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

Abstract

This variable magnification optical system, sequentially from the objective side, comprises: 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 subsequent lens group having a plurality of lens groups. The variable magnification optical system is configured such that, when changing magnification, the first and third lens groups are fixed with respect to an image surface, intervals between adjacent lens groups are changed, and the following conditional expression is satisfied.　0.24<(TL / f1) / (ft / fw)<0.55, in which TL represents the distance to the image surface from a lens surface on the furthermost objective side, f1 represents the focal distance of the first lens group, ft represents the focal distance of the variable magnification optical system in the telescopic end state, and fw represents the focal distance of the variable magnification optical system in the wide-angle end state.

Description

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

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

[0002] 2. Description of the Related Art Conventionally, variable magnification optical systems have been proposed for use in optical devices such as photographic cameras, electronic still cameras, and video cameras (see, for example, Japanese Patent Application Laid-Open No. 2003-222998).

[0003] Japanese Patent Application Laid-Open No. 2021-189401

[0004] The variable magnification optical system of the present disclosure 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 a plurality of lens groups, and during magnification variation, the first lens group and the third lens group are fixed with respect to the image plane, and the spacing between adjacent lens groups changes, and satisfies the following conditional expression: 0.24 < (TL / f1) / (ft / fw) < 0.55, where TL: distance from the lens surface closest to the object to the image plane, f1: focal length of the first lens group, ft: focal length of the variable magnification optical system in the telephoto end state, fw: focal length of the variable magnification optical system in the wide-angle end state.

[0005] A method for manufacturing a variable magnification optical system according to the present disclosure includes configuring 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 a plurality of lens groups, such that, during magnification variation, the first lens group and the third lens group are fixed with respect to the image plane, and the spacing between adjacent lens groups changes, and the following conditional expression is satisfied: 0.24 < (TL / f1) / (ft / fw) < 0.55, where TL: distance from the lens surface closest to the object to the image plane, f1: focal length of the first lens group, ft: focal length of the variable magnification optical system in the telephoto end state, fw: focal length of the variable magnification optical system in the wide-angle end state.

[0006] 1A is a cross-sectional view of a variable magnification optical system of Example 1 when focusing on an object at infinity in the wide-angle end state. (a) is a diagram of various aberrations of the variable magnification optical system of Example 1 when focusing on an object at infinity in the wide-angle end state, and (b) is a diagram of various aberrations of the variable magnification optical system of Example 1 when focusing on an object at infinity in the telephoto end state. (b) is a cross-sectional view of a variable magnification optical system of Example 2 when focusing on an object at infinity in the wide-angle end state. (a) is a diagram of various aberrations of the variable magnification optical system of Example 2 when focusing on an object at infinity in the wide-angle end state, and (b) is a diagram of various aberrations of the variable magnification optical system of Example 2 when focusing on an object at infinity in the telephoto end state. (b) is a cross-sectional view of a variable magnification optical system of Example 3 when focusing on an object at infinity in the wide-angle end state. (a) is a diagram of various aberrations of the variable magnification optical system of Example 3 when focusing on an object at infinity in the wide-angle end state, and (b) is a diagram of various aberrations of the variable magnification optical system of Example 3 when focusing on an object at infinity in the telephoto end state. 1A is a cross-sectional view of a variable magnification optical system of Example 4 when focusing on an object at infinity in the wide-angle end state. (a) is a diagram of various aberrations of the variable magnification optical system of Example 4 when focusing on an object at infinity in the wide-angle end state, and (b) is a diagram of various aberrations of the variable magnification optical system of Example 4 when focusing on an object at infinity in the telephoto end state. (b) is a cross-sectional view of a variable magnification optical system of Example 5 when focusing on an object at infinity in the wide-angle end state. (a) is a diagram of various aberrations of the variable magnification optical system of Example 5 when focusing on an object at infinity in the wide-angle end state, and (b) is a diagram of various aberrations of the variable magnification optical system of Example 5 when focusing on an object at infinity in the telephoto end state. (b) is a cross-sectional view of a variable magnification optical system of Example 6 when focusing on an object at infinity in the wide-angle end state. 1 is a schematic diagram of a camera equipped with the variable magnification optical system of the present embodiment. 2 is a flowchart showing an outline of a method for manufacturing the variable magnification optical system of the present embodiment.

[0007] Hereinafter, a variable magnification optical system, an optical device, and a method for manufacturing a variable magnification optical system according to embodiments of the present application 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 a plurality of lens groups, and during magnification variation, the first lens group and the third lens group are fixed with respect to the image plane, and the interval between each adjacent lens group changes, and satisfies the following conditional expression: (1) 0.24 < (TL / f1) / (ft / fw) < 0.55, where TL: distance from the lens surface closest to the object to the image plane, f1: focal length of the first lens group, ft: focal length of the variable magnification optical system in the telephoto end state, fw: focal length of the variable magnification optical system in the wide-angle end state.

[0009] The variable magnification optical system of this embodiment has 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 multiple lens groups, thereby making it possible to suppress fluctuations in various aberrations, including spherical aberration, during magnification variation.

[0010] Conditional expression (1) defines the ratio of the distance from the lens surface closest to the object to the image plane to the focal length of the first lens group, and the ratio of the focal length of the variable magnification optical system in the wide-angle end state to the focal length in the telephoto end state (variable magnification ratio). By satisfying conditional expression (1), the variable magnification optical system of this embodiment can suppress fluctuations in various aberrations, including spherical aberration, during magnification change.

[0011] In the variable magnification optical system of this embodiment, if the value of conditional expression (1) exceeds the upper limit, the refractive power of the first lens group becomes too strong relative to the distance from the lens surface closest to the object to the image plane and the variable magnification ratio, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during variable magnification.

[0012] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (1) to 0.55. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (1) to 0.53, and more preferably 0.50.

[0013] Furthermore, in the variable magnification optical system of this embodiment, if the value of conditional expression (1) falls below the lower limit, the refractive power of the first lens group becomes too weak relative to the distance from the lens surface closest to the object to the image plane and the variable magnification ratio, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during magnification.

[0014] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (1) to 0.24. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.28, 0.30, 0.33, or even 0.36.

[0015] In the variable magnification optical system of this embodiment, it is preferable to satisfy the following conditional expression (2): 3.00<f1 / (-f2)<5.80, where f2 is the focal length of the second lens group.

[0016] Conditional expression (2) defines the ratio between the focal length of the first lens group and the focal length of the second lens group. By satisfying conditional expression (2), the variable magnification optical system of this embodiment can suppress fluctuations in various aberrations, including coma, during magnification change.

[0017] In the variable magnification optical system of this embodiment, if the value of conditional expression (2) exceeds the upper limit, the refractive power of the second lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including coma, during magnification.

[0018] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (2) to 5.80. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (2) to 5.60, and more preferably 5.40.

[0019] Furthermore, in the variable magnification optical system of this embodiment, if the value of conditional expression (2) falls below the lower limit, the refractive power of the first lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including coma, during magnification.

[0020] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (2) to 3.00. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (2) to 3.30, 3.50, 3.75, or even 3.90.

[0021] In the variable magnification optical system of this embodiment, it is preferable to satisfy the following conditional expression (3): 0.45<f1 / f3<6.00, where f3 is the focal length of the third lens group.

[0022] Conditional expression (3) defines the ratio between the focal length of the first lens group and the focal length of the third lens group. By satisfying conditional expression (3), the variable magnification optical system of this embodiment can suppress fluctuations in various aberrations, including coma, during magnification change.

[0023] In the variable magnification optical system of this embodiment, if the value of conditional expression (3) exceeds the upper limit, the refractive power of the third lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including coma, during magnification.

[0024] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (3) to 6.00. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (3) to 5.50, 5.00, 4.80, 4.50, or even 4.00.

[0025] Furthermore, in the variable magnification optical system of this embodiment, if the value of conditional expression (3) falls below the lower limit, the refractive power of the first lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including coma, during magnification.

[0026] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (3) to 0.45. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.50, 0.55, or even 0.60.

[0027] In the variable magnification optical system of this embodiment, it is preferable that the subsequent lens group includes a focusing lens group that has negative refractive power and moves during focusing, and that the following conditional expression be satisfied: 0.30<f2 / fF<1.00 (4), where f2 is the focal length of the second lens group, and fF is the focal length of the focusing lens group.

[0028] In the variable magnification optical system of this embodiment, the subsequent lens group includes a focusing lens group, so that fluctuations in various aberrations, including spherical aberration, during focusing can be suppressed.

[0029] Conditional expression (4) defines the ratio between the focal length of the second lens group and the focal length of the focusing lens group. By satisfying conditional expression (4), the variable magnification optical system of this embodiment can suppress fluctuations in various aberrations, including coma, during magnification change, and can also suppress fluctuations in various aberrations, including spherical aberration, during focusing.

[0030] In the variable magnification optical system of this embodiment, if the value of conditional expression (4) exceeds the upper limit, the refractive power of the focusing lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing.

[0031] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (4) to 1.00. In order to more reliably achieve the effect of this embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.90, 0.80, 0.75, or even 0.70.

[0032] Furthermore, in the variable magnification optical system of this embodiment, if the value of conditional expression (4) falls below the lower limit, the refractive power of the second lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including coma, during magnification.

[0033] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (4) to 0.30. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.33, and more preferably 0.35.

[0034] In the variable magnification optical system of this embodiment, it is preferable that the final lens group, which is arranged closest to the image plane among the subsequent lens groups, is fixed relative to the image plane during magnification variation.

[0035] In the variable magnification optical system of this embodiment, by having such a configuration, the mechanism for moving each lens group when varying magnification can be simplified, and the variable magnification optical system can be made smaller and lighter.

[0036] In the variable magnification optical system of this embodiment, it is preferable that the subsequent lens group includes a focusing lens group that has negative refractive power and moves during focusing, and a final lens group that is disposed closest to the image plane, and that the following conditional expression be satisfied: (5) 2.00 < |fR| / (-fF) < 100.00, where fR is the focal length of the final lens group, and fF is the focal length of the focusing lens group.

[0037] Conditional expression (5) defines the ratio between the focal length of the final lens group and the focal length of the focusing lens group. By satisfying conditional expression (5), the variable magnification optical system of this embodiment can suppress fluctuations in various aberrations, including coma, during magnification change, and can also suppress fluctuations in various aberrations, including spherical aberration, during focusing.

[0038] In the variable magnification optical system of this embodiment, if the value of conditional expression (5) exceeds the upper limit, the refractive power of the focusing lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing.

[0039] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (5) to 100.00. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (5) to 80.00, 65.00, 55.00, 40.00, 25.00, or even 15.00.

[0040] Furthermore, in the variable magnification optical system of this embodiment, if the value of conditional expression (5) falls below the lower limit, the refractive power of the final lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including coma, during magnification.

[0041] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (5) to 2.00. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (5) to 2.30, 2.50, or even 2.70.

[0042] In addition, it is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (6): 0.15<BFw / fw<0.95, where BFw is the back focus of the variable magnification optical system when focused at infinity in the wide-angle end state.

[0043] Conditional expression (6) defines the ratio between the back focus of the variable magnification optical system when focused on infinity 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 (6), the variable magnification optical system of this embodiment can effectively correct various aberrations, including coma when focused on infinity in the wide-angle end state.

[0044] In the variable magnification optical system of this embodiment, if the value of conditional expression (6) exceeds the upper limit, the back focus becomes large relative to the focal length in the wide-angle end state, making it difficult to satisfactorily correct various aberrations, including coma when focusing at infinity in the wide-angle end state.

[0045] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (6) to 0.95. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (6) to 0.92, and more preferably 0.90.

[0046] Furthermore, in the variable magnification optical system of this embodiment, if the value of conditional expression (6) falls below the lower limit, the back focus becomes small relative to the focal length in the wide-angle end state, making it difficult to satisfactorily correct various aberrations, including coma when focusing on infinity in the wide-angle end state.

[0047] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (6) to 0.15. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (6) to 0.20, 0.30, 0.40, or even 0.45.

[0048] In addition, it is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (7): 0.08<BFt / ft<0.24 where BFt is the back focus of the variable magnification optical system when focused on infinity in the telephoto end state.

[0049] Conditional expression (7) defines the ratio between the back focus of the variable magnification optical system when focused on infinity in the telephoto end state and the focal length of the variable magnification optical system in the telephoto end state. By satisfying conditional expression (7), the variable magnification optical system of this embodiment can effectively correct various aberrations, including coma when focused on infinity in the telephoto end state.

[0050] In the variable magnification optical system of this embodiment, if the value of conditional expression (7) exceeds the upper limit, the back focus becomes large relative to the focal length in the telephoto end state, making it difficult to satisfactorily correct various aberrations, including coma when focusing at infinity in the telephoto end state.

[0051] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (7) to 0.24. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (7) to 0.22, and more preferably 0.20.

[0052] Furthermore, in the variable magnification optical system of this embodiment, if the value of conditional expression (7) falls below the lower limit, the back focus becomes small relative to the focal length in the telephoto end state, making it difficult to satisfactorily correct various aberrations, including coma when focusing at infinity in the telephoto end state.

[0053] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (7) to 0.08. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (7) to 0.09, and more preferably 0.10.

[0054] In the variable magnification optical system of this embodiment, it is preferable that the plurality of lens groups in the subsequent lens group include at least one lens group having positive refractive power, and that the following conditional expression be satisfied: 0.70<f1 / fRP<3.40 (8), where fRP is the focal length of the lens group having the strongest refractive power among the lens groups having positive refractive power included in the subsequent lens group.

[0055] In the variable magnification optical system of this embodiment, the subsequent lens group has at least one lens group with positive refractive power, so that fluctuations in various aberrations such as coma can be suppressed during magnification.

[0056] Conditional expression (8) defines the ratio between the focal length of the first lens group and the focal length of the lens group having the strongest positive refractive power among the lens groups included in the subsequent lens groups. By satisfying conditional expression (8), the variable magnification optical system of this embodiment can suppress fluctuations in various aberrations, including coma, during magnification variation.

[0057] In the variable magnification optical system of this embodiment, if the value of conditional expression (8) exceeds the upper limit, the refractive power of the lens group with the strongest refractive power among the lens groups with positive refractive power included in the subsequent lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations such as coma when varying the magnification.

[0058] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (8) to 3.40. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (8) to 3.30, 3.20, 3.08, or even 3.00.

[0059] Furthermore, in the variable magnification optical system of this embodiment, if the value of conditional expression (8) falls below the lower limit, the refractive power of the first lens group becomes too strong, making it difficult to suppress fluctuations in various aberrations, including coma, during magnification.

[0060] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (8) to 0.70. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (8) to 0.72, 0.80, 0.85, 0.90, or even 0.95.

[0061] Furthermore, it is preferable that the variable magnification optical system of this embodiment satisfy the following conditional expression (9): 0.50<Gw / Gt<1.50, where Gw is the distance from the lens surface of the variable magnification optical system closest to the object in the wide-angle end state to the center of gravity of the variable magnification optical system, and Gt is the distance from the lens surface of the variable magnification optical system closest to the object in the telephoto end state to the center of gravity of the variable magnification optical system.

[0062] Conditional expression (9) defines the ratio between the distance from the lens surface closest to the object of the variable magnification optical system to the center of gravity of the variable magnification optical system in the wide-angle end state and the distance from the lens surface closest to the object of the variable magnification optical system to the center of gravity of the variable magnification optical system in the telephoto end state. By satisfying conditional expression (9), the variable magnification optical system of this embodiment reduces the change in the center of gravity during magnification change, thereby achieving high operability.

[0063] If the variable magnification optical system of this embodiment does not satisfy conditional expression (9), the change in the center of gravity position during magnification will be large, impairing operability.

[0064] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (9) to 1.50. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (9) to 1.40, 1.30, 1.20, 1.10, or even 1.00.

[0065] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (9) to 0.50. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (9) to 0.60, 0.70, 0.80, or even 0.90.

[0066] In addition, it is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression (10): 30.00°<ωw, where ωw is the half angle of view of the variable magnification optical system in the wide-angle end state.

[0067] Conditional expression (10) defines the half angle of view of the variable magnification optical system in the wide-angle end state. By satisfying conditional expression (10), the variable magnification optical system of this embodiment can form an image of a wide range of subjects on the image plane.

[0068] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (10) to 30.00°. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (10) to 34.00°, or even 36.00°.

[0069] In addition, it is preferable that the variable magnification optical system of this embodiment satisfies the following conditional expression: ωt<15.00° (11), where ωt is the half angle of view of the variable magnification optical system in the telephoto end state.

[0070] Conditional expression (11) defines the half angle of view of the variable magnification optical system in the telephoto end state. By satisfying conditional expression (11), the variable magnification optical system of this embodiment can form a large image of a distant subject on the image plane.

[0071] In the variable magnification optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (11) to 15.00°. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (11) to 13.00°, or even 12.00°.

[0072] With the above configuration, it is possible to realize a variable magnification optical system that is small in size and has good imaging performance.

[0073] The optical apparatus of this embodiment has the variable magnification optical system configured as described above, which makes it possible to realize an optical apparatus with excellent optical performance.

[0074] The manufacturing method of the variable magnification optical system of this embodiment includes configuring 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 a plurality of lens groups, such that during magnification variation, the first lens group and the third lens group are fixed with respect to the image plane, and the intervals between adjacent lens groups change, and the following conditional expression is satisfied: (1) 0.24 < (TL / f1) / (ft / fw) < 0.55 where, TL: distance from the lens surface closest to the object to the image plane, f1: focal length of the first lens group, ft: focal length of the variable magnification optical system in the telephoto end state, fw: focal length of the variable magnification optical system in the wide-angle end state.

[0075] By using such a manufacturing method for an optical system, it is possible to manufacture a variable magnification optical system having good optical performance.

[0076] Numerical Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

[0077] First Embodiment FIG. 1 is a cross-sectional view of a variable magnification optical system of a first embodiment when focused on an object at infinity in the wide-angle end state.

[0078] The variable magnification optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power.

[0079] The first lens group G1 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, and a meniscus positive lens L13 with its convex surface facing the object side.

[0080] The second lens group G2 consists of, in order from the object side, a meniscus negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a meniscus negative lens L24 with a concave surface facing the object side.

[0081] The third lens group G3 comprises, in order from the object side, an aperture stop S, a biconvex positive lens L31, a cemented positive lens consisting of a biconvex positive lens L32 and a meniscus negative lens L33 with its concave surface facing the object side, and a cemented positive lens consisting of a meniscus negative lens L34 with its convex surface facing the object side and a biconvex positive lens L35.

[0082] The fourth lens group G4 is composed of a cemented negative lens consisting of a meniscus positive lens L41 with its concave surface facing the object side and a biconcave negative lens L42.

[0083] The fifth lens group G5 consists of, in order from the object side, a biconvex positive lens L51, a cemented negative lens consisting of a meniscus positive lens L52 with its concave surface facing the object side and a biconcave negative lens L53, a cemented positive lens consisting of a meniscus negative lens L54 with its convex surface facing the object side and a biconvex positive lens L55, and a meniscus negative lens L56 with its concave surface facing the object side.

[0084] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0085] The variable magnification optical system of this embodiment focuses by moving the fourth lens group G4 along the optical axis. When focusing on a close object from a state focused on infinity, the fourth lens group G4 is moved from the object side to the image plane side.

[0086] In the variable magnification optical system of this embodiment, the fourth lens group G4 and the fifth lens group G5 are the subsequent lens groups, the fourth lens group G4 is the focusing lens group, the fifth lens group G5 is the final lens group, and the fifth lens group G5 is the lens group with the strongest positive refractive power among the subsequent lens groups.

[0087] Table 1 below lists the values ​​of the specifications of the variable magnification optical system of this example.

[0088] In the [Overall Specifications], TL is the distance from the lens surface closest to the object to the image plane, fw is the focal length of the entire system in the wide-angle end state, ft is the focal length of the entire system in the telephoto end state, FNOw is the F-number in the wide-angle end state, FNOt is the F-number in the telephoto end state, ωw is the half angle of view (degrees) in the wide-angle end state, ωt is the half angle of view (degrees) in the telephoto end state, and Y is the maximum image height.

[0089] In the [Lens Specifications], m is the order of the optical surface counted from the object side, r is the radius of curvature, d is the surface spacing, nd is the refractive index for the d-line (wavelength 587.6 nm), and νd is the Abbe number for the d-line. A radius of curvature r=∞ indicates a flat surface. Additionally, in the [Lens Specifications], optical surfaces marked with an "*" are aspherical.

[0090] In [Aspherical Data], m represents the optical surface corresponding to the aspherical data, K represents the conic constant, and A4-A12 represent the aspherical coefficients.

[0091] The aspherical surface is expressed by the following formula (a), where y is the height in the direction perpendicular to the optical axis, S(y) is the distance (amount of sag) along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface, r is the radius of curvature (paraxial radius of curvature) of the reference spherical surface, K is the conic constant, and An is the n-th order aspherical coefficient. In each example, the second order aspherical coefficient A2 is 0. Also, "En" is expressed as "×10 －ｎ " indicates.

[0092] (a) S(y) = (y ２ / r) / 1 + (1-K×y ２ / r ２ ) １／２ + A4×y ４ + A6×y ６ + A8×y ８ + A10×y １０ + A12×y １２

[0093] The units of focal lengths fw and ft, radius of curvature r, and other lengths listed in Table 1 are "mm." However, this is not limited to this because the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0094] The symbols in Table 1 described above are similarly used in tables of other examples to be described later.

[0095] (Table 1) [Overall specifications] TL 185.45 fw 28.80 ft 131.00 FNOw 4.11 FNOt 4.12 ωw 38.46 ωt 8.68 Y 21.60 [Lens specifications] m r d nd νd 1) 203.5350 2.000 1.90366 31.27 2) 66.2025 10.955 1.59319 67.90 3) -394.6700 0.200 4) 61.5683 6.780 1.75500 52.34 5) 263.3113 D5 * 6) 180.9166 1.500 1.82098 42.50 7) 19.6183 6.756 8) -44.0068 1.500 1.83481 42.73 9) 82.0673 0.200 10) 43.9489 4.902 1.80809 22.74 11) -42.7886 0.967 12) -29.1485 1.500 1.81600 46.59 13) -206.5239 D13 14) ∞ 2.000 (Aperture stop) *15) 102.6863 2.882 1.59245 66.92 16) -108.3264 0.200 17) 44.1156 5.502 1.59319 67.90 18) -52.1552 1.500 1.85883 30.00 19) -90.3268 3.621 20) 41.9375 1.500 2.00100 29.12 21) 22.4452 7.995 1.55332 71.67 *22) -37.7944 D22 23) -101.0979 2.706 1.94595 17.98 24) -32.6426 1.500 1.77387 47.25 *25) 23.4907 D25 26) 38.2444 9.394 1.59319 67.90 27) -33.7518 0.200 28) -69.6810 7.610 1.78472 25.64 29) -19.0000 1.500 2.00069 25.46 30) 65.6562 0.210 31) 44.8073 1.500 1.90366 31.27 32) 23.5000 10.489 1.69895 30.13 33) -57.9472 5.237 *34) -20.4734 1.500 1.74310 49.44 35) -30.6723 D35 [Aspheric data] m K A4 A6 A8 A10 A12 6) 1.0000 3.202E-06 -7.029E-09 2.763E-11 -7.583E-14 1.181E-16 15) 1.0000 -8.531E-06 -1.770E-09 -7.217E-12 3.167E-14 22) 1.0000 6.339E-06 -1.292E-08 3.068E-11 -1.100E-14 25) 1.0000 -6.885E-06 -3.233E-09 1.766E-10 -1.843E-12 34) 1.0000 3.056E-06 8.008E-09 1.421E-10 -4.651E-13 1.075E-15 [Focal length data for each group] Group First surface Focal length G1 1 92.73 G2 6 -17.34 G3 14 24.62 G4 23 -26.67 G5 26 96.06 [Variable distance data] When focusing at infinity When focusing at close range Wide-angle end Mid-range Telephoto end Wide-angle end Mid-range Telephoto end D5 2.000 25.493 37.799 2.000 25.493 37.799 D13 37.799 14.305 2.000 37.799 14.305 2.000 D22 2.000 9.389 16.869 2.153 9.804 17.740 D25 21.523 14.134 6.655 21.370 13.720 5.783 D35 17.828 17.828 17.828 17.828 17.828 17.828.

[0096] FIG. 2A is a diagram showing various aberrations when the variable magnification optical system of the first embodiment is in the wide-angle end state and focused on an object at infinity, and FIG. 2B is a diagram showing various aberrations when the variable magnification optical system of the first embodiment is in the telephoto end state and focused on an object at infinity.

[0097] In each aberration diagram, FNO indicates the F-number, and Y indicates the image height. More specifically, spherical aberration diagrams indicate the F-number value corresponding to the maximum aperture, astigmatism diagrams and distortion diagrams indicate the maximum image height, and coma diagrams indicate the value of each image height. d indicates the d-line, and g indicates the g-line (wavelength 435.8 nm). In astigmatism diagrams, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. The same symbols as those used in the aberration diagrams of this embodiment are used in the aberration diagrams of other embodiments described below.

[0098] From each aberration diagram, it can be seen that the variable magnification optical system of this example appropriately corrects various aberrations and has high optical performance.

[0099] Second Example FIG. 3 is a cross-sectional view of a variable magnification optical system of a second example when focused on an object at infinity in the wide-angle end state.

[0100] The variable magnification optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power.

[0101] The first lens group G1 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, and a meniscus positive lens L13 with its convex surface facing the object side.

[0102] The second lens group G2 consists of, in order from the object side, a meniscus negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a meniscus negative lens L24 with a concave surface facing the object side.

[0103] The third lens group G3 comprises, in order from the object side, an aperture stop S, a biconvex positive lens L31, a cemented positive lens consisting of a biconvex positive lens L32 and a meniscus negative lens L33 with its concave surface facing the object side, and a cemented positive lens consisting of a meniscus negative lens L34 with its convex surface facing the object side and a biconvex positive lens L35.

[0104] The fourth lens group G4 is composed of a cemented negative lens consisting of a meniscus positive lens L41 with its concave surface facing the object side and a biconcave negative lens L42.

[0105] The fifth lens group G5 consists of, in order from the object side, a cemented negative lens consisting of a biconvex positive lens L51 and a meniscus negative lens L52 with its concave surface facing the object side, a biconvex positive lens L53, and a meniscus negative lens L54 with its concave surface facing the object side.

[0106] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

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

[0108] In the variable magnification optical system of this embodiment, the fourth lens group G4 and the fifth lens group G5 are the subsequent lens groups, the fourth lens group G4 is the focusing lens group, the fifth lens group G5 is the final lens group, and the fifth lens group G5 is the lens group with the strongest positive refractive power among the subsequent lens groups.

[0109] Table 2 below lists the values ​​of the specifications of the variable magnification optical system of this example.

[0110] (Table 2) [Overall specifications] TL 185.45 fw 28.80 ft 131.00 FNOw 4.12 FNOt 4.12 ωw 38.55 ωt 8.68 Y 21.60 [Lens specifications] m r d nd νd 1) 160.9680 2.000 1.85883 30.00 2) 66.6346 10.667 1.49782 82.57 3) -440.7488 0.200 4) 61.6751 6.785 1.75500 52.34 5) 270.2573 D5 * 6) 200.0407 1.500 1.82098 42.50 7) 19.4035 6.813 8) -50.3925 1.500 1.81600 46.59 9) 88.0073 0.200 10) 40.5880 4.660 1.80809 22.74 11) -61.3314 1.043 12) -35.5828 1.500 1.77250 49.62 13) -1523.3790 D13 14) ∞ 2.000 (Aperture stop) *15) 89.0223 2.817 1.59245 66.92 16) -138.8020 0.200 17) 43.1800 5.721 1.59319 67.90 18) -46.1385 1.500 2.00069 25.46 19) -75.7096 2.760 20) 42.7879 1.500 1.90265 35.77 21) 19.9289 8.552 1.55332 71.67 *22) -37.9809 D22 23) -91.1448 2.782 1.94595 17.98 24) -30.5403 1.500 1.77387 47.25 *25) 23.7535 D25 26) 48.8085 8.210 1.49782 82.57 27) -39.8555 1.500 2.00100 29.12 28) -1151.4031 0.247 29) 78.5798 9.000 1.55298 55.07 30) -35.4446 9.937 *31) -25.9824 1.500 1.74310 49.44 32) -39.1102 D32 [Aspheric data] m K A4 A6 A8 A10 A12 6) 1.0000 2.250E-06 -6.521E-09 2.698E-11 -8.238E-14 1.019E-16 15) 1.0000 -8.797E-06 -8.208E-11 -2.286E-11 5.285E-14 22) 1.0000 4.616E-06 -1.129E-08 2.220E-12 2.745E-14 25) 1.0000 -7.596E-06 3.224E-09 -2.256E-11 -6.035E-13 31) 1.0000 -3.031E-06 -7.979E-09 7.173E-11 -2.277E-13 3.068E-16 [Each group focal length data] Group starting plane focal length G1 1 94.25 G2 6 -17.77 G3 14 24.74 G4 23 -26.42 G5 26 76.08 [Variable distance data] When focusing at infinity When focusing at close range Wide-angle end Mid-range Telephoto end Wide-angle end Mid-range Telephoto end D5 2.000 25.602 37.954 2.000 25.602 37.954 D13 37.954 14.352 2.000 37.954 14.352 2.000 D22 2.000 9.302 16.644 2.160 9.726 17.519 D25 21.625 14.323 6.981 21.465 13.899 6.106 D32 25.282 25.282 25.281 25.282 25.282 25.281.

[0111] FIG. 4A is a diagram showing various aberrations when the variable magnification optical system of the second embodiment is in the wide-angle end state and focused on an object at infinity, and FIG. 4B is a diagram showing various aberrations when the variable magnification optical system of the second embodiment is in the telephoto end state and focused on an object at infinity.

[0112] From each aberration diagram, it can be seen that the variable magnification optical system of this example appropriately corrects various aberrations and has high optical performance.

[0113] Third Example FIG. 5 is a cross-sectional view of a variable magnification optical system of a third example when focused on an object at infinity in the wide-angle end state.

[0114] The variable magnification optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having positive refractive power.

[0115] The first lens group G1 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, and a meniscus positive lens L13 with its convex surface facing the object side.

[0116] The second lens group G2 consists of, in order from the object side, a meniscus negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a meniscus negative lens L24 with a concave surface facing the object side.

[0117] The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex positive lens L31, and a meniscus negative lens L32 with its concave surface facing the object side.

[0118] The fourth lens group G4 consists of, in order from the object side, a meniscus positive lens L41 with a convex surface facing the object side, a biconvex positive lens L42, a cemented positive lens consisting of a meniscus negative lens L43 with a convex surface facing the object side and a biconvex positive lens L44, and a meniscus negative lens L45 with a convex surface facing the object side.

[0119] The fifth lens group G5 is composed of a cemented negative lens made up of a meniscus negative lens L51 with a convex surface facing the object side and a meniscus positive lens L52 with a convex surface facing the object side.

[0120] The sixth lens group G6 is composed of, in order from the object side, a negative meniscus lens L61 with its concave surface facing the object side, and a positive biconvex lens L62.

[0121] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0122] The variable magnification optical system of this embodiment focuses by moving the fifth lens group G5 along the optical axis. When focusing on a close object from a state focused on infinity, the fifth lens group G5 is moved from the object side to the image plane side.

[0123] In the variable magnification optical system of this embodiment, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 correspond to the subsequent lens groups, the fifth lens group G5 corresponds to the focusing lens group, the sixth lens group G6 corresponds to the final lens group, and the fourth lens group G4 corresponds to the lens group with the strongest refractive power among the lens groups with positive refractive power included in the subsequent lens groups.

[0124] Table 3 below lists the values ​​of the specifications of the variable magnification optical system of this example.

[0125] (Table 3) [Overall specifications] TL 178.46 fw 28.84 ft 130.95 FNOw 4.12 FNOt 4.12 ωw 38.54 ωt 8.71 Y 21.60 [Lens specifications] m r d nd νd 1) 106.2485 1.200 1.85451 25.15 2) 72.9108 7.265 1.49782 82.57 3) -2566.3273 0.200 4) 73.1525 5.243 1.59319 67.90 5) 311.0755 D5 * 6) 407.0508 1.200 1.85108 40.12 7) 26.2159 7.148 8) -51.6266 1.200 1.72916 54.61 9) 51.4576 0.200 10) 45.6463 5.333 1.85451 25.15 11) -83.8936 2.473 *12) -28.9700 1.200 1.49782 82.57 13) -65.5471 D13 14) ∞ 2.000 (Aperture) 15) 95.8245 4.041 1.59349 67.00 16) -62.8425 0.940 17) -40.3456 1.651 1.87070 40.74 18) -65.9661 D18 *19) 25.9551 4.000 1.51680 64.14 20) 44.4253 0.645 21) 39.9828 5.500 1.59319 67.90 22) -391.0917 1.331 23) 48.6465 1.200 1.90366 31.27 24) 18.3320 7.807 1.59319 67.90 25) -171.4604 0.200 26) 77.7825 1.200 1.69343 53.30 *27) 73.7764 D27 28) 80.7818 1.200 1.95000 29.37 29) 16.7054 3.578 1.94595 17.98 30) 27.6369 D30 *31) -101.4351 1.200 1.85108 40.12 32) -42069.7150 3.381 33) 73.6536 5.500 1.54814 45.51 34) -164.9703 D34 [Aspheric data] m K A4 A6 A8 A10 A12 6) 1.0000 2.211E-06 -1.437E-09 1.171E-11 -2.870E-14 5.008E-17 12) 1.0000 -1.225E-07 -1.735E-09 -1.015E-11 19) 1.0000 -2.831E-06 -3.190E-09 -5.738E-12 -8.899E-15 27) 1.0000 1.265E-05 1.948E-08 1.185E-11 2.335E-13 31) 1.0000 -1.999E-06 2.863E-09 -3.559E-12 8.759E-15 [Focal length data for each group] Group Initial surface Focal length G1 1 105.19 G2 6 -24.34 G3 14 134.69 G4 19 35.45 G5 28 -46.01 G6 31 361.54 [Variable distance data] When focusing at infinity When focusing at close range Wide-angle end Mid-range Telephoto end Wide-angle end Mid-range Telephoto end D5 1.500 22.793 38.616 1.500 22.793 38.616 D13 39.116 17.822 2.000 39.116 17.822 2.000 D18 20.867 4.924 2.000 20.867 4.924 2.000 D27 2.529 4.659 10.992 2.905 5.282 12.275 D30 17.618 31.431 28.022 17.242 30.807 26.739 D34 18.793 18.798 18.797 18.793 18.798 18.797.

[0126] FIG. 6A is a diagram showing various aberrations when the variable magnification optical system of the third embodiment is in the wide-angle end state and focused on an object at infinity, and FIG. 6B is a diagram showing various aberrations when the variable magnification optical system of the third embodiment is in the telephoto end state and focused on an object at infinity.

[0127] From each aberration diagram, it can be seen that the variable magnification optical system of this example appropriately corrects various aberrations and has high optical performance.

[0128] Fourth Embodiment FIG. 7 is a cross-sectional view of a variable magnification optical system of a fourth embodiment when focused on an object at infinity in the wide-angle end state.

[0129] The variable magnification optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power.

[0130] The first lens group G1 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus-shaped negative lens L11 with its convex surface facing the object side and a meniscus-shaped positive lens L12 with its convex surface facing the object side, and a meniscus-shaped positive lens L13 with its convex surface facing the object side.

[0131] The second lens group G2 consists of, in order from the object side, a meniscus negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a meniscus negative lens L24 with a concave surface facing the object side.

[0132] The third lens group G3 is composed of, in order from the object side, an aperture stop S, and a cemented positive lens consisting of a biconvex positive lens L31 and a meniscus negative lens L32 with its concave surface facing the object side.

[0133] The fourth lens group G4 consists of, in order from the object side, a meniscus-shaped positive lens L41 with a convex surface facing the object side, a cemented positive lens of a meniscus-shaped positive lens L42 with a convex surface facing the object side and a biconvex positive lens L43, and a meniscus-shaped negative lens L44 with a convex surface facing the object side.

[0134] The fifth lens group G5 is composed of a cemented negative lens made up of a meniscus negative lens L51 with a convex surface facing the object side and a meniscus positive lens L52 with a convex surface facing the object side.

[0135] The sixth lens group G6 is composed of, in order from the object side, a positive meniscus lens L61 with its concave surface facing the object side, a negative meniscus lens L62 with its concave surface facing the object side, and a positive biconvex lens L63.

[0136] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0137] The variable magnification optical system of this embodiment focuses by moving the fifth lens group G5 along the optical axis. When focusing on a close object from a state focused on infinity, the fifth lens group G5 is moved from the object side to the image plane side.

[0138] In the variable magnification optical system of this embodiment, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 correspond to the subsequent lens groups, the fifth lens group G5 corresponds to the focusing lens group, the sixth lens group G6 corresponds to the final lens group, and the fourth lens group G4 corresponds to the lens group with the strongest refractive power among the lens groups with positive refractive power included in the subsequent lens groups.

[0139] Table 4 below lists the values ​​of the specifications of the variable magnification optical system of this example.

[0140] (Table 4) [Overall specifications] TL 179.47 fw 28.84 ft 130.95 FNOw 4.12 FNOt 4.12 ωw 38.54 ωt 8.69 Y 21.60 [Lens specifications] m r d nd νd 1) 100.3057 1.200 1.85451 25.15 2) 60.8344 8.099 1.53775 74.70 3) 469.7604 0.200 4) 76.2982 5.766 1.75500 52.34 5) 445.1784 D5 * 6) 489.6863 1.200 1.85108 40.12 7) 25.8725 8.554 8) -50.8620 1.200 1.83481 42.72 9) 76.2098 0.200 10) 53.6363 5.772 1.84666 23.80 11) -47.5523 0.904 12) -34.9057 1.200 1.74310 49.44 *13) -135.8499 D13 14) ∞ 4.500 (Aperture stop) *15) 63.0236 4.554 1.69343 53.30 16) -58.8213 1.200 1.95000 29.37 17) -207.1161 D17 *18) 33.7325 4.500 1.59319 67.90 19) 153.6733 3.481 20) 33.2491 1.200 1.90110 27.06 21) 23.3148 8.000 1.53775 74.70 22) -73.6961 0.200 23) 53.2656 1.200 1.85108 40.12 *24) 30.8637 D24 25) 104.0299 1.200 2.00069 25.46 26) 18.9870 4.800 1.94595 17.98 27) 39.8976 D27 *28) -103.0331 4.657 1.69343 53.30 29) -40.6980 5.706 30) -30.6104 1.200 1.91082 35.25 31) -216.9426 0.200 32) 55.8746 6.500 1.61266 44.46 33) -211.7306 D33 [Aspheric data] m K A4 A6 A8 A10 A12 6) 1.0000 1.488E-06 -5.065E-10 1.818E-12 1.359E-15 13) 1.0000 2.938E-07 -7.289E-10 1.426E-11 -2.828E-14 15) 1.0000 -1.642E-06 9.096E-10 -2.490E-12 18) 1.0000 9.832E-08 -5.129E-09 -2.654E-12 24) 1.0000 1.226E-05 2.280E-08 3.207E-12 1.685E-13 28) 1.0000 -1.332E-06 2.889E-09 2.329E-12 [Focal length data for each group] Group Initial surface Focal length G1 1 97.13 G2 6 -23.47 G3 14 89.27 G4 18 44.88 G5 25 -60.88 G6 28 -3286.39 [Variable interval data] When focusing at infinity When focusing at close range Wide-angle end Mid-range Telephoto end Wide-angle end Mid-range Telephoto end D5 1.500 23.030 37.587 1.500 23.030 37.587 D13 39.087 17.557 3.000 39.087 17.557 3.000 D17 22.857 6.314 2.000 22.857 6.314 2.000 D24 5.350 6.250 11.401 6.000 7.252 13.341 D27 9.813 25.456 24.618 9.162 24.454 22.679 D33 13.468 13.469 13.458 13.468 13.469 13.458.

[0141] FIG. 8A is a diagram showing various aberrations when the variable magnification optical system of the fourth embodiment is in the wide-angle end state and focused on an object at infinity, and FIG. 8B is a diagram showing various aberrations when the variable magnification optical system of the fourth embodiment is in the telephoto end state and focused on an object at infinity.

[0142] From each aberration diagram, it can be seen that the variable magnification optical system of this example appropriately corrects various aberrations and has high optical performance.

[0143] Fifth Example FIG. 9 is a cross-sectional view of a variable magnification optical system of a fifth example when focused on an object at infinity in the wide-angle end state.

[0144] The variable magnification optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, and a seventh lens group G7 having positive refractive power.

[0145] The first lens group G1 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, and a meniscus positive lens L13 with its convex surface facing the object side.

[0146] The second lens group G2 consists of, in order from the object side, a meniscus negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a meniscus negative lens L24 with a concave surface facing the object side.

[0147] The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex positive lens L31, and a meniscus negative lens L32 with its concave surface facing the object side.

[0148] The fourth lens group G4 is composed of, in order from the object side, a meniscus positive lens L41 with a convex surface facing the object side, and a cemented positive lens consisting of a biconvex positive lens L42 and a meniscus negative lens L43 with a concave surface facing the object side.

[0149] The fifth lens group G5 is composed of a cemented positive lens consisting of a meniscus negative lens L51 with a convex surface facing the object side and a biconvex positive lens L52, and a meniscus positive lens L53 with a convex surface facing the object side.

[0150] The sixth lens group G6 is composed of a cemented negative lens made up of a meniscus negative lens L61 with a convex surface facing the object side and a meniscus positive lens L62 with a convex surface facing the object side.

[0151] The seventh lens group G7 is composed of, in order from the object side, a negative meniscus lens L71 with a concave surface facing the object side, and a positive meniscus lens L72 with a convex surface facing the object side.

[0152] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0153] The variable magnification optical system of this embodiment focuses by moving the sixth lens group G6 along the optical axis. When focusing on a close object from a state focused on infinity, the sixth lens group G6 is moved from the object side to the image plane side.

[0154] In the variable magnification optical system of this embodiment, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 correspond to the subsequent lens groups, the sixth lens group G6 corresponds to the focusing lens group, and the seventh lens group G7 corresponds to the final lens group. Furthermore, the fourth lens group G4 corresponds to the lens group with the strongest refractive power among the lens groups with positive refractive power included in the subsequent lens groups.

[0155] Table 5 below lists the values ​​of the specifications of the variable magnification optical system of this example.

[0156] (Table 5) [Overall specifications] TL 169.45 fw 28.84 ft 116.40 FNOw 4.12 FNOt 4.12 ωw 38.52 ωt 9.80 Y 21.60 [Lens specifications] m r d nd νd 1) 93.2961 1.200 1.85451 25.15 2) 64.7090 8.994 1.49782 82.57 3) -1632.1248 0.200 4) 69.0153 5.266 1.59319 67.90 5) 278.2695 D5 * 6) 315.4615 1.200 1.77387 47.25 7) 23.3642 7.183 8) -56.9381 1.200 1.83481 42.73 9) 89.0147 0.200 10) 48.2552 5.210 1.84666 23.80 11) -77.2530 1.839 12) -33.1241 1.500 1.59319 67.90 13) -166.5029 D13 14) ∞ 2.000 (Aperture stop) *15) 103.5679 3.610 1.69343 53.30 16) -65.2717 0.920 17) -38.6388 1.605 1.80100 34.92 18) -75.8947 D18 *19) 32.3007 3.500 1.51680 64.14 20) 59.0298 0.200 21) 42.1175 5.000 1.59319 67.90 22) -136.2064 1.741 1.72047 34.71 23) -228.7783 D23 24) 41.7423 1.200 1.85451 25.15 25) 21.6999 6.682 1.49782 82.57 26) -240.2934 0.200 27) 76.7885 2.000 1.85108 40.12 *28) 108.2756 D28 29) 111.2012 1.200 1.95000 29.37 30) 17.1778 3.739 1.94595 17.98 31) 29.4041 D31 *32) -46.3988 1.200 1.85108 40.12 33) -80.8980 0.200 34) 57.3607 5.500 1.57501 41.50 35) 1745.7962 D35 [Aspheric data] m K A4 A6 A8 A10 A12 6) 1.0000 1.519E-06 -2.184E-10 1.352E-12 -1.201E-15 9.425E-18 15) 1.0000 -6.645E-07 1.393E-09 -3.960E-12 19) 1.0000 -2.186E-07 -1.597E-09 -1.186E-12 28) 1.0000 1.109E-05 1.403E-08 8.343E-12 1.499E-13 32) 1.0000 -1.684E-06 8.599E-10 3.075E-12 6.087E-16 [Focal length data for each group] Group Initial surface Focal length G1 1 96.71 G2 6 -23.18 G3 14 136.52 G4 19 43.42 G5 24 105.09 G6 29 -43.14 G7 32 469.29 [Variable interval data] When focusing at infinity When focusing at close range Wide-angle end Mid-range Telephoto end Wide-angle end Mid-range Telephoto end D5 1.619 20.213 32.811 1.619 20.213 32.811 D13 33.925 15.331 2.733 33.925 15.331 2.733 D18 18.781 3.212 2.000 18.781 3.212 2.000 D23 2.382 2.449 2.000 2.382 2.449 2.000 D28 2.394 4.128 8.760 2.777 4.750 9.887 D31 20.417 34.186 31.215 20.035 33.564 30.087 D35 15.440 15.449 15.451 15.440 15.449 15.451.

[0157] FIG. 10A is a diagram showing various aberrations when the variable magnification optical system of Example 5 is in the wide-angle end state and focused on an object at infinity, and FIG. 10B is a diagram showing various aberrations when the variable magnification optical system of Example 5 is in the telephoto end state and focused on an object at infinity.

[0158] From each aberration diagram, it can be seen that the variable magnification optical system of this example appropriately corrects various aberrations and has high optical performance.

[0159] Sixth Embodiment FIG. 11 is a cross-sectional view of a variable magnification optical system of a sixth embodiment when focused on an object at infinity in the wide-angle end state.

[0160] The variable magnification optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, and a seventh lens group G7 having positive refractive power.

[0161] The first lens group G1 is composed of, in order from the object side, a cemented positive lens consisting of a meniscus negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, and a meniscus positive lens L13 with its convex surface facing the object side.

[0162] The second lens group G2 consists of, in order from the object side, a meniscus negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a biconvex positive lens L23, and a meniscus negative lens L24 with a concave surface facing the object side.

[0163] The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex positive lens L31, and a meniscus negative lens L32 with its concave surface facing the object side.

[0164] The fourth lens group G4 is composed of, in order from the object side, a meniscus positive lens L41 with a convex surface facing the object side, and a cemented positive lens consisting of a biconvex positive lens L42 and a meniscus negative lens L43 with a concave surface facing the object side.

[0165] The fifth lens group G5 is composed of a cemented positive lens consisting of a meniscus negative lens L51 with a convex surface facing the object side and a biconvex positive lens L52, and a meniscus positive lens L53 with a convex surface facing the object side.

[0166] The sixth lens group G6 is composed of a cemented negative lens made up of a meniscus negative lens L61 with a convex surface facing the object side and a meniscus positive lens L62 with a convex surface facing the object side.

[0167] The seventh lens group G7 is composed of, in order from the object side, a negative meniscus lens L71 with a concave surface facing the object side, and a positive meniscus lens L72 with a convex surface facing the object side.

[0168] An image pickup element (not shown) made up of a CCD, CMOS, or the like is disposed on the image plane I.

[0169] The variable magnification optical system of this embodiment focuses by moving the sixth lens group G6 along the optical axis. When focusing on a close object from a state focused on infinity, the sixth lens group G6 is moved from the object side to the image plane side.

[0170] In the variable magnification optical system of this embodiment, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 correspond to the subsequent lens groups, the sixth lens group G6 corresponds to the focusing lens group, and the seventh lens group G7 corresponds to the final lens group. Furthermore, the fourth lens group G4 corresponds to the lens group with the strongest refractive power among the lens groups with positive refractive power included in the subsequent lens groups.

[0171] Table 6 below lists the values ​​of the specifications of the variable magnification optical system of this example.

[0172] (Table 6) [Overall specifications] TL 157.46 fw 28.84 ft 101.85 FNOw 4.12 FNOt 4.12 ωw 38.51 ωt 11.15 Y 21.60 [Lens specifications] m r d nd νd 1) 89.9694 1.200 1.85451 25.15 2) 61.8344 8.870 1.49782 82.57 3) -1810.4849 0.200 4) 64.2354 5.370 1.59319 67.90 5) 290.2968 D5 * 6) 5724.0693 1.200 1.77387 47.25 7) 22.3009 6.722 8) -51.4759 1.200 1.87070 40.74 9) 89.5799 0.200 10) 48.1451 4.981 1.84666 23.80 11) -65.5885 1.692 12) -29.8981 1.362 1.59319 67.90 13) -78.5606 D13 14) ∞ 2.000 (Aperture stop) *15) 120.1934 3.278 1.74310 49.44 16) -65.7245 0.960 17) -35.0667 1.651 1.85026 32.35 18) -62.4547 D18 *19) 29.6539 3.262 1.51680 64.14 20) 48.4068 0.200 21) 35.8637 5.000 1.59319 67.90 22) -160.1358 1.853 1.80000 29.84 23) -240.2036 D23 24) 41.9624 1.200 1.85451 25.15 25) 21.1993 6.047 1.49782 82.57 26) -424.5511 0.200 27) 68.6284 2.079 1.85108 40.12 *28) 114.7292 D28 29) 89.8202 1.200 1.95000 29.37 30) 16.6762 3.424 1.94595 17.98 31) 26.9989 D31 *32) -40.8570 1.200 1.85108 40.12 33) -66.9608 0.200 34) 54.9466 5.500 1.54814 45.79 35) 1434.5246 D35 [Aspheric data] m K A4 A6 A8 A10 A12 6) 1.0000 2.611E-06 -9.668E-10 4.188E-13 1.205E-14 -8.027E-18 15) 1.0000 -3.471E-07 1.740E-09 -3.975E-12 19) 1.0000 -3.712E-07 -1.673E-09 -2.490E-12 28) 1.0000 1.466E-05 2.424E-08 2.676E-12 3.610E-13 32) 1.0000 -1.048E-06 5.180E-09 -4.595E-12 1.454E-14 [Focal length data for each group] Group Initial surface Focal length G1 1 90.07 G2 6 -22.46 G3 14 140.83 G4 19 40.35 G5 24 101.24 G6 29 -41.95 G7 32 557.85 [Variable interval data] When focusing at infinity When focusing at close range Wide-angle end Mid-range Telephoto end Wide-angle end Mid-range Telephoto end D5 1.995 19.531 28.874 1.995 19.531 28.874 D13 28.880 11.344 2.000 28.880 11.344 2.000 D18 15.834 2.061 2.000 15.834 2.061 2.000 D23 2.490 2.378 2.000 2.490 2.378 2.000 D28 2.241 4.303 7.661 2.633 4.962 8.708 D31 20.172 31.996 29.078 19.781 31.337 28.030 D35 13.601 13.592 13.628 13.601 13.592 13.628 .

[0173] FIG. 12(a) is a diagram showing various aberrations when the variable magnification optical system of Example 6 is in the wide-angle end state and focused on an object at infinity, and FIG. 12(b) is a diagram showing various aberrations when the variable magnification optical system of Example 6 is in the telephoto end state and focused on an object at infinity.

[0174] From each aberration diagram, it can be seen that the variable magnification optical system of this example appropriately corrects various aberrations and has high optical performance.

[0175] According to each of the above-described embodiments, a variable magnification optical system having good optical performance can be realized.

[0176] The values ​​corresponding to the conditional expressions in each example are shown below.

[0177] TL is the distance from the lens surface closest to the object to the image plane, fw is the focal length of the variable magnification optical system in the wide-angle end state, and ft is the focal length of the variable magnification optical system in the telephoto end state. f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, and f3 is the focal length of the third lens group. fF is the focal length of the focusing lens group, fR is the focal length of the final lens group, and fRP is the focal length of the lens group with the strongest positive refractive power among the subsequent lens groups. BFw is the back focal length of the variable magnification optical system when focusing at infinity in the wide-angle end state, and BFt is the back focal length of the variable magnification optical system when focusing at infinity in the telephoto end state. Gw is the distance from the lens surface closest to the object of the variable magnification optical system in the wide-angle end state to the center of gravity of the variable magnification optical system, and Gt is the distance from the lens surface closest to the object of the variable magnification optical system in the telephoto end state to the center of gravity of the variable magnification optical system. ωw is the half angle of view of the variable magnification optical system in the wide-angle end state, and ωt is the half angle of view of the variable magnification optical system in the telephoto end state.

[0178] [Conditional expression corresponding values] Conditional expression 1st 2nd 3rd 4th 5th 6th (1) (TL / f1) / (ft / fw) 0.440 0.433 0.374 0.407 0.434 0.495 (2) f1 / (-f2) 5.348 5.304 4.321 4.138 4.172 4.011 (3) f1 / f3 3.767 3.809 0.781 1.088 0.708 0.640 (4) f2 / fF 0.650 0.673 0.529 0.386 0.537 0.535 (5) |fR| / (-fF) 3.602 2.880 7.858 53.979 10.878 13.297 (6) BFw / fw 0.619 0.878 0.652 0.467 0.535 0.472 (7) BFt / ft 0.136 0.193 0.144 0.103 0.133 0.134 (8) f1 / fRP 0.965 1.239 2.967 2.164 2.227 2.232 (9) Gw / Gt 0.937 0.913 0.917 0.939 0.925 0.937 (10) ωw 38.458° 38.547° 38.544° 38.541° 38.523° 38.515° (11) ωt 8.677° 8.678° 8.715° 8.694° 9.795° 11.148°

[0179] The above examples are merely examples of the present invention, and the present invention is not limited to these. The following content can be appropriately adopted within the scope that does not impair the optical performance of the variable magnification optical system of the embodiment of the present application.

[0180] In the variable magnification optical system of this embodiment, the third lens group does not have to have an aperture stop. Furthermore, the position of the aperture stop in the variable magnification optical system of this embodiment is not limited to the position of the aperture stop S in the variable magnification optical system of each of the above examples. The aperture stop in the variable magnification optical system of this embodiment may be located between lenses in the third lens group.

[0181] The variable magnification optical system of this embodiment may have an optical member such as a filter between the lens surface closest to the image plane and the image plane.

[0182] The variable magnification optical system of this embodiment may have an image stabilization lens group that corrects image blur caused by camera shake by being moved so as to have a component in a direction perpendicular to the optical axis. The image stabilization lens group may be a lens group, or may be a partial lens group consisting of one or more lens components included in the lens group.

[0183] In the variable magnification optical system of this embodiment, the lens surface may be spherical or flat, or may be aspherical. A spherical or flat lens surface is preferred because it facilitates lens processing and assembly adjustment, and prevents degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, a spherical or flat lens surface is preferred because it minimizes degradation of imaging performance when the image plane is displaced.

[0184] In the case where the lens surface is aspherical, the aspherical surface may be formed by grinding glass or by glass molding using a mold having an aspherical shape, or may be formed on the surface of a resin bonded to the surface of the glass. In addition, in the variable magnification optical system of this embodiment, the lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0185] Next, a camera equipped with the variable magnification optical system of this embodiment will be described with reference to Fig. 13. Fig. 13 is a schematic diagram of a camera equipped with the variable magnification optical system of this embodiment.

[0186] The camera 1 is a so-called mirrorless camera with interchangeable lenses, which has the optical system according to the first embodiment as the photographic lens 2.

[0187] In camera 1, light from an object (subject) (not shown) is collected by photographing lens 2 and reaches image sensor 3. Image sensor 3 converts the light from the subject into image data. When the photographer presses a release button (not shown), the image data is stored in memory (not shown). In this way, the photographer can photograph the subject using camera 1.

[0188] Here, the variable magnification optical system of the first embodiment mounted on the camera 1 as the photographic lens 2 is a variable magnification optical system with good optical performance. Therefore, the camera 1 can achieve good optical performance. Note that even if a camera is constructed that mounts the variable magnification optical system of the second to sixth embodiments as the photographic lens 2, the same effects as those of the camera 1 can be achieved.

[0189] Finally, a method for manufacturing the variable magnification optical system of this embodiment will be outlined with reference to FIG.

[0190] 14 is a flowchart outlining the manufacturing method of the variable magnification optical system of this embodiment. The manufacturing method of the variable magnification optical system of this embodiment shown in FIG. 14 includes the following steps S11 to S13.

[0191] Step S11: Prepare the first lens group, the second lens group, the third lens group, and the subsequent lens group.

[0192] Step S12: When the magnification is changed, the first lens group and the third lens group are fixed relative to the image plane, and the interval between each of the adjacent lens groups is changed.

[0193] Step S13: The variable magnification optical system is made to satisfy the following condition: (1) 0.24<(TL / f1) / (ft / fw)<0.55, where TL is the distance from the lens surface closest to the object to the image plane, f1 is the focal length of the first lens group, ft is the focal length of the variable magnification optical system in the telephoto end state, and fw is the focal length of the variable magnification optical system in the wide-angle end state.

[0194] According to the manufacturing method of the variable magnification optical system of this embodiment, an optical system having good imaging performance can be manufactured.

[0195] It should be understood that those skilled in the art can make various changes, substitutions, and alterations thereto without departing from the spirit and scope of the present disclosure.

[0196] S: aperture stop I: image plane 1: camera 2: photographing lens 3: image sensor

Claims

1. the first lens group having a positive refractive power, the second lens group having a negative refractive power, the third lens group having a positive refractive power, and a subsequent lens group having a plurality of lens groups, During magnification change, the first lens group and the third lens group are fixed with respect to an image plane, and the intervals between adjacent lens groups change, A variable magnification optical system that satisfies the following condition: 0.24 < (TL / f1) / (ft / fw) < 0.55 however, TL: Distance from the lens surface closest to the object to the image plane f1: focal length of the first lens group ft: focal length of the variable magnification optical system in the telephoto end state fw: focal length of the variable magnification optical system in the wide-angle end state

2. 2. The variable magnification optical system according to claim 1, which satisfies the following condition: 3.00 < f1 / (-f2) < 5.80 however, f2: focal length of the second lens group

3. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.45 < f1 / f3 < 6.00 however, f3: focal length of the third lens group

4. 3. The variable magnification optical system according to claim 1, wherein the subsequent lens group includes a focusing lens group that has negative refractive power and moves during focusing, and the following condition is satisfied: 0.30 < f2 / fF < 1.00 however, f2: focal length of the second lens group fF: focal length of the focusing lens group

5. 3. The variable magnification optical system according to claim 1, wherein the final lens group, which is disposed closest to the image surface side among the subsequent lens groups, is fixed with respect to the image surface during magnification variation.

6. the subsequent lens group includes a focusing lens group that has negative refractive power and moves during focusing, and a final lens group that is disposed closest to the image surface, 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 2.00 < |fR| / (-fF) < 100.00 however, fR: focal length of the final lens group fF: focal length of the focusing lens group

7. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.15 < BFw / fw < 0.95 however, BFw: Back focus of the variable magnification optical system when focused on infinity in the wide-angle end state

8. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.08 < BFt / ft < 0.24 however, BFt: back focus of the variable magnification optical system when focused on infinity in the telephoto end state

9. 3. The variable magnification optical system according to claim 1, wherein the subsequent lens group includes at least one lens group having a positive refractive power, and the following condition is satisfied: 1<n<1 / n+1 / n. 0.70 < f1 / fRP < 3.40 however, fRP: focal length of the lens group having the strongest positive refractive power among the lens groups having positive refractive power included in the subsequent lens group

10. 3. The variable magnification optical system according to claim 1, wherein the following condition is satisfied: 0.50 < Gw / Gt < 1.50 however, Gw: the distance from the lens surface of the variable magnification optical system closest to the object side to the center of gravity of the variable magnification optical system in the wide-angle end state Gt: the distance from the lens surface closest to the object side of the variable magnification optical system in the telephoto end state to the center of gravity of the variable magnification optical system

11. 3. An optical instrument comprising the variable magnification optical system according to claim 1.

12. 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 a plurality of lens groups; During magnification change, the first lens group and the third lens group are fixed with respect to an image plane, and the intervals between adjacent lens groups change, A manufacturing method for a variable magnification optical system configured to satisfy the following conditional expression: 0.24 < (TL / f1) / (ft / fw) < 0.55 however, TL: Distance from the lens surface closest to the object to the image plane f1: focal length of the first lens group ft: focal length of the variable magnification optical system in the telephoto end state fw: focal length of the variable magnification optical system in the wide-angle end state