Optical system and imaging device

Abstract

To provide a compact optical system capable of effectively correcting various aberrations. [Solution] The optical system consists of a front lens group GF with positive refractive power, an intermediate lens group GM with positive refractive power, and a rear lens group GR with negative refractive power. The intermediate lens group moves during focusing. The front lens group has the positive lens closest to the object. The rear lens group has the negative lens closest to the image. The total number of lenses included in the optical system is 12 or less. When Bf is the air-equivalent distance on the optical axis from the lens surface closest to the image to the image plane, fM is the focal length of the intermediate lens group when focused on an object at infinity, and f is the focal length of the optical system when focused on an object at infinity, the conditions 0.03 ≤ Bf / f ≤ 0.38 and 0.30 ≤ fM / f ≤ 0.85 are satisfied.

Description

[Technical Field]

[0001] This invention relates to an optical system suitable for imaging. [Background technology]

[0002] The optical system, as disclosed in Patent Document 1, consists of a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, with only the intermediate lens group moving during focusing. In this optical system, the front lens group has a positive lens closest to the object, the rear lens group has a negative lens closest to the image, and the total number of lenses in the entire optical system is 12 or less. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Patent Publication No. 2017-0130571 [Overview of the project] [Problems that the invention aims to solve]

[0004] As described above, there is a need for an optical system that is compact and capable of effectively correcting various aberrations such as chromatic aberration and field curvature. [Means for solving the problem]

[0005] One aspect of the present invention is an optical system composed of a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side. During focusing, the front and rear lens groups do not move, but the intermediate lens group moves, changing the spacing between adjacent lens groups. Each of the front, intermediate, and rear lens groups contains multiple lenses. The front lens group has the positive lens closest to the object. The rear lens group has the negative lens closest to the image. The total number of lenses included in the optical system is 12 or less. When Bf is the air-equivalent distance on the optical axis from the lens surface closest to the image to the image plane, fM is the focal length of the intermediate lens group when focused on an object at infinity, and f is the focal length of the optical system when focused on an object at infinity, 0.03 ≤ Bf / f ≤ 0.38 0.30 ≤ fM / f ≤ 0.85 It is characterized by satisfying the following conditions.

[0006] Another aspect of the present invention is an optical system composed of a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side. During focusing, the front and rear lens groups do not move, but the intermediate lens group moves, changing the spacing between adjacent lens groups. Each of the front, intermediate, and rear lens groups contains multiple lenses. The front lens group has the positive lens closest to the object. The total number of lenses included in the optical system is 13 or less. When Bf is the air-equivalent distance on the optical axis from the lens surface closest to the image to the image plane, fM is the focal length of the intermediate lens group when focused on an object at infinity, f is the focal length of the optical system when focused on an object at infinity, and F is the aperture F-number of the optical system, 0.03 ≤ Bf / f ≤ 0.38 0.30 ≤ fM / f ≤ 0.85 1.00 ≤ F ≤ 1.85 It is characterized by satisfying the following conditions. Furthermore, an imaging device equipped with the above optical systems also constitutes another aspect of the present invention. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical system that is small in size and can satisfactorily correct various aberrations.

Brief Description of the Drawings

[0008] [Figure 1] Cross-sectional view of the optical system of Example 1. [Figure 2] Aberration diagram of the optical system of Example 1. [Figure 3] Cross-sectional view of the optical system of Example 2. [Figure 4] Aberration diagram of the optical system of Example 2. [Figure 5] Cross-sectional view of the optical system of Example 3. [Figure 6] Aberration diagram of the optical system of Example 3. [Figure 7] Cross-sectional view of the optical system of Example 4. [Figure 8] Aberration diagram of the optical system of Example 4. [Figure 9] Cross-sectional view of the optical system of Example 5. [Figure 10] Aberration diagram of the optical system of Example 5. [Figure 11] Cross-sectional view of the optical system of Example 6. [Figure 12] Aberration diagram of the optical system of Example 6. [Figure 13] Cross-sectional view of the optical system of Example 7. [Figure 14] Aberration diagram of the optical system of Example 7. [Figure 15] Cross-sectional view of the optical system of Example 8. [Figure 16] Aberration diagram of the optical system of Example 8. [Figure 17] Cross-sectional view of the optical system of Example 9. [Figure 18] Aberration diagram of the optical system of Example 9. [Figure 19] Cross-sectional view of the optical system of Example 10. [Figure 20] Aberration diagram of the optical system of Example 10. [Figure 21] Cross-sectional view of the optical system of Example 11. [Figure 22] Aberration diagram of the optical system of Example 11. [Figure 23]Cross-sectional view of the optical system of Example 12. [Figure 24] Aberration diagram of the optical system in Example 12. [Figure 25] Cross-sectional view of the optical system of Example 13. [Figure 26] Aberration diagram of the optical system in Example 13. [Figure 27] Cross-sectional view of the optical system of Example 14. [Figure 28] Aberration diagram of the optical system in Example 14. [Figure 29] Cross-sectional view of the optical system of Example 15. [Figure 30] Aberration diagram of the optical system in Example 15. [Figure 31] Cross-sectional view of the optical system of Example 16. [Figure 32] Aberration diagram of the optical system in Example 16. [Figure 33] Cross-sectional view of the optical system of Example 17. [Figure 34] Aberration diagram of the optical system in Example 17. [Figure 35] Cross-sectional view of the optical system of Example 18. [Figure 36] Aberration diagram of the optical system in Example 18. [Figure 37] A schematic diagram of an imaging device equipped with the optical system of each embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] Figures 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, and 35 show cross-sections of the optical systems of Examples 1 to 18 in a state where they are in focus on an object at infinity (hereinafter referred to as the infinity focus state). The optical systems of each example are used as imaging optical systems in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras.

[0011] In each cross-sectional view, the left side is the object side (front side), and the right side is the image side (rear side). The optical system of each embodiment has a plurality of lens groups arranged sequentially from the object side to the image side, including a front lens group GF with positive refractive power, an intermediate lens group GM with positive refractive power, and a rear lens group GR with negative refractive power. A lens group is a collection of one or more lenses that move or remain together during focusing, and the spacing between adjacent lens groups changes during focusing.

[0012] In each embodiment, the front lens group GF and the rear lens group GR do not move during focusing, but the intermediate lens group GM moves. As shown by the arrows in each figure, the intermediate lens group GM moves toward the object when focusing from infinity to near. Note that the intermediate lens group GM may move as a whole during focusing, or multiple subgroups (focus groups) divided within the intermediate lens group may move along different trajectories. In embodiments 11, 12, 13, 15, and 16, the object-side focus group GM1 and the image-side focus group GM2 within the intermediate lens group GM move along different trajectories during focusing.

[0013] SP is the aperture diaphragm. IMG is the image plane. The image plane IMG is where the imaging surface (light-receiving surface) of an image sensor such as a CCD sensor or CMOS sensor, or the film surface (photosensitive surface) of a silver halide film is placed. In each embodiment, the optical system may have an optical block (parallel plate, etc.) that does not have refractive power, such as an optical filter or cover glass, placed between the lens surface closest to the image and the image plane IMG.

[0014] The characteristics of the optical systems in each embodiment will be described below.

[0015] In the optical system of each embodiment, the front lens group GF, the intermediate lens group GM, and the rear lens group GR each contain multiple lenses. The lens closest to the object in the front lens group GF is a positive lens, and the lens closest to the image plane in the rear lens group GR is a negative lens. Furthermore, the total number of lenses in the entire optical system is 12 or less. In this configuration, let Bf be the air-equivalent distance (back focus) on the optical axis from the lens surface closest to the image plane (final surface) of the optical system to the image plane IMG, let fM be the focal length of the intermediate lens group GM when it is in focus at infinity, and let f be the focal length of the optical system when it is in focus at infinity. At this time, at least one of the following conditions (1) and (2) is satisfied.

[0016] 0.03 ≤ Bf / f ≤ 0.38 (1) 0.30 ≤ fM / f ≤ 0.85 (2) Furthermore, in the optical systems of each embodiment, the front lens group GF, the intermediate lens group GM, and the rear lens group GR each contain multiple lenses. The lens closest to the object in the front lens group GF is a positive lens, and the total number of lenses in the entire optical system is 13 or less. In this configuration, let Bf be the back focus from the final surface of the optical system to the image plane IMG, fM be the focal length of the intermediate lens group GM when it is in focus at infinity, f be the focal length of the optical system when it is in focus at infinity, and F be the maximum aperture F number of the optical system. At this time, at least one of the following conditions (1), (2), and (3) is satisfied.

[0017] 0.03 ≤ Bf / f ≤ 0.38 (1) 0.30 ≤ fM / f ≤ 0.85 (2) 1.00 ≤ F ≤ 1.85 (3) The conditions in equation (1) indicate an appropriate relationship between the back focus and focal length of the optical system. If Bf / f falls below the lower limit of equation (1), the angle of incidence of light rays to the image sensor positioned on the image plane IMG becomes too large, making it difficult to receive light on the image sensor, which is undesirable. If Bf / f exceeds the upper limit of equation (1), it is not possible to adopt an appropriate lens arrangement to correct chromatic aberration in the region of high image height, resulting in insufficient correction of chromatic aberration, which is also undesirable.

[0018] Furthermore, it is more preferable to set the lower limit of formula (1) to 0.05, 0.08, 0.10, 0.12, or 0.13. Also, it is more preferable to set the upper limit of formula (1) to 0.35, 0.30, 0.25, 0.20, or 0.15.

[0019] The conditions in equation (2) indicate an appropriate relationship between the focal length of the intermediate lens group GM and the focal length of the entire optical system. If fM / f falls below the lower limit of equation (2), the power of the intermediate lens group GM becomes too strong, which is undesirable because it increases the fluctuations in spherical aberration, coma aberration, and field curvature during focusing. If fM / f exceeds the upper limit of equation (2), the power of the intermediate lens group GM becomes too weak, which increases the amount of movement of the intermediate lens group GM during focusing and lengthens the overall length of the optical system, which is also undesirable.

[0020] Furthermore, it is more preferable to set the lower limit of equation (2) to 0.40, 0.50, 0.55, 0.60, or 0.70. Also, it is more preferable to set the upper limit of equation (2) to 0.80, 0.77, or 0.75.

[0021] The conditions in equation (3) indicate an appropriate range for the aperture F-number of the optical system. The optical systems in each embodiment are small, large-aperture medium telephoto optical systems. If F exceeds the upper limit of equation (3), the optical system becomes too large relative to the aperture, which is undesirable. If F falls below the lower limit of equation (3), spherical aberration cannot be adequately corrected, which is also undesirable.

[0022] It is more preferable to set the lower limit of equation (3) to 1.10, 1.20, or 1.30. It is also more preferable to set the upper limit of equation (2) to 1.70, 1.60, or 1.50.

[0023] The following describes the configurations that are preferable to satisfy in the optical system of each embodiment.

[0024] In the front lens group GF, the positive lens closest to the object is preferably a meniscus lens with its convex surface facing the object. In large-aperture, medium-telephoto optical systems, the refractive power of the optical system as a whole is relatively weak, but if an extremely powerful lens is placed within it, correcting aberrations becomes difficult. For this reason, in the front lens group GF, it is desirable to use a meniscus lens with its convex surface facing the object to gently refract the light rays.

[0025] For similar reasons, it is preferable that the second lens positioned from the object side is a meniscus lens with its convex surface facing the object side. Similarly, it is preferable that the third lens positioned from the object side is a meniscus lens with its convex surface facing the object side. Furthermore, it is preferable that the fourth lens positioned from the object side is a meniscus lens with its convex surface facing the object side.

[0026] Furthermore, it is preferable that the total number of lenses in the front lens group GF be 5 or less. Generally, increasing the number of lenses allows for better aberration correction, but on the other hand, it increases the size and weight of the optical system. By limiting the number of lenses in the front lens group GF to 5 or less in each embodiment, a compact, large-aperture medium telephoto optical system can be realized more effectively. For the same reason, it is preferable that the total number of lenses in the intermediate lens group GM be 4 or less, and the total number of lenses in the rear lens group GR be 5 or less.

[0027] It is preferable that each of the front lens group GF, the intermediate lens group GM, and the rear lens group GR has at least one positive lens and at least one negative lens. In order to properly correct field curvature and chromatic aberration regardless of the object distance of the subject, it is necessary to suppress the amount of aberration generated within each lens group. In this case, if there is not at least one positive lens and one negative lens, it is difficult to correct aberrations within the lens group.

[0028] Furthermore, it is preferable that the front lens group GF includes at least two positive lenses with an Abbe number of 60 or higher relative to the d-line. In large-aperture medium telephoto optical systems, the front lens group GF, which has a high axial ray height, contributes most significantly to axial chromatic aberration, and therefore it is particularly important to correct chromatic aberration well in the front lens group GF. For this reason, it is preferable that the front lens group GF has at least two positive lenses made of low-dispersion glass.

[0029] Furthermore, it is preferable that the intermediate lens group GM includes at least one aspherical lens. In order to effectively correct spherical aberration and coma aberration regardless of the object distance of the subject, placing an aspherical lens in the intermediate lens group GM, which is near the aperture diaphragm SP and moves during focusing, allows for effective suppression of aberrations.

[0030] Furthermore, from the viewpoint of correcting field curvature, it is preferable to position the aperture diaphragm SP between the front lens group GF and the intermediate lens group GM. This is because, in terms of its contribution to the overall size of the optical system, it is best to position the aperture diaphragm SP near the center. In addition, by positioning the aperture diaphragm SP closer to the object than the intermediate lens group GM, which moves during focusing, the radial size of the intermediate lens group GM can be suppressed.

[0031] Furthermore, it is preferable that the refractive index of at least one positive lens included in the rear lens group GR is 1.850 or less on the d line and the Abbe number with respect to the d line is 50.0 or less. This makes it easier to correct chromatic aberration even in optical systems using a relatively small number of lenses, and reduces aberration fluctuations during focusing.

[0032] Furthermore, the intermediate lens group GM preferably includes an object-side focus group GM1 and an image-side focus group GM2, and it is preferable that these move along different trajectories during focusing. By appropriately moving these object-side and image-side focus groups GM1 and GM2, respectively, it is possible to suppress fluctuations in the performance of the optical system due to changes in the object distance. It is also preferable that the object-side and image-side focus groups GM1 and GM2 have positive refractive power and positive refractive power, or negative refractive power and positive refractive power, respectively. This further suppresses fluctuations in the performance of the optical system due to changes in the object distance. In each embodiment, the object-side focus group GM1 and the image-side focus group GM2 move towards the object along different trajectories during focusing from infinity to near.

[0033] The following describes conditions that are preferable to further satisfy for the optical systems of each embodiment. In the optical systems of each embodiment, the focal length of the front lens group GF is fF, the focal length of the intermediate lens group GM is fM, and the focal length of the rear lens group GR is fR. For at least one negative lens included in the front lens group GF, the refractive index at the d line is nd_Fn, the Abbe number with respect to the d line is νd_Fn, and the partial dispersion ratio at the g line and F line is θgF_Fn, ×10 -X Let EX be the value. For the negative lens located furthest from the image side in the rear lens group GR, let νd_Rn1 be the Abbe number with respect to the d line, and θgF_Rn1 be the partial dispersion ratio between the g line and the F line. For the negative lens located second from the image side in the rear lens group GR, let νd_Rn2 be the Abbe number with respect to the d line, and θgF_Rn2 be the partial dispersion ratio between the g line and the F line.

[0034] Let βM be the lateral magnification of the intermediate lens group GM at infinity focus, and βR be the lateral magnification of the rear lens group GR at infinity focus. Let dsp_R be the distance along the optical axis from the aperture diaphragm SP to the image plane IMG, and let fF_n1 be the focal length of the negative lens with the strongest refractive power among the at least one negative lens included in the front lens group GF. Let fFM be the combined focal length of the front lens group GF and the intermediate lens group GM at infinity focus, and fMR be the combined focal length of the intermediate lens group GM and the rear lens group GR at infinity focus.

[0035] Let fRn1 be the focal length of the negative lens located furthest towards the image in the rear lens group GR, fFp1 be the focal length of the positive lens located furthest towards the object in the front lens group GF, and fFp2 be the focal length of the second positive lens located furthest from the object in the front lens group GF. The length (total optical length) of the optical system is defined as the distance along the optical axis from the lens surface furthest towards the object (frontmost) to the final surface, plus the aforementioned back focus Bf.

[0036] In this case, it is preferable that the optical system of each embodiment satisfies at least one of the following conditions (4) to (7).

[0037] 1.00 ≤ fF / f ≤ 5.00 (4) -100.00 ≤ fR / f ≤ -0.30 (5) 1.20 ≤ fF / fM ≤ 7.00 (6) -100.00 ≤ fR / fM ≤ -0.80 (7) Furthermore, it is preferable that the optical system of each embodiment satisfies at least one set of conditions from the following sets of conditions: the set of three conditions in formulas (8), (9), and (10); the set of two conditions in formulas (11) and (12); and the set of two conditions in formulas (13) and (14).

[0038] 1.50≦nd_Fn≦2.35-0.015×νd_Fn (8) 20.0 ≤ νd_Fn ≤ 60.0 (9) -0.100≦θgF_Fn-(-9.529E-8×νd_Fn 3 +3.694E-5×νd_Fn 2 -4.717E-3×νd_Fn+7.139E-1)≦0.000 (10) 15.0 ≤ νd_Rn1 ≤ 55.0 (11) -0.010≦θgF_Rn1-(-9.529E-8×νd_Rn1 3 +3.694E-5×νd_Rn1 2 -4.717E-3×νd_Rn1+7.139E-1)≦0.050 (12) 15.0 ≤ νd_Rn2 ≤ 55.0 (13) -0.010 ≤ θgF_Rn2 - (-9.529E-8 × νd_Rn2 3 + 3.694E-5 × νd_Rn2 2 - 4.717E-3 × νd_Rn2 + 7.139E-1) ≤ 0.050 (14) Furthermore, the optical system of each embodiment preferably satisfies at least one of the conditions of the following formulas (15) to (25).

[0039] 0.20 ≤ βM ≤ 1.00 (15) 0.50 ≤ βR ≤ 2.00 (16) 0.30 ≤ (1 - βM 2 ) × βR 2 ≤ 2.00 (17) 0.50 ≤ dsp_R / f ≤ 2.00 (18) -0.80 ≤ fF_n1 / f ≤ -0.20 (19) 0.40 ≤ fFM / f ≤ 1.50 (20) 0.40 ≤ fMR / f ≤ 1.50 (21) -5.00 ≤ fRn1 / f ≤ -0.30 (22) 1.20 ≤ fFp1 / f ≤ 10.00 (23) 0.30 ≤ fFp2 / f ≤ 2.00 (24) 0.80 ≤ TTL / f ≤ 2.00 (25) The condition of formula (4) shows an appropriate relationship between the focal length of the front lens group GF and the focal length of the entire optical system. If fF / f is below the lower limit of formula (4), the power of the front lens group GF becomes too strong, making it difficult to correct spherical aberration, coma aberration, and axial chromatic aberration, which is not preferable. If fF / f exceeds the upper limit of formula (4), the power of the front lens group GF becomes too weak, making it difficult to correct spherical aberration, coma aberration, and axial chromatic aberration, which is not preferable.

[0040] It is more preferable that the lower limit of formula (4) is 1.10, 1.20, 1.30, or 1.40. It is more preferable that the upper limit of formula (4) is 4.50, 4.00, 3.50, 3.00, 2.50, or 2.00.

[0041] The conditions in equation (5) indicate an appropriate relationship between the focal length of the rear lens group GR and the focal length of the entire optical system. If fR / f falls below the lower limit of equation (5), it is undesirable because the power of the rear lens group GR becomes too strong, making it difficult to correct distortion and chromatic aberration, and the angle of incidence of light rays to the image plane IMG becomes too large. If fR / f exceeds the upper limit of equation (5), it is undesirable because the power of the rear lens group GR becomes too weak, making it difficult to correct coma aberration, chromatic aberration, and Petzval sum.

[0042] Furthermore, it is more preferable to set the lower limit of equation (5) to -70.00, -50.00, -25.00, or -10.0. Also, it is more preferable to set the upper limit of equation (5) to -4.00, -0.50, -0.60, -0.70, or -0.80.

[0043] The conditions in equation (6) indicate an appropriate relationship between the focal lengths of the front lens group GF and the intermediate lens group GM. If fF / fM falls below the lower limit of equation (6), the power of the intermediate lens group GM becomes too weak, resulting in a large amount of movement of the intermediate lens group GM during focusing and an increase in the overall length of the optical system, which is undesirable. If fF / fM exceeds the upper limit of equation (6), the power of the front lens group GF becomes too weak, making it difficult to correct spherical aberration, coma aberration, and axial chromatic aberration, which is also undesirable.

[0044] Furthermore, it is more preferable to set the lower limit of formula (6) to 1.40, 1.50, 1.60, 1.70, or 1.80. Also, it is more preferable to set the upper limit of formula (6) to 6.00, 5.00, 4.00, 3.50, or 3.30.

[0045] The conditions in equation (7) indicate an appropriate relationship between the focal lengths of the intermediate lens group GM and the rear lens group GR. If fR / fM falls below the lower limit of equation (7), the power of the rear lens group GR becomes too weak, making it difficult to correct coma aberration, chromatic aberration, and Petzval sum, which is undesirable. If fR / fM exceeds the upper limit of equation (7), the power of the rear lens group GR becomes too strong, making it difficult to correct distortion aberration and chromatic aberration, and the angle of incidence of light rays to the image plane IMG becomes too large, which is also undesirable.

[0046] Furthermore, it is more preferable to set the lower limit of equation (7) to -50.00, -30.00, -20.00, -10.00, -5.00, or -4.00. Also, it is more preferable to set the upper limit of equation (7) to -1.00, -1.30, -1.50, -1.60, or -1.70.

[0047] The conditions in equations (8), (9), and (10) indicate an appropriate range for the refractive index, Abbe number, and partial dispersion ratio of at least one negative lens in the front lens group GF. If nd_Fn falls below the lower limit of equation (8), it is undesirable because the curvature of the negative lens becomes too strong, making it difficult to suppress spherical aberration and coma aberration. If nd_Fn falls below the upper limit of equation (8), it is undesirable because the Petzval sum of the optical system increases to the positive side, making it difficult to correct field curvature. If νd_Fn falls below the lower limit of equation (9), it is undesirable because it becomes difficult to correct chromatic aberration and field curvature. If νd_Fn exceeds the upper limit of equation (9), it is undesirable because chromatic aberration and field curvature become overcorrected. If the value in equation (10) falls below the lower limit, it is undesirable because chromatic aberration of the g line becomes overcorrected. If the value of equation (10) exceeds the upper limit, the chromatic aberration of the g line will be insufficiently corrected, which is undesirable.

[0048] Furthermore, it is more preferable to set the lower limit of equation (8) to 1.52, 1.55, 1.59, 1.61, or 1.63. It is even more preferable to set the upper limit of equation (8) to 2.34-0.015×νdb1n, 2.33-0.015×νdb1n, 2.32-0.015×νdb1n, or 2.30-0.015×νdb1n.

[0049] Furthermore, it is more preferable to set the lower limit of equation (9) to 21.0, 22.0, 23.0, 24.0, or 24.5. It is also more preferable to set the upper limit of equation (9) to 55.0, 50.0, 45.0, 40.0, or 38.0.

[0050] Furthermore, it is preferable to set the lower limit of equation (10) to -0.050, -0.030, -0.010, -0.0095, or -0.009. It is also preferable to set the upper limit of equation (10) to -0.002, -0.003, -0.004, or -0.005.

[0051] The conditions in equations (11) and (12) indicate an appropriate range for the Abbe number and partial dispersion ratio of the negative lens located furthest to the image side in the rear lens group GR. If νd_Rn1 falls below the lower limit of equation (11), it is undesirable because it becomes difficult to correct chromatic aberration and field curvature. If νd_Rn1 exceeds the upper limit of equation (11), it is undesirable because chromatic aberration and field curvature are overcorrected. If the value in equation (12) falls below the lower limit, it is undesirable because the chromatic aberration of the g line is overcorrected. If the value in equation (12) exceeds the upper limit, it is undesirable because the chromatic aberration of the g line is undercorrected.

[0052] Furthermore, it is more preferable to set the lower limit of formula (11) to 17.0, 20.0, 25.0, 27.0, or 30.0. It is also more preferable to set the upper limit of formula (11) to 50.0, 45.0, 40.0, or 35.0.

[0053] Furthermore, it is preferable to set the lower limit of equation (12) to -0.005, -0.002, 0.000, 0.002, or 0.003. It is also preferable to set the upper limit of equation (12) to 0.040, 0.030, 0.027, 0.020, 0.015, or 0.010.

[0054] The conditions in equations (13) and (14) indicate an appropriate range for the Abbe number and partial dispersion ratio of the negative lens positioned second from the image side in the rear lens group GR. If νd_Rn2 falls below the lower limit of equation (13), it is undesirable because it becomes difficult to correct chromatic aberration and field curvature. If νd_Rn2 exceeds the upper limit of equation (13), it is undesirable because chromatic aberration and field curvature are overcorrected. If the value in equation (14) falls below the lower limit, it is undesirable because the chromatic aberration of the g line is overcorrected. If the value in equation (14) exceeds the upper limit, it is undesirable because the chromatic aberration of the g line is undercorrected.

[0055] Furthermore, it is more preferable to set the lower limit of formula (13) to 17.0, 20.0, 25.0, 27.0, or 30.0. It is even more preferable to set the upper limit of formula (13) to 50.0, 45.0, 40.0, or 35.0.

[0056] Furthermore, it is more preferable to set the lower limit of equation (14) to -0.005, -0.002, 0.000, 0.002, or 0.003. It is also more preferable to set the upper limit of equation (14) to 0.040, 0.030, 0.027, 0.020, 0.015, or 0.010.

[0057] The conditions in equation (15) indicate an appropriate range for the lateral magnification of the intermediate lens group GM when in focus at infinity. If βM falls below the lower limit of equation (15), the power of the intermediate lens group GM relative to the front lens group GF becomes too weak, which increases spherical aberration and coma aberration, and is therefore undesirable. If βM exceeds the upper limit of equation (15), the power of the intermediate lens group GM relative to the front lens group GF becomes too weak, which increases the amount of movement of the intermediate lens group GM during focusing, and the optical system becomes larger, which is also undesirable.

[0058] Furthermore, it is more preferable to set the lower limit of formula (15) to 0.30, 0.40, 0.45, or 0.50. Also, it is more preferable to set the upper limit of formula (15) to 0.90, 0.80, 0.75, 0.70, or 0.65.

[0059] The conditions in equation (16) indicate an appropriate range for the lateral magnification of the rear lens group GR when the lens is focused at infinity. When βR falls below the lower limit of equation (16), the power of the rear lens group GR becomes too weak, which increases field curvature and chromatic aberration, and is therefore undesirable. When βR exceeds the upper limit of equation (16), the power of the rear lens group GR becomes too strong, which increases the variation in spherical aberration and field curvature with respect to changes in subject distance, and is therefore undesirable. It is also undesirable because it increases the angle of incidence of light rays to the image plane IMG.

[0060] Furthermore, it is more preferable to set the lower limit of formula (16) to 0.60, 0.70, 0.80, or 0.85. Also, it is more preferable to set the upper limit of formula (16) to 1.80, 1.50, 1.45, 1.40, 1.35, or 1.30.

[0061] The conditions in equation (17) indicate an appropriate relationship between the lateral magnification of the intermediate lens group GM and the rear lens group GR when in focus at infinity. If the value of equation (17) falls below the lower limit, the amount of movement of the intermediate lens group GM during focusing becomes large, making it difficult to shorten the overall length of the optical system, which is undesirable. If the value of equation (17) exceeds the upper limit, the fluctuations in spherical aberration and field curvature with respect to changes in subject distance become large, which is also undesirable.

[0062] Furthermore, it is more preferable to set the lower limit of formula (17) to 0.35, 0.40, 0.45, 0.50, or 0.55. Also, it is more preferable to set the upper limit of formula (17) to 1.80, 1.70, 1.60, 1.50, 1.40, or 1.30.

[0063] The conditions in equation (18) indicate an appropriate relationship between the distance from the aperture diaphragm SP to the image plane and the focal length of the entire optical system. If dsp_R / f falls below the lower limit of equation (18), the aperture diaphragm SP is too close to the image plane, making it difficult to correct image field curvature, which is undesirable. If dsp_R / f exceeds the upper limit of equation (18), it is not possible to properly arrange the lenses in the front lens group GF, making it difficult to correct spherical aberration and coma aberration, which is also undesirable.

[0064] Furthermore, it is more preferable to set the lower limit of formula (18) to 0.55, 0.60, 0.65, or 0.70. Also, it is more preferable to set the upper limit of formula (18) to 1.50, 1.30, 1.10, 1.00, or 0.85.

[0065] The conditions in equation (19) indicate an appropriate relationship between the focal length of the negative lens with the strongest refractive power in the front lens group GF and the focal length of the entire optical system. If fF_n1 / f falls below the lower limit of equation (19), the refractive power of the negative lens becomes too weak, making it difficult to correct field curvature, astigmatism, and axial chromatic aberration, which is undesirable. If fF_n1 / f exceeds the upper limit of equation (19), the curvature of the negative lens becomes too strong, making it difficult to suppress spherical aberration and coma aberration, which is also undesirable.

[0066] Furthermore, it is more preferable to set the lower limit of equation (19) to -0.75, -0.70, -0.65, -0.60, or -0.55. Also, it is more preferable to set the upper limit of equation (19) to -0.25, -0.30, -0.35, or -0.40.

[0067] The conditions in equation (20) indicate an appropriate relationship between the combined focal length of the front lens group GF and the intermediate lens group GM at infinity focus and the focal length of the entire optical system. If fFM / f falls below the lower limit of equation (20), the power of the front lens group GF and the intermediate lens group GM becomes too strong, which increases spherical aberration and lateral chromatic aberration, and is therefore undesirable. If fFM / f exceeds the upper limit of equation (20), the power of the front lens group GF and the intermediate lens group GM becomes too weak, which increases field curvature and axial chromatic aberration, and is therefore undesirable.

[0068] Furthermore, it is more preferable to set the lower limit of formula (20) to 0.50, 0.60, 0.70, or 0.80. It is even more preferable to set the upper limit of formula (20) to 1.40, 1.30, 1.20, or 1.15.

[0069] The conditions in equation (21) indicate an appropriate relationship between the combined focal length of the intermediate lens group GM and the rear lens group GR at infinity focus and the focal length of the entire optical system. When fMR / f falls below the lower limit of equation (21), the power of the intermediate lens group GM becomes too strong, increasing field curvature and coma aberration, which is undesirable. When fMR / f exceeds the upper limit of equation (21), the power of the rear lens group GR becomes too strong, increasing field curvature and chromatic aberration, which is also undesirable.

[0070] Furthermore, it is more preferable to set the lower limit of formula (21) to 0.50, 0.60, 0.70, or 0.80. Also, it is more preferable to set the upper limit of formula (21) to 1.40, 1.30, 1.20, or 1.15.

[0071] The conditions in equation (22) indicate an appropriate relationship between the focal length of the negative lens (final lens) located closest to the image in the rear lens group GR and the focal length of the entire optical system. If fRn1 / f falls below the lower limit of equation (22), the power of the final lens becomes too weak, which is undesirable because it worsens the Petzval sum and results in insufficient correction of chromatic aberration. If fRn1 / f exceeds the upper limit of equation (22), the power of the final lens becomes too strong, which increases coma aberration and distortion, which is also undesirable.

[0072] Furthermore, it is more preferable to set the lower limit of equation (22) to -4.00, -3.00, -2.50, -2.00, or -1.70. Also, it is more preferable to set the upper limit of equation (22) to -0.35, -0.40, -0.50, -0.60, -0.70, or -0.80.

[0073] The conditions in equation (23) indicate an appropriate relationship between the focal length of the positive lens positioned closest to the object in the front lens group GF and the focal length of the entire optical system. If fFp1 / f falls below the lower limit of equation (23), the power of the positive lens closest to the object becomes too strong, making it undesirable as it prevents sufficient correction of spherical aberration and axial chromatic aberration. If fFp1 / f exceeds the upper limit of equation (23), the power of the positive lens closest to the object becomes too weak, making it difficult to correct axial chromatic aberration and g-line chromatic aberration, which is also undesirable.

[0074] Furthermore, it is more preferable to set the lower limit of formula (23) to 1.40, 1.50, 1.60, 1.80, 2.20, or 2.50. Also, it is more preferable to set the upper limit of formula (23) to 8.00, 7.00, 6.00, 5.00, or 4.50.

[0075] The conditions in equation (24) indicate an appropriate relationship between the focal length of the second positive lens positioned from the object side in the front lens group GF and the focal length of the entire optical system. If fFp2 / f falls below the lower limit of equation (24), the power of the second positive lens from the object side becomes too strong, making it undesirable as spherical aberration and axial chromatic aberration cannot be adequately corrected. If fFp2 / f exceeds the upper limit of equation (24), the power of the second positive lens from the object side becomes too weak, making it difficult to correct axial chromatic aberration and g-line chromatic aberration, which is also undesirable.

[0076] Furthermore, it is more preferable to set the lower limit of formula (24) to 0.40, 0.50, 0.60, 0.70, 0.80, or 0.85. Also, it is more preferable to set the upper limit of formula (24) to 1.90, 1.80, 1.70, 1.60, 1.50, or 1.40.

[0077] The conditions in equation (25) indicate an appropriate relationship between the distance from the front element of the optical system to the image plane (IMG) and the focal length of the entire optical system. If TTL / f falls below the lower limit of equation (25), it is undesirable because the overall length of the optical system is too short, leading to increased spherical aberration, field curvature, and distortion. If TTL / f exceeds the upper limit of equation (25), it is undesirable because the optical system becomes too large.

[0078] Furthermore, it is more preferable to set the lower limit of formula (25) to 0.90, 0.95, 1.00, or 1.05. Also, it is more preferable to set the upper limit of formula (25) to 1.80, 1.70, 1.60, 1.50, 1.40, or 1.30.

[0079] The following shows the numerical examples 1 to 18 corresponding to each of the Examples 1 to 18. In the surface data of each numerical example, the surface number m indicates the order of the optical surfaces when counted from the object. r (mm) is the radius of curvature of the m-th optical surface, and d (mm) is the distance on the optical axis between the m-th surface and the (m+1)-th surface. Also, nd indicates the refractive index of each optical material at the d-line between the m-th surface and the (m+1)-th surface. Furthermore, νd and θgF indicate the Abbe number and the partial dispersion ratio at the g-line and F-line of the optical material, respectively, with respect to the d-line. The Abbe number νd with respect to the d-line and the partial dispersion ratio θgF at the g-line and F-line are given by the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm), respectively, when nd, nF, nC, and ng are used. νd=(nd-1) / (nF-nC) θgF = (ng - nF) / (nF - nC) It is represented as follows.

[0080] In each numerical example, d, focal length (mm), F-number (maximum aperture), and half-angle of view (°) are all values ​​when the optical system is in focus at infinity. Back focus Bf is, as mentioned above, the air-equivalent distance from the last surface of the optical system to the image plane. The total lens length is the distance along the optical axis from the frontmost element of the optical system to the last lens surface plus the back focus, and corresponds to TTL in equation (25).

[0081] The asterisk (*) next to the surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following formula, where X is the displacement from the surface vertex in the direction of the optical axis, h is the height from the optical axis in the direction perpendicular to the optical axis, the direction of light propagation is positive, R is the radius of paraxial curvature, K is the cone constant, and A4, A6, A8, A10, and A12 are the aspherical coefficients of their respective orders.

[0082] X=( h 2 / R) / [1+{1-(1+K)(h / R) 2} 1 / 2 ] +A4×h 4 +A6×h 6 +A8×h 8+A10×h 10 +A12×h 12 Note that "e±XX" in the cone constant and aspheric coefficients is "×10 ±XX It means "...".

[0083] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd θgF 1 96.499 5.01 1.65160 58.5 2 244.233 0.20 3 40.463 9.97 1.59282 68.6 4 137.242 0.52 5 33.358 6.83 1.59282 68.6 6 61.128 4.66 7 83.373 1.30 1.77047 29.7 0.5951 8 22.227 9.67 9 (aperture) ∞ (variable) 10 -30.468 1.00 1.60342 38.0 11 105.554 0.20 12 67.398 6.03 1.77250 49.6 13 -94.056 3.94 14* 118.421 5.52 1.80400 46.5 15* -59.424 (variable) 16 2325.253 5.58 1.95375 32.3 17 -47.406 1.20 1.59270 35.3 0.5933 18 219.960 5.34 19 -43.433 1.30 1.59270 35.3 0.5933 20 -137.495 13.72 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-2.09392e-06 A 6=-6.92589e-10 A 8=-1.63601e-11 A10=4.15588e-14 A12=-6.98948e-17 Page 15 K = 0.00000e+00 A 4= 9.61259e-07 A 6=-4.05931e-09 A 8=-4.40009e-13 A10=6.31396e-15 A12=-3.81358e-17 Focal length 82.50 F-number 1.45 Half-angle (°): 14.69 Image height 21.63 Lens length: 102.54 Bf 13.72 Group spacing Infinity Close range d 9 18.06 6.09 d15 2.48 14.46 group focal length Group starting plane focal length 1 1 127.21 2 10 59.61 3 16 -275.31 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd θgF 1 95.111 4.93 1.65160 58.5 2 229.353 0.25 3 39.890 10.14 1.59282 68.6 4 137.462 0.30 5 33.098 8.11 1.59282 68.6 6 61.220 3.90 7 84.095 1.30 1.77047 29.7 0.5951 8 21.568 9.58 9 (aperture) ∞ (variable) 10 -29.553 1.00 1.62205 41.1 11 128.682 0.20 12 69.063 6.70 1.77250 49.6 13 -63.820 4.72 14* 103.130 6.38 1.80400 46.5 15* -74.820 (variable) 16 -338.670 6.05 1.95375 32.3 17 -39.196 1.20 1.63980 34.5 0.5922 18 538.427 5.42 19 -39.662 1.30 1.59270 35.3 0.5933 20 -103.580 11.99 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-2.40891e-06 A 6=-1.51484e-09 A 8=-1.39162e-11 A10=3.05767e-14 A12=-6.30065e-17 Page 15 K = 0.00000e+00 A 4= 3.05960e-07 A 6=-5.60761e-09 A 8= 7.22428e-12 A10=-1.75538e-14 A12=-1.23933e-17 Focal length 82.46 F-number 1.45 Half-angle (°): 14.70 Image height 21.63 Lens length: 102.56 Bf 11.99 Group spacing Infinity Close range d 9 17.10 6.05 d15 2.00 13.05 group focal length Group starting plane focal length 1 1 125.31 2 10 54.92 3 16 -202.25 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd θgF 1 94.508 4.38 1.89190 37.1 2 175.745 0.20 3 41.300 9.65 1.61800 63.4 4 141.876 3.33 5 33.034 9.04 1.59282 68.6 6 56.648 1.50 7 80.687 1.64 1.85451 25.2 0.6103 8 22.626 9.21 9 (aperture) ∞ (variable) 10 -29.615 1.00 1.62205 41.1 11 164.154 0.20 12 66.252 6.64 1.75500 52.3 13 -68.156 5.15 14* 109.455 5.07 1.80400 46.5 15* -73.690 (variable) 16 -11631.908 5.04 2.00100 29.1 17 -52.308 1.20 1.59270 35.3 0.5933 18 158.970 6.07 19 -40.462 1.90 1.59270 35.3 0.5933 20 -97.841 12.00 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-2.53679e-06 A 6= 3.16815e-09 A 8=-2.96570e-11 A10= 4.26246e-14 A12= 9.62952e-18 Page 15 K = 0.00000e+00 A 4= 4.48655e-07 A 6=-8.37526e-10 A 8=-4.58865e-12 A10=-2.65147e-14 A12= 8.53907e-17 Focal length 82.51 F-number 1.45 Half-angle (°): 14.69 Image height 21.63 Lens length: 102.51 Bf 12.00 Group spacing Infinity Close range d 9 17.26 5.99 d15 2.06 13.32 group focal length Group starting plane focal length 1 1 130.46 2 10 55.50 3 16 -235.53 [Numerical Example 4] Unit: mm Surface data Face number rd nd νd θgF 1 89.672 5.37 1.61997 63.9 2 239.563 0.20 3 39.734 10.32 1.59522 67.7 4 146.027 0.30 5 34.372 9.22 1.59522 67.7 6 54.231 3.23 7 86.877 1.30 1.77047 29.7 0.5951 8 21.845 9.34 9 (aperture) ∞ (variable) 10 -28.721 1.00 1.65253 39.5 11 261.154 0.21 12 67.641 7.06 1.75500 52.3 13 -55.967 5.56 14* 103.414 4.47 1.85135 40.1 15* -97.680 (variable) 16 -644.435 6.05 1.95375 32.3 17 -40.993 1.20 1.67270 32.1 0.5922 18 398.025 5.48 19 -39.868 1.30 1.59270 35.3 0.5933 20 -100.321 12.01 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-1.98634e-06 A 6= 2.77142e-09 A 8=-3.34232e-11 A10=7.60383e-14 A12=-4.73445e-18 Page 15 K = 0.00000e+00 A 4= 6.90520e-07 A 6= 3.36538e-10 A 8=-1.90446e-11 A10= 3.73899e-14 A12= 4.64347e-17 Focal length 82.49 F-number 1.45 Half-angle (°): 14.69 Image height 21.63 Lens length: 102.52 Bf 12.01 Group spacing Infinity Close range d 9 16.90 6.07 d15 2.00 12.82 group focal length Group starting plane focal length 1 1 129.63 2 10 53.83 3 16 -199.45 [Numerical Example 5] Unit: mm Surface data Face number rd nd νd θgF 1 105.002 4.27 1.80400 46.5 2 207.534 0.20 3 44.029 9.44 1.59522 67.7 4 173.281 1.34 5 34.216 6.46 1.59522 67.7 6 61.627 2.29 7 87.425 1.64 1.73037 32.2 0.5899 8 24.244 3.46 9 38.204 2.53 1.51742 52.4 10 31.305 8.00 11 (aperture) ∞ (variable) 12 -29.930 2.00 1.60342 38.0 13 100.120 0.47 14 99.185 6.64 1.80400 46.5 15 -51.137 6.17 16 107.238 8.00 1.88300 40.8 17 -119.671 (variable) 18 -2153.232 12.11 1.85150 40.8 19 -40.014 2.00 1.77830 23.9 0.6248 20 -116.338 9.01 21 -46.101 1.30 1.78800 47.4 0.5559 22 -158.459 12.00 Image plane ∞ Focal length 82.50 F-number 1.45 Half-angle (°): 14.69 Image height 21.63 Lens length: 120.00 Bf 12.00 Group spacing Infinity Close range d11 18.66 6.66 d17 2.00 14.00 group focal length Group starting plane focal length 1 1 163.14 2 12 60.82 3 18 -324.63 [Numerical Example 6] Unit: mm Surface data Face number rd nd νd θgF 1 92.342 5.07 1.65160 58.5 2 223.152 0.78 3 39.789 10.14 1.59282 68.6 4 138.752 1.11 5 33.141 8.05 1.59282 68.6 6 58.115 3.47 7 84.465 1.30 1.77047 29.7 0.5951 8 21.789 10.19 9 (aperture) ∞ (variable) 10 -29.147 1.00 1.62205 41.1 11 179.454 0.20 12 66.718 6.84 1.75500 52.3 13 -61.745 5.35 14* 103.675 4.91 1.80400 46.5 15* -82.562 (variable) 16 -669.089 5.87 2.00100 29.1 17 -41.978 1.20 1.68893 31.1 0.6004 18 342.517 5.45 19 -40.276 1.30 1.59270 35.3 0.5933 20 -116.537 11.98 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-2.18628e-06 A 6= 1.10219e-09 A 8=-1.53783e-11 A10= 2.85568e-14 A12= 4.39078e-18 Page 15 K = 0.00000e+00 A 4= 3.13286e-07 A 6= 1.10649e-09 A 8=-1.44957e-11 A10= 2.85592e-14 A12= 1.05169e-17 Focal length 82.49 F-number 1.45 Half-angle (°): 14.70 Image height 21.63 Lens length: 102.52 Bf 11.98 Group spacing Infinity Close range d 9 16.31 5.98 d15 2.00 12.33 group focal length Group starting plane focal length 1 1 126.76 2 10 54.70 3 16 -184.46 [Numerical Example 7] Unit: mm Surface data Face number rd nd νd θgF 1 104.449 3.95 1.89190 37.1 2 183.359 0.20 3 39.124 10.61 1.59282 68.6 4 138.504 1.09 5 34.718 6.70 1.59282 68.6 6 54.935 4.33 7 80.111 1.30 1.85478 24.8 0.6122 8 24.895 10.14 9 (aperture) ∞ (variable) 10 -32.930 1.00 1.61340 44.3 11 110.533 0.20 12 43.544 6.18 1.83481 42.7 13 -329.640 6.78 14* 72.419 4.51 1.85135 40.1 15* -78.936 (variable) 16 -60.771 6.90 1.95375 32.3 17 -26.032 1.20 1.66382 27.4 0.6319 18 -208.185 7.38 19 -34.802 1.30 1.51742 52.4 0.5564 20 -71.968 11.98 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-4.45748e-06 A 6=-4.41383e-09 A 8= 2.11503e-11 A10=-5.14789e-13 A12= 1.04737e-15 Page 15 K = 0.00000e+00 A 4= 1.92133e-06 A 6=-1.35111e-08 A 8= 1.20277e-10 A10=-8.62972e-13 A12= 1.51699e-15 Focal length 82.46 F-number 1.45 Half-angle (°): 14.70 Image height 21.63 Lens length: 102.56 Bf 11.98 Group spacing Infinity Close range d 9 14.01 6.00 d15 2.80 10.80 group focal length Group starting plane focal length 1 1 133.56 2 10 47.19 3 16 -115.99 [Numerical Example 8] Unit: mm Surface data Face number rd nd νd θgF 1 87.194 4.66 1.72916 54.7 2 165.767 0.20 3 40.198 10.28 1.59282 68.6 4 146.250 0.30 5 33.923 7.47 1.59522 67.7 6 57.542 3.86 7 85.721 1.32 1.77047 29.7 0.5951 8 22.453 9.73 9 (aperture) ∞ (variable) 10 -30.566 1.00 1.62205 41.1 11 146.161 0.47 12 59.114 4.89 1.75500 52.3 13 -60.109 8.37 14* 92.380 3.89 1.88202 37.2 15* -151.372 (variable) 16 -268.681 6.37 1.95375 32.3 17 -35.270 1.20 1.66382 27.4 0.6319 18 733.130 5.56 19 -36.645 1.30 1.51742 52.4 0.5564 20 -92.123 12.00 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-8.32103e-07 A 6= 2.73491e-09 A 8=-3.60681e-11 A10= 7.67918e-14 A12= 3.48364e-18 Page 15 K = 0.00000e+00 A 4= 1.89294e-06 A 6= 2.76613e-09 A 8=-3.09673e-11 A10= 5.95910e-14 A12= 4.05639e-17 Focal length 82.50 F-number 1.45 Half-angle (°): 14.69 Image height 21.63 Lens length: 102.50 Bf 12.00 Group spacing Infinity Close range d 9 16.99 6.19 d15 2.65 13.45 group focal length Group starting plane focal length 1 1 133.90 2 10 56.91 3 16 -222.78 [Numerical Example 9] Unit: mm Surface data Face number rd nd νd θgF 1 95.214 4.73 1.65160 58.5 2 261.619 0.73 3 40.303 9.76 1.59282 68.6 4 128.719 0.38 5 33.386 6.80 1.59282 68.6 6 61.069 4.71 7 80.040 1.30 1.77047 29.7 0.5951 8 21.970 9.67 9 (aperture) ∞ (variable) 10 -31.325 1.00 1.65253 39.5 11 130.971 0.20 12* 93.270 4.24 1.76802 49.2 13* -63.617 5.23 14 154.194 6.11 1.83481 42.7 15 -57.367 (variable) 16 1349.945 6.08 2.00100 29.1 17 -44.595 1.20 1.66382 27.4 0.6319 18 199.274 5.80 19 -40.687 1.30 1.59270 35.3 0.5564 20 -112.414 13.24 Image plane ∞ Aspherical data Side 12 K = 0.00000e+00 A 4=-3.58829e-06 A 6= 3.54473e-08 A 8=-3.44570e-10 A10= 1.45153e-12 A12=-2.39626e-15 Page 13 K = 0.00000e+00 A 4=-8.86858e-08 A 6= 1.18777e-08 A 8=-8.65294e-11 A10= 1.89406e-13 A12=-2.26832e-16 Focal length 82.78 F-number 1.45 Half-angle (°): 14.65 Image height 21.63 Lens length: 102.50 Bf 13.24 Group spacing Infinity Close range d 9 18.03 6.01 d15 2.01 14.03 group focal length Group starting plane focal length 1 1 126.52 2 10 59.21 3 16 -254.49 [Numerical Example 10] Unit: mm Surface data Face number rd nd νd θgF 1 79.821 4.45 1.75500 52.3 2 152.402 0.20 3 40.358 9.71 1.59282 68.6 4 127.922 0.30 5 32.616 8.00 1.59282 68.6 6 58.920 2.68 7 75.185 1.30 1.77047 29.7 0.5951 8 21.455 10.20 9 (aperture) ∞ (variable) 10* -46.062 1.10 1.68948 31.0 11* 62.280 0.20 12 78.288 2.51 2.05090 26.9 13 -425.859 4.87 14 106.112 6.56 1.77250 49.6 15 -45.410 (variable) 16 -241.087 7.23 1.89190 37.1 17 -31.536 1.20 1.59270 35.3 0.5933 18 302.600 7.18 19 -28.831 1.45 1.76182 26.5 0.6136 20 -40.290 11.99 Image plane ∞ Aspherical data 10th surface K = 0.00000e+00 A 4=-3.38510e-05 A 6= 3.45660e-07 A 8=-2.62582e-09 A10= 1.07715e-11 A12=-1.86201e-14 11th surface K = 0.00000e+00 A 4=-2.70148e-05 A 6= 3.38895e-07 A 8=-2.54184e-09 A10= 1.06250e-11 A12=-1.88213e-14 Focal length 82.50 F-number 1.45 Half angle of view (°) 14.69 Image height 21.63 Overall lens length 102.50 Bf 11.99 Distance between groups Infinity to nearest[[ID=�0]] d 9 17.24 5.59 d15 4.14 15.79 Group focal length Group starting surface focal length 1 1 127.62 2 10 61.12 3 16 -323.86 [Numerical Example 11] Unit: mm Surface data Face number rd nd νd θgF 1 99.177 5.41 1.61800 63.4 2 334.356 0.20 3 39.105 10.27 1.59282 68.6 4 130.871 0.20 5 33.744 6.31 1.59282 68.6 6 57.901 5.38 7 83.935 1.30 1.77047 29.7 0.5951 8 21.878 9.50 9 (aperture) ∞ (variable) 10 -28.359 1.00 1.62205 41.1 11 129.885 0.20 12 77.279 6.11 1.75500 52.3 13 -55.748 (variable) 14* 84.191 6.49 1.69350 53.2 15* -66.324 (variable) 16 519.279 5.23 2.00100 29.1 17 -58.000 1.20 1.59270 35.3 0.5933 18 127.717 6.07 19 -44.359 1.30 1.59270 35.3 0.5933 20 -167.476 11.98 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-2.63884e-06 A 6= 1.79025e-08 A 8=-1.17237e-10 A10 = 3.28822e-13 A12 = -4.00329e-16 The 15th surface K = 0.00000e+00 A4 = -2.04702e-07 A6 = 1.74076e-08 A8 = -1.14654e-10 A10 = 3.24434e-13 A12 = -3.92510e-16 Focal length 82.67 F number 1.45 Half angle of view (°) 14.66 Image height 21.63 Overall lens length 102.52 Bf 11.98 Distance between groups Infinity - Close d9 17.31 6.52 d13 5.06 5.03 d15 2.00 12.83 Group focal length Group starting surface focal length 1 1 128.88 2 10 -445.98 3 14 54.46 4 16 -196.94 [Numerical example 12] Unit: mm Surface data Surface number r d nd νd θgF 1 98.848 5.24 1.67000 57.3 2 295.504 0.20 3 38.967 10.16 1.59282 68.6 4 127.582 0.20 5 33.955 6.18 1.59282 68.6 6 57.395 5.46 7 82.388 1.30 1.77047 29.7 0.5951 8 21.744 9.79 9 (Aperture) ∞ (Variable) 10 -27.898 1.00 1.59270 35.3 11 114.559 0.20 12 74.170 7.05 1.78800 47.4 13 -55.320 (variable) 14* 82.406 6.46 1.58313 59.4 15* -63.395 (variable) 16 335.703 4.72 2.00100 29.1 17 -69.752 1.20 1.51742 52.4 0.5564 18 111.575 6.26 19 -44.430 1.30 1.59270 35.3 0.5933 20 -169.512 11.94 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-1.28965e-06 A 6= 1.09747e-10 A 8=-1.92881e-11 A10=5.68304e-14 A12=-9.01657e-17 Page 15 K = 0.00000e+00 A 4= 1.59789e-06 A 6=-3.01213e-09 A 8=-5.28990e-12 A10=2.85732e-14 A12=-6.36765e-17 Focal length 82.45 F-number 1.45 Half-angle (°): 14.70 Image height 21.63 Lens length: 102.52 Bf 11.94 Group spacing Infinity Close range d 9 17.26 6.31 d13 4.59 4.21 d15 2.00 13.34 group focal length Group starting plane focal length 1 1 131.50 2 10 -3633.33 3 14 62.47 4 16 -246.75 [Numerical Example 13] Unit: mm Surface data Face number rd nd νd θgF 1 96.945 5.14 1.64000 60.1 2 265.298 0.20 3 39.611 10.34 1.59522 67.7 4 140.530 0.56 5 34.105 6.50 1.59522 67.7 6 58.670 4.50 7 89.820 1.55 1.77047 29.7 0.5951 8 22.607 10.97 9 (aperture) ∞ (variable) 10 -29.095 1.00 1.62205 41.1 11 210.645 0.20 12 72.320 6.09 1.75500 52.3 13 -57.044 (variable) 14* 96.118 4.91 1.76802 49.2 15* -87.910 (variable) 16 -1397.939 5.24 2.05090 26.9 17 -49.271 1.20 1.62200 30.7 0.6248 18 191.538 5.60 19 -42.608 1.62 1.62200 30.7 0.6248 20 -152.005 12.00 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-2.06220e-06 A 6= 1.22665e-08 A 8=-6.98957e-11 A10= 1.55075e-13 A12=-1.01447e-16 Page 15 K = 0.00000e+00 A 4= 6.71633e-07 A 6= 9.76857e-09 A 8=-5.39670e-11 A10= 1.11935e-13 A12=-5.18311e-17 Focal length 82.50 F-number 1.45 Half-angle (°): 14.69 Image height 21.63 Lens length: 102.53 Bf 12.00 Group spacing Infinity Close range d 9 16.85 6.12 d13 6.08 6.38 d15 2.00 12.42 group focal length Group starting plane focal length 1 1 129.43 2 10 2766.85 3 14 60.49 4 16 -184.77 [Numerical Example 14] Unit: mm Surface data Face number rd nd νd θgF 1 103.915 4.11 1.75520 27.5 2 180.873 0.20 3 44.831 10.12 1.59282 68.6 4 179.064 0.20 5 38.169 9.44 1.59282 68.6 6 66.930 1.93 7 97.016 1.30 1.77047 29.7 0.5951 8 25.406 10.23 9 (aperture) ∞ (variable) 10* -45.745 1.50 1.68948 31.0 11* 116.064 0.20 12 86.774 9.12 1.88300 40.8 13 -151.651 2.00 14 153.458 10.53 1.72916 54.7 15 -51.051 (variable) 16 -100.778 1.30 1.62004 36.3 17 44.683 9.27 1.88300 40.8 18 -107.944 0.20 19 4694.716 6.52 2.05090 26.9 20 -59.604 1.20 1.59270 35.3 0.5933 21 109.627 7.11 22 -39.257 1.30 1.85896 22.7 0.6284 23 -92.586 11.99 Image plane ∞ Aspherical data Side 10 K = 0.00000e+00 A 4=-7.66494e-06 A 6= 1.88617e-08 A 8=-3.48146e-11 A10=-9.14108e-14 A12= 2.58628e-16 Page 11 K = 0.00000e+00 A 4=-3.03405e-06 A 6= 1.75168e-08 A 8= 8.40543e-12 A10=-2.34189e-13 A12= 4.50355e-16 Focal length 73.70 F-number 1.24 Half-angle (°): 16.36 Image height 21.63 Lens length: 120.05 Bf 11.99 Group spacing Infinity Close range d 9 16.75 6.46 d15 3.52 13.81 group focal length Group starting plane focal length 1 1 169.50 2 10 62.63 3 16 -1494.49 [Numerical Example 15] Unit: mm Surface data Face number rd nd νd θgF 1 95.104 4.38 1.61997 63.9 2 183.220 0.20 3 47.738 8.65 1.59282 68.6 4 216.503 11.00 5 33.803 7.15 1.49700 81.5 6 67.524 1.81 7 138.349 1.30 1.73037 32.2 0.5899 8 26.585 7.85 9 (aperture) ∞ (variable) 10 45.541 2.87 1.65160 58.5 11 892.884 1.13 12 -76.515 1.50 1.61340 44.3 13 56.431 (Variable) 14 112.667 7.52 1.77250 49.6 15 -78.995 (variable) 16 -53.286 1.30 1.68430 26.8 17 65.737 7.90 1.96300 24.1 0.6212 18 -57.151 9.01 19 -48.169 1.30 1.92286 20.9 0.6390 20 -180.151 12.10 Image plane ∞ Focal length 103.00 F-number 1.84 Half-angle (°): 11.86 Image height 21.63 Lens length: 120.00 Bf 12.10 Group spacing Infinity Close range d 9 18.89 2.00 d13 11.21 10.24 d15 2.93 20.79 group focal length Group starting plane focal length 1 1 157.90 2 10 -223.66 3 14 61.16 4 16 -224.89 [Numerical Example 16] Unit: mm Surface data Face number rd nd νd θgF 1 83.479 4.33 1.78800 47.4 2 138.302 0.20 3 41.305 9.96 1.59522 67.7 4 149.548 0.30 5 32.467 7.36 1.59522 67.7 6 61.890 3.59 7 80.195 1.30 1.77047 29.7 0.5951 8 22.075 10.16 9 (aperture) ∞ (variable) 10 -31.903 0.99 1.62205 41.1 11 -1360.845 0.20 12 91.225 3.73 1.81600 46.6 13 -55.025 (variable) 14 -89.092 1.00 1.69895 30.1 15 264.516 (variable) 16* 59.993 7.19 1.85135 40.1 17* -73.806 (variable) 18 -227.718 4.86 2.00100 29.1 19 -46.931 1.20 1.62004 36.3 0.5879 20 127.812 4.68 21 -63.713 1.30 1.68430 26.8 0.6232 22 -290.269 11.91 Image plane ∞ Aspherical data Page 16 K = 0.00000e+00 A 4=-1.96723e-06 A 6=-1.38972e-09 A 8= 3.06406e-11 A10=-1.02754e-13 A12= 1.36669e-16 Page 17 K = 0.00000e+00 A 4= 2.30491e-06 A 6=-5.17664e-09 A 8= 4.85886e-11 A10=-1.52250e-13 A12= 1.91585e-16 Focal length 82.63 F-number 1.45 Half-angle (°): 14.67 Image height 21.63 Lens length: 102.54 Bf 11.91 Group spacing Infinity Close range d 9 16.09 6.04 d13 1.96 12.02 d15 8.22 2.70 d17 2.00 7.52 group focal length Group starting plane focal length 1 1 125.03 2 10 184.69 3 14 -95.24 4 16 39.86 5 18 -104.71 [Numerical Example 17] Unit: mm Surface data Face number rd nd νd θgF 1 100.562 5.12 1.61997 63.9 2 264.369 0.70 3 37.258 12.30 1.59522 67.7 4 141.561 0.30 5 33.061 7.76 1.59522 67.7 6 58.146 3.05 7 101.752 1.50 1.77047 29.7 0.5951 8 22.004 10.29 9 (aperture) ∞ (variable) 10 -26.032 1.50 1.62205 41.1 11 -385.074 0.20 12 70.797 10.00 1.77250 49.6 13 -61.085 6.11 14* 75.868 5.88 1.85135 40.1 15* -76.706 (variable) 16 -98.035 0.90 1.59270 35.3 17 84.043 2.07 2.05090 26.9 0.6052 18 141.445 3.12 19 -112.994 1.30 1.62200 30.7 0.6248 20 971.714 12.14 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-1.56716e-06 A 6= 1.01211e-09 A 8=-1.61996e-13 A10=-1.38231e-14 A12= 7.55122e-17 Page 15 K = 0.00000e+00 A 4= 2.33785e-06 A 6=-2.25082e-09 A 8= 1.12007e-11 A10=-3.22747e-14 A12= 9.39004e-17 Focal length 85.02 F-number 1.45 Half-angle (°): 14.28 Image height 21.63 Lens length: 102.51 Bf 12.14 Group spacing Infinity Close range d 9 16.26 8.86 d15 2.00 9.40 group focal length Group starting plane focal length 1 1 120.23 2 10 38.26 3 16 -69.61 [Numerical Example 18] Unit: mm Surface data Face number rd nd νd θgF 1 75.008 3.81 2.00069 25.5 2 106.260 0.21 3 41.941 9.60 1.59282 68.6 4 188.605 0.30 5 42.246 4.14 1.59282 68.6 6 58.239 3.04 7 120.927 1.31 1.77047 29.7 0.5951 8 28.784 9.96 9 (aperture) ∞ (variable) 10 -34.015 1.71 1.63980 34.5 11 90.226 0.20 12 50.942 12.35 1.75500 52.3 13 -441.100 2.85 14* 112.302 6.07 1.76802 49.2 15* -54.043 (variable) 16 169.406 7.55 2.00100 29.1 17 -47.231 7.18 1.75211 25.0 0.6192 18 781.714 2.37 19 -67.421 1.30 1.59270 35.3 0.5933 20 153.928 29.90 Image plane ∞ Aspherical data Page 14 K = 0.00000e+00 A 4=-2.80947e-06 A 6=-1.32433e-09 A 8=-2.15907e-11 A10= 1.04837e-13 A12=-1.80154e-16 Page 15 K = 0.00000e+00 A 4= 1.37731e-06 A 6=-1.00542e-09 A 8=-1.67238e-11 A10=8.99597e-14 A12=-1.59322e-16 Focal length 79.70 F-number 1.45 Half-angle (°): 15.19 Image height 21.63 Lens length: 125.03 Bf 29.90 Group spacing Infinity Close range d 9 19.13 7.77 d15 2.06 13.43 group focal length Group starting plane focal length 1 1 208.63 2 10 67.52 3 16 -762.63 The values ​​of equations (1) to (25) for each numerical example are summarized in Tables 1 and 2 below. The optical systems in each numerical example satisfy all the conditions of equations (1) to (25).

[0084] [Table 1]

[0085] [Table 2]

[0086] Figures 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, and 36 show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical systems of numerical examples 1 to 18 at infinity focus.

[0087] In the spherical aberration diagram, Fno indicates the F number, the solid line shows spherical aberration at the d line (wavelength 587.6 nm), and the dashed line shows spherical aberration at the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S shows astigmatism at the sagittal image plane, and the dashed line M shows astigmatism at the meridional image plane. The distortion diagram shows distortion at the d line. The chromatic aberration diagram shows lateral chromatic aberration at the g line. ω is the half-angle of view (°). [Imaging device] Figure 37 shows a digital still camera (imaging device) 200 using the optical systems of each embodiment. In Figure 37, 201 is the camera body, and 202 is a lens device that includes the optical systems of Embodiments 1 to 18 as the imaging optical system. The lens device 202 may be detachable from the camera body 201 or may be integrated into it.

[0088] 203 is an image sensor, such as a CCD sensor or CMOS sensor, built into the camera body 201, which converts the optical image formed by the imaging optical system into photoelectric data (i.e., it images the subject through the imaging optical system).

[0089] The camera body 201 may be a single-lens reflex camera with a quick-turn mirror, or a mirrorless camera without a quick-turn mirror.

[0090] By applying the optical systems of each embodiment to the imaging device in this way, it is possible to provide an imaging device that is compact yet capable of acquiring high-quality images.

[0091] The above embodiments include the following configuration.

[0092] (Composition 1) An optical system comprising a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side, During focusing, the front and rear lens groups do not move, but the intermediate lens group moves, changing the spacing between adjacent lens groups. The aforementioned front, intermediate, and rear lens groups each include multiple lenses. The aforementioned front lens group has the positive lens closest to the object, The aforementioned rear lens group has the negative lens closest to the image. The total number of lenses included in the optical system is 12 or less. When Bf is the air-equivalent distance along the optical axis from the image-side lens surface to the image plane of the optical system, fM is the focal length of the intermediate lens group when it is in focus on an object at infinity, and f is the focal length of the optical system when it is in focus on an object at infinity, 0.03 ≤ Bf / f ≤ 0.38 0.30 ≤ fM / f ≤ 0.85 An optical system characterized by satisfying the following conditions. (Configuration 2) An optical system comprising a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side, During focusing, the front and rear lens groups do not move, but the intermediate lens group moves, changing the spacing between adjacent lens groups. The aforementioned front, intermediate, and rear lens groups each include multiple lenses. The aforementioned front lens group has the positive lens closest to the object, The total number of lenses included in the optical system is 13 or less. When Bf is the air-equivalent distance along the optical axis from the image-side lens surface to the image plane of the optical system, fM is the focal length of the intermediate lens group when focused on an object at infinity, f is the focal length of the optical system when focused on an object at infinity, and F is the maximum aperture F-number of the optical system, 0.03 ≤ Bf / f ≤ 0.38 0.30 ≤ fM / f ≤ 0.85 1.00 ≤ F ≤ 1.85 An optical system characterized by satisfying the following conditions. (Composition 3) When the focal length of the aforementioned front lens group is fF, 1.00 ≤ fF / f ≤ 5.00 The optical system according to configuration 1 or 2, characterized by satisfying the following conditions. (Composition 4) When the focal length of the aforementioned rear lens group is fR, -100.00 ≤ fR / f ≤ -0.30 An optical system according to any one of configurations 1 to 3, characterized by satisfying the following conditions. (Composition 5) When the focal length of the aforementioned front lens group is fF, 1.20 ≤ fF / fM ≤ 7.00 An optical system according to any one of configurations 1 to 4, characterized by satisfying the following conditions. (Composition 6) When the focal length of the aforementioned rear lens group is fR, -100.00 ≤ fR / fM ≤ -0.80 An optical system according to any one of configurations 1 to 5, characterized by satisfying the following conditions. (Composition 7) The negative lens included in the aforementioned front lens group has a refractive index of nd_Fn on the d line, an Abbe number with respect to the d line νd_Fn, and a partial dispersion ratio of θgF_Fn on the g line and F line, ×10 -X Let EX be, 1.50≦nd_Fn≦2.35-0.015×νd_Fn 20.0 ≤ νd_Fn ≤ 60.0 -0.100≦θgF_Fn-(-9.529E-8×νd_Fn 3 +3.694E-5×νd_Fn 2 -4.717E-3×νd_Fn+7.139E-1)≦0.000 An optical system according to any one of configurations 1 to 6, characterized by satisfying the following conditions. (Composition 8) The negative lens positioned closest to the image in the aforementioned rear lens group has an Abbe number of νd_Rn1 with respect to the d line of the negative lens, and a partial dispersion ratio of θgF_Rn1 between the g line and the F line, ×10 -X Let EX be, 15.0 ≤ νd_Rn1 ≤ 55.0 -0.010≦θgF_Rn1-(-9.529E-8×νd_Rn1 3 +3.694E-5×νd_Rn1 2 -4.717E-3×νd_Rn1+7.139E-1)≦0.050 An optical system according to any one of configurations 1 to 7, characterized by satisfying the following conditions. (Composition 9) The aforementioned rear lens group has a negative lens as the second from the image side. The Abbe number of the second negative lens with respect to the d line is νd_Rn2, the partial dispersion ratio between the g line and the F line is θgF_Rn2, ×10 -X Let EX be, 15.0 ≤ νd_Rn2 ≤ 55.0 -0.010≦θgF_Rn2-(-9.529E-8*νd_Rn2 3 +3.694E-5×νd_Rn2 2 -4.717E-3×νd_Rn2+7.139E-1)≦0.050 An optical system according to any one of configurations 1 to 8, characterized by satisfying the following conditions. (Composition 10) The optical system according to any one of configurations 1 to 9, characterized in that the positive lens closest to the object in the front lens group is a meniscus lens with a convex surface facing the object. (Composition 11) The optical system according to any one of configurations 1 to 10, characterized in that the second lens from the object side in the aforementioned front lens group is a meniscus lens with a convex surface facing the object side. (Composition 12) The optical system according to any one of configurations 1 to 11, characterized in that the third lens from the object side in the aforementioned front lens group is a meniscus lens with a convex surface facing the object side. (Composition 13) The optical system according to any one of configurations 1 to 12, characterized in that the fourth lens from the object side of the aforementioned front lens group is a meniscus lens with a convex surface facing the object side. (Composition 14) The optical system according to any one of configurations 1 to 13, characterized in that the total number of lenses included in the aforementioned front lens group is 5 or less. (Composition 15) The optical system according to any one of configurations 1 to 14, characterized in that the total number of lenses included in the intermediate lens group is four or less. (Composition 16) The optical system according to any one of configurations 1 to 15, characterized in that the total number of lenses included in the rear lens group is 5 or less. (Composition 17) The optical system according to any one of configurations 1 to 16, characterized in that each of the front, intermediate, and rear lens groups includes at least one positive lens and at least one negative lens. (Composition 18) The optical system according to any one of configurations 1 to 17, characterized in that the front lens group includes at least two positive lenses with an Abbe number of 60 or more with respect to the d line. (Composition 19) The optical system according to any one of configurations 1 to 18, characterized in that the intermediate lens group includes at least one aspherical lens. (Composition 20) When the image lateral magnification of the intermediate lens group is focused on an object at infinity, let βM be the magnification of the intermediate lens group. 0.20 ≤ βM ≤ 1.00 An optical system according to any one of configurations 1 to 19, characterized by satisfying the following conditions. (Composition 21) When the image lateral magnification of the rear lens group is focused on an object at infinity, let βR be the magnification factor. 0.50 ≤ βR ≤ 2.00 An optical system according to any one of configurations 1 to 20, characterized by satisfying the following conditions. (Composition 22) When the image lateral magnification of the intermediate lens group when focused on an object at infinity is βM, and the image lateral magnification of the rear lens group when focused on an object at infinity is βR, 0.30 ≤ (1 - βM) 2 )×βR 2 ≤2.00 An optical system according to any one of configurations 1 to 21, characterized by satisfying the following conditions. (Composition 23) The optical system has an aperture diaphragm, When the distance along the optical axis from the aperture diaphragm to the image plane is denoted as dsp_R, 0.50 ≤ dsp_R / f ≤ 2.00 An optical system according to any one of configurations 1 to 22, characterized by satisfying the following conditions. (Composition 24) When the focal length of the negative lens with the strongest refractive power among the at least one negative lens included in the aforementioned front lens group is fF_n1, -0.80 ≤ fF_n1 / f ≤ -0.20 An optical system according to any one of configurations 1 to 23, characterized by satisfying the following conditions. (Composition 25) The optical system according to any one of configurations 1 to 24, characterized in that the optical system has an aperture diaphragm between the front lens group and the intermediate lens group. (Composition 26) When the combined focal length of the front lens group and the intermediate lens group is fFM when in focus on an object at infinity, 0.40 ≤ fFM / f ≤ 1.50 An optical system according to any one of configurations 1 to 25, characterized by satisfying the following conditions. (Composition 27) When the combined focal length of the intermediate lens group and the rear lens group is in focus on an object at infinity, let fMR be the combined focal length of the intermediate lens group and the rear lens group. 0.40 ≤ fMR / f ≤ 1.50 An optical system according to any one of configurations 1 to 26, characterized by satisfying the following conditions. (Composition 28) When the focal length of the negative lens positioned closest to the image side in the aforementioned rear lens group is denoted as fRn1, -5.00 ≤ fRn1 / f ≤ -0.30 An optical system according to any one of configurations 1 to 27, characterized by satisfying the following conditions. (Composition 29) When the focal length of the positive lens closest to the object in the aforementioned front lens group is fFp1, 1.20 ≤ fFp1 / f ≤ 10.00 An optical system according to any one of configurations 1 to 28, characterized by satisfying the following conditions. (Composition 30) When the focal length of the positive lens second from the object side in the aforementioned front lens group is fFp2, 0.30 ≤ fFp² / f ≤ 2.00 An optical system according to any one of configurations 1 to 29, characterized by satisfying the following conditions. (Composition 31) The optical system according to any one of configurations 1 to 30, characterized in that the refractive index of at least one positive lens included in the rear lens group is 1.850 or less on the d line and the Abbe number with respect to the d line is 50.0 or less. (Composition 32) The aforementioned intermediate lens group includes an object-side focusing group and an image-side focusing group. The optical system according to any one of configurations 1 to 31, characterized in that the object-side focus group and the image-side focus group move toward the object side on different trajectories when focusing from infinity to near. (Composition 33) The optical system according to configuration 32, characterized in that the object-side focus group and the image-side focus group each have a positive refractive power. (Composition 34) The optical system according to configuration 32, characterized in that the object-side focus group has a negative refractive power and the image-side focus group has a positive refractive power. (Composition 35) When TTL is defined as the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the optical system, plus the air-equivalent distance along the optical axis from the lens surface closest to the image to the image plane, 0.80 ≤ TTL / f ≤ 2.00 An optical system according to any one of configurations 1 to 34, characterized by satisfying the following conditions. (Composition 36) An optical system comprising a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side, During focusing, the front and rear lens groups do not move, but the intermediate lens group moves, changing the spacing between adjacent lens groups. The aforementioned front, intermediate, and rear lens groups each include multiple lenses. The aforementioned front lens group has the positive lens closest to the object, The aforementioned rear lens group has the negative lens closest to the image. An optical system characterized by having a total number of lenses included in the optical system being 12 or less. (Composition 37) An optical system comprising a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side, During focusing, the distance between adjacent lens groups changes. The optical system is characterized in that each of the aforementioned front, intermediate, and rear lens groups includes multiple lenses. (Composition 38) The optical system described in any one of configurations 1 to 37, An imaging device characterized by having an image sensor that captures an image of a subject through the optical system.

[0093] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of Symbols]

[0094] GF front lens group GM Intermediate Lens Group GR rear lens group IMG image plane SP aperture diaphragm

Claims

1. An optical system comprising a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side, During focusing, the front and rear lens groups do not move, but the intermediate lens group moves, changing the spacing between adjacent lens groups. The aforementioned front, intermediate, and rear lens groups each include multiple lenses. The aforementioned front lens group has the positive lens closest to the object, The aforementioned rear lens group has the negative lens closest to the image. The total number of lenses included in the optical system is 12 or less. When Bf is the air-equivalent distance along the optical axis from the image-side lens surface to the image plane of the optical system, fM is the focal length of the intermediate lens group when it is in focus on an object at infinity, and f is the focal length of the optical system when it is in focus on an object at infinity, 0.03 ≤ Bf / f ≤ 0.38 0.30 ≤ fM / f ≤ 0.85 An optical system characterized by satisfying the following conditions.

2. An optical system comprising a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side, During focusing, the front and rear lens groups do not move, but the intermediate lens group moves, changing the spacing between adjacent lens groups. The aforementioned front, intermediate, and rear lens groups each include multiple lenses. The aforementioned front lens group has the positive lens closest to the object, The total number of lenses included in the optical system is 13 or less. When Bf is the air-equivalent distance along the optical axis from the image-side lens surface to the image plane of the optical system, fM is the focal length of the intermediate lens group when focused on an object at infinity, f is the focal length of the optical system when focused on an object at infinity, and F is the maximum aperture F-number of the optical system, 0.03 ≤ Bf / f ≤ 0.38 0.30 ≤ fM / f ≤ 0.85 1.00 ≤ F ≤ 1.85 An optical system characterized by satisfying the following conditions.

3. When the focal length of the aforementioned front lens group is fF, 1.00 ≤ fF / f ≤ 5.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

4. When the focal length of the aforementioned rear lens group is fR, -100.00 ≤ fR / f ≤ -0.30 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

5. When the focal length of the aforementioned front lens group is fF, 1.20 ≤ fF / fM ≤ 7.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

6. When the focal length of the aforementioned rear lens group is fR, -100.00 ≤ fR / fM ≤ -0.80 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

7. The negative lens included in the aforementioned front lens group has a refractive index of nd_Fn on the d line, an Abbe number with respect to the d line νd_Fn, and a partial dispersion ratio of θgF_Fn on the g line and F line, ×10 －Ｘ When we denote this as E - X, 1.50≦nd_Fn≦2.35-0.015×νd_Fn 20.0 ≤ νd_Fn ≤ 60.0 -0.100≦θ'F_Fn-(-9.529E-8×ν$_Fn ３ +3.694E-5×νd_Fn ２ -4.717E-3×νd_Fn+7.139E-1)≦0.000 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

8. The negative lens positioned closest to the image in the aforementioned rear lens group has an Abbe number of νd_Rn1 with respect to the d line of the negative lens, and a partial dispersion ratio of θgF_Rn1 between the g line and the F line, × 10 －Ｘ When we denote this as E - X, 15.0 ≤ νd_Rn1 ≤ 55.0 -0.010≦θgF_Rn1-(-9.529E-8×νd_Rn1 ３ +3.694E-5×νd_Rn1 ２ -4.717E-3×νd_Rn1+7.139E-1)≦0.050 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

9. The aforementioned rear lens group has a negative lens as the second from the image side. The Abbe number of the second negative lens with respect to the d line is νd_Rn2, the partial dispersion ratio between the g line and the F line is θgF_Rn2, ×10 －Ｘ When we denote this as E - X, 15.0 ≤ νd_Rn2 ≤ 55.0 -0.010≦θgF_Rn2-(-9.529E-8*νd_Rn2 ３ +3.694E-5×νd_Rn2 ２ -4.717E-3×νd_Rn2+7.139E-1)≦0.050 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

10. The optical system according to claim 1 or 2, characterized in that the positive lens closest to the object in the front lens group is a meniscus lens with a convex surface facing the object.

11. The optical system according to claim 1 or 2, characterized in that the second lens from the object side in the aforementioned front lens group is a meniscus lens with a convex surface facing the object side.

12. The optical system according to claim 1 or 2, characterized in that the third lens from the object side of the aforementioned front lens group is a meniscus lens with a convex surface facing the object side.

13. The optical system according to claim 1 or 2, characterized in that the fourth lens from the object side of the aforementioned front lens group is a meniscus lens with a convex surface facing the object side.

14. The optical system according to claim 1 or 2, characterized in that the total number of lenses included in the aforementioned front lens group is five or less.

15. The optical system according to claim 1 or 2, characterized in that the total number of lenses included in the intermediate lens group is four or less.

16. The optical system according to claim 1 or 2, characterized in that the total number of lenses included in the rear lens group is five or less.

17. The optical system according to claim 1 or 2, characterized in that each of the front, intermediate, and rear lens groups includes at least one positive lens and at least one negative lens.

18. The optical system according to claim 1 or 2, characterized in that the front lens group includes at least two positive lenses with an Abbe number of 60 or more with respect to the d line.

19. The optical system according to claim 1 or 2, characterized in that the intermediate lens group includes at least one aspherical lens.

20. When the image lateral magnification of the intermediate lens group is focused on an object at infinity, let βM be the magnification of the intermediate lens group. 0.20 ≤ βM ≤ 1.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

21. When the image lateral magnification of the rear lens group is focused on an object at infinity, let βR be the magnification of the rear lens group. 0.50 ≤ βR ≤ 2.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

22. When the image lateral magnification of the intermediate lens group when focused on an object at infinity is βM, and the image lateral magnification of the rear lens group when focused on an object at infinity is βR, 0.30≦(1-βM) ２ )×βR ２ ≦2.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

23. The optical system has an aperture diaphragm, When the distance along the optical axis from the aperture diaphragm to the image plane is denoted as dsp_R, 0.50≦dsp_R / f≦2.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

24. When the focal length of the negative lens with the strongest refractive power among the at least one negative lens included in the aforementioned front lens group is fF_n1, -0.80≦fF_n1 / f≦-0.20 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

25. The optical system according to claim 1 or 2, characterized in that the optical system has an aperture diaphragm between the front lens group and the intermediate lens group.

26. When the combined focal length of the front lens group and the intermediate lens group is fFM in a state where they are in focus on an object at infinity, 0.40 ≤ fFM / f ≤ 1.50 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

27. When the combined focal length of the intermediate lens group and the rear lens group is fMR in a state where they are in focus on an object at infinity, 0.40 ≤ fMR / f ≤ 1.50 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

28. When the focal length of the negative lens positioned closest to the image side in the aforementioned rear lens group is fRn1, -5.00 ≤ fRn1 / f ≤ -0.30 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

29. When the focal length of the positive lens closest to the object in the front lens group is fFp1, 1.20 ≤ fFp1 / f ≤ 10.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

30. When the focal length of the positive lens second from the object side in the aforementioned front lens group is fFp2, 0.30 ≤ fFp² / f ≤ 2.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

31. The optical system according to claim 1 or 2, characterized in that at least one positive lens included in the rear lens group has a refractive index of 1.850 or less on the d line and an Abbe number of 50.0 or less with respect to the d line.

32. The aforementioned intermediate lens group includes an object-side focusing group and an image-side focusing group. The optical system according to claim 1 or 2, characterized in that the object-side focus group and the image-side focus group move toward the object side on different trajectories when focusing from infinity to near.

33. The optical system according to claim 32, characterized in that the object-side focus group and the image-side focus group each have a positive refractive power.

34. The optical system according to claim 32, characterized in that the object-side focus group has a negative refractive power and the image-side focus group has a positive refractive power.

35. When TTL is defined as the distance along the optical axis from the lens surface closest to the object to the lens surface closest to the image of the optical system, plus the equivalent distance along the optical axis from the lens surface closest to the image to the image plane, 0.80 ≤ TTL / f ≤ 2.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditions.

36. An optical system comprising a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side, During focusing, the front and rear lens groups do not move, but the intermediate lens group moves, changing the spacing between adjacent lens groups. The aforementioned front, intermediate, and rear lens groups each include multiple lenses. The aforementioned front lens group has the positive lens closest to the object, The aforementioned rear lens group has the negative lens closest to the image. An optical system characterized in that the total number of lenses included in the optical system is 12 or less.

37. An optical system comprising a front lens group with positive refractive power, an intermediate lens group with positive refractive power, and a rear lens group with negative refractive power, arranged in order from the object side to the image side, During focusing, the distance between adjacent lens groups changes. The optical system is characterized in that the aforementioned front, intermediate, and rear lens groups each include multiple lenses.

38. An optical system according to any one of claims 1 to 37, An imaging device characterized by having an image sensor that captures an image of a subject through the optical system.

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