Optical system and optical device

Abstract

To provide an optical system which offers reduced variation in view angle while focusing.SOLUTION: An optical system OL disclosed herein consists of a front group GA, aperture stop S, and rear group GB arranged in order from an object side along an optical axis, the rear group GB having a focusing lens group GF1 with negative refractive power located on the most object side in the rear group GB and configured to move along the optical axis while focusing, changing distances between adjacent lens groups. The optical system satisfies the following conditional expression: 0.50<ST / TL<0.95, where ST represents an optical axial distance from the aperture stop S to an image plane I, and TL represents the total length of the optical system OL.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 2011-197471 A Summary of the Invention

[0004] The optical system according to the present invention comprises, arranged in order from the object side along the optical axis, a front group, a stop, and a rear group, the rear group having a focusing lens group having negative refractive power that is arranged closest to the object side of the rear group, and during focusing, the focusing lens group moves along the optical axis, changing the spacing between adjacent lens groups, and satisfying the following conditional expressions: 0.50 <ST / TL<0.95 Where ST: distance on the optical axis from the stop to the image plane TL: Total length of the optical system

[0005] An optical device according to the present invention includes the above optical system. [Brief description of the drawings]

[0006] [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. 13 is a diagram showing a lens configuration of an optical system according to a fourth example. [Figure 8] 8A and 8B are diagrams showing various aberrations in the optical system according to Example 4 when focused on infinity and when focused on a close distance, respectively. [Figure 9] FIG. 13 is a diagram showing a lens configuration of an optical system according to a fifth example. [Figure 10] 10A and 10B are diagrams showing various aberrations in the optical system according to Example 5 when focused on infinity and when focused on a close distance, respectively. [Figure 11] FIG. 13 is a diagram showing a lens configuration of an optical system according to Example 6. [Figure 12] 12A and 12B are diagrams showing various aberrations in the optical system according to Example 6 when focused on infinity and when focused on a close distance, respectively. [Figure 13] FIG. 13 is a diagram showing a lens configuration of an optical system according to Example 7. [Figure 14] 14A and 14B are diagrams showing various aberrations in the optical system according to Example 7 when focused on infinity and when focused on a close distance, respectively. [Figure 15] FIG. 13 is a diagram showing a lens configuration of an optical system according to an eighth example. [Figure 16] 16A and 16B are diagrams showing various aberrations in the optical system according to Example 8 when focused on infinity and when focused on a close distance, respectively. [Figure 17] FIG. 1 is a diagram showing a configuration of a camera equipped with an optical system according to an embodiment of the present invention. [Figure 18] 5 is a flowchart showing a method of manufacturing the optical system according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] A preferred embodiment of the present invention will be described below. First, a camera (optical device) equipped with the optical system according to this embodiment will be described with reference to FIG. 17. As shown in FIG. 17, 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.

[0008] 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. The optical system OL shown in FIG. 17 is a schematic diagram of an optical system provided in the photographing lens 3, and the lens configuration of the optical system OL is not limited to this configuration.

[0009] Next, the optical system according to this embodiment will be described. As shown in Fig. 1, an optical system OL(1) as an example of the optical system (photographing lens) OL according to this embodiment is composed of a front group GA, a diaphragm (aperture stop) S, and a rear group GB, which are arranged in order from the object side along the optical axis. The rear group GB is composed of a focusing lens group (GF1) having negative refractive power that is arranged closest to the object side of the rear group GB. During focusing, the focusing lens group moves along the optical axis, and the interval between adjacent lens groups changes.

[0010] With the above-mentioned configuration, the optical system OL according to this embodiment satisfies the following conditional expression (1). 0.50 <ST / TL<0.95 ···(1) Where ST is the distance on the optical axis from aperture S to image plane I TL: Total length of optical system OL

[0011] According to this 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 this embodiment may be the optical system OL(2) shown in Fig. 3, the optical system OL(3) shown in Fig. 5, the optical system OL(4) shown in Fig. 7, or the optical system OL(5) shown in Fig. 9. In addition, the optical system OL according to this embodiment may be the optical system OL(6) shown in Fig. 11, the optical system OL(7) shown in Fig. 13, or the optical system OL(8) shown in Fig. 15.

[0012] Conditional formula (1) defines an appropriate relationship between the distance on the optical axis from the aperture stop S to the image plane I and the overall length of the optical system OL. By satisfying conditional formula (1), it is possible to reduce fluctuations in the angle of view when focusing.

[0013] 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 0.53, 0.55, 0.58, 0.60, 0.63, or even 0.65, the effect of this embodiment can be made more certain. In addition, by setting the upper limit of conditional expression (1) to 0.93, 0.90, 0.88, or 0.85, , 0.83, 0.80, or even 0.78, the effect of this embodiment can be made more certain.

[0014] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (2). 0.65<(-fF) / fA<1.20 (2) where fF is the focal length of the focusing lens group. fA: Focal length of the front group GA

[0015] Condition (2) defines an appropriate relationship between the focal length of the focusing lens group and the focal length of the front group GA. By satisfying condition (2), fluctuations in the angle of view during focusing can be reduced.

[0016] If the corresponding value of conditional expression (2) 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 (2) to 0.68, 0.70, 0.73, 0.75, or even 0.77, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (2) to 1.18, 1.15, 1.13, 1.00, or even 1.09, the effect of this embodiment can be made more certain.

[0017] In the optical system OL according to this embodiment, it is desirable that the rear group GB has at least one lens group arranged closer to the image plane side than the focusing lens group, and that the following conditional expression (3) be satisfied. 0.70<(-fF) / fR<1.80 (3) where fF is the focal length of the focusing lens group. fR: composite focal length of the at least one lens group

[0018] Conditional formula (3) specifies an appropriate relationship between the focal length of the focusing lens group and the composite focal length of at least one lens group arranged closer to the image plane than the focusing lens group. The composite focal length of the at least one lens group is the composite focal length when focusing on an object at infinity. When there is only one lens group, the composite focal length of the at least one lens group is the focal length of that one lens group, and when there are multiple lens groups, the composite focal length of the multiple lens groups. By satisfying conditional formula (3), it is possible to reduce fluctuations in the angle of view when focusing.

[0019] If the 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 0.73, 0.75, 0.78, 0.80, or even 0.83, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (3) to 1.78, 1.75, 1.73, 1.70, 1.68, 1.65, or even 1.63, the effect of this embodiment can be made more certain.

[0020] In the optical system OL according to this embodiment, the rear group GB has a subsequent lens group GR1 arranged adjacent to the focusing lens group on the image plane side, and it is desirable that the following conditional expression (4) be satisfied. 0.00<βR1 / βF<0.25 (4) where βR1 is the lateral magnification of the subsequent lens group GR1 when focusing on an object at infinity. βF: Lateral magnification of the focusing lens group when focusing on an object at infinity

[0021] Condition (4) defines an appropriate relationship between the lateral magnification of the rear lens group GR1 when focusing on an object at infinity and the lateral magnification of the focusing lens group when focusing on an object at infinity. By satisfying condition (4), it is possible to reduce fluctuations in image magnification during focusing.

[0022] If the value of conditional expression (4) falls outside the above range, it becomes difficult to suppress the variation in image magnification during focusing. By setting the lower limit of conditional expression (4) to 0.01, the effect of this embodiment can be more certain. Also, by setting the upper limit of conditional expression (4) to 0.23, 0.20, 0.18, 0.16, or even 0.15, the effect of this embodiment can be more certain.

[0023] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (5). 0.03<Δx / f<0.35 (5) where Δx is the amount of movement of the focusing lens group when focusing from an object at infinity to an object at a close distance f: focal length of optical system OL

[0024] Conditional expression (5) defines an appropriate relationship between the amount of movement of the focusing lens group during focusing and the focal length of the optical system OL. By satisfying conditional expression (5), it is possible to satisfactorily correct field curvature, spherical aberration, coma aberration, and the like. In this embodiment, the sign of the amount of movement of the focusing lens group toward the image side is set to +, and the sign of the amount of movement toward the object side is set to -.

[0025] If the corresponding value of conditional expression (5) falls outside the above range, it becomes difficult to correct curvature of field, spherical aberration, coma aberration, etc. By setting the lower limit of conditional expression (5) to 0.04, 0.06, or further to 0.08, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (5) to 0.33, 0.30, 0.28, 0.25, 0.23, 0.20, or further to 0.18, the effect of this embodiment can be made more certain.

[0026] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (6). 0.65 <f / (-fF)<1.60 ···(6) where f is the focal length of the optical system OL fF: focal length of the focusing lens group

[0027] Condition (6) defines an appropriate relationship between the focal length of the optical system OL and the focal length of the focusing lens group. By satisfying condition (6), chromatic aberration, curvature of field, etc. can be effectively corrected.

[0028] If the value corresponding to conditional expression (6) falls outside the above range, it becomes difficult to correct chromatic aberration, curvature of field, etc. By setting the lower limit of conditional expression (6) to 0.68, 0.70, or further to 0.73, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (6) to 1.58, 1.55, 1.53, 1.50, 1.48, 1.45, 1.43, or further to 1.40, the effect of this embodiment can be made more certain.

[0029] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (7). 2.00 <TL / (FNO×Bf)<10.00 ···(7) However, FNO: F-number of optical system OL Bf: Back focus of optical system OL

[0030] Conditional expression (7) specifies the appropriate relationship between the overall length of the optical system OL and the F-number and back focus of the optical system OL. By satisfying conditional expression (7), it is possible to provide an optical system with a large aperture and a short back focus, with sufficient peripheral light amount secured. Note that the back focus of the optical system OL in conditional expression (7) and conditional expression (14) described later indicates the distance on the optical axis (air-equivalent distance) from the image-side lens surface of the lens arranged closest to the image surface of the optical system OL to the image surface I.

[0031] If the value of conditional expression (7) falls outside the above range, it becomes difficult to ensure a sufficient amount of light around the periphery of the angle of view. By setting the lower limit of conditional expression (7) to 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, or even 2.43, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (7) to 9.85, 9.65, 9.60, 9.55, 9.50, 9.45, or even 9.40, the effect of this embodiment can be made more certain.

[0032] In the optical system OL according to this embodiment, it is preferable that the focusing lens group is composed of one negative lens component. This makes the focusing lens group lightweight, making it possible to focus from an object at infinity to an object at a close distance at high speed. In this embodiment, the lens component refers to a single lens or a cemented lens.

[0033] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (8). -2.50<(rFR2+rFR1) / (rFR2-rFR1)<-0.25 (8) where rFR1 is the radius of curvature of the lens surface closest to the object in the focusing lens group. rFR2: Radius of curvature of the lens surface closest to the image plane in the focusing lens group

[0034] Condition (8) defines an appropriate range for the shape factor of the lenses that make up the focusing lens group. By satisfying condition (8), spherical aberration, coma, and other aberrations can be effectively corrected.

[0035] If the value corresponding to conditional expression (8) falls outside the above range, it becomes difficult to correct spherical aberration, coma aberration, etc. By setting the lower limit of conditional expression (8) to -2.45, -2.40, -2.35, -2.30, -2.25, or further to -2.23, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (8) to -0.30, -0.33, -0.35, -0.38, -0.40, -0.43, -0.45, -0.48, or further to -0.50, the effect of this embodiment can be made more certain.

[0036] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (9). 0.90<(rNR2+rNR1) / (rNR2-rNR1)<2.65 (9) where rNR1 is the radius of curvature of the object-side lens surface of the lens located closest to the image plane in the optical system OL. rNR2: Radius of curvature of the lens surface closest to the image plane in the optical system OL

[0037] Condition (9) defines an appropriate range for the shape factor of the lens located closest to the image plane in the optical system OL. By satisfying condition (9), spherical aberration and distortion can be effectively corrected.

[0038] If the value of conditional expression (9) falls outside the above range, it becomes difficult to correct spherical aberration and distortion. By setting the lower limit of conditional expression (9) to 0.93, 0.95, 0.98, 1.00, or even 1.02, the effect of this embodiment can be made more certain. By setting the upper limit of conditional expression (9) to 2.60, 2.58, 2.55, 2.53, 2.50, 2.48, or even 2.45, the effect of this embodiment can be made more certain.

[0039] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (10). 0.08<1 / βF<0.55 (10) where βF is the lateral magnification of the focusing lens group when focusing on an object at infinity

[0040] Condition (10) defines an appropriate range for the lateral magnification of the focusing lens group when focusing on an object at infinity. By satisfying condition (10), various aberrations such as spherical aberration and curvature of field can be effectively corrected when focusing on an object at infinity.

[0041] If the value of conditional expression (10) falls outside the above range, it becomes difficult to correct various aberrations such as spherical aberration and curvature of field when focusing on an object at infinity. By setting the lower limit of conditional expression (10) to 0.10, 0.12, or even 0.14, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (10) to 0.53, 0.50, 0.48, 0.45, or even 0.43, the effect of this embodiment can be made more certain.

[0042] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (11). {βF+(1 / βF)} -2 <0.15 ···(11) where βF is the lateral magnification of the focusing lens group when focusing on an object at infinity

[0043] Condition (11) defines an appropriate range for the lateral magnification of the focusing lens group when focusing on an object at infinity. By satisfying condition (11), various aberrations such as spherical aberration and curvature of field can be effectively corrected when focusing on an object at infinity.

[0044] If the value of condition (11) falls outside the above range, it becomes difficult to correct various aberrations such as spherical aberration and curvature of field when focusing on an object at infinity. By setting the upper limit of condition (11) to 0.14, or further to 0.13, the effect of this embodiment can be made more certain.

[0045] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (12). 0.003 <BLDF / TL<0.060 ···(12) Where, BLDF: Length of the focusing lens group on the optical axis

[0046] Condition (12) defines an appropriate relationship between the axial length of the focusing lens group and the overall length of the optical system OL. By satisfying condition (12), the focusing lens group can be made lighter and fluctuations in various aberrations during focusing can be suppressed.

[0047] If the corresponding value of conditional expression (12) falls outside the above range, it becomes difficult to correct the fluctuations of various aberrations during focusing. By setting the lower limit of conditional expression (12) to 0.004, 0.006, or even 0.008, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (12) to 0.058, 0.055, 0.053, 0.050, 0.048, 0.045, or even 0.043, the effect of this embodiment can be made more certain.

[0048] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (13). 0.05<βB / βF<0.50 (13) where βB is the lateral magnification of the rear group GB when focusing on an object at infinity. βF: Lateral magnification of the focusing lens group when focusing on an object at infinity

[0049] Condition (13) defines an appropriate relationship between the lateral magnification of the rear group GB when focusing on an object at infinity and the lateral magnification of the focusing lens group when focusing on an object at infinity. By satisfying condition (13), fluctuations in the angle of view when focusing on an object at infinity can be suppressed.

[0050] If the value of conditional expression (13) falls outside the above range, it becomes difficult to suppress the fluctuation of the angle of view when focusing on an object at infinity. By setting the lower limit of conditional expression (13) to 0.06, 0.08, 0.10, or even 0.12, the effect of this embodiment can be made more certain. Also, by setting the upper limit of conditional expression (13) to 0.48, 0.45, 0.43, 0.40, or even 0.38, the effect of this embodiment can be made more certain.

[0051] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (14). 0.05 <Bf / TL<0.25 ···(14) where Bf is the back focus of the optical system OL.

[0052] Condition (14) defines an appropriate relationship between the back focus of the optical system OL and the overall length of the optical system OL. By satisfying condition (14), the back focus can be shortened relative to the overall length of the optical system, which is preferable because it enables the optical system to be made compact.

[0053] If the value of conditional expression (14) falls outside the above range, the back focus becomes long relative to the overall length of the optical system, making it difficult to miniaturize the optical system. By setting the lower limit of conditional expression (14) to 0.06, or further to 0.08, the effect of this embodiment can be made more certain. Furthermore, by setting the upper limit of conditional expression (14) to 0.24, or further to 0.22, the effect of this embodiment can be made more certain.

[0054] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (15). 1.00 <FNO<3.00 ···(15) However, FNO: F-number of optical system OL

[0055] Conditional expression (15) defines an appropriate range for the F-number of the optical system OL. By satisfying conditional expression (15), a bright optical system can be obtained, which is preferable. By setting the lower limit of conditional expression (15) to 1.10, 1.15, or even 1.20, the effect of this embodiment can be made more certain. In addition, by setting the upper limit of conditional expression (15) to 2.85, 2.70, 2.60, 2.50, 2.40, 2.30, 2.20, or even 2.10, the effect of this embodiment can be made more certain.

[0056] It is desirable for the optical system OL according to this embodiment to satisfy the following conditional expression (16). 12.00°<2ω<40.00° ···(16) However, 2ω: full angle of view of optical system OL

[0057] Conditional expression (16) defines an appropriate range for the total angle of view of the optical system OL. By satisfying conditional expression (16), an optical system with a wide angle of view can be obtained, which is preferable. By setting the lower limit of conditional expression (16) to 12.50°, 13.00°, 13.50°, 14.00°, or even 14.50°, the effect of this embodiment can be made more certain. In addition, by setting the upper limit of conditional expression (16) to 38.50°, 37.00°, 36.00°, or even 35.50°, the effect of this embodiment can be made more certain.

[0058] Next, a manufacturing method for the optical system OL according to this embodiment will be outlined with reference to FIG. 18. First, the front group GA, the diaphragm (aperture stop) S, and the rear group GB are arranged in order from the object side along the optical axis (step ST1). Next, a focusing lens group (GF1) having negative refractive power is arranged closest to the object side of the rear group GB (step ST2). Next, the focusing lens group is configured to move along the optical axis during focusing, changing the spacing between adjacent lens groups (step ST3). Then, each lens is arranged in the lens barrel so as to satisfy at least the above conditional formula (1). 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

[0059] Hereinafter, optical systems OL according to examples of this embodiment will be described with reference to the drawings. Figures 1, 3, 5, 7, 9, 11, 13, and 15 are cross-sectional views showing the configurations and refractive power distributions of optical systems OL {OL(1) to OL(8)} according to Examples 1 to 8. In the cross-sectional views of the optical systems OL(1) to OL(8) according to Examples 1 to 8, the movement direction of each focusing lens group along the optical axis when focusing from infinity to a close-distance object is indicated by an arrow together with the word "focusing."

[0060] 1, 3, 5, 7, 9, 11, 13, and 15, each lens group is represented by a combination of the symbol G and a number, and each lens is represented by a combination of the symbol L and a number. In this case, to prevent the symbols and numbers from becoming too large and becoming complicated in number, the lens groups, etc. are represented by their own 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.

[0061] Tables 1 to 8 are shown below, with Table 1 showing data on the various elements in the first embodiment, Table 2 showing data on the second embodiment, Table 3 showing data on the third embodiment, Table 4 showing data on the fourth embodiment, Table 5 showing data on the fifth embodiment, Table 6 showing data on the sixth embodiment, Table 7 showing data on the seventh embodiment, and Table 8 showing data on the eighth embodiment. In each embodiment, 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.

[0062] In the table of [Overall Specifications], f is the focal length of the entire lens system, FNO is the F-number, 2ω is the angle of view (unit: ° (degrees), ω is half angle of view), and Y is the image height. TL is the distance from the front lens surface to the last lens surface on the optical axis when focusing at infinity plus Bf, and Bf is the distance from the last lens surface to the image plane I on the optical axis when focusing at infinity. Bf(a) is the distance on the optical axis from the lens surface on the image plane side of the lens located closest to the image plane in the optical system to the image plane I (air-equivalent distance). In the table of [Overall Specifications], fA is the focal length of the front group. fR is the composite focal length of at least one lens group located closer to the image plane than the focusing lens group closest to the object in the rear group. Δx is the amount of movement of the focusing lens group when focusing from an object at infinity to a close object. βF is the lateral magnification of the focusing lens group when focusing on an object at infinity. βB indicates the lateral magnification of the rear lens group when focusing on an object at infinity. βR1 indicates the lateral magnification of the rear lens group when focusing on an object at infinity.

[0063] 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 have a positive value), D is the surface spacing which is the distance on the optical axis from each optical surface to the next optical surface (or image 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, is omitted.

[0064] 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. Note that D0 indicates the distance from the object to the optical surface closest to the object in the optical system. In the [Variable Distance Data] table, f indicates the focal length of the entire lens system, and β indicates the shooting magnification.

[0065] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0066] 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.

[0067] The above explanation of the tables is common to all the embodiments, and therefore, duplicate explanations will be omitted below.

[0068] (First Example) The first embodiment will be described with reference to FIGS. 1 and 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 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, 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 and the fourth lens group G4 move along the optical axis toward the image side, and the interval between each of 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. 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 embodiments.

[0069] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the aperture stop S is fixed relative to the image surface 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. The second lens group G2 corresponds to the first focusing lens group GF1 arranged closest to the object side of the rear group GB. The third lens group G3 corresponds to the subsequent lens group GR1 arranged adjacent to the image surface side of the first focusing lens group GF1. The fourth lens group G4 corresponds to the second focusing lens group GF2 arranged closer to the image surface side than the first focusing lens group GF1.

[0070] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a positive meniscus lens L12 with a convex surface facing the object side, a cemented lens formed by cementing a positive meniscus lens L13 with a convex surface facing the object side and a negative meniscus lens L14 with a convex surface facing the object side, a negative meniscus lens L15 with a convex surface facing the object side, and a positive meniscus lens L16 with a convex surface facing the object side. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0071] The third lens group G3 is composed of, in order from the object side along the optical axis, a cemented lens formed by cementing together a biconcave negative lens L31 and a biconvex positive lens L32, a biconvex positive lens L33, and a biconvex positive lens L34. The fourth lens group G4 is composed of a biconcave negative lens L41.

[0072] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a biconvex positive lens L51 and a negative meniscus lens L52 with a concave surface facing the object side, and a negative meniscus lens L53 with a concave surface facing the object side. An image surface 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 surface I.

[0073] Table 1 below lists the values ​​of the specifications of the optical system according to the first embodiment.

[0074] (Table 1) [Overall specifications] f=87.000 fA=89.351 FNO=1.424 fR=64.417 2ω=28.285 Δx=12.719 Y=21.600 βF=2.601 TL=129.013 βB=0.974 Bf=1.000 βR1=0.359 Bf(a)=11.168 [Lens specifications] Surface number RD nd νd 1 69.6342 5.430 1.9591 17.47 2 132.1539 0.116 3 55.3642 5.244 2.0010 29.13 4 89.6665 0.100 5 40.4445 8.778 1.5503 75.49 6 140.0000 1.200 1.8548 24.80 7 29.5861 5.360 8 63.3783 1.200 1.9229 20.88 9 31.8132 0.100 10 31.2943 8.078 1.7292 54.67 11 237.3897 2.787 12∞ (D12) (Aperture S) 13 438.3400 1.200 1.5163 64.14 14 38.4472 (D14) 15 -65.9934 1.200 1.7783 23.91 16 39.9168 8.673 1.8040 46.53 17 -723.3882 0.100 18 70.0000 9.587 1.8160 46.62 19 -124.9732 0.100 20 135.5192 4.257 1.9591 17.47 21 -631.3761 (D21) 22 -255.5306 1.200 1.6989 30.13 23 1196.1373 (D23) 24 148.6618 10.553 1.9591 17.47 25 -40.7482 1.000 1.8929 20.36 26 -348.6817 5.247 27 -43.6865 1.200 1.7783 23.91 28 -175.9036 9.113 29 ∞ 1.600 1.5168 63.88 30∞Bf [Variable interval data] Focused at infinity Focused at mid-range Focused at close range f=87.000 β=-0.034 β=-0.126 D0∞ 2570.805 728.956 D12 1.500 4.805 14.219 D14 19.979 16.674 7.260 D21 2.293 4.042 10.530 D23 10.820 9.071 2.583 [Lens group data] Group starting plane focal length G1 1 89.351 G2 13 -81.705 G3 15 54.836 G4 22 -301.138 G5 24 -611.471

[0075] 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.

[0076] 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.

[0077] (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 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, 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 and the fourth lens group G4 move toward the image 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.

[0078] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the aperture stop S is fixed relative to the image surface 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. The second lens group G2 corresponds to the first focusing lens group GF1 arranged closest to the object side of the rear group GB. The third lens group G3 corresponds to the subsequent lens group GR1 arranged adjacent to the image surface side of the first focusing lens group GF1. The fourth lens group G4 corresponds to the second focusing lens group GF2 arranged closer to the image surface side than the first focusing lens group GF1.

[0079] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a positive meniscus lens L12 with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L13 and a biconcave negative lens L14, and a positive meniscus lens L15 with a convex surface facing the object side. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0080] The third lens group G3 is composed of, in order from the object side along the optical axis, a cemented lens formed by cementing together a negative meniscus lens L31 with a convex surface facing the object side and a positive meniscus lens L32 with a convex surface facing the object side, and a biconvex positive lens L33. The fourth lens group G4 is composed of a negative meniscus lens L41 with a convex surface facing the object side.

[0081] The fifth lens group G5 is made up of a positive lens with a convex surface facing the object side, arranged in order from the object side along the optical axis. The fifth lens group G5 is composed of a niscus lens L51 and a negative meniscus lens L52 with a concave surface facing the object side. An image surface 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 surface I.

[0082] Table 2 below lists the values ​​of the specifications of the optical system according to the second embodiment.

[0083] (Table 2) [Overall specifications] f=84.853 fA=83.808 FNO=1.855 fR=70.031 2ω=28.002 Δx=8.031 Y=21.600 βF=4.398 TL=114.050 βB=1.012 Bf=1.000 βR1=0.165 Bf(a)=11.205 [Lens specifications] Surface number RD nd νd 1 57.5903 6.716 1.8081 22.76 2 250.0000 4.134 3 54.4191 3.242 1.7725 49.60 4 87.8376 0.100 5 42.6165 6.392 1.4560 91.37 6 -1029.0613 1.200 2.0007 25.46 7 30.7264 7.020 8 33.1538 7.106 1.4978 82.57 9 2847.8763 2.046 10∞ (D10) (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] Focused at infinity Focused at mid-range Focused at close range f=84.853 β=-0.034 β=-0.120 D0∞ 2544.448 725.082 D10 1.500 3.593 9.531 D12 11.802 9.709 3.771 D17 6.374 7.694 11.374 D19 7.839 6.518 2.839 [Lens group data] Group starting plane focal length G1 1 83.808 G2 11 -66.556 G3 13 40.059 G4 18 -118.979 G5 20 -84.660

[0084] 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.

[0085] (Third Example) The third embodiment 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 embodiment. The optical system OL(3) according to the third embodiment is composed 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, 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 and the fourth lens group G4 move toward the image 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.

[0086] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the aperture stop S is fixed relative to the image surface 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. The second lens group G2 corresponds to the first focusing lens group GF1 arranged closest to the object side of the rear group GB. The third lens group G3 corresponds to the subsequent lens group GR1 arranged adjacent to the image surface side of the first focusing lens group GF1. The fourth lens group G4 corresponds to the second focusing lens group GF2 arranged closer to the image surface side than the first focusing lens group GF1.

[0087] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a positive meniscus lens L12 with a convex surface facing the object side, and a cemented lens formed by cementing a biconvex positive lens L13 and a biconcave negative lens L14. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0088] The third lens group G3 is composed of a biconvex positive lens L31. The fourth lens group G4 is composed of a negative meniscus lens L41 with its convex surface facing the object side.

[0089] The fifth lens group G5 is composed of a positive meniscus lens L51 with a convex surface facing the object side and a negative meniscus lens L52 with a concave surface facing the object side, arranged in order from the object side along the optical axis. An image surface 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 surface I.

[0090] Table 3 below lists the values ​​of the specifications of the optical system according to the third embodiment.

[0091] (Table 3) [Overall specifications] f=82.010 fA=102.479 FNO=2.060 fR=82.146 2ω=28.969 Δx=10.381 Y=21.600 βF=2.495 TL=90.023 βB=0.800 Bf=1.000 βR1=0.202 Bf(a)=17.858 [Lens specifications] Surface number RD nd νd 1 46.5771 5.350 1.7725 49.60 2 179.4303 0.100 3 40.3285 4.836 1.4970 81.61 4 129.0466 0.100 5 33.5684 6.218 1.4560 91.37 6 -229.0734 1.000 1.9004 37.37 7 29.9047 5.182 8∞ (D8) (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] Focused at infinity Focused at mid-range Focused at close range f=82.010 β=-0.032 β=-0.113 D0∞ 2519.887 756.709 D8 1.066 3.911 11.447 D10 17.056 14.211 6.675 D12 1.148 2.146 4.829 D14 6.369 5.372 2.688 [Lens group data] Group starting plane focal length G1 1 102.479 G2 9 -109.666 G3 11 36.793 G4 13 -83.956 G5 15 -101.166

[0092] 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.

[0093] (Fourth Example) The fourth embodiment will be described with reference to FIGS. 7 to 8 and Table 4. FIG. 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 is composed 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, 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 and the fourth lens group G4 move toward the image 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.

[0094] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the aperture stop S is fixed relative to the image surface 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. The second lens group G2 corresponds to the first focusing lens group GF1 arranged closest to the object side of the rear group GB. The third lens group G3 corresponds to the subsequent lens group GR1 arranged adjacent to the image surface side of the first focusing lens group GF1. The fourth lens group G4 corresponds to the second focusing lens group GF2 arranged closer to the image surface side than the first focusing lens group GF1.

[0095] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a cemented lens formed by cementing a positive meniscus lens L12 with a convex surface facing the object side and a negative meniscus lens L13 with a convex surface facing the object side, and a cemented lens formed by cementing a biconvex positive lens L14 and a biconcave negative lens L15. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0096] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L31 with a concave surface facing the object side, a positive meniscus lens L32 with a concave surface facing the object side, and a biconvex positive lens L33. The fourth lens group G4 is composed of a negative meniscus lens L41 with a convex surface facing the object side.

[0097] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L51 with a convex surface facing the object side, a positive meniscus lens L52 with a convex surface facing the object side, and a negative meniscus lens L53 with a concave surface facing the object side. An image surface 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 surface I.

[0098] Table 4 below lists the values ​​of the specifications of the optical system according to the fourth embodiment.

[0099] (Table 4) [Overall specifications] f=84.453 fA=118.522 FNO=1.242 fR=61.307 2ω=28.622 Δx=10.784 Y=21.600 βF=3.780 TL=130.011 βB=0.713 Bf=1.000 βR1=0.153 Bf(a)=11.185 [Lens specifications] Surface number RD nd νd 1 73.2143 10.224 1.8929 20.36 2 453.0360 0.100 3 54.5976 9.054 1.5503 75.49 4 258.6524 1.000 1.7283 28.46 5 39.1638 1.660 6 45.1558 12.609 1.5928 68.62 7 -100.3906 1.000 1.9229 20.88 8 119.0758 4.000 9∞ (D9) (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] Focused at infinity Focused at mid-range Focused at close range f=84.453 β=-0.043 β=-0.087 D0∞ 2018.279 1007.763 D9 2.000 6.974 12.784 D11 21.625 16.651 10.841 D17 2.000 4.186 6.592 D19 9.109 6.923 4.518 [Lens group data] Group starting plane focal length G1 1 118.522 G2 10 -97.991 G3 12 43.900 G4 18 -121.185 G5 20 -251.050

[0100] Fig. 8(A) is a diagram showing various aberrations of the optical system according to Example 4 when focusing at infinity. Fig. 8(B) is a diagram showing various aberrations of the optical system according to Example 4 when focusing at a close distance. From each diagram showing various aberrations, it can be seen that the optical system according to Example 4 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.

[0101] (Fifth Example) The fifth embodiment will be described with reference to FIGS. 9 and 10 and Table 5. FIG. 5 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 is composed 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, which are arranged in order from the object side along the optical axis. When focusing from an object at infinity to a close object, the second lens group G2 and the fourth lens group G4 move along the optical axis toward the image side, 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.

[0102] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the aperture stop S is fixed relative to the image surface 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. The second lens group G2 corresponds to the first focusing lens group GF1 arranged closest to the object side of the rear group GB. The third lens group G3 corresponds to the subsequent lens group GR1 arranged adjacent to the image surface side of the first focusing lens group GF1. The fourth lens group G4 corresponds to the second focusing lens group GF2 arranged closer to the image surface side than the first focusing lens group GF1.

[0103] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L12 and a biconcave negative lens L13, and a cemented lens formed by cementing a negative meniscus lens L14 with a convex surface facing the object side and a positive meniscus lens L15 with a convex surface facing the object side. The second lens group G2 is composed of, in order from the object side, a cemented lens having negative refractive power formed by cementing a positive meniscus lens L21 with a concave surface facing the object side and a biconcave negative lens L22.

[0104] The third lens group G3 is composed of, in order from the object side along the optical axis, a biconvex positive lens L31 and a negative meniscus lens L32 with a concave surface facing the object side. The fourth lens group G4 is composed of, in order from the object side, a biconvex positive lens L41 and a biconcave negative lens L42 cemented together to form a cemented lens having negative refractive power.

[0105] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a negative meniscus lens L51 with a convex surface facing the object side and a biconvex positive lens L52, and a negative meniscus lens L53 with a concave surface facing the object side. An image surface 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 surface I.

[0106] Table 5 below lists the values ​​of the specifications of the optical system according to the fifth embodiment.

[0107] (Table 5) [Overall specifications] f=68.369 fA=75.680 FNO=1.850 fR=52.672 2ω=35.083 Δx=11.502 Y=21.600 βF=6.768 TL=116.082 βB=0.903 Bf=1.000 βR1=0.110 Bf(a)=11.055 [Lens specifications] Surface number RD nd νd 1 113.3605 3.581 1.9229 18.90 2 259.4789 2.000 3 64.8154 7.756 1.7495 35.28 4 -305.8877 1.000 1.9229 18.90 5 89.4171 9.650 6 42.6939 1.000 1.9037 31.34 7 24.8498 8.072 1.6584 50.88 8 195.3643 2.647 9∞ (D9) (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] Focused at infinity Focused at mid-range Focused at close range f=68.369 β=-0.028 β=-0.148 D0∞ 2500.000 500.000 D9 2.021 4.185 13.522 D12 20.093 17.929 8.591 D16 1.418 1.749 4.177 D19 5.496 5.164 2.737 [Lens group data] Group starting plane focal length G1 1 75.680 G2 10 -59.462 G3 13 39.475 G4 17 -105.696 G5 20 -171.475

[0108] Fig. 10(A) is a diagram showing various aberrations of the optical system according to Example 5 when focusing at infinity. Fig. 10(B) is a diagram showing various aberrations of the optical system according to Example 5 when focusing at a close distance. From each diagram showing various aberrations, it can be seen that the optical system according to Example 5 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 the variation in the angle of view when focusing.

[0109] (Sixth Example) The sixth embodiment will be described with reference to FIGS. 11 and 12 and Table 6. FIG. 11 is a diagram showing the lens configuration of an optical system according to the sixth embodiment. The optical system OL(6) according to the sixth embodiment comprises, arranged in order from the object side along the optical axis, a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power. The optical system is made up of 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. 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 along the optical axis toward the image side, and the intervals between the adjacent lens groups change. 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 plane I.

[0110] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the aperture stop S is fixed relative to the image surface 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. The second lens group G2 corresponds to the first focusing lens group GF1 arranged closest to the object side of the rear group GB. The third lens group G3 corresponds to the subsequent lens group GR1 arranged adjacent to the image surface side of the first focusing lens group GF1. The fourth lens group G4 corresponds to the second focusing lens group GF2 arranged closer to the image surface side than the first focusing lens group GF1.

[0111] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a positive meniscus lens L12 with a convex surface facing the object side, a cemented lens formed by cementing a positive meniscus lens L13 with a convex surface facing the object side and a negative meniscus lens L14 with a convex surface facing the object side, a negative meniscus lens L15 with a convex surface facing the object side, and a positive meniscus lens L16 with a convex surface facing the object side. The second lens group G2 is composed of, in order from the object side, a cemented lens having negative refractive power formed by cementing a negative meniscus lens L21 with a convex surface facing the object side and a negative meniscus lens L22 with a convex surface facing the object side.

[0112] The third lens group G3 is composed of, in order from the object side along the optical axis, a cemented lens formed by cementing together a biconcave negative lens L31 and a biconvex positive lens L32, a positive meniscus lens L33 with a convex surface facing the object side, and a biconvex positive lens L34. The fourth lens group G4 is composed of a negative meniscus lens L41 with a convex surface facing the object side.

[0113] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a cemented lens formed by cementing together a biconvex positive lens L51 and a negative meniscus lens L52 with a concave surface facing the object side, and a negative meniscus lens L53 with a concave surface facing the object side. An image surface 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 surface I.

[0114] Table 6 below lists the values ​​of the specifications of the optical system according to the sixth embodiment.

[0115] (Table 6) [Overall specifications] f=79.983 fA=80.002 FNO=1.650 fR=58.141 2ω=14.994 Δx=8.575 Y=21.600 βF=3.011 TL=127.000 βB=1.000 Bf=1.000 βR1=0.280 Bf(a)=12.166 [Lens specifications] Surface number RD nd νd 1 110.5878 4.985 1.9630 24.11 2 283.6905 0.100 3 63.6059 4.396 2.0033 28.27 4 89.9017 3.000 5 80.0000 5.550 1.6935 53.20 6 383.6873 1.200 1.8929 20.36 7 84.9195 5.586 8 48.6443 1.000 1.8467 23.78 9 28.2642 0.248 10 28.4061 10.976 1.4970 81.61 11 231.2679 2.922 12∞ (D12) (Aperture S) 13 267.2771 1.500 1.6230 58.16 14 36.6616 3.000 1.8590 22.73 15 35.7069 (D15) 16 -36.0649 1.000 1.7380 32.33 17 92.6451 8.190 1.7725 49.62 18 -48.8133 0.100 19 64.0592 4.832 1.7725 49.60 20 306.9860 1.122 21 88.0545 5.785 1.9229 20.88 22 -184.9624 (D22) 23 140.5931 1.505 1.6910 54.82 24 48.6168 (D24) 25 83.3736 11.265 1.8515 40.78 26 -30.3564 1.000 1.8081 22.74 27 -217.6682 3.835 28 -42.0504 1.000 1.7783 23.91 29 -2185.7734 10.111 30 ∞ 1.600 1.5168 63.88 31∞Bf [Variable interval data] Focused at infinity Focused at mid-range Focused at close range f=79.983 β=-0.032 β=-0.113 D0∞ 2544.448 725.082 D12 1.300 3.613 9.875 D15 18.706 16.393 10.131 D22 1.300 2.156 4.812 D24 8.887 8.031 5.375 [Lens group data] Group starting plane focal length G1 1 80.002 G2 13 -67.065 G3 16 41.282 G4 23 -108.270 G5 25 -1174.941

[0116] Fig. 12(A) is a diagram showing various aberrations of the optical system according to Example 6 when focusing at infinity. Fig. 12(B) is a diagram showing various aberrations of the optical system according to Example 6 when focusing at a close distance. From each diagram showing various aberrations, it can be seen that the optical system according to Example 6 has excellent imaging performance, with various aberrations being well corrected over the entire range from focusing at infinity to focusing at close distances. 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. do.

[0117] (Seventh Example) The seventh embodiment will be described with reference to FIGS. 13 to 14 and Table 7. FIG. 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 is composed of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive 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 along the optical axis toward the image side, and the interval between the adjacent lens groups changes. Note that the first lens group G1 and the third lens group G3 are fixed with respect to the image surface I during focusing.

[0118] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the aperture stop S is fixed relative to the image surface I. In this embodiment, the first lens group G1 constitutes the front group GA, and the second lens group G2 and the third lens group G3 constitute the rear group GB. The second lens group G2 corresponds to the focusing lens group GF arranged closest to the object side of the rear group GB. The third lens group G3 corresponds to the rear lens group GR1 arranged adjacent to the focusing lens group GF on the image surface side.

[0119] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L12 and a biconcave negative lens L13, and a cemented lens formed by cementing a negative meniscus lens L14 with a convex surface facing the object side and a positive meniscus lens L15 with a convex surface facing the object side. The second lens group G2 is composed of, in order from the object side, a cemented lens having negative refractive power formed by cementing a positive meniscus lens L21 with a concave surface facing the object side and a biconcave negative lens L22.

[0120] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconvex positive lens L31, a cemented lens in which a biconcave negative lens L32 and a biconvex positive lens L33 are cemented together, a cemented lens in which a biconvex positive lens L34 and a biconcave negative lens L35 are cemented together, a negative meniscus lens L36 with a convex surface facing the object side, a biconvex positive lens L37, and a negative meniscus lens L38 with a concave surface facing the object side. An image surface I is disposed on the image side of the third lens group G3. A parallel plate PP is disposed between the third lens group G3 and the image surface I.

[0121] Table 7 below lists the values ​​of the specifications of the optical system according to the seventh embodiment.

[0122] (Table 7) [Overall specifications] f=73.180 fA=65.047 FNO=1.857 fR=61.979 2ω=32.805 Δx=7.838 Y=21.600 βF=5.900 TL=119.318 βB=1.125 Bf=1.006 βR1=0.191 Bf(a)=11.061 [Lens specifications] Surface number RD nd νd 1 86.3436 3.855 1.9229 18.90 2 240.9219 0.100 3 109.1989 5.811 1.7495 35.28 4 -148.8703 1.000 1.9229 20.88 5 100.0000 11.212 6 40.0083 1.000 1.9037 31.31 7 23.8536 8.324 1.6968 55.53 8 541.8771 3.546 9∞ (D9) (Aperture S) 10 -102.6387 2.695 1.8590 22.73 11 -47.9027 1.940 1.5530 55.07 12 32.6973 (D12) 13 34.2780 7.412 1.7015 41.24 14 -122.6095 0.204 15 -30343.0670 1.113 1.9537 32.32 16 31.2978 6.189 1.7639 48.49 17 -1254.1635 1.400 18 141.8350 5.000 1.5378 74.70 19 -48.4566 1.000 1.6398 34.47 20 90.6288 2.112 21 240.5167 1.001 1.8548 24.80 22 37.9682 0.100 23 37.4387 12.070 2.0007 25.46 24 -277.6337 5.753 25 -23.7721 1.076 1.6730 38.26 26 -96.5381 9.000 27 ∞ 1.600 1.5168 63.88 28∞Bf [Variable interval data] Focused at infinity Focused at mid-range Focused at close range f=73.180 β=-0.029 β=-0.128 D0∞ 2558.661 610.735 D9 2.242 3.982 10.080 D12 21.558 19.818 13.719 [Lens group data] Group starting plane focal length G1 1 65.047 G2 10 -52.462 G3 13 61.979

[0123] Fig. 14(A) is a diagram showing various aberrations of the optical system according to Example 7 when focusing at infinity. Fig. 14(B) is a diagram showing various aberrations of the optical system according to Example 7 when focusing at a close distance. From each diagram showing various aberrations, it can be seen that the optical system according to Example 7 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 the variation in the angle of view when focusing.

[0124] (Eighth Example) Example 8 will be described with reference to Figs. 15 to 16 and Table 8. Fig. 15 is a diagram showing the lens configuration of an optical system according to Example 8. An optical system OL(8) according to Example 8 is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 moves along the optical axis toward the image side, The fourth lens group G4 moves toward the object side along the optical axis, and the intervals between adjacent lens groups change. Note that 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 during focusing.

[0125] The aperture stop S is disposed between the first lens group G1 and the second lens group G2. During focusing, the aperture stop S is fixed relative to the image surface 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. The second lens group G2 corresponds to the first focusing lens group GF1 arranged closest to the object side of the rear group GB. The third lens group G3 corresponds to the subsequent lens group GR1 arranged adjacent to the image surface side of the first focusing lens group GF1. The fourth lens group G4 corresponds to the second focusing lens group GF2 arranged closer to the image surface side than the first focusing lens group GF1.

[0126] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a positive meniscus lens L11 with a convex surface facing the object side, a positive meniscus lens L12 with a convex surface facing the object side, and a cemented lens formed by cementing a biconvex positive lens L13 and a biconcave negative lens L14. The second lens group G2 is composed of a negative meniscus lens L21 with a convex surface facing the object side.

[0127] The third lens group G3 is composed of a biconvex positive lens L31. The fourth lens group G4 is composed of a positive meniscus lens L41 with its convex surface facing the object side.

[0128] The fifth lens group G5 is composed of a negative meniscus lens L51 with its concave surface facing the object side. An image surface 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 surface I.

[0129] Table 8 below lists the values ​​of the specifications of the optical system according to the eighth embodiment.

[0130] (Table 8) [Overall specifications] f=82.010 fA=84.922 FNO=2.050 fR=72.581 2ω=32.753 Δx=8.605 Y=21.600 βF=3.508 TL=90.018 βB=0.966 Bf=1.322 βR1=0.219 Bf(a)=16.376 [Lens specifications] Surface number RD nd νd 1 49.7600 5.102 1.7550 52.32 2 207.7589 0.100 3 43.3970 4.415 1.6180 63.33 4 120.3692 0.100 5 35.5101 6.189 1.5928 68.62 6 -216.6911 2.098 1.9053 35.04 7 28.2895 5.240 8∞ (D8) (Aperture S) 9 5405.8128 1.000 1.4875 70.23 10 35.3627 (D10) 11 41.2560 9.000 1.5174 52.43 12 -51.9830 (D12) 13 98.4043 2.467 1.8590 22.73 14 222.8980 (D14) 15 -31.6093 3.000 1.8502 30.05 16 -173.6461 14.000 17 ∞ 1.600 1.5168 63.88 18∞Bf [Variable interval data] Focused at infinity Focused at mid-range Focused at close range f=82.010 β=-0.033 β=-0.115 D0∞ 2526.094 756.181 D8 1.985 4.234 10.591 D10 16.324 14.075 7.719 D12 10.523 8.452 4.434 D14 5.552 7.623 11.641 [Lens group data] Group starting plane focal length G1 1 84.922 G2 9 -73.023 G3 11 45.967 G4 13 203.256 G5 15 -45.895

[0131] Fig. 16(A) is a diagram showing various aberrations of the optical system according to Example 8 when focusing at infinity. Fig. 16(B) is a diagram showing various aberrations of the optical system according to Example 8 when focusing at a close distance. From each diagram showing various aberrations, it can be seen that the optical system according to Example 8 has excellent imaging performance, with various aberrations being well corrected 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 the variation in the angle of view when focusing.

[0132] 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 (16) for all the examples (Examples 1 to 8). Condition (1) 0.50 <ST / TL<0.95 Condition (2) 0.65<(-fF) / fA<1.20 Conditional expression (3) 0.70<(-fF) / fR<1.80 Conditional expression (4) 0.00<βR1 / βF<0.25 Conditional expression (5) 0.03<Δx / f<0.35 Condition (6) 0.65 <f / (-fF)<1.60 Condition (7) 2.00 <TL / (FNO×Bf)<10.00 Conditional expression (8) -2.50<(rFR2+rFR1) / (rFR2-rFR1)<-0.25 Conditional expression (9) 0.90<(rNR2+rNR1) / (rNR2-rNR1)<2.65 Conditional expression (10) 0.08<1 / βF<0.55 Conditional expression (11) {βF+(1 / βF)} -2 <0.15 Condition (12) 0.003 <BLDF / TL<0.060 Conditional expression (13) 0.05<βB / βF<0.50 Condition (14) 0.05 <Bf / TL<0.25 Condition (15) 1.00 <FNO<3.00 Conditional expression (16) 12.00°<2ω<40.00°

[0133] [Conditional Expression Corresponding Values] (First to Fourth Examples) Conditional Expression 1st Example 2nd Example 3rd Example 4th Example (1) 0.702 0.667 0.747 0.695 (2) 0.914 0.794 1.070 0.827 (3) 1.268 0.950 1.335 1.598 (4) 0.138 0.038 0.081 0.040 (5) 0.146 0.095 0.127 0.128 (6) 1.065 1.275 0.748 0.862 (7) 8.113 5.488 2.447 9.359 (8) -1.192 -1.054 -2.198 -1.300 (9) 1.661 1.441 2.433 2.272 (10) 0.384 0.227 0.401 0.265 (11) 0.112 0.047 0.119 0.061 (12) 0.009 0.011 0.011 0.008 (13) 0.374 0.230 0.321 0.188 (14) 0.087 0.098 0.198 0.086 (15) 1.424 1.855 2.060 1.242 (16) 28.285 28.002 28.969 28.622 [Conditional Expression Corresponding Values] (Fifth to Eighth Examples) Conditional Expression 5th Example 6th Example 7th Example 8th Example (1) 0.692 0.685 0.708 0.742 (2) 0.786 0.838 0.807 0.860 (3) 1.129 1.154 0.846 1.006 (4) 0.016 0.093 0.032 0.062 (5) 0.168 0.107 0.107 0.105 (6) 1.150 1.193 1.395 1.123 (7) 5.676 6.327 5.808 2.681 (8) -0.568 -1.308 -0.517 -1.013 (9) 1.291 1.039 1.653 1.445 (10) 0.148 0.332 0.169 0.285 (11) 0.021 0.089 0.027 0.070 (12) 0.028 0.035 0.039 0.011 (13) 0.133 0.332 0.191 0.275 (14) 0.095 0.096 0.093 0.182 (15) 1.850 1.650 1.857 2.050 (16) 35.083 14.994 32.805 32.753

[0134] According to each of the above embodiments, an optical system with little fluctuation in the angle of view during focusing can be realized.

[0135] The above-mentioned embodiments are merely examples of the present invention, and the present invention is not limited to these.

[0136] The following contents can be appropriately adopted within the scope that does not impair the optical performance of the optical system of this embodiment.

[0137] Although three-group and five-group configurations have been shown as examples of the optical system of this embodiment, the present application is not limited thereto, and optical systems of other group configurations (for example, four groups, 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] The aperture diaphragm is preferably disposed between the first lens group and the second lens group, but it is also possible to use the lens frame to fulfill that role instead of providing a member serving as the aperture diaphragm.

[0142] 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]

[0143] 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. An optical system comprising a stop, a front group, and a rear group disposed closer to the image side than the front group, the rear group includes a first focusing lens group having negative refractive power and arranged closest to the object side of the rear group, and a second focusing lens group arranged closer to the image side than the first focusing lens group, During focusing, the first focusing lens group and the second focusing lens group move along the optical axis, An optical system that satisfies the following condition: 0.50<ST / TL<0.95 where ST is the distance on the optical axis from the stop to the image plane. TL: total length of the optical system

2. 2. The optical system according to claim 1, wherein the following condition is satisfied: 0.65<(-fF) / fA<1.20 where fF is the focal length of the first focusing lens group. fA: focal length of the front group

3. the rear group has at least one lens group arranged closer to the image plane than the first focusing lens group, 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.70<(-fF) / fR<1.80 where fF is the focal length of the first focusing lens group. fR: composite focal length of the at least one lens group

4. the rear group includes a subsequent lens group arranged adjacent to the first focusing lens group on the image plane side, 4. The optical system according to claim 1, wherein the following condition is satisfied: 0.00<βR1 / βF<0.25 where βR1 is the lateral magnification of the subsequent lens group when focusing on an object at infinity. βF: lateral magnification of the first focusing lens group when focusing on an object at infinity

5. 5. The optical system according to claim 1, wherein the following condition is satisfied: 0.03<Δx / f<0.35 where Δx is the amount of movement of the first focusing lens group when focusing from an object at infinity to an object at a close distance. f: focal length of the optical system

6. 6. The optical system according to claim 1, wherein the following condition is satisfied: 0.65<f / (-fF)<1.60 where f is the focal length of the optical system. fF: focal length of the first focusing lens group

7. 7. The optical system according to claim 1, wherein the following condition is satisfied: 2.00<TL / (FNO×Bf)<10.00 where FNO: F-number of the optical system Bf: back focus of the optical system

8. An optical system described in any one of claims 1 to 7, wherein the aperture is arranged between the front group and the rear group.

9. 9. The optical system according to claim 1, wherein the following condition is satisfied: -2.50<(rFR2+rFR1) / (rFR2-rFR1)<-0.25 where rFR1 is the radius of curvature of the lens surface closest to the object in the first focusing lens group. rFR2: radius of curvature of the lens surface in the first focusing lens group closest to the image plane

10. 10. The optical system according to claim 1, wherein the following condition is satisfied: 0.90<(rNR2+rNR1) / (rNR2-rNR1)<2.65 where rNR1 is the radius of curvature of the object-side lens surface of the lens arranged closest to the image plane in the optical system. rNR2: the radius of curvature of the lens surface closest to the image plane in the lens arranged closest to the image plane in the optical system

11. The optical system according to any one of claims 1 to 10, which satisfies the following conditional expression: 0.08<1 / βF<0.55 where βF is the lateral magnification of the first focusing lens group when focusing on an object at infinity.

12. 12. The optical system according to claim 1, wherein the following condition is satisfied: {βF+(1 / βF)} -2 <0.15 where βF is the lateral magnification of the first focusing lens group when focusing on an object at infinity.

13. The optical system according to any one of claims 1 to 12, which satisfies the following conditional expression: 0.003<BLDF / TL<0.060 where BLDF is the length of the first focusing lens group on the optical axis.

14. The optical system according to any one of claims 1 to 13, which satisfies the following conditional expression: 0.05<βB / βF<0.50 where βB is the lateral magnification of the rear group when focusing on an object at infinity. βF: lateral magnification of the first focusing lens group when focusing on an object at infinity

15. The optical system according to any one of claims 1 to 14, which satisfies the following conditional expression: 0.05<Bf / TL<0.25 where Bf is the back focus of the optical system.

16. The optical system according to any one of claims 1 to 15, which satisfies the following conditional expression: 1.00<FNO<3.00 where FNO: F-number of the optical system

17. 17. The optical system according to claim 1, wherein the following condition is satisfied: 12.00°<2ω<40.00° where 2ω is the total angle of view of the optical system.

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

Images