Optical system, optical device, interchangeable lens, and optical system manufacturing method

Abstract

This optical system that has, in order from the object side, a front group having positive refractive power, an aperture stop, and a rear group, is configured so as to satisfy the following conditional expressions: (1) 0.10<ff / │fr│<1.50; (2) 0.13<tr / TL<0.45; and (3) 0.50<f / TL<1.20, where ff is the focal length of the front group, fr is the focal length of the rear group, tr is the sum of the center thicknesses of lenses included in the rear group, TL is the total length of the optical system, and f is the focal length of the optical system.

Description

Optical system, optical device, interchangeable lens, and method of manufacturing optical system

[0001] The present disclosure relates to an optical system, an optical instrument, an interchangeable lens, and a method for manufacturing an optical system.

[0002] 2. Description of the Related Art Conventionally, optical systems have been proposed for use in optical devices such as photographic cameras, electronic still cameras, and video cameras (see, for example, Japanese Patent Application Laid-Open No. 2003-222294).

[0003] International Publication No. 2019 / 187633

[0004] The optical system of the present disclosure has, in order from the object side, a front group having positive refractive power, an aperture stop, and a rear group, and satisfies the following conditional expressions: 0.10 < ff / |fr| < 1.50 0.13 < tr / TL < 0.45 0.50 < f / TL < 1.20 where, ff: focal length of the front group fr: focal length of the rear group tr: sum of center thicknesses of the lenses included in the rear group TL: total length of the optical system f: focal length of the optical system

[0005] The method for manufacturing an optical system according to the present disclosure includes constructing an optical system having, in order from the object side, a front group having positive refractive power, an aperture stop, and a rear group, so as to satisfy all of the following conditional expressions: 0.10 < ff / |fr| < 1.50 0.13 < tr / TL < 0.45 0.50 < f / TL < 1.20 where, ff: focal length of the front group fr: focal length of the rear group tr: sum of center thicknesses of the lenses included in the rear group TL: total length of the optical system f: focal length of the optical system

[0006] 1. A cross-sectional view of the optical system of Example 1 when focusing on an object at infinity. FIG. 2. A cross-sectional view of the optical system of Example 1 when focusing on an object at infinity. FIG. 3. A cross-sectional view of the optical system of Example 2 when focusing on an object at infinity. FIG. 4. A cross-sectional view of the optical system of Example 3 when focusing on an object at infinity. FIG. 5. A cross-sectional view of the optical system of Example 4 when focusing on an object at infinity. FIG. 6. A cross-sectional view of the optical system of Example 5 when focusing on an object at infinity. FIG. 7. A cross-sectional view of the optical system of Example 7 when focusing on an object at infinity. FIG. 8. A cross-sectional view of the optical system of Example 8 when focusing on an object at infinity. FIG. 9. A cross-sectional view of the optical system of Example 9 when focusing on an object at infinity. FIG. 10. Fig. 10 is a cross-sectional view of the optical system of Example 10 when focusing on an object at infinity. Fig. 11 is a diagram showing various aberrations of the optical system of Example 10. Fig. 12 is a schematic diagram of a camera equipped with the optical system of this embodiment. Fig. 13 is a flowchart showing an outline of a method for manufacturing the optical system of this embodiment.

[0007] An optical system, an optical device, and a method for manufacturing an optical system according to embodiments of the present application will be described below.

[0008] The optical system of this embodiment has, in order from the object side, a front group having positive refractive power, an aperture stop, and a rear group, and satisfies the following conditional expressions: (1) 0.10 < ff / |fr| < 1.50 (2) 0.13 < tr / TL < 0.45 (3) 0.50 < f / TL < 1.20 where, ff: focal length of the front group, fr: focal length of the rear group, tr: sum of center thicknesses of the lenses included in the rear group, TL: total length of the optical system, f: focal length of the optical system.

[0009] In the optical system of this embodiment, the front group has positive refractive power, so that the principal point can be located on the object side, and therefore the overall length can be made short relative to the focal length.

[0010] Conditional expression (1) defines the ratio between the focal length of the front group and the focal length of the rear group. By satisfying conditional expression (1), the optical system of this embodiment can appropriately correct various aberrations, including spherical aberration, coma, curvature of field, and distortion, while preventing the optical system from becoming too large.

[0011] In the optical system of this embodiment, if the value of conditional expression (1) exceeds the upper limit, the refractive power of the front group becomes too strong, causing high-order spherical aberration, coma, field curvature, and distortion, making it difficult to appropriately correct various aberrations.

[0012] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (1) to 1.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (1) to 1.40, 1.30, 1.20, 1.10, or even 1.00.

[0013] Furthermore, in the optical system of this embodiment, if the value of conditional expression (1) is below the lower limit, the refractive power of the front group becomes too weak, the overall length of the optical system becomes long, the lens diameter becomes large, and the optical system becomes large.

[0014] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (1) to 0.10. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.15, 0.19, or even 0.40.

[0015] Conditional expression (2) defines the ratio of the sum of the center thicknesses of the lenses in the rear group to the overall length of the optical system. By satisfying conditional expression (2), the optical system of this embodiment can suppress increases in size and weight.

[0016] In the optical system of this embodiment, if the value of conditional expression (2) exceeds the upper limit, the lens thickness increases, and the weight of the optical system also increases.

[0017] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (2) to 0.45. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.40, 0.35, or even 0.30.

[0018] Furthermore, in the optical system of this embodiment, if the value of conditional expression (2) is below the lower limit, the overall length of the optical system becomes long, and the optical system becomes large.

[0019] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (2) to 0.13. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (2) to 0.14, 0.15, 0.16, or even 0.17.

[0020] Conditional expression (3) defines the ratio between the focal length of the optical system and the overall length of the optical system. By satisfying conditional expression (3), the optical system of this embodiment can appropriately correct various aberrations, including spherical aberration, coma, curvature of field, and distortion, while preventing the optical system from becoming too large.

[0021] In the optical system of this embodiment, if the value of conditional expression (3) exceeds the upper limit, it becomes difficult to appropriately correct various aberrations, including spherical aberration, coma, curvature of field, and distortion.

[0022] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (3) to 1.20. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (3) to 1.15, 1.10, 1.05, or even 1.00.

[0023] Furthermore, in the optical system of this embodiment, if the value of conditional expression (3) falls below the lower limit, the overall length of the optical system becomes long, and the optical system becomes large.

[0024] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (3) to 0.50. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.55, 0.60, 0.65, 0.70, or even 0.80.

[0025] The optical system of this embodiment satisfies conditional expressions (1), (2), and (3), and thereby can appropriately correct various aberrations, including spherical aberration, coma, field curvature, and distortion, while suppressing increases in the size and weight of the optical system.

[0026] In the optical system of this embodiment, it is preferable that the rear group has negative refractive power.

[0027] With the optical system of this embodiment, by having such a configuration, the overall length of the optical system can be shortened and spherical aberration can be appropriately corrected.

[0028] It is also preferable that the optical system of this embodiment satisfy the following condition (4): 0.05<fPr / |fr|<0.70, where fPr is the focal length of the single lens Pr having the strongest refractive power among the biconvex single lenses in the rear group.

[0029] Conditional expression (4) defines the ratio between the focal length of the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group and the focal length of the rear group. By satisfying conditional expression (4), the optical system of this embodiment can appropriately correct various aberrations, including coma and curvature of field, while suppressing an increase in size of the optical system.

[0030] In the optical system of this embodiment, if the value of conditional expression (4) exceeds the upper limit, the refractive power of the rear group becomes too weak, the overall length of the optical system becomes long, the lens diameter becomes large, and the optical system becomes large in size.

[0031] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (4) to 0.70. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.65, 0.60, or even 0.40.

[0032] Furthermore, in the optical system of this embodiment, if the value of conditional expression (4) falls below the lower limit, the refractive power of the single lens Pr becomes too strong, causing high-order coma aberration and curvature of field, making it difficult to appropriately correct various aberrations.

[0033] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (4) to 0.05. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.06, 0.07, 0.08, 0.09, 0.10, or even 0.20.

[0034] Furthermore, it is preferable that the optical system of this embodiment has at least one focusing group that moves during focusing, and satisfies the following condition (5): 0.05<fPfoi / |fr|<0.50, where fPfoi is the focal length of the single lens Pfoi with the strongest refractive power among the biconvex single lenses that are located closer to the image plane than the focusing group Gfo that is located closest to the object among the at least one focusing group.

[0035] Conditional expression (5) defines the ratio between the focal length of the single lens Pfoi and the focal length of the rear group. By satisfying conditional expression (5), the optical system of this embodiment can suppress the occurrence of spherical aberration, coma, and curvature of field while preventing the optical system from becoming large.

[0036] In the optical system of this embodiment, if the value of conditional expression (5) exceeds the upper limit, the refractive power of the single lens fPfoi becomes too weak, and the overall length of the optical system becomes long.

[0037] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (5) to 0.70. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (5) to 0.65, 0.60, or even 0.40.

[0038] Furthermore, in the optical system of this embodiment, if the value of conditional expression (5) falls below the lower limit, the refractive power of the single lens Pfoi becomes too strong, making it difficult to properly correct various aberrations, including spherical aberration, coma, and field curvature.

[0039] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (5) to 0.05. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (5) to 0.06, 0.07, 0.08, 0.09, 0.10, or even 0.20.

[0040] It is also preferable that the optical system of this embodiment has at least one focusing group that moves during focusing, and satisfies the following condition (6): 0.25<fPfoi / f<0.55

[0041] Conditional expression (6) defines the ratio between the focal length of the single lens Pfoi and the focal length of the optical system. By satisfying conditional expression (6), the optical system of this embodiment can suppress the occurrence of spherical aberration, coma, and curvature of field while suppressing an increase in size of the optical system.

[0042] In the optical system of this embodiment, if the value of conditional expression (6) exceeds the upper limit, the refractive power of the single lens Pfoi becomes too weak, the overall length of the optical system becomes long, the lens diameter becomes large, and the optical system becomes large. Also, if the value of conditional expression (6) exceeds the upper limit, it becomes difficult to appropriately correct various aberrations, including spherical aberration, coma, and curvature of field.

[0043] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (6) to 0.55. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (6) to 0.50, 0.48, 0.46, or even 0.40.

[0044] Furthermore, in the optical system of this embodiment, if the value of conditional expression (6) falls below the lower limit, the refractive power of the single lens Pfoi becomes too strong, making it difficult to properly correct various aberrations, including spherical aberration, coma, and field curvature.

[0045] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (6) to 0.25. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (6) to 0.28, 0.30, or even 0.31.

[0046] It is also preferable that the optical system of this embodiment satisfy the following conditional expression (7): 0.05<Da / Bf<1.10, where Da is the distance on the optical axis between the object-side lens surface of the lens Li1 located closest to the image plane and the image-side lens surface of the lens Li2 located adjacent to the lens Li1 on the object side, when focusing at infinity; Bf is the back focus in terms of air equivalent length.

[0047] Conditional expression (7) defines the ratio of the distance on the optical axis between the object-side lens surface of lens Li1 and the image-side lens surface of lens Li2 when focusing at infinity to the back focus in terms of the air-equivalent length of the optical system. By satisfying conditional expression (7), the optical system of this embodiment can appropriately correct various aberrations, including curvature of field, coma, and distortion.

[0048] In the optical system of this embodiment, if the value of conditional expression (7) exceeds the upper limit, it becomes difficult to appropriately correct curvature of field and coma.

[0049] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (7) to 1.10. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (7) to 1.05, and more preferably 1.00.

[0050] Furthermore, in the optical system of this embodiment, if the value of conditional expression (7) falls below the lower limit, it becomes difficult to appropriately correct curvature of field and distortion.

[0051] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (7) to 0.05. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (7) to 0.06, and more preferably 0.07.

[0052] In the optical system of this embodiment, it is preferable that the rear group has a plurality of lens groups including at least one focusing group that moves during focusing, the distance between the plurality of lens groups changing during focusing, and that the following condition be satisfied: (8) 0.30 < tGi / Da < 9.00, where tGi is the sum of the lengths on the optical axis of the lenses included in the lens group Gi that is located closest to the image among the plurality of lens groups.

[0053] Conditional expression (8) defines the ratio of the sum of the axial lengths of the lenses included in lens group Gi to the axial distance between the object-side lens surface of lens Li1 and the image-plane-side lens surface of lens Li2 when focusing at infinity. By satisfying conditional expression (8), the optical system of this embodiment can appropriately correct various aberrations, including curvature of field and distortion, while suppressing an increase in the weight of the optical system.

[0054] In the optical system of this embodiment, if the value of conditional expression (8) exceeds the upper limit, the lens thickness of the lens group Gi becomes too large, and the weight of the optical system increases.

[0055] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (8) to 9.00. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (8) to 8.50, 8.00, 7.80, 7.60, or even 3.00.

[0056] Furthermore, in the optical system of this embodiment, if the value of conditional expression (8) falls below the lower limit, it becomes difficult to appropriately correct various aberrations, including curvature of field and distortion.

[0057] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (8) to 0.30. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (8) to 0.32, 0.34, 0.60, 1.00, or even 1.50.

[0058] It is also preferable that the optical system of this embodiment satisfy the following condition: 0.40<D1 / TL<0.85 (9), where D1 is the distance on the optical axis between the lens surface closest to the object and the object-side surface of the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, when focusing at infinity.

[0059] Conditional expression (9) defines the ratio of the axial distance between the lens surface closest to the object and the lens surface closest to the object of the single lens Pr when focusing at infinity to the overall length of the optical system. By satisfying conditional expression (9), the optical system of this embodiment can appropriately correct various aberrations, including spherical aberration, coma, curvature of field, and distortion, while preventing the optical system from becoming too large.

[0060] In the optical system of this embodiment, if the value of conditional expression (9) exceeds the upper limit, the refractive power between the lens surface closest to the object and the lens surface of the single lens Pr closest to the object becomes too weak, the lens diameter increases, and the optical system becomes large.

[0061] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (9) to 0.85. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (9) to 0.84, 0.82, or even 0.80.

[0062] Furthermore, in the optical system of this embodiment, if the value of conditional expression (9) falls below the lower limit, the refractive power between the lens surface closest to the object and the lens surface of the single lens Pr closest to the object becomes too strong, causing high-order spherical aberration, coma, curvature of field, and distortion, making it difficult to appropriately correct various aberrations.

[0063] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (9) to 0.40. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (9) to 0.45, and more preferably 0.50.

[0064] It is also preferable that the optical system of this embodiment satisfy the following condition: 0.10<D2 / TL<0.80 (10), where D2 is the distance on the optical axis between the aperture stop and the object-side lens surface of the biconvex single lens Pr that has the strongest refractive power among the single lenses in the rear group.

[0065] Conditional expression (10) defines the ratio of the axial distance between the aperture stop and the object-side lens surface of the single lens Pr to the overall length of the optical system. By satisfying conditional expression (10), the optical system of this embodiment can appropriately correct various aberrations, including spherical aberration, coma, field curvature, and distortion, while preventing the optical system from becoming too large.

[0066] In the optical system of this embodiment, if the value of conditional expression (10) exceeds the upper limit, the refractive power between the aperture stop and the object-side lens surface of the single lens Pr becomes too weak, the lens diameter increases, and the optical system becomes large.

[0067] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (10) to 0.80. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (10) to 0.70, 0.60, 0.50, 0.40, or even 0.36.

[0068] Furthermore, in the optical system of this embodiment, if the value of conditional expression (10) falls below the lower limit, the refractive power between the aperture stop and the object-side lens surface of the single lens Pr becomes too strong, causing higher-order spherical aberration, coma, field curvature, and distortion, making it difficult to appropriately correct various aberrations.

[0069] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (10) to 0.10. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (10) to 0.11, 0.12, or even 0.13.

[0070] It is also preferable that the optical system of this embodiment has at least one focusing group that moves during focusing, and satisfies the following condition: 0.25<|ffo| / f<0.90 (11), where ffo is the focal length of the focusing group Gfo that is located closest to the object side among the at least one focusing group.

[0071] Conditional expression (11) defines the ratio between the focal length of the focusing group Gfo located closest to the object and the focal length of the optical system. By satisfying conditional expression (11), the optical system of this embodiment can appropriately correct various aberrations, including spherical aberration, coma, curvature of field, and distortion, while suppressing an increase in the overall length of the optical system.

[0072] In the optical system of this embodiment, if the value of conditional expression (11) exceeds the upper limit, it becomes difficult to suppress fluctuations in various aberrations, including spherical aberration, coma, field curvature, and distortion, during focusing.

[0073] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (11) to 0.90. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (11) to 0.85, and more preferably 0.80.

[0074] Furthermore, in the optical system of this embodiment, if the value of conditional expression (11) falls below the lower limit, the refractive power of the focusing group located closest to the object becomes too weak, and the amount of movement of the focusing group during focusing increases, thereby increasing the overall length of the optical system.

[0075] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (11) to 0.25. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (11) to 0.26, 0.28, 0.30, 0.31, or even 0.32.

[0076] In the optical system of this embodiment, it is preferable that the front group has at least one positive lens Pf that satisfies both of the following conditional expressions: (12) 1.60<ndPf (13) νdPf<31.00 (14) 0.01<θgFPf-(0.6415-0.00162×νdPf) where, ndPf: refractive index of the positive lens Pf for the d-line νdPf: Abbe number of the positive lens Pf based on the d-line θgFPf: partial dispersion ratio of the positive lens Pf, which is defined by the following expression when the refractive index of the positive lens Pf for the g-line is ngPf, the refractive index of the positive lens Pf for the F-line is nFPf, and the refractive index of the positive lens Pf for the C-line is nCPf. θgFPf=(ngPf-nFPf) / (nFPf-nCPf)

[0077] The optical system of this embodiment has at least one positive lens Pf in the front group, so that various aberrations including axial chromatic aberration can be appropriately corrected.

[0078] In the optical system of this embodiment, the value of conditional expression (12) for the positive lens Pf is set to be greater than the lower limit, thereby making it possible to suppress the occurrence of high-order aberrations.

[0079] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (12) to 1.60. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (12) to 1.62, 1.64, or even 1.66.

[0080] In the optical system of this embodiment, by making the value of conditional expression (13) for the positive lens Pf smaller than the upper limit, the second-order dispersion of axial chromatic aberration can be corrected satisfactorily.

[0081] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (13) to 31.00. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (13) to 29.50, 28.00, or even 27.50.

[0082] In the optical system of this embodiment, by making the value of conditional expression (14) for the positive lens Pf greater than the lower limit, the second-order dispersion of axial chromatic aberration can be corrected satisfactorily.

[0083] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (14) to 0.01. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (14) to 0.015, 0.02, or even 0.025.

[0084] In the optical system of this embodiment, it is preferable that the front group has at least one negative lens Nf that satisfies both of the following conditional expressions: (15) 1.85<ndNf (16) νdNf<26.00 (17) θgFNf-(0.6415-0.00162×νdNf)<0.015 where, ndNf: refractive index of the negative lens Nf for the d-line νdNf: Abbe number of the negative lens Nf based on the d-line θgFNf: partial dispersion ratio of the negative lens Nf, which is defined by the following expression when the refractive index of the negative lens Nf for the g-line is ngNf, the refractive index of the negative lens Nf for the F-line is nFNf, and the refractive index of the negative lens Nf for the C-line is nCNf. θgFNf = (ngNf-nFNf) / (nFNf-nCNf)

[0085] The optical system of this embodiment has at least one negative lens Nf in the front group, making it possible to appropriately correct various aberrations including axial chromatic aberration.

[0086] In the optical system of this embodiment, the value of conditional expression (15) for the negative lens Nf is set to be greater than the lower limit, thereby making it possible to suppress the occurrence of high-order aberrations.

[0087] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (15) to 1.85.

[0088] In the optical system of this embodiment, by making the value of conditional expression (16) for the negative lens Nf smaller than the upper limit, the second-order dispersion of axial chromatic aberration can be corrected satisfactorily.

[0089] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (16) to 26.00. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (16) to 25.80, 25.50, or even 25.20.

[0090] In the optical system of this embodiment, by making the value of conditional expression (17) for the negative lens Nf smaller than the upper limit, the second-order dispersion of axial chromatic aberration can be corrected satisfactorily.

[0091] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (17) to 0.015. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (17) to 0.013, 0.012, or even 0.01.

[0092] With the above configuration, it is possible to realize an optical system that is small in size and has good optical performance.

[0093] The optical device of this embodiment includes the optical system having the above-described configuration, thereby realizing an optical device that is small in size and has good optical performance.

[0094] The interchangeable lens of this embodiment includes the optical system configured as described above, thereby realizing an interchangeable lens that is small in size and has good optical performance.

[0095] The method for manufacturing the optical system of this embodiment includes constructing an optical system having, in order from the object side, a front group having positive refractive power, an aperture stop, and a rear group, so as to satisfy all of the following conditional expressions: (1) 0.10 < ff / |fr| < 1.50 (2) 0.13 < tr / TL < 0.45 (3) 0.50 < f / TL < 1.20 where, ff: focal length of the front group, fr: focal length of the rear group, tr: sum of center thicknesses of the lenses included in the rear group, TL: total length of the optical system, f: focal length of the optical system.

[0096] By using such a manufacturing method for an optical system, it is possible to manufacture an optical system that is small in size and has good optical performance.

[0097] Numerical Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

[0098] First Embodiment FIG. 1 is a cross-sectional view of an optical system of a first embodiment when focusing on an object at infinity.

[0099] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.

[0100] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus positive lens L3 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, an aperture stop S, and a meniscus positive lens L6 with a convex surface facing the object side.

[0101] The second lens group G2 is made up of a negative meniscus lens L7 with its convex surface facing the object side.

[0102] The third lens group G3 consists of, in order from the object side, a meniscus positive lens L8 with its concave surface facing the object side, a cemented negative lens consisting of a biconcave negative lens L9 and a meniscus positive lens L10 with its convex surface facing the object side, a biconvex positive lens L11, and a meniscus negative lens L12 with its convex surface facing the object side.

[0103] The fourth lens group G4 is made up of a positive meniscus lens L13 with its convex surface facing the object side.

[0104] The fifth lens group G5 comprises, in order from the object side, a biconcave negative lens L14, a meniscus positive lens L15 with its convex surface facing the object side, and a meniscus negative lens L16 with its concave surface facing the object side.

[0105] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0106] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0107] The optical system of this embodiment focuses by moving the second lens group G2 and the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the object side to the image plane side, and the fourth lens group G4 is moved from the image plane side to the object side.

[0108] In the optical system of this embodiment, the positive lens L1 to the negative lens L5 of the first lens group G1 correspond to the front group, and the positive lens L6 of the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group. The second lens group G2 and the fourth lens group G4 correspond to focusing groups that move during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The fifth lens group corresponds to the lens group Gi located closest to the image.

[0109] In the optical system of this embodiment, the positive lens L11 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L16 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L15 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side. The positive lens L1 corresponds to the positive lens Pf in the front group, and the negative lens L5 corresponds to the negative lens Nf in the front group.

[0110] Table 1 below lists the specifications of the optical system of this example.

[0111] In the [Overall Specifications], f is the focal length of the entire optical system, ff is the focal length of the front group, fr is the focal length of the rear group, TL is the distance from the lens surface closest to the object to the image plane, Bf is the back focus in air equivalent length of the optical system, FNO is the F-number of the optical system, and Y is the maximum image height.

[0112] In the [Lens Specifications], m is the order of the optical surface counted from the object side, r is the radius of curvature, d is the surface spacing, nd is the refractive index for the d-line (wavelength 587.6 nm), and νd is the Abbe number for the d-line. A radius of curvature r=∞ indicates a flat surface. Additionally, in the [Lens Specifications], optical surfaces marked with an "*" are aspherical.

[0113] In [Aspherical Data], m indicates the optical surface corresponding to the aspherical data, K indicates the conic constant, and A4-A10 indicate the aspherical coefficients.

[0114] The aspherical surface is expressed by the following formula (a), where y is the height in the direction perpendicular to the optical axis, S(y) is the distance (amount of sag) along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface, r is the radius of curvature (paraxial radius of curvature) of the reference spherical surface, K is the conic constant, and An is the n-th order aspherical coefficient. In each example, the second order aspherical coefficient A2 is 0. Also, "En" is expressed as "×10 －ｎ " indicates.

[0115] (a) S(y) = (y ２ / r) / 1 + (1-K×y ２ / r ２ ) １／２ + A4×y ４ + A6×y ６ + A8×y ８ + A10×y １０

[0116] The focal length f, radius of curvature r, and other lengths listed in Table 1 are in units of mm. However, this is not limited to this because the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0117] The symbols in Table 1 described above are similarly used in tables of other examples to be described later.

[0118] (Table 1) [Overall specifications] f 132.30 ff 113.43 fr -227.10 TL 147.45 Bf 13.89 FNO 1.85 Y 21.70 [Lens specifications] m r d nd νd 1) 73.0739 8.2580 1.66382 27.35 2) 173.9425 1.0000 3) 75.0000 8.0959 1.49782 82.57 4) 226.5221 1.0000 5) 94.0000 6.1837 1.49782 82.57 6) 255.7300 1.0000 7) 55.0000 10.2480 1.49782 82.57 8) -766.4853 2.1000 1.85451 25.15 9) 50.0250 8.2444 10) ∞ 2.1000 (Aperture stop) *11) 105.9598 4.7000 1.51680 64.14 12) 853.5480 D12 13) 221.6993 2.1000 1.69680 55.52 14) 39.4223 D14 15) -164.4380 4.0545 1.80809 22.74 16) -75.4132 0.1000 17) -160.7346 2.1000 1.85451 25.15 18) 80.4120 3.2958 1.59319 67.90 19) 157.8647 0.7213 20) 64.0655 9.2661 1.80440 39.61 21) -101.7863 0.1000 22) 195.9905 2.2000 1.83481 42.73 23) 83.1844 D23 24) 85.1050 4.4549 1.85883 30.00 25) 380.6074 D25 26) -542.5119 2.1000 1.78590 44.17 27) 62.2755 1.0000 28) 51.4253 5.3074 1.84666 23.78 29) 162.7875 4.3017 30) -70.4474 2.1000 1.81600 46.59 31) -2372.9554 11.4681 32) ∞ 1.6000 1.51680 64.14 33) ∞ 1.3712 [Aspherical surface data] m K A4 A6 A8 A10 11) 1.0000 -1.741E-06 -1.130E-10 -2.868E-14 9.211E-17 [Focal length data for each group] Group Initial surface Focal length G1 1 89.30 G2 13 -69.14 G3 15 116.43 G4 24 126.75 G5 26 -71.11 [Variable distance data] When focusing at infinity When focusing at close range D12 1.749 15.346 D14 22.105 8.507 D23 9.528 3.345 D25 3.500 9.684.

[0119] FIG. 2 is a diagram showing various aberrations of the optical system of the first embodiment.

[0120] In each aberration diagram, FNO indicates the F-number, and A indicates the image height. More specifically, spherical aberration diagrams indicate the F-number value corresponding to the maximum aperture, astigmatism diagrams and distortion diagrams indicate the maximum image height, and coma diagrams indicate the value of each image height. d indicates the d-line, and g indicates the g-line (wavelength 435.8 nm). In astigmatism diagrams, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. The same symbols as those used in the aberration diagrams of this embodiment are used in the aberration diagrams of other embodiments described below.

[0121] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0122] Second Example FIG. 3 is a cross-sectional view of an optical system of a second example when focusing on an object at infinity.

[0123] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.

[0124] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus positive lens L3 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a biconvex positive lens L6.

[0125] The second lens group G2 is made up of a negative meniscus lens L7 with its convex surface facing the object side.

[0126] The third lens group G3 is composed of, in order from the object side, a cemented negative lens of a biconcave negative lens L8 and a meniscus positive lens L9 with its convex surface facing the object side, a biconvex positive lens L10, and a meniscus negative lens L11 with its convex surface facing the object side.

[0127] The fourth lens group G4 is made up of a positive meniscus lens L12 with its convex surface facing the object side.

[0128] The fifth lens group G5 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus negative lens L13 with its convex surface facing the object side and a biconvex positive lens L14, and a biconcave negative lens L15.

[0129] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0130] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0131] The optical system of this embodiment focuses by moving the second lens group G2 and the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the object side to the image plane side, and the fourth lens group G4 is moved from the image plane side to the object side.

[0132] In the optical system of this embodiment, the first lens group G1 corresponds to the front group, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group. The second lens group G2 and the fourth lens group G4 correspond to focusing groups that move during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The fifth lens group corresponds to the lens group Gi located closest to the image.

[0133] In the optical system of this embodiment, the positive lens L10 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L15 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L14 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side. The positive lens L1 corresponds to the positive lens Pf in the front group, and the negative lens L5 corresponds to the negative lens Nf in the front group.

[0134] Table 2 below lists the specifications of the optical system of this example.

[0135] (Table 2) [Overall specifications] f 132.30 ff 84.98 fr -99.98 TL 144.99 Bf 15.36 FNO 1.85 Y 21.70 [Lens specifications] m r d nd νd 1) 71.4223 9.3392 1.66382 27.35 2) 212.8546 0.2000 3) 82.3011 6.8153 1.49782 82.57 4) 189.8030 4.0179 5) 67.8053 6.4147 1.49782 82.57 6) 146.3981 0.2000 7) 50.4121 9.6499 1.49782 82.57 8) -3183.7228 1.2000 1.85451 25.15 9) 43.4640 6.7260 *10) 98.1806 4.1632 1.51680 64.14 11) -1338.1241 1.6925 12) ∞ D12 (Aperture stop) 13) 187.4183 1.2000 1.69680 55.52 14) 37.4569 D14 15) -331.5883 1.2000 1.8466623.80 16) 72.4584 3.6449 1.59319 67.90 17) 187.4042 4.2922 18) 72.7147 9.0000 1.68376 37.64 19) -83.4441 0.2000 20) 85.5767 1.5000 2.00069 25.46 21) 60.8156 D21 22) 85.9402 4.5000 1.95000 29.37 23) 390.8660 D23 24) 229.3158 1.2000 1.88300 40.69 25) 41.6420 8.5000 1.85451 25.15 26) -188.3950 5.3350 *27) -58.0337 1.2000 1.79526 45.25 28) 127.2294 D28 29) ∞ 1.6000 1.51680 63.88 30) ∞ 1.0000 [Aspheric data] m K A4 A6 A8 A10 10) 1.0000 -1.415E-06 1.034E-10 -6.229E-13 6.524E-16 27) 1.0000 2.317E-06 2.412E-10 -4.722E-12 5.079E-15 [Each group focal length data] Group First plane Focal length G1 1 84.98 G2 13 -67.40 G3 15 220.38 G4 22 115.13 G5 24 -89.30 [Variable distance data] When focusing at infinity When focusing at close range D12 3.000 15.000 D14 19.761 7.761 D21 10.199 3.077 D23 3.934 11.057 D28 13.303 13.340.

[0136] FIG. 4 is a diagram showing various aberrations of the optical system of the second embodiment.

[0137] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0138] Third Embodiment FIG. 5 is a cross-sectional view of an optical system of a third embodiment when focusing on an object at infinity.

[0139] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.

[0140] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus positive lens L3 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, an aperture stop S, and a meniscus positive lens L6 with a convex surface facing the object side.

[0141] The second lens group G2 is made up of a negative meniscus lens L7 with its convex surface facing the object side.

[0142] The third lens group G3 is composed of, in order from the object side, a cemented negative lens of a biconcave negative lens L8 and a meniscus positive lens L9 with its convex surface facing the object side, a biconvex positive lens L10, and a meniscus negative lens L11 with its convex surface facing the object side.

[0143] The fourth lens group G4 is made up of a positive meniscus lens L12 with its convex surface facing the object side.

[0144] The fifth lens group G5 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus negative lens L13 with its convex surface facing the object side and a biconvex positive lens L14, and a biconcave negative lens L15.

[0145] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0146] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0147] The optical system of this embodiment focuses by moving the second lens group G2 and the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the object side to the image plane side, and the fourth lens group G4 is moved from the image plane side to the object side.

[0148] In the optical system of this embodiment, the positive lens L1 to the negative lens L5 of the first lens group G1 correspond to the front group, and the positive lens L6 of the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group. The second lens group G2 and the fourth lens group G4 correspond to focusing groups that move during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The fifth lens group corresponds to the lens group Gi located closest to the image.

[0149] In the optical system of this embodiment, the positive lens L10 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L15 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L14 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side. The positive lens L1 corresponds to the positive lens Pf in the front group, and the negative lens L5 corresponds to the negative lens Nf in the front group.

[0150] Table 3 below lists the specifications of the optical system of this example.

[0151] (Table 3) [Overall specifications] f 132.30 ff 112.47 fr -196.89 TL 145.00 Bf 15.00 FNO 1.84 Y 21.70 [Lens specifications] m r d nd νd 1) 71.7601 8.8107 1.66382 27.35 2) 184.7948 0.2000 3) 86.2502 7.1330 1.49782 82.57 4) 237.5854 3.4700 5) 69.0966 6.7579 1.49782 82.57 6) 167.1912 0.2000 7) 53.2464 9.4720 1.49782 82.57 8) -1820.1966 1.2000 1.85451 25.15 9) 47.3137 7.6169 10) ∞ 3.0000 (Aperture stop) 11) 92.4608 3.6037 1.51680 64.14 12) 557.2232 D12 13) 146.6010 1.2000 1.69680 55.52 14) 38.6158 D14 15) -234.1612 1.2000 1.85451 25.15 16) 77.2640 3.4308 1.59319 67.90 17) 165.0443 3.3299 18) 82.1496 9.0000 1.73800 32.33 19) -78.9827 0.2000 20) 90.3107 1.5000 1.90200 25.26 21) 67.5653 D21 22) 87.9013 4.5000 1.83481 42.73 23) 437.5569 D23 24) 191.2552 1.2000 1.88300 40.69 25) 40.4406 7.5029 1.85451 25.15 26) -998.5745 5.2026 27) -66.7707 1.5000 1.79526 45.25 28) 135.3380 D28 29) ∞ 1.6000 1.51680 63.88 30) ∞ 1.0000 [Aspherical data] m K A4 A6 A8 A10 11) 1.0000 -1.618E-06 1.005E-10 -9.102E-13 1.027E-15 27) 1.0000 1.794E-06 3.511E-10 -4.194E-12 4.714E-15 [Each group focal length data] Group First plane Focal length G1 1 87.05 G2 13 -75.58 G3 15 188.31 G4 22 131.00 G5 24 -81.36 [Variable distance data] When focusing at infinity When focusing at close range D12 1.500 14.150 D14 20.677 8.026 D21 11.687 2.799 D23 4.359 13.247 D28 12.949 12.967.

[0152] FIG. 6 is a diagram showing various aberrations of the optical system of the third embodiment.

[0153] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0154] Fourth Embodiment FIG. 7 is a cross-sectional view of an optical system of a fourth embodiment when focusing on an object at infinity.

[0155] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.

[0156] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus positive lens L3 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a biconvex positive lens L6.

[0157] The second lens group G2 is made up of a negative meniscus lens L7 with its convex surface facing the object side.

[0158] The third lens group G3 is composed of, in order from the object side, a biconvex positive lens L8, a biconcave negative lens L9, a biconcave negative lens L10, and a biconvex positive lens L11.

[0159] The fourth lens group G4 is made up of a biconvex positive lens L12.

[0160] The fifth lens group G5 is made up of a biconcave negative lens L13.

[0161] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0162] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0163] The optical system of this embodiment focuses by moving the second lens group G2 and the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the object side to the image plane side, and the fourth lens group G4 is moved from the image plane side to the object side.

[0164] In the optical system of this embodiment, the first lens group G1 corresponds to the front group, and the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group. The second lens group G2 and the fourth lens group G4 correspond to focusing groups that move during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The fifth lens group corresponds to the lens group Gi located closest to the image.

[0165] In the optical system of this embodiment, the positive lens L11 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L13 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L12 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side. The positive lens L1 corresponds to the positive lens Pf in the front group, and the negative lens L5 corresponds to the negative lens Nf in the front group.

[0166] Table 4 below lists the specifications of the optical system of this example.

[0167] (Table 4) [Overall specifications] f 132.50 ff 89.44 fr -275.65 TL 145.93 Bf 27.06 FNO 1.84 Y 21.70 [Lens specifications] m r d nd νd 1) 66.3183 9.7104 1.66382 27.35 2) 165.2220 0.1000 3) 100.0420 7.5397 1.43700 95.00 4) 483.6760 0.1000 5) 69.7432 5.3124 1.48749 70.24 6) 105.3980 0.7647 7) 51.1334 10.4840 1.55032 75.49 8) -1410.8700 1.4999 1.85478 24.80 9) 43.2806 4.4516 *10) 96.9716 4.5988 1.49782 82.56 11) -620.9090 1.1187 12) ∞ D12 (Aperture stop) 13) 758.4980 1.4999 1.59319 67.87 14) 43.6263 D14 15) 69.5215 6.9627 1.83400 37.18 16) -117.7280 0.4462 17) -249.8720 1.4000 1.71736 29.57 18) 53.3330 6.6458 19) -124.6990 1.5000 1.66446 35.86 20) 89.4859 3.6246 21) 78.8983 8.0487 1.85026 32.35 22) -100.9890 D22 23) 132.3330 4.1642 1.90200 25.26 24) -628.5160 D24 25) -80.5301 1.5000 1.85026 32.35 26) 378.0000 25.0012 27) ∞ 1.6000 1.51680 63.80 28) ∞ 1.0013 [Aspherical data] m K A4 A6 A8 A10 10) 1.0000 -1.352E-06 -3.019E-10 -2.040E-14 0.000E+00 [Focal length data for each group] Group Initial surface Focal length G1 1 89.44 G2 13 -78.09 G3 15 101.43 G4 23 121.51 G5 25 -77.96 [Variable distance data] When focused at infinity When focused at close range D12 1.900 15.168 D14 23.030 9.761 D22 7.512 3.134 D24 4.409 8.787

[0168] FIG. 8 is a diagram showing various aberrations of the optical system of the fourth embodiment.

[0169] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0170] Fifth Embodiment FIG. 9 is a cross-sectional view of an optical system of a fifth embodiment when focusing on an object at infinity.

[0171] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power.

[0172] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus positive lens L3 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, an aperture stop S, and a meniscus positive lens L6 with a convex surface facing the object side.

[0173] The second lens group G2 is made up of a negative meniscus lens L7 with its convex surface facing the object side.

[0174] The third lens group G3 is composed of, in order from the object side, a biconcave negative lens L8, a meniscus positive lens L9 with its convex surface facing the object side, a biconvex positive lens L10, and a biconvex positive lens L11.

[0175] The fourth lens group G4 is made up of a biconcave negative lens L12.

[0176] The fifth lens group G5 is composed of, in order from the object side, a meniscus positive lens L13 with its convex surface facing the object side, a biconcave negative lens L14, and a biconcave negative lens L15.

[0177] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0178] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0179] In the optical system of this embodiment, focusing is performed by moving the second lens group G2 and the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 and the fourth lens group G4 are moved from the object side to the image plane side along different trajectories.

[0180] In the optical system of this embodiment, the positive lens L1 to the negative lens L5 of the first lens group G1 correspond to the front group, and the positive lens L6 of the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group. The second lens group G2 and the fourth lens group G4 correspond to focusing groups that move during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The fifth lens group corresponds to the lens group Gi located closest to the image.

[0181] In the optical system of this embodiment, the positive lens L10 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L15 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L14 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side. The positive lens L1 corresponds to the positive lens Pf in the front group, and the negative lens L5 corresponds to the negative lens Nf in the front group.

[0182] Table 5 below lists the specifications of the optical system of this example.

[0183] (Table 5) [Overall specifications] f 132.30 ff 127.35 fr -496.37 TL 147.53 Bf 13.91 FNO 1.85 Y 21.70 [Lens specifications] m r d nd νd 1) 72.0000 8.1143 1.66382 27.35 2) 161.8404 1.0002 3) 72.6315 8.1310 1.49782 82.57 4) 199.5442 1.6725 5) 94.0000 5.5489 1.49782 82.57 6) 202.8688 2.1185 7) 55.0000 9.7215 1.49782 82.57 8) -4288.4061 2.1000 1.85451 25.15 9) 48.0031 8.4369 10) ∞ 2.1000 (Aperture stop) *11) 68.5824 4.7000 1.51680 64.13 12) 441.6203 D12 13) 157.7474 2.1000 1.72916 54.61 14) 39.7106 D14 15) -202.1129 2.1000 1.85451 25.15 16) 112.5075 2.0137 17) 100.0000 3.5631 1.59319 67.90 18) 208.1606 2.3956 19) 100.0000 8.8106 1.76200 40.11 20) -79.7795 0.2910 21) 250.6999 4.1838 1.86074 23.08 22) -393.9542 D22 23) -1082.0011 2.1000 1.60738 56.74 24) 100.0000 D24 25) 59.1913 5.3939 1.86074 23.08 26) 207.0827 1.5307 27) -899.4731 2.1000 1.80400 46.60 28) 95.4791 3.9878 29) -123.4835 2.1000 1.86074 23.08 30) 594.5786 11.8530 31) ∞ 1.6000 1.51680 63.88 32) ∞ 1.0000 [Aspherical surface data] m K A4 A6 A8 A10 11) 1.0000 -1.726E-06 -4.489E-10 -1.063E-13 -9.041E-17 [Each group focal length data] Group starting surface focal length G1 1 87.22 G2 13 -73.33 G3 15 64.71 G4 23 -150.61 G5 25 -169.73 [Variable distance data] When focusing at infinity When focusing at close range D12 1.671 15.261 D14 21.508 7.918 D22 2.500 10.558 D24 1.058 3.000.

[0184] FIG. 10 is a diagram showing various aberrations of the optical system of the fifth embodiment.

[0185] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0186] Sixth Embodiment FIG. 11 is a cross-sectional view of an optical system of a sixth embodiment when focusing on an object at infinity.

[0187] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.

[0188] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus positive lens L3 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, an aperture stop S, and a biconvex positive lens L6.

[0189] The second lens group G2 is made up of a negative meniscus lens L7 with its convex surface facing the object side.

[0190] The third lens group G3 is composed of, in order from the object side, a cemented negative lens of a biconcave negative lens L8 and a meniscus positive lens L9 with its convex surface facing the object side, a biconvex positive lens L10, and a meniscus positive lens L11 with its concave surface facing the object side.

[0191] The fourth lens group G4 is composed of a plano-convex positive lens L12 with its flat surface facing the object side.

[0192] The fifth lens group G5 consists of, in order from the object side, a cemented positive lens consisting of a meniscus-shaped positive lens L13 with its concave surface facing the object side and a meniscus-shaped negative lens L14 with its concave surface facing the object side, and a plano-concave negative lens L15 with its concave surface facing the object side.

[0193] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0194] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0195] The optical system of this embodiment focuses by moving the second lens group G2 and the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the object side to the image plane side, and the fourth lens group G4 is moved from the image plane side to the object side.

[0196] In the optical system of this embodiment, the positive lens L1 to the negative lens L5 of the first lens group G1 correspond to the front group, and the positive lens L6 of the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group. The second lens group G2 and the fourth lens group G4 correspond to focusing groups that move during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The fifth lens group corresponds to the lens group Gi located closest to the image.

[0197] In the optical system of this embodiment, the positive lens L10 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L15 corresponds to the lens Li1 arranged closest to the image plane, and the negative lens L14 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side. The positive lens L1 corresponds to the positive lens Pf in the front group, and the negative lens L5 corresponds to the negative lens Nf in the front group.

[0198] Table 6 below lists the specifications of the optical system of this example.

[0199] (Table 6) [Overall specifications] f 122.20 ff 112.14 fr -177.50 TL 145.00 Bf 13.45 FNO 1.85 Y 21.70 [Lens specifications] m r d nd νd 1) 66.9113 7.1102 1.66382 27.35 2) 132.6147 3.5669 3) 137.4634 5.1224 1.49782 82.57 4) 540.1386 0.2000 5) 89.9080 6.7766 1.49782 82.57 6) 613.1016 0.2000 7) 57.3140 9.6789 1.49782 82.57 8) -307.5506 1.2000 1.85451 25.15 9) 63.0143 6.3078 10) ∞ 3.0000 (Aperture stop) *11) 122.2242 4.0000 1.51680 64.13 12) -458.5930 D12 13) 4486.7234 1.5000 1.59349 67.00 14) 44.8020 D14 15) -430.0623 1.5000 1.85451 25.15 16) 47.1972 2.9853 2.00100 29.12 17) 57.6854 1.0000 18) 63.0295 7.5095 2.00069 25.46 19) -194.4050 9.1686 20) -93.7633 6.3889 1.61800 63.34 *21) -43.5220 D21 22) ∞ 4.1055 1.72047 34.71 23) -206.0663 D23 24) -192.6542 6.9552 1.80518 25.45 25) -43.3466 1.4653 2.00069 25.46 26) -110.3893 3.2612 *27) -43.8980 1.2000 1.79526 45.25 28) ∞ 11.3953 29) ∞ 1.6000 1.51680 64.13 30) ∞ 1.0001 [Aspherical data] m K A4 A6 A8 A10 11) 1.0000 -1.521E-06 -1.713E-10 -2.725E-13 3.136E-16 21) 1.0000 2.328E-06 -8.987E-10 7.838E-13 -1.151E-16 27) 1.0000 7.505E-06 -5.432E-09 -6.999E-13 5.724E-15 [Focal length data for each group] Group Starting surface Focal length G1 1 81.65 G2 13 -76.26 G3 15 79.48 G4 22 286.02 G5 24 -55.59 [Variable interval data] When focusing at infinity When focusing at close distance D12 1.500 14.388 D14 20.384 7.496 D21 10.795 1.806 D23 4.123 13.113.

[0200] FIG. 12 is a diagram showing various aberrations of the optical system of the sixth embodiment.

[0201] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0202] Seventh Embodiment FIG. 13 is a cross-sectional view of an optical system of a seventh embodiment when focusing on an object at infinity.

[0203] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.

[0204] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus positive lens L3 with a convex surface facing the object side, a cemented negative lens consisting of a meniscus positive lens L4 with a convex surface facing the object side and a meniscus negative lens L5 with a convex surface facing the object side, an aperture stop S, and a biconvex positive lens L6.

[0205] The second lens group G2 is made up of a negative meniscus lens L7 with its convex surface facing the object side.

[0206] The third lens group G3 is composed of, in order from the object side, a cemented negative lens consisting of a meniscus negative lens L8 with its convex surface facing the object side and a meniscus positive lens L9 with its convex surface facing the object side, a biconvex positive lens L10, and a meniscus positive lens L11 with its concave surface facing the object side.

[0207] The fourth lens group G4 is made up of a positive meniscus lens L12 with its concave surface facing the object side.

[0208] The fifth lens group G5 is composed of, in order from the object side, a cemented negative lens consisting of a meniscus negative lens L13 with its convex surface facing the object side and a meniscus positive lens L14 with its convex surface facing the object side, and a biconcave negative lens L15.

[0209] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0210] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0211] The optical system of this embodiment focuses by moving the second lens group G2 and the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the object side to the image plane side, and the fourth lens group G4 is moved from the image plane side to the object side.

[0212] In the optical system of this embodiment, the positive lens L1 to the negative lens L5 of the first lens group G1 correspond to the front group, and the positive lens L6 of the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group. The second lens group G2 and the fourth lens group G4 correspond to focusing groups that move during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The fifth lens group corresponds to the lens group Gi located closest to the image.

[0213] In the optical system of this embodiment, the positive lens L10 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L15 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L14 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side. The positive lens L1 corresponds to the positive lens Pf in the front group, and the negative lens L5 corresponds to the negative lens Nf in the front group.

[0214] Table 7 below lists the specifications of the optical system of this example.

[0215] (Table 7) [Overall specifications] f 147.00 ff 129.17 fr -189.05 TL 157.00 Bf 15.74 FNO 1.85 Y 21.70 [Lens specifications] m r d nd νd 1) 74.1751 10.1607 1.66382 27.35 2) 191.7895 0.2000 3) 93.9587 6.9178 1.49782 82.57 4) 200.7834 0.2000 5) 74.0198 7.9191 1.49782 82.57 6) 179.5298 0.2000 7) 55.0947 11.1364 1.49782 82.57 8) 3267.0580 1.2000 1.85451 25.15 9) 47.1440 9.1892 10) ∞ 3.0000 (Aperture stop) *11) 106.1518 4.9153 1.51680 64.13 12) -333.2392 D12 13) 447.5810 1.5000 1.59349 67.00 14) 40.6656 D14 15) 68.0477 1.5000 1.90366 31.27 16) 31.3982 7.3704 1.59319 67.90 17) 70.6986 14.9835 18) 230.0945 9.0000 1.90366 31.27 19) -63.8675 0.2000 20) -125.7886 3.5000 1.51680 64.13 *21) -83.8591 D21 22) -283.7511 3.5722 1.69895 30.13 23) -110.1588 D23 24) 522.5170 1.2000 1.88300 40.69 25) 36.0701 6.0890 1.68893 31.16 26) 121.3136 4.4693 *27) -217.7830 1.5000 1.85108 40.12 28) 91.8799 13.6807 29) ∞ 1.6000 1.51680 64.13 30) ∞ 1.0000 [Aspheric data] m K A4 A6 A8 A10 11) 1.0000 -1.573E-06 -1.204E-10 -1.440E-13 2.081E-16 21) 1.0000 4.670E-06 -4.131E-09 3.245E-12 -2.590E-15 27) 1.0000 7.294E-06 -1.088E-08 1.539E-11 -1.356E-14 [Each group focal length data] Group starting plane focal length G1 1 88.53 G2 13 -75.47 G3 15 61.62 G4 22 255.46 G5 24 -42.70 [Variable interval data] When focusing at infinity When focusing at close distance D12 1.500 15.236 D14 21.671 7.935 D21 5.840 1.300 D23 1.786 6.327.

[0216] FIG. 14 is a diagram showing various aberrations of the optical system of the seventh embodiment.

[0217] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0218] Eighth Example FIG. 15 is a cross-sectional view of an optical system of an eighth example when focusing on an object at infinity.

[0219] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.

[0220] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with a convex surface facing the object side, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus positive lens L3 with a convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, an aperture stop S, and a meniscus positive lens L6 with a convex surface facing the object side.

[0221] The second lens group G2 is made up of a negative meniscus lens L7 with its convex surface facing the object side.

[0222] The third lens group G3 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus negative lens L8 with its concave surface facing the object side and a meniscus positive lens L9 with its concave surface facing the object side, a biconvex positive lens L10, and a biconcave negative lens L11.

[0223] The fourth lens group G4 is composed of a positive lens L12 having a plano-convex shape with its convex surface facing the object side.

[0224] The fifth lens group G5 consists of, in order from the object side, a cemented negative lens consisting of a plano-concave negative lens L13 with its concave surface facing the object side and a plano-convex positive lens L14 with its flat surface facing the object side, and a biconcave negative lens L15.

[0225] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0226] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0227] The optical system of this embodiment focuses by moving the second lens group G2 and the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the object side to the image plane side, and the fourth lens group G4 is moved from the image plane side to the object side.

[0228] In the optical system of this embodiment, the positive lens L1 to the negative lens L5 of the first lens group G1 correspond to the front group, and the positive lens L6 of the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 correspond to the rear group. The second lens group G2 and the fourth lens group G4 correspond to focusing groups that move during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The fifth lens group corresponds to the lens group Gi located closest to the image.

[0229] In the optical system of this embodiment, the positive lens L10 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L15 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L14 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side. The positive lens L1 corresponds to the positive lens Pf in the front group, and the negative lens L5 corresponds to the negative lens Nf in the front group.

[0230] Table 8 below lists the specifications of the optical system of this example.

[0231] (Table 8) [Overall specifications] f 176.40 ff 134.07 fr -141.88 TL 185.00 Bf 15.26 FNO 1.85 Y 21.70 [Lens specifications] m r d nd νd 1) 70.7992 10.3651 1.66382 27.35 2) 98.0167 4.1343 3) 113.3096 11.6028 1.43700 95.10 4) 600.8306 17.8278 5) 53.5822 10.2222 1.43700 95.10 6) 102.9859 0.2000 7) 65.9776 12.1046 1.49782 82.57 8) -209.2139 2.0000 1.85451 25.15 9) 77.6880 6.5433 10) ∞ 3.0000 (Aperture stop) *11) 68.8730 6.2390 1.51680 64.13 12) 742.5790 D12 13) 135.0045 1.5000 1.87071 40.73 14) 35.9895 D14 15) -82.8618 1.5000 2.00069 25.46 16) -232.4416 7.3438 1.51680 64.13 17) -48.2540 0.2000 18) 113.4417 9.0000 1.85451 25.15 19) -79.8447 1.3545 20) -63.0212 1.5000 1.59319 67.90 *21) 310.8985 D21 22) 110.8901 4.5000 1.80518 25.45 23) ∞ D23 24) -192.4796 1.5000 2.00069 25.46 25) ∞ 4.4712 1.60342 38.03 26) -198.8206 4.9478 *27) -135.4173 1.5000 1.85108 40.12 28) 116.3479 13.2022 29) ∞ 1.6000 1.51680 64.13 30) ∞ 1.0000 [Aspheric data] m K A4 A6 A8 A10 11) 1.0000 -1.987E-06 -3.988E-10 -1.732E-13 2.337E-16 21) 1.0000 -1.638E-06 -1.437E-09 -3.911E-13 3.952E-16 27) 1.0000 1.966E-07 -5.586E-09 7.011E-12 -7.933E-15 [Each group focal length data] Group starting plane focal length G1 1 93.04 G2 13 -56.76 G3 15 110.95 G4 22 137.72 G5 24 -61.92 [Variable interval data] When focusing at infinity When focusing at close distance D12 1.500 12.763 D14 33.230 21.967 D21 7.604 2.497 D23 3.307 8.415.

[0232] FIG. 16 is a diagram showing various aberrations of the optical system of the eighth embodiment.

[0233] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0234] Ninth Example FIG. 17 is a cross-sectional view of an optical system of a ninth example when focusing on an object at infinity.

[0235] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power.

[0236] The first lens group G1 comprises, in order from the object side, a biconvex positive lens L1, a cemented negative lens consisting of a biconvex positive lens L2 and a biconcave negative lens L3, and a biconvex positive lens L4.

[0237] The second lens group G2 is made up of a cemented negative lens consisting of a biconvex positive lens L5 and a biconcave negative lens L6.

[0238] The third lens group G3 consists of, in order from the object side, a biconvex positive lens L7, a cemented negative lens consisting of a biconcave negative lens L8 and a biconvex positive lens L9, a cemented negative lens consisting of a plano-convex negative lens L10 with its flat surface facing the object side and 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, and a meniscus negative lens L13 with its concave surface facing the object side.

[0239] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0240] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0241] In the optical system of this embodiment, focusing is performed by moving the second lens group G2 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the object side to the image plane side.

[0242] In the optical system of this embodiment, the first lens group G1 corresponds to the front group, and the second lens group G2 and the third lens group G3 correspond to the rear group. The second lens group G2 corresponds to the focusing group that moves during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The third lens group corresponds to the lens group Gi located closest to the image.

[0243] In the optical system of this embodiment, the positive lens L7 corresponds to the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group, and to the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo. The negative lens L13 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L12 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side.

[0244] Table 9 below lists the specifications of the optical system of this example.

[0245] (Table 9) [Overall specifications] f 85.60 ff 78.29 fr -407.18 TL 124.99 Bf 12.15 FNO 1.85 Y 21.70 [Lens specifications] m r d nd νd 1) 103.0990 7.3719 1.88300 40.76 2) -644.1714 0.1000 3) 57.9469 9.9769 1.49782 82.57 4) -128.1989 1.4547 2.00330 28.27 5) 151.9669 7.1394 6) 645.1565 10.0790 1.72916 54.67 7) -201.8099 1.4626 8) ∞ D8 (Aperture stop) 9) 375.9531 4.9280 1.66382 27.35 10) -47.1085 1.2000 1.71700 47.93 11) 42.5578 D11 12) 76.0025 8.7829 1.76385 48.49 13) -56.0181 0.1000 14) -61.6864 1.2000 1.69895 30.13 15) 40.7957 9.2671 1.81600 46.62 16) -118.5713 1.4000 17) ∞ 1.2000 1.63980 34.47 18) 28.7079 4.2638 1.80810 22.76 19) 39.6858 3.5350 20) 55.4388 6.2285 1.88300 40.76 21) 213.8631 12.1281 22) -36.6968 1.2000 1.60342 38.03 23) -124.2980 10.0960 24) ∞ 1.6000 1.51680 63.88 25) ∞ 1.0000 [Focal length data for each group] Group Initial Focal length G1 1 78.29 G2 9 -62.08 G3 12 70.49 [Variable interval data] When focusing at infinity When focusing at short distance D8 1.200 10.964 D11 18.074 8.310.

[0246] FIG. 18 is a diagram showing various aberrations of the optical system of the ninth embodiment.

[0247] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0248] Tenth Example FIG. 19 is a cross-sectional view of an optical system of a tenth example when focusing on an object at infinity.

[0249] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and a third lens group G3 having negative refractive power.

[0250] The first lens group G1 consists of, in order from the object side, a meniscus positive lens L1 with its convex surface facing the object side, a cemented negative lens consisting of a biconvex positive lens L2 and a biconcave negative lens L3, and a cemented negative lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5.

[0251] The second lens group G2 consists of, in order from the object side, a biconcave negative lens L6, a biconvex positive lens L7, a meniscus negative lens L8 with its convex surface facing the object side, and a cemented positive lens consisting of a biconcave negative lens L9 and a biconvex positive lens L10.

[0252] The third lens group G3 is composed of, in order from the object side, a positive meniscus lens L11 with its concave surface facing the object side, and a negative meniscus lens L12 with its concave surface facing the object side.

[0253] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0254] Between the optical system of this embodiment and the image plane I, a filter FL is disposed.

[0255] In the optical system of this embodiment, focusing is performed by moving the second lens group G2 along the optical axis. When focusing on a close object from a state focused on infinity, the second lens group G2 is moved from the image plane side to the object side.

[0256] In the optical system of this embodiment, the first lens group G1 corresponds to the front group, and the second lens group G2 and the third lens group G3 correspond to the rear group. The second lens group G2 corresponds to the focusing group that moves during focusing. The second lens group G2 corresponds to the focusing group Gfo located closest to the object. The third lens group corresponds to the lens group Gi located closest to the image.

[0257] In the optical system of this embodiment, the positive lens L7 corresponds to the single lens Pr having the strongest refractive power among the biconvex single lenses in the rear group, the negative lens L12 corresponds to the lens Li1 arranged closest to the image plane, and the positive lens L11 corresponds to the lens Li2 arranged adjacent to the lens Li1 on the object side.

[0258] Table 10 below lists the specifications of the optical system of this example.

[0259] (Table 10) [Overall specifications] f 100.00 ff 136.41 TL 120.00 Bf 13.15 FNO 1.85 Y 21.70 [Lens specifications] m r d nd νd 1) 57.7694 10.0024 1.59282 68.62 2) 400.0000 7.3758 3) 41.5755 11.6144 1.49782 82.57 4) -164.2951 1.2000 1.73800 32.33 5) 48.8315 2.2015 6) 69.3936 8.4881 1.80810 22.76 7) -54.7343 1.2000 1.74077 27.79 8) 49.8276 4.9417 9) ∞ 14.8014 (Aperture) 10) -124.6523 1.2000 1.73800 32.33 11) 111.4500 0.1000 12) 35.2246 10.0000 1.90366 31.34 13) -335.2341 0.9386 *14) 57.8259 1.2000 2.00178 19.32 15) 35.2792 7.8204 16) -55.7086 1.2964 1.68893 31.07 17) 78.8211 7.7550 1.88300 40.76 18) -51.1472 5.5324 19) -43.8291 6.4320 1.98613 16.48 20) -39.3902 1.0000 *21) -33.3333 1.2000 1.58913 61.25 22) -114.3133 11.1000 23) ∞ 1.6000 1.51680 63.88 24) ∞ 1.0000 [Aspheric data] m K A4 A6 A8 A10 14) 1.0000 -7.051E-06 -4.487E-09 -9.846E-12 1.986E-14 21) 1.0000 8.649E-07 3.345E-09 1.111E-12 -7.577E-15 [Focal length data for each group] Group Initial surface Focal length G1 1 136.41 G2 10 79.30 G3 19 -111.58 [Variable distance data] When focused at infinity When focused at close range D9 14.801 2.270 D18 5.532 18.064

[0260] FIG. 20 is a diagram showing various aberrations of the optical system of the tenth embodiment.

[0261] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0262] According to the above-described embodiments, an optical system that is small in size and has good optical performance can be realized.

[0263] The values ​​corresponding to the conditional expressions in each example are shown below.

[0264] TL is the total length of the optical system, f is the focal length of the optical system, Bf is the back focus in air equivalent length, ff is the focal length of the front group, fr is the focal length of the rear group, fPr is the focal length of the single lens Pr, fPfo1 is the focal length of the single lens Pfoi, and ffo is the focal length of the focusing group Gfo.

[0265] tr is the sum of the center thicknesses of the lenses included in the rear group, and tGi is the sum of the lengths on the optical axis of the lenses included in lens group Gi. Da is the distance on the optical axis between the object-side lens surface of lens Li1 and the image-plane-side lens surface of lens Li2 when focusing at infinity. D1 is the distance on the optical axis between the lens surface closest to the object and the object-side surface of single lens Pr when focusing at infinity, and D2 is the distance on the optical axis between the aperture stop and the object-side lens surface of single lens Pr.

[0266] ndPf is the refractive index of the positive lens Pf for the d-line, νdPf is the Abbe number of the positive lens Pf based on the d-line, θFPf is the partial dispersion ratio of the positive lens Pf, ndNf is the refractive index of the negative lens Nf for the d-line, νdNf is the Abbe number of the negative lens Nf based on the d-line, and θFNf is the partial dispersion ratio of the negative lens Nf.

[0267] [Conditional Expression Corresponding Values] Conditional Expression 1st 2nd 3rd 4th 5th (1) ff / |fr| 0.499 0.850 0.571 0.324 0.257 (2) tr / TL 0.283 0.220 0.239 0.172 0.252 (3) f / TL 0.897 0.912 0.912 0.908 0.897 (4) fPr / |fr| 0.221 0.582 0.284 0.193 0.120 (5) fPfoi / |fr| 0.221 0.582 0.284 0.193 0.120 (6) fPfoi / f 0.379 0.440 0.422 0.401 0.450 ( 7) Da / Bf 0.310 0.347 0.347 0.163 0.287 ( 8) tGi / Da 2.210 2.043 1.961 0.340 2.406 ( 9) D1 / TL 0.605 0.576 0.571 0.635 0.603 (10) D2 / TL 0.292 0.228 0.262 0.322 0.286 (11) |ffo| / f 0.523 0.509 0.571 0.589 0.554 (12) ndPf 1.664 1.664 1.664 1.664 1.664 (13) νdPf 27.350 27.350 27.350 27.350 27.350 (14) θFPf-(0.6415-0.00162*νdPf) 0.035 0.035 0.035 0.035 0.035 (15) ndNf 1.855 1.855 1.855 1.855 1.855 (16) νdNf 25.150 25.150 25.150 24.800 25.150 (17) θFNf-(0.6415-0.00162*νdNf) 0.010 0.010 0.010 0.011 0.010 .

[0268] Conditional 6th 7th 8th 9th 10th (1) ff / |fr| 0.632 0.683 0.945 0.192 0.688 (2) tr / TL 0.260 0.256 0.211 0.306 0.242 (3) f / TL 0.843 0.936 0.954 0.685 0.833 (4) fPr / |fr| 0.272 0.297 0.395 0.107 0.180 (5) fPfoi / |fr| 0.272 0.297 0.395 0.107 0.180 (6) fPfoi / f 0.395 0.382 0.318 0.508 0.357 (7) Da / Bf 0.242 0.284 0.324 0.998 0.076 (8) tGi / Da 2.950 1.967 1.510 2.650 7.632 (9) D1 / TL 0.524 0.660 0.700 0.504 0.526 (10) D2 / TL 0.247 0.359 0.295 0.203 0.134 (11) |ffo| / f 0.624 0.513 0.322 0.725 0.793 (12) ndPf 1.664 1.664 1.664 - 1.808 (13) νdPf 27.350 27.350 27.350 - 22.760 (14) θFPf-(0.6415-0.00162*νdPf) 0.035 0.035 0.035 - 0.026 (15) ndNf 1.855 1.855 1.855 - - (16) νdNf 25.150 25.150 25.150 - - (17) θFNf-(0.6415-0.00162*νdNf) 0.010 0.010 0.010 - -.

[0269] The above examples are merely illustrative of the present invention, and the present invention is not limited thereto. The following content can be appropriately adopted within the scope that does not impair the optical performance of the optical system of the embodiment of the present application.

[0270] The optical system of this embodiment does not need to have an optical member such as a filter between the lens surface closest to the image plane and the image plane.

[0271] The optical system of this embodiment may have an anti-vibration lens group that corrects image blur caused by camera shake by being moved so as to have a component in a direction perpendicular to the optical axis. The anti-vibration lens group may be a lens group, or a partial lens group consisting of one or more lens components included in the lens group. The "lens component" refers to a single lens or a cemented lens formed by cementing two or more single lenses together.

[0272] In the optical system of this embodiment, the lens surface may be spherical or flat, or may be aspherical. A spherical or flat lens surface is preferred because it facilitates lens processing and assembly adjustment, and prevents degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, a spherical or flat lens surface is preferred because it minimizes degradation of imaging performance when the image plane is misaligned.

[0273] In the case where the lens surface is aspherical, the aspherical surface may be formed by grinding glass or by glass molding using a mold having an aspherical shape, or may be formed on the surface of a resin bonded to the surface of the glass. In addition, in the optical system of this embodiment, the lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0274] Next, a camera equipped with the optical system of this embodiment will be described with reference to Fig. 21. Fig. 21 is a schematic diagram of a camera equipped with the optical system of this embodiment.

[0275] The camera 1 is an example of an optical device, and is a so-called mirrorless camera with interchangeable lenses, which has an interchangeable lens equipped with the optical system according to the first embodiment as the photographic lens 2.

[0276] In camera 1, light from an object (subject) (not shown) is collected by photographic lens 2 and reaches image sensor 3. Image sensor 3 converts the light from the subject into image data. The image data is displayed on electronic viewfinder 4. This allows a photographer with their eye positioned at eyepoint EP to observe the subject.

[0277] When the photographer presses a release button (not shown), the image data is stored in a memory (not shown). In this way, the photographer can photograph a subject using the camera 1.

[0278] Here, the optical system of the first embodiment mounted on the camera 1 as the photographic lens 2 is a small-sized optical system with good optical performance. Therefore, the camera 1 can be made small and have good optical performance. Note that even if a camera is constructed with the optical system of the second to tenth embodiments mounted on the photographic lens 2, the same effects as those of the camera 1 can be achieved.

[0279] Finally, a method for manufacturing the optical system of this embodiment will be outlined with reference to FIG.

[0280] 22 is a flowchart showing an outline of the method for manufacturing the optical system of this embodiment. The method for manufacturing the optical system of this embodiment shown in FIG. 22 includes the following steps S11 and S12.

[0281] Step S11: Prepare the front group, aperture stop S, and rear group.

[0282] Step S12: The optical system is made to satisfy the following conditions: (1) 0.10<ff / |fr|<1.50 (2) 0.13<tr / TL<0.45 (3) 0.50<f / TL<1.20 where, ff: focal length of the front group, fr: focal length of the rear group, tr: sum of the center thicknesses of the lenses included in the rear group, TL: total length of the optical system, f: focal length of the optical system.

[0283] According to the method for manufacturing an optical system of this embodiment, it is possible to manufacture an optical system that is small in size and has good imaging performance.

[0284] It should be understood that those skilled in the art can make various changes, substitutions, and alterations thereto without departing from the spirit and scope of the present disclosure.

[0285] S: aperture stop I: image plane 1: camera 2: photographing lens 3: image sensor

Claims

1. The lens has, in order from the object side, a front group having positive refractive power, an aperture stop, and a rear group, An optical system that satisfies both of the following conditions: 0.10 < ff / |fr| < 1.50 0.13 < tr / TL < 0.45 0.50 < f / TL < 1.20 however, ff: focal length of the front group fr: focal length of the rear group tr: the sum of the center thicknesses of the lenses included in the rear group TL: total length of the optical system f: focal length of the optical system

2. 2. The optical system according to claim 1, wherein the rear group has negative refractive power.

3. 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.05 < fPr / | fr | < 0.70 however, fPr: focal length of the single lens Pr having the strongest refractive power among the biconvex single lenses in the rear group

4. at least one focusing group that moves during focusing; 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.05 < fPfoi / |fr| < 0.70 however, fPfoi: the focal length of the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo arranged closest to the object among the at least one focusing group

5. at least one focusing group that moves during focusing; 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.25 < fPfoi / f <0.55 however, fPfoi: the focal length of the single lens Pfoi with the strongest refractive power among the biconvex single lenses arranged closer to the image plane than the focusing group Gfo arranged closest to the object among the at least one focusing group

6. 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.05 < Da / Bf < 1.10 however, Da: The distance on the optical axis between the object-side lens surface of the lens Li1 located closest to the image plane and the image-side lens surface of the lens Li2 located adjacent to the object side of the lens Li1 when focusing at infinity. Bf: Back focus in air equivalent length

7. the rear group has a plurality of lens groups including at least one focusing group that moves during focusing; The distances between the plurality of lens groups change during focusing, 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.30 < tGi / Da < 9.00 however, tGi: the sum of the lengths on the optical axis of the lenses included in the lens group Gi that is located closest to the image among the plurality of lens groups Da: The distance on the optical axis between the object-side lens surface of the lens Li1 located closest to the image plane and the image-side lens surface of the lens Li2 located adjacent to the object side of the lens Li1 when focusing at infinity.

8. 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.40 < D1 / TL < 0.85 however, D1: The distance on the optical axis between the lens surface closest to the object and the object-side surface of the single lens Pr with the strongest refractive power among the biconvex single lenses in the rear group when focusing at infinity.

9. 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.10 < D2 / TL < 0.80 however, D2: The distance on the optical axis between the aperture stop and the object-side lens surface of the single lens Pr having the strongest refractive power among the biconvex single lenses in the rear group.

10. at least one focusing group that moves during focusing; 3. The optical system according to claim 1, wherein the following condition is satisfied: 0.25 < |ffo| / f < 0.90 however, ffo: focal length of the focusing group Gfo arranged closest to the object side among the at least one focusing group

11. 3. The optical system according to claim 1, wherein the front group has at least one positive lens Pf that satisfies both of the following conditions: 1.60 < ndPf νdPf < 31.00 0.01 < θgFPf-(0.6415-0.00162×νdPf) however, ndPf: refractive index of the positive lens Pf with respect to the d line νdPf: Abbe number of the positive lens Pf based on the d line θgFPf: partial dispersion ratio of the positive lens Pf, which is defined by the following equation when the refractive index of the positive lens Pf for the g-line is ngPf, the refractive index of the positive lens Pf for the F-line is nFPf, and the refractive index of the positive lens Pf for the C-line is nCPf. θgFPf = (ngPf-nFPf) / (nFPf-nCPf)

12. 3. The optical system according to claim 1, wherein the front group has at least one negative lens Nf that satisfies both of the following conditions: Nf=1 / Nf / Nf / Nf (2 / Nf / Nf) ...). 1.85 < ndNf νdNf < 26.00 θgFNf-(0.6415-0.00162×νdNf) < 0.015 however, ndNf: refractive index of the negative lens Nf with respect to the d line νdNf: Abbe number of the negative lens Nf based on the d line θgFNf: partial dispersion ratio of the negative lens Nf, which is defined by the following equation when the refractive index of the negative lens Nf for the g-line is ngNf, the refractive index of the negative lens Nf for the F-line is nFNf, and the refractive index of the negative lens Nf for the C-line is nCNf. θgFNf = (ngNf-nFNf) / (nFNf-nCNf)

13. An optical instrument comprising the optical system according to claim 1 or 2.

14. An interchangeable lens comprising the optical system according to claim 1 or 2.