Optical system and optical apparatus

Abstract

To provide an optical system having less aberration variation during focusing.SOLUTION: The optical system OL consists of, in order from an object, a front group GA, a stop S, and a rear group GB, wherein the front group GA consists of a preceding lens group consisting of one lens group having a positive refractive power, the rear group GB includes a first focusing lens group GF1 having a negative refractive power, a positive lens group having a positive refractive power, a second focusing lens group GF2 having a negative refractive power, and a final lens group GE having a negative refractive power, and upon focusing from an object at infinity to an object at a close distance, the first focusing lens group GF1 and the second focusing lens group GF2 move toward the image plane side along respective different loci, each of the first focusing lens group GF1 and the second focusing lens group GF2 includes one or two lenses, and satisfies the following conditional expressions: 0.862 ≤ f / (-fF1) <1.80, where f is a focal distance of the optical system OL, and fF1 is a focal distance of the first focusing lens group GF1 SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system and an optical instrument. [Background technology]

[0002] Conventionally, optical systems have been proposed in which multiple lens groups are moved along the optical axis to achieve focusing (see, for example, Patent Document 1). In such optical systems, the focusing lens group is heavy, making it difficult to suppress aberration fluctuations during focusing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-155228 Summary of the Invention

[0004] A first optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a front group, a stop, and a rear group, wherein the front group comprises a leading lens group constituted by one lens group having positive refractive power, and the rear group comprises, arranged in order from the rear group closest to the object side, a first focusing lens group having negative refractive power, a positive lens group having positive refractive power, a second focusing lens group having negative refractive power, and a final lens group having negative refractive power, wherein, when focusing from an object at infinity to an object at a close distance, the first focusing lens group and the second focusing lens group move along the optical axis toward the image plane along different trajectories, and both the first focusing lens group and the second focusing lens group are constituted by one or two lenses, and the following conditional expression is satisfied: 0.838≦f / (-fF1)<1.80 where f is the focal length of the optical system. fF1: focal length of the first focusing lens group

[0005] A second optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a leading lens group having positive refractive power, a first focusing lens group having negative refractive power, a positive lens group having positive refractive power, a second focusing lens group having negative refractive power, and a final lens group, wherein, when focusing from an object at infinity to an object at a close distance, the first focusing lens group and the second focusing lens group move along the optical axis toward the image plane along different trajectories, and both the first focusing lens group and the second focusing lens group are composed of one or two lenses, and the following conditional expression is satisfied: 0.838≦f / (-fF1)<1.80 0.35 <fB / (-fF1)≦0.867 where f is the focal length of the optical system. fF1: focal length of the first focusing lens group fB: composite focal length of the lens group arranged closer to the image plane than the first focusing lens group fF1: focal length of the first focusing lens group

[0006] An optical device according to the present invention includes the optical system described above. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram showing the lens configuration of an optical system according to Example 1. [Figure 2] 2A and 2B are diagrams showing various aberrations of the optical system according to Example 1 when focused at infinity and when focused at a close distance, respectively. [Figure 3] FIG. 10 is a diagram showing the lens configuration of an optical system according to a second example. [Figure 4] 4A and 4B are diagrams showing various aberrations of the optical system according to Example 2 when focused on infinity and when focused on a close distance, respectively. [Figure 5] FIG. 10 is a diagram showing the lens configuration of an optical system according to Example 3. [Figure 6] 6A and 6B are diagrams showing various aberrations of the optical system according to Example 3 when focused at infinity and when focused at a close distance, respectively. [Figure 7]FIG. 10 is a diagram showing the lens configuration of an optical system according to Example 4. [Figure 8] 8A and 8B are diagrams showing various aberrations of the optical system according to Example 4 when focused at infinity and when focused at a close distance, respectively. [Figure 9] FIG. 10 is a diagram showing the lens configuration of an optical system according to Example 5. [Figure 10] 10A and 10B are diagrams showing various aberrations of the optical system according to Example 5 when focused on infinity and when focused on a close distance, respectively. [Figure 11] FIG. 13 is a diagram showing the lens configuration of an optical system according to Example 6. [Figure 12] 12A and 12B are diagrams showing various aberrations of the optical system according to Example 6 when focused on infinity and when focused on a close distance, respectively. [Figure 13] FIG. 13 is a diagram showing the lens configuration of an optical system according to Example 7. [Figure 14] 14A and 14B are diagrams showing various aberrations of the optical system according to Example 7 when focused on infinity and when focused on a close distance, respectively. [Figure 15] FIG. 13 is a diagram showing the lens configuration of an optical system according to Example 8. [Figure 16] 16A and 16B are diagrams showing various aberrations of the optical system according to Example 8 when focused on infinity and when focused on a close distance, respectively. [Figure 17] FIG. 13 is a diagram showing the lens configuration of an optical system according to Example 9. [Figure 18] 18A and 18B are diagrams showing various aberrations of the optical system according to Example 9 when focused on infinity and when focused on a close distance, respectively. [Figure 19] FIG. 23 is a diagram showing the lens configuration of an optical system according to Example 10. [Figure 20] 20A and 20B are diagrams showing various aberrations when the optical system according to Example 10 is in the wide-angle end state and focused at infinity and when focused at a close distance, respectively. [Figure 21] 21A and 21B are diagrams showing various aberrations when the optical system according to Example 10 is in the telephoto end state and focused on infinity and when focused on a close distance, respectively. [Figure 22] FIG. 1 is a diagram showing the configuration of a camera including an optical system according to each embodiment. [Figure 23] 4 is a flowchart showing a method for manufacturing the optical system according to the first embodiment. [Figure 24] 10 is a flowchart showing a method for manufacturing an optical system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present invention will be described below. First, a camera (optical device) equipped with an optical system according to each embodiment will be described with reference to FIG. 22. As shown in FIG. 22, 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 an optical system OL 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.

[0009] Light from the subject is collected by the optical system OL 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. The optical system OL shown in FIG. 22 is a schematic representation of an optical system provided in the photographing lens 3, and the lens configuration of the optical system OL is not limited to this configuration.

[0010] Next, an optical system according to a first embodiment will be described. As shown in FIG. 1, an optical system OL(1) as an example of the optical system OL according to the first embodiment is composed of, in order from the object side along the optical axis, a front group GA, a diaphragm (aperture stop) S, and a rear group GB. The rear group GB has a first focusing lens group GF1 with negative refractive power that is located closest to the object side of the rear group GB, and a second focusing lens group GF2 with negative refractive power that is located closer to the image plane than the first focusing lens group GF1. When focusing from an object at infinity to a close-up object, the first focusing lens group GF1 and the second focusing lens group GF2 move along the optical axis toward the image plane along different trajectories.

[0011] According to the first embodiment, it is possible to obtain an optical system with little aberration fluctuation during focusing, and an optical device equipped with this optical system. Furthermore, because the aberration fluctuation during focusing is little, good optical performance can be achieved even with a large aperture. Since it is possible to reduce the weight of each focusing lens group, it is possible to obtain an optical system that supports high-speed autofocus (AF). Since it is possible to simplify the drive mechanism for each focusing lens group, it is possible to reduce the sensitivity of optical performance to manufacturing errors.

[0012] The optical system OL according to the first embodiment may be the variable magnification optical system OL(2) shown in Fig. 3, the optical system OL(3) shown in Fig. 5, the optical system OL(4) shown in Fig. 7, or the optical system OL(5) shown in Fig. 9. Moreover, the optical system OL according to the first embodiment may be the variable magnification optical system OL(6) shown in Fig. 11, the optical system OL(7) shown in Fig. 13, or the optical system OL(10) shown in Fig. 19.

[0013] It is desirable that the optical system OL according to the first embodiment satisfy the following conditional expression (1). 0.30 <STL / TL<0.90 ···(1) However, STL: Distance on the optical axis from aperture S to image plane I TL: Total length of optical system OL

[0014] Conditional expression (1) defines an appropriate relationship between the distance on the optical axis from the aperture stop S to the image plane I and the overall length of the optical system OL. By satisfying conditional expression (1), the exit pupil position can be inferred, and an appropriate range of aperture position can be defined. Furthermore, fluctuations in the angle of view that occur in response to changes in back focus due to manufacturing errors, etc., can be suppressed. Note that in each embodiment, the overall length of the optical system OL is the distance on the optical axis (air-equivalent distance) from the lens surface of the optical system OL closest to the object to the image plane I when focused at infinity.

[0015] If the corresponding value of conditional expression (1) is below the lower limit, the exit pupil becomes closer to the image plane I, so that the inclination angle of the light rays incident on the image plane I becomes steeper, and fluctuations in the angle of view are likely to occur due to changes in the back focus caused by manufacturing errors, etc. The effect of this embodiment can be made more certain by setting the lower limit of conditional expression (1) to 0.33, 0.35, 0.38, 0.40, 0.43, 0.45, 0.48, 0.50, or even 0.52.

[0016] If the corresponding value of conditional expression (1) exceeds the upper limit, the position of the aperture stop S will be inappropriate, causing an imbalance between the upper and lower light rays blocked by the aperture stop S, resulting in a so-called one-sided aperture. Furthermore, the overall length of the optical system OL will be too short, making aberration correction difficult. The effects of this embodiment can be further ensured by setting the upper limit of conditional expression (1) to 0.88, 0.85, 0.83, 0.80, 0.78, or even 0.76.

[0017] In the optical system OL according to the first embodiment, the rear group GB has a positive lens group GP with positive refractive power that is located between the first focusing lens group GF1 and the second focusing lens group GF2, and during focusing from an object at infinity to a close object, it is desirable that the position of the positive lens group GP be fixed with respect to the image surface I. This enables excellent correction of spherical aberration, Petzval sum, and the like.

[0018] In the optical system OL according to the first embodiment, it is desirable that the front group GA comprises a leading lens group GA1 having positive refractive power, and the rear group GB comprises a positive lens group GP having positive refractive power arranged between the first focusing lens group GF1 and the second focusing lens group GF2, and a final lens group GE arranged closer to the image plane than the second focusing lens group GF2. By arranging the multiple focusing lens groups closer to the image plane than the aperture stop S, it is possible to easily align the axes of the multiple focusing lens groups during centering, thereby reducing the sensitivity of optical performance to manufacturing errors. Furthermore, by moving the multiple focusing lens groups during focusing, it is possible to reduce the weight of the focusing lens groups and effectively suppress aberration fluctuations during focusing.

[0019] Next, an optical system according to a second embodiment will be described. As shown in Fig. 1, an optical system OL(1) as an example of the optical system OL according to the second embodiment includes, arranged in order from the object side along the optical axis, a leading lens group GA1 having positive refractive power, a first focusing lens group GF1 having negative refractive power, a positive lens group GP having positive refractive power, a second focusing lens group GF2 having negative refractive power, and a final lens group GE. When focusing from an object at infinity to a close object, the first focusing lens group GF1 and the second focusing lens group GF2 move along the optical axis toward the image plane along different trajectories.

[0020] According to the second embodiment, it is possible to obtain an optical system with little aberration fluctuation during focusing, and an optical device equipped with this optical system. Furthermore, because the aberration fluctuation during focusing is little, good optical performance can be achieved even with a large aperture. Since it is possible to reduce the weight of each focusing lens group, it is possible to obtain an optical system that supports high-speed autofocus (AF). Since it is possible to simplify the drive mechanism for each focusing lens group, it is possible to reduce the sensitivity of optical performance to manufacturing errors.

[0021] The optical system OL according to the second embodiment may be the variable magnification optical system OL(2) shown in Fig. 3, the optical system OL(3) shown in Fig. 5, the optical system OL(4) shown in Fig. 7, or the optical system OL(5) shown in Fig. 9. Furthermore, the optical system OL according to the second embodiment may be the variable magnification optical system OL(6) shown in Fig. 11, the optical system OL(7) shown in Fig. 13, the optical system OL(8) shown in Fig. 15, the optical system OL(9) shown in Fig. 17, or the optical system OL(10) shown in Fig. 19.

[0022] In the optical system OL according to the second embodiment, it is desirable to dispose a diaphragm (aperture stop) S between the leading lens group GA1 and the first focusing lens group GF1. This effectively narrows the light rays incident on the focusing lens group, making it possible to reduce the size and weight of the focusing lens group. It also makes it easier to align the axes of multiple focusing lens groups during centering, reducing the sensitivity of optical performance to manufacturing errors. It also makes it possible to effectively correct fluctuations in the angle of view during focusing.

[0023] It is desirable that the optical system OL according to the second embodiment satisfy the above-mentioned conditional expression (1). By satisfying conditional expression (1), the exit pupil position can be inferred, as in the first embodiment, and the range of appropriate aperture positions can be defined. Furthermore, fluctuations in the angle of view in response to changes in back focus due to manufacturing errors and the like can be suppressed. The effects of this embodiment can be further ensured by setting the lower limit of conditional expression (1) to 0.33, 0.35, 0.38, 0.40, 0.43, 0.45, 0.48, 0.50, or even 0.52. The effects of this embodiment can be further ensured by setting the upper limit of conditional expression (1) to 0.88, 0.85, 0.83, 0.80, 0.78, or even 0.76.

[0024] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (2). 0.50 <fA / f<2.00 ···(2) where fA is the focal length of the first lens group GA1 f: focal length of optical system OL

[0025] Conditional expression (2) defines an appropriate relationship between the focal length of the leading lens group GA1 and the focal length of the optical system OL. By satisfying conditional expression (2), chromatic aberration can be effectively corrected and the overall length of the optical system OL can be shortened.

[0026] If the value corresponding to conditional expression (2) falls outside the above range, it becomes difficult to correct chromatic aberration and to shorten the overall length of the optical system OL. By setting the lower limit of conditional expression (2) to 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, or even 0.95, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (2) to 1.90, 1.80, 1.75, 1.70, 1.65, 1.60, 1.55, 1.50, or even 1.45, the effects of each embodiment can be further ensured.

[0027] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (3). 0.50 <fA / (-fF1)<1.50 ···(3) where fA is the focal length of the first lens group GA1 fF1: focal length of the first focusing lens group GF1

[0028] Conditional expression (3) defines an appropriate relationship between the focal length of the leading lens group GA1 and the focal length of the first focusing lens group GF1. By satisfying conditional expression (3), it is possible to reduce fluctuations in aberration and angle of view during focusing.

[0029] If the value corresponding to conditional expression (3) falls outside the above range, it becomes difficult to suppress aberration fluctuations and fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (3) to 0.53, 0.55, 0.58, 0.60, 0.63, 0.65, 0.58, 0.70, or even 0.73, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (3) to 1.48, 1.45, 1.43, 1.40, 1.38, 1.35, or even 1.33, the effects of each embodiment can be more reliably achieved.

[0030] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (4). 0.35 <fB / (-fF1)<1.50 ···(4) where fB is the composite focal length of the lens group arranged closer to the image plane than the first focusing lens group GF1 fF1: focal length of the first focusing lens group GF1

[0031] Conditional expression (4) defines an appropriate relationship between the composite focal length of the lens groups located closer to the image plane than the first focusing lens group GF1 and the focal length of the first focusing lens group GF1. By satisfying conditional expression (4), it is possible to reduce fluctuations in aberration and angle of view during focusing.

[0032] If the value corresponding to conditional expression (4) falls outside the above range, it becomes difficult to suppress aberration fluctuations and fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (4) to 0.38, 0.40, 0.43, 0.45, 0.48, 0.50, 0.53, 0.55, 0.58, or even 0.60, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (4) to 1.45, 1.40, 1.35, 1.30, 1.25, 1.20, 1.18, 1.20, 1.15, 1.13, or even 1.10, the effects of each embodiment can be more reliably achieved.

[0033] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (5). -2.00<(-fE) / f<15.00 (5) where fE is the focal length of the final lens group GE f: focal length of optical system OL

[0034] Conditional expression (5) defines an appropriate relationship between the focal length of the final lens group GE and the focal length of the optical system OL. By satisfying conditional expression (5), shading can be suppressed and the overall length of the optical system OL can be shortened.

[0035] If the value corresponding to conditional expression (5) falls outside the above range, it becomes difficult to suppress shading and to shorten the overall length of the optical system OL. The effects of each embodiment can be further ensured by setting the lower limit of conditional expression (5) to -1.80, -1.50, -1.00, -0.50, -0.10, 0.10, 0.50, 0.65, 0.80, or even 0.90. Furthermore, the effects of each embodiment can be further ensured by setting the upper limit of conditional expression (5) to 14.80, 12.00, 10.00, 8.50, 7.50, 6.00, 5.00, 4.50, or even 4.00.

[0036] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (6). -1.00 <fP / (-fE)<1.50 ···(6) However, fP is the focal length of the positive lens group GP. fE: focal length of the final lens group GE

[0037] Conditional expression (6) defines an appropriate relationship between the focal length of the positive lens group GP and the focal length of the final lens group GE. By satisfying conditional expression (6), it is possible to effectively suppress aberration fluctuations during focusing, and it is possible to locate the exit pupil farther from the image plane I.

[0038] If the value corresponding to conditional expression (6) falls outside the above range, it becomes difficult to suppress aberration fluctuations during focusing. By setting the lower limit of conditional expression (6) to -0.80, -0.50, -0.25, -0.10, 0.01, 0.05, 0.12, or even 0.15, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (6) to 1.40, 1.25, 1.00, 0.85, 0.70, 0.65, 0.60, or even 0.55, the effects of each embodiment can be more reliably achieved.

[0039] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (7). 1.10<(-fF1) / fP<3.20 (7) where fF1 is the focal length of the first focusing lens group GF1 fP: focal length of the positive lens group GP

[0040] Conditional expression (7) defines an appropriate relationship between the focal length of the first focusing lens group GF1 and the focal length of the positive lens group GP. By satisfying conditional expression (7), the occurrence of spherical aberration and axial chromatic aberration can be effectively suppressed.

[0041] If the value corresponding to conditional expression (7) falls outside the above range, it becomes difficult to correct spherical aberration and axial chromatic aberration. By setting the lower limit of conditional expression (7) to 1.15, 1.20, 1.25, 1.30, 1.33, 1.35, 1.38, 1.40, 1.43, or even 1.45, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (7) to 3.15, 3.10, 3.05, or even 3.00, the effects of each embodiment can be more reliably achieved.

[0042] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (8). 0.30 <fP / f<1.00 ···(8) However, fP is the focal length of the positive lens group GP. f: focal length of optical system OL

[0043] Condition (8) defines an appropriate relationship between the focal length of the positive lens group GP and the focal length of the optical system OL. By satisfying condition (8), spherical aberration, Petzval sum, etc. can be effectively corrected.

[0044] If the value corresponding to conditional expression (8) falls outside the above range, it becomes difficult to correct spherical aberration, Petzval sum, etc. By setting the lower limit of conditional expression (8) to 0.33, 0.35, 0.38, 0.40, or even 0.43, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (8) to 0.98, 0.95, 0.93, 0.90, or even 0.88, the effects of each embodiment can be more reliably achieved.

[0045] In the optical systems OL according to the first and second embodiments, it is desirable that the positive lens group GP has, arranged in order from the object side along the optical axis, a negative lens, a first positive lens, and a second positive lens. This makes it possible to reduce the size of the optical system OL and to locate the exit pupil farther from the image surface I. It also makes it possible to effectively correct various aberrations, including spherical aberration.

[0046] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (9). 0.10 <fF1 / fF2<2.00 ···(9) where fF1 is the focal length of the first focusing lens group GF1 fF2: focal length of the second focusing lens group GF2

[0047] Conditional expression (9) defines an appropriate relationship between the focal length of the first focusing lens group GF1 and the focal length of the second focusing lens group GF2. By satisfying conditional expression (9), spherical aberration, curvature of field, etc. can be effectively corrected.

[0048] If the value corresponding to conditional expression (9) falls outside the above range, it becomes difficult to correct spherical aberration, curvature of field, etc. By setting the lower limit of conditional expression (9) to 0.13, 0.15, 0.18, 0.20, 0.23, or even 0.25, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (9) to 1.98, 1.95, 1.93, 1.90, 1.75, 1.50, 1.40, 1.25, 1.10, or even 1.00, the effects of each embodiment can be more reliably achieved.

[0049] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (10). 0.50 <f / (-fF1)<1.80 ···(10) where f is the focal length of the optical system OL fF1: focal length of the first focusing lens group GF1

[0050] Condition (10) defines an appropriate relationship between the focal length of the optical system OL and the focal length of the first focusing lens group GF1. By satisfying condition (10), chromatic aberration, curvature of field, etc. can be effectively corrected.

[0051] If the value corresponding to conditional expression (10) falls outside the above range, it becomes difficult to correct chromatic aberration, curvature of field, etc. By setting the lower limit of conditional expression (10) to 0.53, 0.55, 0.58, 0.60, 0.63, 0.65, 0.68, 0.70, 0.73, or even 0.75, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (10) to 1.78, 1.75, 1.73, 1.70, 1.50, 1.40, or even 1.20, the effects of each embodiment can be more reliably achieved.

[0052] In the optical systems OL according to the first and second embodiments, it is desirable that the first focusing lens group GF1 be made up of one negative lens component. This makes the first focusing lens group GF1 lightweight, enabling high-speed focusing from an object at infinity to a close-up object. Note that in each embodiment, the lens component refers to a single lens or a cemented lens.

[0053] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (11). -2.50<(rF12+rF11) / (rF12-rF11)<0.00 ···(11) where rF11: radius of curvature of the lens surface closest to the object in the first focusing lens group GF1 rF12: radius of curvature of the lens surface closest to the image plane in the first focusing lens group GF1

[0054] Condition (11) defines an appropriate range for the shape factor of the lenses that make up the first focusing lens group GF1. By satisfying condition (11), spherical aberration, coma, and other aberrations can be effectively corrected.

[0055] If the value corresponding to conditional expression (11) falls outside the above range, it becomes difficult to correct spherical aberration, coma, etc. By setting the lower limit of conditional expression (11) to -2.45, -2.40, -2.35, -2.30, -2.28, -2.25, or even -2.23, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (11) to -0.05, -0.10, -0.15, -0.20, -0.25, -0.30, -0.35, -0.40, -0.45, -0.50, or even -0.55, the effects of each embodiment can be more reliably achieved.

[0056] In the optical systems OL according to the first and second embodiments, it is desirable that the second focusing lens group GF2 be made up of one negative lens component, which makes the second focusing lens group GF2 lighter, thereby enabling high-speed focusing from an object at infinity to an object at close range.

[0057] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (12). 0.05 <Bf / TL<0.80 ···(12) However, Bf is the back focus of the optical system OL. TL: Total length of optical system OL

[0058] Conditional expression (12) defines an appropriate relationship between the back focus of the optical system OL and the overall length of the optical system OL. By satisfying conditional expression (12), spherical aberration, coma, and the like can be corrected well. In each embodiment, the back focus of the optical system OL is defined as the distance on the optical axis (air-equivalent distance) from the lens surface of the optical system OL closest to the image plane to the image plane I when focused at infinity.

[0059] If the corresponding value of conditional expression (12) falls below the lower limit, the exit pupil will be too close to the image plane I, causing vignetting of light rays at the image plane I. Attempts to avoid this are undesirable, as it may ultimately make it difficult to correct off-axial aberrations, particularly coma. Setting the lower limit of conditional expression (12) to 0.06, or even 0.07, can further ensure the effects of each embodiment.

[0060] If the corresponding value of conditional expression (12) exceeds the upper limit, the overall length of the optical system OL becomes too short, making it difficult to correct spherical aberration, coma, etc. Furthermore, the back focus of the optical system OL becomes too long, making the optical system OL larger. By setting the upper limit of conditional expression (12) to 0.75, 0.70, 0.65, 0.50, 0.40, 0.35, 0.30, or even 0.25, the effects of each embodiment can be more reliably achieved.

[0061] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (13). -0.80<(rR2+rR1) / (rR2-rR1)<2.50 ···(13) where rR1 is the radius of curvature of the object-side lens surface of the lens arranged closest to the image plane in the optical system OL. rR2: Radius of curvature of the lens surface closest to the image plane in the optical system OL

[0062] Condition (13) defines an appropriate range for the shape factor of the lens element located closest to the image plane in optical system OL. By satisfying condition (13), coma and other aberrations can be effectively corrected, and ghosting can be suppressed.

[0063] If the value corresponding to conditional expression (13) falls outside the above range, it becomes difficult to correct coma aberration and suppress ghosting. By setting the lower limit of conditional expression (13) to -0.75, -0.70, -0.65, -0.60, -0.50, -0.30, 0.30, 0.50, 0.80, or even 0.95, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (13) to 2.45, 2.35, 2.15, 2.00, 1.85, or even 1.70, the effects of each embodiment can be further ensured.

[0064] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (14). 0.01<1 / βF1<0.60 (14) where βF1 is the lateral magnification of the first focusing lens group GF1 when focusing on an object at infinity

[0065] Conditional expression (14) defines an appropriate range for the lateral magnification of the first focusing lens group GF1 when focusing on an object at infinity. By satisfying conditional expression (14), various aberrations such as spherical aberration and curvature of field can be effectively corrected when focusing on an object at infinity.

[0066] If the value corresponding to conditional expression (14) falls outside the above range, it becomes difficult to correct various aberrations, such as spherical aberration and curvature of field, when focusing on an object at infinity. By setting the lower limit of conditional expression (14) to 0.02, 0.05, or even 0.08, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (14) to 0.58, 0.55, 0.53, 0.50, 0.48, 0.45, or even 0.43, the effects of each embodiment can be more reliably achieved.

[0067] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (15). 0.50<1 / βF2<0.95 (15) where βF2 is the lateral magnification of the second focusing lens group GF2 when focusing on an object at infinity.

[0068] Conditional expression (15) defines an appropriate range for the lateral magnification of the second focusing lens group GF2 when focusing on an object at infinity. By satisfying conditional expression (15), various aberrations such as spherical aberration and curvature of field can be effectively corrected when focusing on an object at infinity.

[0069] If the value corresponding to conditional expression (15) falls outside the above range, it becomes difficult to correct various aberrations, such as spherical aberration and curvature of field, when focusing on an object at infinity. By setting the lower limit of conditional expression (15) to 0.53, 0.55, 0.58, or even 0.60, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (15) to 0.94, 0.92, 0.90, or even 0.85, the effects of each embodiment can be more reliably achieved.

[0070] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (16). {βF1+(1 / βF1)} -2 <0.20 (16) where βF1 is the lateral magnification of the first focusing lens group GF1 when focusing on an object at infinity

[0071] Conditional expression (16) defines an appropriate range for the lateral magnification of the first focusing lens group GF1 when focusing on an object at infinity. By satisfying conditional expression (16), various aberrations such as spherical aberration and curvature of field can be effectively corrected when focusing on an object at infinity.

[0072] If the value corresponding to conditional expression (16) is outside the above range, it becomes difficult to correct various aberrations such as spherical aberration and curvature of field when focusing on an object at infinity. By setting the upper limit of conditional expression (16) to 0.18, 0.16, 0.15, or even 0.14, the effects of each embodiment can be more reliably achieved.

[0073] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (17). {βF2+(1 / βF2)} -2 ≦0.25 (17) where βF2 is the lateral magnification of the second focusing lens group GF2 when focusing on an object at infinity.

[0074] Conditional expression (17) defines an appropriate range for the lateral magnification of the second focusing lens group GF2 when focusing on an object at infinity. By satisfying conditional expression (17), various aberrations such as spherical aberration and curvature of field when focusing on an object at infinity can be effectively corrected. If the value corresponding to conditional expression (17) falls outside the above range, it becomes difficult to correct various aberrations such as spherical aberration and curvature of field when focusing on an object at infinity.

[0075] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (18). 0.15 <MF1 / MF2<0.80 ···(18) where MF1 is the absolute value of the movement of the first focusing lens group GF1 when focusing from an object at infinity to an object at a close distance. MF2: Absolute value of the movement of the second focusing lens group GF2 when focusing from an object at infinity to an object at a close distance

[0076] Conditional expression (18) defines an appropriate relationship between the amount of movement of the first focusing lens group GF1 and the amount of movement of the second focusing lens group GF2 when focusing from an object at infinity to an object at a close distance. By satisfying conditional expression (18), spherical aberration, coma, curvature of field, etc. can be effectively corrected.

[0077] If the value corresponding to conditional expression (18) falls outside the above range, it becomes difficult to correct spherical aberration, coma, field curvature, etc. By setting the lower limit of conditional expression (18) to 0.16, 0.18, 0.20, or even 0.22, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (18) to 0.78, 0.75, 0.73, 0.70, or even 0.68, the effects of each embodiment can be more reliably achieved.

[0078] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (19). 20.00°<2ω<40.00° ···(19) However, 2ω: full field angle of optical system OL

[0079] Conditional expression (19) defines an appropriate range for the total angle of view of the optical system OL. Satisfying conditional expression (19) is preferable because it provides an optical system with a wide angle of view. By setting the lower limit of conditional expression (19) to 22.00°, 24.00°, 26.00°, or even 27.00°, the effects of each embodiment can be further ensured. Furthermore, by setting the upper limit of conditional expression (19) to 38.00°, 37.00°, or even 36.00°, the effects of each embodiment can be further ensured.

[0080] It is desirable that the optical systems OL according to the first and second embodiments satisfy the following conditional expression (20). 0.08 <Bf / f<1.20 ···(20) However, Bf is the back focus of the optical system OL. f: focal length of optical system OL

[0081] Conditional expression (20) defines an appropriate relationship between the back focus of the optical system OL and the focal length of the optical system OL. By satisfying conditional expression (20), it is possible to obtain an optical system with a short back focus while effectively suppressing the occurrence of various aberrations. By setting the lower limit of conditional expression (20) to 0.09, 0.10, 0.11, or even 0.12, the effects of each embodiment can be more reliably achieved. Furthermore, by setting the upper limit of conditional expression (20) to 1.18, 1.15, 1.13, 1.10, 1.08, 1.05, or even 1.03, the effects of each embodiment can be more reliably achieved.

[0082] Next, a manufacturing method of the optical system OL according to the first embodiment will be outlined with reference to FIG. 23. First, the front group GA, the aperture stop (aperture stop) S, and the rear group GB are arranged, in order from the object side along the optical axis (Step ST1). Next, the first focusing lens group GF1 having negative refractive power is arranged closest to the object side of the rear group GB, and the second focusing lens group GF2 having negative refractive power is arranged closer to the image plane side than the first focusing lens group GF1 of the rear group GB (Step ST2). Then, the lenses are arranged within the lens barrel so that the first focusing lens group GF1 and the second focusing lens group GF2 move along different trajectories toward the image plane side along the optical axis when focusing from an object at infinity to a close object (Step ST3). This manufacturing method makes it possible to manufacture an optical system with minimal aberration fluctuation during focusing.

[0083] Next, a manufacturing method of the optical system OL according to the second embodiment will be outlined with reference to FIG. 24. First, a leading lens group GA1 having positive refractive power, a first focusing lens group GF1 having negative refractive power, a positive lens group GP having positive refractive power, a second focusing lens group GF2 having negative refractive power, and a final lens group GE are arranged in this order along the optical axis from the object side (step ST11). Then, the lenses are arranged in the lens barrel so that, when focusing from an object at infinity to an object at close range, the first focusing lens group GF1 and the second focusing lens group GF2 move along different trajectories toward the image plane along the optical axis (step ST12). This manufacturing method makes it possible to manufacture an optical system with little aberration fluctuation during focusing. [Example]

[0084] Optical systems OL according to examples of each embodiment will be described below with reference to the drawings. Examples 1 to 7 and 10 correspond to the first embodiment, while Examples 1 to 10 correspond to the second embodiment. FIGS. 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19 are cross-sectional views showing the configurations and refractive power distributions of optical systems OL {OL(1) to OL(10)} according to Examples 1 to 10. In the cross-sectional views of the optical systems OL(1) to OL(10) according to Examples 1 to 10, arrows indicate the direction of movement of each lens group along the optical axis when focusing from infinity to a close-up object. In the cross-sectional view of the optical system OL(10) according to Example 10, arrows indicate 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).

[0085] In these figures (FIGS. 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19), each lens group is represented by a combination of the symbol G and a number, and each lens is represented by a combination of the symbol L and a number. In this case, to prevent the symbols and numbers from becoming too numerous and complicated, each example uses its own 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.

[0086] Tables 1 to 10 are shown below, with Table 1 showing data on the various specifications for Example 1, Table 2 for Example 2, Table 3 for Example 3, Table 4 for Example 4, Table 5 for Example 5, Table 6 for Example 6, Table 7 for Example 7, Table 8 for Example 8, Table 9 for Example 9, and Table 10 for Example 10. 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.

[0087] 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 (units: °, where ω is half the angle of view), and Y is the 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 on the optical axis to image plane I when focused at infinity (back focus). TL(a) is the distance on the optical axis (air-equivalent distance) from the lens surface closest to the object in the optical system to image plane I when focused at infinity. Bf(a) is the distance on the optical axis (air-equivalent distance) from the lens surface closest to the image plane in the optical system to image plane I when focused at infinity. Note that if the optical system is a variable magnification optical system, these values ​​are shown for each of the magnification states: wide-angle end (W), mid-focal length (M), and telephoto end (T).

[0088] In the table of [Overall Specifications], fA indicates the focal length of the leading lens group. fB indicates the combined focal length of the lens group arranged closer to the image plane than the first focusing lens group. βF1 indicates the lateral magnification of the first focusing lens group when focusing on an object at infinity. βF2 indicates the lateral magnification of the second focusing lens group when focusing on an object at infinity. MF1 indicates the absolute value of the movement amount of the first focusing lens group when focusing from an object at infinity to a close object. MF2 indicates the absolute value of the movement amount of the second focusing lens group when focusing from an object at infinity to a close object.

[0089] In the [Lens Specifications] table, the surface number indicates the order of the optical surfaces 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 "∞" in the radius of curvature indicates a plane or an aperture, and (stop S) indicates the aperture stop S. The refractive index of air, nd = 1.00000, is omitted.

[0090] The [Variable Distance Data] table shows the surface spacing at surface number i where the surface spacing is (Di) in the [Lens Specifications] table. If the optical system is not a variable magnification optical system, in the [Variable Distance Data] table, f shows the focal length of the entire lens system, and β shows the shooting magnification. Also, D0 shows the distance from the object to the optical surface in the optical system closest to the object. If the optical system is a variable magnification optical system, the [Variable Distance Data] table shows the surface spacing at surface number i where the surface spacing is (Di) in the [Lens Specifications] table, corresponding to each of the magnification states: wide-angle end (W), mid-focal length (M), and telephoto end (T).

[0091] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0092] 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.

[0093] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0094] (First Example) The first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. 1 illustrates the lens configuration of the optical system according to the first embodiment. The optical system OL(1) according to the first embodiment is composed of, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of the lens group, and this also applies to all the following examples.

[0095] An aperture diaphragm S is disposed between the first lens group G1 and the second lens group G2. During focusing, the position of the aperture diaphragm S is fixed relative to the image plane I. In this embodiment, the first lens group G1 constitutes the front group GA, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0096] 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 positive meniscus lens L12 with a convex surface facing the object side, a cemented lens formed by cementing a positive meniscus lens L13 with a convex surface facing the object side and a negative meniscus lens L14 with a convex surface facing the object side, a negative meniscus lens L15 with a convex surface facing the object side, and a positive meniscus lens L16 with a convex surface facing the object side. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0097] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a biconcave negative lens L31 and a biconvex positive lens L32, a biconvex positive lens L33, and a biconvex positive lens L34. The fourth lens group G4 is composed of a biconcave negative lens L41.

[0098] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a biconvex positive lens L51 and a negative meniscus lens L52 with its concave surface facing the object side, and a negative meniscus lens L53 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.

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

[0100] (Table 1) [Overall specifications] f=87.000 fA=89.351 FNO=1.424 fB=64.417 2ω=28.285 βF1=2.601 Y=21.600 βF2=1.125 TL=129.013 MF1=12.719 Bf=1.000 MF2=8.237 TL(a)=128.468 Bf(a)=11.168 [Lens specifications] Surface number RD nd νd 1 69.6342 5.430 1.9591 17.47 2 132.1539 0.116 3 55.3642 5.244 2.0010 29.13 4 89.6665 0.100 5 40.4445 8.778 1.5503 75.49 6 140.0000 1.200 1.8548 24.80 7 29.5861 5.360 8 63.3783 1.200 1.9229 20.88 9 31.8132 0.100 10 31.2943 8.078 1.7292 54.67 11 237.3897 2.787 12∞ (D12) (Aperture S) 13 438.3400 1.200 1.5163 64.14 14 38.4472 (D14) 15 -65.9934 1.200 1.7783 23.91 16 39.9168 8.673 1.8040 46.53 17 -723.3882 0.100 18 70.0000 9.587 1.8160 46.62 19 -124.9732 0.100 20 135.5192 4.257 1.9591 17.47 21 -631.3761 (D21) 22 -255.5306 1.200 1.6989 30.13 23 1196.1373 (D23) 24 148.6618 10.553 1.9591 17.47 25 -40.7482 1.000 1.8929 20.36 26 -348.6817 5.247 27 -43.6865 1.200 1.7783 23.91 28 -175.9036 9.113 29 ∞ 1.600 1.5168 63.88 30∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=87.000 β=-0.034 β=-0.126 D0 ∞ 2570.805 728.956 D12 1.500 4.805 14.219 D14 19.979 16.674 7.260 D21 2.293 4.042 10.530 D23 10.820 9.071 2.583 [Lens group data] Group starting plane focal length G1 1 89.351 G2 13 -81.705 G3 15 54.836 G4 22 -301.138 G5 24 -611.471

[0101] FIG. 2A shows various aberration diagrams for the optical system of Example 1 when focusing at infinity. FIG. 2B shows various aberration diagrams for the optical system of Example 1 when focusing at close distances. In each aberration diagram for when focusing at infinity, FNO indicates the F-number, and Y indicates the image height. In each aberration diagram for when focusing at close distances, NA indicates the numerical aperture, and Y indicates the image height. Note that the spherical aberration diagram shows the F-number or numerical aperture value corresponding to the maximum aperture, the astigmatism diagram and distortion diagram show the maximum image height, and the coma diagram shows 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.

[0102] From the various aberration diagrams, it can be seen that the optical system according to Example 1 has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing at infinity to focusing at close distances.

[0103] (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 optical system according to the second example. The optical system OL(2) according to the second example is composed of, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I.

[0104] An aperture diaphragm S is disposed between the first lens group G1 and the second lens group G2. During focusing, the position of the aperture diaphragm S is fixed relative to the image plane I. In this embodiment, the first lens group G1 constitutes the front group GA, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0105] 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 positive meniscus lens L12 with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L13 and a biconcave negative lens L14, and a positive meniscus lens L15 with a convex surface facing the object side. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0106] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a negative meniscus lens L31 with a convex surface facing the object side and a positive meniscus lens L32 with a convex surface facing the object side, and a biconvex positive lens L33. The fourth lens group G4 is composed of a negative meniscus lens L41 with a convex surface facing the object side.

[0107] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L51 with its convex surface facing the object side and a negative 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.

[0108] Table 2 below lists the values ​​of the specifications of the optical system according to the second example.

[0109] (Table 2) [Overall specifications] f=84.853 fA=83.808 FNO=1.855 fB=70.031 2ω=28.002 βF1=4.398 Y=21.600 βF2=1.236 TL=114.050 MF1=8.031 Bf=1.000 MF2=5.000 TL(a)=113.505 Bf(a)=11.205 [Lens specifications] Surface number RD nd νd 1 57.5903 6.716 1.8081 22.76 2 250.0000 4.134 3 54.4191 3.242 1.7725 49.60 4 87.8376 0.100 5 42.6165 6.392 1.4560 91.37 6 -1029.0613 1.200 2.0007 25.46 7 30.7264 7.020 8 33.1538 7.106 1.4978 82.57 9 2847.8763 2.046 10∞ (D10) (S aperture) 11 1361.3846 1.200 1.5530 55.07 12 35.8243 (D12) 13 105.7816 1.200 1.8052 25.46 14 30.0129 5.549 1.7292 54.67 15 177.6261 7.465 16 70.0000 6.745 2.0007 25.46 17 -91.9564 (D17) 18 135.9285 1.200 1.6730 38.26 19 50.2105 (D19) 20 85.3901 2.439 2.0010 29.13 21 157.8735 6.189 22 -36.1082 4.843 1.8081 22.76 23 -200.0000 9.150 24 ∞ 1.600 1.5168 63.88 25∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=84.853 β=-0.034 β=-0.120 D0 ∞ 2544.448 725.082 D10 1.500 3.593 9.531 D12 11.802 9.709 3.771 D17 6.374 7.694 11.374 D19 7.839 6.518 2.839 [Lens group data] Group starting plane focal length G1 1 83.808 G2 11 -66.556 G3 13 40.059 G4 18 -118.979 G5 20 -84.660

[0110] Fig. 4(A) is a diagram showing various aberrations of the optical system according to Example 2 when focusing at infinity. Fig. 4(B) is a diagram showing various aberrations of the optical system according to Example 2 when focusing at close range. From the diagrams of various aberrations, it can be seen that the optical system according to Example 2 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close range.

[0111] (Third Example) Example 3 will be described with reference to FIGS. 5 to 6 and Table 3. FIG. 5 shows the lens configuration of the optical system according to Example 3. The optical system OL(3) according to Example 3 is composed of, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I.

[0112] An aperture diaphragm S is disposed between the first lens group G1 and the second lens group G2. During focusing, the position of the aperture diaphragm S is fixed relative to the image plane I. In this embodiment, the first lens group G1 constitutes the front group GA, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0113] 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 positive meniscus lens L12 with a convex surface facing the object side, and a cemented lens formed by cementing a biconvex positive lens L13 and a biconcave negative lens L14. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0114] The third lens group G3 is composed of a biconvex positive lens L31, and the fourth lens group G4 is composed of a negative meniscus lens L41 with its convex surface facing the object side.

[0115] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L51 with its convex surface facing the object side and a negative 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.

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

[0117] (Table 3) [Overall specifications] f=82.010 fA=102.479 FNO=2.060 fB=82.146 2ω=28.969 βF1=2.495 Y=21.600 βF2=1.406 TL=90.023 MF1=10.381 Bf=1.000 MF2=3.680 TL(a)=89.478 Bf(a)=17.858 [Lens specifications] Surface number RD nd νd 1 46.5771 5.350 1.7725 49.60 2 179.4303 0.100 3 40.3285 4.836 1.4970 81.61 4 129.0466 0.100 5 33.5684 6.218 1.4560 91.37 6 -229.0734 1.000 1.9004 37.37 7 29.9047 5.182 8∞ (D8) (S aperture) 9 88.7347 1.000 1.4875 70.23 10 33.2383 (D10) 11 40.9864 8.072 1.7130 53.87 12 -66.9077 (D12) 13 159.0319 1.157 1.5814 40.75 14 37.2505 (D14) 15 46.6687 2.874 1.8590 22.73 16 78.4005 7.093 17 -26.5540 3.000 1.9037 31.31 18 -63.6154 15.803 19 ∞ 1.600 1.5168 63.88 20∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=82.010 β=-0.032 β=-0.113 D0 ∞ 2519.887 756.709 D8 1.066 3.911 11.447 D10 17.056 14.211 6.675 D12 1.148 2.146 4.829 D14 6.369 5.372 2.688 [Lens group data] Group starting plane focal length G1 1 102.479 G2 9 -109.666 G3 11 36.793 G4 13 -83.956 G5 15 -101.166

[0118] Fig. 6(A) is a diagram showing various aberrations of the optical system according to Example 3 when focusing at infinity. Fig. 6(B) is a diagram showing various aberrations of the optical system according to Example 3 when focusing at close range. From the diagrams of various aberrations, it can be seen that the optical system according to Example 3 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close range.

[0119] (Fourth Example) Example 4 will be described with reference to FIGS. 7 to 8 and Table 4. FIG. 7 illustrates the lens configuration of an optical system according to Example 4. The optical system OL(4) according to Example 4 includes, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I.

[0120] An aperture diaphragm S is disposed between the first lens group G1 and the second lens group G2. During focusing, the position of the aperture diaphragm S is fixed relative to the image plane I. In this embodiment, the first lens group G1 constitutes the front group GA, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0121] 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 formed by cementing 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, and a cemented lens formed by cementing a biconvex positive lens L14 and a biconcave negative lens L15. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0122] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L31 with a concave surface facing the object side, a positive meniscus lens L32 with a concave surface facing the object side, and a biconvex positive lens L33. The fourth lens group G4 is composed of a negative meniscus lens L41 with a convex surface facing the object side.

[0123] 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 convex surface facing the object side, a positive meniscus lens L52 with its convex surface facing the object side, and a negative meniscus lens L53 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.

[0124] Table 4 below lists the values ​​of the specifications of the optical system according to the fourth example.

[0125] (Table 4) [Overall specifications] f=84.453 fA=118.522 FNO=1.242 fB=61.307 2ω=28.622 βF1=3.780 Y=21.600 βF2=1.316 TL=130.011 MF1=10.784 Bf=1.000 MF2=4.592 TL(a)=129.465 Bf(a)=11.185 [Lens specifications] Surface number RD nd νd 1 73.2143 10.224 1.8929 20.36 2 453.0360 0.100 3 54.5976 9.054 1.5503 75.49 4 258.6524 1.000 1.7283 28.46 5 39.1638 1.660 6 45.1558 12.609 1.5928 68.62 7 -100.3906 1.000 1.9229 20.88 8 119.0758 4.000 9∞ (D9) (S aperture) 10 361.2899 1.000 1.5530 55.07 11 47.0735 (D11) 12 -36.4250 1.300 1.6398 34.47 13 -49.6895 0.100 14 -131.6092 5.891 1.7292 54.67 15 -54.7849 0.100 16 50.6772 14.609 1.7725 49.60 17 -230.5704 (D17) 18 113.4024 1.000 1.8081 22.74 19 52.3424 (D19) 20 89.2568 1.000 1.9229 20.88 21 36.4463 0.100 22 36.3836 9.726 1.9591 17.47 23 183.6004 8.074 24 -38.1283 1.000 1.7408 27.79 25 -98.0949 9.130 26 ∞ 1.600 1.5168 63.88 27∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=84.453 β=-0.043 β=-0.087 D0 ∞ 2018.279 1007.763 D9 2.000 6.974 12.784 D11 21.625 16.651 10.841 D17 2.000 4.186 6.592 D19 9.109 6.923 4.518 [Lens group data] Group starting plane focal length G1 1 118.522 G2 10 -97.991 G3 12 43.900 G4 18 -121.185 G5 20 -251.050

[0126] Fig. 8(A) is a diagram showing various aberrations when the optical system according to Example 4 is focused at infinity. Fig. 8(B) is a diagram showing various aberrations when the optical system according to Example 4 is focused at close distances. From the diagrams of various aberrations, it can be seen that the optical system according to Example 4 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close distances.

[0127] (Fifth Example) Example 5 will be described with reference to FIGS. 9 and 10 and Table 5. FIG. 9 illustrates the lens configuration of an optical system according to Example 5. The optical system OL(5) according to Example 5 includes, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I.

[0128] An aperture diaphragm S is disposed between the first lens group G1 and the second lens group G2. During focusing, the position of the aperture diaphragm S is fixed relative to the image plane I. In this embodiment, the first lens group G1 constitutes the front group GA, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0129] 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 formed by cementing a biconvex positive lens L12 and a biconcave negative lens L13, and a cemented lens formed by cementing a negative meniscus lens L14 with a convex surface facing the object side and a positive meniscus lens L15 with a convex surface facing the object side. The second lens group G2 is composed of, in order from the object side, a cemented lens having negative refractive power formed by cementing a positive meniscus lens L21 with a concave surface facing the object side and a biconcave negative lens L22.

[0130] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L31 and a negative meniscus lens L32 with its concave surface facing the object side. The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens L41 and a biconcave negative lens L42 cemented together to form a cemented lens with negative refractive power.

[0131] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a negative meniscus lens L51 with its convex surface facing the object side and a biconvex positive lens L52, and a negative meniscus lens L53 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.

[0132] Table 5 below lists the values ​​of the specifications of the optical system according to the fifth example.

[0133] (Table 5) [Overall specifications] f=68.369 fA=75.680 FNO=1.850 fB=52.672 2ω=35.083 βF1=6.768 Y=21.600 βF1=1.291 TL=116.082 MF1=11.502 Bf=1.000 MF2=2.759 TL(a)=115.537 Bf(a)=11.055 [Lens specifications] Surface number RD nd νd 1 113.3605 3.581 1.9229 18.90 2 259.4789 2.000 3 64.8154 7.756 1.7495 35.28 4 -305.8877 1.000 1.9229 18.90 5 89.4171 9.650 6 42.6939 1.000 1.9037 31.34 7 24.8498 8.072 1.6584 50.88 8 195.3643 2.647 9∞ (D9) (S aperture) 10 -123.7398 2.263 1.8590 22.73 11 -60.4222 1.000 1.5225 59.84 12 34.0422 (D12) 13 35.0724 8.638 1.6584 50.88 14 -72.0999 0.816 15 -53.1994 6.085 2.0033 28.27 16 -57.0661 (D16) 17 200.0000 4.047 1.5503 75.50 18 -70.0000 1.000 1.7888 28.43 19 88.7178 (D19) 20 146.9186 1.000 1.7847 26.29 21 35.2338 8.408 2.0010 29.14 22 -294.1634 5.492 23 -25.4180 1.000 1.6889 31.07 24 -199.9991 9.000 25 ∞ 1.600 1.5168 63.88 26∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=68.369 β=-0.028 β=-0.148 D0 ∞ 2500.000 500.000 D9 2.021 4.185 13.522 D12 20.093 17.929 8.591 D16 1.418 1.749 4.177 D19 5.496 5.164 2.737 [Lens group data] Group starting plane focal length G1 1 75.680 G2 10 -59.462 G3 13 39.475 G4 17 -105.696 G5 20 -171.475

[0134] Fig. 10(A) is a diagram showing various aberrations when the optical system according to Example 5 is focused at infinity. Fig. 10(B) is a diagram showing various aberrations when the optical system according to Example 5 is focused at close distances. From the diagrams of various aberrations, it can be seen that the optical system according to Example 5 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close distances.

[0135] (Sixth Example) Example 6 will be described with reference to FIGS. 11 and 12 and Table 6. FIG. 11 illustrates the lens configuration of an optical system according to Example 6. The optical system OL(6) according to Example 6 includes, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I.

[0136] An aperture diaphragm S is disposed between the first lens group G1 and the second lens group G2. During focusing, the position of the aperture diaphragm S is fixed relative to the image plane I. In this embodiment, the first lens group G1 constitutes the front group GA, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0137] 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 positive meniscus lens L12 with a convex surface facing the object side, a cemented lens formed by cementing a positive meniscus lens L13 with a convex surface facing the object side and a negative meniscus lens L14 with a convex surface facing the object side, a negative meniscus lens L15 with a convex surface facing the object side, and a positive meniscus lens L16 with a convex surface facing the object side. The second lens group G2 is composed of, in order from the object side, a cemented lens having negative refractive power formed by cementing a negative meniscus lens L21 with a convex surface facing the object side and a negative meniscus lens L22 with a convex surface facing the object side.

[0138] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a biconcave negative lens L31 and a biconvex positive lens L32, a positive meniscus lens L33 with its convex surface facing the object side, and a biconvex positive lens L34. The fourth lens group G4 is composed of a negative meniscus lens L41 with its convex surface facing the object side.

[0139] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a biconvex positive lens L51 and a negative meniscus lens L52 with its concave surface facing the object side, and a negative meniscus lens L53 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.

[0140] Table 6 below lists the values ​​of the specifications of the optical system according to the sixth example.

[0141] (Table 6) [Overall specifications] f=79.983 fA=80.002 FNO=1.650 fB=58.141 2ω=14.994 βF1=3.011 Y=21.600 βF2=1.339 TL=127.000 MF1=8.575 Bf=1.000 MF2=3.511 TL(a)=126.455 Bf(a)=12.166 [Lens specifications] Surface number RD nd νd 1 110.5878 4.985 1.9630 24.11 2 283.6905 0.100 3 63.6059 4.396 2.0033 28.27 4 89.9017 3.000 5 80.0000 5.550 1.6935 53.20 6 383.6873 1.200 1.8929 20.36 7 84.9195 5.586 8 48.6443 1.000 1.8467 23.78 9 28.2642 0.248 10 28.4061 10.976 1.4970 81.61 11 231.2679 2.922 12∞ (D12) (Aperture S) 13 267.2771 1.500 1.6230 58.16 14 36.6616 3.000 1.8590 22.73 15 35.7069 (D15) 16 -36.0649 1.000 1.7380 32.33 17 92.6451 8.190 1.7725 49.62 18 -48.8133 0.100 19 64.0592 4.832 1.7725 49.60 20 306.9860 1.122 21 88.0545 5.785 1.9229 20.88 22 -184.9624 (D22) 23 140.5931 1.505 1.6910 54.82 24 48.6168 (D24) 25 83.3736 11.265 1.8515 40.78 26 -30.3564 1.000 1.8081 22.74 27 -217.6682 3.835 28 -42.0504 1.000 1.7783 23.91 29 -2185.7734 10.111 30 ∞ 1.600 1.5168 63.88 31∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=79.983 β=-0.032 β=-0.113 D0 ∞ 2544.448 725.082 D12 1.300 3.613 9.875 D15 18.706 16.393 10.131 D22 1.300 2.156 4.812 D24 8.887 8.031 5.375 [Lens group data] Group starting plane focal length G1 1 80.002 G2 13 -67.065 G3 16 41.282 G4 23 -108.270 G5 25 -1174.941

[0142] Fig. 12(A) is a diagram showing various aberrations when the optical system according to Example 6 is focused at infinity. Fig. 12(B) is a diagram showing various aberrations when the optical system according to Example 6 is focused at close distances. From the diagrams showing various aberrations, it can be seen that the optical system according to Example 6 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close distances.

[0143] (Seventh Example) Example 7 will be described with reference to FIGS. 13 and 14 and Table 7. FIG. 13 illustrates the lens configuration of an optical system according to Example 7. The optical system OL(7) according to Example 7 includes, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I.

[0144] An aperture diaphragm S is disposed between the first lens group G1 and the second lens group G2. During focusing, the position of the aperture diaphragm S is fixed relative to the image plane I. In this embodiment, the first lens group G1 constitutes the front group GA, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0145] 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 formed by cementing a biconvex positive lens L12 and a biconcave negative lens L13, and a cemented lens formed by cementing a negative meniscus lens L14 with a convex surface facing the object side and a positive meniscus lens L15 with a convex surface facing the object side. The second lens group G2 is composed of, in order from the object side, a cemented lens having negative refractive power formed by cementing a positive meniscus lens L21 with a concave surface facing the object side and a biconcave negative lens L22.

[0146] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing a biconvex positive lens L31 and a negative meniscus lens with a concave surface facing the object side, and 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. The fourth lens group G4 is composed of, in order from the object side, a cemented lens having negative refractive power formed by cementing a positive meniscus lens L41 with a concave surface facing the object side and a biconcave negative lens L42.

[0147] 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 convex surface facing the object side, a biconvex positive lens L52, and a negative meniscus lens L53 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.

[0148] Table 7 below lists the values ​​of the specifications of the optical system according to the seventh example.

[0149] (Table 7) [Overall specifications] f=72.206 fA=76.209 FNO=1.851 fB=52.016 2ω=33.081 βF1=9.569 Y=21.600 βF2=1.349 TL=119.717 MF1=8.426 Bf=1.013 MF2=2.437 TL(a)=119.172 Bf(a)=11.068 [Lens specifications] Surface number RD nd νd 1 78.4114 3.340 1.9229 18.90 2 134.9023 9.699 3 80.8692 5.255 1.7495 35.28 4 -196.7196 1.000 1.9229 18.90 5 105.8491 3.200 6 41.3126 1.000 1.9037 31.34 7 23.7147 8.842 1.6584 50.88 8 229.9800 3.085 9∞ (D9) (S aperture) 10 -153.1268 2.349 1.8590 22.73 11 -69.0439 1.000 1.5530 55.07 12 34.7326 (D12) 13 39.6101 10.055 1.7015 41.24 14 -38.2042 1.520 1.7440 44.79 15 -9186.4681 0.102 16 185.8765 2.043 2.0033 28.27 17 66.3539 5.789 1.7639 48.49 18 -68.6833 (D18) 19 -7187.8804 5.000 1.5378 74.70 20 -33.8223 1.000 1.6398 34.47 21 71.5832 (D21) 22 154.3722 1.571 1.8590 22.73 23 40.6489 0.100 24 39.6478 6.587 1.9630 24.11 25 -314.8754 5.215 26 -25.8083 3.118 1.6668 33.05 27 -200.0000 9.000 28 ∞ 1.600 1.5168 63.88 29∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=72.206 β=-0.03 β=-0.13 D0 ∞ 2545.928 610.020 D9 2.182 4.156 10.608 D12 19.120 17.146 10.694 D18 1.416 1.823 3.853 D21 4.519 4.111 2.081 [Lens group data] Group starting plane focal length G1 1 76.209 G2 10 -58.166 G3 13 36.632 G4 19 -82.990 G5 22 -115.991

[0150] Fig. 14(A) is a diagram showing various aberrations when the optical system according to Example 7 is focused at infinity. Fig. 14(B) is a diagram showing various aberrations when the optical system according to Example 7 is focused at close distances. From the diagrams of various aberrations, it can be seen that the optical system according to Example 7 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close distances.

[0151] (Eighth Example) Example 8 will be described with reference to FIGS. 15 and 16 and Table 8. FIG. 15 illustrates the lens configuration of an optical system according to Example 8. The optical system OL (8) according to Example 8 includes, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I.

[0152] An aperture stop S is disposed between the second lens group G2 and the third lens group G3. During focusing, the position of the aperture stop S is fixed relative to the image plane I. In this embodiment, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0153] 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 positive meniscus lens L12 with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L13 and a biconcave negative lens L14, and a positive meniscus lens L15 with a convex surface facing the object side. The second lens group G2 is composed of a biconcave negative lens L21.

[0154] 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 biconcave negative lens L32, a biconvex positive lens L33, and a biconvex positive lens L34. The fourth lens group G4 is composed of, in order from the object side, a biconcave negative lens L41 and a positive meniscus lens L42 with its convex surface facing the object side cemented together to form a cemented lens having negative refractive power.

[0155] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L51 with its convex surface facing the object side and a negative 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.

[0156] Table 8 below lists the values ​​of the specifications of the optical system according to the eighth example.

[0157] (Table 8) [Overall specifications] f=83.973 fA=118.595 FNO=1.850 fB=65.652 2ω=28.584 βF1=29.632 Y=21.600 βF2=1.580 TL=139.993 MF1=11.005 Bf=1.000 MF2=3.781 TL(a)=139.448 Bf(a)=12.248 [Lens specifications] Surface number RD nd νd 1 127.9197 4.846 1.9537 32.32 2 272.7568 4.078 3 115.2661 4.962 1.5928 68.62 4 277.0000 0.100 5 87.1825 13.346 1.5503 75.49 6 -77.2302 1.000 1.8548 24.80 7 128.2191 0.100 8 93.8240 4.157 1.9004 37.37 9 198.1148 (D9) 10 -653.6377 1.000 1.5530 55.07 11 56.1988 (D11) 12 ∞ 0.970 (Aperture S) 13 106.6668 5.649 1.8590 22.73 14 -97.6967 12.597 15 -61.1900 1.000 1.7618 26.52 16 57.3394 2.510 17 213.2733 4.668 1.8515 40.78 18 -86.4919 0.100 19 53.1152 18.000 1.8160 46.62 20 -78.0941 (D20) 21 -2564.6832 1.000 1.9037 31.27 22 34.4236 4.052 1.5378 74.70 23 60.4235 (D23) 24 102.4782 4.312 1.9004 37.37 25 443.2418 4.671 26 -42.4531 1.000 1.8502 30.05 27 -131.6310 10.194 28 ∞ 1.600 1.5168 63.88 29∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=83.973 β=-0.04 β=-0.12 D0 ∞ 2002.405 704.409 D9 3.130 6.630 14.135 D11 20.860 17.360 9.855 D20 2.168 3.388 5.950 D23 6.923 5.704 3.142 [Lens group data] Group starting plane focal length G1 1 118.595 G2 10 -93.536 G3 13 39.296 G4 21 -49.646 G5 24 -165.859

[0158] Fig. 16(A) is a diagram showing various aberrations when the optical system according to Example 8 is focused at infinity. Fig. 16(B) is a diagram showing various aberrations when the optical system according to Example 8 is focused at close range. From the diagrams showing various aberrations, it can be seen that the optical system according to Example 8 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close range.

[0159] (Ninth Example) The ninth example will be described with reference to FIGS. 17 to 18 and Table 9. FIG. 17 illustrates the lens configuration of the optical system according to the ninth example. The optical system OL(9) according to the ninth example is composed of, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side along different trajectories (movement amounts), changing the spacing between adjacent lens groups. During focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed relative to the image plane I.

[0160] An aperture stop S is disposed between the second lens group G2 and the third lens group G3. During focusing, the position of the aperture stop S is fixed relative to the image plane I. In this embodiment, the first lens group G1 corresponds to the leading lens group GA1, the second lens group G2 corresponds to the first focusing lens group GF1, the third lens group G3 corresponds to the positive lens group GP, the fourth lens group G4 corresponds to the second focusing lens group GF2, and the fifth lens group G5 corresponds to the final lens group GE.

[0161] The first lens group G1 is composed of, arranged along the optical axis from the object side, a biconvex positive lens L11, a cemented lens formed by cementing a biconvex positive lens L12 and a biconcave negative lens L13, and a positive meniscus lens L14 with its convex surface facing the object side. The second lens group G2 is composed of, arranged along the optical axis from the object side, a cemented lens having negative refractive power formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22.

[0162] 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 biconcave negative lens L32 and a biconvex positive lens L33, and a biconvex positive lens L34. The fourth lens group G4 is composed of, in order from the object side, a cemented lens having negative refractive power formed by cementing a negative meniscus lens L41 with its convex surface facing the object side and a positive meniscus lens L42 with its convex surface facing the object side.

[0163] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a biconvex positive lens L51 and a negative meniscus lens L52 with its concave surface facing the object side, and a negative meniscus lens L53 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.

[0164] Table 9 below lists the values ​​of the specifications of the optical system according to the ninth example.

[0165] (Table 9) [Overall specifications] f=80.000 fA=101.228 FNO=1.235 fB=59.749 2ω=30.268 βF1=8.461 Y=21.600 βF2=1.250 TL=145.575 MF1=11.429 Bf=1.000 MF2=5.187 TL(a)=145.030 Bf(a)=11.275 [Lens specifications] Surface number RD nd νd 1 183.4514 8.187 1.8830 40.77 2 -3312.8103 0.100 3 77.4634 19.962 1.4978 82.57 4 -137.5613 1.200 2.0033 28.27 5 241.0867 0.100 6 81.1912 6.450 1.7292 54.67 7 235.4529 (D7) 8 442.7861 7.699 1.6638 27.35 9 -88.8277 1.200 1.6935 53.20 10 49.5806 (D10) 11 ∞ 7.563 (Aperture S) 12 142.8934 7.834 1.7639 48.49 13 -65.8512 0.677 14 -58.4504 1.200 1.6989 30.13 15 43.1953 8.580 1.8160 46.62 16 -30004.8580 0.400 17 66.5871 6.934 1.8919 37.13 18 -265.8061 (D18) 19 98.5961 1.200 1.6889 31.07 20 38.2743 2.661 1.9861 16.48 21 43.0852 (D21) 22 140.5125 8.022 1.7639 48.49 23 -40.8933 1.200 1.7205 34.71 24 -1018.3630 5.378 25 -36.5515 1.200 1.6989 30.13 26 -200.0000 9.220 27 ∞ 1.600 1.5168 63.88 28∞Bf [Variable Interval Data] Focused at infinity Focused at mid-range distance Focused at close range f=80.000 β=-0.03 β=-0.11 D0 ∞ 2607.240 732.487 D7 3.170 5.986 14.599 D10 18.577 15.761 7.148 D18 2.100 3.486 7.287 D21 12.160 10.774 6.973 [Lens group data] Group starting plane focal length G1 1 101.228 G2 8 -78.670 G3 12 43.569 G4 19 -131.418 G5 22 -135.408

[0166] Fig. 18(A) is a diagram showing various aberrations when the optical system according to Example 9 is focused at infinity. Fig. 18(B) is a diagram showing various aberrations when the optical system according to Example 9 is focused at close range. From the diagrams showing various aberrations, it can be seen that the optical system according to Example 9 has excellent imaging performance, with various aberrations being well corrected across the entire range from focusing at infinity to focusing at close range.

[0167] (Tenth Example) Example 10 will be described with reference to FIGS. 19 to 21 and Table 10. FIG. 19 shows the lens configuration of the optical system according to Example 10. The optical system OL (10) according to Example 10 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, a seventh lens group G7 having negative refractive power, and an eighth lens group G8 having positive refractive power. When varying magnification from the wide-angle end state (W) to the telephoto end state (T), the first to eighth lens groups G1 to G8 move toward the object side along the optical axis, changing the spacing between adjacent lens groups. Furthermore, when focusing from an object at infinity to an object at a close distance, the fourth lens group G4 and the sixth lens group G6 move along the optical axis toward the image side along different trajectories (movement amounts). During focusing, the positions of the first lens group G1, the second lens group G2, the third lens group G3, the fifth lens group G5, the seventh lens group G7, and the eighth lens group G8 are fixed relative to the image plane I.

[0168] An aperture diaphragm S is disposed between the third lens group G3 and the fourth lens group G4. During magnification, the aperture diaphragm S moves along the optical axis together with the third lens group G3. During focusing, the position of the aperture diaphragm S and the third lens group G3 is fixed relative to the image plane I. In this embodiment, the first lens group G1, the second lens group G2, and the third lens group G3 constitute the front group GA, and the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 constitute the rear group GB. The first lens group G1, the second lens group G2, and the third lens group G3 correspond to the leading lens group GA1. The fourth lens group G4 corresponds to the first focusing lens group GF1, the fifth lens group G5 corresponds to the positive lens group GP, and the sixth lens group G6 corresponds to the second focusing lens group GF2. The seventh lens group G7 and the eighth lens group G8 correspond to the final lens group GE.

[0169] In this embodiment, the parameter values ​​corresponding to the aforementioned conditional expressions (1) to (20) are the parameter values ​​in the wide-angle end state. The focal length of the leading lens group GA1 is the focal length of the leading lens group GA1 in the wide-angle end state, i.e., the composite focal length of the first lens group G1, the second lens group G2, and the third lens group G3 in the wide-angle end state. The focal length of the final lens group GE is the focal length of the final lens group GE in the wide-angle end state, i.e., the composite focal length of the seventh lens group G7 and the eighth lens group G8 in the wide-angle end state.

[0170] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing a negative meniscus lens L11 with a convex surface facing the object side to a biconvex positive lens L12, and a positive meniscus lens L13 with a convex surface facing the object side. 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, and a cemented lens formed by cementing a biconcave negative lens L22 to a positive meniscus lens L23 with a convex surface facing the object side.

[0171] The third lens group G3 is composed of, arranged along the optical axis from the object side, a biconvex positive lens L31 and a positive meniscus lens L32 with its convex surface facing the object side. The fourth lens group G4 is composed of a negative meniscus lens L41 with its convex surface facing the object side.

[0172] The fifth lens group G5 is composed of, arranged along the optical axis from the object side, a cemented lens formed by cementing together a biconvex positive lens L51 and a negative meniscus lens L52 with a concave surface facing the object side, a positive meniscus lens L53 with a concave surface facing the object side, and a biconvex positive lens L54. The sixth lens group G6 is composed of, arranged along the optical axis from the object side, a positive meniscus lens L61 with a convex surface facing the object side and a negative meniscus lens L62 with a convex surface facing the object side.

[0173] The seventh lens group G7 is composed of a biconcave negative lens L71. The eighth lens group G8 is composed of a biconvex positive lens L81. An image plane I is located on the image side of the eighth lens group G8. A parallel plate PP is located between the eighth lens group G8 and the image plane I.

[0174] Table 10 below lists the values ​​of the specifications of the optical system according to the tenth example.

[0175] (Table 10) [Overall specifications] Magnification ratio=3.90 fA=62.983 fB=65.548 βF1=6.538 βF2=1.193 MF1=4.361 MF2=2.626 WMT f 50.001 105.261 194.999 FNO 4.310 4.680 5.843 2ω 32.403 14.756 8.181 Y 14.200 14.200 14.200 TL 120.000 145.076 180.000 BF 1.000 1.000 1.000 TL(a) 119.455 144.531 179.454 Bf(a) 10.934 11.154 19.512 [Lens specifications] Surface number RD nd νd 1 600.0000 1.000 1.8548 24.80 2 155.2796 5.494 1.5378 74.70 3 -103.0036 0.100 4 43.6041 3.387 1.4970 81.54 5 61.7534 (D5) 6 32.1528 1.000 1.4875 70.23 7 22.4574 7.828 8 -29.4600 1.000 1.6400 60.08 9 78.0591 2.128 1.9591 17.47 10 260.3924 (D10) 11 75.7053 3.155 1.4560 91.37 12 -80.2763 0.100 13 30.2800 3.198 1.5932 67.90 14 137.1805 1.507 15∞ (D15) (Aperture S) 16 65.2191 1.000 1.4560 91.37 17 23.9229 (D17) 18 146.4932 3.856 1.5186 69.89 19 -19.3364 1.000 2.0033 28.27 20 -51.9744 0.126 21 -50.6359 2.092 1.5378 74.70 22 -34.8114 0.100 23 137.5873 2.826 1.8160 46.59 24 -57.7362 (D24) 25 62.3570 2.187 1.8052 25.45 26 212.1498 0.100 27 109.1696 1.000 1.7570 47.86 28 27.2138 (D28) 29 -31.9103 1.000 1.6385 55.34 30 1423.4306 (D30) 31 351.5326 3.000 1.9020 25.26 32 -97.3988 (D32) 33 ∞ 1.600 1.5168 63.88 34∞Bf [Variable Interval Data] Focused at infinity Focused at mid-distance WMTWMT D5 2.136 30.400 34.714 2.136 30.400 34.714 D10 15.274 4.048 1.000 15.273 4.048 1.000 D15 1.000 6.133 12.552 2.010 6.231 12.803 D17 12.641 5.710 4.455 11.631 5.613 4.204 D24 20.316 4.001 1.500 22.316 6.206 2.979 D28 7.468 33.900 18.239 5.468 31.696 16.760 D30 1.503 1.000 39.299 1.503 1.000 39.299 D32 8.879 9.100 17.458 8.879 9.100 17.458 Close focus state WMT D5 2.136 30.400 34.714 D10 15.274 4.048 1.000 D15 5.361 7.542 14.689 D17 8.280 4.302 2.318 D24 22.943 14.670 16.356 D28 4.842 23.232 3.383 D30 1.503 1.000 39.299 D32 8.879 9.100 17.458 [Lens group data] Group starting plane focal length G1 1 121.101 G2 6 -34.997 G3 11 37.110 G4 16 -83.487 G5 18 42.783 G6 25 -90.033 G7 29 -48.865 G8 31 84.823

[0176] Fig. 20(A) is a diagram showing various aberrations when the optical system according to Example 10 is focused at infinity in the wide-angle end state. Fig. 20(B) is a diagram showing various aberrations when the optical system according to Example 10 is focused at a close distance in the wide-angle end state. Fig. 21(A) is a diagram showing various aberrations when the optical system according to Example 10 is focused at infinity in the telephoto end state. Fig. 21(B) is a diagram showing various aberrations when the optical system according to Example 10 is focused at a close distance in the telephoto end state. It can be seen from the various aberration diagrams that the optical system according to Example 10 has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing at infinity to focusing at a close distance, not only in the wide-angle end state but also in the telephoto end state.

[0177] 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 (20) for all Examples (Examples 1 to 10). Condition (1) 0.30 <STL / TL<0.90 Condition (2) 0.50 <fA / f<2.00 Condition (3) 0.50 <fA / (-fF1)<1.50 Condition (4) 0.35 <fB / (-fF1)<1.50 Conditional expression (5) -2.00<(-fE) / f<15.00 Condition (6) -1.00 <fP / (-fE)<1.50 Conditional expression (7) 1.10<(-fF1) / fP<3.20 Condition (8) 0.30 <fP / f<1.00 Condition (9) 0.10 <fF1 / fF2<2.00 Condition (10) 0.50 <f / (-fF1)<1.80 Conditional expression (11) -2.50<(rF12+rF11) / (rF12-rF11)<0.00 Condition (12) 0.05 <Bf / TL<0.80 Conditional expression (13) -0.80<(rR2+rR1) / (rR2-rR1)<2.50 Conditional expression (14) 0.01<1 / βF1<0.60 Conditional expression (15) 0.50<1 / βF2<0.95 Conditional expression (16) {βF1+(1 / βF1)} -2 <0.20 Conditional expression (17) {βF2+(1 / βF2)} -2 ≦0.25 Condition (18) 0.15 <MF1 / MF2<0.80 Conditional expression (19) 20.00°<2ω<40.00° Condition (20) 0.08 <Bf / f<1.20

[0178] [Conditional Expression Corresponding Values] (First to Fourth Examples) Conditional Expression 1st Example 2nd Example 3rd Example 4th Example (1) 0.705 0.670 0.751 0.698 (2) 1.027 0.988 1.250 1.403 (3) 1.094 1.259 0.934 1.210 (4) 0.788 1.052 0.749 0.626 (5) 7.028 0.998 1.234 2.973 (6) 0.090 0.473 0.364 0.175 (7) 1.490 1.661 2.981 2.232 (8) 0.630 0.472 0.449 0.520 (9) 0.271 0.559 1.306 0.809 (10) 1.065 1.275 0.748 0.862 (11) -1.192 -1.054 -2.198 -1.300 (12) 0.087 0.099 0.200 0.086 (13) 1.661 1.441 2.433 2.272 (14) 0.384 0.227 0.401 0.265 (15) 0.889 0.809 0.711 0.760 (16) 0.112 0.047 0.119 0.061 (17) 0.247 0.239 0.223 0.232 (18) 0.648 0.623 0.355 0.426 (19) 28.285 28.002 28.996 28.631 (20) 0.128 0.132 0.218 0.132 [Conditional Expression Corresponding Values] (Fifth to Eighth Examples) Conditional Expression 5th Example 6th Example 7th Example 8th Example (1) 0.696 0.688 0.707 0.591 (2) 1.107 1.000 1.055 1.412 (3) 1.273 1.193 1.310 1.268 (4) 0.886 0.867 0.894 0.702 (5) 2.508 14.690 1.606 1.975 (6) 0.230 0.035 0.316 0.237 (7) 1.506 1.625 1.588 2.380 (8) 0.577 0.516 0.507 0.468 (9) 0.563 0.619 0.701 1.884 (10) 1.150 1.193 1.241 0.898 (11) -0.568 -1.308 -0.630 -0.842 (12) 0.096 0.096 0.093 0.088 (13) 1.291 1.039 1.296 1.952 (14) 0.148 0.332 0.104 0.034 (15) 0.775 0.747 0.741 0.633 (16) 0.021 0.089 0.011 0.001 (17) 0.234 0.230 0.229 0.204 (18) 0.240 0.409 0.289 0.344 (19) 35.107 29.992 33.081 28.584 (20) 0.162 0.152 0.153 0.146 [Conditional Expression Corresponding Values] (Examples 9 to 10) Conditional Expression 9th Example 10th Example (1) 0.544 0.609 (2) 1.265 1.260 (3) 1.287 0.754 (4) 0.759 0.785 (5) 1.693 -1.696 (6) 0.322 -0.504 (7) 1.806 1.951 (8) 0.545 0.856 (9) 0.599 0.927 (10) 1.017 2.236 (telephoto end), 0.599 (wide-angle end) (11) -1.252 -2.159 (12) 0.078 0.092 (13) 1.447 -0.566 (14) 0.118 0.153 (15) 0.800 0.838 (16) 0.014 0.022 (17) 0.238 0.242 (18) 0.454 0.602 (19) 30.268 32.403 (20) 0.141 0.219

[0179] According to each of the above embodiments, an optical system with little aberration fluctuation during focusing can be realized.

[0180] The above-described examples are merely illustrative examples of the present invention, and the present invention is not limited to these.

[0181] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the optical system of this embodiment.

[0182] Although five-group and eight-group configurations have been shown as examples of the optical system of this embodiment, the present application is not limited to these, and optical systems with other group configurations (e.g., six-group, nine-group, etc.) can also be configured. Specifically, a lens or lens group may be added to the optical system of this embodiment closest to the object or closest to the image plane. Note that a lens group refers to a portion having at least one lens separated by an air gap that changes during focusing or zooming.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] It is preferable that the aperture diaphragm be located between the first and second lens groups, or between the second and third lens groups, or between the third and fourth lens groups, but it is also possible to use the lens frame to fulfill that role without providing a component serving as an aperture diaphragm.

[0187] 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]

[0188] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group G7 7th lens group G8 8th lens group I Image plane S Aperture stop

Claims

1. It consists of a front group, a stop, and a rear group, arranged in order from the object side along the optical axis. the front group is a leading lens group that is made up of one lens group having positive refractive power, the rear group is composed of, arranged in order from the object side of the rear group, a first focusing lens group having negative refractive power, a positive lens group having positive refractive power, a second focusing lens group having negative refractive power, and a final lens group having negative refractive power; When focusing from an object at infinity to an object at a close distance, the first focusing lens group and the second focusing lens group move along different loci toward the image plane along the optical axis, An optical system in which the first focusing lens group and the second focusing lens group each include one or two lenses, and the following condition is satisfied: 0.862≦f / (-fF1)<1.80 where f is the focal length of the optical system. fF1: focal length of the first focusing lens group

2. 2. The optical system according to claim 1, wherein the following condition is satisfied: 0.30<STL / TL<0.90 where STL is the distance on the optical axis from the stop to the image plane. TL: total length of the optical system

3. 3. The optical system according to claim 1, wherein the position of said positive lens group is fixed relative to the image plane during focusing from an object at infinity to an object at a close distance.

4. 4. The optical system according to claim 1, wherein the following condition is satisfied: 0.35<fB / (-fF1)<1.50 where fB is the composite focal length of the positive lens group, the second focusing lens group, and the final lens group. fF1: focal length of the first focusing lens group

5. The optical system comprises, arranged in order from the object side along the optical axis, a leading lens group having positive refractive power, a first focusing lens group having negative refractive power, a positive lens group having positive refractive power, a second focusing lens group having negative refractive power, and a final lens group, When focusing from an object at infinity to an object at a close distance, the first focusing lens group and the second focusing lens group move along different loci toward the image plane along the optical axis, An optical system in which the first focusing lens group and the second focusing lens group each include one or two lenses, and the following condition is satisfied: 0.862≦f / (-fF1)<1.80 0.35<fB / (-fF1)≦0.867 -2.00<(-fE) / f<15.00 where f is the focal length of the optical system. fF1: focal length of the first focusing lens group fB: composite focal length of the positive lens group, the second focusing lens group, and the final lens group fF1: focal length of the first focusing lens group fE: focal length of the final lens group

6. The optical system comprises, arranged in order from the object side along the optical axis, a leading lens group having positive refractive power, a first focusing lens group having negative refractive power, a positive lens group having positive refractive power, a second focusing lens group having negative refractive power, and a final lens group, When focusing from an object at infinity to an object at a close distance, the first focusing lens group and the second focusing lens group move along different loci toward the image plane along the optical axis, each of the first focusing lens group and the second focusing lens group is composed of one or two lenses; The positive lens group has, arranged in order from the object side along the optical axis, a negative lens, a first positive lens, and a second positive lens, and the optical system satisfies the following conditional expression: 0.862≦f / (-fF1)<1.80 0.35<fB / (-fF1)≦0.867 where f is the focal length of the optical system fF1: focal length of the first focusing lens group fB: composite focal length of the positive lens group, the second focusing lens group, and the final lens group

7. 7. The optical system according to claim 5, wherein a diaphragm is disposed between the leading lens group and the first focusing lens group.

8. 8. The optical system according to claim 7, which satisfies the following condition: 0.30<STL / TL<0.90 where STL is the distance on the optical axis from the stop to the image plane. TL: total length of the optical system

9. 9. The optical system according to claim 1, wherein the following condition is satisfied: 0.50<fA / f<2.00 where fA is the focal length of the preceding lens group f: focal length of the optical system

10. 10. The optical system according to claim 1, wherein the following condition is satisfied: 0.50<fA / (-fF1)<1.50 where fA is the focal length of the preceding lens group fF1: focal length of the first focusing lens group

11. The optical system according to any one of claims 1 to 4 and 6 to 10, which satisfies the following conditional expressions: -2.00<(-fE) / f<15.00 where fE is the focal length of the final lens group f: focal length of the optical system

12. 12. The optical system according to claim 1, wherein the following condition is satisfied: -1.00<fP / (-fE)<1.50 where fP is the focal length of the positive lens group fE: focal length of the final lens group

13. The optical system according to any one of claims 1 to 12, which satisfies the following conditional expression: 1.10<(-fF1) / fP<3.20 where fF1 is the focal length of the first focusing lens group fP: focal length of the positive lens group

14. The optical system according to any one of claims 1 to 13, which satisfies the following conditional expression: 0.30<fP / f<1.00 where fP is the focal length of the positive lens group f: focal length of the optical system

15. 15. The optical system according to claim 1, wherein the positive lens group has, arranged in order from the object side along the optical axis, a negative lens, a first positive lens, and a second positive lens.

16. The optical system according to any one of claims 1 to 5 and 7 to 15, which satisfies the following conditional expression: 0.10<fF1 / fF2<2.00 where fF1 is the focal length of the first focusing lens group fF2: focal length of the second focusing lens group

17. 17. The optical system according to claim 1, wherein the first focusing lens group is made up of one negative lens component.

18. 18. The optical system according to claim 1, wherein the following condition is satisfied: -2.50<(rF12+rF11) / (rF12-rF11)<0.00 where rF11 is the radius of curvature of the lens surface closest to the object in the first focusing lens group. rF12: radius of curvature of the lens surface in the first focusing lens group closest to the image plane

19. 19. The optical system according to claim 1, wherein the second focusing lens group is made up of one negative lens component.

20. 20. The optical system according to claim 1, wherein the following condition is satisfied: 0.05<Bf / TL<0.80 where Bf is the back focus of the optical system. TL: total length of the optical system

21. 21. The optical system according to claim 1, wherein the following condition is satisfied: -0.80<(rR2+rR1) / (rR2-rR1)<2.50 where rR1 is the radius of curvature of the object-side lens surface of the lens arranged closest to the image plane in the optical system. rR2: the radius of curvature of the lens surface on the image side of the lens arranged closest to the image side of the optical system

22. 22. The optical system according to claim 1, wherein the following condition is satisfied: 0.01<1 / βF1<0.60 where βF1 is the lateral magnification of the first focusing lens group when focusing on an object at infinity.

23. The optical system according to any one of claims 1 to 22, which satisfies the following conditional expression: 0.50<1 / βF2<0.95 where βF2 is the lateral magnification of the second focusing lens group when focusing on an object at infinity.

24. The optical system according to any one of claims 1 to 23, which satisfies the following conditional expression: {βF1+(1 / βF1)} -2 <0.20 where βF1 is the lateral magnification of the first focusing lens group when focusing on an object at infinity.

25. The optical system according to any one of claims 1 to 24, which satisfies the following conditional expression: {βF2+(1 / βF2)} -2 ≦0.25 where βF2 is the lateral magnification of the second focusing lens group when focusing on an object at infinity.

26. The optical system according to any one of claims 1 to 25, which satisfies the following conditional expression: 0.15<MF1 / MF2<0.80 where MF1 is the absolute value of the movement amount of the first focusing lens group when focusing from an object at infinity to an object at a close distance. MF2: Absolute value of the movement amount of the second focusing lens group when focusing from an object at infinity to an object at a close distance

27. The optical system according to any one of claims 1 to 26, which satisfies the following conditional expression: 20.00°<2ω<40.00° where 2ω is the total angle of view of the optical system.

28. 28. The optical system according to claim 1, wherein the following condition is satisfied: 0.08<Bf / f<1.20 where Bf is the back focus of the optical system. f: focal length of the optical system

29. An optical instrument comprising the optical system according to any one of claims 1 to 28.

Images