Variable magnification optical system, optical device, and method for manufacturing variable magnification optical system

Abstract

SOLUTION: A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a rear lens group having a positive refractive power, wherein upon zooming from a wide angle end state to a telephoto end state, a distance between the first lens group and the second lens group changes, and a distance between the second lens group and the third lens group changes, A distance between the third lens group and the rear lens group changes, the rear lens group includes a focusing lens group that moves during focusing from an object at infinity to an object at a close distance, and a predetermined conditional expression is satisfied.EFFECT: It is possible to correct various aberrations favorably.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a variable magnification optical system, an optical device, and a method for manufacturing a variable magnification optical system. [Background technology]

[0002] Variable magnification optical systems have been proposed in the past that are compact yet compatible with large image sensors and enable high-speed focusing suitable for video shooting. See, for example, Japanese Patent Application Laid-Open No. 2015-064492. However, conventional variable magnification optical systems have not been able to adequately correct various aberrations. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-064492 Summary of the Invention

[0004] The present invention provides The lens has, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a subsequent lens group having positive refractive power; During magnification change, the distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, and the distance between the third lens group and the subsequent lens group changes, the subsequent lens group includes a focusing lens group that moves during focusing; The variable magnification optical system satisfies the following conditional expressions: 2.00 < f1 / fw < 8.000 0.100 <BFw / fw < 1.00 however, f1: focal length of the first lens group fw: focal length of the variable magnification optical system in the wide-angle end state BFw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state

[0005] The present invention also provides A method for manufacturing a variable magnification optical system having, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a subsequent lens group having positive refractive power, the method comprising: During zooming, the distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, and the distance between the third lens group and the subsequent lens group changes; The subsequent lens group is configured to have a focusing lens group that moves during focusing, The present invention relates to a manufacturing method for a variable magnification optical system that is configured to satisfy the following conditional expressions: 2.00 < f1 / fw < 8.000 0.100 <BFw / fw < 1.00 however, f1: focal length of the first lens group fw: focal length of the variable magnification optical system in the wide-angle end state BFw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state [Brief explanation of the drawings]

[0006] [Figure 1] 1A, 1B, and 1C are cross-sectional views of a variable magnification optical system according to Example 1 in a wide-angle end state, an intermediate focal length state, and a telephoto end state, respectively. [Figure 2] 2A, 2B, and 2C are diagrams showing various aberrations when the variable magnification optical system according to Example 1 is focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 3] 3A, 3B, and 3C are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 4]4A, 4B, and 4C are cross-sectional views of the variable magnification optical system according to Example 2 in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 5] 5A, 5B, and 5C are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 6] 6A, 6B, and 6C are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 7] 7A, 7B, and 7C are cross-sectional views of the variable magnification optical system according to Example 3 in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 8] 8A, 8B, and 8C are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 9] 9A, 9B, and 9C are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 10] 10A, 10B, and 10C are cross-sectional views of the variable magnification optical system according to Example 4 in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 11] 11A, 11B, and 11C are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 12] 12A, 12B, and 12C are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 13] 13A, 13B, and 13C are cross-sectional views of a variable magnification optical system according to Example 5 in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 14] 14A, 14B, and 14C are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 15] 15A, 15B, and 15C are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 16] 16A, 16B, and 16C are cross-sectional views of a variable magnification optical system according to Example 6 in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 17] 17A, 17B, and 17C are diagrams showing various aberrations of the variable magnification optical system according to Example 6 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 18] 18A, 18B, and 18C are diagrams showing various aberrations of the variable magnification optical system according to Example 6 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 19] 19A, 19B, and 19C are cross-sectional views of the variable magnification optical system according to Example 7 in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 20] 20A, 20B, and 20C are diagrams showing various aberrations of the variable magnification optical system according to Example 7 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 21] 21A, 21B, and 21C are diagrams showing various aberrations of the variable magnification optical system according to Example 7 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 22] 22A, 22B, and 22C are cross-sectional views of a variable magnification optical system according to Example 8 in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 23]23A, 23B, and 23C are diagrams showing various aberrations of the variable magnification optical system according to Example 8 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 24] 24A, 24B, and 24C are diagrams showing various aberrations of the variable magnification optical system according to Example 8 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. [Figure 25] FIG. 25 is a diagram showing the configuration of a camera equipped with a variable magnification optical system. [Figure 26] FIG. 26 is a flow chart showing an outline of a method for manufacturing a variable magnification optical system. DETAILED DESCRIPTION OF THE INVENTION

[0007] The variable magnification optical system, optical device, and method for manufacturing the variable magnification optical system according to this embodiment will be described below. First, the variable magnification optical system according to this embodiment will be described.

[0008] The variable magnification optical system of this embodiment has, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a subsequent lens group having positive refractive power, and when changing magnification from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, and the distance between the third lens group and the subsequent lens group changes, and the subsequent lens group has a focusing lens group that moves when focusing from an object at infinity to an object at a close distance, and is configured to satisfy the following conditional expressions (1) and (2). (1) 2.00 < f1 / fw < 8.000 (2) 0.100 <BFw / fw < 1.00 however, f1: focal length of the first lens group fw: focal length of the variable magnification optical system in the wide-angle end state BFw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state

[0009] The subsequent lens group of the variable magnification optical system of this embodiment has at least two lens groups. Note that in this embodiment, a lens group refers to a portion having at least one lens separated by an air gap. Also, in this embodiment, a lens component refers to a single lens or a cemented lens formed by cementing two or more lenses together. The variable magnification optical system of this embodiment can achieve good aberration correction during magnification change by changing the spacing between each lens group when changing magnification from the wide-angle end state to the telephoto end state. In addition, by locating the focusing lens group as the subsequent lens group, the focusing lens group can be made smaller and lighter, resulting in high-speed focusing and allowing for the size of the variable magnification optical system and the lens barrel to be reduced.

[0010] Conditional expression (1) defines the ratio between the focal length of the first lens group and the focal length of the variable magnification optical system in the wide-angle end state. By satisfying conditional expression (1), the variable magnification optical system of this embodiment can effectively correct various aberrations, including coma in the wide-angle end state.

[0011] If the value corresponding to conditional expression (1) of the variable magnification optical system of this embodiment exceeds the upper limit, the refractive power of the first lens group becomes weak, making it difficult to effectively correct various aberrations in the wide-angle end state. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (1) to 7.000. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (1) to 6.500, or even 6.000.

[0012] On the other hand, if the value corresponding to conditional expression (1) of the variable magnification optical system of this embodiment falls below the lower limit, the refractive power of the first lens group becomes large, making it difficult to effectively correct various aberrations, particularly coma, in the wide-angle end state. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (1) to 3.00. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (1) to 4.00, or even 4.50.

[0013] Conditional expression (2) defines the ratio between the back focus of the variable magnification optical system in the wide-angle end state and the focal length of the variable magnification optical system in the wide-angle end state. By satisfying conditional expression (2), the variable magnification optical system of this embodiment can effectively correct various aberrations, including coma in the wide-angle end state. Note that the back focus is the distance on the optical axis from the lens surface closest to the image to the image plane.

[0014] If the value corresponding to conditional expression (2) of the variable magnification optical system of this embodiment exceeds the upper limit, the back focus of the variable magnification optical system in the wide-angle end state becomes large relative to the focal length of the variable magnification optical system in the wide-angle end state, making it difficult to satisfactorily correct various aberrations in the wide-angle end state. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.91. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.85, or even 0.80.

[0015] On the other hand, if the corresponding value of conditional expression (2) of the variable magnification optical system of this embodiment falls below the lower limit, the back focus of the variable magnification optical system in the wide-angle end state becomes small relative to the focal length of the variable magnification optical system in the wide-angle end state, making it difficult to satisfactorily correct various aberrations, particularly coma aberration, in the wide-angle end state. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (2) to 0.300. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (2) to 0.400, or even 0.500.

[0016] In conditional expression (2), the "back focus of the variable magnification optical system in the wide-angle end state" indicated by BFw may be changed to the "back focus of the variable magnification optical system in the shortest overall length state," and the "focal length of the variable magnification optical system in the wide-angle end state" indicated by fw may be changed to the "focal length of the variable magnification optical system in the shortest overall length state." In other words, conditional expression (2) may be expressed as follows: (2) 0.100 <BFs / fs < 1.00 however, BFs: back focus of the variable magnification optical system when the total length is shortest fs: focal length of the variable magnification optical system when the total length is shortest

[0017] With the above configuration, the variable magnification optical system of this embodiment is compact yet compatible with large image sensors, and can effectively correct various aberrations during magnification and focusing.

[0018] Furthermore, it is desirable that the variable magnification optical system of this embodiment satisfy the following conditional expression (3). (3) 0.040 < βFw < 0.800 however, βFw: lateral magnification of the focusing lens group in the wide-angle end state

[0019] Conditional expression (3) defines the lateral magnification of the focusing lens group in the wide-angle end state. By satisfying conditional expression (3), the variable magnification optical system of this embodiment can reduce the amount of movement of the focusing lens group during focusing, thereby enabling the variable magnification optical system to be made more compact.

[0020] If the value corresponding to conditional expression (3) of the variable magnification optical system of this embodiment exceeds the upper limit, the amount of movement of the focusing lens group during focusing becomes large, making it difficult to reduce the size of the variable magnification optical system. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.770. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.750, or even 0.730.

[0021] On the other hand, if the corresponding value of conditional expression (3) of the variable magnification optical system of this embodiment falls below the lower limit, the sensitivity increases and the amount of movement of the focusing lens group during focusing decreases, making focus control difficult. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.200. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.300, or even 0.400.

[0022] Furthermore, it is desirable that the variable magnification optical system of this embodiment has a fourth lens group having positive refractive power and a fifth lens group having negative refractive power as the subsequent lens group, and that it satisfies the following conditional expression (4): (4) -3.000 < f5 / f3 < -0.500 however, f3: focal length of the third lens group f5: focal length of the fifth lens group

[0023] Conditional expression (4) defines the ratio between the focal length of the third lens group and the focal length of the fifth lens group. By satisfying conditional expression (4), the variable magnification optical system of this embodiment can maintain the power ratio between the third lens group and the fifth lens group within an appropriate range, and can effectively correct astigmatism and coma.

[0024] If the value corresponding to conditional expression (4) of the variable magnification optical system of this embodiment exceeds the upper limit, the refractive power of the third lens group becomes large relative to the refractive power of the fifth lens group, making it difficult to satisfactorily correct various aberrations, particularly astigmatism, in the wide-angle end state. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (4) to -0.800. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (4) to -1.000, or even -1.100.

[0025] On the other hand, if the corresponding value of conditional expression (4) of the variable magnification optical system of this embodiment falls below the lower limit, the refractive power of the fifth lens group becomes large relative to the refractive power of the third lens group, making it difficult to effectively correct various aberrations, particularly coma, in the telephoto end state. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (4) to -2.500. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (4) to -2.000, or even -1.400.

[0026] In addition, in the variable magnification optical system of this embodiment, it is desirable that the fourth lens group has a focusing lens group. With this configuration, the variable magnification optical system of this embodiment can make the focusing lens group smaller and lighter, and as a result, the variable magnification optical system and the lens barrel can be made smaller.

[0027] Furthermore, it is desirable that the variable magnification optical system of this embodiment satisfy the following conditional expression (5). (5) 4.000 < f1 / f1Rw < 9.000 however, f1: focal length of the first lens group f1Rw: the composite focal length of the lens group arranged closer to the image plane than the first lens group in the wide-angle end state

[0028] Conditional expression (5) defines the ratio between the focal length of the first lens group and the combined focal length of the lens group located closer to the image plane than the first lens group in the wide-angle end state. By satisfying conditional expression (5), the variable magnification optical system of this embodiment can effectively correct various aberrations, including coma in the wide-angle end state. Furthermore, by satisfying conditional expression (5), fluctuations in various aberrations, including spherical aberration, can be suppressed when changing magnification from the wide-angle end state to the telephoto end state.

[0029] If the value corresponding to conditional expression (5) of the variable magnification optical system of this embodiment exceeds the upper limit, the refractive power of the lens group arranged closer to the image plane than the first lens group in the wide-angle end state becomes large, making it difficult to effectively correct various aberrations, particularly coma, in the wide-angle end state. Furthermore, it becomes difficult to suppress fluctuations in various aberrations, including spherical aberration, when changing magnification from the wide-angle end state to the telephoto end state. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (5) to 8.500. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (5) to 8.000, or even 6.500.

[0030] On the other hand, if the value corresponding to conditional expression (5) of the variable magnification optical system of this embodiment falls below the lower limit, the refractive power of the first lens group becomes large, making it difficult to effectively correct various aberrations, particularly coma, in the wide-angle end state. Furthermore, it becomes difficult to suppress fluctuations in various aberrations, including spherical aberration, when changing magnification from the wide-angle end state to the telephoto end state. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (5) to 5.000. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (5) to 5.100, or even 5.200.

[0031] Furthermore, it is desirable that the variable magnification optical system of this embodiment satisfy the following conditional expression (6). (6)nd3fp < 1.800 however, nd3fp: refractive index of the lens with the highest refractive index in the third lens group

[0032] Conditional expression (6) defines the refractive index of the lens with the strongest refractive power in the third lens group. By using a glass material with high refractive power that satisfies conditional expression (6), the variable magnification optical system of this embodiment can effectively correct axial chromatic aberration and spherical aberration.

[0033] If the value corresponding to conditional expression (6) of the variable magnification optical system of this embodiment exceeds the upper limit, the refractive power of the third lens group increases, making it difficult to effectively correct axial chromatic aberration and spherical aberration. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (6) to 1.750. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (6) to 1.700, or even 1.650.

[0034] Furthermore, it is desirable that the variable magnification optical system of this embodiment satisfy the following conditional expression (7). (7) 50.000 < νd3p however, νd3p: the Abbe number of the lens in the third lens group with the smallest Abbe number

[0035] Condition (7) defines the Abbe number of the lens in the third lens group that has the smallest Abbe number. In the variable magnification optical system of this embodiment, by using a low-dispersion glass material that satisfies conditional expression (7), it is possible to impart anomalous dispersion to the third lens group, thereby enabling excellent correction of axial chromatic aberration and spherical aberration.

[0036] If the corresponding value of conditional expression (7) of the variable magnification optical system of this embodiment falls below the lower limit, it will be impossible to provide sufficient anomalous dispersion to the third lens group, making it difficult to effectively correct axial chromatic aberration and spherical aberration. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (7) to 55,000. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (7) to 58,000, or even 60,000.

[0037] Furthermore, it is desirable that the variable magnification optical system of this embodiment satisfy the following conditional expression (8). (8) 0.500 < 1 / βRw < 1.000 however, βRw: Lateral magnification of the lens group located closest to the image plane in the wide-angle end state

[0038] Conditional expression (8) defines the lateral magnification of the lens group located closest to the image plane in the wide-angle end state. By satisfying conditional expression (8), the variable magnification optical system of this embodiment can effectively correct various aberrations, including astigmatism, in the wide-angle end state.

[0039] If the value corresponding to conditional expression (8) of the variable magnification optical system of this embodiment exceeds the upper limit, the lateral magnification of the lens group positioned closest to the image plane in the wide-angle end state becomes small, making it difficult to effectively correct various aberrations, particularly astigmatism, in the wide-angle end state. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (8) to 0.950. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (8) to 0.900, or even 0.850.

[0040] On the other hand, if the value corresponding to conditional expression (8) of the variable magnification optical system of this embodiment falls below the lower limit, the lateral magnification of the lens group positioned closest to the image plane in the wide-angle end state becomes large, field curvature becomes more likely to occur in the wide-angle end state, and it becomes difficult to effectively correct various aberrations. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (8) to 0.550. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (8) to 0.600, or even 0.650.

[0041] It is also desirable that the variable magnification optical system of this embodiment satisfy the following conditional expression (9). (9) 0.500 < f2fn / f2 < 1.100 however, f2fn: focal length of the lens component in the second lens group closest to the object f2: focal length of the second lens group

[0042] Conditional expression (9) defines the ratio between the focal length of the lens component closest to the object in the second lens group and the focal length of the second lens group. By satisfying conditional expression (9), the variable magnification optical system of this embodiment can appropriately allocate the power of the lens component closest to the object in the second lens group, and can effectively correct various aberrations including spherical aberration.

[0043] If the value corresponding to conditional expression (9) of the variable magnification optical system of this embodiment exceeds the upper limit, the refractive power of the lens component closest to the object in the second lens group becomes weak, making it difficult to effectively correct various aberrations including spherical aberration. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (9) to 1.000. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (9) to 0.900, or even 0.850.

[0044] On the other hand, if the value corresponding to conditional expression (9) of the variable magnification optical system of this embodiment falls below the lower limit, the refractive power of the lens component closest to the object in the second lens group becomes too strong, making it difficult to effectively correct various aberrations including spherical aberration. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (9) to 0.600. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (9) to 0.650, or even 0.700.

[0045] It is also desirable that the variable magnification optical system of this embodiment satisfy the following conditional expression (10): (10) 0.300 < fF / ft < 1.400 however, fF: focal length of the focusing lens group ft: focal length of the variable magnification optical system in the telephoto end state

[0046] Conditional expression (10) defines the ratio between the focal length of the focusing lens group and the focal length of the variable magnification optical system in the telephoto end state. By satisfying conditional expression (10), the variable magnification optical system of this embodiment can suppress fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance, and can also achieve miniaturization of the variable magnification optical system and the lens barrel.

[0047] If the value corresponding to conditional expression (10) of the variable magnification optical system of this embodiment exceeds the upper limit, the refractive power of the focusing lens group will be weak, making it difficult to effectively correct fluctuations in aberrations, particularly fluctuations in spherical aberration, when focusing from an object at infinity to a close object. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (10) to 1.000. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (10) to 0.900, or even 0.850.

[0048] On the other hand, if the value corresponding to conditional expression (10) of the variable magnification optical system of this embodiment falls below the lower limit, the refractive power of the focusing lens group becomes large, making it difficult to effectively correct fluctuations in various aberrations, particularly fluctuations in spherical aberration, when focusing from an object at infinity to a close object. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (10) to 0.500. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (10) to 0.600, or even 0.700.

[0049] It is also desirable that the variable magnification optical system of this embodiment satisfy the following conditional expression (11): (11) 40.00° < ωw < 85.00° however, ωw: half angle of view of the variable magnification optical system in the wide-angle end state

[0050] Conditional expression (11) defines the half angle of view of the variable magnification optical system in the wide-angle end state. By satisfying conditional expression (11), the variable magnification optical system of this embodiment can have a wide angle of view while effectively correcting various aberrations such as coma, distortion, and field curvature.

[0051] If the value corresponding to conditional expression (11) of the variable magnification optical system of this embodiment exceeds the upper limit, the angle of view becomes too wide, making it difficult to satisfactorily correct various aberrations such as coma, distortion, and curvature of field. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (11) to 84.00°. To further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (11) to 83.00°, or even 82.00°.

[0052] On the other hand, if the value corresponding to conditional expression (11) of the variable magnification optical system of this embodiment falls below the lower limit, the angle of view becomes narrow, making it difficult to satisfactorily correct various aberrations. To achieve this, it is preferable to set the lower limit of conditional expression (11) to 41.00°. To further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional expression (11) to 42.00°, and more preferably 43.00°.

[0053] The optical device of this embodiment has a variable magnification optical system with the above-described configuration, which makes it possible to realize an optical device that is compact yet compatible with large image sensors and that can effectively correct various aberrations during magnification and focusing.

[0054] The method for manufacturing a variable magnification optical system according to this embodiment is a method for manufacturing a variable magnification optical system having, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a subsequent lens group having positive refractive power, wherein the distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, and the distance between the third lens group and the subsequent lens group changes when zooming from the wide-angle end state to the telephoto end state, the subsequent lens group is configured to have a focusing lens group that moves when focusing from an object at infinity to an object at a close distance, and the method is configured to satisfy the following conditional expressions (1) and (2): This makes it possible to manufacture a variable magnification optical system that is compact yet compatible with a large image sensor and that can effectively correct various aberrations when zooming and when focusing. (1) 2.00 < f1 / fw < 8.000 (2) 0.100 <BFw / fw < 1.00 however, f1: focal length of the first lens group fw: focal length of the variable magnification optical system in the wide-angle end state BFw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state

[0055] A variable magnification optical system according to a numerical example of this embodiment will be described below with reference to the accompanying drawings. (First Example) 1A, 1B, and 1C are cross-sectional views of a variable-magnification optical system according to Example 1 of this embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. The arrows below each lens group in Fig. 1A indicate the direction of movement of each lens group when changing magnification from the wide-angle end state to the intermediate focal length state. The arrows below each lens group in Fig. 1B indicate the movement locus of each lens group when changing magnification from the intermediate focal length state to the telephoto end state.

[0056] The variable magnification optical system according to this embodiment is composed of, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a subsequent lens group GR having positive refractive power.

[0057] The first lens group G1 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 consists of, in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, and a positive meniscus lens L23 with a convex surface facing the object side. The negative meniscus lens L21 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The third lens group G3 is composed of, in order from the object side along the optical axis, a biconvex positive lens L31, a cemented lens of a negative meniscus lens L32 with its convex surface facing the object side and a biconvex positive lens L33, and a cemented lens of a biconcave negative lens L34 and a biconvex positive lens L35. The biconvex positive lens L31 is a glass-molded aspherical lens with an aspherical lens surface facing the object side. It is a lens.

[0058] The subsequent lens group GR is composed of, in order from the object side along the optical axis, a fourth lens group G4 having positive refractive power and a fifth lens group G5 having negative refractive power. The fourth lens group G4 consists of, in order from the object side along the optical axis, a negative meniscus lens L41 with its concave surface facing the object side, and a biconvex positive lens L42. The biconvex positive lens L42 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The fifth lens group G5 consists of, in order from the object side along the optical axis, a positive meniscus lens L51 with its concave surface facing the object side, and a biconcave negative lens L52. The positive meniscus lens L51 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I.

[0059] Between the fifth lens group G5 and the image plane I, a filter FL such as a low-pass filter is disposed. On the image plane I, an image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed.

[0060] In the variable magnification optical system according to this embodiment, all of the lens groups from the first lens group G1 to the fifth lens group G5 move along the optical axis so that the distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, and the distance between the fourth lens group G4 and the fifth lens group G5 change when the magnification is changed from the wide-angle end state to the telephoto end state. In addition, the aperture stop S moves integrally with the third lens group G3 when the magnification is changed from the wide-angle end state to the telephoto end state. In the variable magnification optical system according to this embodiment, focusing from an object at infinity to an object at a close distance is performed by moving the fourth lens group G4, which serves as a focusing lens group, along the optical axis toward the object.

[0061] Table 1 below lists the values ​​of the specifications of the variable magnification optical system according to this example. In [Surface Data], m is the order of the optical surface counted from the object side, r is the radius of curvature, d is the surface spacing (the spacing between the nth surface (n is an integer) and the n+1th surface), nd is the refractive index for the d line (wavelength 587.6 nm), and νd is the Abbe number for the d line (wavelength 587.6 nm). Also, OP is the object surface, Dn (n is an integer) is the variable surface spacing, S is the aperture stop, and I is the image plane. Note that the radius of curvature r=∞ indicates a flat surface. The refractive index of air, nd=1.00000, is omitted. Also, if the lens surface is aspherical, an * is added to the surface number. The column for radius of curvature r shows the paraxial radius of curvature.

[0062] In [Various Data], f is the focal length, FNo is the F-number, ω is the half angle of view (unit: °), Y is the maximum image height, and TL is the total length of the variable magnification optical system according to this example, i.e., the distance on the optical axis from the first surface to the image surface I. BF is the back focus, i.e., the distance on the optical axis from the lens surface closest to the image side to the image surface I, and BF (air-equivalent length) is the value measured when an optical block such as a filter is removed from the optical path. W indicates the wide-angle end state, M indicates the intermediate focal length state, and T indicates the telephoto end state. [Lens group data] indicates the first surface number ST and focal length f of each lens group.

[0063] [Aspherical surface data] indicates the aspherical coefficients and conic constants for the aspherical surface shown in [Surface data] when the shape is expressed by the following equation. x=(h 2 / r) / [1+{1-κ(h / r) 2} 1 / 2 ] +A4h 4 +A6h 6 +A8h 8 +A10h 10 Here, h is the height in the direction perpendicular to the optical axis, x is the sag amount, which is the distance along the optical axis direction from the tangent plane of the vertex of the aspheric surface at height h to the aspheric surface, κ is the conic constant, and A4, A6, A8, A10 is the aspherical coefficient, and r is the paraxial radius of curvature, which is the radius of curvature of the reference sphere. is an integer) is "×10 -n ", for example, "1.234E-05" indicates "1.234 x 10 -5 The second-order aspherical coefficient A2 is 0, and is therefore omitted.

[0064] In the [Variable Distance Data], Dn (n is an integer) indicates the surface distance between the nth surface and the (n+1)th surface. Also, W indicates the wide-angle end state, M indicates the intermediate focal length state, T indicates the telephoto end state, infinity indicates when focusing on an object at infinity, and close distance indicates when focusing on an object at close range. [Conditional expression corresponding value] indicates the corresponding value of each conditional expression.

[0065] Here, the focal length f, radius of curvature r, and other length units listed in Table 1 are generally in millimeters. However, this is not a limitation, as the optical system can achieve the same optical performance even when proportionally enlarged or reduced. The symbols in Table 1 described above will be used in the same manner in the tables of the respective examples described later.

[0066] (Table 1) First Example [Face Data] mrd nd νd OP ∞ 1 73.00000 2.150 1.84666 23.8 2 47.49515 8.600 1.75500 52.3 3 417.04330 D3 4 400.00000 1.800 1.74353 49.5 * 5 17.04241 8.087 6 -181.13172 1.350 1.75500 52.3 7 49.98466 2.108 8 37.80684 3.693 2.00069 25.5 9 235.22758 D9 10(S) ∞ 1.500 *11 25.88353 4.048 1.55332 71.7 12 -254.63176 0.800 13 52.19394 1.000 1.83481 42.7 14 26.38369 3.546 1.61800 63.3 15 -150.00000 3.743 16 -33.68615 1.000 1.81600 46.6 17 17.28639 6.494 1.59319 67.9 18 -23.04098 D18 19 -22.45485 1.000 1.80100 34.9 20 -41.05177 0.103 21 59.92172 6.115 1.59201 67.0 *22 -26.25646 D22 23 -40.60645 3.489 1.58913 61.2 *24 -24.00000 5.786 25 -24.36536 1.500 1.61800 63.3 26 107.45414 D26 27 ∞ 1.600 1.51680 64.1 28 ∞ D28 I ∞ [Various items] Ratio: 2.75 WMT f 24.72 46.31 67.91 FNo 4.00 4.00 4.00 ω 43.3 24.0 16.7 Y 21.70 21.70 21.70 TL 121.583 134.978 151.029 BF 15.558 28.486 36.144 BF (air equivalent length) 15.013 27.941 35.599 [Lens group data] Lens group ST f First lens group 1 125.09 Second lens group 4 -28.96 Third lens group 10 39.65 4th lens group 19 56.05 Fifth lens group 23 -51.52 [Aspherical data] Surface κ A4 A6 A8 A10 5 0.00000e+00 2.11342e-05 4.21453e-08 -3.77216e-11 4.44697e-13 11 1.00000e+00 -5.01541e-06 1.10914e-09 4.72876e-11 -3.55280e-13 22 1.00000e+00 1.52181e-05 -2.09730e-08 -1.77284e-11 -1.36838e-13 24 1.00000e+00 3.09258e-06 3.56902e-08 -3.36788e-11 3.80333e-13 [Variable Interval Data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance D3 1.600 17.195 31.254 1.600 17.195 31.254 D9 23.690 8.562 2.895 23.690 8.562 2.895 D18 4.579 8.446 10.823 2.148 3.205 2.313 D22 8.245 4.378 2.000 10.675 9.619 10.510 D26 13.858 26.785 34.444 13.858 26.785 34.444 D28 0.100 0.101 0.101 0.100 0.101 0.101 [Conditional expression corresponding value] (1) f1 / fw=5.0602 (2) BFw / fw=0.6901 (3) βFw=0.5234 (4) f5 / f3=-1.2993 (5) f1 / f1Rw=5.7747 (6)nd3fp=1.5533 (7)νd3p=71.6835 (8)1 / βRw=0.7853 (9) f2fn / f2=0.8285 (10) fF / ft=0.8254 (11)ωw=43.3420°

[0067] 2A, 2B, and 2C are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. 3A, 3B, and 3C are diagrams showing various aberrations of the variable magnification optical system according to Example 1 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.

[0068] In each aberration diagram, FNO denotes the F-number, NA denotes the numerical aperture, A denotes the angle of incidence of light rays, i.e., the half-angle of view (unit: °), and H0 denotes the object height (unit: mm). Specifically, spherical aberration diagrams indicate the F-number FNO or numerical aperture NA corresponding to the maximum aperture, astigmatism diagrams and distortion diagrams indicate the maximum half-angle of view or the maximum object height, respectively, and coma diagrams indicate the values ​​for each half-angle of view or each object height. "d" denotes aberration at the d-line (wavelength 587.6 nm), and "g" denotes aberration at the g-line (wavelength 435.8 nm), respectively. Values ​​without "d" or "g" indicate aberration at the d-line. In astigmatism diagrams, the solid line denotes the sagittal image plane, and the dashed line denotes the meridional image plane. The coma diagrams indicate coma aberration, i.e., lateral aberration, at each half-angle of view or each object height. Note that the same symbols as in this embodiment are used in the aberration diagrams of the following examples.

[0069] From each aberration diagram, it can be seen that the variable magnification optical system according to this embodiment has excellent imaging performance by effectively correcting various aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close-distance objects.

[0070] (Second Example) 4A, 4B, and 4C are cross-sectional views of a variable-magnification optical system according to Example 2 of this embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. The arrows below each lens group in Fig. 4A indicate the direction of movement of each lens group when changing magnification from the wide-angle end state to the intermediate focal length state. The arrows below each lens group in Fig. 4B indicate the movement locus of each lens group when changing magnification from the intermediate focal length state to the telephoto end state.

[0071] The variable magnification optical system according to this embodiment is composed of, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a subsequent lens group GR having positive refractive power.

[0072] The first lens group G1 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 consists of, in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, and a positive meniscus lens L23 with a convex surface facing the object side. The negative meniscus lens L21 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The third lens group G3 consists of, in order from the object side along the optical axis, a biconvex positive lens L31, a cemented lens of a negative meniscus lens L32 with its convex surface facing the object side and a biconvex positive lens L33, and a cemented lens of a biconcave negative lens L34 and a biconvex positive lens L35. The biconvex positive lens L31 is a glass-molded aspherical lens with an aspherical lens surface facing the object side.

[0073] The subsequent lens group GR is composed of, in order from the object side along the optical axis, a fourth lens group G4 having positive refractive power and a fifth lens group G5 having negative refractive power. The fourth lens group G4 is, in order from the object side along the optical axis, a negative meniscus with a concave surface facing the object side The biconvex positive lens L42 is a glass-molded aspherical lens whose lens surface on the image plane I side is aspherical. The fifth lens group G5 consists of, in order from the object side along the optical axis, a positive meniscus lens L51 with its concave surface facing the object side, and a biconcave negative lens L52. The positive meniscus lens L51 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I.

[0074] Between the fifth lens group G5 and the image plane I, a filter FL such as a low-pass filter is disposed. On the image plane I, an image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed.

[0075] In the variable magnification optical system according to this embodiment, all of the lens groups from the first lens group G1 to the fifth lens group G5 move along the optical axis so that the distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, and the distance between the fourth lens group G4 and the fifth lens group G5 change when the magnification is changed from the wide-angle end state to the telephoto end state. In addition, the aperture stop S moves integrally with the third lens group G3 when the magnification is changed from the wide-angle end state to the telephoto end state. In the variable magnification optical system according to this embodiment, focusing from an object at infinity to an object at a close distance is performed by moving the fourth lens group G4, which serves as a focusing lens group, along the optical axis toward the object. Table 2 below lists the values ​​of the specifications of the variable magnification optical system according to this example.

[0076] (Table 2) Second Example [Face Data] mrd nd νd OP ∞ 1 71.32483 2.150 1.84666 23.8 2 47.40907 8.400 1.75500 52.3 3 322.63295 D3 4 400.00000 1.800 1.74353 49.5 * 5 16.36859 9.475 6 -167.05753 2.029 1.75500 52.3 7 52.89355 0.797 8 36.08835 4.010 2.00069 25.5 9 256.44936 D9 10(S) ∞ 1.500 *11 25.91417 3.857 1.55332 71.7 12 -275.22572 1.078 13 51.71743 1.000 1.83481 42.7 14 21.38295 4.402 1.61800 63.3 15 -80.10599 3.539 16 -29.70942 1.000 1.81600 46.6 17 18.35723 5.582 1.59349 67.0 18 -21.31475 D18 19 -21.98830 1.000 1.74950 35.2 20 -53.12352 0.100 21 62.90338 5.816 1.62263 58.2 *22 -25.22856 D22 23 -35.90246 3.521 1.62263 58.2 *24 -23.00000 6.177 25 -23.30716 1.500 1.61800 63.3 26 150.39447 D26 27 ∞ 1.600 1.51680 64.1 28∞D28 I∞ [Various data] Magnification ratio: 2.75 WMT f 24.72 46.31 67.90 FNo 4.00 4.00 4.00 ω 43.6 24.3 16.8 Y 21.70 21.70 21.70 TL 122.013 134.611 152.248 BF 15.085 29.244 35.661 BF (air equivalent length) 14.540 28.699 35.116 [Lens group data] Lens group ST f First lens group 1 128.74 Second lens group 4 -28.81 Third lens group 10 38.09 4th lens group 19 60.73 5th lens group 23 -52.48 [Aspherical data] Surface κ A4 A6 A8 A10 5 0.00000e+00 2.31089e-05 3.91931e-08 8.80919e-12 3.83889e-13 11 1.00000e+00 -6.11034e-06 4.65530e-09 -7.97458e-11 3.48297e-13 22 1.00000e+00 1.49147e-05 -1.52664e-08 -4.38703e-11 -3.36461e-14 24 1.00000e+00 3.38657e-06 2.78770e-08 3.43065e-11 1.67177e-13 [Variable Interval Data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance D3 1.607 15.176 31.798 1.607 15.176 31.798 D9 23.402 8.272 2.870 23.402 8.272 2.870 D18 4.665 9.193 11.184 2.019 3.622 2.045 D22 8.519 3.992 2.000 11.165 9.562 11.139 D26 13.385 27.544 33.962 13.385 27.544 33.962 D28 0.100 0.099 0.099 0.099 0.099 0.099 [Conditional expression corresponding value] (1) f1 / fw=5.2079 (2) BFw / fw=0.6709 (3) βFw=0.5717 (4) f5 / f3=-1.3777 (5) f1 / f1Rw=5.9279 (6)nd3fp=1.5533 (7)νd3p=71.6835 (8)1 / βRw=0.7923 (9) f2fn / f2=0.7983 (10) fF / ft=0.8944 (11)ωw=43.6046°

[0077] 5A, 5B, and 5C are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. 6A, 6B, and 6C are diagrams showing various aberrations of the variable magnification optical system according to Example 2 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.

[0078] From each aberration diagram, it can be seen that the variable magnification optical system according to this embodiment has excellent imaging performance by effectively correcting various aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close-distance objects.

[0079] (Third Example) 7A, 7B, and 7C are cross-sectional views of a variable-magnification optical system according to Example 3 of this embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. The arrows below each lens group in Fig. 7A indicate the direction of movement of each lens group when changing magnification from the wide-angle end state to the intermediate focal length state. The arrows below each lens group in Fig. 7B indicate the movement locus of each lens group when changing magnification from the intermediate focal length state to the telephoto end state.

[0080] The variable magnification optical system according to this embodiment is composed of, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a subsequent lens group GR having positive refractive power.

[0081] The first lens group G1 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 consists of, in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, and a positive meniscus lens L23 with a convex surface facing the object side. The negative meniscus lens L21 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The third lens group G3 consists of, in order from the object side along the optical axis, a positive meniscus lens L31 with a convex surface facing the object side, a cemented lens of a negative meniscus lens L32 with a convex surface facing the object side and a biconvex positive lens L33, and a cemented lens of a biconcave negative lens L34 and a biconvex positive lens L35. The positive meniscus lens L31 is a glass-molded aspherical lens with an aspherical lens surface facing the object side.

[0082] The subsequent lens group GR is composed of, in order from the object side along the optical axis, a fourth lens group G4 having positive refractive power and a fifth lens group G5 having negative refractive power. The fourth lens group G4 consists of, in order from the object side along the optical axis, a negative meniscus lens L41 with its concave surface facing the object side, and a biconvex positive lens L42. The biconvex positive lens L42 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The fifth lens group G5 is, in order from the object side along the optical axis, a positive meniscus with its concave surface facing the object side The positive meniscus lens L51 is a glass-molded aspherical lens whose lens surface on the image plane I side is aspherical.

[0083] Between the fifth lens group G5 and the image plane I, a filter FL such as a low-pass filter is disposed. On the image plane I, an image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed.

[0084] In the variable magnification optical system according to this embodiment, all of the lens groups from the first lens group G1 to the fifth lens group G5 move along the optical axis so that the distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, and the distance between the fourth lens group G4 and the fifth lens group G5 change when the magnification is changed from the wide-angle end state to the telephoto end state. In addition, the aperture stop S moves integrally with the third lens group G3 when the magnification is changed from the wide-angle end state to the telephoto end state. In the variable magnification optical system according to this embodiment, focusing from an object at infinity to an object at a close distance is performed by moving the fourth lens group G4, which serves as a focusing lens group, along the optical axis toward the object. Table 3 below lists the values ​​of the specifications of the variable magnification optical system according to this example.

[0085] (Table 3) Third Example [Face Data] mrd nd νd OP ∞ 1 77.74447 2.150 1.84666 23.8 2 53.55851 8.020 1.72916 54.6 3 478.39025 D3 4 1000.00000 2.000 1.74250 49.4 * 5 17.13499 9.008 6 -103.78967 1.500 1.75500 52.3 7 80.88445 0.942 8 41.82797 3.959 2.00069 25.5 9 874.65992 D9 10(S) ∞ 1.500 *11 25.63046 3.669 1.55332 71.7 12 649.10845 0.500 13 43.22955 1.000 1.83481 42.7 14 18.28418 4.715 1.61800 63.3 15 -90.27190 4.286 16 -32.75074 1.000 1.81600 46.6 17 18.81533 5.331 1.59349 67.0 18 -22.38426 D18 19 -20.95545 1.000 1.80610 33.3 20 -38.43736 0.450 21 70.13258 6.000 1.62263 58.2 *22 -25.20560 D22 23 -28.47777 3.307 1.69350 53.3 *24 -21.27208 6.193 25 -24.27627 1.500 1.61881 63.9 26 106.34326 D26 27 ∞ 1.600 1.51680 64.1 28∞D28 I∞ [Various data] Magnification ratio: 2.75 WMT f 24.72 46.31 67.90 FNo 4.00 4.28 4.00 ω 43.9 24.1 16.6 Y 21.70 21.70 21.70 TL 121.939 132.931 151.948 BF 14.546 28.656 35.001 BF (air equivalent length) 14.000 28.111 34.456 [Lens group data] Lens group ST f First lens group 1 137.34 Second lens group 4 -31.18 Third lens group 10 38.77 4th lens group 19 54.86 5th lens group 23 -47.21 [Aspherical data] Surface κ A4 A6 A8 A10 5 0.00000e+00 2.00686e-05 2.97810e-08 2.98043e-11 1.72509e-13 11 1.00000e+00 -5.31955e-06 1.45892e-09 2.19477e-11 -2.48946e-13 22 1.00000e+00 1.44228e-05 -1.30721e-08 5.35466e-12 -2.19209e-13 24 1.00000e+00 5.35295e-06 2.89950e-08 -2.95842e-11 3.75280e-13 [Variable Interval Data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance D3 1.704 15.094 33.353 1.704 15.094 33.353 D9 24.986 8.476 2.890 24.986 8.476 2.890 D18 4.613 8.792 10.677 2.183 3.795 2.527 D22 8.064 3.886 2.000 10.494 8.882 10.150 D26 12.846 26.958 33.303 12.846 26.958 33.303 D28 0.100 0.099 0.098 0.099 0.098 0.098 [Conditional expression corresponding value] (1) f1 / fw=5.5559 (2) BFw / fw=0.6491 (3) βFw=0.5546 (4) f5 / f3=-1.2178 (5) f1 / f1Rw=6.2478 (6)nd3fp=1.5533 (7)νd3p=71.6835 (8)1 / βRw=0.7706 (9) f2fn / f2=0.7537 (10) fF / ft=0.8080 (11)ωw=43.9044°

[0086] 8A, 8B, and 8C are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. 9A, 9B, and 9C are diagrams showing various aberrations of the variable magnification optical system according to Example 3 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.

[0087] From each aberration diagram, it can be seen that the variable magnification optical system according to this embodiment has excellent imaging performance by effectively correcting various aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close-distance objects.

[0088] (Fourth Example) 10A, 10B, and 10C are cross-sectional views of a variable magnification optical system according to Example 4 of this embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. The arrows below each lens group in Fig. 10A indicate the direction of movement of each lens group when changing magnification from the wide-angle end state to the intermediate focal length state. The arrows below each lens group in Fig. 10B indicate the movement locus of each lens group when changing magnification from the intermediate focal length state to the telephoto end state.

[0089] The variable magnification optical system according to this embodiment is composed of, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a subsequent lens group GR having positive refractive power.

[0090] The first lens group G1 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 consists of, in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, and a positive meniscus lens L23 with a convex surface facing the object side. The negative meniscus lens L21 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The third lens group G3 consists of, in order from the object side along the optical axis, a positive meniscus lens L31 with a convex surface facing the object side, a cemented lens of a negative meniscus lens L32 with a convex surface facing the object side and a biconvex positive lens L33, and a cemented lens of a biconcave negative lens L34 and a biconvex positive lens L35. The positive meniscus lens L31 is a glass-molded aspherical lens with an aspherical lens surface facing the object side.

[0091] The subsequent lens group GR is composed of, in order from the object side along the optical axis, a fourth lens group G4 having positive refractive power and a fifth lens group G5 having negative refractive power. The fourth lens group G4 consists of, in order from the object side along the optical axis, a negative meniscus lens L41 with its concave surface facing the object side, and a biconvex positive lens L42. The biconvex positive lens L42 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The fifth lens group G5 consists of, in order from the object side along the optical axis, a positive meniscus lens L51 with its concave surface facing the object side, and a biconcave negative lens L52. The positive meniscus lens L51 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I.

[0092] Between the fifth lens group G5 and the image plane I, a filter FL such as a low-pass filter is disposed. On the image plane I, an image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed.

[0093] In the variable magnification optical system according to this embodiment, all of the lens groups from the first lens group G1 to the fifth lens group G5 move along the optical axis so that the distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, and the distance between the fourth lens group G4 and the fifth lens group G5 change when the magnification is changed from the wide-angle end state to the telephoto end state. In addition, the aperture stop S moves integrally with the third lens group G3 when the magnification is changed from the wide-angle end state to the telephoto end state. In the variable magnification optical system according to this embodiment, focusing from an object at infinity to an object at a close distance is performed by moving the fourth lens group G4, which serves as a focusing lens group, along the optical axis toward the object. Table 4 below lists the values ​​of the specifications of the variable magnification optical system according to this example.

[0094] (Table 4) Fourth Example [Face Data] mrd nd νd OP ∞ 1 76.69882 2.150 1.84666 23.8 2 49.37863 8.183 1.75500 52.3 3 439.48582 D3 4 1000.00000 2.000 1.74250 49.4 * 5 17.13499 9.947 6 -92.86562 1.500 1.75500 52.3 7 89.43926 1.284 8 45.22218 3.631 2.00069 25.5 9 1279.93050 D9 10(S) ∞ 1.500 *11 25.91677 3.597 1.55332 71.7 12 261.64746 0.300 13 38.95443 1.000 1.83481 42.7 14 23.18065 4.122 1.61800 63.3 15 -155.71305 4.035 16 -65.68195 1.000 1.83481 42.7 17 15.75952 5.135 1.61800 63.3 18 -32.57355 D18 19 -20.56363 2.000 1.80100 34.9 20 -34.41474 1.000 21 89.46436 6.000 1.59201 67.0 *22 -24.96683 D22 23 -34.33374 3.425 1.55332 71.7 *24 -23.28316 4.520 25 -24.47581 1.500 1.61881 63.9 26 132.00709 D26 27 ∞ 1.500 1.51680 64.1 28∞D28 I∞ [Various data] Magnification ratio: 2.75 WMT f 24.72 46.31 67.90 FNo 4.00 4.18 4.00 ω 43.6 23.8 16.5 Y 21.70 21.70 21.70 TL 121.051 133.285 149.815 BF 14.060 26.434 33.679 BF (air equivalent length) 13.549 25.923 33.168 [Lens group data] Lens group ST f First lens group 1 131.85 Second lens group 4 -29.95 Third lens group 10 35.73 4th lens group 19 55.25 5th lens group 23 -46.59 [Aspherical data] Surface κ A4 A6 A8 A10 5 0.00000e+00 1.93492e-05 2.97056e-08 3.40451e-11 1.36704e-13 11 1.00000e+00 -5.53738e-06 5.67727e-10 5.02317e-11 -4.30689e-13 22 1.00000e+00 1.49131e-05 -1.16787e-08 1.79818e-12 -2.00447e-13 24 1.00000e+00 3.34976e-06 2.85281e-08 -3.37056e-11 3.81301e-13 [Variable Interval Data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance D3 1.800 17.426 32.352 1.800 17.426 32.352 D9 23.692 7.926 2.285 23.692 7.926 2.285 D18 5.643 9.324 11.669 2.987 3.852 2.996 D22 8.025 4.345 2.000 10.681 9.817 10.673 D26 12.460 24.834 32.078 12.460 24.834 32.078 D28 0.100 0.101 0.101 0.100 0.101 0.101 [Conditional expression corresponding value] (1) f1 / fw=5.3337 (2) BFw / fw=0.6294 (3) βFw=0.6214 (4) f5 / f3=-1.3040 (5) f1 / f1Rw=6.0287 (6)nd3fp=1.5533 (7)νd3p=71.6835 (8)1 / βRw=0.7672 (9) f2fn / f2=0.7846 (10) fF / ft=0.8135 (11)ωw=43.5536°

[0095] 11A, 11B, and 11C are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. 12A, 12B, and 12C are diagrams showing various aberrations of the variable magnification optical system according to Example 4 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.

[0096] From each aberration diagram, it can be seen that the variable magnification optical system according to this embodiment has excellent imaging performance by effectively correcting various aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close-distance objects.

[0097] (Fifth Example) 13A, 13B, and 13C are cross-sectional views of a variable magnification optical system according to Example 5 of this embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. The arrows below each lens group in Fig. 13A indicate the direction of movement of each lens group when changing magnification from the wide-angle end state to the intermediate focal length state. The arrows below each lens group in Fig. 13B indicate the movement locus of each lens group when changing magnification from the intermediate focal length state to the telephoto end state.

[0098] The variable magnification optical system according to this embodiment is composed of, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a subsequent lens group GR having positive refractive power.

[0099] The first lens group G1 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 consists of, in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, and a positive meniscus lens L23 with a convex surface facing the object side. The negative meniscus lens L21 is a glass-molded aspherical lens with aspherical surfaces on the object side and the image plane I side. The third lens group G3 consists of, in order from the object side along the optical axis, a positive meniscus lens L31 with a convex surface facing the object side, a cemented lens of a biconvex positive lens L32 and a negative meniscus lens L33 with a concave surface facing the object side, and a cemented lens of a biconcave negative lens L34 and a biconvex positive lens L35. The positive meniscus lens L31 is a glass-molded aspherical lens with an aspherical lens surface facing the object side.

[0100] The subsequent lens group GR is composed of, in order from the object side along the optical axis, a fourth lens group G4 having positive refractive power and a fifth lens group G5 having negative refractive power. The fourth lens group G4 consists of, in order from the object side along the optical axis, a negative meniscus lens L41 with its concave surface facing the object side, and a biconvex positive lens L42. The biconvex positive lens L42 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The fifth lens group G5 is composed of, in order from the object side along the optical axis, a negative biconcave lens L51 and a positive meniscus lens L52 with its convex surface facing the object side.

[0101] Between the fifth lens group G5 and the image plane I, a filter FL such as a low-pass filter is disposed. On the image plane I, an image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed.

[0102] In the variable magnification optical system according to this embodiment, all of the lens groups from the first lens group G1 to the fifth lens group G5 move along the optical axis so that the distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, and the distance between the fourth lens group G4 and the fifth lens group G5 change when the magnification is changed from the wide-angle end state to the telephoto end state. In addition, the aperture stop S moves integrally with the third lens group G3 when the magnification is changed from the wide-angle end state to the telephoto end state. In the variable magnification optical system according to this embodiment, focusing from an object at infinity to an object at a close distance is performed by moving the fourth lens group G4, which serves as a focusing lens group, along the optical axis toward the object. Table 5 below lists the values ​​of the specifications of the variable magnification optical system according to this example.

[0103] (Table 5) Fifth Example [Face Data] mrd nd νd OP ∞ 1 78.28661 2.200 1.94595 18.0 2 55.12139 7.465 1.83481 42.7 3 416.58751 D3 * 4 600.00000 2.000 1.74330 49.3 * 5 14.79065 9.268 6 -80.00000 1.500 1.49782 82.6 7 112.11004 0.150 8 35.97822 3.589 2.00069 25.5 9 115.26124 D9 10(S) ∞ 1.500 *11 22.34807 3.756 1.61881 63.9 12 215.30357 4.534 13 116.19602 4.736 1.61800 63.3 14 -16.99559 1.000 1.61266 44.5 15 -42.70583 0.150 16 -3080.10830 1.000 1.83481 42.7 17 14.42589 4.664 1.49782 82.6 18 -73.51276 D18 19 -32.33307 1.000 1.80100 34.9 20 -94.44385 0.415 21 34.51492 5.500 1.69350 53.2 *22 -39.28206 D22 23 -146.73735 1.500 1.59319 67.9 24 27.39699 2.426 25 58.23961 2.594 1.69895 30.1 26 100.00000 D26 27 ∞ 1.500 1.51680 64.1 28∞D28 I∞ [Various data] Magnification ratio: 2.75 WMT f 24.71 46.30 67.86 FNo 4.00 4.16 4.00 ω 43.3 23.8 16.5 Y 21.70 21.70 21.70 TL 117.744 130.814 147.913 BF 19.640 33.380 41.487 BF (air equivalent length) 19.129 32.869 40.976 [Lens group data] Lens group ST f First lens group 1 121.95 Second lens group 4 -27.81 Third lens group 10 36.02 4th lens group 19 45.26 5th lens group 23 -48.61 [Aspherical data] Surface κ A4 A6 A8 A10 4 1.00000e+00 1.94041e-06 -1.27348e-08 2.13014e-11 -1.37676e-14 5 0.00000e+00 2.59781e-05 6.01951e-08 -1.23842e-10 2.09998e-13 11 1.00000e+00 -1.43227e-05 1.69157e-08 -3.97283e-10 1.27743e-12 22 1.00000e+00 1.66914e-05 -1.21729e-08 -1.24851e-12 9.57183e-15 [Variable Interval Data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance D3 2.000 16.993 31.289 2.000 16.993 31.289 D9 24.595 8.932 3.628 24.595 8.932 3.628 D18 4.555 7.160 9.062 2.811 3.351 2.811 D22 6.007 3.402 1.500 7.751 7.211 7.751 D26 18.040 31.781 39.888 18.040 31.781 39.888 D28 0.100 0.100 0.100 0.100 0.099 0.100 [Conditional expression corresponding value] (1) f1 / fw=4.9349 (2) BFw / fw=0.8998 (3) βFw=0.5108 (4) f5 / f3=-1.3496 (5) f1 / f1Rw=5.6533 (6)nd3fp=1.6188 (7)νd3p=63.8544 (8)1 / βRw=0.6758 (9) f2fn / f2=0.7346 (10) fF / ft=0.6668 (11)ω=43.2711°

[0104] 14A, 14B, and 14C are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. 15A, 15B, and 15C are diagrams showing various aberrations of the variable magnification optical system according to Example 5 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.

[0105] From each aberration diagram, it can be seen that the variable magnification optical system according to this embodiment has excellent imaging performance by effectively correcting various aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close-distance objects.

[0106] (Sixth Example) Figures 16A, 16B, and 16C are cross-sectional views of a variable magnification optical system according to Example 6 of this embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. The arrows below each lens group in Figure 16A indicate the direction of movement of each lens group when changing magnification from the wide-angle end state to the intermediate focal length state. The arrows below each lens group in Figure 16B indicate the movement locus of each lens group when changing magnification from the intermediate focal length state to the telephoto end state.

[0107] The variable magnification optical system according to this embodiment is composed of, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a subsequent lens group GR having positive refractive power.

[0108] The first lens group G1 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side. The second lens group G2 consists of, in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, and a positive meniscus lens L23 with a convex surface facing the object side. The negative meniscus lens L21 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The third lens group G3 consists of, in order from the object side along the optical axis, a biconvex positive lens L31, a cemented lens of a positive meniscus lens L32 with its concave surface facing the object side and a negative meniscus lens L33 with its concave surface facing the object side, and a cemented lens of a negative meniscus lens L34 with its convex surface facing the object side and a positive meniscus lens L35 with its convex surface facing the object side. The biconvex positive lens L31 is a glass-molded aspherical lens with an aspherical lens surface facing the object side.

[0109] The subsequent lens group GR is composed of, in order from the object side along the optical axis, a fourth lens group G4 having positive refractive power and a fifth lens group G5 having negative refractive power. The fourth lens group G4 consists of, in order from the object side along the optical axis, a negative meniscus lens L41 with a concave surface facing the object side and a positive meniscus lens L42 with a concave surface facing the object side. The negative meniscus lens L41 is a glass-molded aspherical lens with an aspherical lens surface facing the object side. The positive meniscus lens L42 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I side. The fifth lens group G5 is composed of, in order from the object side along the optical axis, a positive meniscus lens L51 with its concave surface facing the object side, and a negative biconcave lens L52.

[0110] Between the fifth lens group G5 and the image plane I, a filter FL such as a low-pass filter is disposed. On the image plane I, an image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed.

[0111] In the variable magnification optical system according to this embodiment, when the magnification is changed from the wide-angle end state to the telephoto end state, the first lens group All of the lens groups from the first lens group G1 to the fifth lens group G5 move along the optical axis so that the distances between G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, and the distance between the fourth lens group G4 and the fifth lens group G5 change. Furthermore, the aperture diaphragm S moves integrally with the third lens group G3 when changing magnification from the wide-angle end state to the telephoto end state. In the variable magnification optical system according to this embodiment, focusing from an object at infinity to an object at a close distance is performed by moving the fourth lens group G4, which serves as a focusing lens group, along the optical axis toward the object. Table 6 below lists the values ​​of the specifications of the variable magnification optical system according to this example.

[0112] (Table 6) Sixth Example [Face Data] mrd nd νd OP ∞ 1 60.32635 2.039 1.80809 22.7 2 41.97920 8.268 1.75500 52.3 3 207.34902 D3 4 1000.00000 2.000 1.82886 42.3 * 5 15.73567 8.461 6 -59.96573 1.500 1.49782 82.6 7 49.78382 0.150 8 35.18437 4.075 1.98917 26.2 9 1619.58040 D9 10(S) ∞ 1.500 *11 25.50000 4.170 1.55332 71.7 12 -65.45591 3.367 13 -32.91804 3.671 1.83645 42.6 14 -14.77178 1.500 1.94754 27.1 15 -26.35178 0.150 16 26.26299 1.500 1.99662 26.6 17 13.56251 3.695 1.64836 33.2 18 37.92217 D18 *19 -45.13942 1.500 1.58313 59.4 20 -55.10622 4.314 21 -45.22291 5.000 1.55332 71.7 *22 -17.65257 D22 23 -60.30075 8.069 1.65648 32.5 24 -15.50000 1.500 1.75698 36.7 25 290.03399 D25 26 ∞ 1.500 1.51680 64.1 27∞D27 I∞ [Various data] Magnification ratio: 2.75 WMT f 24.72 46.31 67.90 FNo 4.00 4.09 4.00 ω 44.7 24.0 16.7 Y 21.70 21.70 21.70 TL 116.526 128.486 142.973 BF 14.627 25.478 33.218 BF (air equivalent length) 14.116 24.967 32.707 [Lens group data] Lens group ST f First lens group 1 114.00 Second lens group 4 -26.90 Third lens group 10 31.86 4th lens group 19 53.18 5th lens group 23 -48.77 [Aspherical data] Surface κ A4 A6 A8 A10 5 0.00000e+00 2.28397e-05 5.52091e-08 -3.85159e-11 3.96575e-13 11 1.00000e+00 -1.02420e-05 -5.12185e-09 -2.80701e-11 -2.18997e-13 19 1.00000e+00 -3.49441e-05 -2.07361e-07 1.87328e-09 -1.70790e-11 22 1.00000e+00 7.10600e-06 -6.76172e-08 4.93526e-10 -2.53168e-12 [Variable Interval Data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance D3 2.000 17.776 29.427 2.000 17.776 29.427 D9 21.834 7.167 2.262 21.834 7.167 2.262 D18 4.820 7.522 10.636 2.245 2.026 1.830 D22 6.816 4.114 1.000 9.392 9.610 9.806 D25 13.027 23.878 31.619 13.027 23.878 31.619 D27 0.100 0.100 0.100 0.100 0.100 0.100 [Conditional expression corresponding value] (1) f1 / fw=4.6115 (2) BFw / fw=0.6524 (3) βFw=0.6567 (4) f5 / f3=-1.5310 (5) f1 / f1Rw=5.3365 (6)nd3fp=1.5533 (7)νd3p=71.6835 (8)1 / βRw=0.7366 (9) f2fn / f2=0.7177 (10) fF / ft=0.7832 (11)ωw=44.7194°

[0113] 17A, 17B, and 17C are diagrams showing various aberrations of the variable magnification optical system according to Example 6 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. 18A, 18B, and 18C are diagrams showing the wide-angle zoom lens of the variable magnification optical system according to Example 6. 10A to 10C are diagrams illustrating various aberrations when focusing on a close object in an end state, an intermediate focal length state, and a telephoto end state.

[0114] From each aberration diagram, it can be seen that the variable magnification optical system according to this embodiment has excellent imaging performance by effectively correcting various aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close-distance objects.

[0115] (Seventh Example) Figures 19A, 19B, and 19C are cross-sectional views of a variable magnification optical system according to Example 7 of this embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. The arrows below each lens group in Figure 19A indicate the direction of movement of each lens group when changing magnification from the wide-angle end state to the intermediate focal length state. The arrows below each lens group in Figure 19B indicate the movement locus of each lens group when changing magnification from the intermediate focal length state to the telephoto end state.

[0116] The variable magnification optical system according to this embodiment is composed of, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a subsequent lens group GR having positive refractive power.

[0117] The first lens group G1 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a negative meniscus lens L11 with its convex surface facing the object side and a biconvex positive lens L12. The second lens group G2 consists of, in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a negative meniscus lens L22 with a concave surface facing the object side, and a positive meniscus lens L23 with a convex surface facing the object side. The negative meniscus lens L21 is a glass-molded aspherical lens with aspherical surfaces on the object side and the image plane I side. The third lens group G3 consists of, in order from the object side along the optical axis, a positive meniscus lens L31 with a convex surface facing the object side, a positive meniscus lens L32 with a convex surface facing the object side, and a cemented lens made up of a positive meniscus lens L33 with a convex surface facing the object side and a negative meniscus lens L34 with a convex surface facing the object side. The positive meniscus lens L31 is a glass-molded aspherical lens with an aspherical lens surface facing the object side.

[0118] The subsequent lens group GR is composed of, in order from the object side along the optical axis, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. The fourth lens group G4 is composed of a biconvex positive lens L41, which is a glass-molded aspherical lens with aspherical surfaces on both the object side and the image plane I side. The fifth lens group G5 is made up of a negative meniscus lens L51 with a convex surface facing the object side. The negative meniscus lens L51 is a glass-molded aspherical lens with an aspherical lens surface facing the object side. The sixth lens group G6 is made up of a negative meniscus lens L61 with its concave surface facing the object side.

[0119] Between the sixth lens group G6 and the image plane I, a filter FL such as a low-pass filter is disposed. On the image plane I, an image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed.

[0120] The variable magnification optical system according to this embodiment is configured such that, when the magnification is changed from the wide-angle end state to the telephoto end state, the distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, the distance between the fourth lens group G4 and the fifth lens group G5, and the distance between the fifth lens group G5 and the sixth lens group G6 change. G1, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move along the optical axis. At this time, the position of the sixth lens group G6 is fixed with respect to the image plane I. Furthermore, the aperture stop S moves integrally with the third lens group G3 when changing magnification from the wide-angle end state to the telephoto end state. In the variable magnification optical system according to this embodiment, focusing from an object at infinity to an object at a close distance is performed by moving the fourth lens group G4, which serves as a focusing lens group, along the optical axis toward the object. Table 7 below lists the values ​​of the specifications of the variable magnification optical system according to this example.

[0121] (Table 7) Seventh Example [Face Data] mrd nd νd OP ∞ 1 101.78373 2.263 1.84666 23.8 2 64.09488 8.457 1.75500 52.3 3 -4649.78570 D3 * 4 338.09183 2.000 1.85135 40.1 * 5 17.62582 9.239 6 -31.88780 1.500 1.49782 82.6 7 -480.92591 0.150 8 48.76651 3.362 2.00069 25.5 9 1462.00720 D9 10(S) ∞ 1.500 *11 40.00000 3.061 1.49710 81.5 12 746.47149 0.150 13 56.62003 3.000 1.85896 22.7 14 1991.68980 0.150 15 22.31377 3.732 1.49782 82.6 16 102.88645 1.500 1.85896 22.7 17 20.13958 D17 *18 25.58334 5.130 1.49710 81.5 *19 -26.20789 D19 *20 44.84857 1.500 1.74330 49.3 21 19.56479 D21 22 -58.99276 0.839 1.61800 63.3 23 -84.99207 21.000 24 0.00000 1.500 1.51680 64.1 25 0.00000 D25 I∞ [Various data] Magnification ratio: 2.75 WMT f 24.72 46.32 67.90 FNo 4.02 4.01 4.02 ω 43.5 23.3 16.4 Y 21.70 21.70 21.70 TL 115.000 129.999 145.678 BF 22.601 22.601 22.602 BF (air equivalent length) 22.090 22.090 22.091 [Lens group data] Lens group ST f First lens group 1 141.68 Second lens group 4 -27.31 Third lens group 10 59.45 4th lens group 18 26.93 5th lens group 20 -47.90 6th lens group 22 -315.95 [Aspherical data] Surface κ A4 A6 A8 A10 4 1.00000e+00 1.12967e-05 -4.46018e-08 1.00140e-10 -1.05741e-13 5 0.00000e+00 3.44021e-05 7.39481e-08 -2.03619e-10 1.51680e-12 11 1.00000e+00 -6.99848e-06 -1.23976e-08 1.83746e-10 -4.96062e-13 18 1.00000e+00 -1.46574e-05 2.12049e-07 -8.82713e-10 -5.22530e-12 19 1.00000e+00 2.32857e-05 1.32158e-07 -5.88648e-10 -6.83977e-12 20 1.00000e+00 4.54779e-06 -1.12679e-08 -3.81570e-10 0.00000e+00 [Variable Interval Data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance D3 2.000 22.166 34.570 2.000 22.166 34.570 D9 24.510 8.331 2.222 24.510 8.331 2.222 D17 5.931 5.867 5.409 4.929 3.275 0.788 D19 4.569 3.472 1.944 5.571 6.063 6.565 D21 7.856 20.029 31.398 7.856 20.029 31.398 D25 0.101 0.101 0.102 0.101 0.101 0.103 [Conditional expression corresponding value] (1) f1 / fw=5.7316 (2) BFw / fw=0.9668 (3) βFw=0.0452 (4) f5 / f3=-0.8058 (5) f1 / f1Rw=6.3640 (6)nd3fp=1.4971 (7)νd3p=81.5584 (8)1 / βRw=0.9286 (9) f2fn / f2=0.8021 (10) fF / ft=0.3965 (11)ωw=43.4833°

[0122] 20A, 20B, and 20C are diagrams showing various aberrations of the variable magnification optical system according to Example 7 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. 21A, 21B, and 21C are diagrams showing the wide-angle zoom lens of the variable magnification optical system according to Example 7. 10A to 10C are diagrams illustrating various aberrations when focusing on a close object in an end state, an intermediate focal length state, and a telephoto end state.

[0123] From each aberration diagram, it can be seen that the variable magnification optical system according to this embodiment has excellent imaging performance by effectively correcting various aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close-distance objects.

[0124] (Eighth Example) Figures 22A, 22B, and 22C are cross-sectional views of a variable magnification optical system according to Example 8 of this embodiment in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. The arrows below each lens group in Figure 22A indicate the direction of movement of each lens group when changing magnification from the wide-angle end state to the intermediate focal length state. The arrows below each lens group in Figure 22B indicate the movement locus of each lens group when changing magnification from the intermediate focal length state to the telephoto end state.

[0125] The variable magnification optical system according to this embodiment is composed of, in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an aperture stop S, a third lens group G3 having positive refractive power, and a subsequent lens group GR having positive refractive power.

[0126] The first lens group G1 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a negative meniscus lens L11 with its convex surface facing the object side and a biconvex positive lens L12. The second lens group G2 consists of, in order from the object side along the optical axis, a negative meniscus lens L21 with a convex surface facing the object side, a biconcave negative lens L22, and a positive meniscus lens L23 with a convex surface facing the object side. The negative meniscus lens L21 is a glass-molded aspherical lens with an aspherical lens surface facing the image plane I. The third lens group G3 consists of, in order from the object side along the optical axis, a biconvex positive lens L31, a cemented lens of a negative meniscus lens L32 with its convex surface facing the object side and a biconvex positive lens L33, and a cemented lens of a positive meniscus lens L34 with its concave surface facing the object side and a biconcave negative lens L35. The biconvex positive lens L31 is a glass-molded aspherical lens with an aspherical lens surface facing the object side.

[0127] The subsequent lens group GR is composed of, in order from the object side along the optical axis, a fourth lens group G4 having positive refractive power and a fifth lens group G5 having negative refractive power. The fourth lens group G4 consists of, in order from the object side along the optical axis, a positive meniscus lens L41 with its convex surface facing the object side, and a biconvex positive lens L42. The biconvex positive lens L42 is a glass-molded aspherical lens with aspherical surfaces on both the object side and the image plane I side. The fifth lens group G5 is composed of, in order from the object side along the optical axis, a cemented lens consisting of a biconvex positive lens L51 and a biconcave negative lens L52. The biconcave negative lens L52 is a glass-molded aspherical lens with an aspherical lens surface facing the object side.

[0128] Between the fifth lens group G5 and the image plane I, a filter FL such as a low-pass filter is disposed. On the image plane I, an image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed.

[0129] In the variable magnification optical system according to this embodiment, when the magnification is changed from the wide-angle end state to the telephoto end state, all of the lens groups from the first lens group G1 to the fifth lens group G5 move along the optical axis so that the distance between the first lens group G1 and the second lens group G2, the distance between the second lens group G2 and the third lens group G3, the distance between the third lens group G3 and the fourth lens group G4, and the distance between the fourth lens group G4 and the fifth lens group G5 change. It moves together with the third lens group G3. In the variable magnification optical system according to this embodiment, focusing from an object at infinity to an object at a close distance is performed by moving the positive meniscus lens L41 of the fourth lens group G4, which serves as a focusing lens group, along the optical axis toward the object. Table 8 below lists the values ​​of the specifications of the variable magnification optical system according to this example.

[0130] (Table 8) Eighth Example [Face Data] mrd nd νd OP ∞ 1 116.51174 2.150 1.84666 23.8 2 68.14169 8.500 1.75500 52.3 3 -1607.21650 D3 4 643.64333 2.000 1.85135 40.1 * 5 22.47852 12.291 6 -49.00635 1.500 1.49782 82.6 7 35.41428 0.100 8 32.93414 4.000 2.00069 25.5 9 134.12564 D9 10(S) ∞ 1.500 *11 23.68026 5.000 1.55332 71.7 12 -51.23473 1.136 13 87.42815 1.000 1.97484 25.9 14 48.00600 5.000 1.61800 63.3 15 -93.41134 1.653 16 -27.67767 4.500 1.61800 63.3 17 -14.25207 1.000 1.63137 35.1 18 3549.62960 D18 19 34.01132 1.500 1.83858 33.3 20 52.01107 6.500 *21 505.55440 4.000 1.59201 67.0 *22 -61.72425 D22 23 106.95458 10.000 1.51680 64.1 24 -20.00000 1.500 1.74330 49.3 *25 144.50680 D25 26 0.00000 1.500 1.51680 64.1 27 0.00000 D27 I ∞ [Various data] Magnification ratio: 2.75 WMT f 24.72 46.31 67.89 FNo 4.00 4.00 4.00 ω 44.9 23.8 16.5 Y 21.70 21.70 21.70 TL 121.839 134.775 154.929 BF 14.062 27.994 39.252 BF (air equivalent length) 13.551 27.483 38.741 [Lens group data] Lens group ST f First lens group 1 156.61 Second lens group 4 -26.22 Third lens group 10 38.65 4th lens group 19 53.93 5th lens group 23 -89.77 [Aspherical data] Surface κ A4 A6 A8 A10 5 0.00000e+00 1.29856e-05 3.72807e-08 -9.91643e-11 5.62653e-13 11 1.00000e+00 -6.13337e-06 1.52342e-08 -1.33494e-10 5.07280e-13 21 1.00000e+00 -1.56957e-05 -4.44053e-08 -8.01823e-10 -6.52474e-14 22 1.00000e+00 6.23173e-06 -4.75716e-08 -5.19265e-10 -1.02402e-13 25 1.00000e+00 1.25490e-06 3.00760e-08 -1.22687e-10 3.40306e-13 [Variable Interval Data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance D3 2.000 19.945 36.744 2.000 19.945 36.744 D9 20.989 5.771 1.000 20.989 5.771 1.000 D18 4.914 2.181 2.103 4.914 2.181 2.103 D22 5.044 4.055 1.000 6.288 6.671 5.279 D25 12.462 26.394 37.651 12.462 26.394 37.651 D27 0.100 0.100 0.101 0.100 0.100 0.101 [Conditional expression corresponding value] (1) f1 / fw=6.3354 (2) BFw / fw=0.6275 (3) βFw=0.7271 (4) f5 / f3=-2.3229 (5) f1 / f1Rw=8.1273 (6)nd3fp=1.5533 (7)νd3p=71.6835 (8)1 / βRw=0.8894 (9) f2fn / f2=1.0450 (10) fF / ft=1.3722 (11)ωw=45.6019°

[0131] 23A, 23B, and 23C are diagrams showing various aberrations of the variable magnification optical system according to Example 8 when focused on an object at infinity in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively. 24A, 24B, and 24C are diagrams showing various aberrations of the variable magnification optical system according to Example 8 when focusing on a close object in the wide-angle end state, the intermediate focal length state, and the telephoto end state, respectively.

[0132] From each aberration diagram, it can be seen that the variable magnification optical system according to this embodiment has excellent imaging performance by effectively correcting various aberrations from the wide-angle end state to the telephoto end state, and also has excellent imaging performance when focusing on close-distance objects.

[0133] According to each of the above embodiments, it is possible to realize a variable magnification optical system that is compact yet can accommodate a large image sensor, that effectively corrects various aberrations from the wide-angle end state to the telephoto end state, and that has excellent imaging performance even when focusing on a close-distance object.

[0134] The variable magnification optical system according to this embodiment has a magnification ratio of approximately 2 to 10, a focal length at the wide-angle end of approximately 20 to 30 mm in 35 mm equivalent, an F-number at the wide-angle end of approximately f / 2.0 to f / 4.5, and an F-number at the telephoto end of approximately f / 2.0 to f / 6.3. Furthermore, the above examples show specific examples of this embodiment, and this embodiment is not limited to these. The following content can be adopted as appropriate within the scope that does not impair the optical performance of the variable magnification optical system of this embodiment.

[0135] Although the numerical examples of the variable magnification optical system of this embodiment have been shown to have a five-group or six-group configuration, this embodiment is not limited to this, and variable magnification optical systems with other group configurations (e.g., seven groups, etc.) can also be configured. Specifically, a lens or lens group may be added to the most object-side or most image-side of the variable magnification optical systems of the above examples. Alternatively, a lens or lens group may be added between the first lens group G1 and the second lens group G2. Alternatively, a lens or lens group may be added between the second lens group G2 and the third lens group G3. Alternatively, a lens or lens group may be added between the third lens group G3 and the subsequent lens group GR.

[0136] In addition, in each of the above embodiments, the fourth lens group G4 and the fifth lens group G5, or the fourth lens group G4, the fifth lens group G5 and the sixth lens group G6 are shown as the lens groups that make up the subsequent lens group GR, but this is not limited to this.

[0137] In addition, in each of the above embodiments, one lens group or part of a lens group is used as the focusing lens group, but two or more lens groups may be used as the focusing lens group. Such a focusing lens group can also be used for autofocusing, and is suitable for driving by an autofocus motor, such as an ultrasonic motor, a stepping motor, or a VCM motor.

[0138] Furthermore, in the variable magnification optical systems of the above embodiments, any one of the lens groups may be configured to perform vibration reduction by moving all or part of it as an image stabilization group so as to include a component in a direction perpendicular to the optical axis, or by rotating (oscillating) it in a plane including the optical axis.

[0139] Furthermore, the lens surfaces of the lenses constituting the variable magnification optical systems of the above embodiments may be spherical, flat, or aspherical. Spherical or flat lens surfaces are preferred because they facilitate lens processing and assembly adjustment, preventing degradation of optical performance due to errors in lens processing and assembly adjustment. Furthermore, they are preferred because they minimize degradation of imaging performance even when the image plane is misaligned. If the lens surface is aspherical, it may be a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, or a hybrid aspherical surface in which a resin applied to a glass surface is formed into an aspherical shape. Furthermore, the lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0140] Furthermore, in the variable magnification optical systems of the above embodiments, it is preferable that the aperture stop S be located between the second lens group G2 and the third lens group G3, but it is also possible to use a configuration in which no component is provided as an aperture stop and the lens frame serves that role instead.

[0141] Furthermore, the lens surfaces of the lenses constituting the variable magnification optical systems of the above examples may be coated with an anti-reflection coating that has high transmittance over a wide wavelength range, thereby reducing flare and ghosting and achieving high-contrast optical performance.

[0142] Next, a camera equipped with the variable magnification optical system of this embodiment will be described with reference to FIG. FIG. 25 is a diagram showing the configuration of a camera equipped with the variable magnification optical system of this embodiment. As shown in FIG. 25, the camera 1 is a so-called mirrorless camera with interchangeable lenses, which is provided with the variable magnification optical system according to the first embodiment as the photographic lens 2.

[0143] In this camera 1, light from an object (subject) (not shown) is collected by a photographing lens 2 and captured via an OLPF (Optical Low Pass Filter) (not shown). An image of the subject is formed on the imaging surface of imaging unit 3. The image of the subject is then photoelectrically converted by a photoelectric conversion element provided in imaging unit 3 to generate an image of the subject. This image is displayed on an EVF (Electronic View Finder) 4 provided in camera 1. This allows the photographer to observe the subject through EVF 4. Furthermore, when the photographer presses a release button (not shown), the image of the subject generated by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can photograph the subject using the camera 1.

[0144] Here, the variable magnification optical system according to the first embodiment mounted as the photographic lens 2 in the camera 1 has good optical performance and is compact, as described above. That is, the camera 1 can be made compact, and can achieve high optical performance by satisfactorily correcting various aberrations from the wide-angle end state to the telephoto end state, and by providing excellent imaging performance even when focusing on a close-up object. Note that even if a camera is constructed with the variable magnification optical systems according to the second to eighth embodiments mounted as the photographic lens 2, it can achieve the same effects as the camera 1. Furthermore, even if the variable magnification optical systems according to the above embodiments are mounted on a single-lens reflex camera that has a quick-return mirror and observes a subject through a viewfinder optical system, it can achieve the same effects as the camera 1.

[0145] Next, a method for manufacturing the variable magnification optical system of this embodiment will be outlined with reference to FIG. FIG. 26 is a flow chart showing an outline of a method for manufacturing a variable magnification optical system according to this embodiment.

[0146] The manufacturing method of the variable magnification optical system of this embodiment shown in Figure 26 is a manufacturing method of a variable magnification optical system having, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a subsequent lens group having positive refractive power, and includes the following steps S1 to S3.

[0147] Step S1: When changing magnification from the wide-angle end state to the telephoto end state, the distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, and the distance between the third lens group and the subsequent lens group changes. Step S2: The subsequent lens group is configured to have a focusing lens group that moves when focusing from an object at infinity to an object at a close distance. Step S3: The variable magnification optical system is made to satisfy the following conditional expressions (1) and (2). (1) 2.00 < f1 / fw < 8.000 (2) 0.100 <BFw / fw < 1.00 however, f1: focal length of the first lens group fw: focal length of the variable magnification optical system in the wide-angle end state BFw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state

[0148] According to the manufacturing method of the variable magnification optical system of this embodiment, it is possible to realize a variable magnification optical system that is compact yet can accommodate large image sensors, that effectively corrects various aberrations from the wide-angle end state to the telephoto end state, and that has high optical performance with excellent imaging performance even when focusing on close-distance objects. [Explanation of symbols]

[0149] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group GR subsequent lens group S aperture stop I image plane

Claims

[Claim 1] The lens comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a subsequent lens group having positive refractive power; the subsequent lens group comprises, in order from the object side, a fourth lens group having positive refractive power and a fifth lens group having negative refractive power; During magnification change, the distance between the first lens group and the second lens group changes, the distance between the second lens group and the third lens group changes, the distance between the third lens group and the fourth lens group changes, and the distance between the fourth lens group and the fifth lens group changes, the subsequent lens group includes a focusing lens group that moves during focusing; A variable magnification optical system that satisfies the following condition: 2.00 < f1 / fw < 8.000 0.100 <BFw / fw < 1.00 however, f1: focal length of the first lens group fw: focal length of the variable magnification optical system in the wide-angle end state BFw: back focus of the variable magnification optical system in the wide-angle end state fw: focal length of the variable magnification optical system in the wide-angle end state

Images