Optical systems and optical instruments

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 device.

Background Art

[0002] Conventionally, an optical system has been proposed in which a plurality of lens groups are moved along the optical axis to perform focusing (see, for example, Patent Document 1). In such an optical system, the focusing lens group becomes heavier, and it is difficult to suppress aberration fluctuations during focusing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The optical system according to the first aspect of the present invention includes a front group, an aperture, and a rear group arranged in order from the object side along the optical axis. The front group consists of a leading lens group composed of one lens group having a positive refractive power. The rear group is composed of a first focusing lens group having a negative refractive power arranged in order from the most object side of the rear group, a positive lens group having a positive refractive power, a second focusing lens group having a negative refractive power, and a final lens group having a negative refractive power. When focusing from an infinite object to a near object, the first focusing lens group and the second focusing lens group move along the optical axis toward the image plane side on different trajectories. The first focusing lens group and the second focusing lens group are each composed of one or two lenses and satisfy the following conditional expression. 0.838≦f / (-fF1)<1.80 Here, f: focal length of the optical system fF1: focal length of the first focusing lens group

[0005] The second optical system according to the present invention consists of 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, all arranged in order from the object side along the optical axis. 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 toward the image plane along the optical axis along different trajectories, and both the first focusing lens group and the second focusing lens group consist of one or two lenses, satisfying the following conditional equation. 0.838 ≤ f / (-fF1) < 1.80 0.35 <fB / (-fF1)≦0.867 However, f: focal length of the optical system fF1: Focal length of the first focusing lens group fB: Combined focal length of the lens group positioned on the image plane side of the first focusing lens group. fF1: Focal length of the first focusing lens group

[0006] The optical instrument according to the present invention is configured to include the optical system described above. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows the lens configuration of the optical system according to the first embodiment. [Figure 2] Figures 2(A) and 2(B) show the aberrations of the optical system according to the first embodiment when it is focused at infinity and when it is focused at close range, respectively. [Figure 3] This figure shows the lens configuration of the optical system according to the second embodiment. [Figure 4] Figures 4(A) and 4(B) show the aberrations of the optical system according to the second embodiment when it is focused at infinity and when it is focused at close range, respectively. [Figure 5] This figure shows the lens configuration of the optical system according to the third embodiment. [Figure 6] Figures 6(A) and 6(B) show the aberrations of the optical system according to the third embodiment when it is focused at infinity and when it is focused at close range, respectively. [Figure 7]This figure shows the lens configuration of the optical system according to the fourth embodiment. [Figure 8] Figures 8(A) and 8(B) show the aberrations of the optical system according to the fourth embodiment when it is focused at infinity and when it is focused at close range, respectively. [Figure 9] This figure shows the lens configuration of the optical system according to the fifth embodiment. [Figure 10] Figures 10(A) and 10(B) show the aberrations of the optical system according to the fifth embodiment when it is focused at infinity and when it is focused at close range, respectively. [Figure 11] This figure shows the lens configuration of the optical system according to the sixth embodiment. [Figure 12] Figures 12(A) and 12(B) show the aberrations of the optical system according to the sixth embodiment when it is focused at infinity and when it is focused at close range, respectively. [Figure 13] This figure shows the lens configuration of the optical system according to the seventh embodiment. [Figure 14] Figures 14(A) and 14(B) show the aberrations of the optical system according to the seventh embodiment when it is focused at infinity and when it is focused at close range, respectively. [Figure 15] This figure shows the lens configuration of the optical system according to the eighth embodiment. [Figure 16] Figures 16(A) and 16(B) show the aberrations of the optical system according to the eighth embodiment when focused at infinity and when focused at close range, respectively. [Figure 17] This figure shows the lens configuration of the optical system according to the ninth embodiment. [Figure 18] Figures 18(A) and 18(B) show the aberrations of the optical system according to the ninth embodiment when it is focused at infinity and when it is focused at close range, respectively. [Figure 19] This figure shows the lens configuration of the optical system according to the 10th embodiment. [Figure 20] Figures 20(A) and 20(B) show the aberrations of the optical system according to the 10th embodiment at the wide-angle end when focused at infinity and when focused at close range, respectively. [Figure 21] Figures 21(A) and 21(B) show the various aberrations of the optical system according to the 10th embodiment at the telephoto end when focused at infinity and when focused at close range, respectively. [Figure 22] It is a diagram showing the configuration of a camera equipped with an optical system according to each embodiment. [Figure 23] It is a flowchart showing a method for manufacturing an optical system according to the first embodiment. [Figure 24] It is a flowchart showing a method for manufacturing an optical system according to the second embodiment.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, preferred embodiments according to the present invention will be described. First, a camera (optical device) equipped with an optical system according to each embodiment will be described based on FIG. 22. As shown in FIG. 22, this camera 1 is composed of a main body 2 and a photographing lens 3 attached to the main body 2. The main body 2 includes an imaging element 4, a main body control unit (not shown) that controls the operation of the digital camera, and a liquid crystal screen 5. The photographing lens 3 includes an optical system OL composed of a plurality of lens groups and a lens position control mechanism (not shown) that controls the positions of the respective lens groups. The lens position control mechanism is composed of a sensor that detects the position of the lens group, a motor that moves the lens group back and forth along the optical axis, a control circuit that drives the motor, and the like.

[0009] Light from the subject is condensed by the optical system OL of the photographing lens 3 and reaches the image plane I of the imaging element 4. The light from the subject that has reached the image plane I is photoelectrically converted by the imaging element 4 and recorded in a memory (not shown) as digital image data. The digital image data recorded in the memory can be displayed on the liquid crystal screen 5 in response to a user's operation. Note that this camera may be a mirrorless camera or a single-lens reflex type camera having a quick return mirror. Also, the optical system OL shown in FIG. 22 schematically shows the 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 the first embodiment will be described. Optical system OL(1), an example of the optical system OL according to the first embodiment, consists of a front group GA, an aperture (diaphragm) S, and a rear group GB, arranged in order from the object side along the optical axis, as shown in Figure 1. The rear group GB has a first focusing lens group GF1 having negative refractive power and positioned closest to the object, and a second focusing lens group GF2 having negative refractive power and positioned closer to the image plane than the first focusing lens group GF1. When focusing from an object at infinity to a nearby object, the first focusing lens group GF1 and the second focusing lens group GF2 move toward the image plane along the optical axis along different trajectories.

[0011] According to the first embodiment, it becomes possible to obtain an optical system with minimal aberration variation during focusing, and an optical instrument equipped with this optical system. Furthermore, because the aberration variation during focusing is minimal, good optical performance can be achieved even with a large aperture. Since each focusing lens group can be made lighter, an optical system compatible with high-speed autofocus (AF) can be obtained. Since the drive mechanism of each focusing lens group can be simplified, the sensitivity of optical performance to manufacturing errors can be reduced.

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

[0013] The optical system OL according to the first embodiment preferably satisfies the following condition (1). 0.30 <STL / TL<0.90 ···(1) However, STL: distance along the optical axis from aperture S to image plane I. TL: Total length of optical system OL

[0014] Conditional equation (1) defines an appropriate relationship between the distance along the optical axis from the aperture S to the image plane I and the total length of the optical system OL. By satisfying conditional equation (1), the exit pupil position can be estimated, and an appropriate range of aperture positions can be defined. Furthermore, it is possible to suppress the angle of view fluctuations corresponding to changes in back focus due to manufacturing errors, etc. In each embodiment, the total length of the optical system OL is the distance along the optical axis from the lens surface closest to the object to the image plane I when the optical system OL is in focus at infinity (air equivalent distance).

[0015] When the corresponding value in conditional equation (1) falls below the lower limit, the exit pupil becomes closer to the image plane I, resulting in a steeper inclination angle of the light rays incident on the image plane I. This makes it easier for the field of view to fluctuate due to changes in back focus caused by manufacturing errors, etc. By setting the lower limit of conditional equation (1) to 0.33, 0.35, 0.38, 0.40, 0.43, 0.45, 0.48, 0.50, and further to 0.52, the effects of this embodiment can be made more reliable.

[0016] If the corresponding value in conditional equation (1) exceeds the upper limit, the position of the aperture S is inappropriate, resulting in an imbalance in the ratio of upper and lower light cut-off at aperture S, which is known as a single aperture. Furthermore, the overall length of the optical system OL is too short, making aberration correction difficult. By setting the upper limit of conditional equation (1) to 0.88, 0.85, 0.83, 0.80, 0.78, and further to 0.76, the effect of this embodiment can be made more reliable.

[0017] In the optical system OL according to the first embodiment, the rear lens group GB includes a positive lens group GP having positive refractive power, positioned between the first focusing lens group GF1 and the second focusing lens group GF2. When focusing from an object at infinity to an object at a close distance, it is desirable that the position of the positive lens group GP is fixed with respect to the image plane I. This allows for good correction of spherical aberration, Petzval sum, etc.

[0018] In the optical system OL according to the first embodiment, the front group GA preferably consists of a leading lens group GA1 having positive refractive power, and the rear group GB preferably has a positive lens group GP having positive refractive power positioned between the first focusing lens group GF1 and the second focusing lens group GF2, and a final lens group GE positioned closer to the image plane than the second focusing lens group GF2. By positioning multiple focusing lens groups closer to the image plane than the aperture S, it is possible to align the axes of the multiple focusing lens groups during focusing, thereby reducing the sensitivity of optical performance to manufacturing errors. Furthermore, by moving multiple focusing lens groups during focusing, the weight of the focusing lens groups can be reduced, and aberration fluctuations during focusing can be effectively suppressed.

[0019] Next, an optical system according to the second embodiment will be described. Optical system OL(1), as an example of the optical system OL according to the second embodiment, is configured as shown in Figure 1 with 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, all arranged in order from the object side along the optical axis. When 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 along the optical axis along different trajectories.

[0020] According to the second embodiment, it becomes possible to obtain an optical system with minimal aberration variation during focusing, and an optical instrument equipped with this optical system. Furthermore, because the aberration variation during focusing is minimal, good optical performance can be achieved even with a large aperture. Since each focusing lens group can be made lighter, an optical system compatible with high-speed autofocus (AF) can be obtained. Since the drive mechanism of each focusing lens group can be simplified, the sensitivity of optical performance to manufacturing errors can be reduced.

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

[0022] In the optical system OL according to the second embodiment, it is desirable to place an aperture (aperture diaphragm) S between the leading lens group GA1 and the first focusing lens group GF1. This allows for effective stopping of the light rays incident on the focusing lens group, making it possible to make the focusing lens group smaller and lighter. Furthermore, it makes it easier to align the axes of multiple focusing lens groups during centering, reducing the sensitivity of optical performance to manufacturing errors. In addition, it allows for good correction of angle of view fluctuations during focusing.

[0023] The optical system OL according to the second embodiment preferably satisfies the aforementioned conditional equation (1). By satisfying conditional equation (1), the exit pupil position can be estimated, as in the first embodiment, and a range of appropriate aperture positions can be defined. Furthermore, fluctuations in the field of view corresponding to changes in back focus due to manufacturing errors, etc., can be suppressed. The effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (1) to 0.33, 0.35, 0.38, 0.40, 0.43, 0.45, 0.48, 0.50, and further to 0.52. The effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (1) to 0.88, 0.85, 0.83, 0.80, 0.78, and further to 0.76.

[0024] The optical system OL according to the first and second embodiments preferably satisfies the following condition (2). 0.50 <fA / f<2.00 ···(2) However, fA: Focal length of the leading lens group GA1 f: focal length of optical system OL

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

[0026] If the corresponding value in conditional equation (2) falls outside the above range, it becomes difficult to correct chromatic aberration and also difficult to shorten the overall length of the optical system OL. Setting the lower limit of conditional equation (2) to 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, and further to 0.95 makes the effects of each embodiment more reliable. Furthermore, setting the upper limit of conditional equation (2) to 1.90, 1.80, 1.75, 1.70, 1.65, 1.60, 1.55, 1.50, and further to 1.45 makes the effects of each embodiment more reliable.

[0027] The optical system OL according to the first and second embodiments preferably satisfies the following condition (3). 0.50 <fA / (-fF1)<1.50 ···(3) However, fA: Focal length of the leading lens group GA1 fF1: Focal length of the first focusing lens group GF1

[0028] Condition (3) defines the 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 condition (3), aberration and angle of view fluctuations during focusing can be reduced.

[0029] If the corresponding value in conditional equation (3) falls outside the above range, it becomes difficult to suppress aberration and field of view fluctuations during focusing. Setting the lower limit of conditional equation (3) to 0.53, 0.55, 0.58, 0.60, 0.63, 0.65, 0.58, 0.70, and further to 0.73 makes the effects of each embodiment more reliable. Furthermore, setting the upper limit of conditional equation (3) to 1.48, 1.45, 1.43, 1.40, 1.38, 1.35, and further to 1.33 makes the effects of each embodiment more reliable.

[0030] The optical system OL according to the first and second embodiments preferably satisfies the following condition (4). 0.35 <fB / (-fF1)<1.50 ···(4) However, fB: The combined focal length of the lens groups positioned closer to the image plane than the first focusing lens group GF1. fF1: Focal length of the first focusing lens group GF1

[0031] Conditional equation (4) defines an appropriate relationship between the combined focal length of the lens groups positioned on the image plane side of the first focusing lens group GF1 and the focal length of the first focusing lens group GF1. By satisfying conditional equation (4), aberration fluctuations and angle of view fluctuations during focusing can be reduced.

[0032] If the corresponding value in conditional equation (4) falls outside the above range, it becomes difficult to suppress aberration and field of view fluctuations during focusing. Setting the lower limit of conditional equation (4) to 0.38, 0.40, 0.43, 0.45, 0.48, 0.50, 0.53, 0.55, 0.58, and further to 0.60 makes the effects of each embodiment more reliable. Furthermore, setting the upper limit of conditional equation (4) to 1.45, 1.40, 1.35, 1.30, 1.25, 1.20, 1.18, 1.20, 1.15, 1.13, and further to 1.10 makes the effects of each embodiment more reliable.

[0033] The optical system OL according to the first and second embodiments preferably satisfies the following condition (5). -2.00 < (-fE) / f < 15.00 ···(5) However, fE: focal length of the final lens group GE f: focal length of optical system OL

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

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

[0036] The optical system OL according to the first and second embodiments preferably satisfies the following condition (6). -1.00 <fP / (-fE)<1.50 ···(6) However, fP: focal length of the positive lens group GP fE: Focal length of the final lens group GE

[0037] Condition (6) defines the appropriate relationship between the focal length of the positive lens group GP and the focal length of the final lens group GE. By satisfying condition (6), aberration fluctuations during focusing can be well suppressed, and the exit pupil can be moved further away from the image plane I.

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

[0039] The optical system OL according to the first and second embodiments preferably satisfies the following condition (7). 1.10 < (-fF1) / fP < 3.20 ... (7) However, fF1: Focal length of the first focusing lens group GF1 fP: Focal length of the positive lens group GP

[0040] Conditional equation (7) defines the 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 equation (7), the occurrence of spherical aberration and axial chromatic aberration can be effectively suppressed.

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

[0042] The optical system OL according to the first and second embodiments preferably satisfies the following condition (8). 0.30 <fP / f<1.00 ···(8) However, fP: focal length of the positive lens group GP f: focal length of optical system OL

[0043] Condition (8) defines the 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 corrected effectively.

[0044] If the corresponding value in conditional equation (8) falls outside the above range, it becomes difficult to correct spherical aberration, Petzval sum, etc. Setting the lower limit of conditional equation (8) to 0.33, 0.35, 0.38, 0.40, and further to 0.43 makes the effects of each embodiment more reliable. Furthermore, setting the upper limit of conditional equation (8) to 0.98, 0.95, 0.93, 0.90, and further to 0.88 makes the effects of each embodiment more reliable.

[0045] In the optical system OL according to the first and second embodiments, it is desirable that the positive lens group GP has a negative lens, a first positive lens, and a second positive lens arranged in order from the object side along the optical axis. This makes it possible to miniaturize the optical system OL and to move the exit pupil further away from the image plane I. Furthermore, it is possible to correct various aberrations, including spherical aberration, effectively.

[0046] The optical system OL according to the first and second embodiments preferably satisfies the following condition (9). 0.10 <fF1 / fF2<2.00 ···(9) However, fF1: Focal length of the first focusing lens group GF1 fF2: Focal length of the second focusing lens group GF2

[0047] Conditional equation (9) defines the 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 equation (9), spherical aberration, field curvature, etc., can be effectively corrected.

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

[0049] The optical system OL according to the first and second embodiments preferably satisfies the following condition (10). 0.50 <f / (-fF1)<1.80 ···(10) However, f: focal length of the optical system OL fF1: Focal length of the first focusing lens group GF1

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

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

[0052] In the optical system OL according to the first and second embodiments, it is preferable that the first focusing lens group GF1 consists of a single negative lens component. This makes the first focusing lens group GF1 lighter, enabling high-speed focusing from an object at infinity to an object at a close distance. In each embodiment, the lens component refers to a single lens or a cemented lens.

[0053] The optical system OL according to the first and second embodiments preferably satisfies the following condition (11). -2.50<(rF12+rF11) / (rF12-rF11)<0.00 ···(11) However, rF11: The 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 constituting the first focusing lens group GF1. By satisfying condition (11), spherical aberration, coma aberration, etc., can be corrected effectively.

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

[0056] In the optical system OL according to the first and second embodiments, it is preferable that the second focusing lens group GF2 consists of one negative lens component. This makes the second focusing lens group GF2 lighter, enabling high-speed focusing from an object at infinity to an object at a close distance.

[0057] The optical system OL according to the first and second embodiments preferably satisfies the following condition (12). 0.05 <Bf / TL<0.80 ···(12) However, Bf: back focus of the optical system OL TL: Total length of optical system OL

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

[0059] If the corresponding value in conditional equation (12) falls below the lower limit, the exit pupil becomes too close to the image plane I, causing vignetting at the image plane I. Attempting to avoid this can result in difficulty correcting off-axial aberrations, particularly coma aberration, which is undesirable. By setting the lower limit of conditional equation (12) to 0.06, and further to 0.07, the effects of each embodiment can be made more reliable.

[0060] If the corresponding value in conditional equation (12) exceeds the upper limit, the overall length of the optical system OL becomes too short, making it difficult to correct spherical aberration, coma aberration, etc. Also, the back focus of the optical system OL becomes too long, resulting in a larger optical system OL. By setting the upper limit of conditional equation (12) to 0.75, 0.70, 0.65, 0.50, 0.40, 0.35, 0.30, and further to 0.25, the effects of each embodiment can be made more reliable.

[0061] The optical system OL according to the first and second embodiments preferably satisfies the following condition (13). -0.80<(rR2+rR1) / (rR2-rR1)<2.50 (13) However, rR1: radius of curvature of the object-side lens surface at the lens positioned closest to the image plane in the optical system OL. rR2: Radius of curvature of the image-plane lens surface at the lens positioned closest to the image plane in the optical system OL.

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

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

[0064] The optical system OL according to the first and second embodiments preferably satisfies the following condition (14). 0.01 < 1 / βF1 < 0.60 ···(14) However, βF1: Horizontal magnification of the first focusing lens group GF1 when focusing on an object at infinity.

[0065] Condition (14) specifies an appropriate range for the lateral magnification of the first focusing lens group GF1 when an object at infinity is in focus. By satisfying condition (14), various aberrations such as spherical aberration and field curvature can be effectively corrected when an object at infinity is in focus.

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

[0067] The optical system OL according to the first and second embodiments preferably satisfies the following condition (15). 0.50 < 1 / βF2 < 0.95 ···(15) However, βF2: Horizontal magnification of the second focusing lens group GF2 when focusing on an object at infinity.

[0068] Condition (15) specifies an appropriate range for the lateral magnification of the second focusing lens group GF2 when an object at infinity is in focus. By satisfying condition (15), various aberrations such as spherical aberration and field curvature can be effectively corrected when an object at infinity is in focus.

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

[0070] The optical system OL according to the first and second embodiments preferably satisfies the following condition (16). {βF1+(1 / βF1)} -2 <0.20 ···(16) However, βF1: Horizontal magnification of the first focusing lens group GF1 when focusing on an object at infinity.

[0071] Condition (16) specifies an appropriate range for the lateral magnification of the first focusing lens group GF1 when an object at infinity is in focus. By satisfying condition (16), various aberrations such as spherical aberration and field curvature can be effectively corrected when an object at infinity is in focus.

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

[0073] The optical system OL according to the first and second embodiments preferably satisfies the following condition (17). {βF2+(1 / βF2)} -2 ≤0.25 ···(17) However, βF2: Horizontal magnification of the second focusing lens group GF2 when focusing on an object at infinity.

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

[0075] The optical system OL according to the first and second embodiments preferably satisfies the following condition (18). 0.15< MF2 / MF1 <0.80 ···(18) However, MF1: The absolute value of the amount of movement of the first focusing lens group GF1 when focusing from an object at infinity to an object at a close distance. MF2: The absolute value of 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.

[0076] Conditional equation (18) defines the 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 equation (18), spherical aberration, coma aberration, field curvature, etc., can be corrected well.

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

[0078] The optical system OL according to the first and second embodiments preferably satisfies the following condition (19). 20.00°<2ω<40.00° ···(19) However, 2ω: the entire field of view of the optical system OL

[0079] Conditional equation (19) defines an appropriate range for the entire field of view of the optical system OL. Satisfying conditional equation (19) is preferable because it allows for the acquisition of an optical system with a wide field of view. Setting the lower limit of conditional equation (19) to 22.00°, 24.00°, 26.00°, and further to 27.00° makes the effects of each embodiment more reliable. Furthermore, setting the upper limit of conditional equation (19) to 38.00°, 37.00°, and further to 36.00° makes the effects of each embodiment more reliable.

[0080] The optical system OL according to the first and second embodiments preferably satisfies the following condition (20). 0.08 <Bf / f<1.20 ···(20) However, Bf: back focus of the optical system OL f: focal length of optical system OL

[0081] Conditional equation (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 equation (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 equation (20) to 0.09, 0.10, 0.11, and further to 0.12, the effects of each embodiment can be made more reliable. Furthermore, by setting the upper limit of conditional equation (20) to 1.18, 1.15, 1.13, 1.10, 1.08, 1.05, and further to 1.03, the effects of each embodiment can be made more reliable.

[0082] Next, with reference to Figure 23, the manufacturing method of the optical system OL according to the first embodiment will be outlined. First, the front group GA, the aperture (diaphragm) 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, which has negative refractive power, is placed on the object side of the rear group GB, and the second focusing lens group GF2, which has negative refractive power, is placed on the image plane side of the rear group GB than the first focusing lens group GF1 (step ST2). Then, when focusing from an object at infinity to an object at close range, the lenses are arranged in the lens barrel such that the first focusing lens group GF1 and the second focusing lens group GF2 move toward the image plane along the optical axis on different trajectories (step ST3). With this manufacturing method, it is possible to manufacture an optical system with little aberration variation during focusing.

[0083] Next, with reference to Figure 24, the manufacturing method of the optical system OL according to the second embodiment will be outlined. First, along the optical axis, in order from the object side, 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 (step ST11). Then, when focusing from an object at infinity to an object at a close distance, the lenses are arranged in the lens barrel such that the first focusing lens group GF1 and the second focusing lens group GF2 move toward the image plane along the optical axis on different trajectories (step ST12). With this manufacturing method, it is possible to manufacture an optical system with little aberration variation during focusing. [Examples]

[0084] The optical system OL according to each embodiment will be described below based on the drawings. The embodiments corresponding to the first embodiment are the first to seventh embodiments and the tenth embodiment, and the embodiments corresponding to the second embodiment are the first to tenth embodiments. Figures 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19 are cross-sectional views showing the configuration and refractive power distribution of the optical system OL{OL(1) to OL(10)} according to the first to tenth embodiments. In the cross-sectional views of the optical systems OL(1) to OL(10) according to the first to tenth embodiments, the direction of movement along the optical axis of each lens group when focusing from infinity to a near-field object is indicated by arrows. In the cross-sectional view of the optical system OL(10) according to the tenth embodiment, the direction of movement along the optical axis of each lens group when changing magnification from the wide-angle end state (W) to the telephoto end state (T) is indicated by arrows.

[0085] In these figures (Figures 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, in order to prevent the number and types of symbols and numbers from becoming too large and complicated, each embodiment uses a separate combination of symbols and numbers to represent the lens groups, etc. Therefore, even if the same combination of symbols and numbers is used between embodiments, it does not mean that they have the same configuration.

[0086] Tables 1 to 10 are shown below. Table 1 shows the specifications for the first example, Table 2 for the second example, Table 3 for the third example, Table 4 for the fourth example, Table 5 for the fifth example, Table 6 for the sixth example, Table 7 for the seventh example, Table 8 for the eighth example, Table 9 for the ninth example, and Table 10 for the tenth example. In each example, the d-line (wavelength λ=587.6nm) and the g-line (wavelength λ=435.8nm) 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 (in degrees, where ω is half the angle of view), and Y is the image height. TL is the distance from the frontmost lens to the final lens surface on the optical axis when focused at infinity, plus Bf, and Bf is the distance from the final lens surface to the image plane I on the optical axis when focused at infinity (back focus). Also, TL(a) is the distance on the optical axis from the lens surface closest to the object in the optical system to the image plane I (air equivalent distance) when focused at infinity. Bf(a) is the distance on the optical axis from the lens surface closest to the image plane in the optical system to the image plane I (air equivalent distance) when focused at infinity. Note that if the optical system is a variable magnification optical system, these values ​​are shown for each magnification state at the wide-angle end (W), intermediate focal length (M), and telephoto end (T).

[0088] In addition, in the [Overall Specifications] table, fA indicates the focal length of the leading lens group. fB indicates the combined focal length of the lens groups positioned 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 amount of movement of the first focusing lens group when focusing from an object at infinity to a nearby object. MF2 indicates the absolute value of the amount of movement of the second focusing lens group when focusing from an object at infinity to a nearby 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 propagation; R is the radius of curvature of each optical surface (a positive value is given for surfaces where the center of curvature is located on the image side); D is the interplanar spacing, which is the distance along the optical axis from each optical surface to the next optical surface (or image plane); nd is the refractive index of the optical component material with respect to the d line; and νd is the Abbe number with respect to the d line of the optical component material. "∞" for the radius of curvature indicates a plane or aperture, and (Aperture S) indicates an aperture diaphragm S. The refractive index of air nd = 1.00000 is omitted.

[0090] The [Variable Interval Data] table shows the interval at surface number i, where the interval is (Di) in the [Lens Specifications] table. If the optical system is not a variable magnification optical system, in the [Variable Interval Data] table, f represents the focal length of the entire lens system, and β represents the magnification. Also, D0 represents the distance from the object to the optical surface closest to the object in the optical system. If the optical system is a variable magnification optical system, the [Variable Interval Data] table shows the interval at surface number i, where the interval is (Di) in the [Lens Specifications] table, corresponding to each magnification state at the wide-angle end (W), intermediate 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 for each lens group.

[0092] In all specifications listed below, the focal length f, radius of curvature R, interplanar spacing D, and other lengths are generally expressed in "mm" unless otherwise specified. However, since optical systems can achieve equivalent optical performance even when proportionally enlarged or reduced, this is not the only way to express them.

[0093] The explanations in the table above are common to all examples, and any redundant explanations below will be omitted.

[0094] (First embodiment) The first embodiment will be described using Figures 1 and 2 and Table 1. Figure 1 is a diagram showing the lens configuration of the optical system according to the first embodiment. The optical system OL(1) according to the first embodiment consists of 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, all arranged in order from the object side along the optical axis. When focusing from an object at infinity to an object at a close distance, the second lens group G2 and the fourth lens group G4 move toward the image side along the optical axis along different trajectories (amount of movement), and the spacing between adjacent lens groups changes. At the time of focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of each lens group, and this is the same in all the following examples.

[0095] The aperture diaphragm S is positioned between the first lens group G1 and the second lens group G2. When focusing, the aperture diaphragm S is fixed in position 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, third lens group G3, fourth lens group G4, and fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the preceding 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 consists of a positive meniscus lens L11 with its convex surface facing the object, arranged in order from the object side along the optical axis; a positive meniscus lens L12 with its convex surface facing the object; a cemented lens formed by joining a positive meniscus lens L13 with its convex surface facing the object and a negative meniscus lens L14 with its convex surface facing the object; a negative meniscus lens L15 with its convex surface facing the object; and a positive meniscus lens L16 with its convex surface facing the object. The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object.

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

[0098] The fifth lens group G5 consists of a cemented lens formed by joining a biconvex positive lens L51 and a negative meniscus lens L52 with its concave surface facing the object, arranged in order from the object side along the optical axis, and a negative meniscus lens L53 with its concave surface facing the object. The image plane I is positioned on the image side of the fifth lens group G5. A parallel plate PP is positioned between the fifth lens group G5 and the image plane I.

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

[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] Face 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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] Figure 2(A) is an aberration diagram of the optical system according to the first embodiment when focused at infinity. Figure 2(B) is an aberration diagram of the optical system according to the first embodiment when focused at close range. In each aberration diagram when focused at infinity, FNO indicates the F number and Y indicates the image height. In each aberration diagram when focused at close range, 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 and distortion diagrams show the maximum image height, and the coma aberration diagram shows the values ​​of each image height. d indicates the d line (wavelength λ=587.6nm), and g indicates the g line (wavelength λ=435.8nm). 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 reference numerals as in this embodiment are used in the aberration diagrams of the embodiments shown below, and redundant explanations are omitted.

[0102] From the various aberration diagrams, it can be seen that the optical system according to the first embodiment has excellent imaging performance, with aberrations well corrected throughout the entire range from infinity focus to close-up focus.

[0103] (Second example) The second embodiment will be explained using Figures 3-4 and Table 2. Figure 3 is a diagram showing the lens configuration of the optical system according to the second embodiment. The optical system OL(2) according to the second embodiment consists of 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, all arranged in order from the object side along the optical axis. When focusing from an object at infinity to an object at a close distance, the second lens group G2 and the fourth lens group G4 move toward the image side along the optical axis along different trajectories (amount of movement), and the spacing between adjacent lens groups changes. At the time of focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I.

[0104] The aperture diaphragm S is positioned between the first lens group G1 and the second lens group G2. When focusing, the aperture diaphragm S is fixed in position 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, third lens group G3, fourth lens group G4, and fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the preceding 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 consists of a positive meniscus lens L11 with its convex surface facing the object, arranged in order from the object side along the optical axis; a positive meniscus lens L12 with its convex surface facing the object; a cemented lens formed by joining a biconvex positive lens L13 and a biconcave negative lens L14; and a positive meniscus lens L15 with its convex surface facing the object. The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object.

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

[0107] The fifth lens group G5 consists of a positive meniscus lens L51 with its convex surface facing the object and a negative meniscus lens L52 with its concave surface facing the object, arranged in order from the object side along the optical axis. The image plane I is positioned on the image side of the fifth lens group G5. A parallel plate PP is positioned between the fifth lens group G5 and the image plane I.

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

[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] Face 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) (Aperture S) 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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] Figure 4(A) shows the aberrations of the optical system according to the second embodiment when focused at infinity. Figure 4(B) shows the aberrations of the optical system according to the second embodiment when focused at close range. From each aberration diagram, it can be seen that the optical system according to the second embodiment has excellent imaging performance, with aberrations well corrected across the entire range from infinity focus to close range focus.

[0111] (Third embodiment) The third embodiment will be explained using Figures 5-6 and Table 3. Figure 5 is a diagram showing the lens configuration of the optical system according to the third embodiment. The optical system OL(3) according to the third embodiment consists of 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, all arranged in order from the object side along the optical axis. When focusing from an object at infinity to an object at a close distance, the second lens group G2 and the fourth lens group G4 move toward the image side along the optical axis along different trajectories (amount of movement), and the spacing between adjacent lens groups changes. At the time of focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I.

[0112] The aperture diaphragm S is positioned between the first lens group G1 and the second lens group G2. When focusing, the aperture diaphragm S is fixed in position 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, third lens group G3, fourth lens group G4, and fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the preceding 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 consists of a positive meniscus lens L11 with its convex surface facing the object, a positive meniscus lens L12 with its convex surface facing the object, and a cemented lens formed by joining a biconvex positive lens L13 and a biconcave negative lens L14, all arranged in order from the object side along the optical axis. The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object.

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

[0115] The fifth lens group G5 consists of a positive meniscus lens L51 with its convex surface facing the object and a negative meniscus lens L52 with its concave surface facing the object, arranged in order from the object side along the optical axis. The image plane I is positioned on the image side of the fifth lens group G5. A parallel plate PP is positioned between the fifth lens group G5 and the image plane I.

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

[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] Face 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) (Aperture S) 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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] Figure 6(A) shows the aberrations of the optical system according to the third embodiment when focused at infinity. Figure 6(B) shows the aberrations of the optical system according to the third embodiment when focused at close range. From each aberration diagram, it can be seen that the optical system according to the third embodiment has excellent imaging performance, with aberrations well corrected across the entire range from infinity focus to close range focus.

[0119] (Fourth embodiment) The fourth embodiment will be explained using Figures 7-8 and Table 4. Figure 7 is a diagram showing the lens configuration of the optical system according to the fourth embodiment. The optical system OL(4) according to the fourth embodiment consists of 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, all arranged in order from the object side along the optical axis. When focusing from an object at infinity to an object at a close distance, the second lens group G2 and the fourth lens group G4 move toward the image side along the optical axis along different trajectories (amount of movement), and the spacing between adjacent lens groups changes. At the time of focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I.

[0120] The aperture diaphragm S is positioned between the first lens group G1 and the second lens group G2. When focusing, the aperture diaphragm S is fixed in position 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, third lens group G3, fourth lens group G4, and fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the preceding 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 consists of a positive meniscus lens L11 with its convex surface facing the object, arranged in order from the object side along the optical axis; a cemented lens formed by joining a positive meniscus lens L12 with its convex surface facing the object and a negative meniscus lens L13 with its convex surface facing the object; and a cemented lens formed by joining a biconvex positive lens L14 and a biconcave negative lens L15. The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object.

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

[0123] The fifth lens group G5 consists of three lenses arranged in order from the object side along the optical axis: a negative meniscus lens L51 with its convex surface facing the object, a positive meniscus lens L52 with its convex surface facing the object, and a negative meniscus lens L53 with its concave surface facing the object. The image plane I is positioned on the image side of the fifth lens group G5. A parallel plate PP is positioned between the fifth lens group G5 and the image plane I.

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

[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] Face 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) (Aperture S) 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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] Figure 8(A) shows the aberrations of the optical system according to the fourth embodiment when focused at infinity. Figure 8(B) shows the aberrations of the optical system according to the fourth embodiment when focused at close range. From each aberration diagram, it can be seen that the optical system according to the fourth embodiment has excellent imaging performance, with aberrations well corrected across the entire range from infinity focus to close range focus.

[0127] (Fifth example) The fifth embodiment will be explained using Figures 9 to 10 and Table 5. Figure 9 is a diagram showing the lens configuration of the optical system according to the fifth embodiment. The optical system OL(5) according to the fifth embodiment consists of 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, all arranged in order from the object side along the optical axis. When focusing from an object at infinity to an object at a close distance, the second lens group G2 and the fourth lens group G4 move toward the image side along the optical axis along different trajectories (amount of movement), and the spacing between adjacent lens groups changes. At the time of focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I.

[0128] The aperture diaphragm S is positioned between the first lens group G1 and the second lens group G2. When focusing, the aperture diaphragm S is fixed in position 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, third lens group G3, fourth lens group G4, and fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the preceding 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 consists of a positive meniscus lens L11 with its convex surface facing the object, arranged in order from the object side along the optical axis; a cemented lens formed by joining a biconvex positive lens L12 and a biconcave negative lens L13; and a cemented lens formed by joining a negative meniscus lens L14 with its convex surface facing the object and a positive meniscus lens L15 with its convex surface facing the object. The second lens group G2 consists of a cemented lens with negative refractive power, formed by joining a positive meniscus lens L21 with its concave surface facing the object and a biconcave negative lens L22, arranged in order from the object side.

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

[0131] The fifth lens group G5 consists of a cemented lens formed by joining a negative meniscus lens L51 with a convex surface facing the object side and a biconvex positive lens L52, arranged in order from the object side along the optical axis, and a negative meniscus lens L53 with a concave surface facing the object side. The image plane I is positioned on the image side of the fifth lens group G5. A parallel plate PP is positioned between the fifth lens group G5 and the image plane I.

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

[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 βF2 =1.291 TL=116.082 MF1=11.502 Bf=1.000 MF2=2.759 TL(a) = 115.537 Bf(a) = 11.055 [Lens Specifications] Face 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) (Aperture S) 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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] Figure 10(A) shows the aberrations of the optical system according to the fifth embodiment when focused at infinity. Figure 10(B) shows the aberrations of the optical system according to the fifth embodiment when focused at close range. From each aberration diagram, it can be seen that the optical system according to the fifth embodiment has excellent imaging performance, with aberrations well corrected across the entire range from infinity focus to close range focus.

[0135] (Sixth embodiment) The sixth embodiment will be described using Figures 11-12 and Table 6. Figure 11 is a diagram showing the lens configuration of the optical system according to the sixth embodiment. The optical system OL(6) according to the sixth embodiment consists of 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, all arranged in order from the object side along the optical axis. When focusing from an object at infinity to an object at a close distance, the second lens group G2 and the fourth lens group G4 move towards the image side along the optical axis along different trajectories (amount of movement), and the spacing between adjacent lens groups changes. At the time of focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I.

[0136] The aperture diaphragm S is positioned between the first lens group G1 and the second lens group G2. When focusing, the aperture diaphragm S is fixed in position 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, third lens group G3, fourth lens group G4, and fifth lens group G5 constitute the rear group GB. Furthermore, the first lens group G1 corresponds to the preceding 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 consists of a positive meniscus lens L11 with its convex surface facing the object, a positive meniscus lens L12 with its convex surface facing the object, a cemented lens formed by joining a positive meniscus lens L13 with its convex surface facing the object and a negative meniscus lens L14 with its convex surface facing the object, a negative meniscus lens L15 with its convex surface facing the object, and a positive meniscus lens L16 with its convex surface facing the object, all arranged in order from the object side along the optical axis. The second lens group G2 consists of a cemented lens with negative refractive power formed by joining a negative meniscus lens L21 with its convex surface facing the object and a negative meniscus lens L22 with its convex surface facing the object, all arranged in order from the object side.

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

[0139] The fifth lens group G5 consists of a cemented lens formed by joining a biconvex positive lens L51 and a negative meniscus lens L52 with its concave surface facing the object, arranged in order from the object side along the optical axis, and a negative meniscus lens L53 with its concave surface facing the object. The image plane I is positioned on the image side of the fifth lens group G5. A parallel plate PP is positioned between the fifth lens group G5 and the image plane I.

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

[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] Face 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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] Figure 12(A) shows the aberrations of the optical system according to the sixth embodiment when focused at infinity. Figure 12(B) shows the aberrations of the optical system according to the sixth embodiment when focused at close range. From each aberration diagram, it can be seen that the optical system according to the sixth embodiment has excellent imaging performance, with aberrations well corrected across the entire range from infinity focus to close range focus.

[0143] (Seventh Example) The seventh embodiment will be explained using Figures 13-14 and Table 7. Figure 13 is a diagram showing the lens configuration of the optical system according to the seventh embodiment. The optical system OL(7) according to the seventh embodiment consists of 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, all arranged in order from the object side along the optical axis. When focusing from an object at infinity to an object at a close distance, the second lens group G2 and the fourth lens group G4 move toward the image side along the optical axis along different trajectories (amount of movement), and the spacing between adjacent lens groups changes. At the time of focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I.

[0144] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the position of the aperture stop S is fixed with respect 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. Also, the first lens group G1 corresponds to the preceding 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 a positive meniscus lens L11 with a convex surface facing the object side, arranged in order from the object side along the optical axis, 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 a cemented lens having a negative refractive power, which is formed by cementing, in order from the object side, 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 a cemented lens formed by cementing, in order from the object side along the optical axis, 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 a cemented lens having a negative refractive power, which is formed by cementing, in order from the object side, 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 a negative meniscus lens L51 with a convex surface facing the object side, arranged in order from the object side along the optical axis, a biconvex positive lens L52, and a negative meniscus lens L53 with a concave surface facing the object side. The image plane I is disposed on the image side of the fifth lens group G5. A parallel plate PP is disposed between the fifth lens group G5 and the image plane I.

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

[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 R D 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) (Aperture S) 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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 of various aberrations when the optical system according to the seventh embodiment is focused at infinity. FIG. 14(B) is a diagram of various aberrations when the optical system according to the seventh embodiment is focused at a short distance. From each diagram of various aberrations, it can be seen that the optical system according to the seventh embodiment has good correction of various aberrations and excellent imaging performance throughout the range from infinity focus to short distance focus.

[0151] (Eighth Embodiment) The eighth embodiment will be described with reference to FIGS. 15 to 16 and Table 8. FIG. 15 is a diagram showing the lens configuration of the optical system according to the eighth embodiment. The optical system OL(8) according to the eighth embodiment includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a negative refractive power, which are arranged in order from the object side along the optical axis. When focusing from an infinite object to a short distance object, the second lens group G2 and the fourth lens group G4 move toward the image side along the optical axis with different trajectories (amounts of movement), and the intervals between adjacent lens groups change. Note that when focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I.

[0152] The aperture stop S is disposed between the second lens group G2 and the third lens group G3. When focusing, the position of the aperture stop S is fixed with respect to the image plane I. In this embodiment, the first lens group G1 corresponds to the front 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 includes 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, which are arranged in order from the object side along the optical axis. The second lens group G2 consists of a biconcave negative lens L21.

[0154] The third lens group G3 consists of a biconvex positive lens L31, a biconcave negative lens L32, a biconvex positive lens L33, and a biconvex positive lens L34, arranged in order from the object side along the optical axis. The fourth lens group G4 consists of a cemented lens with negative refractive power, formed by joining a biconcave negative lens L41 and a positive meniscus lens L42 with its convex surface facing the object side, arranged in order from the object side.

[0155] The fifth lens group G5 consists of a positive meniscus lens L51 with its convex surface facing the object and a negative meniscus lens L52 with its concave surface facing the object, arranged in order from the object side along the optical axis. The image plane I is positioned on the image side of the fifth lens group G5. A parallel plate PP is positioned between the fifth lens group G5 and the image plane I.

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

[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] Face 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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] Figure 16(A) shows the aberrations of the optical system according to the eighth embodiment when focused at infinity. Figure 16(B) shows the aberrations of the optical system according to the eighth embodiment when focused at close range. From each aberration diagram, it can be seen that the optical system according to the eighth embodiment has excellent imaging performance, with aberrations well corrected across the entire range from infinity focus to close range focus.

[0159] (9th example) The ninth embodiment will be explained using Figures 17-18 and Table 9. Figure 17 is a diagram showing the lens configuration of the optical system according to the ninth embodiment. The optical system OL(9) according to the ninth embodiment consists of 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, all arranged in order from the object side along the optical axis. When focusing from an object at infinity to an object at a close distance, the second lens group G2 and the fourth lens group G4 move toward the image side along the optical axis along different trajectories (amount of movement), and the spacing between adjacent lens groups changes. At the time of focusing, the positions of the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image plane I.

[0160] The aperture diaphragm S is positioned between the second lens group G2 and the third lens group G3. When focusing, the aperture diaphragm S is fixed in position relative to the image plane I. In this embodiment, the first lens group G1 corresponds to the preceding 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 consists of a biconvex positive lens L11, a cemented lens formed by joining a biconvex positive lens L12 and a biconcave negative lens L13, and a positive meniscus lens L14 with its convex surface facing the object, arranged in order from the object side along the optical axis. The second lens group G2 consists of a cemented lens with negative refractive power formed by joining a biconvex positive lens L21 and a biconcave negative lens L22, arranged in order from the object side.

[0162] The third lens group G3 consists of a biconvex positive lens L31, a cemented lens formed by joining a biconcave negative lens L32 and a biconvex positive lens L33, and a biconvex positive lens L34, arranged in order from the object side along the optical axis. The fourth lens group G4 consists of a cemented lens with negative refractive power formed by joining 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, arranged in order from the object side.

[0163] The fifth lens group G5 consists of a cemented lens formed by joining a biconvex positive lens L51 and a negative meniscus lens L52 with its concave surface facing the object, arranged in order from the object side along the optical axis, and a negative meniscus lens L53 with its concave surface facing the object. The image plane I is positioned on the image side of the fifth lens group G5. A parallel plate PP is positioned between the fifth lens group G5 and the image plane I.

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

[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] Face 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] Infinity focus state, intermediate distance focus state, very close distance focus state 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] Figure 18(A) shows the aberrations of the optical system according to the ninth embodiment when focused at infinity. Figure 18(B) shows the aberrations of the optical system according to the ninth embodiment when focused at close range. From each aberration diagram, it can be seen that the optical system according to the ninth embodiment has excellent imaging performance, with aberrations well corrected across the entire range from infinity focus to close range focus.

[0167] (Tenth example) The 10th embodiment will be explained using Figures 19 to 21 and Table 10. Figure 19 is a diagram showing the lens configuration of the optical system according to the 10th embodiment. The optical system OL(10) according to the 10th embodiment consists of 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, all arranged in order from the object side along the optical axis. When changing magnification from the wide-angle end state (W) to the telephoto end state (T), the first to eighth lens groups G1 to G8 move towards the object side along the optical axis, and the spacing between adjacent lens groups changes. 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 toward the image along the optical axis along different trajectories (amount of movement). At the time of 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] The aperture diaphragm S is positioned 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 aperture diaphragm S is fixed in position relative to the image plane I together with the third lens group G3. 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] Furthermore, in this embodiment, the parameter values ​​corresponding to each of the aforementioned conditional equations (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 combined 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 combined 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 consists of a cemented lens formed by joining a negative meniscus lens L11 with its convex surface facing the object and a biconvex positive lens L12, which are arranged in order from the object side along the optical axis, and a positive meniscus lens L13 with its convex surface facing the object. The second lens group G2 consists of a cemented lens formed by joining a negative meniscus lens L21 with its convex surface facing the object and a biconcave negative lens L22 and a positive meniscus lens L23 with its convex surface facing the object, which are arranged in order from the object side along the optical axis.

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

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

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

[0174] Table 10 below lists the specifications of the optical system according to the 10th embodiment.

[0175] (Table 10) [Overall Specifications] Multiplication 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] Face 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] Infinity focus state Intermediate distance focus state 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] Figure 20(A) is an aberration diagram of the optical system according to the 10th embodiment when focused at infinity at the wide-angle end. Figure 20(B) is an aberration diagram of the optical system according to the 10th embodiment when focused at close range at the wide-angle end. Figure 21(A) is an aberration diagram of the optical system according to the 10th embodiment when focused at infinity at the telephoto end. Figure 21(B) is an aberration diagram of the optical system according to the 10th embodiment when focused at close range at the telephoto end. From each aberration diagram, it can be seen that the optical system according to the 10th embodiment has excellent imaging performance, with aberrations well corrected not only at the wide-angle end but also at the telephoto end, across the entire range from infinity focus to close range focus.

[0177] Next, the table of [Conditional Expression Corresponding Values] is shown below. This table summarizes the values ​​corresponding to each conditional expression (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 Conditional expression (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 Conditional expression (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< MF2 / MF1 <0.80 Conditional expression (19) 20.00°<2ω<40.00° Conditional expression (20) 0.08 <Bf / f<1.20

[0178] [Conditional Expression Corresponding Values] (Examples 1-4) Conditional expression First example Second example Third example Fourth 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] (Examples 5-8) 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 9-10) 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 2.336 (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 the above embodiments, an optical system with minimal aberration variation during focusing can be realized.

[0180] The above embodiments illustrate specific examples of the present invention, and the present invention is not limited to these.

[0181] The following elements can be appropriately incorporated as long as they do not impair the optical performance of the optical system of this embodiment.

[0182] Although the optical system of this embodiment is shown with a 5-group configuration and an 8-group configuration, this application is not limited to these, and optical systems with other group configurations (e.g., 6-group, 9-group, etc.) can also be constructed. Specifically, the optical system of this embodiment may be configured by adding lenses or lens groups to the object side or the image plane side. A lens group refers to a portion having at least one lens, separated by an air gap that changes during focusing or magnification.

[0183] A lens group or partial lens group may be moved so that it has a component perpendicular to the optical axis, or rotated (oscillated) in the in-plane direction including the optical axis, to correct image blur caused by camera shake.

[0184] The lens surface may be formed as a spherical, flat, or aspherical surface. A spherical or flat lens surface is preferable because it facilitates lens processing and assembly adjustment, preventing degradation of optical performance due to processing and assembly errors. It is also preferable because it minimizes degradation of image rendering performance even if the image plane is misaligned.

[0185] If the lens surface is aspherical, it can be an aspherical surface created by grinding, a glass molded aspherical surface formed from glass using a mold, or a composite aspherical surface formed by creating an aspherical shape from resin on the surface of glass. Furthermore, the lens surface may also be a diffractive surface, and the lens may be a refractive index distributed lens (GRIN lens) or a plastic lens.

[0186] The aperture diaphragm is preferably positioned between the first and second lens groups, or between the second and third lens groups, or between the third and fourth lens groups. However, the function of the aperture diaphragm may be substituted by the lens frame without providing a separate component.

[0187] Each lens surface may be coated with an anti-reflective 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 diaphragm

Claims

1. It consists of a front group, an aperture, and a rear group, arranged in order from the object side along the optical axis. The aforementioned front group consists of a preceding lens group composed of one lens group having positive refractive power. The rear group consists of a first focusing lens group having negative refractive power, arranged in order from the object side of the rear group; 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 toward the image plane along the optical axis in different trajectories. An optical system in which both the first focusing lens group and the second focusing lens group consist of one or two lenses, and satisfy the following conditional equation. 0.862≦f / (-fF1)<1.80 However, f: focal length of the optical system fF1: Focal length of the first focusing lens group

2. The optical system according to claim 1, satisfying the following conditional expression. 0.30<STL / TL<0.90 However, STL: distance along the optical axis from the aperture to the image plane. TL: Total length of the optical system

3. The optical system according to claim 1 or 2, wherein when focusing from an object at infinity to an object at a close distance, the positive lens group is fixed in position with respect to the image plane.

4. An optical system according to any one of claims 1 to 3 that satisfies the following conditional expression. 0.35<fB / (-fF1)<1.50 However, fB: the combined 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. It consists of a leading lens group with positive refractive power, a first focusing lens group with negative refractive power, a positive lens group with positive refractive power, a second focusing lens group with negative refractive power, and a final lens group, all arranged in order from the object side along the optical axis. 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 toward the image plane along the optical axis in different trajectories. An optical system in which both the first focusing lens group and the second focusing lens group consist of one or two lenses, and satisfy the following conditional equation. 0.862≦f / (-fF1)<1.80 0.35<fB / (-fF1)≦0.867 -2.00<(-fE) / f<15.00 However, f: focal length of the optical system fF1: Focal length of the first focusing lens group fB: Combined 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. It consists of a leading lens group with positive refractive power, a first focusing lens group with negative refractive power, a positive lens group with positive refractive power, a second focusing lens group with negative refractive power, and a final lens group, all arranged in order from the object side along the optical axis. 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 toward the image plane along the optical axis in different trajectories. Both the first focusing lens group and the second focusing lens group are composed of one or two lenses. The aforementioned positive lens group comprises a negative lens, a first positive lens, and a second positive lens, arranged in order from the object side along the optical axis, and is an optical system that satisfies the following condition. 0.862≦f / (-fF1)<1.80 0.35<fB / (-fF1)≦0.867 However, f: focal length of the optical system fF1: Focal length of the first focusing lens group fB: Combined focal length of the positive lens group, the second focusing lens group, and the final lens group.

7. The optical system according to claim 5 or 6, wherein an aperture is arranged between the preceding lens group and the first focusing lens group.

8. The optical system according to claim 7, satisfying the following conditional expression. 0.30<STL / TL<0.90 However, STL: distance along the optical axis from the aperture to the image plane. TL: Total length of the optical system

9. An optical system according to any one of claims 1 to 8 that satisfies the following conditional expression. 0.50<fA / f<2.00 However, fA: focal length of the preceding lens group. f: Focal length of the optical system

10. An optical system according to any one of claims 1 to 9 that satisfies the following conditional expression. 0.50<fA / (-fF1)<1.50 However, fA: focal length of the preceding lens group. fF1: Focal length of the first focusing lens group

11. An optical system according to any one of claims 1 to 4, 6 to 10, which satisfies the following conditional expression. -2.00<(-fE) / f<15.00 However, fE: focal length of the final lens group. f: Focal length of the optical system

12. An optical system according to any one of claims 1 to 11 that satisfies the following conditional expression. -1.00<fP / (-fE)<1.50 However, fP: focal length of the positive lens group. fE: Focal length of the final lens group

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

14. An optical system according to any one of claims 1 to 13 that satisfies the following conditional expression. 0.30<fP / f<1.00 However, fP: focal length of the positive lens group. f: Focal length of the optical system

15. The optical system according to any one of claims 1 to 14, wherein the positive lens group comprises a negative lens, a first positive lens, and a second positive lens, arranged in order from the object side along the optical axis.

16. An optical system according to any one of claims 1 to 5, 7 to 15, that satisfies the following conditional expression. 0.10<fF1 / fF2<2.00 However, fF1: focal length of the first focusing lens group. fF2: Focal length of the second focusing lens group

17. The optical system according to any one of claims 1 to 16, wherein the first focusing lens group comprises one negative lens component.

18. An optical system according to any one of claims 1 to 17 that satisfies the following conditional expression. -2.50<(rF12+rF11) / (rF12-rF11)<0.00 However, rF11: 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 closest to the image plane in the first focusing lens group.

19. The optical system according to any one of claims 1 to 18, wherein the second focusing lens group comprises one negative lens component.

20. An optical system according to any one of claims 1 to 19 that satisfies the following conditional expression. 0.05<Bf / TL<0.80 However, Bf: Back focus of the optical system. TL: Total length of the optical system

21. An optical system according to any one of claims 1 to 20 that satisfies the following conditional expression. -0.80<(rR2+rR1) / (rR2-rR1)<2.50 However, rR1: radius of curvature of the object-side lens surface in the lens positioned closest to the image plane in the optical system. rR2: Radius of curvature of the lens surface on the image plane side of the lens positioned closest to the image plane in the optical system.

22. An optical system according to any one of claims 1 to 21 that satisfies the following conditional expression. 0.01<1 / βF1<0.60 However, βF1: The lateral magnification of the first focusing lens group when an object at infinity is in focus.

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

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

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

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

27. An optical system according to any one of claims 1 to 26 that satisfies the following conditional expression. 20.00°<2ω<40.00° However, 2ω: the entire field of view of the optical system.

28. An optical system according to any one of claims 1 to 27 that satisfies the following conditional expression. 0.08<Bf / f<1.20 However, Bf: Back focus of the optical system. f: Focal length of the optical system

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

Images