Optical system, optical apparatus, and method for manufacturing optical system

Abstract

To provide an optical system which is lightweight and compact and has excellent optical performance.SOLUTION: The optical system OL includes, in order from an object, a first lens group G1 having a positive refractive power, a second lens group G2, and a third lens group G3, the second lens group G2 moves along the optical axis during focusing, and the first lens group G1 includes at least one negative lens L1n and a first positive lens L1p disposed closest to the object and satisfying the following conditional expressions: 0.023 * ν dL1p + ndL1p 2.500 where ndL1p is the index of refraction of the first positive lens L1p with respect to the d-line, ν dL1p is the Abbe number of the first positive lens L1p with respect to the d-line, and the following conditional expressions are satisfied. 0.600 <TL / f <1.200, where TL is a distance on the optical axis from a lens surface closest to the object side in the optical system OL to the image plane, and f is a focal length of the entire optical system OL SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system, an optical instrument, and a method for manufacturing an optical system. [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). Among such optical systems, there is a demand for optical systems that are lightweight and compact yet have various aberrations well corrected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-215492 Summary of the Invention

[0004] An optical system according to the present invention comprises a first lens group having positive refractive power, a second lens group, and a third lens group, arranged in this order from the object side along an optical axis, wherein the second lens group moves along the optical axis during focusing, and the first lens group comprises at least one negative lens and a first positive lens arranged closest to the object side of the first lens group, and the first positive lens satisfies the following conditional expression: 0.023×νdL1p+ndL1p<2.500 where ndL1p is the refractive index of the first positive lens with respect to the d-line. νdL1p: Abbe number of the first positive lens based on the d line Furthermore, the following conditional expression is satisfied: 0.600 <TL / f<1.200 where TL is the distance on the optical axis from the lens surface closest to the object in the optical system to the image plane. f: focal length of the entire optical system

[0005] An optical device according to the present invention includes the optical system described above.

[0006] A method for manufacturing an optical system according to the present invention includes: an optical system having a first lens group, a second lens group, and a third lens group, which are arranged in order from the object side along an optical axis, and each having a positive refractive power; During focusing, the second lens group moves along the optical axis, A method for manufacturing an optical system in which the first lens group has at least one negative lens, and a first positive lens is disposed closest to the object side of the first lens group, the first positive lens satisfying the following conditional expression: 0.023×νdL1p+ndL1p<2.500 where ndL1p is the refractive index of the first positive lens with respect to the d-line. νdL1p: Abbe number of the first positive lens based on the d line The method further includes a step of arranging each lens within the lens barrel so as to satisfy the following conditional expression: 0.600 <TL / f<1.200 where TL is the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane. f: focal length of the entire optical system [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram showing the lens configuration of an optical system according to Example 1. [Figure 2] 5A to 5C are diagrams illustrating various aberrations of the optical system according to Example 1 when focused at infinity. [Figure 3] FIG. 10 is a diagram showing the lens configuration of an optical system according to a second example. [Figure 4] 10A to 10C are diagrams showing various aberrations of the optical system according to Example 2 when focused on infinity. [Figure 5] FIG. 10 is a diagram showing the lens configuration of an optical system according to Example 3. [Figure 6] 10A to 10C are diagrams showing various aberrations of the optical system according to Example 3 when focused at infinity. [Figure 7] FIG. 1 is a diagram showing the configuration of a camera including an optical system according to each embodiment. [Figure 8] 10 is a flowchart illustrating a method for manufacturing an optical system according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0009] Light from the subject is collected by the optical system OL of the photographing lens 3 and reaches the image plane I of the image sensor 4. The light from the subject that reaches the image plane I is photoelectrically converted by the image sensor 4 and recorded as digital image data in a memory (not shown). The digital image data recorded in the memory can be displayed on the LCD screen 5 in response to a user operation. Note that this camera may be a mirrorless camera or a single-lens reflex camera with a quick-return mirror. Also, the optical system OL shown in FIG. 7 is a schematic representation of an optical system provided in the photographing lens 3, and the lens configuration of the optical system OL is not limited to this configuration.

[0010] Next, an optical system according to this embodiment will be described. As shown in FIG. 1, an optical system OL(1) as an example of the optical system OL according to this embodiment has, arranged along the optical axis from the object side, a first lens group G1 having positive refractive power, a second lens group G2, and a third lens group, and during focusing, the second lens group G2 moves along the optical axis. The first lens group G1 has at least one negative lens L1n and a first positive lens L1p that is located closest to the object side of the first lens group and satisfies the following conditional expression (1): In each embodiment, the term "lens" refers to a single lens or one of the cemented lenses in a cemented lens.

[0011] 0.023×νdL1p+ndL1p<2.500 (1) where ndL1p is the refractive index of the first positive lens L1p for the d line νdL1p: Abbe number of the first positive lens L1p based on the d line

[0012] Furthermore, with the above configuration, the optical system OL satisfies the following conditional expression (2).

[0013] 0.600 <TL / f<1.200 ···(2) where TL is the distance on the optical axis from the lens surface closest to the object in the optical system OL to the image plane f: focal length of the entire optical system

[0014] According to this embodiment, it is possible to obtain an optical system that is lightweight and compact yet has various aberrations well corrected, and an optical device equipped with this optical system. The optical system OL according to this embodiment may be the optical system OL(2) shown in Figure 3 or the optical system OL(3) shown in Figure 5.

[0015] Conditional expression (1) defines an appropriate relationship between the refractive index of the first positive lens L1p at the d-line and the Abbe number based on the d-line. By satisfying conditional expression (1), various aberrations can be corrected well and the optical system can be made lighter.

[0016] If the corresponding value of conditional expression (1) exceeds the upper limit, it becomes difficult to achieve both achromatization of second-order chromatic aberrations such as longitudinal chromatic aberration and weight reduction. By setting the upper limit of conditional expression (1) to 2.470, 2.440, 2.410, 2.380, or even 2.350, the effect of this embodiment can be further ensured.

[0017] Setting the lower limit of conditional expression (1) to 0.000 allows for good correction of first-order chromatic aberration (achromatism) and spherical aberration, etc. To further ensure the effects of this embodiment, the lower limit of conditional expression (1) may be set to 1.000 or even 2.000.

[0018] Conditional expression (2) defines an appropriate relationship between the axial distance from the lens surface closest to the object in the optical system OL according to this embodiment to the image plane and the focal length of the entire optical system OL. By satisfying conditional expression (2), it is possible to obtain an optical system with a short overall length while effectively suppressing the occurrence of various aberrations.

[0019] If the corresponding value of conditional expression (2) exceeds the upper limit, it becomes difficult to shorten the overall length of the optical system. By setting the upper limit of conditional expression (2) to 1.180, 1.160, 1.140, 1.120, or even 1.100, the effect of this embodiment can be further ensured.

[0020] If the corresponding value of conditional expression (2) falls below the lower limit, it becomes difficult to correct coma and axial chromatic aberration at close distances. By setting the lower limit of conditional expression (2) to 0.640, 0.680, 0.720, 0.760, or even 0.800, the effects of this embodiment can be further ensured.

[0021] In the optical system OL according to this embodiment, it is preferable that the first positive lens L1p satisfy the following conditional expressions (3) and (4). 0.590<θgFL1p<0.800 (3) νdL1p<40.00 (4) Here, θgFL1p: partial dispersion ratio of the first positive lens L1p, and is defined by the following formula when the refractive index of the first positive lens L1p for the g-line is ngL1p, the refractive index of the first positive lens L1p for the F-line is nFL1p, and the refractive index of the first positive lens L1p for the C-line is nCL1p. θgFL1p=(ngL1p-nFL1p) / (nFL1p-nCL1p)

[0022] Conditional expression (3) appropriately defines the anomalous dispersion of the first positive lens L1p. By satisfying conditional expression (3), in the correction of chromatic aberration, in addition to first-order achromatism, second-order spectrum can be well corrected.

[0023] If the corresponding value of conditional expression (3) exceeds the upper limit, it becomes difficult to correct chromatic aberration. By setting the upper limit of conditional expression (3) to 0.770, 0.740, 0.710, 0.680, or even 0.650, the effect of this embodiment can be further ensured.

[0024] If the corresponding value of conditional expression (3) falls below the lower limit, it becomes difficult to correct chromatic aberrations such as longitudinal chromatic aberration. By setting the lower limit of conditional expression (3) to 0.598, 0.605, 0.613, or even 0.620, the effects of this embodiment can be further ensured.

[0025] Conditional expression (4) defines an appropriate range for the Abbe number of the first positive lens L1p with respect to the d-line. By satisfying conditional expression (4), spherical aberration, coma, and the like can be corrected well.

[0026] If the corresponding value of conditional expression (4) exceeds the upper limit, anomalous dispersion becomes small, making it difficult to correct secondary chromatic aberration. By setting the upper limit of conditional expression (4) to 39.00, 38.00, 37.00, 36.00, or even 35.00, the effect of this embodiment can be further ensured.

[0027] By setting the lower limit of conditional expression (4) to 0.00, first-order chromatic aberration can be effectively corrected. To further enhance the effect of this embodiment, the lower limit of conditional expression (4) may be set to 4.00, 8.00, 12.00, 16.00, or even 20.00.

[0028] In the optical system OL according to this embodiment, it is preferable that at least one negative lens L1n in the first lens group G1 satisfies the following conditional expressions (5) and (6). 1.450 <ndL1n<1.950 ···(5) 20.00<νdL1n<40.00 (6) where νdL1n: Abbe number of at least one negative lens L1n in the first lens group G1 with reference to the d-line ndL1n: refractive index for the d-line of at least one negative lens L1n in the first lens group G1

[0029] Conditional expression (5) defines an appropriate range of the refractive index for the d-line of at least one negative lens L1n in the first lens group G1. By satisfying conditional expression (5), it is possible to effectively correct chromatic aberration while reducing the weight of the entire optical system.

[0030] If the value corresponding to conditional expression (5) exceeds the upper limit, the weight of the lens increases, making it difficult to make the optical system lightweight. By setting the upper limit of conditional expression (5) to 1.930, 1.920, 1.910, 1.900, 1.890, or even 1.880, the effect of this embodiment can be further ensured.

[0031] If the corresponding value of conditional expression (5) falls below the lower limit, it becomes difficult to correct spherical aberration and coma. By setting the lower limit of conditional expression (5) to 1.480, 1.510, 1.540, 1.570, or even 1.600, the effect of this embodiment can be further ensured.

[0032] Conditional expression (6) defines an appropriate range for the Abbe number of the negative lens L1n relative to the d-line. By satisfying conditional expression (6), in addition to achieving first-order achromatism in correcting chromatic aberration, the overall optical system can be made lighter.

[0033] If the corresponding value of conditional expression (6) exceeds the upper limit, it becomes difficult to correct chromatic aberration. By setting the upper limit of conditional expression (6) to 37.00, 36.00, 35.00, 34.00, or even 33.00, the effect of this embodiment can be further ensured.

[0034] If the corresponding value of conditional expression (6) falls below the lower limit, the weight of the lens increases, making it difficult to make the optical system lightweight. By setting the lower limit of conditional expression (6) to 21.00, 22.00, 23.00, 24.00, or even 25.00, the effect of this embodiment can be further ensured.

[0035] In the optical system OL according to this embodiment, the first lens group G1 includes a partial lens group Gp composed of positive lenses and arranged adjacent to the image plane side of the first positive lens L1p, and the partial lens group Gp may be arranged closer to the object side than the negative lens L1n in the first lens group G1. With this configuration, various aberrations including spherical aberration can be effectively corrected.

[0036] In the optical system OL according to this embodiment, the first lens group G1 includes a partial lens group Gp composed of positive lenses arranged adjacent to the first positive lens L1p on the image plane side, and the second positive lens L2p arranged closest to the object in the partial lens group Gp may satisfy the following conditional expression: ndL2p<1.750 (7) 80.00<νdL2p ···(8) where ndL2p is the refractive index of the second positive lens L2p for the d line. νdL2p: Abbe number of the second positive lens L2p based on the d line

[0037] By including the second positive lens L2p, various aberrations including spherical aberration can be corrected well.

[0038] Conditional expression (7) defines an appropriate range for the refractive index of the second positive lens L2p for the d-line. By satisfying conditional expression (7), various aberrations can be corrected well.

[0039] If the corresponding value of conditional expression (7) exceeds the upper limit, the Abbe number becomes small, making it difficult to correct first-order chromatic aberration (achromatization). By setting the upper limit of conditional expression (7) to 1.700, 1.675, 1.650, 1.625, or even 1.600, the effect of this embodiment can be further ensured.

[0040] By setting the lower limit of conditional expression (7) to 1.400, spherical aberration can be effectively corrected. To further ensure the effect of this embodiment, the lower limit of conditional expression (7) may be set to 1.410, 1.420, or even 1.430.

[0041] Conditional expression (8) defines an appropriate range for the Abbe number of the second positive lens L2p with respect to the d-line. By satisfying conditional expression (8), chromatic aberration can be corrected well.

[0042] If the corresponding value of conditional expression (8) falls below the lower limit, it becomes difficult to effectively correct chromatic aberration. By setting the lower limit of conditional expression (8) to 83.00, 86.00, 89.00, 92.00, or even 95.00, the effect of this embodiment can be further ensured.

[0043] By setting the upper limit of conditional expression (8) to 100.00, the refractive index does not become too low and spherical aberration and coma can be corrected well. To further ensure the effect of this embodiment, the upper limit of conditional expression (8) may be set to 99.00 or even 98.00.

[0044] In the optical system OL according to this embodiment, the first lens group G1 may have a second positive lens L2p arranged adjacent to the image surface side of the first positive lens L1p, and a third positive lens L3p arranged adjacent to the image surface side of the second positive lens L2p. This configuration allows for excellent correction of various aberrations, including spherical aberration. It is preferable to use a lens made of calcium fluoride single crystal (fluorite) as the second positive lens L2p. Alternatively, a material other than fluorite with properties similar to fluorite may be used. Using fluorite not only reduces the weight of the optical system, but also allows for excellent correction of chromatic aberration and the like.

[0045] In the optical system OL according to this embodiment, the following conditional expression may be satisfied. 0.200 <f2 / f<1.000 ···(9) However, f2 is the focal length of the second lens group G2. f: focal length of the entire optical system

[0046] Conditional expression (9) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the entire optical system OL. By satisfying conditional expression (9), it is possible to achieve appropriate focusing accuracy and the amount of movement during focusing.

[0047] If the value corresponding to conditional expression (9) exceeds the upper limit, the movement amount of the second lens group G2, which is the lens group that moves during focusing, increases, making it difficult to adjust the movement amount appropriately. By setting the upper limit of conditional expression (9) to 0.960, 0.920, 0.880, 0.840, or even 0.800, the effect of this embodiment can be further ensured.

[0048] If the value corresponding to conditional expression (9) falls below the lower limit, the movement amount of the second lens group G2, which is the lens group that moves during focusing, becomes too small, which is undesirable because it reduces the focusing accuracy. By setting the lower limit of conditional expression (9) to 0.240, 0.280, 0.320, 0.360, or even 0.400, the effect of this embodiment can be made more certain.

[0049] In the optical system OL according to this embodiment, the second lens group G2 may have a positive lens that satisfies the following conditional expression. 1,500 <ndLp<1.900 ···(10) 30.00<νdLp<70.00 (11) where ndLp is the refractive index of the positive lens in the second lens group G2 at the d-line νdLp: Abbe number of the positive lens in the second lens group G2 based on the d-line

[0050] Conditional expression (10) defines an appropriate range for the refractive index of the positive lens in the second lens group G2 at the d-line. By satisfying conditional expression (10), it is possible to improve the performance when focusing at close distances and reduce the weight of the entire optical system.

[0051] If the corresponding value of conditional expression (10) exceeds the upper limit, the weight of the second lens group G2, which is the lens group that moves during focusing, increases, making it difficult to make the optical system lightweight. By setting the upper limit of conditional expression (10) to 1.880, 1.860, 1.840, or even 1.820, the effects of this embodiment can be further ensured.

[0052] If the corresponding value of conditional expression (10) falls below the lower limit, it becomes difficult to correct various aberrations during close-range focusing. By setting the lower limit of conditional expression (10) to 1.510, 1.520, 1.530, 1.540, or even 1.550, the effect of this embodiment can be further ensured.

[0053] Conditional expression (11) defines an appropriate range for the Abbe number of the positive lens in the second lens group G2, with reference to the d-line. By satisfying conditional expression (11), various aberrations can be corrected well.

[0054] If the corresponding value of conditional expression (11) exceeds the upper limit, the fluctuation of spherical aberration for each wavelength due to focusing becomes too large, which is undesirable. By setting the upper limit of conditional expression (11) to 68.00, 66.00, 64.00, 62.00, or even 60.00, the effect of this embodiment can be further ensured.

[0055] If the value of conditional expression (11) is below the lower limit, the correction of first-order chromatic aberration (achromatism) will be poor. By setting the lower limit of conditional expression (11) to 32.00, 34.00, 36.00, 38.00, or even 40.00, the effect of this embodiment can be made more certain.

[0056] In the optical system OL according to this embodiment, the second lens group G2 may be composed of a single lens, which allows for a reduction in the weight of the lens group that moves during focusing.

[0057] In the optical system OL according to this embodiment, the second lens group G2 may move toward the object side during focusing. By adopting such a configuration, the effect of this embodiment can be more reliably achieved.

[0058] In the optical system OL according to this embodiment, the following conditional expression may be satisfied. 0.500 <f1 / f<2.800 ···(12) where f1 is the focal length of the first lens group G1 f: focal length of the entire optical system

[0059] Conditional expression (12) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the entire optical system OL. By satisfying conditional expression (12), it is possible to reduce the weight of the optical system while effectively correcting various aberrations.

[0060] If the corresponding value of conditional expression (12) exceeds the upper limit, the weight of the lens increases, making it difficult to reduce the weight of the optical system. By setting the upper limit of conditional expression (12) to 2.720, 2.640, 2.560, 2.480, or even 2.400, the effect of this embodiment can be further ensured.

[0061] If the corresponding value of conditional expression (12) falls below the lower limit, fluctuations in coma and axial chromatic aberration due to focusing become too large, which is undesirable. By setting the lower limit of conditional expression (12) to 0.560, 0.620, 0.680, 0.740, or even 0.800, the effect of this embodiment can be made more certain.

[0062] In the optical system OL according to this embodiment, the following conditional expression may be satisfied. 0.400<(-f3) / f<2.000 ···(13) However, f3 is the focal length of the third lens group G3. f: focal length of the entire optical system

[0063] Conditional expression (13) defines an appropriate relationship between the focal length of the third lens group G3 and the focal length of the entire optical system OL. By satisfying conditional expression (13), it is possible to effectively correct various aberrations, such as lateral chromatic aberration, while reducing the weight of the entire optical system.

[0064] If the corresponding value of conditional expression (13) exceeds the upper limit, the overall length of the optical system becomes too long, making it difficult to reduce the weight of the optical system. By setting the upper limit of conditional expression (13) to 1.840, 1.680, 1.520, 1.360, or even 1.200, the effect of this embodiment can be made more certain.

[0065] If the corresponding value of conditional expression (13) falls below the lower limit, it becomes difficult to correct various aberrations, including lateral chromatic aberration. By setting the lower limit of conditional expression (13) to 0.460, 0.520, 0.580, 0.640, or even 0.700, the effects of this embodiment can be further ensured.

[0066] In the optical system OL according to this embodiment, the first lens group G1 includes a partial lens group Gp composed of positive lenses and adjacent to the image plane side of the first positive lens L1p, and the second positive lens L2p is arranged closest to the object side in the partial lens group Gp, and the following conditional expression may be satisfied: 0.0000 <d1 / TL1<0.8000 ···(14) where d1 is the distance on the optical axis from the lens surface of the first positive lens L1p on the image plane side to the lens surface of the second positive lens L2p on the object side. TL1: the distance on the optical axis from the lens surface in the first lens group G1 closest to the object to the lens surface in the first lens group G1 closest to the image plane

[0067] Conditional expression (14) defines an appropriate relationship between the axial distance between the first positive lens L1p and the second positive lens L2p and the length of the first lens group G1. By satisfying conditional expression (14), various aberrations can be corrected well.

[0068] If the corresponding value of conditional expression (14) exceeds the upper limit, the fluctuation of spherical aberration for each wavelength due to focusing becomes too large, which is undesirable. By setting the upper limit of conditional expression (14) to 0.7500, 0.6800, 0.5500, 0.4500, 0.3500, 0.2500, or even 0.0100, the effect of this embodiment can be made more certain.

[0069] If the value corresponding to conditional expression (14) is below the lower limit, the weight of the lens increases, making it difficult to reduce the weight of the optical system. By setting the lower limit of conditional expression (14) to 0.0010, the effect of this embodiment can be more reliably achieved.

[0070] In the optical system OL according to this embodiment, the first lens group G1 includes a second positive lens L2p arranged adjacent to the image surface side of the first positive lens L1p, and a third positive lens L3p arranged adjacent to the image surface side of the second positive lens L2p, and may satisfy the following conditional expression: 0.400<(L3R2-L3R1) / (L3R2+L3R1)<3.500 ···(15) However, L3R1: Radius of curvature of the lens surface on the object side of the third positive lens L3p L3R2: Radius of curvature of the image-side lens surface of the third positive lens L3p

[0071] Conditional expression (15) defines an appropriate range for the shape factor of the third positive lens L3p. By satisfying conditional expression (15), spherical aberration and the like can be corrected well.

[0072] If the corresponding value of conditional expression (15) exceeds the upper limit, spherical aberration becomes too large and difficult to correct. By setting the upper limit of conditional expression (15) to 3.360, 3.220, 3.080, 2.940, or even 2.800, the effect of this embodiment can be further ensured.

[0073] If the corresponding value of conditional expression (15) is below the lower limit, the fluctuation of spherical aberration during focusing becomes too large, making correction difficult. By setting the lower limit of conditional expression (15) to 0.460, 0.520, 0.580, 0.640, or even 0.700, the effect of this embodiment can be further ensured.

[0074] In the optical system OL according to this embodiment, the third lens group G3 may include, arranged in order from the object side, at least one lens, a diaphragm S, and a vibration-reduction lens group Gvr that corrects the image formed on the image plane by moving in a direction perpendicular to the optical axis. Arranging the diaphragm S and the vibration-reduction lens group Gvr adjacent to each other allows for excellent correction of aberrations when the vibration-reduction lens group Gvr is driven to correct image blur caused by camera shake or the like. Furthermore, having at least one lens between the diaphragm S and the second lens group G2, which is a focusing lens group that moves during focusing, allows for a smaller diameter for the diaphragm S, thereby enabling the optical system to be made lighter.

[0075] In the above optical system OL, the following condition may be satisfied: 0.000 <dS / TLs<0.600 ···(16) where dS is the distance on the optical axis from the aperture stop S to the lens surface closest to the object in the vibration-reduction lens group Gvr. TLs: Distance on the optical axis from the aperture S to the image plane I

[0076] Conditional expression (16) defines an appropriate relationship between the distance between the aperture stop S and the vibration-reduction lens group Gvr and the distance from the aperture stop S to the image plane I. Satisfying conditional expression (16) makes it possible to improve the correction by the vibration-reduction lens group Gvr.

[0077] If the corresponding value of conditional expression (16) exceeds the upper limit, it becomes difficult to perform good correction by the vibration-reduction lens group Gvr. By setting the upper limit of conditional expression (16) to 0.500, 0.400, 0.300, 0.200, or even 0.150, the effect of this embodiment can be made more certain.

[0078] If the corresponding value of conditional expression (16) falls below the lower limit, the aperture stop S and the vibration reduction lens group Gvr will be too close, or they will collide, making it difficult to perform good correction by the vibration reduction lens group Gvr. By setting the lower limit of conditional expression (16) to 0.0010, 0.0015, 0.0020, 0.0025, or even 0.0030, the effects of this embodiment can be made even more certain.

[0079] In the optical system OL according to this embodiment, the following conditional expression may be satisfied. 3.00°<2ω<14.00° (17) However, 2ω: full field angle of optical system OL

[0080] Conditional expression (17) defines an appropriate range for the total angle of view 2ω of the optical system OL. By satisfying conditional expression (17), the effect of this embodiment can be made more certain.

[0081] The effect of this embodiment can be further ensured by setting the upper limit of conditional expression (17) to 13.00°, 12.00°, 11.00°, or even 10.00°.The effect of this embodiment can be further ensured by setting the lower limit of conditional expression (17) to 4.00°, 5.00°, or even 6.00°.

[0082] A manufacturing method for the optical system OL according to this embodiment will now be described with reference to FIG. 8. First, the lenses are arranged in the lens barrel so as to have, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2, and a third lens group G3 (Step ST1). Then, the second lens group G2 is configured to move along the optical axis during focusing (Step ST2). Furthermore, at least one negative lens L1n is arranged in the first lens group G1, and a first positive lens L1p satisfying conditional expression (1) is arranged closest to the object side of the first lens group G1 (Step ST3). Furthermore, the lenses are arranged in the lens barrel so as to satisfy at least conditional expression (2) (Step ST4). This manufacturing method makes it possible to manufacture an optical system that is lightweight and compact yet has excellent correction for various aberrations. [Example]

[0083] Optical systems OL according to examples of this embodiment will be described below with reference to the drawings. Figs. 1, 3, and 5 are cross-sectional views showing the configurations of optical systems OL {OL(1) to OL(3)} according to first to third examples. In Figs. 1, 3, and 5, the direction of movement of each lens group along the optical axis when focusing from infinity to a close-distance object is indicated by an arrow accompanied by the word "(focusing)." The direction of movement of the vibration-proof lens group is also indicated by an arrow accompanied by the symbol "Gvr."

[0084] 1, 3, and 5, the lens groups are represented by the symbols first lens group G1, second lens group G2, and third lens group G3, and each lens is represented by a number along with the symbol L, but each example represents a lens group independently, etc. Therefore, even if the same symbols are used between examples, this does not mean that the examples have the same configuration.

[0085] 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 (λ=587.6 nm), g-line (λ=435.8 nm), and C-line (λ=656.3 nm) were selected as the targets for calculating aberration characteristics.

[0086] In the [Overall Specifications] table, f is the focal length of the entire optical system, FNO is the F-number, ω is the half angle of view (unit: °), and Y is the image height. TL is the total length of the optical system, or more specifically, the distance from the lens surface closest to the object on the optical axis to the lens surface closest to the image plane when focused at infinity, plus the air-equivalent distance from the final lens surface on the optical axis to image plane I when focused at infinity. BF is the air-equivalent distance (back focus) from the final lens surface on the optical axis to image plane I when focused at infinity.

[0087] In the [Lens Specifications] table, the surface number indicates the order of the optical surfaces from the object side along the direction of light ray travel, R indicates the radius of curvature of each optical surface (a surface whose center of curvature is located on the image plane side has a positive value), D indicates the surface spacing, which is the distance on the optical axis from each optical surface to the next optical surface (or image plane), and nd indicates the refractive index of the material of the optical component, based on the d-line. For θgF, only the value of the lens corresponding to the first positive lens L1p required in the conditional formula is shown. The "∞" for the radius of curvature indicates a plane or an aperture, and (stop S) indicates the aperture stop. The refractive index of air, nd = 1.00000, is omitted.

[0088] The "Variable Distance Data" table shows the surface spacings listed for the surface numbers in the "Lens Specifications" table that have a "variable" surface spacing, and also shows the surface spacings when focused at infinity and when focused at close distances. Note that f represents the focal length of the entire lens system, and β represents the magnification. Also, D0 represents the distance from the object to the optical surface closest to the object in the optical system.

[0089] The [Lens Group Data] table shows the starting surface (the surface closest to the object) and focal length of each lens group.

[0090] In the following, for all specifications, the focal length, radius of curvature R, surface spacing D, and other lengths are generally expressed in "mm" unless otherwise specified, but this is not limited to this, as the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0091] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0092] (First Example) Example 1 will be described with reference to FIGS. 1, 2, and Table 1. FIG. 1 shows the lens configuration of an optical system according to Example 1. The optical system OL(1) according to Example 1 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 positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 moves toward the object side, changing the spacing between adjacent lens groups.

[0093] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a meniscus positive lens L11 with its convex surface facing the object side, a meniscus positive lens L12 with its convex surface facing the object side, a cemented lens of a biconvex positive lens L13 and a biconcave negative lens L14, and a meniscus positive lens L15 with its convex surface facing the object side.

[0094] The second lens group G2 is composed of a biconvex positive lens L21. When focusing from an object at infinity to an object at a close distance, the second lens group G2 moves toward the object.

[0095] The third lens group G3 is composed of, arranged along the optical axis from the object side, the following: a meniscus positive lens L31 with a convex surface facing the object side; a meniscus negative lens L32 with a convex surface facing the object side; a meniscus negative lens L33 with a convex surface facing the object side; a cemented lens of a meniscus positive lens L34 with a convex surface facing the image side and a biconcave negative lens L35; a cemented lens of a biconvex positive lens L36 and a meniscus negative lens L37 with a convex surface facing the image side; a biconvex positive lens L38; and a meniscus negative lens L39 with a convex surface facing the image side. An aperture stop S for adjusting the amount of light is located between the negative lens L32 and the negative lens L33.

[0096] In this embodiment, the positive lens L11 in the first lens group G1 corresponds to the first positive lens L1p, the positive lens L12 corresponds to the second positive lens L2p, the positive lens L13 corresponds to the third positive lens L3p, and the negative lens L14 corresponds to the negative lens L1n. Of these, the second positive lens L2p and the third positive lens L3p constitute a partial lens group Gp arranged adjacent to the image plane side of the first positive lens L1p. Furthermore, the negative lens L33 in the third lens group G3 and a cemented lens of a negative lens L34 and a negative lens L35 constitute an image-stabilizing lens group Gvr that is movable in a direction perpendicular to the optical axis and corrects displacement of the imaging position (image blur on the image plane I) due to camera shake or the like.

[0097] Table 1 below shows the values ​​of the specifications in the optical system according to the first example.

[0098] (Table 1) [Overall specifications] f=293.78 FNO=2.9 2ω=8.4 Y=21.6 TL=293.994 BF=57.074 [Lens specifications] Surface number RD nd νd θgF 1 253.4130 7.764 1.62200 30.66 0.6248 2 2337.0555 0.150 3 160.6925 9.366 1.43384 95.16 4 700.1842 86.595 5 125.7215 8.078 1.43384 95.16 6 -269.1282 2.299 1.85026 32.35 7 82.1140 1.824 8 128.9989 5.790 1.43384 95.16 9 2000.0210 Variable (D9) 10 82.6543 7.423 1.56732 42.58 11 -448.0608 Variable (D11) 12 31.6776 9.031 1.59319 67.90 13 233.5103 0.150 14 169.7612 1.500 1.78880 28.42 15 30.4517 20.911 16 ∞ 0.300 (Aperture) 17 120.3262 1.800 1.85026 32.35 18 42.8944 6.075 19 -90.8542 4.837 1.85000 27.03 20 -23.8556 1.800 1.79500 45.31 21 86.2883 2.197 22 105.1867 8.965 1.51823 58.82 23 -21.0773 1.500 1.62846 59.18 24 -79.8673 0.300 25 88.8785 7.340 1.73800 32.26 26 -51.3208 2.169 27 -44.6758 1.500 1.49782 82.57 28 -540.9290 BF [Variable Interval Data] Infinity focus Close focus f=293.776 β= -0.1727 D0 ∞ 1706.008 D9 34.258 13.750 D11 3.000 23.504 BF 57.074 57.074 [Lens group data] Group starting plane focal length G1 1 660.02 G2 10 123.62 G3 12 -233.47

[0099] FIG. 2 shows various aberration diagrams of the optical system according to Example 1 when focused at infinity. In each aberration diagram, FNO indicates the F-number, and Y indicates the image height. In each aberration diagram when focused at infinity, Y indicates the image height. In each aberration diagram, d indicates the aberration at the d-line (λ=587.6 nm), g indicates the aberration at the g-line (λ=435.8 nm), and C indicates the aberration at the C-line (λ=656.3 nm). In the aberration diagrams showing the curvature of field, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. In the distortion diagrams, distortion based on the d-line is shown. Note that the same symbols as in this example are used in the aberration diagrams of each Example shown below, and redundant explanations will be omitted.

[0100] From the various aberration diagrams, it can be seen that the optical system according to Example 1 has excellent correction of various aberrations and has excellent imaging performance.

[0101] (Second Example) Example 2 will be described with reference to FIGS. 3, 4, and Table 2. FIG. 3 is a diagram showing the lens configuration of an optical system according to Example 2. The optical system OL(2) according to Example 2 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 positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 moves toward the object side, changing the spacing between adjacent lens groups.

[0102] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a meniscus-shaped positive lens L11 with its convex surface facing the object side, a meniscus-shaped positive lens L12 with its convex surface facing the object side, and a cemented lens consisting of a biconvex positive lens L13 and a biconcave negative lens L14.

[0103] The second lens group G2 is composed of a meniscus-shaped positive lens L21 with its convex surface facing the object side. When focusing from an object at infinity to an object at a close distance, the second lens group G2 moves toward the object side.

[0104] The third lens group G3 is composed of, arranged along the optical axis from the object side, a biconcave negative lens L31, a biconvex positive lens L32, a meniscus negative lens L33 with its convex surface facing the object side, a cemented lens consisting of a meniscus positive lens L34 with its convex surface facing the image side and a biconcave negative lens L35, a biconvex positive lens L36, a meniscus positive lens L37 with its convex surface facing the object side, and a meniscus negative lens L38 with its convex surface facing the image side. An aperture diaphragm S for adjusting the amount of light is located between the positive lens L32 and the negative lens L33.

[0105] In this embodiment, the positive lens L11 in the first lens group G1 corresponds to the first positive lens L1p, the positive lens L12 corresponds to the second positive lens L2p, the positive lens L13 corresponds to the third positive lens L3p, and the negative lens L14 corresponds to the negative lens L1n. Of these, the second positive lens L2p and the third positive lens L3p form a partial lens group Gp arranged adjacent to the image plane side of the first positive lens L1p. Furthermore, the negative lens L33 and the cemented lens of the positive lens L34 and the negative lens L35 in the third lens group G3 form an image stabilization lens group Gvr that is movable in a direction perpendicular to the optical axis and corrects displacement of the imaging position (image blur on the image plane I) due to camera shake or the like.

[0106] Table 2 below shows the values ​​of the specifications in the optical system according to the second example.

[0107] (Table 2) [Overall specifications] f=293.81 FNO=2.9 2ω=8.4 Y=21.6 TL=294.060 BF=53.973 [Lens specifications] Surface number RD nd νd θgF 1 127.6089 10.619 1.66382 27.35 0.6319 2 401.0174 67.421 3 98.6642 8.563 1.43384 95.16 4 522.5091 3.000 5 69.5933 11.262 1.43384 95.16 6 -855.1277 2.503 1.80518 25.45 7 61.9968 Variable (D7) 8 80.7109 5.383 1.80100 34.92 9 372.3250 Variable (D9) 10 -125.5961 2.000 1.84666 23.80 11 98.6407 5.440 12 175.9735 5.966 1.69930 51.11 13 -89.7310 4.205 14 ∞ 13.895 (Aperture) 15 183.3048 1.800 1.85000 27.03 16 53.2944 7.597 17 -72.4068 4.887 1.89286 25.64 18 -29.9498 1.800 1.67790 55.35 19 170.3450 5.127 20 56.4004 5.419 1.61293 36.95 21 -136.1057 30.068 22 80.5120 3.708 1.73800 32.26 23 1511.2016 3.275 24 -46.6564 2.000 1.49782 82.57 25 -175.2232 BF [Variable Interval Data] Infinity focus Close focus f=293.809 β= -0.1731 D0 ∞ 1705.956 D7 25.430 10.320 D9 8.716 23.814 BF 53.973 53.973 [Lens group data] Group starting plane focal length G1 1 368.52 G2 8 127.60 G3 10 -242.87

[0108] 4 shows diagrams of various aberrations when the optical system according to Example 2 is focused at infinity. From these diagrams, it can be seen that the optical system according to Example 2 has excellent correction for various aberrations and has excellent imaging performance.

[0109] (Third Example) Example 3 will be described with reference to FIGS. 5, 6, and Table 3. FIG. 5 is a diagram showing the lens configuration of an optical system according to Example 3. The optical system OL(3) according to Example 3 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 positive refractive power, and a third lens group G3 having negative refractive power. When focusing from an object at infinity to a close object, the second lens group G2 moves toward the object side, changing the spacing between adjacent lens groups.

[0110] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a meniscus-shaped positive lens L11 with its convex surface facing the object side, a meniscus-shaped positive lens L12 with its convex surface facing the object side, a cemented lens of a meniscus-shaped positive lens L13 with its convex surface facing the object side and a meniscus-shaped negative lens L14 with its convex surface facing the object side, and a meniscus-shaped positive lens L15 with its convex surface facing the object side.

[0111] The second lens group G2 is composed of a meniscus-shaped positive lens L21 with its convex surface facing the object side. When focusing from an object at infinity to an object at a close distance, the second lens group G2 moves toward the object side.

[0112] The third lens group G3 is composed of, arranged along the optical axis from the object side, a meniscus positive lens L31 with a convex surface facing the object side, a meniscus negative lens L32 with a convex surface facing the object side, a meniscus negative lens L33 with a convex surface facing the object side, a cemented lens consisting of a meniscus positive lens L34 with a convex surface facing the image side and a biconcave negative lens L35, a biconvex positive lens L36, a meniscus positive lens L37 with a convex surface facing the image side, a meniscus negative lens L38 with a convex surface facing the image side, a biconvex positive lens L39, and a meniscus negative lens L40 with a convex surface facing the image side. An aperture stop S for adjusting the amount of light is located between the negative lens L32 and the negative lens L33.

[0113] In this embodiment, the positive lens L11 in the first lens group G1 corresponds to the first positive lens L1p, the positive lens L12 corresponds to the second positive lens L2p, the positive lens L13 corresponds to the third positive lens L3p, and the negative lens L14 corresponds to the negative lens L1n. Of these, the second positive lens L2p and the third positive lens L3p constitute a partial lens group Gp arranged adjacent to the image plane side of the first positive lens L1p. Furthermore, the negative lens L33 in the third lens group G3 and a cemented lens of a positive lens L34 and a negative lens L35 constitute an image-stabilizing lens group Gvr that is movable in a direction perpendicular to the optical axis and corrects displacement of the imaging position (image blur on the image plane I) due to camera shake or the like.

[0114] Table 3 below shows the values ​​of the specifications of the optical system according to the third example.

[0115] (Table 3) [Overall specifications] f=293.64 FNO=2.9 2ω=8.4 Y=21.6 TL=240.156 BF=36.766 [Lens specifications] Surface number RD nd νd θgF 1 154.6944 9.740 1.66382 27.35 0.6319 2 588.4165 0.218 3 85.7690 13.376 1.43384 95.16 4 236.4474 33.466 5 76.0502 9.725 1.43384 95.16 6 419.5661 2.596 1.78880 28.42 7 54.8249 3.269 8 84.3365 6.229 1.43384 95.16 9 201.9139 Variable (D9) 10 76.3027 5.034 1.62846 59.18 11 234.3750 Variable (D11) 12 31.3023 7.593 1.51742 52.20 13 113.6663 0.150 14 104.9554 1.500 1.84666 23.80 15 29.4086 18.158 16 ∞ 0.300 (Aperture) 17 198.4446 1.800 1.83481 42.73 18 47.5466 2.923 19 -75.9021 3.463 1.80518 25.45 20 -32.0573 1.800 1.79500 45.31 21 218.8230 2.065 22 60.4132 3.579 1.80518 25.45 23 -604.9868 15.205 24 455.8002 6.503 1.55298 55.07 25 -26.1964 0.188 26 -26.0899 1.800 1.62846 59.18 27 -283.3974 17.546 28 130.9733 5.893 1.68376 37.64 29 -101.7497 4.140 30 -51.4337 1.500 1.49782 82.57 31 -112.6706 BF [Variable Interval Data] Infinity focus Close focus f=293.638 β=-0.1698 D0 ∞ 1759.846 D9 20.630 3.000 D11 3.000 20.628 BF 36.766 36.766 [Lens group data] Group starting plane focal length G1 1 242.88 G2 10 177.83 G3 12 -314.008

[0116] 6 shows diagrams of various aberrations when the optical system according to Example 3 is focused at infinity. From these diagrams, it can be seen that the optical system according to Example 3 has excellent correction for various aberrations and has excellent imaging performance.

[0117] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below: This table shows the values ​​corresponding to each of the conditional expressions (1) to (17) for all the examples (Examples 1 to 3). Conditional expression (1)0.023×νdL1p+ndL1p<2.500 Condition (2) 0.600 <TL / f<1.200 Conditional expression (3)0.590<θgFL1p<0.800 Conditional expression (4) νdL1p<40.00 Condition (5) 1.450 <ndL1n<1.950 Conditional expression (6)20.00<νdL1n<40.00 Conditional expression (7)ndL2p<1.750 Conditional expression (8) 80.00<νdL2p Condition (9) 0.200 <f2 / f<1.000 Condition (10) 1.500 <ndLp<1.900 Conditional expression (11) 30.00<νdLp<70.00 Condition (12) 0.500 <f1 / f<2.800 Conditional expression (13)0.400<(-f3) / f<2.000 Condition (14) 0.0000 <d1 / TL1<0.8000 Conditional expression (15) 0.400<(L3R2-L3R1) / (L3R2+L3R1)<3.500 Condition (16) 0.000 <dS / TLs<0.600 Conditional expression (17) 3.00°<2ω<14.00°

[0118] [Conditional Expression Corresponding Values] (First to Third Examples) Conditional Expression First Example Second Example Third Example (1) 2.3271 2.2928 2.2928 (2) 1.0007 1.0009 0.8179 (3) 0.6248 0.6319 0.6319 (4) 30.657 27.347 27.347 (5) 1.8503 1.8052 1.7888 (6) 32.353 25.448 28.417 (7) 1.4338 1.4338 1.4338 (8) 95.163 95.163 95.163 (9) 0.4208 0.4343 0.6056 (10) 1.5673 1.8010 1.6285 (11) 42.578 34.923 59.175 (12) 2.2467 1.2543 0.8271 (13) 0.7947 0.8266 1.0694 (14) 0.00123 0.65223 0.00277 (15) 2.7534 1.1772 0.6931 (16) 0.0031 0.1040 0.0028 (17) 8.404 8.404 8.404

[0119] As described above, according to each embodiment, it is possible to realize an optical system and optical equipment that is lightweight and small, yet has good optical performance.

[0120] In the above-described embodiment, the following contents can be appropriately adopted within the scope that does not impair the optical performance.

[0121] Although a three-group configuration has been shown as an example of the optical system of this embodiment, the present application is not limited to this, and optical systems with other group configurations (for example, four groups, five groups, etc.) can also be configured. Specifically, a configuration in which a lens or lens group is added to the most object side or the most image side of the optical system of this embodiment can also be used. A configuration in which a second focusing lens group is added in addition to one focusing lens group can also be used. Note that a lens group refers to a portion having at least one lens separated by an air gap that changes during focusing.

[0122] The lens surface may be spherical, flat, or aspherical. Spherical or flat lens surfaces are preferred because they facilitate lens processing and assembly adjustment, and prevent degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, they are preferred because they minimize degradation of imaging performance even when the image plane is misaligned.

[0123] If the lens surface is aspherical, the aspherical surface may be any of the following: a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, or a hybrid aspherical surface in which a resin is formed into an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, or the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0124] The aperture diaphragm may not be provided as a component, and the lens frame may play the role of the aperture diaphragm.

[0125] Each lens surface may be coated with an anti-reflection coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high-contrast optical performance. [Explanation of symbols]

[0126] OL optical system G1 First lens group G2 Second lens group G3 Third lens group L1p 1st positive lens L2p 2nd positive lens L3p Third positive lens L1n Negative lens Gvr vibration-proof lens group S Aperture stop I Image plane

Claims

1. The optical system has a first lens group having positive refractive power, a second lens group, and a third lens group arranged in this order from the object side along an optical axis, During focusing, the second lens group moves along the optical axis, the first lens group has at least one negative lens and a first positive lens arranged closest to the object in the first lens group, The first positive lens satisfies the following condition: 0.023×νdL1p+ndL1p<2.500 where ndL1p is the refractive index of the first positive lens with respect to the d-line. νdL1p: Abbe number of the first positive lens based on the d line Furthermore, the optical system satisfies the following conditional expression: 0.600<TL / f<1.200 where TL is the distance on the optical axis from the lens surface closest to the object in the optical system to the image plane. f: focal length of the entire optical system

2. 2. The optical system according to claim 1, wherein the first positive lens satisfies the following condition: 1<f<1 / ... 0.590<θgFL1p<0.800 νdL1p<40.00 where θgFL1p is the partial dispersion ratio of the first positive lens, and is defined by the following formula when the refractive index of the first positive lens for the g-line is ngL1p, the refractive index of the first positive lens for the F-line is nFL1p, and the refractive index of the first positive lens for the C-line is nCL1p. θgFL1p=(ngL1p-nFL1p) / (nFL1p-nCL1p)

3. 3. The optical system according to claim 1, wherein the at least one negative lens in the first lens group satisfies the following condition: 1<n<1 / ... 1.450<ndL1n<1.950 20.00<νdL1n<40.00 where νdL1n is the Abbe number of the at least one negative lens in the first lens group, with reference to the d-line. ndL1n: the refractive index of the at least one negative lens in the first lens group with respect to the d-line

4. The optical system according to any one of claims 1 to 3, wherein the first lens group includes a partial lens group composed of a positive lens arranged adjacent to the image plane side of the first positive lens, and the partial lens group is arranged closer to the object side than the negative lens in the first lens group.

5. The optical system according to any one of claims 1 to 4, wherein the first lens group includes a partial lens group composed of a positive lens that is arranged adjacent to the image surface side of the first positive lens, and a second positive lens that is arranged closest to the object side in the partial lens group satisfies the following conditional expression: ndL2p<1.750 80.00<νdL2p where ndL2p is the refractive index of the second positive lens with respect to the d-line. νdL2p: Abbe number of the second positive lens based on the d line

6. The optical system according to any one of claims 1 to 5, wherein the first lens group includes a second positive lens that is arranged adjacent to the image surface side of the first positive lens, and a third positive lens that is arranged adjacent to the image surface side of the second positive lens.

7. 7. The optical system according to claim 1, wherein the following condition is satisfied: 0.200<f2 / f<1.000 where f2 is the focal length of the second lens group f: focal length of the entire optical system

8. 8. The optical system according to claim 1, wherein the second lens group has a positive lens that satisfies the following condition: 1 / (f<f<1 / ... 1.500<ndLp<1.900 30.00<νdLp<70.00 where ndLp is the refractive index of the positive lens in the second lens group with respect to the d-line. νdLp: Abbe number of the positive lens in the second lens group with reference to the d-line

9. 9. The optical system according to claim 1, wherein the second lens group is made up of one single lens.

10. 10. The optical system according to claim 1, wherein the second lens group moves toward the object side during focusing.

11. The optical system according to any one of claims 1 to 10, which satisfies the following conditional expression: 0.500<f1 / f<2.800 where f1 is the focal length of the first lens group f: focal length of the entire optical system

12. 12. The optical system according to claim 1, wherein the following condition is satisfied: 0.400<(-f3) / f<2.000 where f3 is the focal length of the third lens group f: focal length of the entire optical system

13. The optical system according to any one of claims 1 to 12, wherein the first lens group includes a partial lens group composed of a positive lens arranged adjacent to the image surface side of the first positive lens, and a second positive lens is arranged closest to the object side in the partial lens group, and the following conditional expression is satisfied: 0.0000<d1 / TL1<0.8000 where d1 is the distance on the optical axis from the lens surface of the first positive lens on the image plane side to the lens surface of the second positive lens on the object side. TL1: the distance on the optical axis from the lens surface in the first lens group closest to the object to the lens surface in the first lens group closest to the image plane

14. The first lens group includes a second positive lens that is arranged adjacent to the image surface side of the first positive lens, and a third positive lens that is arranged adjacent to the image surface side of the second positive lens, and satisfies the following conditional expression: 0.400<(L3R2-L3R1) / (L3R2+L3R1)<3.500 where L3R1 is the radius of curvature of the object-side lens surface of the third positive lens. L3R2: radius of curvature of the image-side lens surface of the third positive lens

15. 15. The optical system according to claim 1, wherein the third lens group includes, in order from the object side, at least one lens, a diaphragm, and an image stabilization lens group that corrects an image formed on an image plane by moving in a direction perpendicular to the optical axis.

16. 16. The optical system according to claim 15, wherein the following condition is satisfied: 0.000<dS / TLs<0.600 where dS is the distance on the optical axis from the stop to the lens surface closest to the object in the vibration reduction lens group. TLs: distance on the optical axis from the stop to the image plane

17. 17. The optical system according to claim 1, wherein the following condition is satisfied: 3.00°<2ω<14.00° where 2ω is the total angle of view of the optical system.

18. An optical device equipped with the optical system according to any one of claims 1 to 17.

19. The optical system has a first lens group having positive refractive power, a second lens group, and a third lens group arranged in this order from the object side along an optical axis, During focusing, the second lens group moves along the optical axis, a manufacturing method for an optical system in which the first lens group has at least one negative lens, and a first positive lens is disposed closest to the object side of the first lens group, The first positive lens satisfies the following condition: 0.023×νdL1p+ndL1p<2.500 where ndL1p is the refractive index of the first positive lens with respect to the d-line. νdL1p: Abbe number of the first positive lens based on the d line Furthermore, a manufacturing method of an optical system in which each lens is arranged in a lens barrel so as to satisfy the following conditional expression: 0.600<TL / f<1.200 where TL is the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane. f: focal length of the entire optical system

Images