Optical system and optical apparatus

Abstract

To provide an optical system with less fluctuation in an angle of view upon focusing.SOLUTION: An optical system OL comprises a preceding lens group GA having negative refractive power and a succeeding lens group GB having positive refractive power, arranged in order from an object side along an optical axis. The succeeding lens group GB includes a focusing group GF having positive refractive power disposed closest to the object side of the succeeding lens group GB and an image-side group GC disposed closer to an image side than the focusing group GF. The focusing group GF moves toward the image side along the optical axis while focusing from an infinitely distant object to a short-distance object. The image-side group GC has a lens group having negative refractive power disposed closest to the image side.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, optical systems suitable for photo cameras, electronic still cameras, video cameras, etc. have been proposed (see, for example, Patent Document 1). In such optical systems, there is a demand for suppressing fluctuations in the angle of view during focusing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-117419 A Summary of the Invention

[0004] A first optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a first lens group having negative refractive power and a subsequent group having positive refractive power, the subsequent group comprising, arranged in order from the object side along the optical axis, a second lens group having positive refractive power and an image-side group having a plurality of lens groups, the second lens group moving during focusing to change the spacing between adjacent lens groups, and satisfying the following conditional expression: 1.00<βB / βC<10.00 however, βB: Magnification of the succeeding lens group when focusing on an object at infinity βC: Magnification of the image-side group when focusing on an object at infinity

[0005] A second optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a first lens group having negative refractive power and a subsequent group having positive refractive power, the subsequent group comprising, arranged in order from the object side along the optical axis, a second lens group having positive refractive power, and an image-side group having a plurality of lens groups, the second lens group moving during focusing to change the spacing between adjacent lens groups, and satisfying the following conditional expression: 0.78 <fB / fC<1.00 however, fB: focal length of the subsequent group when focusing on an object at infinity fC: focal length of the image-side group when focusing on an object at infinity

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

[0007] [Figure 1] FIG. 2 is a diagram showing a lens configuration of an optical system according to a first example. [Diagram 2] 2A and 2B are diagrams showing various aberrations in the optical system according to the first example when focused on infinity and when focused on a close distance, respectively. [Diagram 3] FIG. 13 is a diagram showing a lens configuration of an optical system according to a second example. [Figure 4] 4A and 4B are diagrams showing various aberrations in the optical system according to the second example when focused on infinity and when focused on a close distance, respectively. [Diagram 5] FIG. 13 is a diagram showing a lens configuration of an optical system according to a third example. [Figure 6] 6A and 6B are diagrams showing various aberrations in the optical system according to the third example when focused on infinity and when focused on a close distance, respectively. [Figure 7] FIG. 1 is a diagram showing a configuration of a camera including an optical system according to each embodiment. [Figure 8] 4 is a flowchart illustrating a method for manufacturing an optical system according to each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Preferred embodiments of the present invention will be described below. First, a camera (optical device) equipped with an optical system according to each embodiment will be described with reference to FIG. 7. As shown in FIG. 7, this camera 1 is composed of a body 2 and a photographing lens 3 attached to the body 2. The body 2 is equipped with an image sensor 4, a body control unit (not shown) that controls the operation of the digital camera, and a liquid crystal screen 5. The photographing lens 3 is equipped with an optical system OL consisting of a plurality of lens groups, and a lens position control mechanism (not shown) that controls the position of each lens group. The lens position control mechanism is composed of a sensor that detects the position of the lens groups, a motor that moves the lens groups back and forth along the optical axis, a control circuit that drives the motor, and the like.

[0009] Light from the subject is collected by the optical system OL of the photographing lens 3 and reaches the image plane I of the image sensor 4. The light from the subject that reaches the image plane I is photoelectrically converted by the image sensor 4 and recorded as digital image data in a memory (not shown). The digital image data recorded in the memory can be displayed on the liquid crystal screen 5 in response to a user's operation. This camera may be a mirrorless camera or a single-lens reflex camera having a quick-return mirror.

[0010] Next, an optical system according to the first embodiment will be described. As shown in FIG. 1, an optical system OL(1) as an example of an optical system (photographing lens) OL according to the first embodiment is composed of a leading lens group GA having negative refractive power and a trailing lens group GB having positive refractive power, which are arranged in order from the object side along the optical axis. The trailing lens group GB has a focusing group GF having positive refractive power, which is arranged closest to the object side of the trailing lens group GB, and an image side group GC, which is arranged on the image side of the focusing group GF. When focusing from an object at infinity to an object at a close distance, the focusing group GF moves toward the image side along the optical axis.

[0011] With the above-mentioned configuration, the optical system OL according to the first embodiment satisfies the following conditional expression (1). 0.78 <fB / fC<1.00 ···(1) where fB is the focal length of the subsequent lens group GB when focusing on an object at infinity fC: focal length of the image-side group GC when focusing on an object at infinity

[0012] According to the first embodiment, it is possible to obtain an optical system with little fluctuation in the angle of view during focusing, and an optical device including this optical system. The optical system OL according to the first embodiment may be the optical system OL(2) shown in Fig. 3 or the optical system OL(3) shown in Fig. 5.

[0013] Condition (1) defines an appropriate relationship between the focal length of the rear lens group GB when focusing on an object at infinity and the focal length of the image-side lens group GC when focusing on an object at infinity. By satisfying condition (1), it is possible to reduce fluctuations in the angle of view when focusing.

[0014] If the corresponding value of conditional expression (1) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (1) to 0.79, 0.80, 0.81, 0.82, or even 0.83, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (1) to 0.98, 0.96, 0.95, or even 0.94, the effect of this embodiment can be made more certain.

[0015] It is desirable for the optical system OL according to the first embodiment to satisfy the following conditional expression (2). 0.010 <BLDF / TL<0.160 ···(2) Where TL: total length of optical system OL BLDF: Length of focusing group GF on the optical axis

[0016] Condition (2) defines an appropriate relationship between the axial length of the focusing group GF and the overall length of the optical system OL. By satisfying condition (2), the focusing group can be made lighter, enabling high-speed focusing.

[0017] If the corresponding value of conditional expression (2) falls outside the above range, it becomes difficult to suppress the weight of the focusing group. By setting the lower limit of conditional expression (2) to 0.015, 0.020, 0.023, 0.025, 0.028, 0.030, 0.033, or even 0.035, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (2) to 0.150, 0.130, 0.110, 0.080, 0.060, or even 0.050, the effect of this embodiment can be made more certain.

[0018] Next, an optical system according to a second embodiment will be described. As shown in FIG. 1, an optical system OL(1) as an example of an optical system (photographing lens) OL according to the second embodiment is composed of a leading lens group GA having negative refractive power and a trailing lens group GB having positive refractive power, which are arranged in order from the object side along the optical axis. The trailing lens group GB has a focusing group GF having positive refractive power, which is arranged closest to the object side of the trailing lens group GB, and an image side group GC, which is arranged on the image side of the focusing group GF. When focusing from an object at infinity to an object at a close distance, the focusing group GF moves toward the image side along the optical axis.

[0019] With the above-mentioned configuration, the optical system OL according to the second embodiment satisfies the following conditional expression (3). 1.00<βB / βC<10.00 (3) where βB is the magnification of the subsequent lens group GB when focusing on an object at infinity. βC: Magnification of the image-side group GC when focusing on an object at infinity

[0020] According to the second embodiment, it is possible to obtain an optical system with little fluctuation in the angle of view during focusing, and an optical device including this optical system. The optical system OL according to the second embodiment may be the optical system OL(2) shown in Fig. 3 or the optical system OL(3) shown in Fig. 5.

[0021] Condition (3) defines an appropriate relationship between the magnification of the rear lens group GB when focusing on an object at infinity and the magnification of the image-side lens group GC when focusing on an object at infinity. By satisfying condition (3), it is possible to reduce fluctuations in the angle of view when focusing.

[0022] If the corresponding value of conditional expression (3) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (3) to 1.40, 1.80, 2.20, 2.50, or even 2.60, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (3) to 8.00, 7.50, 7.00, 6.50, 6.00, 5.50, 5.00, or even 4.50, the effect of this embodiment can be made more certain.

[0023] It is desirable that the optical system OL according to the second embodiment satisfies the above-mentioned conditional expression (2). By satisfying the conditional expression (2), high-speed focusing can be performed as in the first embodiment. By setting the lower limit of the conditional expression (2) to 0.015, 0.020, 0.023, 0.025, 0.028, 0.030, 0.033, or even 0.035, the effect of this embodiment can be made more certain. In addition, by setting the upper limit of the conditional expression (2) to 0.150, 0.130, 0.110, 0.080, 0.060, or even 0.050, the effect of this embodiment can be made more certain.

[0024] The optical system OL according to the second embodiment may satisfy the above-mentioned conditional expression (1). By satisfying conditional expression (1), it is possible to reduce the variation in the angle of view during focusing, as in the first embodiment. By setting the lower limit of conditional expression (1) to 0.79, 0.80, 0.81, 0.82, or even 0.83, it is possible to ensure the effect of the second embodiment. Moreover, by setting the upper limit of conditional expression (1) to 0.98, 0.96, 0.95, or even 0.94, it is possible to ensure the effect of the second embodiment.

[0025] Moreover, the optical system OL according to the first embodiment may satisfy the above-mentioned conditional expression (3). By satisfying conditional expression (3), it is possible to reduce the fluctuation of the angle of view during focusing, as in the second embodiment. By setting the lower limit of conditional expression (3) to 1.40, 1.80, 2.20, 2.50, or even 2.60, it is possible to further ensure the effect of the first embodiment. By setting the upper limit of conditional expression (3) to 8.00, 7.50, 7.00, 6.50, 6.00, 5.50, 5.00, or even 4.50, it is possible to further ensure the effect of the first embodiment.

[0026] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following conditional expression (4). 0.50<(-fA) / f<1.50 (4) where fA is the focal length of the leading lens group GA f: focal length of optical system OL when focusing on an object at infinity

[0027] Condition (4) defines an appropriate relationship between the focal length of the leading lens group GA and the focal length of the optical system OL when focusing on an object at infinity. By satisfying condition (4), various aberrations such as field curvature can be effectively corrected.

[0028] If the corresponding value of conditional expression (4) falls outside the above range, it becomes difficult to correct various aberrations such as curvature of field. By setting the lower limit of conditional expression (4) to 0.60, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, or even 0.98, the effects of each embodiment can be more reliably achieved. Also, by setting the upper limit of conditional expression (4) to 1.45, 1.40, 1.35, 1.30, 1.25, 1.20, 1.18, or even 1.15, the effects of each embodiment can be more reliably achieved.

[0029] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following conditional expression (5). -3.00<(rL1R2+rL1R1) / (rL1R2-rL1R1)<0.00 ···(5) where rL1R1 is the radius of curvature of the lens surface on the object side of the lens arranged closest to the object side in the optical system OL. rL1R2: Radius of curvature of the image-side lens surface of the lens located closest to the object in the optical system OL

[0030] Condition (5) defines an appropriate shape factor for the lens located closest to the object in the optical system OL. By satisfying condition (5), coma and curvature of field can be effectively corrected.

[0031] If the corresponding value of conditional expression (5) falls outside the above range, it becomes difficult to correct coma aberration and curvature of field. By setting the lower limit of conditional expression (5) to -2.70, -2.50, -2.30, -2.00, -1.80, or -1.70, the effects of each embodiment can be more certain. Also, by setting the upper limit of conditional expression (5) to -0.40, -0.60, -0.80, -1.00, -1.20, or -1.30, the effects of each embodiment can be more certain.

[0032] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following conditional expression (6). -5.00<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-2.00 ···(6) where rL2R1 is the radius of curvature of the object-side lens surface of the second lens in the optical system OL, counting from the object side. rL2R2: Radius of curvature of the image-side lens surface of the second lens located from the object side of the optical system OL

[0033] Conditional formula (6) defines an appropriate shape factor for the second lens element from the object side of the optical system OL. By satisfying conditional formula (6), coma and curvature of field can be effectively corrected.

[0034] If the corresponding value of conditional expression (6) falls outside the above range, it becomes difficult to correct coma aberration and curvature of field. By setting the lower limit of conditional expression (6) to -4.80, -4.60, -4.50, -4.40, or further to -4.30, the effects of each embodiment can be more reliably achieved. Also, by setting the upper limit of conditional expression (6) to -2.20, -2.40, -2.50, -2.60, -2.70, or further to -2.80, the effects of each embodiment can be more reliably achieved.

[0035] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following conditional expression (7). 60.00°<2ω<130.00° ···(7) However, 2ω: the total angle of view of the optical system OL when focusing on an object at infinity

[0036] Conditional expression (7) defines an appropriate range of the total angle of view of the optical system OL when focusing on an object at infinity. By satisfying conditional expression (7), an optical system with a wide angle of view can be obtained, which is preferable. By setting the lower limit of conditional expression (7) to 64.00°, 68.00°, 72.00°, 76.00°, or even 80.00°, the effects of each embodiment can be made more certain. In addition, by setting the upper limit of conditional expression (7) to 125.00°, 120.00°, 115.00°, 110.00°, or even 105.00°, the effects of each embodiment can be made more certain.

[0037] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following conditional expression (8). 1.20 <FNO<3.00 ···(8) However, FNO: F-number of the optical system OL when focusing on an object at infinity

[0038] Conditional formula (8) defines an appropriate range of the F-number of the optical system OL when focusing on an object at infinity. Satisfying conditional formula (8) is preferable because it provides a bright optical system. Setting the lower limit of conditional formula (8) to 1.25, 1.30, 1.40, 1.50, 1.60, 1.70, or even 1.75 can ensure the effects of each embodiment. Setting the upper limit of conditional formula (8) to 2.80, 2.65, 2.50, 2.40, 2.30, or even 2.20 can ensure the effects of each embodiment.

[0039] In the optical systems OL according to the first and second embodiments, it is desirable that an aperture stop S is disposed in the subsequent lens group GB and that the following conditional expression (9) is satisfied. 0.35 <STL / TL<0.70 ···(9) However, STL: The distance on the optical axis from the aperture stop S to the image plane I when focusing on an object at infinity TL: Total length of optical system OL

[0040] Condition (9) prescribes an appropriate position for the aperture stop S. By satisfying condition (9), the amount of peripheral light can be ensured.

[0041] If the value of conditional expression (9) falls outside the above range, it becomes difficult to ensure the amount of peripheral light. By setting the lower limit of conditional expression (9) to 0.38, 0.40, 0.42, 0.45, or even 0.48, the effects of each embodiment can be more reliably achieved. Also, by setting the upper limit of conditional expression (9) to 0.68, 0.65, 0.63, 0.60, 0.58, or even 0.57, the effects of each embodiment can be more reliably achieved.

[0042] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following condition (10). 0.05 <Bf / TL<0.30 ···(10) where Bf is the back focus of the optical system OL. TL: Total length of optical system OL

[0043] Condition (10) defines an appropriate relationship between the back focal length of the optical system OL and the overall length of the optical system OL. By satisfying condition (10), various aberrations such as field curvature and distortion can be effectively corrected.

[0044] If the corresponding value of conditional expression (10) falls outside the above range, it becomes difficult to correct various aberrations such as curvature of field and distortion. By setting the lower limit of conditional expression (10) to 0.06, 0.07, 0.08, 0.09, or even 0.10, the effects of each embodiment can be made more certain. Also, by setting the upper limit of conditional expression (10) to 0.27, 0.25, 0.23, 0.20, 0.18, 0.16, or even 0.15, the effects of each embodiment can be made more certain.

[0045] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following conditional expression (11). 1.50 <fF / f<4.50 ···(11) where fF is the focal length of the focusing group GF f: focal length of optical system OL when focusing on an object at infinity

[0046] Condition (11) defines an appropriate relationship between the focal length of the focusing group GF and the focal length of the optical system OL when focusing on an object at infinity. By satisfying condition (11), good optical performance can be obtained both when focusing on an object at infinity and when focusing on a close object.

[0047] If the corresponding value of conditional expression (11) falls outside the above range, it becomes difficult to obtain good optical performance both when focusing on an object at infinity and when focusing on an object at close range. By setting the lower limit of conditional expression (11) to 1.60, 1.80, 2.20, 2.30, 2.40, 2.45, 2.50, or even 2.55, the effects of each embodiment can be made more certain. Also, by setting the upper limit of conditional expression (11) to 4.20, 4.00, 3.80, 3.60, 3.50, 3.40, or even 3.30, the effects of each embodiment can be made more certain.

[0048] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following condition (12). 1.00 <fF / fB<3.00 ···(12) where fF is the focal length of the focusing group GF fB: focal length of the subsequent lens group GB when focusing on an object at infinity

[0049] Condition (12) defines an appropriate relationship between the focal length of the focusing group GF and the focal length of the subsequent lens group GB when focusing on an object at infinity. By satisfying condition (12), good optical performance can be obtained both when focusing on an object at infinity and when focusing on a close object.

[0050] If the corresponding value of conditional expression (12) falls outside the above range, it becomes difficult to obtain good optical performance both when focusing on an object at infinity and when focusing on an object at close range. By setting the lower limit of conditional expression (12) to 1.20, 1.30, 1.40, 1.50, 1.55, 1.60, or even 1.65, the effects of each embodiment can be more certain. Also, by setting the upper limit of conditional expression (12) to 2.80, 2.70, 2.60, 2.50, 2.40, 2.35, 2.30, 2.25, 2.20, or even 2.18, the effects of each embodiment can be more certain.

[0051] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following condition (13). 0.15 <dF / TL<0.40 ···(13) where dF is the distance on the optical axis from the lens surface of the optical system OL closest to the object to the lens surface of the focusing group GF closest to the object when focusing on an object at infinity. TL: Total length of optical system OL

[0052] Conditional expression (13) defines an appropriate range of the distance on the optical axis from the lens surface closest to the object in the optical system OL to the lens surface closest to the object in the focusing group GF. By satisfying conditional expression (13), the focusing group GF is preferably disposed toward the object side in the optical system OL. By setting the lower limit of conditional expression (13) to 0.18, 0.20, 0.22, or even 0.23, the effects of each embodiment can be made more certain. Furthermore, by setting the upper limit of conditional expression (13) to 0.38, 0.35, 0.33, or even 0.30, the effects of each embodiment can be made more certain.

[0053] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following condition (14). 0.00<1 / βF<0.60 (14) where βF is the magnification of the focusing group GF when focusing on an object at infinity.

[0054] Condition (14) defines an appropriate range for the magnification of the focusing group GF when focusing on an object at infinity. By satisfying condition (14), fluctuations in the angle of view when focusing can be reduced.

[0055] If the corresponding value of conditional expression (14) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the lower limit of conditional expression (14) to 0.04, 0.05, 0.08, 0.10, 0.13, 0.15, 0.18, 0.20, or even 0.22, the effects of each embodiment can be more reliably achieved. Also, by setting the upper limit of conditional expression (14) to 0.55, 0.53, 0.50, 0.48, 0.45, 0.42, 0.40, 0.38, or even 0.36, the effects of each embodiment can be more reliably achieved.

[0056] It is desirable for the optical system OL according to the first and second embodiments to satisfy the following condition (15). {βF+(1 / βF)} -2 <0.18 ···(15) where βF is the magnification of the focusing group GF when focusing on an object at infinity.

[0057] Condition (15) defines an appropriate range for the magnification of the focusing group GF when focusing on an object at infinity. By satisfying condition (15), fluctuations in the angle of view when focusing can be reduced.

[0058] If the value of conditional expression (15) falls outside the above range, it becomes difficult to suppress fluctuations in the angle of view during focusing. By setting the upper limit of conditional expression (15) to 0.16, 0.15, 0.14, 0.13, 0.12, or even 0.11, the effects of each embodiment can be more reliably achieved.

[0059] Next, with reference to FIG. 8, a manufacturing method of the optical system OL according to the first and second embodiments will be outlined. First, a leading lens group GA having a negative refractive power and a trailing lens group GB having a positive refractive power are arranged in order from the object side along the optical axis (step ST1). Next, a focusing group GF having a positive refractive power is arranged on the most object side of the trailing lens group GB, and an image side group GC is arranged on the image side of the focusing group GF of the trailing lens group GB (step ST2). Next, the focusing group GF is configured to move toward the image side along the optical axis when focusing from an infinite object to a close object (step ST3). Then, in the case of the optical system OL according to the first embodiment, each lens is arranged in the lens barrel so as to satisfy at least the above conditional formula (1) (step ST4). In the case of the optical system OL according to the second embodiment, each lens is arranged in the lens barrel so as to satisfy at least the above conditional formula (3) (step ST4). According to such a manufacturing method, it is possible to manufacture an optical system with little fluctuation in the angle of view during focusing. EXAMPLES

[0060] Hereinafter, optical systems OL according to examples of each embodiment will be described with reference to the drawings. Figures 1, 3, and 5 are cross-sectional views showing the configuration and refractive power distribution of optical systems OL {OL(1) to OL(3)} according to first to third examples. In the cross-sectional views of the optical systems OL(1) to OL(3) according to first to third examples, the arrows indicate the movement direction of each lens group along the optical axis when focusing from infinity to a close-distance object.

[0061] 1, 3, and 5, each lens group and each 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 symbols and numbers from becoming too large and becoming complicated in number, the lens groups, etc. are represented by different combinations of symbols and numbers for each embodiment. Therefore, even if the same combinations of symbols and numbers are used between embodiments, this does not mean that they have the same configuration.

[0062] Tables 1 to 3 are shown below, with Table 1 showing data on various elements in Example 1, Table 2 showing data on various elements in Example 2, and Table 3 showing data on various elements in Example 3. In each example, the d-line (wavelength λ=587.6 nm) and g-line (wavelength λ=435.8 nm) are selected as the targets for calculating the aberration characteristics.

[0063] In the [Overall Specifications] table, f is the focal length of the entire lens system, FNO is the F-number, 2ω is the angle of view (units are ° (degrees), where ω is half the angle of view), and Y is the image height. TL is the distance from the frontmost lens surface to the final lens surface on the optical axis when focusing on infinity plus BF, and BF is the distance from the final lens surface on the optical axis to image plane I when focusing on infinity (back focus). Also, in the [Overall Specifications] table, fA is the focal length of the leading lens group. fB is the focal length of the trailing lens group when focusing on an object at infinity. fC is the focal length of the image-side group when focusing on an object at infinity. fF is the focal length of the focusing group. βB is the magnification of the trailing lens group when focusing on an object at infinity. βC is the magnification of the image-side group when focusing on an object at infinity. βF is the magnification of the focusing group when focusing on an object at infinity.

[0064] In the [Lens specifications] table, the surface number indicates the order of the optical surfaces from the object side along the direction of light travel, R is the radius of curvature of each optical surface (surfaces whose center of curvature is located on the image side are given a positive value), D is the surface spacing which is the distance on the optical axis from each optical surface to the next optical surface (or image surface), nd is the refractive index of the material of the optical component with respect to the d-line, and νd is the Abbe number based on the d-line of the material of the optical component. The "∞" in the radius of curvature indicates a plane or an aperture, and (stop S) indicates the aperture stop S. The refractive index of air, nd=1.00000, has been omitted. If the optical surface is aspheric, an * is added to the surface number, and the paraxial radius of curvature is shown in the column for radius of curvature R.

[0065] In the [Aspherical Data] table, the shape of the aspherical surface shown in [Lens Specifications] is shown by the following formula (A). X(y) is the distance (sag amount) along the optical axis direction from the tangent plane at the apex of the aspherical surface to the position on the aspherical surface at height y, R is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and Ai is the ith aspherical coefficient. "En" is the ratio of "×10 -n For example, 1.234E-05=1.234×10 -5 In addition, the second-order aspheric coefficient A2 is 0, and is omitted.

[0066] X(y)=(y 2 / R) / {1+(1-κ×y 2 / R 2 ) 1 / 2}+A4×y 4 +A6×y 6 +A8×y 8 +A10×y 10 +A12×y 12 …(A)

[0067] The [Variable Distance Data] table shows the surface spacing for surface number i, which has a surface spacing of (Di) in the [Lens Specifications] table. In the [Variable Distance Data] table, f indicates the focal length of the entire lens system, and β indicates the shooting magnification.

[0068] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0069] In the following, for all specifications, the focal length f, radius of curvature R, surface separation D, and other lengths are generally in "mm" unless otherwise specified; however, this is not limited to this because the optical system can provide the same optical performance even when proportionally enlarged or reduced.

[0070] The above explanation of the tables is common to all the embodiments, and therefore, duplicate explanations will be omitted below.

[0071] (First embodiment) The first embodiment will be described with reference to FIGS. 1 to 2 and Table 1. FIG. 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 is composed of a first lens group G1 having negative refractive power, a second lens group G2 having positive 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, which are 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 moves toward the image side along the optical axis, and the fourth lens group G4 moves toward the object side along the optical axis, and the interval between the adjacent lens groups changes. During focusing, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image surface I. An aperture stop S is disposed in the third lens group G3. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of the lens group, and this is the same in all the following embodiments.

[0072] The first lens group G1 is composed of a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, and a cemented lens of a biconcave negative lens L13 and a positive meniscus lens L14 with a convex surface facing the object side, which are arranged in order from the object side along the optical axis. The negative meniscus lens L12 is a hybrid lens composed of a glass lens body and a resin layer provided on the object side surface. The image side surface of the resin layer is aspheric, and the negative meniscus lens L12 is a composite aspheric lens. In the [Lens Specifications] described later, surface number 3 indicates the object side surface of the lens body, surface number 4 indicates the image side surface of the lens body and the object side surface of the resin layer (the surface where the two are cemented), and surface number 5 indicates the image side surface of the resin layer.

[0073] The second lens group G2 is composed of a biconvex positive lens L21.

[0074] The third lens group G3 is composed of, in order from the object side, a cemented lens of a biconvex positive lens L31 and a biconcave negative lens L32, a biconcave negative lens L33, a biconvex positive lens L34, a cemented lens of a biconvex positive lens L35 and a negative meniscus lens L36 with its concave surface facing the object side, and a biconvex positive lens L37. An aperture stop S is disposed between the negative lens L32 and the negative lens L33 in the third lens group G3.

[0075] The fourth lens group G4 is composed of a negative meniscus lens L41 with its concave surface facing the object side. The negative meniscus lens L41 has aspheric lens surfaces on both sides.

[0076] The fifth lens group G5 is composed of a negative meniscus lens L51 with a concave surface facing the object side. An image surface I is disposed on the image side of the fifth lens group G5. The negative meniscus lens L51 has aspheric lens surfaces on both sides.

[0077] In this embodiment, the first lens group G1 constitutes a leading lens group GA having a negative refractive power as a whole. The second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute a trailing lens group GB having a positive refractive power as a whole. The second lens group G2 constitutes a focusing group GF in the trailing lens group GB, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute an image side group GC in the trailing lens group GB.

[0078] Table 1 below lists the values ​​of the specifications of the optical system according to the first embodiment.

[0079] (Table 1) [Overall specifications] f=19.752 fA=-21.416 FNO=1.850 fB=32.742 2ω=94.000 fC=36.880 Y=21.700 fF=54.915 TL=119.425 βB=-0.922 Bf=13.307 βC=-0.223 βF=4.143 [Lens specifications] Surface number RD nd νd 1 95.9736 2.200 1.69680 55.53 2 22.7534 8.128 3 44.6575 1.550 1.77250 49.62 4 23.5501 0.050 1.51380 52.97 5* 19.5320 10.056 6 -2091.0337 1.600 1.49782 82.57 7 28.5475 5.100 1.95375 32.33 8 62.5330 (D8) 9 49.0421 4.800 1.80400 46.60 10 -423.4257 (D10) 11 62.2274 5.000 1.95375 32.33 12 -31.1515 1.100 1.84666 23.80 13 109.4389 7.476 14 ∞ 4.522 (Aperture S) 15 -21.9847 1.100 1.63980 34.55 16 180.9758 0.200 17 28.8999 6.500 1.49782 82.57 18 -32.6652 0.200 19 40.2245 7.600 1.49782 82.57 20 -21.1001 1.200 1.95375 32.33 21 -133.5276 0.200 22 46.5098 4.369 1.96300 24.11 23 -174.4889 (D23) 24* -114.5192 1.600 1.86100 37.10 25* -200.0000 (D25) 26* -41.2363 2.000 1.86100 37.10 27* -52.6527 Bf [Aspherical Data] The 5th surface κ = 0.0000, A4 = 2.25913E-06, A6 = -1.46119E-09 A8 = -3.65260E-11, A10 = 7.29186E-14, A12 = -0.12250E-15 The 24th surface κ = 1.0000, A4 = -2.36949E-05, A6 = 4.59449E-08 A8 = -2.40149E-10, A10 = 4.37008E-14, A12 = 0.00000E+00 The 25th surface κ = 1.0000, A4 = 1.03885E-05, A6 = -1.05283E-08 A8=2.53730E-10,A10=-2.36282E-12,A12=0.56556E-14 Page 26 κ=1.0000,A4=5.70338E-05,A6=-5.96569E-07 A8=1.49791E-09,A10=-2.21943E-12,A12=0.00000E+00 Page 27 κ=1.0000,A4=6.20655E-05,A6=-5.08156E-07 A8=1.34161E-09,A10=-1.31454E-12,A12=0.00000E+00 [Variable interval data] Focused at infinity Focused at mid-range Focused at close range f=19.7523 β=-0.0324 β=-0.1844 Object distance ∞ 583.6824 81.5339 D8 3.83333 4.66117 8.49234 D10 9.69148 8.86123 5.03506 D23 7.98377 7.83192 7.06806 D25 8.05896 8.21231 8.97413 [Lens group data] Group starting plane focal length G1 1 -21.416 G2 9 54.915 G3 11 33.632 G4 24 -313.917 G5 26 -240.369

[0080] FIG. 2(A) shows various aberration diagrams of the optical system according to the first embodiment when focusing at infinity. FIG. 2(B) shows various aberration diagrams of the optical system according to the first embodiment when focusing at a close distance. In each aberration diagram when focusing at infinity, FNO indicates the F-number, and Y indicates the image height. In each aberration diagram when focusing at a close distance, NA indicates the numerical aperture, and Y indicates the image height. Note that the spherical aberration diagram shows the F-number or numerical aperture value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum value of the image height, and the coma aberration diagram shows the value of each image height. d indicates the d-line (wavelength λ=587.6 nm), and g indicates the g-line (wavelength λ=435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image surface, and the dashed line indicates the meridional image surface. Note that the same symbols as in this embodiment are used in the aberration diagrams of each embodiment shown below, and duplicated explanations are omitted.

[0081] From the various aberration diagrams, it can be seen that the optical system of Example 1 has excellent imaging performance with various aberrations well corrected over the entire range from focusing at infinity to focusing at close distances. Therefore, even when focusing on a close object, it is possible to reduce fluctuations in the angle of view when focusing while maintaining good optical performance.

[0082] (Second Example) The second embodiment will be described with reference to FIGS. 3 to 4 and Table 2. FIG. 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 is composed of a first lens group G1 having negative refractive power, a second lens group G2 having positive 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, which are 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 moves toward the image side along the optical axis, and the fourth lens group G4 moves toward the object side along the optical axis, and the interval between the adjacent lens groups changes. During focusing, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image surface I. An aperture stop S is disposed in the third lens group G3.

[0083] In the second embodiment, the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 are configured in the same manner as in the first embodiment, so the same reference numerals as in the first embodiment are used and detailed description of each of these lenses is omitted. In this embodiment, the first lens group G1 constitutes the leading lens group GA having a negative refractive power as a whole. The second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the trailing lens group GB having a positive refractive power as a whole. The second lens group G2 constitutes the focusing group GF in the trailing lens group GB, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute the image side group GC in the trailing lens group GB.

[0084] Table 2 below lists the values ​​of the specifications of the optical system according to the second embodiment.

[0085] (Table 2) [Overall specifications] f=18.300 fA=-20.673 FNO=2.040 fB=33.525 2ω=100.000 fC=36.254 Y=21.700 fF=56.730 TL=115.432 βB=-0.885 Bf=13.305 βC=-0.228 βF=3.889 [Lens specifications] Surface number RD nd νd 1 90.2277 2.200 1.69680 55.53 2 22.3259 8.564 3 46.5688 1.550 1.77250 49.62 4 22.8095 0.050 1.51380 52.97 5* 18.7517 10.444 6 -695.4342 1.600 1.49782 82.57 7 28.3462 5.100 1.95375 32.33 8 67.1568 (D8) 9 47.3685 4.800 1.80400 46.60 10 -1173.5659 (D10) 11 57.0678 5.000 1.95375 32.33 12 -28.3547 1.100 1.84666 23.80 13 124.7137 6.930 14 ∞ 4.437 (Aperture S) 15 -21.8487 1.100 1.66464 34.18 16 83.7472 0.200 17 26.4652 6.000 1.49782 82.57 18 -34.8619 0.200 19 32.6847 7.800 1.49782 82.57 20 -21.1000 1.200 1.95481 31.10 21 -238.7056 0.200 22 41.9717 4.400 1.96300 24.11 23 -115.3109 (D23) 24* -48.7305 1.600 1.86100 37.10 25* -76.3867 (D25) 26* -50.5083 2.000 1.86100 37.10 27* -52.6316 Bf [Aspherical Data] The 5th surface κ = 0.0000, A4 = 1.73336E-06, A6 = -5.18373E-09 A8 = -6.72613E-12, A10 = -1.17084E-14, A12 = -0.28865E-16 The 24th surface κ = 1.0000, A4 = -2.54179E-05, A6 = 1.75260E-07 A8 = -4.68333E-10, A10 = -2.00453E-12, A12 = 0.00000E+00 The 25th surface κ = 1.0000, A4 = 1.77608E-05, A6 = 9.96131E-08 A8 = 3.73519E-10, A10 = -6.29138E-12, A12 = 0.11757E-13 The 26th surface κ = 1.0000, A4 = 5.28778E-05, A6 = -4.96309E-07 A8 = 9.50586E-10, A10 = -1.55937E-12, A12 = 0.00000E+00 The 27th surface κ = 1.0000, A4 = 5.89841E-05, A6 = -4.03867E-07 A8 = 6.73316E-10, A10 = -1.78482E-13, A12 = 0.00000E+00 [Variable interval data] Infinity focus state, intermediate distance focus state, closest distance focus state f = 18.3000, β = -0.0300, β = -0.1722 Object distance: ∞, 585.1748, 81.2627 D8: 4.34275, 5.13609, 8.85548 D10: 9.47662, 8.68285, 4.96440 D23: 7.13601, 7.03337, 6.49123 D25: 7.52933, 7.63252, 8.17487 [Lens group data] Group, starting surface, focal length G1: 1, -20.673 G2: 9, 56.730 G3: 11, 32.335 G4: 24, -160.622 G5: 26, -2577.184

[0086] Fig. 4(A) is a diagram showing various aberrations of the optical system according to Example 2 when focusing at infinity. Fig. 4(B) is a diagram showing various aberrations of the optical system according to Example 2 when focusing at a close distance. From each diagram showing various aberrations, it can be seen that the optical system according to Example 2 has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing at infinity to focusing at a close distance. Therefore, even when focusing on a close-distance object, it is possible to reduce fluctuations in the angle of view when focusing while maintaining good optical performance.

[0087] (Third Example) The third example will be described with reference to Figs. 5 to 6 and Table 3. Fig. 5 is a diagram showing the lens configuration of the optical system according to the third example of the present embodiment in an infinity focused state. The optical system OL(3) according to the third example is composed of a first lens group G1 having negative refractive power, a second lens group G2 having positive 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, which are arranged in order from the object side along the optical axis. When focusing from an infinite object to a close object, the second lens group G2 moves toward the image side along the optical axis, and the fourth lens group G4 moves toward the object side along the optical axis, and the interval between the adjacent lens groups changes. Note that, when focusing, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed with respect to the image surface I. An aperture stop S is disposed in the third lens group G3.

[0088] The first lens group G1 is composed of a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, and a cemented lens of a negative meniscus lens L13 with a convex surface facing the object side and a positive meniscus lens L14 with a convex surface facing the object side, which are arranged in order from the object side along the optical axis. The negative meniscus lens L12 is a hybrid lens composed of a glass lens body and a resin layer provided on the object side surface. The image side surface of the resin layer is aspheric, and the negative meniscus lens L12 is a composite aspheric lens. In the [Lens Specifications] described later, surface number 3 indicates the object side surface of the lens body, surface number 4 indicates the image side surface of the lens body and the object side surface of the resin layer (the surface where the two are cemented), and surface number 5 indicates the image side surface of the resin layer.

[0089] The second lens group G2 is composed of a biconvex positive lens L21.

[0090] The third lens group G3 is composed of, in order from the object side, a cemented lens of a biconvex positive lens L31 and a biconcave negative lens L32, a biconcave negative lens L33, a biconvex positive lens L34, a cemented lens of a biconvex positive lens L35 and a negative meniscus lens L36 with its concave surface facing the object side, and a biconvex positive lens L37. An aperture stop S is disposed between the negative lens L32 and the negative lens L33 in the third lens group G3.

[0091] The fourth lens group G4 is composed of a biconcave negative meniscus lens L41, both lens surfaces of which are aspheric.

[0092] The fifth lens group G5 is composed of a negative meniscus lens L51 with a concave surface facing the object side. An image surface I is disposed on the image side of the fifth lens group G5. The negative meniscus lens L51 has aspheric lens surfaces on both sides.

[0093] In this embodiment, the first lens group G1 constitutes a leading lens group GA having a negative refractive power as a whole. The second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute a trailing lens group GB having a positive refractive power as a whole. The second lens group G2 constitutes a focusing group GF in the trailing lens group GB, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 constitute an image side group GC in the trailing lens group GB.

[0094] Table 3 below lists the values ​​of the specifications of the optical system according to the third embodiment.

[0095] (Table 3) [Overall specifications] f=23.400 fA=-24.637 FNO=1.850 fB=28.542 2ω=84.000 fC=34.083 Y=21.700 fF=60.973 TL=108.428 βB=-0.950 Bf=14.958 βC=-0.327 βF=2.902 [Lens specifications] Surface number RD nd νd 1 142.4574 1.800 1.65844 50.83 2 21.6000 6.396 3 38.1000 1.550 1.51680 64.13 4 23.6120 0.050 1.51380 52.97 5* 19.2059 6.142 6 63.1783 1.600 1.49782 82.57 7 23.3698 6.266 1.95000 29.37 8 36.0387 (D8) 9 54.5725 3.900 1.80400 46.60 10 -466.6331 (D10) 11 39.5691 5.000 1.95375 32.33 12 -40.6795 1.100 1.84666 23.80 13 54.0179 4.380 14 ∞ 4.408 (Aperture S) 15 -24.1356 1.100 1.62004 36.40 16 75.2494 0.200 17 28.7803 7.300 1.49782 82.57 18 -30.0589 0.200 19 35.1599 8.100 1.49782 82.57 20 -19.4891 1.200 1.95375 32.33 21 -97.0841 0.200 22 53.3925 4.200 1.96300 24.11 23 -93.6556 (D23) 24* -501.9657 1.400 1.86100 37.10 25* 126.9062 (D25) 26* -29.3391 1.600 1.86100 37.10 27* -35.7143 Bf [Aspherical surface] Page 5 κ=0.0000,A4=4.66669E-07,A6=-6.88717E-09 A8=-2.30899E-11,A10=5.43815E-14,A12=-0.19200E-15 Page 24 κ=1.0000,A4=-1.88541E-05,A6=-8.03342E-08 A8=2.03164E-10,A10=1.24201E-12,A12=-0.10143E-13 Page 25 κ=1.0000,A4=6.60646E-06,A6=-1.50187E-07 A8=7.59419E-10,A10=-1.80547E-12,A12=-0.21528E-14 Page 26 κ=1.0000,A4=2.96788E-05,A6=-5.54230E-07 A8=1.09418E-09,A10=8.51720E-13,A12=0.35278E-15 Page 27 κ=1.0000,A4=4.49265E-05,A6=-4.55643E-07 A8=1.16960E-09,A10=1.42886E-12,A12=-0.54944E-14 [Can change the interval データ] Infinity focus stateIntermediate focus state to close focus state f=23.4000 β=-0.0397 β=-0.1410 Object distance ∞ 562.7256 138.9454 D8 3.68884 5.07863 8.66216 D10 6.97027 5.57838 2.00000 D23 7.70512 7.31418 6.15913 D25 7.01357 7.40825 8.56537 [Lens group data] Group starting plane focal length G1 1 -24.637 G2 9 60.973 G3 11 29.756 G4 24 -117.529 G5 26 -215.972

[0096] Fig. 6(A) is a diagram showing various aberrations of the optical system according to Example 3 when focusing at infinity. Fig. 6(B) is a diagram showing various aberrations of the optical system according to Example 3 when focusing at a close distance. From each diagram showing various aberrations, it can be seen that the optical system according to Example 3 has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing at infinity to focusing at a close distance. Therefore, even when focusing on a close object, it is possible to reduce fluctuations in the angle of view when focusing while maintaining good optical performance.

[0097] Next, a table of [Values ​​Corresponding to Conditional Expressions] is shown below. This table shows the values ​​corresponding to each of the conditional expressions (1) to (14) for all the examples (Examples 1 to 3). Condition (1) 0.78 <fB / fC<1.00 Condition (2) 0.010 <BLDF / TL<0.160 Conditional expression (3) 1.00<βB / βC<10.00 Condition (4) 0.50<(-fA) / f<1.50 Conditional expression (5) -3.00<(rL1R2+rL1R1) / (rL1R2-rL1R1)<0.00 Conditional expression (6) -5.00<(rL2R2+rL2R1) / (rL2R2-rL2R1)<-2.00 Conditional expression (7) 60.00°<2ω<130.00° Condition (8) 1.20 <FNO<3.00 Condition (9) 0.35 <STL / TL<0.70 Condition (10) 0.05 <Bf / TL<0.30 Condition (11) 1.50 <fF / f<4.50 Condition (12) 1.00 <fF / fB<3.00 Condition (13) 0.15 <dF / TL<0.40 Conditional expression (14) 0.00<1 / βF<0.60 Conditional expression (15) {βF+(1 / βF)} -2 <0.18

[0098] [Conditional expression corresponding value] Conditional Expression 1st Example 2nd Example 3rd Example (1) 0.888 0.925 0.837 (2) 0.040 0.042 0.036 (3) 4.143 3.889 2.902 (4) 1.084 1.130 1.053 (5) -1.622 -1.658 -1.357 (6) -3.231 -2.920 -4.260 (7) 94.000 100.000 84.000 (8) 1.850 2.040 1.850 (9) 0.493 0.511 0.550 (10) 0.111 0.115 0.138 (11) 2.780 3.100 2.606 (12) 1.677 1.692 2.136 (13) 0.272 0.293 0.254 (14) 0.241 0.257 0.345 (15) 0.052 0.058 0.095

[0099] According to each of the above embodiments, an optical system with little fluctuation in the angle of view during focusing can be realized.

[0100] The above-mentioned embodiments are merely examples of the present invention, and the present invention is not limited to these.

[0101] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the optical system of this embodiment.

[0102] Although a five-group configuration has been shown as an example of the optical system of this embodiment, the present application is not limited to this, and a variable magnification optical system with other group configurations (for example, six groups, etc.) can also be configured. Specifically, a lens or lens group may be added to the most object side or the most image side of the optical system of this embodiment. Note that a lens group refers to a portion having at least one lens separated by an air gap that changes when focusing.

[0103] The lens group or partial lens group may be moved so as to have a component in a direction perpendicular to the optical axis, or may be rotated (rocked) in a plane including the optical axis to serve as an anti-vibration lens group that corrects image blur caused by camera shake.

[0104] The lens surface may be spherical or flat, or aspherical. A spherical or flat lens surface is preferable because it facilitates lens processing and assembly adjustment, and prevents deterioration of optical performance due to errors in processing and assembly adjustment. It is also preferable because there is little deterioration in image quality even if the image plane is shifted.

[0105] When the lens surface is aspheric, the aspheric surface may be any of the following: an aspheric surface formed by grinding, a glass molded aspheric surface formed by molding glass into an aspheric shape, or a composite aspheric surface formed by molding a resin into an aspheric shape on the surface of glass. The lens surface may also be a diffractive surface, or the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0106] It is preferable that the aperture stop is disposed in the third lens group, but it is also possible to use the lens frame to fulfill that role instead of providing a member serving as the aperture stop.

[0107] Each lens surface may be coated with an anti-reflection coating having high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high-contrast optical performance. [Explanation of symbols]

[0108] G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group I Image plane S Aperture stop

Claims

1. the first lens group having negative refractive power and the subsequent lens group having positive refractive power, arranged in order from the object side along the optical axis; the subsequent group includes, in order from the object side along the optical axis, a second lens group having positive refractive power and an image-side group including a plurality of lens groups; During focusing, the second lens group moves, and the interval between the adjacent lens groups changes. An optical system that satisfies the following conditions: 1.00<βB / βC<10.00 however, βB: the magnification of the subsequent lens group when focusing on an object at infinity βC: the magnification of the image side group when focusing on an object at infinity

2. 2. The optical system according to claim 1, which satisfies the following condition: 0.78<fB / fC<1.00 however, fB: the focal length of the subsequent lens group when focusing on an object at infinity fC: focal length of the image side group when focusing on an object at infinity

3. the first lens group having negative refractive power and the subsequent lens group having positive refractive power, arranged in order from the object side along the optical axis; the subsequent group includes, in order from the object side along the optical axis, a second lens group having positive refractive power and an image-side group including a plurality of lens groups; During focusing, the second lens group moves, and the interval between the adjacent lens groups changes. An optical system that satisfies the following conditions: 0.78<fB / fC<1.00 however, fB: the focal length of the subsequent lens group when focusing on an object at infinity fC: focal length of the image side group when focusing on an object at infinity

4. 4. The optical system according to claim 1, wherein the subsequent group includes a lens group having negative refractive power that is arranged closest to the image side of the subsequent group.

5. 5. The optical system according to claim 1, comprising, arranged in order from the object side along the optical axis, the first lens group, the second lens group, a third lens group having positive refractive power, a fourth lens group having negative refractive power and moving during focusing, and a fifth lens group having negative refractive power.

6. 6. The optical system according to claim 1, which satisfies the following condition: 0.010<BLDF / TL<0.160 however, TL: total length of the optical system BLDF: The length of the second lens group on the optical axis

7. 7. The optical system according to claim 1, which satisfies the following condition: 0.50<(-fA) / f<1.50 however, fA: focal length of the first lens group f: focal length of the optical system when focused on an object at infinity

8. 8. The optical system according to claim 1, which satisfies the following condition: -3.00<(rL1R2+rL1R1) / (rL1R2-rL1R1) <0.00 however, rL1R1: the radius of curvature of the object-side lens surface of the lens arranged closest to the object side of the optical system rL1R2: Radius of curvature of the image-side lens surface of the lens arranged closest to the object side in the optical system

9. 9. The optical system according to claim 1, which satisfies the following condition: -5.00<(rL2R2+rL2R1) / (rL2R2-rL2R1) <-2.00 however, rL2R1: the radius of curvature of the object-side lens surface of the second lens located from the object side of the optical system rL2R2: the radius of curvature of the image-side lens surface of the second lens located from the object side of the optical system

10. 10. The optical system according to claim 1, which satisfies the following condition: 60.00°<2ω<130.00° however, 2ω: full angle of view of the optical system when focused on an object at infinity

11. 11. The optical system according to claim 1, which satisfies the following condition: 1.20<FNO<3.00 however, FNO: F-number of the optical system when focused on an object at infinity

12. an aperture stop is disposed in the subsequent lens group; 12. The optical system according to claim 1, which satisfies the following condition: 0.35<STL / TL<0.70 however, STL: Distance on the optical axis from the aperture stop to the image plane when focusing on an object at infinity TL: total length of the optical system

13. 13. The optical system according to claim 1, which satisfies the following condition: 0.05<Bf / TL<0.30 however, Bf: back focus of the optical system TL: total length of the optical system

14. 14. The optical system according to claim 1, which satisfies the following condition: 1.50<fF / f<4.50 however, fF: focal length of the second lens group f: focal length of the optical system when focused on an object at infinity

15. 15. The optical system according to claim 1, which satisfies the following condition: 1.00<fF / fB<3.00 however, fF: focal length of the second lens group fB: the focal length of the subsequent lens group when focusing on an object at infinity

16. 16. The optical system according to claim 1, which satisfies the following condition: 0.15<dF / TL<0.40 however, dF: the distance on the optical axis from the lens surface of the optical system closest to the object to the lens surface of the second lens group closest to the object when focusing on an object at infinity TL: total length of the optical system

17. 17. The optical system according to claim 1, which satisfies the following condition: 0.00<1 / βF<0.60 however, βF: the magnification of the second lens group when focusing on an object at infinity

18. 18. The optical system according to claim 1, which satisfies the following condition: {βF+(1 / βF)}-2<0.18 however, βF: the magnification of the second lens group when focusing on an object at infinity

19. An optical instrument comprising the optical system according to any one of claims 1 to 18.

Images