographic lens 3 attached to the body 2. The body 2 is equipped with an image sensor 4, a body control unit (not shown) that controls the operation of the digital camera, and an LCD screen 5. The photographic lens 3 is equipped with a variable magnification optical system ZL consisting of multiple lens groups, and a lens position control mechanism (not shown) that controls the position of each lens group. The lens position control mechanism is composed of a sensor that detects the position of the lens groups, a motor that moves the lens groups back and forth along the optical axis, a control circuit that drives the motor, etc.

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

[0009] Next, a variable magnification optical system according to the first embodiment will be described. A variable magnification optical system ZL(1), which is an example of the variable magnification optical system (zoom lens) ZL according to the first embodiment, is composed of, as shown in FIG. 1, a first lens group G1 having positive refractive power and a rear group GR having multiple lens groups, arranged in order from the object side along the optical axis. The spacing between adjacent lens groups changes during magnification. The multiple lens groups in the rear group GR include a second lens group G2 having positive refractive power, which is positioned closest to the object side of the rear group GR.

[0010] With the above-described configuration, the variable-magnification optical system ZL according to the first embodiment satisfies the following conditional expression (1). 0.15 <f2 / f1<0.80 ···(1) where f1 is the focal length of the first lens group G1 f2: Focal length of the second lens group G2

[0011] According to the first embodiment, it is possible to obtain a variable magnification optical system that is small yet bright 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 first embodiment may be the variable magnification optical system ZL(2) shown in Fig. 3, the variable magnification optical system ZL(3) shown in Fig. 5, or the variable magnification optical system ZL(4) shown in Fig. 7.

[0012] Conditional expression (1) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the second lens group G2. Note that the focal length of the first lens group G1 is the focal length of the first lens group G1 when focused at infinity. By satisfying conditional expression (1), good optical performance can be obtained throughout the entire zoom range.

[0013] If the value corresponding to conditional expression (1) falls outside the above range, it becomes difficult to obtain good optical performance over at least a portion of the magnification range. The effects of this embodiment can be further ensured by setting the upper limit of conditional expression (1) to 0.75, 0.70, 0.65, 0.60, 0.55, 0.50, 0.45, or even 0.40. Furthermore, the effects of this embodiment can be further ensured by setting the lower limit of conditional expression (1) to 0.18, 0.20, 0.23, 0.25, 0.28, or even 0.30.

[0014] Next, a variable magnification optical system according to a second embodiment will be described. A variable magnification optical system ZL(1), which is an example of a variable magnification optical system (zoom lens) ZL according to the second embodiment, is composed of, as shown in FIG. 1, a first lens group G1 having positive refractive power and a rear group GR having multiple lens groups, arranged in order from the object side along the optical axis. When changing magnification from the wide-angle end state to the telephoto end state, the first lens group G1 moves along the optical axis toward the object side, changing the spacing between adjacent lens groups. The first lens group G1 includes, arranged in order from the object side along the optical axis, a front fixed group GP1 whose position is fixed relative to the image plane I during focusing, and a front focusing group GF1 that moves along the optical axis during focusing.

[0015] With the above-described configuration, the variable-magnification optical system ZL according to the second embodiment satisfies the following conditional expressions (2) and (3). 0.60 <fP1 / (-fF1)<1.00 ···(2) 0.80<(-fF1) / fw<1.40 (3) where fP1 is the focal length of the front fixed group GP1 fF1: focal length of the front focusing group GF1 fw: focal length of variable magnification optical system ZL at wide-angle end

[0016] According to the second embodiment, it is possible to obtain a variable magnification optical system that is small yet bright 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.

[0017] Conditional formula (2) defines an appropriate relationship between the focal length of the front fixed group GP1 and the focal length of the front focusing group GF1. Conditional formula (3) defines an appropriate relationship between the focal length of the front focusing group GF1 and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional formulas (2) and (3), good optical performance can be achieved even when focusing on close objects, despite the compact size.

[0018] If the corresponding value of conditional expression (2) falls outside the above range, it becomes difficult to obtain good optical performance when focusing on a close object. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (2) to 0.98, 0.96, 0.95, 0.93, 0.90, 0.88, or even 0.85. The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (2) to 0.63, 0.65, 0.68, 0.70, 0.73, 0.75, 0.76, or even 0.80.

[0019] If the value corresponding to conditional expression (3) is outside the above range, it becomes difficult to obtain good optical performance when focusing on a close object. The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (3) to 1.35, 1.33, 1.30, 1.26, 1.25, 1.23, or even 1.20. Furthermore, the effect of this embodiment can be further ensured by setting the lower limit of conditional expression (3) to 0.83, 0.85, 0.88, 0.90, 0.93, 0.95, 0.96, or even 1.00.

[0020] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (4). 1.20 <ft / fw<2.00 ···(4) where ft is the focal length of the variable magnification optical system ZL at the telephoto end fw: focal length of variable magnification optical system ZL at wide-angle end

[0021] Condition (4) defines an appropriate range for the zoom ratio of the variable-magnification optical system ZL. By satisfying condition (4), various aberrations such as field curvature can be effectively corrected over the entire range of zoom ratio.

[0022] If the corresponding value of conditional expression (4) exceeds the upper limit, it becomes difficult to correct field curvature in at least a part of the range of magnification. By setting the upper limit of conditional expression (4) to 1.90, 1.80, 1.70, or even 1.60, the effects of each embodiment can be further ensured.

[0023] If the corresponding value of conditional expression (4) falls below the lower limit, the magnification ratio of the variable magnification optical system ZL becomes too small, making it useless as a variable magnification optical system (zoom lens). By setting the lower limit of conditional expression (4) to 1.25, 1.30, 1.35, 1.40, 1.43, 1.45, or even 1.48, the effects of each embodiment can be more reliably achieved.

[0024] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (5). 0.01 <Bfw / TLw<0.20 ···(5) Bfw: back focus of the variable magnification optical system ZL in the wide-angle end state TLw: Total length of the variable magnification optical system ZL in the wide-angle end state

[0025] Condition (5) defines the appropriate relationship between the back focal length of the variable magnification optical system ZL in the wide-angle end state and the overall length of the variable magnification optical system ZL in the wide-angle end state. By satisfying condition (5), it is possible to effectively correct curvature of field.

[0026] If the corresponding value of conditional expression (5) exceeds the upper limit, the relative length of the back focus with respect to the overall length of the variable magnification optical system ZL becomes large, making it difficult to correct the curvature of field. By setting the upper limit of conditional expression (5) to 0.18, 0.15, 0.12, or even 0.10, the effects of each embodiment can be more reliably achieved.

[0027] If the corresponding value of conditional expression (5) is below the lower limit, the overall length of the variable magnification optical system ZL increases, making it difficult to correct field curvature while keeping the variable magnification optical system ZL compact. By setting the lower limit of conditional expression (5) to 0.02, 0.04, 0.05, 0.06, or even 0.07, the effects of each embodiment can be more reliably achieved.

[0028] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (6). 0.60 <YLE / IHw<1.00 ···(6) However, YLE is the effective diameter of the lens located closest to the image side in the variable magnification optical system ZL. IHw: Maximum image height of the variable magnification optical system ZL in the wide-angle end state

[0029] Conditional expression (6) defines an appropriate relationship between the effective diameter of the lens located closest to the image in the variable magnification optical system ZL and the maximum image height of the variable magnification optical system ZL in the wide-angle end state. Hereinafter, the lens located closest to the image in the variable magnification optical system ZL may be referred to as the final lens. In each embodiment, the effective diameter of the final lens refers to the effective diameter of the lens surface of the final lens located closest to the image in the wide-angle end state. By satisfying conditional expression (6), field curvature can be effectively corrected.

[0030] If the corresponding value of conditional expression (6) exceeds the upper limit, the effective diameter of the final lens becomes large, making it difficult to correct field curvature while keeping the variable magnification optical system ZL compact. By setting the upper limit of conditional expression (6) to 0.96, 0.95, 0.93, 0.90, 0.88, or even 0.85, the effects of each embodiment can be more reliably achieved.

[0031] If the corresponding value of conditional expression (6) falls below the lower limit, the effective diameter of the final lens becomes small, making it difficult to correct field curvature. By setting the lower limit of conditional expression (6) to 0.65, 0.70, 0.73, 0.75, 0.78, or even 0.80, the effects of each embodiment can be further ensured.

[0032] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (7). FNOw<2.8 (7) However, FNOw: F-number of the variable magnification optical system ZL at the wide-angle end

[0033] Conditional expression (7) defines an appropriate range for the F-number of the variable magnification optical system ZL in the wide-angle end state. Satisfying conditional expression (7) is preferable because it results in a bright variable magnification optical system. Setting the upper limit of conditional expression (7) to 2.50, 2.40, 2.20, 2.00, or even 1.90 can further ensure the effects of each embodiment. The lower limit of conditional expression (7) may be set to 1.20, 1.40, 1.50, or even greater than 1.80.

[0034] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (8). 10.00°<2ωw<35.00° ···(8) However, 2ωw: the total angle of view of the variable magnification optical system ZL in the wide-angle end state

[0035] Conditional expression (8) defines an appropriate range for the total angle of view of the variable magnification optical system ZL in the wide-angle end state. Satisfying conditional expression (8) is preferable because it provides a variable magnification optical system with a medium telephoto range. By setting the upper limit of conditional expression (8) to 32.00°, 30.00°, 29.00°, or even 28.00°, the effects of each embodiment can be further ensured. By setting the lower limit of conditional expression (8) to 15.00°, 20.00°, 24.00°, or even 27.00°, the effects of each embodiment can be further ensured.

[0036] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (9). 0.30 <fw / f1<0.70 ···(9) where fw is the focal length of the variable magnification optical system ZL at the wide-angle end f1: focal length of the first lens group G1

[0037] Condition (9) defines an appropriate relationship between the focal length of the variable magnification optical system ZL in the wide-angle end state and the focal length of the first lens group G1. By satisfying condition (9), spherical aberration can be effectively corrected throughout the entire range of magnification.

[0038] If the corresponding value of conditional expression (9) exceeds the upper limit, the refractive power of the first lens group G1 becomes too strong, making it difficult to correct spherical aberration. By setting the upper limit of conditional expression (9) to 0.68, 0.65, 0.62, 0.58, or even 0.55, the effects of each embodiment can be further ensured.

[0039] If the corresponding value of conditional expression (9) falls below the lower limit, the refractive power of the first lens group G1 becomes too weak, and the variable magnification optical system ZL becomes large. As a result, it becomes difficult to correct spherical aberration while keeping the variable magnification optical system ZL compact. By setting the lower limit of conditional expression (9) to 0.33, 0.35, 0.38, 0.42, or even 0.45, the effects of each embodiment can be more reliably achieved.

[0040] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that the multiple lens groups in the rear group GR include a second lens group G2 having positive refractive power that is arranged closest to the object in the rear group GR, and that the following conditional expression (10) be satisfied: 0.30 <f2 / fRw<0.65 ···(10) However, f2 is the focal length of the second lens group G2. fRw: composite focal length of rear group GR at the wide-angle end

[0041] Conditional expression (10) defines an appropriate relationship between the focal length of the second lens group G2 and the combined focal length of the rear group GR at the wide-angle end. By satisfying conditional expression (10), spherical aberration can be effectively corrected throughout the entire zoom range.

[0042] If the corresponding value of conditional expression (10) exceeds the upper limit, the refractive power of the second lens group G2 becomes too weak, making it difficult to correct curvature of field. By setting the upper limit of conditional expression (10) to 0.62, 0.60, 0.58, 0.55, or even 0.52, the effects of each embodiment can be further ensured.

[0043] If the corresponding value of conditional expression (10) falls below the lower limit, the refractive power of the second lens group G2 becomes too strong, making it difficult to correct spherical aberration. By setting the lower limit of conditional expression (10) to 0.32, 0.34, 0.35, 0.36, 0.38, or even 0.40, the effects of each embodiment can be more reliably achieved.

[0044] In the variable magnification optical systems ZL according to the first and second embodiments, it is desirable that the multiple lens groups in the rear group GR include a final lens group GE that is arranged closest to the image side of the rear group GR, and that the following conditional expression (11) be satisfied: 0.50<(-fGE) / fw<1.00 ···(11) where fGE is the focal length of the final lens group GE fw: focal length of variable magnification optical system ZL at wide-angle end

[0045] Conditional expression (11) defines an appropriate relationship between the focal length of the final lens group GE and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (11), the variable magnification optical system ZL can be made compact and field curvature can be effectively corrected.

[0046] If the corresponding value of conditional expression (11) exceeds the upper limit, the refractive power of the final lens group GE becomes too weak, making it difficult to correct curvature of field. By setting the upper limit of conditional expression (11) to 0.98, 0.95, 0.93, 0.90, 0.88, 0.85, 0.83, or even 0.80, the effects of each embodiment can be more reliably achieved.

[0047] If the corresponding value of conditional expression (11) falls below the lower limit, the refractive power of the final lens group GE becomes too strong, making it difficult to correct distortion and lateral chromatic aberration. By setting the lower limit of conditional expression (11) to 0.53, 0.55, 0.58, 0.60, 0.63, 0.65, 0.68, 0.70, or even 0.72, the effects of each embodiment can be more reliably achieved.

[0048] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (12). 1.00<(L1r2+L1r1) / (L1r2-L1r1)<2.50 ···(12) where L1r1 is the radius of curvature of the lens surface closest to the object in the variable magnification optical system ZL. L1r2: Radius of curvature of the image-side lens surface of the lens located closest to the object in the variable magnification optical system ZL

[0049] Conditional expression (12) defines an appropriate range for the shape factor of the lens located closest to the object in the variable magnification optical system ZL. By satisfying conditional expression (12), various aberrations such as coma can be effectively corrected throughout the entire range of magnification.

[0050] If the corresponding value of conditional expression (12) exceeds the upper limit, it becomes difficult to correct spherical aberration. By setting the upper limit of conditional expression (12) to 2.40, 2.25, 2.10, 2.00, 1.95, 1.90, 1.85, or even 1.80, the effects of each embodiment can be further ensured.

[0051] If the corresponding value of conditional expression (12) falls below the lower limit, it becomes difficult to correct coma. By setting the lower limit of conditional expression (12) to 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, or even 1.40, the effects of each embodiment can be further ensured.

[0052] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (13). 1.50<(LEr2+LEr1) / (LEr2-LEr1)<3.00 ···(13) where LEr1 is the radius of curvature of the object-side lens surface of the lens arranged closest to the image side in the variable magnification optical system ZL. LEr2: Radius of curvature of the image-side lens surface of the lens located closest to the image side in the variable magnification optical system ZL

[0053] Conditional expression (13) defines an appropriate range for the shape factor of the lens (final lens) located closest to the image side in the variable magnification optical system ZL. By satisfying conditional expression (13), various aberrations such as field curvature can be effectively corrected throughout the entire range of variable magnification.

[0054] If the corresponding value of conditional expression (13) exceeds the upper limit, it becomes difficult to correct spherical aberration. By setting the upper limit of conditional expression (13) to 2.90, 2.80, 2.70, 2.60, 2.50, 2.45, 2.40, 2.35, or even 2.30, the effects of each embodiment can be further ensured.

[0055] If the corresponding value of conditional expression (13) falls below the lower limit, it becomes difficult to correct coma. By setting the lower limit of conditional expression (13) to 1.60, 1.65, 1.75, 1.80, 1.85, 1.90, 1.95, or even 2.00, the effects of each embodiment can be further ensured.

[0056] It is desirable that the variable magnification optical system ZL according to the first and second embodiments satisfy the following conditional expression (14). 1.00 <f1 / fRw<1.80 ···(14) where f1 is the focal length of the first lens group G1 fRw: composite focal length of rear group GR at the wide-angle end

[0057] Condition (14) defines an appropriate relationship between the focal length of the first lens group G1 and the combined focal length of the rear group GR at the wide-angle end. By satisfying condition (14), spherical aberration can be effectively corrected throughout the entire zoom range.

[0058] If the corresponding value of conditional expression (14) exceeds the upper limit, the refractive power of the first lens group G1 becomes too weak, and the variable magnification optical system ZL becomes large. As a result, it becomes difficult to correct spherical aberration while keeping the variable magnification optical system ZL compact. By setting the upper limit of conditional expression (14) to 1.75, 1.70, 1.68, 1.65, 1.63, or even 1.60, the effects of each embodiment can be more reliably achieved.

[0059] If the corresponding value of conditional expression (14) falls below the lower limit, the refractive power of the first lens group G1 becomes too strong, making it difficult to correct spherical aberration. By setting the lower limit of conditional expression (14) to 1.03, 1.05, 1.08, or even 1.10, the effects of each embodiment can be further ensured.

[0060] In the variable magnification optical systems ZL according to the first and second embodiments, the multiple lens groups of the rear group GR include a second lens group G2 having positive refractive power that is located closest to the object side of the rear group GR, and a third lens group G3 that is located adjacent to the image side of the second lens group G2, and it is desirable that the distance between the second lens group G2 and the third lens group G3 decreases when changing magnification from the wide-angle end state to the telephoto end state.

[0061] The variable magnification optical systems ZL according to the first and second embodiments have an aperture stop S disposed between the first lens group G1 and the rear group GR, and it is desirable that the first lens group G1 moves along the optical axis together with the aperture stop S during magnification variation.

[0062] In the variable magnification optical systems ZL according to the first and second embodiments, the first lens group G1 has a front focusing group GF1 that moves along the optical axis during focusing, and the rear group GR has a rear focusing group GF2 that moves along the optical axis along a trajectory different from that of the front focusing group GF1 during focusing, and it is desirable that at least a portion of any one of the multiple lens groups in the rear group GR constitutes the rear focusing group GF2.

[0063] In the variable magnification optical systems ZL according to the first and second embodiments, the front focusing group GF1 and the rear focusing group GF2 may satisfy the following conditional expression (15). -0.30 <fF2 / fF1<0.30 ···(15) where fF1 is the focal length of the front focusing group GF1 fF2: focal length of rear focusing group GF2

[0064] Condition (15) defines an appropriate relationship between the focal length of the front focusing group GF1 and the focal length of the rear focusing group GF2. By satisfying condition (15), fluctuations in field curvature during focusing can be effectively suppressed throughout the entire magnification range.

[0065] If the corresponding value of conditional expression (15) exceeds the upper limit, it becomes difficult to suppress fluctuations in field curvature during focusing. By setting the upper limit of conditional expression (15) to 0.28, 0.25, 0.23, 0.20, or even 0.18, the effects of each embodiment can be more reliably achieved.

[0066] If the corresponding value of conditional expression (15) is below the lower limit, it becomes difficult to suppress fluctuations in field curvature during focusing. By setting the lower limit of conditional expression (15) to -0.25, -0.15, -0.10, -0.05, -0.01, 0.01, or even 0.02, the effects of each embodiment can be more reliably achieved.

[0067] In the variable magnification optical systems ZL according to the first and second embodiments, the front focusing group GF1 and the rear focusing group GF2 may satisfy the following conditional expression (16). 0.01 <fF2 / (-fF1)<0.30 ···(16) where fF1 is the focal length of the front focusing group GF1 fF2: focal length of rear focusing group GF2

[0068] Conditional expression (16) defines an appropriate relationship between the focal length of the front focusing group GF1 and the focal length of the rear focusing group GF2. By satisfying conditional expression (16), fluctuations in field curvature during focusing can be effectively suppressed throughout the entire magnification range.

[0069] If the corresponding value of conditional expression (16) exceeds the upper limit, it becomes difficult to suppress fluctuations in field curvature during focusing. By setting the upper limit of conditional expression (16) to 0.28, 0.25, 0.23, 0.20, or even 0.18, the effects of each embodiment can be more reliably achieved.

[0070] If the corresponding value of conditional expression (16) is below the lower limit, it becomes difficult to suppress fluctuations in field curvature during focusing. By setting the lower limit of conditional expression (16) to 0.02, the effects of each embodiment can be more reliably achieved.

[0071] Next, referring to FIG. 10, a manufacturing method for the variable magnification optical system ZL according to the first embodiment will be outlined. First, a first lens group G1 having positive refractive power and a rear group GR having multiple lens groups are arranged, in order from the object side along the optical axis (Step ST1). Next, a configuration is established in which the spacing between adjacent lens groups changes during magnification (Step ST2). Next, of the multiple lens groups in the rear group GR, a second lens group G2 having positive refractive power is arranged closest to the object side of the rear group GR (Step ST3). Then, the lenses are arranged within the lens barrel so as to satisfy at least the above-mentioned conditional expression (1) (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system that is compact yet bright and has good optical performance.

[0072] Next, with reference to FIG. 11, a manufacturing method for the variable-magnification optical system ZL according to the second embodiment will be outlined. First, a first lens group G1 having positive refractive power and a rear lens group GR having multiple lens groups are arranged, in order from the object side along the optical axis (Step ST11). Next, the first lens group G1 is configured to move along the optical axis toward the object side during zooming from the wide-angle end state to the telephoto end state, changing the spacing between adjacent lens groups (Step ST12). Next, in the first lens group G1, in order from the object side along the optical axis, a front fixed lens group GP1 whose position relative to the image plane I during focusing and a front focusing lens group GF1 that moves along the optical axis during focusing are arranged (Step ST13). Then, the lenses are arranged within the lens barrel so as to satisfy at least the above conditional expressions (2) and (3) (Step ST14). This manufacturing method makes it possible to manufacture a variable-magnification optical system that is compact, bright, and has excellent optical performance. [Example]

[0073] The 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. In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(4) according to Examples 1 to 4, the direction of movement of the focusing group along the optical axis when focusing from infinity to a close-distance object is indicated by an arrow along with the word "focusing." In the cross-sectional views of the variable magnification optical systems ZL(1) to ZL(4) according to Examples 1 to 4, the direction of movement of each lens group along the optical axis when changing magnification from the wide-angle end state (W) to the telephoto end state (T) is indicated by an arrow.

[0074] 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.

[0075] 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.

[0076] In the [Overall Specifications] table, f is the focal length of the entire lens system, FNO is the F-number, 2ω is the angle of view (unit: ° (degrees), where ω is half the angle of view), and Ymax is the maximum image height. TL is the distance from the frontmost lens surface to the last lens surface on the optical axis when focused at infinity plus BF, and BF is the distance from the last lens surface to the image plane I on the optical axis when focused at infinity (back focus). Note that these values ​​are shown for both the wide-angle end (W) and the telephoto end (T) magnification settings.

[0077] Additionally, in the table of "Overall Specifications," YLE indicates the effective diameter of the lens (final lens) located closest to the image side of the variable magnification optical system. IHw indicates the maximum image height of the variable magnification optical system in the wide-angle end state. fP1 indicates the focal length of the front fixed group. fF1 indicates the focal length of the front focusing group. fRw indicates the combined focal length of the rear group in the wide-angle end state. fF2 indicates the focal length of the rear focusing group.

[0078] 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.

[0079] 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.

[0080] 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)

[0081] 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.

[0082] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0083] 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.

[0084] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0085] (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, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 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 and the third lens group G3 move along the optical axis toward the object side, changing the spacing between adjacent lens groups. During magnification variation, the aperture stop S moves along the optical axis together with the first lens group G1, while the second lens group G2 is fixed in position relative to the image plane I. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of the respective lens group, and this is the same for all of the following embodiments.

[0086] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a cemented lens of a positive meniscus lens L12 with a convex surface facing the object side and a negative meniscus lens L13 with a convex surface facing the object side, a positive meniscus lens L14 with a convex surface facing the object side, and a cemented lens of a biconvex positive lens L15 and a biconcave negative lens L16.

[0087] The second lens group G2 is composed of, arranged along the optical axis from the object side, a biconcave negative lens L21, a biconvex positive lens L22, and a cemented lens consisting of a biconvex positive lens L23 and a negative meniscus lens L24 with its concave surface facing the object side. The object side surface of the positive lens L23 is aspheric.

[0088] The third lens group G3 is composed of, arranged along the optical axis from the object side, a cemented lens consisting of a positive meniscus lens L31 with its concave surface facing the object side and a biconcave negative lens L32, and a negative meniscus lens L33 with its concave surface facing the object side. The negative lens L32 has an aspherical lens surface facing the image side. An image surface I is located on the image side of the third lens group G3.

[0089] In this embodiment, the second lens group G2 and the third lens group G3 constitute the rear group GR, which has positive refractive power overall. The third lens group G3 corresponds to the final lens group GE, which is located closest to the image side of the rear group GR. The negative meniscus lens L33 of the third lens group G3 corresponds to the final lens. The positive meniscus lens L11 of the first lens group G1, the cemented lens of the positive meniscus lens L12 and the negative meniscus lens L13, and the positive meniscus lens L14 constitute the front fixed group GP1, whose position is fixed relative to the image plane I during focusing. The cemented lens of the positive lens L15 and the negative lens L16 of the first lens group G1 constitutes the front focusing group GF1, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the front focusing group GF1 (the cemented lens of the positive lens L15 and the negative lens L16 of the first lens group G1) moves toward the image side along the optical axis.

[0090] Table 1 below lists the values ​​of the specifications of the variable magnification optical system according to the first example.

[0091] (Table 1) [Overall specifications] Magnification ratio=1.497 YLE=18.000 IHw=21.600 fP1=84.022 fF1=-101.078 fRw=119.920 WT f 87.497 130.992 FNO 1.859 2.788 2ω 27.50 18.79 Ymax 21.600 21.600 TL 119.454 149.236 Bf 9.103 24.335 [Lens specifications] Surface number RD nd νd 1 46.914 6.995 1.846660 23.8 2 166.537 0.200 3 47.658 7.580 1.593190 67.9 4 33336.213 2.000 1.846660 23.8 5 30.363 2.896 6 40.058 5.343 1.593190 67.9 7 165.681 (D7) 8 362.425 3.014 1.945944 18.0 9 -100.065 1.100 1.850000 27.0 10 62.769 (D10) 11∞ (D11) (Aperture S) 12 -39.802 1.100 1.720000 43.6 13 5040.621 0.200 14 65.807 6.882 1.696800 55.5 15 -83.001 7.355 16* 254.149 7.210 1.772500 49.6 17 -39.577 1.100 1.846660 23.8 18 -60.083 (D18) 19 -412.223 4.304 1.846660 23.8 20 -59.324 1.600 1.487490 70.3 21* 87.613 8.473 22 -37.483 1.600 1.834000 37.2 23 -96.128 Bf [Aspherical data] Page 16 κ=1.0000,A4=-4.16377E-06,A6=1.34984E-10,A8=-2.63295E-12,A10=2.51738E-15 Page 21 κ=1.0000,A4=-3.27383E-06,A6=-4.18982E-09,A8=2.10935E-12,A10=-1.03143E-14 [Variable Interval Data] Infinity focus WMT Focal length 87.497 104.995 130.992 Object distance ∞ ∞ ∞ D7 2.675 2.675 2.675 D10 13.768 13.768 13.768 D11 4.479 17.898 34.262 D18 16.479 9.390 1.246 Bf 9.103 16.191 24.335 Closest focusing state W M T Magnification -0.085 -0.103 -0.131 Object distance 1080.047 1066.880 1050.516 D7 11.703 11.826 11.983 D10 4.740 4.617 4.460 D11 4.479 17.898 34.262 D18 16.479 9.390 1.246 Bf 9.103 16.191 24.335 [Lens group data] Group Starting surface Focal length G1 1 186.610 G2 12 59.317 G3 19 -66.172

[0092] 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.

[0093] 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.

[0094] (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 a variable magnification optical system according to the second example. The variable magnification optical system ZL(2) according to the second example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 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 and the third lens group G3 move along the optical axis toward the object side, changing the spacing between adjacent lens groups. During magnification variation, the aperture stop S moves along the optical axis together with the first lens group G1, while the position of the second lens group G2 is fixed relative to the image plane I.

[0095] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with its convex surface facing the object side, a cemented lens of a biconvex positive lens L12 and a biconcave negative lens L13, a positive meniscus lens L14 with its convex surface facing the object side, and a cemented lens of a biconvex positive lens L15 and a biconcave negative lens L16.

[0096] The second lens group G2 is composed of, arranged along the optical axis from the object side, a biconcave negative lens L21, a biconvex positive lens L22, and a cemented lens consisting of a biconvex positive lens L23 and a negative meniscus lens L24 with its concave surface facing the object side. The object side surface of the positive lens L23 is aspheric.

[0097] The third lens group G3 is composed of, arranged along the optical axis from the object side, a cemented lens consisting of a positive meniscus lens L31 with its concave surface facing the object side and a biconcave negative lens L32, and a negative meniscus lens L33 with its concave surface facing the object side. The negative lens L32 has an aspherical lens surface facing the image side. An image surface I is located on the image side of the third lens group G3.

[0098] In this embodiment, the second lens group G2 and the third lens group G3 constitute the rear group GR, which has positive refractive power overall. The third lens group G3 corresponds to the final lens group GE, which is located closest to the image side of the rear group GR. The negative meniscus lens L33 of the third lens group G3 corresponds to the final lens. The positive meniscus lens L11, the cemented lens of the positive lens L12 and the negative lens L13, and the positive meniscus lens L14 of the first lens group G1 constitute the front fixed group GP1, whose position is fixed relative to the image plane I during focusing. The cemented lens of the positive lens L15 and the negative lens L16 of the first lens group G1 constitute the front focusing group GF1, which moves along the optical axis during focusing. The cemented lens of the positive lens L23 and the negative meniscus lens L24 of the second lens group G2 constitute the rear focusing group GF2, which moves along the optical axis during focusing. When focusing from an object at infinity to an object at a close distance, the front focusing group GF1 (a cemented lens of the positive lens L15 and the negative lens L16 in the first lens group G1) moves toward the image along the optical axis, and the rear focusing group GF2 (a cemented lens of the positive lens L23 and the negative meniscus lens L24 in the second lens group G2) moves toward the object along the optical axis.

[0099] Table 2 below lists the values ​​of the specifications of the variable magnification optical system according to the second example.

[0100] (Table 2) [Overall specifications] Magnification ratio=1.499 YLE=18.000 IHw=21.600 fP1=82.997 fF1=-99.080 fRw=118.936 fF2=671.573 WT f 87.387 131.002 FNO 1.859 2.791 2ω 27.48 18.77 Ymax 21.600 21.600 TL 115.452 145.326 Bf 9.106 24.310 [Lens specifications] Surface number RD nd νd 1 48.237 6.840 1.846660 23.8 2 176.058 0.201 3 47.311 7.706 1.593190 67.9 4 -10977.113 2.000 1.846660 23.8 5 30.989 2.743 6 40.022 5.341 1.593190 67.9 7 158.515 (D7) 8 288.236 3.092 1.945944 18.0 9 -101.965 1.100 1.850000 27.0 10 58.937 (D10) 11∞ (D11) (Aperture S) 12 -38.826 1.100 1.720000 43.6 13 1908.000 0.200 14 63.919 7.360 1.696800 55.5 15 -78.285 (D15) 16* 305.745 7.228 1.772500 49.6 17 -38.870 1.100 1.846660 23.8 18 -58.392 (D18) 19 -329.356 4.313 1.846660 23.8 20 -57.876 1.600 1.487490 70.3 21* 88.263 8.353 22 -38.199 1.600 1.834000 37.2 23 -96.156 Bf [Aspherical surface] Page 16 κ=1.0000,A4=-4.42907E-06,A6=2.27606E-10,A8=-3.87693E-12,A10=4.36472E-15 Page 21 κ=1.0000,A4=-3.09349E-06,A6=-4.12964E-09,A8=3.11255E-12,A10=-9.85811E-15 [Can change the interval データ] Infinity focus state WMT Focus distance 87.387 105.000 131.002 Object distance ∞ ∞ ∞ D7 2.600 2.600 2.600 D10 13.859 13.859 13.859 D11 4.529 18.085 34.404 D15 6.736 6.736 6.736 D18 16.744 9.652 1.541 Bf 9.106 16.198 24.310 Close focus WMT Magnification -0.105 -0.128 -0.160 Object distance 880.077 866.739 850.411 D7 12.676 13.336 12.579 D10 3.783 3.123 3.881 D11 4.529 18.085 34.404 D15 6.092 6.334 5.007 D18 17.389 10.053 3.269 Bf 9.106 16.199 24.310 [Lens group data] Group starting plane focal length G1 1 185.733 G2 12 58.900 G3 19 -66.353

[0101] 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.

[0102] (Third Example) The third example will be described with reference to FIGS. 5 to 6 and Table 3. FIG. 5 shows the lens configuration of the variable magnification optical system of the third example. The variable magnification optical system ZL(3) of the third example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having 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 third lens group G3, and the fourth lens group G4 move along the optical axis toward the object side, changing the spacing between adjacent lens groups. During magnification variation, the aperture stop S moves along the optical axis together with the first lens group G1, while the position of the second lens group G2 is fixed relative to the image plane I.

[0103] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a cemented lens of a biconvex positive lens L12 and a biconcave negative lens L13, a biconvex positive lens L14, and a cemented lens of a positive meniscus lens L15 with a concave surface facing the object side and a biconcave negative lens L16.

[0104] The second lens group G2 is composed of, arranged along the optical axis from the object side, a biconcave negative lens L21, a biconvex positive lens L22, and a cemented lens consisting of a biconvex positive lens L23 and a negative meniscus lens L24 with its concave surface facing the object side. The object side surface of the positive lens L23 is aspheric.

[0105] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a cemented lens consisting of a positive meniscus lens L31 with its concave surface facing the object side and a negative meniscus lens L32 with its concave surface facing the object side. The negative meniscus lens L32 has an aspherical lens surface facing the image side.

[0106] The fourth lens group G4 is composed of a negative meniscus lens L41 with its concave surface facing the object side. An image surface I is located on the image side of the fourth lens group G4.

[0107] In this embodiment, the second lens group G2, the third lens group G3, and the fourth lens group G4 constitute the rear group GR, which has a positive refractive power as a whole. The fourth lens group G4 corresponds to the final lens group GE, which is located closest to the image side of the rear group GR. The negative meniscus lens L41 of the fourth lens group G4 corresponds to the final lens. The positive meniscus lens L11 of the first lens group G1, the cemented lens of the positive lens L12 and the negative lens L13, and the positive lens L14 constitute the front fixed group GP1, whose position is fixed relative to the image plane I during focusing. The cemented lens of the positive meniscus lens L15 and the negative lens L16 of the first lens group G1 constitute the front focusing group GF1, which moves along the optical axis during focusing. The entire third lens group G3 constitutes the rear focusing group GF2, which moves along the optical axis during focusing. When focusing from an object at infinity to an object at a close distance, the front focusing group GF1 (a cemented lens of the positive meniscus lens L15 and the negative lens L16 in the first lens group G1) moves along the optical axis toward the image side, and the rear focusing group GF2 (the entire third lens group G3) moves along the optical axis toward the image side on a trajectory (movement amount) different from that of the front focusing group GF1.

[0108] Table 3 below lists the values ​​of the specifications of the variable magnification optical system according to the third example.

[0109] (Table 3) [Overall specifications] Magnification ratio=1.497 YLE=18.000 IHw=21.600 fP1=74.366 fF1=-90.157 fRw=147.649 fF2=2886.045 WT f 87.500 131.001 FNO 1.858 2.786 2ω 27.43 18.80 Ymax 21.600 21.600 TL 116.222 142.023 Bf 9.251 25.667 [Lens specifications] Surface number RD nd νd 1 56.682 6.478 1.846660 23.8 2 318.773 0.200 3 50.234 8.612 1.593190 67.9 4 -271.667 1.200 1.854779 24.8 5 37.409 4.817 6 44.054 6.278 1.497820 82.6 7 -2142.172 (D7) 8 -369.420 3.507 1.922860 20.9 9 -52.787 1.100 1.770470 29.7 10 67.323 (D10) 11 ∞ (D11) 12 -34.128 1.100 1.723420 38.0 13 306.831 0.200 14 92.900 6.152 1.834810 42.7 15 -56.452 4.410 16* 875.397 9.115 1.693430 53.3 17 -26.311 1.100 1.850260 32.4 18 -44.283 (D18) 19 -132.378 3.586 1.846660 23.8 20 -50.802 1.600 1.588870 61.1 21* -371.956 (D21) 22 -29.395 1.600 1.693500 53.2 23 -86.978 Bf [Aspherical surface] Page 16 κ=1.0000,A4=-4.22271E-06,A6=-3.12823E-10,A8=-1.96537E-12,A10=2.59367E-15 Page 21 κ = 1.0000, A4 = -6.06022E-06, A6 = -5.54411E-09, A8 = -1.79582E-12, A10 = -6.81506E-15 [Variable interval data] Infinity focus state WMT Focal length 87.500 105.000 131.001 Object distance ∞ ∞ ∞ D7 2.737 2.737 2.737 D10 12.555 12.555 12.555 D11 4.854 16.294 30.654 D18 17.472 10.297 2.001 D21 8.299 7.849 7.354 Bf 9.251 16.876 25.667 Closest focus state WMT Magnification -0.104 -0.127 -0.161 Object distance 880.418 868.885 854.626 D7 11.412 11.574 11.749 D10 3.881 3.719 3.543 D11 4.854 16.294 30.654 D18 19.896 11.712 3.066 D21 5.875 6.434 6.289 Bf 9.283 16.924 25.744 [Lens group data] Group Starting surface Focal length G1 1 163.682 G2 12 62.062 G3 19 2886.045 G4 22 -64.759

[0110] 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.

[0111] (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, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 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 and the third lens group G3 move toward the object side along the optical axis, and the second lens group G2 moves toward the image side along the optical axis, changing the spacing between adjacent lens groups. Furthermore, when varying magnification, the aperture stop S moves along the optical axis together with the first lens group G1.

[0112] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a cemented lens of a positive meniscus lens L12 with a convex surface facing the object side and a negative meniscus lens L13 with a convex surface facing the object side, a positive meniscus lens L14 with a convex surface facing the object side, and a cemented lens of a biconvex positive lens L15 and a biconcave negative lens L16.

[0113] The second lens group G2 is composed of, arranged along the optical axis from the object side, a biconcave negative lens L21, a biconvex positive lens L22, and a cemented lens consisting of a biconvex positive lens L23 and a negative meniscus lens L24 with its concave surface facing the object side. The object side surface of the positive lens L23 is aspheric.

[0114] The third lens group G3 is composed of, arranged along the optical axis from the object side, a cemented lens consisting of a positive meniscus lens L31 with its concave surface facing the object side and a biconcave negative lens L32, and a negative meniscus lens L33 with its concave surface facing the object side. The negative lens L32 has an aspherical lens surface facing the image side. An image surface I is located on the image side of the third lens group G3.

[0115] In this embodiment, the second lens group G2 and the third lens group G3 constitute the rear group GR, which has positive refractive power overall. The third lens group G3 corresponds to the final lens group GE, which is located closest to the image side of the rear group GR. The negative meniscus lens L33 of the third lens group G3 corresponds to the final lens. The positive meniscus lens L11 of the first lens group G1, the cemented lens of the positive meniscus lens L12 and the negative meniscus lens L13, and the positive meniscus lens L14 constitute the front fixed group GP1, whose position is fixed relative to the image plane I during focusing. The cemented lens of the positive lens L15 and the negative lens L16 of the first lens group G1 constitutes the front focusing group GF1, which moves along the optical axis during focusing. When focusing from an object at infinity to a close object, the front focusing group GF1 (the cemented lens of the positive lens L15 and the negative lens L16 of the first lens group G1) moves toward the image side along the optical axis.

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

[0117] (Table 4) [Overall specifications] Magnification ratio=1.497 YLE=18.000 IHw=21.600 fP1=82.088 fF1=-96.051 fRw=118.327 WT f 87.500 131.000 FNO 1.860 2.785 2ω 27.51 18.80 Ymax 21.600 21.600 TL 115.456 145.509 Bf 9.105 23.679 [Lens specifications] Surface number RD nd νd 1 47.389 6.930 1.846660 23.8 2 168.915 0.200 3 46.629 7.713 1.593190 67.9 4 20954.696 2.000 1.846660 23.8 5 30.529 2.967 6 40.993 5.299 1.593190 67.9 7 183.696 (D7) 8 389.304 3.072 1.945944 18.0 9 -93.280 1.100 1.850000 27.0 10 60.942 (D10) 11∞ (D11) (Aperture S) 12 -40.799 1.100 1.720000 43.6 13 6130.299 0.200 14 65.875 6.929 1.696800 55.5 15 -87.261 7.752 16* 234.100 7.362 1.772500 49.6 17 -40.329 1.100 1.846660 23.8 18 -61.665 (D18) 19 -723.265 4.425 1.846660 23.8 20 -61.965 1.600 1.487490 70.3 21* 82.427 7.649 22 -40.118 1.600 1.834000 37.2 23 -116.183 Bf [Aspherical data] Page 16 κ = 1.0000, A4 = -4.01821E-06, A6 = 3.20252E-10, A8 = -3.12345E-12, A10 = 3.14559E-15 Page 21 κ = 1.0000, A4 = -2.97715E-06, A6 = -3.92189E-09, A8 = 1.79480E-12, A10 = -9.46067E-15 [Variable interval data] Infinity focus state W M T Focal length 87.500 105.000 131.000 Object distance ∞ ∞ ∞ D7 2.689 2.689 2.689 D10 13.153 13.153 13.153 D11 4.613 18.735 35.490 D18 16.898 9.784 1.500 Bf 9.105 15.838 23.679 Closest focus state W M T Magnification -0.085 -0.103 -0.130 Object distance 1084.544 1070.803 1054.491 D7 11.156 11.275 11.422 D10 4.686 4.566 4.420 D11 4.613 18.735 35.490 D18 16.898 9.784 1.500 Bf 9.105 15.838 23.679 [Lens group data] Group Starting surface Focal length G1 1 187.387 G2 12 59.720 G3 19 -67.423

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

[0119] 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 (16) for all the examples (Examples 1 to 4). Condition (1) 0.15 <f2 / f1<0.80 Condition (2) 0.60 <fP1 / (-fF1)<1.00 Conditional expression (3) 0.80<(-fF1) / fw<1.40 Condition (4) 1.20 <ft / fw<2.00 Condition (5) 0.01 <Bfw / TLw<0.20 Condition (6) 0.60 <YLE / IHw<1.00 Conditional expression (7) FNOw<2.8 Conditional expression (8) 10.00°<2ωw<35.00° Condition (9) 0.30 <fw / f1<0.70 Condition (10) 0.30 <f2 / fRw<0.65 Conditional expression (11) 0.50<(-fGE) / fw<1.00 Conditional expression (12) 1.00<(L1r2+L1r1) / (L1r2-L1r1)<2.50 Conditional expression (13) 1.50<(LEr2+LEr1) / (LEr2-LEr1)<3.00 Condition (14) 1.00 <f1 / fRw<1.80 Condition (15) -0.30 <fF2 / fF1<0.30 Condition (16) 0.01 <fF2 / (-fF1)<0.30

[0120] [Conditional Expression Corresponding Values] (First to Fourth Examples) Conditional Expression 1st Example 2nd Example 3rd Example 4th Example (1) 0.318 0.317 0.379 0.319 (2) 0.831 0.838 0.825 0.855 (3) 1.155 1.134 1.030 1.098 (4) 1.497 1.499 1.497 1.497 (5) 0.076 0.079 0.080 0.079 (6) 0.833 0.833 0.833 0.833 (7) 1.859 1.859 1.858 1.860 (8) 27.50 27.48 27.43 27.51 (9) 0.469 0.470 0.535 0.467 (10) 0.495 0.495 0.420 0.505 (11) 0.756 0.759 0.740 0.771 (12) 1.784 1.755 1.433 1.780 (13) 2.278 2.278 2.021 2.055 (14) 1.556 1.562 1.109 1.584 (15) - 0.148 0.031 - (16) - 0.148 0.031 -

[0121] According to the above-described embodiments, it is possible to realize a variable magnification optical system that is small in size, yet bright and has good optical performance.

[0122] The above-described examples are merely illustrative examples of the present invention, and the present invention is not limited to these.

[0123] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the variable magnification optical system of this embodiment.

[0124] Although three-group and four-group configurations have been shown as examples of the variable magnification optical system of this embodiment, the present application is not limited to these, and variable magnification optical systems with other group configurations (for example, five groups) can also be configured. Specifically, a lens or lens group may be added to the most object-side or most image-plane-side of the variable magnification optical system of this embodiment. Note that a lens group refers to a portion having at least one lens separated by an air gap that changes when the magnification is changed.

[0125] A single lens group, multiple lens groups, or a partial lens group may be moved in the optical axis direction to function as a focusing lens group that focuses from an object at infinity to a close object. The focusing lens group can also be used for autofocusing, and is suitable for driving a motor (using an ultrasonic motor, etc.) for autofocusing.

[0126] The lens group or partial lens group may be moved so as to have a component in a direction perpendicular to the optical axis, or may be rotated (oscillated) in a plane including the optical axis, to serve as an image stabilization lens group that corrects image blur caused by camera shake.

[0127] 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.

[0128] 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.

[0129] The aperture diaphragm is preferably disposed between the first lens group and the second lens group, but it is also possible to use the lens frame to fulfill that role instead of providing a member serving as an aperture diaphragm.

[0130] 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]

[0131] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group I Image plane S Aperture stop

Claims

1. The lens comprises a first lens group having positive refractive power and a rear lens group having a plurality of lens groups, which are arranged in order from the object side along the optical axis, When changing magnification, the spacing between adjacent lens groups changes, the plurality of lens groups in the rear group are composed of two or three lens groups including a second lens group having positive refractive power and arranged closest to the object side of the rear group, A variable magnification optical system that satisfies the following condition: 0.15<f2 / f1<0.80 1.00<(L1r2+L1r1) / (L1r2-L1r1)<2.50 1.50<(LEr2+LEr1) / (LEr2-LEr1)<3.00 0.30<f2 / fRw<0.65 where f1 is the focal length of the first lens group f2: focal length of the second lens group L1r1: the radius of curvature of the object-side lens surface of the lens arranged closest to the object side in the variable magnification optical system L1r2: the radius of curvature of the image-side lens surface of the lens arranged closest to the object side in the variable magnification optical system LEr1: radius of curvature of the object-side lens surface of the lens arranged closest to the image side in the variable magnification optical system LEr2: radius of curvature of the image-side lens surface of the lens arranged closest to the image side in the variable magnification optical system f2: focal length of the second lens group fRw: composite focal length of the rear group in the wide-angle end state

2. The lens comprises, arranged in order from the object side along the optical axis, a first lens group having positive refractive power, an aperture stop, and a rear group having a plurality of lens groups, When changing magnification, the spacing between adjacent lens groups changes, During magnification change, the first lens group moves along the optical axis together with the aperture stop, the plurality of lens groups in the rear group are composed of two or three lens groups including a second lens group having positive refractive power and arranged closest to the object side of the rear group, During magnification change, the first lens group moves along the optical axis together with the aperture stop. A variable magnification optical system that satisfies the following condition: 0.15<f2 / f1<0.80 1.00<(L1r2+L1r1) / (L1r2-L1r1)<2.50 1.50<(LEr2+LEr1) / (LEr2-LEr1)<3.00 where f1 is the focal length of the first lens group f2: focal length of the second lens group L1r1: the radius of curvature of the object-side lens surface of the lens arranged closest to the object side in the variable magnification optical system L1r2: the radius of curvature of the image-side lens surface of the lens arranged closest to the object side in the variable magnification optical system LEr1: radius of curvature of the object-side lens surface of the lens arranged closest to the image side in the variable magnification optical system LEr2: radius of curvature of the image-side lens surface of the lens arranged closest to the image side in the variable magnification optical system

3. The lens comprises a first lens group having positive refractive power and a rear lens group having a plurality of lens groups, which are arranged in order from the object side along the optical axis, When changing magnification, the spacing between adjacent lens groups changes, the plurality of lens groups in the rear group are composed of two or three lens groups including a second lens group having positive refractive power and arranged closest to the object side of the rear group, the first lens group has a front focusing group that moves along the optical axis during focusing; the rear group has a rear focusing group that moves along the optical axis on a different path from that of the front focusing group during focusing; at least a part of any one of the plurality of lens groups in the rear group constitutes the rear focusing group, A variable magnification optical system that satisfies the following condition: 0.15<f2 / f1<0.80 1.00<(L1r2+L1r1) / (L1r2-L1r1)<2.50 1.50<(LEr2+LEr1) / (LEr2-LEr1)<3.00 0.01<fF2 / (-fF1)<0.30 where f1 is the focal length of the first lens group f2: focal length of the second lens group L1r1: the radius of curvature of the object-side lens surface of the lens arranged closest to the object side in the variable magnification optical system L1r2: the radius of curvature of the image-side lens surface of the lens arranged closest to the object side in the variable magnification optical system LEr1: radius of curvature of the object-side lens surface of the lens arranged closest to the image side in the variable magnification optical system LEr2: radius of curvature of the image-side lens surface of the lens arranged closest to the image side in the variable magnification optical system fF1: focal length of the front focusing group fF2: focal length of the rear focusing group

4. 4. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 1.20<ft / fw<2.00 where ft is the focal length of the variable magnification optical system in the telephoto end state. fw: focal length of the variable magnification optical system in the wide-angle end state

5. 5. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.01<Bfw / TLw<0.20 where Bfw is the back focus of the variable magnification optical system in the wide-angle end state. TLw: total length of the variable magnification optical system in the wide-angle end state

6. 6. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.60<YLE / IHw<1.00 where YLE is the effective diameter of the lens arranged closest to the image side in the variable magnification optical system. IHw: maximum image height of the variable magnification optical system in the wide-angle end state

7. 7. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: FNOw<2.8 where FNOw is the F-number of the variable magnification optical system in the wide-angle end state.

8. 8. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 10.00°<2ωw<35.00° where 2ωw is the total angle of view of the variable magnification optical system in the wide-angle end state.

9. 9. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.30<fw / f1<0.70 where fw is the focal length of the variable magnification optical system in the wide-angle end state f1: focal length of the first lens group

10. A variable magnification optical system according to any one of claims 2 to 9, which satisfies the following conditional expression: 0.30<f2 / fRw<0.65 where f2 is the focal length of the second lens group fRw: composite focal length of the rear group in the wide-angle end state

11. the plurality of lens groups in the rear group include a final lens group arranged closest to the image side of the rear group, 11. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.50<(-fGE) / fw<1.00 where fGE is the focal length of the final lens group. fw: focal length of the variable magnification optical system in the wide-angle end state

12. 12. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 1.00<f1 / fRw<1.80 where f1 is the focal length of the first lens group fRw: composite focal length of the rear group in the wide-angle end state

13. the plurality of lens groups in the rear group include a third lens group arranged adjacent to the image side of the second lens group, 13. The variable magnification optical system according to claim 1, wherein the distance between the second lens group and the third lens group decreases when the magnification is changed from the wide-angle end state to the telephoto end state.

14. an aperture stop disposed between the first lens group and the rear lens group; 14. A variable magnification optical system according to claim 1, wherein the first lens group moves along the optical axis together with the aperture stop during magnification variation.

15. the first lens group has a front focusing group that moves along the optical axis during focusing; the rear group has a rear focusing group that moves along the optical axis on a different path from that of the front focusing group during focusing; 15. A variable magnification optical system according to claim 1, wherein at least a part of any one of the plurality of lens groups in the rear group constitutes the rear-side focusing group.

16. 16. The variable magnification optical system according to claim 15, which satisfies the following condition: -0.30<fF2 / fF1<0.30 where fF1 is the focal length of the front focusing group fF2: focal length of the rear focusing group

17. 16. The variable magnification optical system according to claim 15, which satisfies the following condition: 0.01<fF2 / (-fF1)<0.30 where fF1 is the focal length of the front focusing group fF2: focal length of the rear focusing group

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

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