Zoom optical system and image capturing device

Abstract

To provide a zoom optical system which has a wide angle of view, is reduced in size, and maintains good optical performance, and to provide an image capturing device equipped with the same.SOLUTION: A zoom optical system provided herein is a zoom lens comprising a front group, an intermediate group, and a rear group arranged in order from the object side. The front group consists of one lens group with negative refractive power configured to move while zooming. The intermediate group has just one lens group having positive refractive power as a lens group. The rear group consists of three or less lens groups. An aperture stop is disposed between a most image-side lens surface of the front group and a most object-side lens surface of the rear group. The front group comprises at least three negative lenses and at least one positive lens. A negative meniscus lens having a convex object-side surface is located on the most object side in the front group. The zoom optical system satisfies predetermined conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology of the present disclosure relates to a variable magnification optical system and an imaging apparatus. [Background technology]

[0002] Conventionally, the following Patent Documents 1 and 2 are known as variable magnification optical systems that can be used in imaging devices such as digital cameras. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-148949 [Patent Document 2] Patent Publication No. 2021-076829 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for variable magnification optical systems that have a wide angle of view, are compact, and maintain good optical performance, and the level of these requirements is increasing year by year.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a variable magnification optical system that has a wide angle of view, is compact, and maintains good optical performance, and an imaging device that is equipped with this variable magnification optical system. [Means for solving the problem]

[0006] A first aspect of the present disclosure is a variable magnification optical system comprising, in order from the object side to the image side, a front group, a middle group, and a rear group, wherein the front group consists of two or less lens groups and has negative refractive power overall throughout the entire range of magnification variation, the middle group includes only one lens group having positive refractive power as a lens group, and the rear group consists of three or less lens groups, an aperture stop is disposed between the lens surface of the front group closest to the image side and the lens surface of the rear group closest to the object side, and the spacing between the front group and the middle group changes during magnification variation, and when the front group consists of two lens groups, the spacing between adjacent lens groups in the front group changes during magnification variation, and when the rear group consists of multiple lens groups, the spacing between adjacent lens groups in the rear group changes during magnification variation. the front group includes at least three negative lens elements and at least one positive lens element, and a first lens element having negative refractive power and a meniscus shape with its convex surface facing the object is disposed closest to the object side of the front group; when the lens is focused on an object at infinity at the wide-angle end, the sum of the distance on the optical axis from the lens surface in the front group closest to the object side to the lens surface in the rear group closest to the image side and the back focus in terms of the air-equivalent distance of the entire system is TLw; the focal length of the entire system when focused on an object at infinity at the wide-angle end is fw; the focal length of the entire system when focused on an object at infinity at the telephoto end is ft; and the maximum half angle of view when focused on an object at infinity at the telephoto end is ωt. 3.8 <TLw / (ft×tanωt)<5.2 (1) 1<(fw×TLw) / ft 2 <2 (2) The conditional expressions (1) and (2) are satisfied.

[0007] In the second aspect of the present disclosure, when the maximum F-number in a state in which an object at infinity is focused at the telephoto end in the first aspect is FNot, 1.5 <FNot / (ft / fw)<3 (3) This variable magnification optical system satisfies conditional expression (3) below.

[0008] A third aspect of the present disclosure is the first or second aspect, where fFw is the focal length of the front group and fM is the focal length of the middle group when focused on an object at infinity at the wide-angle end, and 0.1<(-fFw) / fM<1.6 (4) This variable magnification optical system satisfies conditional expression (4) expressed as follows:

[0009] A fourth aspect of the present disclosure is any one of the first to third aspects, wherein, when the focal length of the front group at the wide-angle end when focused on an object at infinity is fFw, 0.6<(-fFw) / (fw×ft) 1 / 2 <1.3 (5) This variable magnification optical system satisfies conditional expression (5) expressed as follows:

[0010] A fifth aspect of the present disclosure is any one of the first to fourth aspects, wherein, when the focal length of the middle group is fM, 0.65 <fM / (fw×ft) 1 / 2 <3.7 (6) This variable magnification optical system satisfies conditional expression (6) expressed as follows:

[0011] A sixth aspect of the present disclosure is any one of the first to fifth aspects, wherein, when the focal length of the first lens is fL1 and the focal length of the front group when focused on an object at infinity at the wide-angle end is fFw, 1 <fL1 / fFw<3.5 (7) This variable magnification optical system satisfies conditional expression (7) below.

[0012] A seventh aspect of the present disclosure is any one of the first to sixth aspects, wherein, when the focal length of the front group when focused on an object at infinity at the wide-angle end is fFw and the maximum F-number when focused on an object at infinity at the telephoto end is FNot, 1.8<(-fFw) / (ft / FNot)<4 (8) This variable magnification optical system satisfies conditional expression (8) below.

[0013] An eighth aspect of the present disclosure is any one of the first to seventh aspects, wherein, when the center thickness of the first lens is D1 and the maximum aperture F-number in a state where the lens is focused on an object at infinity at the telephoto end is FNot, 0.08 <D1 / (ft / FNot)<0.42 (9) This variable magnification optical system satisfies conditional expression (9) below.

[0014] A ninth aspect of the present disclosure is any one of the first to eighth aspects, wherein, when the maximum half angle of view in a state in which an object at infinity is focused at the wide-angle end is ωw and the maximum open F-number in a state in which an object at infinity is focused at the wide-angle end is FNow, 0.3 <tanωw / FNow<0.47 (10) This variable magnification optical system satisfies conditional expression (10) expressed as follows:

[0015] A tenth aspect of the present disclosure is any one of the first to ninth aspects, wherein, when the lateral magnification of the middle group when focused on an object at infinity at the wide-angle end is βMw and the lateral magnification of the middle group when focused on an object at infinity at the telephoto end is βMt, -4<βMt / βMw<3.5 (11) This variable magnification optical system satisfies conditional expression (11) below.

[0016] An eleventh aspect of the present disclosure is any one of the first to tenth aspects, wherein, when the focal length of the rear group at the wide-angle end when focused on an object at infinity is fRw, 0.15<(fw×ft) 1 / 2 / |fRw|<1.1 (12) This variable magnification optical system satisfies conditional expression (12) expressed as follows:

[0017] A twelfth aspect of the present disclosure is any one of the first to eleventh aspects, wherein, when the lateral magnification of the lens unit closest to the image side in the rear group in a state where the lens is focused on an object at infinity at the wide-angle end is βRrw, -2<βRrw<3 (13) This variable magnification optical system satisfies conditional expression (13) below.

[0018] A thirteenth aspect of the present disclosure is any one of the first to twelfth aspects, wherein, when the distance on the optical axis from the lens surface of the front group closest to the object to the aperture stop when focused on an object at infinity at the wide-angle end is DDFSTw, and the focal length of the front group when focused on an object at infinity at the wide-angle end is fFw, 1.4 <DDFSTw / |fFw|<4 (14) This variable magnification optical system satisfies conditional expression (14) expressed as follows:

[0019] A fourteenth aspect of the present disclosure is any one of the first to thirteenth aspects, wherein, when the distance on the optical axis from the lens surface of the front group closest to the object to the paraxial entrance pupil position when focused on an object at infinity at the wide-angle end is Enpw, and the maximum half angle of view when focused on an object at infinity at the wide-angle end is ωw, 1.9 <Enpw / {(fw×tanωw)×log(ft / fw)}<3.8 (15) This variable magnification optical system satisfies conditional expression (15) below.

[0020] A fifteenth aspect of the present disclosure is any one of the first to fourteenth aspects, wherein, when the distance on the optical axis from the lens surface of the front group closest to the object to the aperture stop when focused on an object at infinity at the wide-angle end is DDFSTw, and the maximum half angle of view when focused on an object at infinity at the wide-angle end is ωw, 5 <DDFSTw / {(fw×tanωw)×log(ft / fw)}<10 (16) This variable magnification optical system satisfies conditional expression (16) expressed as follows:

[0021] A sixteenth aspect of the present disclosure is any one of the first to fifteenth aspects, wherein, when the distance on the optical axis from the lens surface of the front group closest to the object to the paraxial entrance pupil position in a state in which the lens is focused on an object at infinity at the wide-angle end is Enpw, 0.5 <Enpw / (fw×ft) 1 / 2 <1.1 (17) This variable magnification optical system satisfies conditional expression (17) below.

[0022] A seventeenth aspect of the present disclosure is any one of the first to sixteenth aspects, wherein, when the distance on the optical axis from the lens surface of the front group closest to the object to the aperture stop in a state in which the lens is focused on an object at infinity at the wide-angle end is DDFSTw, 0.3 <DDFSTw / TLw<0.7 (18) This variable magnification optical system satisfies conditional expression (18) below.

[0023] An eighteenth aspect of the present disclosure is any one of the first to seventeenth aspects, wherein, when a back focus in an air-equivalent distance of the entire system at the wide-angle end in a state where the lens is focused on an object at infinity is Bfw, 0.08 <Bfw / TLw<0.27 (19) This variable magnification optical system satisfies conditional expression (19) below.

[0024] A 19th aspect of the present disclosure is any one of the first to eighteenth aspects, wherein, when focused on an object at infinity at the wide-angle end, the sum of the distance on the optical axis from the paraxial exit pupil position to the lens surface in the rear group closest to the image side and the back focus in air equivalent distance of the entire system is defined as Expw: 0.28 <fw / Expw<0.65 (20) This variable magnification optical system satisfies conditional expression (20) below.

[0025] A twentieth aspect of the present disclosure is any one of the first to nineteenth aspects, wherein, when the radius of curvature of the object-side surface of the first lens is Rf and the radius of curvature of the image-side surface of the first lens is Rr, 1.5<(Rf+Rr) / (Rf-Rr)<4.2 (21) This variable magnification optical system satisfies conditional expression (21) expressed as follows:

[0026] A twenty-first aspect of the present disclosure is any one of the first to twentieth aspects, wherein, when the average value of the Abbe numbers of all the positive lenses in the rear group based on the d-line is νRpave, 40<νRpave<90 (22) This variable magnification optical system satisfies conditional expression (22) below.

[0027] A 22nd aspect of the present disclosure, in any one of the first to 21st aspects, is such that DMwt denotes the difference in the optical axis direction between the position of the middle group when focused on an object at infinity at the wide-angle end and the position of the middle group when focused on an object at infinity at the telephoto end, the sign of DMwt is positive if the position of the middle group when focused on an object at infinity at the telephoto end is closer to the image than the position of the middle group when focused on an object at infinity at the wide-angle end, and negative if the position of the middle group when focused on an object at infinity at the telephoto end is closer to the object than the position of the middle group when focused on an object at infinity at the wide-angle end, and when the unit of DMwt is millimeters, -0.2<(ft / fw) / DMwt<-0.04 (23) This variable magnification optical system satisfies conditional expression (23) expressed as follows:

[0028] A 23rd aspect of the present disclosure is any one of the first to 22nd aspects, wherein, when the refractive index of the first lens at the d-line is NL1 and the refractive index of the second negative lens from the object side among the negative lenses in the front group is NLn2, 1.58<(NL1+NLn2) / 2<2.2 (24) This variable magnification optical system satisfies conditional expression (24) expressed as follows:

[0029] A 24th aspect of the present disclosure is any one of the first to 23rd aspects, wherein the image-side surface of the lens having the strongest positive refractive power in the rear group is configured to be a convex surface, and where the focal length of the lens having the strongest positive refractive power in the rear group is fRLp and the focal length of the rear group when focused on an object at infinity at the wide-angle end is fRw, then: -10 <fRw / fRLp<5 (25) This variable magnification optical system satisfies conditional expression (25) expressed as follows:

[0030] A twenty-fifth aspect of the present disclosure is a variable power optical system according to the twenty-fourth aspect, wherein the lens having the strongest positive refractive power in the rear group is a biconvex lens.

[0031] A 26th aspect of the present disclosure is any one of the first to 25th aspects, wherein, when the effective diameter of the lens surface of the front group closest to the object is EDf and the effective diameter of the lens surface of the rear group closest to the image is EDr, 1.1 <EDf / EDr<2.1 (26) This variable magnification optical system satisfies conditional expression (26) expressed as follows:

[0032] A 27th aspect of the present disclosure is any one of the first to 26th aspects, wherein, when the effective diameter of the lens surface of the front group closest to the object side is defined as EDf, 0.2 <EDf / TLw<0.45 (27) This variable magnification optical system satisfies conditional expression (27) below.

[0033] A 28th aspect of the present disclosure is any one of the first to 27th aspects, wherein the rear group includes a focusing group that moves along the optical axis during focusing, and the focusing group is a variable magnification optical system consisting of two or less lenses.

[0034] A 29th aspect of the present disclosure is the 28th aspect, wherein the focusing group is a variable magnification optical system made up of one negative lens and one positive lens.

[0035] A thirtieth aspect of the present disclosure is the variable magnification optical system according to the twenty-ninth aspect, wherein the focusing group is a cemented lens formed by cementing one negative lens and one positive lens together.

[0036] A thirty-first aspect of the present disclosure is the twenty-eighth aspect, wherein the focusing group is a variable magnification optical system made up of one single lens.

[0037] A 32nd aspect of the present disclosure is a variable magnification optical system in any one of the 1st to 28th aspects, which includes only one focusing group that moves along the optical axis during focusing, and the focusing group is disposed within the rear group.

[0038] A thirty-third aspect of the present disclosure is a variable magnification optical system in any one of the first to twenty-eighth aspects, wherein the front group is made up of one lens group that moves during magnification variation.

[0039] A 34th aspect of the present disclosure is a variable magnification optical system that is a zoom lens in any one of the first to twenty-eighth aspects, wherein, during magnification variation, the lens group closest to the object in the front group is fixed relative to the image plane.

[0040] A 35th aspect of the present disclosure is a variable magnification optical system according to any one of the first to twenty-eighth aspects, which includes at least two cemented lenses, each cemented with one positive lens and one negative lens, located on the image side of the front group.

[0041] A 36th aspect of the present disclosure is a variable magnification optical system in which, in any one of the first to twenty-eighth aspects, at least one of the middle group and the rear group includes a composite aspherical lens in which a resin having an aspherical air-contacting surface is formed on the spherical surface of a glass lens.

[0042] A thirty-seventh aspect of the present disclosure is any one of the first to twenty-eighth aspects, wherein, when the Abbe number based on the d-line of the third negative lens from the object side among the negative lenses in the front group is vLn3, 50<νLn3<95 (28) This variable magnification optical system satisfies conditional expression (28) below.

[0043] A thirty-eighth aspect of the present disclosure is any one of the first to twenty-eighth aspects, wherein the lens group closest to the object side in the rear group is a variable magnification optical system having positive refractive power.

[0044] A thirty-ninth aspect of the present disclosure is a variable magnification optical system according to the thirty-eighth aspect, wherein the rear group has positive refractive power and is made up of one lens group that moves during magnification variation.

[0045] A fortieth aspect of the present disclosure is a variable magnification optical system according to the thirty-ninth aspect, wherein the front group is made up of one lens group that moves during magnification variation.

[0046] A forty-first aspect of the present disclosure is a variable magnification optical system according to the thirty-ninth or fortieth aspect, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with negative refractive power and a convex surface facing the object side, a third lens having negative refractive power and a concave surface facing the image side, and a fourth lens having positive refractive power and a convex surface facing the object side.

[0047] A forty-second aspect of the present disclosure is a variable magnification optical system in which, in the forty-first aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0048] A 43rd aspect of the present disclosure is the 38th aspect, wherein the rear group is a variable magnification optical system consisting of, in order from the object side to the image side, a lens group having positive refractive power, a lens group having negative refractive power, and a lens group having negative refractive power.

[0049] A forty-fourth aspect of the present disclosure is the variable magnification optical system according to the forty-third aspect, in which all of the lens groups in the rear group move when varying magnification.

[0050] A forty-fifth aspect of the present disclosure is the variable magnification optical system according to the forty-third or forty-fourth aspect, wherein the front group is made up of one lens group that moves during magnification variation.

[0051] A 46th aspect of the present disclosure is a variable magnification optical system in any one of the 43rd to 45th aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with a convex surface facing the object side and negative refractive power, a third lens having a concave surface facing the image side and negative refractive power, and a fourth lens having a convex surface facing the object side and positive refractive power.

[0052] A 47th aspect of the present disclosure is a variable magnification optical system in which, in the 46th aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0053] A 48th aspect of the present disclosure is any one of the 43rd to 47th aspects, including a focusing group that moves along the optical axis during focusing, and the focusing group is a variable magnification optical system consisting of one single lens.

[0054] A forty-ninth aspect of the present disclosure is the thirty-eighth aspect, wherein the rear group is a variable magnification optical system consisting of, in order from the object side to the image side, a lens group having positive refractive power, a lens group having positive refractive power, and a lens group having negative refractive power.

[0055] A fiftieth aspect of the present disclosure is the variable magnification optical system of the forty-ninth aspect, in which all of the lens groups in the rear group move when varying magnification.

[0056] A fifty-first aspect of the present disclosure is the variable magnification optical system according to the forty-ninth or fiftieth aspect, wherein the front group is made up of one lens group that moves during magnification variation.

[0057] A 52nd aspect of the present disclosure is a variable magnification optical system in any one of the 49th to 51st aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with a convex surface facing the object side and negative refractive power, a third lens having a concave surface facing the image side and negative refractive power, and a fourth lens having a convex surface facing the object side and positive refractive power.

[0058] A 53rd aspect of the present disclosure is a variable magnification optical system in which, in the 52nd aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0059] A 54th aspect of the present disclosure is the 38th aspect, wherein the rear group is a variable magnification optical system consisting of, in order from the object side to the image side, a lens group having positive refractive power, a lens group having negative refractive power, and a lens group having positive refractive power.

[0060] A fifty-fifth aspect of the present disclosure is the variable magnification optical system of the fifty-fourth aspect, in which all of the lens groups in the rear group move when varying magnification.

[0061] A fifty-sixth aspect of the present disclosure is a variable magnification optical system according to the fifty-fourth aspect, wherein, during magnification variation, the lens group closest to the image side in the rear group is fixed with respect to the image plane.

[0062] A fifty-seventh aspect of the present disclosure is a variable magnification optical system according to any one of the fifty-fourth to fifty-sixth aspects, wherein the front group is made up of one lens group that moves during magnification variation.

[0063] A 58th aspect of the present disclosure is a variable magnification optical system in the 54th aspect, wherein the front group is composed of, in order from the object side to the image side, a lens group having negative refractive power and a lens group having positive refractive power.

[0064] A fifty-ninth aspect of the present disclosure is a variable magnification optical system that is a zoom lens in the fifty-eighth aspect, wherein, during magnification variation, the lens group closest to the object side in the front group is fixed relative to the image plane.

[0065] A 60th aspect of the present disclosure is a variable magnification optical system in any one of the 54th to 59th aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with a convex surface facing the object side and negative refractive power, a third lens having a concave surface facing the image side and negative refractive power, and a fourth lens having a convex surface facing the object side and positive refractive power.

[0066] A 61st aspect of the present disclosure is a variable magnification optical system in which, in the 60th aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0067] A 62nd aspect of the present disclosure is any one of the 54th to 61st aspects, wherein the rear group includes a focusing group that moves along the optical axis during focusing, and the focusing group is a variable magnification optical system consisting of two or less lenses.

[0068] A sixty-third aspect of the present disclosure is the sixty-second aspect, wherein the focusing group is a variable magnification optical system made up of one negative lens.

[0069] A 64th aspect of the present disclosure is a variable magnification optical system in the 38th aspect, wherein the rear group is composed of, in order from the object side to the image side, a lens group having positive refractive power and a lens group having negative refractive power.

[0070] A sixty-fifth aspect of the present disclosure is the variable magnification optical system of the sixty-fourth aspect, in which all of the lens groups in the rear group move when varying magnification.

[0071] A sixty-sixth aspect of the present disclosure is the sixty-fourth or sixty-fifth aspect, wherein the front group is a variable magnification optical system made up of one lens group that moves during magnification variation.

[0072] A 67th aspect of the present disclosure is a variable magnification optical system according to the 64th or 65th aspect, wherein the front group is composed of, in order from the object side to the image side, a lens group having negative refractive power and a lens group having positive refractive power.

[0073] A 68th aspect of the present disclosure is a variable magnification optical system that is a zoom lens in the 67th aspect, wherein, during magnification variation, the lens group closest to the object side in the front group is fixed relative to the image plane.

[0074] A 69th aspect of the present disclosure is a variable magnification optical system in any one of the 64th to 68th aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with negative refractive power and a convex surface facing the object side, a third lens having negative refractive power and a concave surface facing the image side, and a fourth lens having positive refractive power and a convex surface facing the object side.

[0075] A 70th aspect of the present disclosure is a variable magnification optical system in which, in the 69th aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0076] A 71st aspect of the present disclosure is any one of the 1st to 37th aspects, wherein the lens group closest to the object side in the rear group is a variable magnification optical system having negative refractive power.

[0077] A 72nd aspect of the present disclosure is a variable magnification optical system in the 71st aspect, wherein the rear group is composed of, in order from the object side to the image side, a lens group having negative refractive power and a lens group having positive refractive power.

[0078] A seventy-third aspect of the present disclosure is the variable magnification optical system of the seventy-second aspect, in which all lens groups in the rear group move during magnification variation.

[0079] A seventy-fourth aspect of the present disclosure is the variable magnification optical system according to the seventy-second or seventy-third aspect, wherein the front group is made up of one lens group that moves during magnification variation.

[0080] A 75th aspect of the present disclosure is a variable magnification optical system in any one of the 72nd to 74th aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with a convex surface facing the object side and negative refractive power, a third lens having a concave surface facing the image side and negative refractive power, and a fourth lens having a convex surface facing the object side and positive refractive power.

[0081] A 76th aspect of the present disclosure is a variable magnification optical system in which, in the 75th aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0082] A 77th aspect of the present disclosure is any one of the 72nd to 76th aspects, and includes a focusing group that moves along the optical axis during focusing, and the focusing group is a variable magnification optical system composed of a cemented lens consisting of one positive lens and one negative lens.

[0083] A 78th aspect of the present disclosure is a variable magnification optical system in which, in the 71st aspect, the rear group is composed of, in order from the object side to the image side, a lens group having negative refractive power and a lens group having negative refractive power.

[0084] A seventy-ninth aspect of the present disclosure is the variable magnification optical system of the seventy-eighth aspect, in which all of the lens groups in the rear group move when varying magnification.

[0085] An eightieth aspect of the present disclosure is the variable magnification optical system according to the seventy-eighth or seventy-ninth aspect, wherein the front group is made up of one lens group that moves during magnification variation.

[0086] An 81st aspect of the present disclosure is a variable magnification optical system in any one of the 78th to 80th aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with negative refractive power and a convex surface facing the object side, a third lens having negative refractive power and a concave surface facing the image side, and a fourth lens having positive refractive power and a convex surface facing the object side.

[0087] An 82nd aspect of the present disclosure is a variable magnification optical system in which, in the 81st aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0088] An 83rd aspect of the present disclosure is any one of the 78th to 82nd aspects, and includes a focusing group that moves along the optical axis during focusing, and the focusing group is a variable magnification optical system consisting of a cemented lens consisting of one positive lens and one negative lens.

[0089] An 84th aspect of the present disclosure is a variable magnification optical system in which, in the 71st aspect, the rear group is composed of, in order from the object side to the image side, a lens group having negative refractive power, a lens group having negative refractive power, and a lens group having positive refractive power.

[0090] An 85th aspect of the present disclosure is the variable magnification optical system according to the 84th aspect, in which all lens groups in the rear group move when varying magnification.

[0091] An 86th aspect of the present disclosure is the variable magnification optical system according to the 84th or 85th aspect, wherein the front group is made up of one lens group that moves during magnification variation.

[0092] An 87th aspect of the present disclosure is a variable magnification optical system in any one of the 84th to 86th aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with negative refractive power and a convex surface facing the object side, a third lens having negative refractive power and a concave surface facing the image side, and a fourth lens having positive refractive power and a convex surface facing the object side.

[0093] An 88th aspect of the present disclosure is a variable magnification optical system in which, in the 87th aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0094] An 89th aspect of the present disclosure is any one of the 84th to 88th aspects, and includes a focusing group that moves along the optical axis during focusing, and the focusing group is a variable magnification optical system consisting of a cemented lens consisting of one positive lens and one negative lens.

[0095] A 90th aspect of the present disclosure is a variable magnification optical system in which, in the 71st aspect, the rear group is composed of, in order from the object side to the image side, a lens group having negative refractive power, a lens group having positive refractive power, and a lens group having positive refractive power.

[0096] A ninety-first aspect of the present disclosure is the variable magnification optical system of the ninety-first aspect, in which all lens groups in the rear group move when varying magnification.

[0097] A ninety-second aspect of the present disclosure is the variable magnification optical system according to the ninety-first or ninety-first aspect, wherein the front group is made up of one lens group that moves during magnification variation.

[0098] A 93rd aspect of the present disclosure is a variable magnification optical system in any one of the 90th to 92nd aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with negative refractive power and a convex surface facing the object side, a third lens having negative refractive power and a concave surface facing the image side, and a fourth lens having positive refractive power and a convex surface facing the object side.

[0099] A 94th aspect of the present disclosure is a variable magnification optical system in which, in the 93rd aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0100] A 95th aspect of the present disclosure is any one of the 90th to 94th aspects, which includes a focusing group that moves along the optical axis during focusing, and the focusing group is a variable magnification optical system consisting of a cemented lens consisting of one positive lens and one negative lens.

[0101] A 96th aspect of the present disclosure is the 71st aspect, wherein the rear group is a variable magnification optical system consisting of, in order from the object side to the image side, a lens group having negative refractive power, a lens group having positive refractive power, and a lens group having negative refractive power.

[0102] A 97th aspect of the present disclosure is the variable magnification optical system of the 96th aspect, in which all lens groups in the rear group move when varying magnification.

[0103] A 98th aspect of the present disclosure is the variable magnification optical system according to the 96th or 97th aspect, wherein the front group is made up of one lens group that moves during magnification variation.

[0104] A 99th aspect of the present disclosure is a variable magnification optical system in any one of the 96th to 98th aspects, wherein the front group includes, in order from the object side to the image side, a first lens, a second lens having a meniscus shape with a convex surface facing the object side and negative refractive power, a third lens having a concave surface facing the image side and negative refractive power, and a fourth lens having a convex surface facing the object side and positive refractive power.

[0105] The 100th aspect of the present disclosure is a variable magnification optical system in which, in the 99th aspect, the first lens has spherical lens surfaces on the object side and the image side, and the second lens has aspherical lens surfaces on the object side and the image side.

[0106] A 101st aspect of the present disclosure is any one of the 96th to 100th aspects, which includes a focusing group that moves along the optical axis during focusing, and the focusing group is a variable magnification optical system consisting of a cemented lens made of one positive lens and one negative lens.

[0107] A 102nd aspect of the present disclosure is an imaging device including the variable magnification optical system according to any one of the first to 101st aspects.

[0108] In this specification, the terms "consisting of" and "consisting of" are intended to mean that, in addition to the listed components, other components may also be included, such as lenses that have substantially no refractive power, optical elements other than lenses, such as apertures, filters, and cover glasses, and mechanical parts, such as lens flanges, lens barrels, image sensors, and image stabilization mechanisms.

[0109] In this specification, "a lens group having positive refractive power" and "the lens group has positive refractive power" mean that the lens group as a whole has positive refractive power. Similarly, "a lens group having negative refractive power" and "the lens group has negative refractive power" mean that the lens group as a whole has negative refractive power. A "lens having positive refractive power" and a "positive lens" are synonymous. A "lens having negative refractive power" and a "negative lens" are synonymous. In this specification, the terms "lens group", "front group", "middle group", "rear group", and "focusing group" such as the "first lens group" are not limited to being configured with multiple lenses, but may be configured with only one lens.

[0110] Unless otherwise specified, the radius of curvature, sign of refractive power, and surface shape of lenses including aspherical surfaces are those in the paraxial region. The sign of the radius of curvature is positive for surfaces with a convex surface facing the object side, and negative for surfaces with a convex surface facing the image side.

[0111] In this specification, "total system" refers to a variable magnification optical system. The "focal length" used in the conditional expressions is the paraxial focal length. The "distance on the optical axis" used in the conditional expressions is considered to be a geometric length unless otherwise specified. The values ​​used in the conditional expressions are values ​​based on the d-line when focused on an object at infinity unless otherwise specified. The "d-line," "C-line," and "F-line" used in this specification are emission lines, with the d-line wavelength being 587.56 nm (nanometers), the C-line wavelength being 656.27 nm (nanometers), and the F-line wavelength being 486.13 nm (nanometers). [Effects of the Invention]

[0112] According to the present disclosure, it is possible to provide a variable magnification optical system that has a wide angle of view, is compact, and maintains good optical performance, and an imaging device that includes this variable magnification optical system. [Brief explanation of the drawings]

[0113] [Figure 1] 1A and 1B are diagrams showing a cross-sectional view of the configuration of a variable magnification optical system according to one embodiment and a movement direction thereof, which corresponds to the variable magnification optical system of Example 1. FIG. [Figure 2] 2 is a cross-sectional view of the configuration of the variable magnification optical system of FIG. 1 and a light beam. [Figure 3] FIG. 2 is a diagram for explaining symbols in each conditional expression. [Figure 4] FIG. 10 is a diagram for explaining an effective diameter. [Figure 5] 3A to 3C are diagrams showing various aberrations in the variable magnification optical system of Example 1. [Figure 6] 10A and 10B are cross-sectional views of the configuration of a variable magnification optical system according to a second embodiment and diagrams showing the direction of movement. [Figure 7] 10A to 10C are diagrams showing various aberrations in the variable magnification optical system of Example 2. [Figure 8] 10A and 10B are cross-sectional views of the configuration of a variable magnification optical system according to a third embodiment and diagrams showing the direction of movement. [Figure 9] 10A to 10C are diagrams showing various aberrations in the variable magnification optical system of Example 3. [Figure 10] 10A and 10B are cross-sectional views of the configuration of a variable magnification optical system according to a fourth embodiment and diagrams showing the direction of movement. [Figure 11]10A to 10C are diagrams showing various aberrations in the variable magnification optical system of Example 4. [Figure 12] 10A and 10B are cross-sectional views of the configuration of a variable magnification optical system according to a fifth embodiment and a diagram showing the direction of movement. [Figure 13] 10A to 10C are diagrams showing various aberrations in the variable magnification optical system of Example 5. [Figure 14] 13A and 13B are cross-sectional views of the configuration of a variable magnification optical system according to a sixth embodiment and a diagram showing the direction of movement. [Figure 15] 10A to 10C are diagrams showing various aberrations in the variable magnification optical system of Example 6. [Figure 16] 13A and 13B are cross-sectional views of the configuration of a variable magnification optical system according to a seventh embodiment and a diagram showing the direction of movement. [Figure 17] 10A to 10C are diagrams showing various aberrations in the variable magnification optical system of Example 7. [Figure 18] 13A and 13B are cross-sectional views of the configuration of a variable magnification optical system according to an eighth embodiment and a diagram showing the direction of movement. [Figure 19] 13A to 13C are diagrams showing various aberrations in the variable magnification optical system of Example 8. [Figure 20] 13A and 13B are diagrams showing a cross-sectional view of the configuration of a variable magnification optical system of Example 9 and a movement direction thereof. [Figure 21] 13A to 13C are diagrams showing various aberrations in the variable magnification optical system of Example 9. [Figure 22] 13A and 13B are cross-sectional views of the configuration of a variable magnification optical system according to a tenth embodiment and a diagram showing the direction of movement. [Figure 23] 13A to 13C are diagrams showing various aberrations in the variable magnification optical system of Example 10. [Figure 24] 13A and 13B are cross-sectional views of the configuration of a variable magnification optical system according to an eleventh embodiment and a diagram showing the direction of movement. [Figure 25] 13A to 13C are diagrams showing various aberrations in the variable magnification optical system of Example 11. [Figure 26] 13A and 13B are cross-sectional views of the configuration of a variable magnification optical system according to Example 12 and a diagram showing the direction of movement. [Figure 27] 13A to 13C are diagrams showing various aberrations in the variable magnification optical system of Example 12. [Figure 28] 13A and 13B are cross-sectional views of the configuration of a variable magnification optical system according to a thirteenth embodiment and a diagram showing the direction of movement. [Figure 29] 13A to 13C are diagrams showing various aberrations in the variable magnification optical system of Example 13. [Figure 30] 13A and 13B are cross-sectional views of the configuration of a variable magnification optical system according to Example 14 and a diagram showing the direction of movement. [Figure 31] 16A to 16C are diagrams showing various aberrations in the variable magnification optical system of Example 14. [Figure 32] 15A and 15B are cross-sectional views of the configuration of a variable magnification optical system according to a fifteenth embodiment and a diagram showing the direction of movement. [Figure 33] 20A to 20C are diagrams showing various aberrations in the variable magnification optical system of Example 15. [Figure 34] 20A and 20B are cross-sectional views of the configuration of a variable magnification optical system according to a sixteenth embodiment and a diagram showing the direction of movement. [Figure 35] 20A to 20C are diagrams showing various aberrations in the variable magnification optical system of Example 16. [Figure 36] 20A and 20B are cross-sectional views of the configuration of a variable magnification optical system according to Example 17 and a diagram showing the direction of movement. [Figure 37] 20A to 20C are diagrams showing various aberrations in the variable magnification optical system of Example 17. [Figure 38] 20A and 20B are cross-sectional views of the configuration of a variable magnification optical system according to Example 18 and a diagram showing the direction of movement. [Figure 39] 20A to 20C are diagrams showing various aberrations in the variable magnification optical system of Example 18. [Figure 40] 20A and 20B are cross-sectional views of the configuration of a variable magnification optical system according to Example 19 and a diagram showing the direction of movement. [Figure 41] 20A to 20C are diagrams showing various aberrations in the variable magnification optical system of Example 19. [Figure 42] 1 is a perspective view of the front side of an imaging device according to an embodiment. [Figure 43] FIG. 2 is a perspective view of the rear side of the imaging device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0114] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0115] FIG. 1 shows cross-sectional views of the configuration and schematic movement directions of a variable magnification optical system according to an embodiment of the present disclosure in each variable magnification state. FIG. 2 also shows cross-sectional views of the configuration and light beams in each variable magnification state of the variable magnification optical system of FIG. 1. In FIGS. 1 and 2, the upper row labeled "Wide" shows the state at the wide-angle end, the middle row labeled "Middle" shows the state at an intermediate focal length state, and the lower row labeled "Tele" shows the state at the telephoto end. Both of the views in FIGS. 1 and 2 show the state focused on an object at infinity. In this specification, an object at infinity in the optical axis direction from the lens surface closest to the object in the variable magnification optical system is referred to as an "infinite object."

[0116] In Fig. 2, the upper row shows an axial light beam wa and a light beam wb having a maximum half angle of view ωw, the middle row shows an axial light beam ma and a light beam mb having a maximum half angle of view ωm, and the lower row shows an axial light beam ta and a light beam tb having a maximum half angle of view ωt. The example shown in Figs. 1 and 2 corresponds to the variable magnification optical system of Example 1, which will be described later. In Figs. 1 and 2, the left side is the object side and the right side is the image side.

[0117] The variable magnification optical system of the present disclosure comprises, in order from the object side to the image side along the optical axis Z, a front group GF, a middle group GM, and a rear group GR. The front group GF comprises two or fewer lens groups and has negative refractive power overall throughout the entire range of magnification. The middle group GM includes only one lens group with positive refractive power. In other words, the middle group GM includes only one lens group. The rear group GR comprises three or fewer lens groups. An aperture stop St is located between the lens surface of the front group GF closest to the image and the lens surface of the rear group GR closest to the object.

[0118] In this specification, a "lens group" refers to a component of a variable magnification optical system, including at least one lens, separated by an air gap that changes during magnification. During magnification, each lens group is moved or fixed individually, and the spacing between lenses within each lens group does not change. In other words, in this specification, a lens group is defined as a group in which the spacing between adjacent groups changes during magnification, but the total spacing between adjacent lenses within the lens group does not change. Note that the "lens group" may also include components other than lenses that do not have refractive power, such as an aperture stop St.

[0119] When magnification is changed, the distance between the front group GF and the middle group GM changes, and the distance between the middle group GM and the rear group GR changes. If the front group GF consists of two lens groups, the distance between adjacent lens groups in the front group changes when magnification is changed. If the rear group GR consists of multiple lens groups, the distance between all of the adjacent lens groups in the rear group changes when magnification is changed.

[0120] By having the front group GF, which is closest to the object, have negative refractive power, it becomes easy to achieve a wide angle of view at the wide-angle end. By locating the middle group GM, which has positive refractive power, on the image side of the front group GF and the rear group GR on the image side of the middle group GM, it becomes easy to achieve a high-performance optical system while maintaining a compact size. By locating the aperture stop St between the lens surface of the front group GF closest to the image and the lens surface of the rear group GR closest to the object, it becomes possible to reduce the size of the stop unit, which also works to reduce the size of the entire lens system.

[0121] As an example, the variable magnification optical system in FIG. 1 is composed of, in order from the object side to the image side, a first lens group G1, a second lens group G2, and a third lens group G3. As an example, each lens group in FIG. 1 is configured as follows: The first lens group G1 is composed of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 is composed of three lenses, L21 to L23, in order from the object side to the image side, and an aperture stop St. The third lens group G3 is composed of five lenses, L31 to L35, in order from the object side to the image side. Note that the aperture stop St in FIG. 1 does not indicate its shape or size, but rather its position in the optical axis direction. This method of illustrating the aperture stop St is similar in other figures.

[0122] In the example of Figure 1, when changing magnification, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis Z while changing the spacing between adjacent lens groups. The diagonal arrows between the top and middle sections of Figure 1 roughly indicate the direction of movement of each lens group when changing magnification from the wide-angle end to the mid-focal length state. The diagonal arrows between the middle and bottom sections of Figure 1 roughly indicate the direction of movement of each lens group when changing magnification from the mid-focal length state to the telephoto end. In the example of Figure 1, the front group GF consists of the first lens group G1, the middle group GM consists of the second lens group G2, and the rear group GR consists of the third lens group G3.

[0123] Note that the example shown in FIG. 1 is just one example, and the variable magnification optical system of the present disclosure can be modified in various ways without departing from the spirit and scope of the technology of the present disclosure. For example, the front group GF may be configured to consist of one lens group, or two lens groups. The rear group GR may be configured to consist of one lens group, two lens groups, or three lens groups. Furthermore, the number of lenses included in each lens group may be different from that in the example of FIG. 1. Preferred and possible configurations of the variable magnification optical system of the present disclosure are described below.

[0124] The front group GF may be configured to consist of a single lens group that moves during zooming. Configuring the front group GF to move during zooming is advantageous for achieving a high zoom ratio.

[0125] Alternatively, the front group GF may be configured to consist of, in order from the object side to the image side, a lens group with negative refractive power and a lens group with positive refractive power, which is advantageous for achieving a high zoom ratio while suppressing aberration fluctuations during zooming.

[0126] The variable magnification optical system of the present disclosure may be a zoom lens or a varifocal lens. When the variable magnification optical system is a zoom lens, the lens group closest to the object in the front group GF may be configured to be fixed relative to the image plane Sim during magnification. In this case, the number of lens groups that move during magnification can be reduced, making the system less susceptible to decentration and simplifying the configuration of the lens frame. Furthermore, since the overall length of the optical system remains constant during magnification, fluctuations in the center of gravity of the optical system during magnification can be reduced, thereby improving convenience during photography.

[0127] The front group GF preferably includes a first lens element closest to the object, which is a meniscus lens element with a convex surface facing the object and has negative refractive power. The front group GF also preferably includes at least three negative lenses, including the first lens element, and at least one positive lens element. By making the first lens element, the negative lens element closest to the object, a meniscus lens element with a convex surface facing the object, the refraction angle of the light beam incident on the first lens element can be reduced, which is advantageous for correcting field curvature and other issues. By including three or more negative lenses in the front group GF, the negative refractive power of the front group GF can be strengthened, which is advantageous for achieving a wider angle of view at the wide-angle end. By including at least one positive lens element in the front group GF, the diameter of the light beam incident on the middle group GM from the front group GF can be reduced, which is advantageous for compactness. In the example shown in FIG. 1, lens L11 corresponds to the first lens element.

[0128] More specifically, the front group GF preferably includes, in order from the object side to the image side, the first lens, a second lens having a meniscus shape and negative refractive power with a convex surface facing the object side, a third lens having negative refractive power with a concave surface facing the image side, and a fourth lens having positive refractive power with a convex surface facing the object side. This configuration is advantageous for correcting field curvature and the like, widening the angle of view at the wide-angle end, and reducing size. In the example of FIG. 1, lenses L12, L13, and L14 correspond to the second lens, the third lens, and the fourth lens, respectively. The front group GF may be configured to include four lenses, the first lens to the fourth lens. Alternatively, the front group GF may be configured to include a total of five lenses, including the first lens to the fourth lens.

[0129] In this specification, the phrase "including, in order from the object side to the image side," is intended to mean including components in order, both continuously and discontinuously. For example, "including, in order from the object side to the image side, A and B" may mean including A and B arranged continuously, or A and B arranged discontinuously with something else interposed between them.

[0130] When the front group GF includes the first lens and the second lens, the first lens may be configured so that its object-side and image-side lens surfaces are spherical, and the second lens may be configured so that its object-side and image-side lens surfaces are aspherical. In optical systems with wide angles of view, the first lens, which is closest to the object and tends to have a large diameter, is made spherical, thereby reducing manufacturing costs. Making the second lens an aspherical lens is advantageous for reducing the size of the optical system while suppressing various aberrations at the wide-angle end.

[0131] The variable magnification optical system of the present disclosure is preferably configured to include at least two cemented lenses, each composed of one positive lens and one negative lens, located closer to the image side than the front group GF, which is advantageous for suppressing lateral chromatic aberration and axial chromatic aberration throughout the entire range of magnification.

[0132] It is preferable to configure the lens group in the middle group so that it moves when changing magnification, which is advantageous for improving performance because it makes it easier to suppress aberration fluctuations when changing magnification.

[0133] The aperture stop St may be located closest to the image in the middle group GM, or may be located between two lens surfaces in the middle group, or may be located closest to the object in the rear group GR. The aperture stop St may be configured to move integrally with an adjacent lens when changing magnification, or may be configured to move along a trajectory different from that of any of the lenses when changing magnification.

[0134] At least one of the middle group GM and the rear group GR may be configured to include a compound aspherical lens in which a resin having an aspherical air-contact surface is formed on the spherical surface of a glass lens. In this case, an aspherical surface can be added to the lens surface while suppressing manufacturing costs, thereby achieving cost reduction and excellent correction of various aberrations. Note that in this disclosure, a compound aspherical lens formed of the resin and the glass lens is not considered a cemented lens in which two lenses are cemented together, but is treated as a single lens.

[0135] The lens unit closest to the object side of the rear group GR may be configured to have positive refractive power, which is advantageous for suppressing spherical aberration, particularly at the telephoto end.

[0136] Alternatively, the lens unit closest to the object side of the rear group GR may be configured to have negative refractive power, which is advantageous for suppressing distortion, particularly at the wide-angle end.

[0137] The rear group GR may be configured to consist of a single lens group that has positive refractive power and moves during zooming. In this case, the entire rear group moves as a unit during zooming, simplifying the mechanism for operating the lens groups during zooming. Furthermore, the positive refractive power of the rear group GR is advantageous for suppressing spherical aberration, particularly at the telephoto end.

[0138] Alternatively, the rear group GR may be configured to consist, in order from the object side to the image side, of a lens group having negative refractive power and a lens group having negative refractive power, which makes it easier to suppress fluctuations in distortion during zooming.

[0139] Alternatively, the rear group GR may be configured to include multiple lens groups, including both lens groups with positive refractive power and lens groups with negative refractive power, which makes it easier to suppress aberration fluctuations during zooming.

[0140] When the rear group GR is made up of two lens groups, it may be configured to consist, in order from the object side to the image side, of a lens group having positive refractive power and a lens group having negative refractive power, or it may be configured to consist, in order from the object side to the image side, of a lens group having negative refractive power and a lens group having positive refractive power.

[0141] When the rear group GR consists of three lens groups, it may be configured as follows. The rear group GR may be configured to consist, in order from the object side to the image side, of a lens group having positive refractive power, a lens group having negative refractive power, and a lens group having negative refractive power. The rear group GR may be configured to consist, in order from the object side to the image side, of a lens group having positive refractive power, a lens group having positive refractive power, and a lens group having negative refractive power. The rear group GR may be configured to consist, in order from the object side to the image side, of a lens group having positive refractive power, a lens group having negative refractive power, and a lens group having positive refractive power. The rear group GR may be configured to consist, in order from the object side to the image side, of a lens group having negative refractive power, a lens group having negative refractive power, and a lens group having positive refractive power. The rear group GR may be configured to consist, in order from the object side to the image side, of a lens group having negative refractive power, a lens group having positive refractive power, and a lens group having positive refractive power.The rear group GR may be configured, in order from the object side to the image side, of a lens group having negative refractive power, a lens group having positive refractive power, and a lens group having negative refractive power.

[0142] It is also possible to configure the rear lens group so that all of the lens units move during zooming, which is advantageous for achieving a high zoom ratio while suppressing aberration fluctuations during zooming.

[0143] Alternatively, the lens group closest to the image in the rear group GR may be configured to be fixed relative to the image plane Sim during zooming, which simplifies the mechanism for operating the lens groups during zooming.

[0144] The variable magnification optical system of the present disclosure preferably includes a focusing group that moves along the optical axis Z during focusing. In this specification, the group that moves along the optical axis Z during focusing is referred to as the "focusing group." Focusing is performed by the movement of the focusing group.

[0145] As an example, the focusing group in Figure 1 consists of two lenses, lens L31 and lens L32. The parentheses and left-pointing arrows below lens L31 and lens L32 in the upper part of Figure 1 indicate that the focusing group consists of lens L31 and lens L32, and that this focusing group moves toward the object when focusing from an object at infinity to a close object.

[0146] The focusing group is preferably included in the rear group GR. By locating the focusing group within the rear group, it becomes easier to make the diameter of the focusing group small, which makes it easier to control the focusing group.

[0147] The focusing group may be located closest to the object in the rear group GR. This facilitates miniaturization of the focusing group, which is advantageous for miniaturizing the entire lens system. Alternatively, if the rear group GR consists of three lens groups, the focusing group may be located within the rear group, the second lens group from the object side.

[0148] The focusing group preferably consists of two or fewer lenses. By limiting the number of lenses that make up the focusing group, the mechanism for controlling the focusing group can be simplified and quick focusing can be facilitated.

[0149] The focusing group may be configured to include one negative lens and one positive lens, which allows the negative and positive lenses in the focusing group to cancel out various aberrations, making it easier to suppress aberration fluctuations during focusing, and is advantageous for improving performance.

[0150] The focusing group may be configured as a cemented lens consisting of one negative lens and one positive lens. This configuration allows for a more compact lens than a non-cemented configuration. A compact focusing group allows for a simpler mechanism for controlling the focusing group and facilitates faster focusing.

[0151] The focusing group may be configured to consist of one single lens. A "single lens" is a single lens that is not cemented. When the focusing group consists of one single lens, it can be made even more compact than when the focusing group consists of two or more lenses. By making the focusing group smaller, the mechanism for controlling the focusing group can be simplified and quick focusing can be facilitated.

[0152] The focusing group may be configured to consist of one negative lens. This allows for even smaller size compared to when the focusing group consists of two or more lenses. A smaller focusing group simplifies the mechanism for controlling the focusing group and facilitates rapid focusing. Furthermore, by making the refractive power of the focusing group negative, it becomes easier to impart strong refractive power to the focusing group, which is advantageous for reducing the amount of movement of the focusing group during focusing.

[0153] The variable magnification optical system of the present disclosure preferably includes only one focusing group. In this case, the focusing mechanism can be simplified. When the variable magnification optical system includes only one focusing group, it is preferable that the focusing group be located within the rear group.

[0154] Below, we will describe preferred and possible configurations for the conditional expressions of the variable magnification optical system of the present disclosure. In the following explanation of the conditional expressions, to avoid redundant explanation, the same symbols are used for elements with the same definitions, and some redundant explanations of the symbols will be omitted. Also, to avoid redundant explanation, hereinafter, "the variable magnification optical system of the present disclosure" will also be simply referred to as "the variable magnification optical system."

[0155] It is preferable that a variable magnification optical system satisfy the following conditional expression (1). Here, TLw is the sum of the axial distance from the lens surface of the front group GF closest to the object to the lens surface of the rear group GR closest to the image when focused on an object at infinity at the wide-angle end, and the back focal length Bfw of the entire system in terms of air equivalent distance. ft is the focal length of the entire system when focused on an object at infinity at the telephoto end, and ωt is the maximum half angle of view when focused on an object at infinity at the telephoto end. TLw is the overall length when focused on an object at infinity at the wide-angle end. tan in conditional expression (1) is the tangent, and this notation is similar for the other conditional expressions. Ensuring that the corresponding value of conditional expression (1) does not fall below the lower limit is advantageous for suppressing various aberrations throughout the entire magnification range. Ensuring that the corresponding value of conditional expression (1) does not fall above the upper limit is advantageous for reducing the size of the entire optical system. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional expression (1-1), and it is even more preferable that the variable magnification optical system satisfies the following conditional expression (1-2). 3.8 <TLw / (ft×tanωt)<5.2 (1) 4 <TLw / (ft×tanωt)<5.1 (1-1) 4.2 <TLw / (ft×tanωt)<5.04 (1-2)

[0156] As an example, FIG. 3 shows the back focus Bfw and total length TLw of the variable magnification optical system of FIG. 1 when focused on an object at infinity at the wide-angle end. "Back focus" refers to the distance on the optical axis from the lens surface closest to the image in the variable magnification optical system to the image plane Sim. As in the example of FIG. 3, if no components are arranged between the lens surface closest to the image in the variable magnification optical system and the image plane Sim, the geometric length from the lens surface closest to the image in the variable magnification optical system to the image plane Sim is equal to the back focus Bfw in the air-equivalent distance. However, unlike the example of FIG. 3, if a component such as a filter or cover glass is arranged between the lens surface closest to the image in the variable magnification optical system and the image plane Sim, the geometric length from the lens surface closest to the image in the variable magnification optical system to the image plane Sim differs from the back focus Bfw in the air-equivalent distance. Therefore, the thickness of the component on the optical axis is converted into air to calculate the back focus Bfw.

[0157] If the focal length of the entire system when focused on an object at infinity at the wide-angle end is fw, it is preferable that the variable magnification optical system satisfy the following conditional expression (2). Ensuring that the corresponding value of conditional expression (2) does not fall below the lower limit is advantageous for suppressing various aberrations throughout the entire range of magnification. Ensuring that the corresponding value of conditional expression (2) does not fall above the upper limit is advantageous for reducing the size of the entire optical system or for obtaining a sufficient magnification ratio as a variable magnification optical system. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (2-1), and it is even more preferable that it satisfy the following conditional expression (2-2). 1<(fw×TLw) / ft 2 <2 (2) 1.1<(fw×TLw) / ft 2 <1.85 (2-1) 1.2<(fw×TLw) / ft 2 <1.75 (2-2)

[0158] If the maximum F-number when focused on an object at infinity at the telephoto end is FNot, it is preferable that the variable magnification optical system satisfy the following conditional expression (3). ft / fw in conditional expression (3) is the maximum variable magnification ratio. Ensuring that the corresponding value of conditional expression (3) does not fall below the lower limit is advantageous for reducing the size of the entire optical system, and is also advantageous for suppressing various aberrations, particularly at the telephoto end. Ensuring that the corresponding value of conditional expression (3) does not fall above the upper limit makes it easier to obtain sufficient brightness at the telephoto end. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (3-1), and even more preferable that it satisfy the following conditional expression (3-2). 1.5 <FNot / (ft / fw)<3 (3) 1.7 <FNot / (ft / fw)<2.9 (3-1) 1.9 <FNot / (ft / fw)<2.85 (3-2)

[0159] When the focal length of the front group GF when focused on an object at infinity at the wide-angle end is fFw and the focal length of the middle group GM is fM, it is preferable that the variable magnification optical system satisfy the following conditional expression (4): By ensuring that the corresponding value of conditional expression (4) is not below the lower limit, the refractive power of the middle group GM does not become too weak, which is advantageous for correcting spherical aberration, particularly on the telephoto side. By ensuring that the corresponding value of conditional expression (4) is not above the upper limit, the refractive power of the front group GF does not become too weak, which makes it easy to prevent the front group GF from becoming too large. Furthermore, if the front group GF moves during magnification, it makes it easy to reduce the amount of movement of the front group GF during magnification. To obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (4-1), and it is even more preferable that it satisfy the following conditional expression (4-2). 0.1<(-fFw) / fM<1.6 (4) 0.2<(-fFw) / fM<1.5 (4-1) 0.25<(-fFw) / fM<1.45 (4-2)

[0160] It is preferable that the variable magnification optical system satisfy the following conditional expression (5). By ensuring that the corresponding value of conditional expression (5) is not below the lower limit, the refractive power of the front group GF does not become too strong, which is advantageous for suppressing aberration fluctuations during magnification. By ensuring that the corresponding value of conditional expression (5) is not above the upper limit, the refractive power of the front group GF does not become too weak, which makes it easy to prevent the front group GF from becoming too large, and also makes it easy to suppress the amount of movement of the front group GF during magnification, if the front group GF moves during magnification. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (5-1), and even more preferable that it satisfy the following conditional expression (5-2). 0.6<(-fFw) / (fw×ft) 1 / 2 <1.3 (5) 0.65<(-fFw) / (fw×ft) 1 / 2 <1.25 (5-1) 0.7<(-fFw) / (fw×ft) 1 / 2 <1.2 (5-2)

[0161] It is preferable that the variable magnification optical system satisfy the following conditional expression (6). By ensuring that the corresponding value of conditional expression (6) is not below the lower limit, the refractive power of the middle group GM does not become too strong, making it possible to suppress the curvature of field that occurs in the middle group GM, which is advantageous for correcting aberrations when varying magnification. By ensuring that the corresponding value of conditional expression (6) is not above the upper limit, the refractive power of the middle group GM does not become too weak, making it possible to suppress the amount of movement of the middle group GM when varying magnification, which is advantageous for shortening the overall length of the optical system. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (6-1), and it is even more preferable that it satisfy the following conditional expression (6-2). 0.65 <fM / (fw×ft) 1 / 2 <3.7 (6) 0.7 <fM / (fw×ft) 1 / 2 <3.6 (6-1) 0.75 <fM / (fw×ft) 1 / 2 <3.5 (6-2)

[0162] In a configuration in which the front group GF includes the first lens, where the focal length of the first lens is fL1, it is preferable that the variable magnification optical system satisfy the following conditional expression (7): By ensuring that the corresponding value of conditional expression (7) is not below the lower limit, the refractive power of the first lens does not become too strong, making it easy to suppress high-order aberrations at the telephoto end. Alternatively, by ensuring that the corresponding value of conditional expression (7) is not below the lower limit, the refractive power of the front group GF does not become too weak, making it easy to suppress an increase in the size of the front group GF, which is advantageous for downsizing the front group GF. In this specification, "high-order aberrations" refers to aberrations of the fifth order or higher. By ensuring that the corresponding value of conditional expression (7) is not above the upper limit, the refractive power of the front group GF does not become too strong, making it advantageous for suppressing aberration fluctuations during magnification. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (7-1), and even more preferable that it satisfy the following conditional expression (7-2). 1 <fL1 / fFw<3.5 (7) 1.1 <fL1 / fFw<3.2 (7-1) 1.2 <fL1 / fFw<3 (7-2)

[0163] If the maximum F-number when focused on an object at infinity at the telephoto end is FNot, it is preferable that the variable magnification optical system satisfy the following conditional expression (8). Ensuring that the corresponding value of conditional expression (8) does not become equal to or less than the lower limit is advantageous for improving performance. Ensuring that the corresponding value of conditional expression (8) does not become equal to or greater than the upper limit prevents the refractive power of the front group GF from becoming too weak, making it easier to prevent the front group GF from becoming large, which is advantageous for making the front group GF more compact. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (8-1), and even more preferable that it satisfy the following conditional expression (8-2). 1.8<(-fFw) / (ft / FNot)<4 (8) 2<(-fFw) / (ft / FNot)<3.2 (8-1) 2.2<(-fFw) / (ft / FNot)<2.9 (8-2)

[0164] In a configuration in which the front group GF includes the first lens described above, when the center thickness of the first lens is D1, it is preferable that the variable magnification optical system satisfy the following conditional expression (9). By ensuring that the corresponding value of conditional expression (9) is not below the lower limit, it becomes easy to ensure the mechanical strength of the first lens. By ensuring that the corresponding value of conditional expression (9) is not above the upper limit, it becomes advantageous for reducing the weight of the first lens. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (9-1), and it is even more preferable that it satisfy the following conditional expression (9-2). 0.08 <D1 / (ft / FNot)<0.42 (9) 0.09 <D1 / (ft / FNot)<0.41 (9-1) 0.1 <D1 / (ft / FNot)<0.4 (9-2)

[0165] If the maximum half angle of view when focused on an object at infinity at the wide-angle end is ωw and the maximum F-number when focused on an object at infinity at the wide-angle end is FNow, it is preferable that the variable magnification optical system satisfy the following conditional expression (10). By ensuring that the corresponding value of conditional expression (10) is not below the lower limit, it is easy to widen the angle of view at the wide-angle end while reducing the maximum F-number at the wide-angle end. By ensuring that the corresponding value of conditional expression (10) is not above the upper limit, it is easy to suppress an increase in the number of lenses and an increase in the size of the optical system while obtaining good optical performance. In order to obtain even better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (10-1), and it is even more preferable that it satisfy the following conditional expression (10-2). 0.3 <tanωw / FNow<0.47 (10) 0.31 <tanωw / FNow<0.45 (10-1) 0.32 <tanωw / FNow<0.43 (10-2)

[0166] If the lateral magnification of the middle group GM when focused on an object at infinity at the wide-angle end is βMw and the lateral magnification of the middle group GM when focused on an object at infinity at the telephoto end is βMt, it is preferable that the variable magnification optical system satisfy the following conditional expression (11). Ensuring that the corresponding value of conditional expression (11) is not below the lower limit is advantageous for achieving a high variable magnification ratio. Ensuring that the corresponding value of conditional expression (11) is not above the upper limit is advantageous for suppressing aberration fluctuations during magnification variation. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (11-1), and even more preferable that it satisfy the following conditional expression (11-2). -4<βMt / βMw<3.5 (11) -3.5<βMt / βMw<3 (11-1) -3<βMt / βMw<2.5 (11-2)

[0167] If the focal length of the rear group GR when focused on an object at infinity at the wide-angle end is fRw, it is preferable that the variable magnification optical system satisfy the following conditional expression (12). Ensuring that the corresponding value of conditional expression (12) is not below the lower limit is advantageous for suppressing various aberrations throughout the entire range of variable magnification. Ensuring that the corresponding value of conditional expression (12) is not above the upper limit is advantageous for suppressing the sensitivity of the rear group GR to errors. In order to obtain even better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (12-1), and even more preferable that it satisfy the following conditional expression (12-2). 0.15<(fw×ft) 1 / 2 / |fRw|<1.1 (12) 0.2<(fw×ft) 1 / 2 / |fRw|<0.9 (12-1) 0.25<(fw×ft) 1 / 2 / |fRw|<0.8 (12-2)

[0168] If the lateral magnification of the lens unit closest to the image side in the rear group GR when focused on an object at infinity at the wide-angle end is βRrw, it is preferable that the variable magnification optical system satisfy the following conditional expression (13). Ensuring that the corresponding value of conditional expression (13) is not below the lower limit is advantageous for achieving a high variable magnification ratio. Ensuring that the corresponding value of conditional expression (13) is not above the upper limit is advantageous for suppressing various aberrations throughout the entire variable magnification range. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (13-1), and even more preferable that it satisfy the following conditional expression (13-2). -2<βRrw<3 (13) -1<βRrw<2.75 (13-1) -0.5<βRrw<2.5 (13-2)

[0169] If the on-optical distance from the object-side lens surface of the front group GF to the aperture stop St when focused on an object at infinity at the wide-angle end is defined as DDFSTw, it is preferable that the variable-magnification optical system satisfy the following conditional expression (14): As an example, FIG. 3 shows the distance DDFSTw defined above for the variable-magnification optical system of FIG. 1. By ensuring that the value corresponding to conditional expression (14) is not below the lower limit, the distance from the object-side lens surface of the front group GF to the aperture stop St does not become too short, and the range of motion of the middle group GM does not become too narrow, which is advantageous for achieving a high variable-magnification ratio. Alternatively, by ensuring that the value corresponding to conditional expression (14) is not below the lower limit, the refractive power of the front group GF does not become too weak, which is advantageous for achieving both compactness and a high variable-magnification ratio. By ensuring that the value corresponding to conditional expression (14) does not exceed the upper limit, the distance from the lens surface of the front group GF closest to the object to the entrance pupil position on the wide-angle side does not become too long, so that the diameter of the front group GF can be kept from increasing, facilitating size reduction.Alternatively, by ensuring that the value corresponding to conditional expression (14) does not exceed the upper limit, the refractive power of the front group GF does not become too strong, which is advantageous for improving performance.In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (14-1), and it is even more preferable that it satisfy the following conditional expression (14-2). 1.4 <DDFSTw / |fFw|<4 (14) 1.5 <DDFSTw / |fFw|<3.75 (14-1) 1.6 <DDFSTw / |fFw|<3.5 (14-2)

[0170] It is preferable that a variable magnification optical system satisfy the following conditional expression (15): Here, Enpw is the distance on the optical axis from the lens surface of the front group GF closest to the object to the paraxial entrance pupil position Pen when focused on an object at infinity at the wide-angle end. As an example, FIG. 3 shows the paraxial entrance pupil position Pen and the distance Enpw defined above when the variable magnification optical system of FIG. 1 is focused on an object at infinity at the wide-angle end. In this specification, the sign of Enpw is negative if the paraxial entrance pupil position Pen is closer to the object than the lens surface of the front group GF closest to the object, and positive if the paraxial entrance pupil position Pen is closer to the image than the lens surface of the front group GF closest to the object. By ensuring that the corresponding value of conditional expression (15) is not below its lower limit, the distance from the lens surface of the front group GF closest to the object to the paraxial entrance pupil position Pen at the wide-angle end does not become too short, making it easier to suppress aberration fluctuations during magnification variation. By ensuring that the value corresponding to conditional expression (15) does not exceed its upper limit, the distance from the lens surface of the front group GF closest to the object to the paraxial entrance pupil position Pen on the wide-angle side does not become too long, so that the diameter of the front group GF can be kept from increasing, facilitating size reduction. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (15-1), and it is even more preferable that it satisfy the following conditional expression (15-2). 1.9 <Enpw / {(fw×tanωw)×log(ft / fw)}<3.8 (15) 2 <Enpw / {(fw×tanωw)×log(ft / fw)}<3.5 (15-1) 2.1 <Enpw / {(fw×tanωw)×log(ft / fw)}<3.2 (15-2)

[0171] It is preferable that the variable magnification optical system satisfy the following conditional expression (16): By ensuring that the corresponding value of conditional expression (16) is not below the lower limit, the distance from the lens surface of the front group GF closest to the object to the entrance pupil position at the wide-angle side does not become too short, making it easy to suppress aberration fluctuations during magnification variation. By ensuring that the corresponding value of conditional expression (16) is not above the upper limit, the distance from the lens surface of the front group GF closest to the object to the entrance pupil position at the wide-angle side does not become too long, making it possible to prevent the diameter of the front group GF from becoming too large, thereby facilitating size reduction. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (16-1), and it is even more preferable that the following conditional expression (16-2) is satisfied. 5 <DDFSTw / {(fw×tanωw)×log(ft / fw)}<10 (16) 5.5 <DDFSTw / {(fw×tanωw)×log(ft / fw)}<9 (16-1) 6 <DDFSTw / {(fw×tanωw)×log(ft / fw)}<8 (16-2)

[0172] It is preferable that the variable magnification optical system satisfy the following conditional expression (17): By ensuring that the corresponding value of conditional expression (17) is not below the lower limit, the distance from the lens surface of the front group GF closest to the object to the paraxial entrance pupil position Pen on the wide-angle side does not become too short, making it easy to suppress aberration fluctuations during magnification variation. By ensuring that the corresponding value of conditional expression (17) is not above the upper limit, the distance from the lens surface of the front group GF closest to the object to the paraxial entrance pupil position Pen on the wide-angle side does not become too long, making it possible to suppress an increase in the diameter of the front group GF, and thereby facilitating size reduction. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (17-1), and it is even more preferable that the following conditional expression (17-2) is satisfied. 0.5 <Enpw / (fw×ft) 1 / 2 <1.1 (17) 0.55 <Enpw / (fw×ft) 1 / 2 <1 (17-1) 0.6 <Enpw / (fw×ft) 1 / 2 <0.9 (17-2)

[0173] It is preferable that the variable magnification optical system satisfy the following conditional expression (18): By ensuring that the corresponding value of conditional expression (18) is not below the lower limit, the distance from the lens surface of the front group GF closest to the object to the entrance pupil position at the wide-angle side does not become too short, making it easy to suppress aberration fluctuations during magnification variation. By ensuring that the corresponding value of conditional expression (18) is not above the upper limit, the distance from the lens surface of the front group GF closest to the object to the entrance pupil position at the wide-angle side does not become too long, making it possible to prevent the diameter of the front group GF from becoming too large, thereby facilitating size reduction. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (18-1), and it is even more preferable that the following conditional expression (18-2) is satisfied. 0.3 <DDFSTw / TLw<0.7 (18) 0.38 <DDFSTw / TLw<0.6 (18-1) 0.43 <DDFSTw / TLw<0.5 (18-2)

[0174] If the back focal length at the air-equivalent distance of the entire system when focused on an object at infinity at the wide-angle end is Bfw, it is preferable that the variable magnification optical system satisfy the following conditional expression (19): By ensuring that the corresponding value of conditional expression (19) is not below the lower limit, the back focal length Bfw defined above does not become too short, making it easy to attach a mount exchange mechanism. By ensuring that the corresponding value of conditional expression (19) is not above the upper limit, the back focal length Bfw defined above does not become too long, making it easy to achieve compactness. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (19-1), and it is even more preferable that it satisfy the following conditional expression (19-2). 0.08 <Bfw / TLw<0.27 (19) 0.1 <Bfw / TLw<0.25 (19-1) 0.12 <Bfw / TLw<0.22 (19-2)

[0175] It is preferable that a variable magnification optical system satisfy the following conditional expression (20). Here, Expw is the sum of the axial distance from the paraxial exit pupil position Pex to the lens surface of the rear group GR closest to the image when focused on an object at infinity at the wide-angle end, and the back focal length Bfw of the entire system in terms of air equivalent distance. As an example, FIG. 3 shows the paraxial exit pupil position Pex and the distance Expw defined above when the variable magnification optical system of FIG. 1 is focused on an object at infinity at the wide-angle end. In this specification, the sign of Expw is positive if the paraxial exit pupil position Pex is closer to the object than the image plane Sim, and negative if the paraxial exit pupil position Pex is closer to the image than the image plane Sim. By ensuring that the corresponding value of conditional expression (20) is not less than the lower limit, it becomes easier to shorten the overall length of the optical system, which is advantageous for compactness. By ensuring that the corresponding value of conditional expression (20) does not exceed the upper limit, it becomes easy to reduce the angle of incidence of the off-axial chief ray onto the image plane Sim, which is advantageous for ensuring the amount of peripheral light. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional expression (20-1), and it is even more preferable that it satisfies the following conditional expression (20-2): 0.28 <fw / Expw<0.65 (20) 0.3 <fw / Expw<0.6 (20-1) 0.32 <fw / Expw<0.58 (20-2)

[0176] In a configuration in which the front group GF includes the first lens, where Rf is the radius of curvature of the object-side surface of the first lens and Rr is the radius of curvature of the image-side surface of the first lens, it is preferable that the variable magnification optical system satisfy the following conditional expression (21). By ensuring that the corresponding value of conditional expression (21) is not below the lower limit, it becomes easy to correct astigmatism, particularly on the telephoto side. By ensuring that the corresponding value of conditional expression (21) is not above the upper limit, it becomes easy to achieve a wider angle of view because the refractive power of the first lens does not become too weak. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (21-1), and it is even more preferable that it satisfy the following conditional expression (21-2). 1.5<(Rf+Rr) / (Rf-Rr)<4.2 (21) 1.6<(Rf+Rr) / (Rf-Rr)<4.1 (21-1) 1.7<(Rf+Rr) / (Rf-Rr)<4 (21-2)

[0177] If the average value of the Abbe numbers of all the positive lenses in the rear group GR based on the d-line is νRpave, it is preferable that the variable magnification optical system satisfy the following conditional expression (22). Ensuring that the corresponding value of conditional expression (22) does not become equal to or smaller than the lower limit thereof is advantageous for correction of axial chromatic aberration, particularly at the telephoto end. Ensuring that the corresponding value of conditional expression (22) does not become equal to or larger than the upper limit thereof is advantageous for correction of various aberrations other than chromatic aberration. In order to obtain even better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (22-1), and it is even more preferable that it satisfy the following conditional expression (22-2). 40<νRpave<90 (22) 45<νRpave<86 (22-1) 50<νRpave<82 (22-2)

[0178] If the difference in the optical axis direction between the position of the middle group GM when focused on an object at infinity at the wide-angle end and the position of the middle group GM when focused on an object at infinity at the telephoto end is DMwt, it is preferable that the variable magnification optical system satisfy the following conditional expression (23). As an example, FIG. 2 shows the difference DMwt defined above for the variable magnification optical system of FIG. 1. The sign of DMwt is positive if the position of the middle group GM when focused on an object at infinity at the telephoto end is closer to the image than the position of the middle group GM when focused on an object at infinity at the wide-angle end; it is negative if the position of the middle group GM when focused on an object at infinity at the telephoto end is closer to the object than the position of the middle group GM when focused on an object at infinity at the wide-angle end. The unit of DMwt is millimeters. By ensuring that the corresponding value of conditional expression (23) is not below the lower limit, the amount of movement of the middle group GM during magnification change can be suppressed, which is advantageous for making the optical system more compact. Ensuring that the corresponding value of conditional expression (23) does not exceed the upper limit is advantageous in suppressing aberration fluctuations during zooming. In order to obtain better characteristics, it is more preferable that the zoom optical system satisfy the following conditional expression (23-1), and even more preferable that it satisfy the following conditional expression (23-2). -0.2<(ft / fw) / DMwt<-0.04 (23) -0.19<(ft / fw) / DMwt<-0.05 (23-1) -0.18<(ft / fw) / DMwt<-0.06 (23-1)

[0179] In a configuration in which the front group GF includes at least three negative lenses, including the first lens, where NL1 denotes the refractive index at the d-line of the first lens and NLn2 denotes the refractive index at the d-line of the second negative lens in the front group from the object side, it is preferable that the variable magnification optical system satisfy the following conditional expression (24): By ensuring that the corresponding value of conditional expression (24) is not below the lower limit, it is easy to ensure the refractive power of the front group GF, which is advantageous for reducing distortion at the wide-angle end while shortening the focal length of the variable magnification optical system at the wide-angle end. By ensuring that the corresponding value of conditional expression (24) is not above the upper limit, it is possible to prevent the weight of the first lens and the second negative lens in the front group from the object side from increasing. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (24-1), and even more preferable that the following conditional expression (24-2) be satisfied. 1.58<(NL1+NLn2) / 2<2.2 (24) 1.62<(NL1+NLn2) / 2<2.15 (24-1) 1.7<(NL1+NLn2) / 2<2.1 (24-2)

[0180] It is preferable that the image-side surface of the lens with the strongest positive refractive power in the rear group is a convex surface. This is advantageous for correcting spherical aberration throughout the entire range of magnification. It is also preferable that the lens with the strongest positive refractive power in the rear group is a biconvex lens. This is advantageous for correcting spherical aberration, particularly at the telephoto end.

[0181] In a configuration in which the image-side surface of the lens with the strongest positive refractive power in the rear group is convex, where the focal length of the lens with the strongest positive refractive power in the rear group is fRLp, it is preferable that the variable magnification optical system satisfy the following conditional expression (25): Ensuring that the corresponding value of conditional expression (25) is not below the lower limit is advantageous for correcting spherical aberration, particularly at the telephoto end. Ensuring that the corresponding value of conditional expression (25) is not above the upper limit is advantageous for ensuring peripheral light intensity, particularly at the wide-angle end, since it becomes easier to reduce the angle of incidence of off-axial chief rays onto the image plane Sim. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (25-1), and even more preferable that it satisfy the following conditional expression (25-2). -10 <fRw / fRLp<5 (25) -9.5 <fRw / fRLp<4.5 (25-1) -9 <fRw / fRLp<4 (25-2)

[0182] If the effective diameter of the lens surface of the front group GF closest to the object is EDf and the effective diameter of the lens surface of the rear group GR closest to the image is EDr, it is preferable that the variable magnification optical system satisfy the following conditional expression (26). Generally, to reduce the diameter of the lens closest to the object, the refractive power of the front group GF must be increased. When the refractive power of the front group GF is increased, the fluctuation in aberrations during magnification tends to increase. For these reasons, ensuring that the value corresponding to conditional expression (26) is not below the lower limit prevents the diameter of the lens closest to the object from becoming too small, which is advantageous for suppressing fluctuation in aberrations during magnification. Also, ensuring that the value corresponding to conditional expression (26) is not below the lower limit prevents the diameter of the lens closest to the object from becoming too small, which is advantageous for ensuring the peripheral illumination ratio at the maximum image height. Ensuring that the value corresponding to conditional expression (26) is not above the upper limit prevents the diameter of the lens closest to the object from becoming too large, which facilitates compactness. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional expression (26-1), and it is even more preferable that the variable magnification optical system satisfies the following conditional expression (26-2). 1.1 <EDf / EDr<2.1 (26) 1.2 <EDf / EDr<2 (26-1) 1.3 <EDf / EDr<1.9 (26-2)

[0183] In this specification, the "effective diameter" of a lens surface is defined as twice the distance from the point of intersection of the outermost ray and the lens surface, among the rays that enter the lens surface from the object side and exit to the image side, to the optical axis Z. Here, "outside" refers to the radially outward direction centered on the optical axis Z, i.e., the side away from the optical axis Z. The "outside ray" is determined taking into account the entire range of magnification.

[0184] For explanatory purposes, FIG. 4 shows an example of the effective diameter ED. In FIG. 4, the left side is the object side and the right side is the image side. FIG. 4 shows an on-axis ray Xa and an off-axis ray Xb passing through the lens Lx. In the example of FIG. 4, ray Xb1, which is the upper ray of the off-axis ray Xb, is the outermost ray. Therefore, in the example of FIG. 4, the effective diameter ED of the object-side surface of the lens Lx is twice the distance from the intersection of the object-side surface of the lens Lx and ray Xb1 to the optical axis Z. Note that in FIG. 4, the upper ray of the off-axis ray Xb is the outermost ray, but which ray is the outermost ray varies depending on the optical system.

[0185] It is preferable that the variable magnification optical system satisfies the following conditional expression (27): By ensuring that the corresponding value of conditional expression (27) is not below the lower limit, the overall length of the optical system can be prevented from increasing, thereby facilitating size reduction in the optical axis direction. By ensuring that the corresponding value of conditional expression (27) is not above the upper limit, the diameter of the lens closest to the object can be prevented from increasing, thereby facilitating size reduction in the radial direction. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional expression (27-1), and it is even more preferable that the following conditional expression (27-2) be satisfied. 0.2 <EDf / TLw<0.45 (27) 0.25 <EDf / TLw<0.41 (27-1) 0.3 <EDf / TLw<0.375 (27-2)

[0186] In a configuration in which the front group GF includes at least three negative lenses, when the Abbe number based on the d-line of the third negative lens from the object side among the negative lenses in the front group is vLn3, it is preferable that the variable magnification optical system satisfy the following conditional expression (28): By ensuring that the corresponding value of conditional expression (28) is not equal to or less than the lower limit, it is possible to prevent over-correction of longitudinal chromatic aberration at the telephoto end. By ensuring that the corresponding value of conditional expression (28) is not equal to or greater than the upper limit, it is possible to prevent under-correction of longitudinal chromatic aberration at the telephoto end. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfy the following conditional expression (28-1), and it is even more preferable that it satisfy the following conditional expression (28-2). 50<νLn3<95 (28) 55<νLn3<91 (28-1) 60<νLn3<87 (28-2)

[0187] The above-described preferred and possible configurations can be arbitrarily combined, and are preferably selectively adopted as appropriate according to the required specifications. Note that the conditional expressions that the variable magnification optical system of the present disclosure preferably satisfies are not limited to those written in the form of an equation, but include all conditional expressions obtained by arbitrarily combining the lower and upper limits of the preferred, more preferred, and even more preferred conditional expressions.

[0188] As an example, one preferred embodiment of the variable magnification optical system of the present disclosure comprises, in order from the object side to the image side, a front group GF, a middle group GM, and a rear group GR, wherein the front group GF consists of two or less lens groups and has negative refractive power overall over the entire range of variable magnification, the middle group GM includes only one lens group with positive refractive power as a lens group, and the rear group GR consists of three or less lens groups, an aperture stop St is disposed between the lens surface of the front group GF closest to the image and the lens surface of the rear group GR closest to the object, and the distance between the front group GF and the middle group GM changes during variable magnification, The variable magnification optical system satisfies the above conditional expressions (1) and (2), in which the distance between the middle group GM and the rear group GR changes, and in the case where the front group GF consists of two lens groups, the distance between adjacent lens groups in the front group changes when magnification is changed, and in the case where the rear group GR consists of multiple lens groups, the distance between all of the adjacent lens groups in the rear group changes when magnification is changed, the front group GF includes at least three negative lens elements and at least one positive lens element, and a first lens element having negative refractive power and a meniscus shape with its convex surface facing the object side is located closest to the object in the front group GF.

[0189] Next, examples of the variable magnification optical system of the present disclosure will be described with reference to the drawings. The reference symbols attached to the lenses in the cross-sectional views of each example are used independently for each example to avoid cluttering the explanation and the drawings due to an increase in the number of digits of the reference symbols. Therefore, even if common reference symbols are attached in drawings of different examples, they do not necessarily have the same configuration. Furthermore, the following Examples 4, 10 to 12, and 19 are examples of the present disclosure, and Examples 1 to 3, 5 to 9, and 13 to 18 are reference examples of the present disclosure.

[0190] [Example 1] The configuration and movement direction of the variable magnification optical system of Example 1 are shown in Figure 1. The illustration method and configuration are as described above, so some overlapping explanations will be omitted here. The variable magnification optical system of Example 1 consists, in order from the object side to the image side, of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of three lenses, lenses L21 to L23, and an aperture stop St. The third lens group G3 consists, in order from the object side to the image side, of five lenses, lenses L31 to L35.

[0191] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3. The focusing group consists of two lenses, lenses L31 and L32. When focusing from an object at infinity to a close object, the focusing group moves toward the object.

[0192] For the variable magnification optical system of Example 1, basic lens data is shown in Table 1, specifications and variable surface spacing are shown in Table 2, and aspherical coefficients are shown in Table 3. The table of basic lens data is written as follows: The Sn column shows the surface numbers, with the surface closest to the object being surface 1 and the numbers increasing by one as one moves toward the image side. The R column shows the radius of curvature of each surface. The D column shows the surface spacing on the optical axis between each surface and its adjacent surface on the image side. The Nd column shows the refractive index for the d-line of each component element. The νd column shows the Abbe number of each component element based on the d-line. The ED column shows the effective diameter of the lens surface closest to the object side and the lens surface closest to the image side.

[0193] In the table of basic lens data, the sign of the radius of curvature of a surface with a convex surface facing the object side is positive, and the sign of the radius of curvature of a surface with a convex surface facing the image side is negative. The column for the surface number corresponding to the aperture stop St contains the surface number and the term (St). The value in the bottom column of the D column in the table is the distance between the surface in the table closest to the image side and the image plane Sim. The symbol DD[ ] is used to indicate variable surface distances, and the surface number on the object side of this distance is entered in the [ ] in the D column.

[0194] Table 2 shows the zoom ratio Zr, focal length f, back focal length Bf in air equivalent distance, maximum F-number FNo., maximum full angle of view 2ω, and variable surface spacing during zooming, based on the d-line. When the zoom optical system is a zoom lens, the zoom ratio is synonymous with the zoom magnification. The [°] in the 2ω column indicates that the unit is degrees. In Table 2, the columns labeled "Wide," "Middle," and "Tele" show the values ​​for the wide-angle end state, mid-focal length state, and telephoto end state, respectively.

[0195] In the basic lens data, the surface numbers of aspherical surfaces are marked with an *, and the numerical value of the paraxial radius of curvature is entered in the column for the radius of curvature of the aspherical surface. In Table 3, the Sn row shows the surface numbers of aspherical surfaces, and the KA and Am rows show the numerical values ​​of the aspherical coefficients for each aspherical surface. Note that m in Am is an integer of 3 or more, and varies depending on the surface. For example, for the third surface in Example 1, m = 4, 6, 8, 10, 12. The numerical values ​​of the aspherical coefficients in Table 3, "E±n" (n: integer), are expressed as "×10 ±n KA and Am are aspherical coefficients in the aspherical formula given below. Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspheric depth (length of the perpendicular line drawn from a point on the aspheric surface at height h to a plane perpendicular to the optical axis Z where the vertex of the aspheric surface is in contact) h: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial radius of curvature KA, Am: aspherical coefficients In the aspherical formula, Σ means the summation over m.

[0196] In the basic lens data, the surface numbers of aspherical surfaces of hybrid aspherical lenses are marked with **. For example, in Example 1, lens L33 is a hybrid aspherical lens, and the surface number of surface 19 in Table 1, which corresponds to the aspherical surface of lens L33, is marked with **.

[0197] In the data in each table, degrees are used as the unit of angle and millimeters as the unit of length, but since the optical system can be used with proportional magnification or reduction, other appropriate units can also be used. Also, in each table below, values ​​are listed rounded to a predetermined number of decimal places.

[0198] [Table 1]

[0199] [Table 2]

[0200] [Table 3]

[0201] FIG. 5 shows aberration diagrams of the variable magnification optical system of Example 1 when focused on an object at infinity. From left to right, FIG. 5 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In FIG. 5, the upper row labeled "Wide" shows aberrations at the wide-angle end, the middle row labeled "Middle" shows aberrations at the intermediate focal length, and the lower row labeled "Tele" shows aberrations at the telephoto end. In the spherical aberration diagram, aberrations at the d-line, F-line, and C-line are shown by solid lines, long-dashed lines, and short-dashed lines, respectively. In the astigmatism diagram, aberrations at the d-line in the sagittal direction are shown by solid lines, and aberrations at the d-line in the tangential direction are shown by short-dashed lines. In the distortion diagram, aberrations at the d-line are shown by solid lines. In the lateral chromatic aberration diagram, aberrations at the F-line and C-line are shown by long-dashed lines and short-dashed lines, respectively. In the spherical aberration diagram, the maximum F-number is shown after FNo.=. In the other aberration diagrams, the maximum half angle of view is shown after ω=.

[0202] The symbols, meanings, notation methods, and illustration methods of each data item related to the above-mentioned Example 1 are basically the same in the following Examples unless otherwise specified, and therefore, redundant explanations will be omitted below.

[0203] [Example 2] The configuration and movement direction of the variable magnification optical system of Example 2 are shown in Figure 6. The variable magnification optical system of Example 2 consists of, from the object side to the image side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. The first lens group G1 consists of four lenses, L11 to L14, from the object side to the image side. The second lens group G2 consists of three lenses, L21 to L23, from the object side to the image side, and an aperture stop St. The third lens group G3 consists of two lenses, L31 and L32, from the object side to the image side. The fourth lens group G4 consists of three lenses, L41 to L43, from the object side to the image side.

[0204] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3 and the fourth lens group G4. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the object.

[0205] For the variable magnification optical system of Example 2, basic lens data is shown in Table 4, specifications and variable surface spacing in Table 5, aspherical coefficients in Table 6, and aberration diagrams in FIG.

[0206] [Table 4]

[0207] [Table 5]

[0208] [Table 6]

[0209] [Example 3] The configuration and movement direction of the variable magnification optical system of Example 3 are shown in Figure 8. The variable magnification optical system of Example 3 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having negative refractive power. The first lens group G1 consists, in order from the object side to the image side, of five lenses, lenses L11 to L15. The second lens group G2 consists, in order from the object side to the image side, of three lenses, lenses L21 to L23, and an aperture stop St. The third lens group G3 consists, in order from the object side to the image side, of two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of three lenses, lenses L41 to L43.

[0210] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3 and the fourth lens group G4. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the object.

[0211] For the variable magnification optical system of Example 3, basic lens data is shown in Table 7, specifications and variable surface spacing in Table 8, aspherical coefficients in Table 9, and various aberration diagrams in FIG.

[0212] [Table 7]

[0213] [Table 8]

[0214] [Table 9]

[0215] [Example 4] The configuration and movement direction of the variable magnification optical system of Example 4 are shown in Figure 10. The variable magnification optical system of Example 4 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having negative refractive power. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of lenses L21 and L22, an aperture stop St, and lenses L23 to L25. The third lens group G3 consists, in order from the object side to the image side, of two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of three lenses, lenses L41 to L43.

[0216] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3 and the fourth lens group G4. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0217] For the variable magnification optical system of Example 4, basic lens data is shown in Table 10, specifications and variable surface spacing in Table 11, aspherical coefficients in Table 12, and various aberration diagrams in FIG.

[0218] [Table 10]

[0219] [Table 11]

[0220] [Table 12]

[0221] [Example 5] The configuration and movement direction of the variable magnification optical system of Example 5 are shown in Figure 12. The variable magnification optical system of Example 5 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of three lenses, lenses L21 to L23, and an aperture stop St. The third lens group G3 consists, in order from the object side to the image side, of two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of two lenses, lenses L41 and L42. The fifth lens group G5 is made up of one lens, lens L51.

[0222] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, the fourth lens group G4, and the fifth lens group G5. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the object.

[0223] For the variable magnification optical system of Example 5, basic lens data is shown in Table 13, specifications and variable surface spacing in Table 14, aspherical coefficients in Table 15, and various aberration diagrams in FIG.

[0224] [Table 13]

[0225] [Table 14]

[0226] [Table 15]

[0227] [Example 6] The configuration and movement direction of the variable magnification optical system of Example 6 are shown in Figure 14. The variable magnification optical system of Example 6 consists of, from the object side to the image side, a first lens group G1 having negative refractive power, a second lens group G2 having positive 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. The first lens group G1 consists of four lenses, L11 to L14, from the object side to the image side. The second lens group G2 consists of three lenses, L21 to L23, from the object side to the image side. The third lens group G3 consists of, from the object side to the image side, an aperture stop St and three lenses, L31 to L33. The fourth lens group G4 consists of a single lens, L41. The fifth lens group G5 is composed of, in order from the object side to the image side, two lenses, lenses L51 and L52.

[0228] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, fourth lens group G4, and fifth lens group G5. The focusing group consists of the fourth lens group G4. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0229] For the variable magnification optical system of Example 6, basic lens data is shown in Table 16, specifications and variable surface spacing in Table 17, aspherical coefficients in Table 18, and various aberration diagrams in FIG.

[0230] [Table 16]

[0231] [Table 17]

[0232] [Table 18]

[0233] [Example 7] The configuration and movement direction of the variable magnification optical system of Example 7 are shown in Figure 16. The variable magnification optical system of Example 7 is composed of, in order from the object side to the image side, a first lens group G1 having negative refractive power, a second lens group G2 having positive 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. The first lens group G1 is composed of five lenses, lenses L11 to L15, in order from the object side to the image side. The second lens group G2 is composed of three lenses, lenses L21 to L23, in order from the object side to the image side. The third lens group G3 is composed of an aperture stop St and three lenses, lenses L31 to L33, in order from the object side to the image side. The fourth lens group G4 is made up of one lens, lens L41. The fifth lens group G5 is made up of, in order from the object side to the image side, two lenses, lens L51 and lens L52.

[0234] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, fourth lens group G4, and fifth lens group G5. The focusing group consists of the fourth lens group G4. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0235] For the variable magnification optical system of Example 7, basic lens data is shown in Table 19, specifications and variable surface spacing in Table 20, aspherical coefficients in Table 21, and aberration diagrams in FIG.

[0236] [Table 19]

[0237] [Table 20]

[0238] [Table 21]

[0239] [Example 8] The configuration and movement direction of the variable magnification optical system of Example 8 are shown in Figure 18. The variable magnification optical system of Example 8 comprises, in order from the object side to the image side, a first lens group G1 having negative refractive power and a second lens group G2 having positive refractive power. The lens group G1 consists of a lens group G2, a third lens group G3 with positive refractive power, a fourth lens group G4 with negative refractive power, and a fifth lens group G5 with positive refractive power. The first lens group G1 consists of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 consists of three lenses, L21 to L23, in order from the object side to the image side. The third lens group G3 consists of an aperture stop St and three lenses, L31 to L33, in order from the object side to the image side. The fourth lens group G4 consists of one lens, L41. The fifth lens group G5 consists of three lenses, L51 to L53, in order from the object side to the image side.

[0240] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, fourth lens group G4, and fifth lens group G5. The focusing group consists of the fourth lens group G4. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0241] For the variable magnification optical system of Example 8, basic lens data is shown in Table 22, specifications and variable surface spacing in Table 23, aspherical coefficients in Table 24, and various aberration diagrams in FIG.

[0242] [Table 22]

[0243] [Table 23]

[0244] [Table 24]

[0245] [Example 9] The configuration and movement direction of the variable magnification optical system of Example 9 are shown in Figure 20. The variable magnification optical system of Example 9 consists of, from the object side to the image side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power. The first lens group G1 consists of four lenses, L11 to L14, from the object side to the image side. The second lens group G2 consists of three lenses, L21 to L23, from the object side to the image side, and an aperture stop St. The third lens group G3 consists of three lenses, L31 to L33, from the object side to the image side. The fourth lens group G4 consists of a single lens, L41. The fifth lens group G5 is composed of, in order from the object side to the image side, two lenses, lenses L51 and L52.

[0246] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, fourth lens group G4, and fifth lens group G5. The focusing group consists of the fourth lens group G4. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0247] For the variable magnification optical system of Example 9, basic lens data is shown in Table 25, specifications and variable surface spacing in Table 26, aspherical coefficients in Table 27, and various aberration diagrams in FIG.

[0248] [Table 25]

[0249] [Table 26]

[0250] [Table 27]

[0251] [Example 10] The configuration and movement direction of the variable magnification optical system of Example 10 are shown in Figure 22. The variable magnification optical system of Example 10 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of lenses L21 and L22, an aperture stop St, and lenses L23 to L25. The third lens group G3 consists, in order from the object side to the image side, of two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of two lenses, lenses L41 and L42. The fifth lens group G5 is made up of one lens, lens L51.

[0252] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, the fourth lens group G4, and the fifth lens group G5. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0253] For the variable magnification optical system of Example 10, basic lens data is shown in Table 28, specifications and variable surface spacing in Table 29, aspherical coefficients in Table 30, and various aberration diagrams in FIG.

[0254] [Table 28]

[0255] [Table 29]

[0256] [Table 30]

[0257] [Example 11] The configuration and movement direction of the variable magnification optical system of Example 11 are shown in Figure 24. The variable magnification optical system of Example 11 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having positive refractive power. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of three lenses, lenses L21 to L23. The third lens group G3 consists, in order from the object side to the image side, of an aperture stop St and two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of three lenses, lenses L41 to L43. The fifth lens group G5 is made up of three lenses, lenses L51 to L53, in that order from the object side to the image side.

[0258] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, the fourth lens group G4, and the fifth lens group G5. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0259] For the variable magnification optical system of Example 11, basic lens data is shown in Table 31, specifications and variable surface spacing in Table 32, aspherical coefficients in Table 33, and various aberration diagrams in FIG.

[0260] [Table 31]

[0261] [Table 32]

[0262] [Table 33]

[0263] [Example 12] The configuration and movement direction of the variable magnification optical system of Example 12 are shown in Figure 26. The variable magnification optical system of Example 12 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of three lenses, lenses L21 to L23. The third lens group G3 consists, in order from the object side to the image side, of an aperture stop St and two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of four lenses, lenses L41 to L44. The fifth lens group G5 is made up of three lenses, lenses L51 to L53, in that order from the object side to the image side.

[0264] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, the fourth lens group G4, and the fifth lens group G5. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0265] For the variable magnification optical system of Example 12, basic lens data is shown in Table 34, specifications and variable surface spacing in Table 35, aspherical coefficients in Table 36, and various aberration diagrams in FIG.

[0266] [Table 34]

[0267] [Table 35]

[0268] [Table 36]

[0269] [Example 13] The configuration and movement direction of the variable magnification optical system of Example 13 are shown in Figure 28. The variable magnification optical system of Example 13 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive 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. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of three lenses, lenses L21 to L23, and an aperture stop St. The third lens group G3 consists, in order from the object side to the image side, of two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of three lenses, lenses L41 to L43. The fifth lens group G5 is made up of one lens, lens L51.

[0270] During magnification change, the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 move along the optical axis Z while changing the spacing between adjacent lens groups, while the fifth lens group G5 remains fixed relative to the image plane Sim. The grounding symbols below the fifth lens group G5 in the upper and middle rows of Figure 28 indicate that the fifth lens group G5 remains fixed relative to the image plane Sim during magnification change. The method of illustrating the grounding symbols is the same in the cross-sectional views of other embodiments. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, the fourth lens group G4, and the fifth lens group G5. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the object.

[0271] For the variable magnification optical system of Example 13, basic lens data is shown in Table 37, specifications and variable surface spacing in Table 38, aspherical coefficients in Table 39, and various aberration diagrams in FIG.

[0272] [Table 37]

[0273] [Table 38]

[0274] [Table 39]

[0275] [Example 14] The configuration and movement direction of the variable magnification optical system of Example 14 are shown in Figure 30. The variable magnification optical system of Example 14 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive 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. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of three lenses, lenses L21 to L23, and an aperture stop St. The third lens group G3 consists, in order from the object side to the image side, of two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of three lenses, lenses L41 to L43. The fifth lens group G5 is made up of one lens, lens L51.

[0276] When varying magnification, the first lens group G1, second lens group G2, third lens group G3, and fourth lens group G4 move along the optical axis Z while changing the spacing between adjacent lens groups, while the fifth lens group G5 is fixed relative to the image plane Sim. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, fourth lens group G4, and fifth lens group G5. The focusing group consists of the third lens group G3. When focusing from an object at infinity to an object at close range, the focusing group moves toward the object.

[0277] For the variable magnification optical system of Example 14, basic lens data is shown in Table 40, specifications and variable surface spacing in Table 41, aspherical coefficients in Table 42, and various aberration diagrams in FIG.

[0278] [Table 40]

[0279] [Table 41]

[0280] [Table 42]

[0281] [Example 15] The configuration and movement direction of the variable magnification optical system of Example 15 are shown in Figure 32. The variable magnification optical system of Example 15 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive 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. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of three lenses, lenses L21 to L23, and an aperture stop St. The third lens group G3 consists, in order from the object side to the image side, of two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of three lenses, lenses L41 to L43. The fifth lens group G5 is made up of one lens, lens L51.

[0282] When varying magnification, the first lens group G1, second lens group G2, third lens group G3, and fourth lens group G4 move along the optical axis Z while changing the spacing between adjacent lens groups, while the fifth lens group G5 is fixed relative to the image plane Sim. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, fourth lens group G4, and fifth lens group G5. The focusing group consists of the third lens group G3. When focusing from an object at infinity to an object at close range, the focusing group moves toward the object.

[0283] For the variable magnification optical system of Example 15, basic lens data is shown in Table 43, specifications and variable surface spacing in Table 44, aspherical coefficients in Table 45, and various aberration diagrams in FIG.

[0284] [Table 43]

[0285] [Table 44]

[0286] [Table 45]

[0287] [Example 16] The configuration and movement direction of the variable magnification optical system of Example 16 are shown in Figure 34. The variable magnification optical system of Example 16 consists of, in order from the object side to the image side, a first lens group G1 having negative refractive power, a second lens group G2 having positive 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. The first lens group G1 consists of, in order from the object side to the image side, four lenses, lenses L11 to L14. The second lens group G2 consists of, in order from the object side to the image side, three lenses, lenses L21 to L23. The third lens group G3 consists of, in order from the object side to the image side, an aperture stop St and three lenses, lenses L31 to L33. The fourth lens group G4 consists of a single lens, lens L41. The fifth lens group G5 is composed of, in order from the object side to the image side, two lenses, lenses L51 and L52.

[0288] When varying magnification, the first lens group G1 is fixed relative to the image plane Sim, while the second lens group G2, third lens group G3, fourth lens group G4, and fifth lens group G5 move along the optical axis Z while changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3, fourth lens group G4, and fifth lens group G5. The focusing group consists of the fourth lens group G4. When focusing from an object at infinity to an object at close range, the focusing group moves toward the image side.

[0289] For the variable magnification optical system of Example 16, basic lens data is shown in Table 46, specifications and variable surface spacing in Table 47, aspherical coefficients in Table 48, and various aberration diagrams in FIG.

[0290] [Table 46]

[0291] [Table 47]

[0292] [Table 48]

[0293] [Example 17] The configuration and movement direction of the variable magnification optical system of Example 17 are shown in Figure 36. The variable magnification optical system of Example 17 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power. The first lens group G1 consists, in order from the object side to the image side, of two lenses, lenses L11 and L12. The second lens group G2 consists, in order from the object side to the image side, of two lenses, lenses L21 and L22. The third lens group G3 consists, in order from the object side to the image side, of three lenses, lenses L31 to L33, and an aperture stop St. The fourth lens group G4 consists, in order from the object side to the image side, of two lenses, lenses L41 and L42. The fifth lens group G5 is made up of four lenses, lenses L51 to L54, in that order from the object side to the image side.

[0294] When varying magnification, the first lens group G1 is fixed relative to the image plane Sim, while 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 Z while changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1 and the second lens group G2. The middle group GM consists of the third lens group G3. The rear group GR consists of the fourth lens group G4 and the fifth lens group G5. The focusing group consists of the fourth lens group G4. When focusing from an object at infinity to an object at close range, the focusing group moves toward the object.

[0295] For the variable magnification optical system of Example 17, basic lens data is shown in Table 49, specifications and variable surface spacing in Table 50, aspherical coefficients in Table 51, and various aberration diagrams in FIG.

[0296] [Table 49]

[0297] [Table 50]

[0298] [Table 51]

[0299] [Example 18] The configuration and movement direction of the variable magnification optical system of Example 18 are shown in Figure 38. The variable magnification optical system of Example 18 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive 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. The first lens group G1 consists, in order from the object side to the image side, of two lenses, lenses L11 and L12. The second lens group G2 consists, in order from the object side to the image side, of two lenses, lenses L21 and L22. The third lens group G3 consists, in order from the object side to the image side, of three lenses, lenses L31 to L33, and an aperture stop St. The fourth lens group G4 consists of, in order from the object side to the image side, two lenses, L41 and L42. The fifth lens group G5 consists of, in order from the object side to the image side, three lenses, L51 to L53. The sixth lens group G6 consists of one lens, lens L61.

[0300] During magnification variation, the first lens group G1 and the sixth lens group G6 are fixed relative to the image plane Sim, while 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 Z while changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1 and the second lens group G2. The middle group GM consists of the third lens group G3. The rear group GR consists of the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. The focusing group consists of the fourth lens group G4. When focusing from an object at infinity to an object at close range, the focusing group moves toward the object.

[0301] For the variable magnification optical system of Example 18, basic lens data is shown in Table 52, specifications and variable surface spacing in Table 53, aspherical coefficients in Table 54, and various aberration diagrams in FIG.

[0302] [Table 52]

[0303] [Table 53]

[0304] [Table 54]

[0305] [Example 19] The configuration and movement direction of the variable magnification optical system of Example 19 are shown in Figure 40. The variable magnification optical system of Example 19 consists, in order from the object side to the image side, of a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power. The first lens group G1 consists, in order from the object side to the image side, of four lenses, lenses L11 to L14. The second lens group G2 consists, in order from the object side to the image side, of lenses L21 and L22, an aperture stop St, and lenses L23 to L25. The third lens group G3 consists, in order from the object side to the image side, of two lenses, lenses L31 and L32. The fourth lens group G4 consists, in order from the object side to the image side, of two lenses, lenses L41 and L42.

[0306] When varying magnification, all lens groups move along the optical axis Z, changing the spacing between adjacent lens groups. The front group GF consists of the first lens group G1. The middle group GM consists of the second lens group G2. The rear group GR consists of the third lens group G3 and the fourth lens group G4. The focusing group consists of the third lens group G3. When focusing from an object at infinity to a close object, the focusing group moves toward the image side.

[0307] For the variable magnification optical system of Example 19, basic lens data is shown in Table 55, specifications and variable surface spacing in Table 56, aspherical coefficients in Table 57, and various aberration diagrams in FIG.

[0308] [Table 55]

[0309] [Table 56]

[0310] [Table 57]

[0311] Tables 58 to 61 show the corresponding values ​​of conditional expressions (1) to (28) for the variable magnification optical systems of Examples 1 to 19. The corresponding values ​​of the Examples shown in Tables 58 to 61 may be used as the upper or lower limits of the conditional expressions to set even more preferable ranges for the conditional expressions.

[0312] [Table 58]

[0313] [Table 59]

[0314] [Table 60]

[0315] [Table 61]

[0316] The variable magnification optical systems of Examples 1 to 19 are compact, yet achieve a wide angle of view with a total angle of view exceeding 100 degrees at the wide-angle end.The variable magnification optical systems of Examples 1 to 19 have a maximum variable magnification ratio of 1.7 or more, which is a relatively high variable magnification ratio for a wide-angle optical system.In addition, the variable magnification optical systems of Examples 1 to 19 maintain high optical performance with various aberrations well corrected.

[0317] Next, an imaging device according to an embodiment of the present disclosure will be described. Fig. 42 and Fig. 43 show external views of a camera 30, which is an imaging device according to an embodiment of the present disclosure. Fig. 42 shows a perspective view of the camera 30 as seen from the front side, and Fig. 43 shows a perspective view of the camera 30 as seen from the rear side. The camera 30 is a so-called mirrorless digital camera, to which an interchangeable lens 20 can be removably attached. The interchangeable lens 20 is configured to include a variable magnification optical system 1 according to an embodiment of the present disclosure housed in a lens barrel.

[0318] The camera 30 includes a camera body 31, and a shutter button 32 and a power button 33 are provided on the top surface of the camera body 31. An operation unit 34, an operation unit 35, and a display unit 36 ​​are provided on the back surface of the camera body 31. The display unit 36 ​​can display a captured image and an image within the angle of view before the image was captured.

[0319] A photographic opening through which light from the subject to be photographed enters is provided in the center of the front face of the camera body 31, and a mount 37 is provided at a position corresponding to the photographic opening, and an interchangeable lens 20 is attached to the camera body 31 via the mount 37.

[0320] Inside the camera body 31 are provided an imaging element such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) that outputs an imaging signal corresponding to the subject image formed by the interchangeable lens 20, a signal processing circuit that processes the imaging signal output from the imaging element to generate an image, and a recording medium for recording the generated image. With the camera 30, it is possible to take still images or videos by pressing the shutter button 32, and the image data obtained by this shooting is recorded on the recording medium.

[0321] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values ​​shown in the above examples and can take other values.

[0322] Furthermore, the imaging device according to the embodiment of the present disclosure is not limited to the above example, and can take various forms, such as a camera other than a mirrorless type, a film camera, a video camera, and a security camera. [Explanation of symbols]

[0323] 1 Variable magnification optical system 20 Interchangeable Lenses 30 Camera 31 Camera Body 32 Shutter button 33 Power button 34 Control section 35 Control section 36 Display section 37 Mount Bfw back focus DDFSTw Distance DMwt difference ED Effective Diameter Enpw distance Expw distance G1 First lens group G2 Second lens group G3 Third lens group G4 4th lens group G5 5th lens group G6 6th lens group GF front group GM middle group GR rear group L11~L61 lenses Lx Lens ma On-axis luminous flux mb luminous flux Pen paraxial entrance pupil position Pex paraxial exit pupil position Sim image plane St aperture stop ta axial luminous flux tb luminous flux TLw full length wa axial luminous flux wb luminous flux Xa On-axis luminous flux Xb Off-axis luminous flux Xb1 ray Z optical axis ωm Maximum half angle of view ωt Maximum half angle of view ωw Maximum half angle of view

Claims

1. A variable magnification optical system comprising, in order from the object side to the image side, a front group, a middle group, and a rear group, the variable magnification optical system is a zoom lens, the front group is made up of one lens group having negative refractive power that moves during zooming, the middle group includes only one lens group having positive refractive power, the rear group consists of three or less lens groups, a lens group having negative refractive power is disposed closest to the object side of the rear group; an aperture stop is disposed between the lens surface of the front group closest to the image side and the lens surface of the rear group closest to the object side; When the magnification is changed, the distance between the front group and the middle group changes, and the distance between the middle group and the rear group changes, When the rear group is made up of a plurality of lens groups, the intervals between all of the adjacent lens groups in the rear group change during magnification. the front group includes at least three negative lens elements and at least one positive lens element, a first lens element having a meniscus shape and negative refractive power, with a convex surface facing the object side, is disposed closest to the object side of the front group; TLw is the sum of the distance on the optical axis from the lens surface of the front group closest to the object to the lens surface of the rear group closest to the image when focused on an object at infinity at the wide-angle end, and the back focus in air equivalent distance of the entire system; The focal length of the entire system when focused on an object at infinity at the wide-angle end is fw. The focal length of the entire system when focused on an object at infinity at the telephoto end is ft, The maximum half angle of view when focused on an object at infinity at the telephoto end is ωt. The focal length of the rear lens group when focused on an object at infinity at the wide-angle end is fRw, The radius of curvature of the object side surface of the first lens is Rf, When the radius of curvature of the image-side surface of the first lens is Rr, 3.8<TLw / (ft×tanωt)<5.2 (1) 1<(fw×TLw) / ft ２ <2 (2) 0.464≦(fw×ft) １／２ / |fRw|<1.1 (12-3) 2.226≦(Rf+Rr) / (Rf-Rr)<4.2 (21-3) A variable magnification optical system that satisfies the conditions (1), (2), (12-3), and (21-3) expressed by the following formulas.

2. When the open F-number at the telephoto end when focused on an object at infinity is FNot, 1.5<FNot / (ft / fw)<3 (3) 2. The variable magnification optical system according to claim 1, which satisfies conditional expression (3) expressed as follows:

3. The focal length of the front lens group when focused on an object at infinity at the wide-angle end is fFw, If the focal length of the middle group is fM, 0.1<(-fFw) / fM<1.6 (4) 3. The variable magnification optical system according to claim 1, which satisfies conditional expression (4) expressed as follows:

4. When the focal length of the front group is set to fFw when focused on an object at infinity at the wide-angle end, 0.6<(-fFw) / (fw×ft) １／２ <13 (5) 4. The variable magnification optical system according to claim 1, which satisfies conditional expression (5) expressed as follows:

5. If the focal length of the middle group is fM, 0.65<fM / (fw×ft) １／２ <3.7 (6) 5. The variable magnification optical system according to claim 1, which satisfies conditional expression (6) expressed as follows:

6. The focal length of the first lens is fL1, When the focal length of the front group is set to fFw when focused on an object at infinity at the wide-angle end, 1<fL1 / fFw<3.5 (7) 6. The variable magnification optical system according to claim 1, which satisfies conditional expression (7) expressed as follows:

7. The focal length of the front lens group when focused on an object at infinity at the wide-angle end is fFw, When the open F-number at the telephoto end when focused on an object at infinity is FNot, 1.8<(-fFw) / (ft / FNot)<4 (8) 7. The variable magnification optical system according to claim 1, which satisfies conditional expression (8) expressed as follows:

8. The center thickness of the first lens is D1, When the open F-number at the telephoto end when focused on an object at infinity is FNot, 0.08<D1 / (ft / FNot)<0.42 (9) 8. The variable magnification optical system according to claim 1, which satisfies conditional expression (9) expressed as follows:

9. The maximum half angle of view when focused on an object at infinity at the wide-angle end is ωw, When the maximum F-number when focused on an object at infinity at the wide-angle end is FNow, 0.3<tanωw / FNow<0.47 (10) 9. The variable magnification optical system according to claim 1, which satisfies conditional expression (10) expressed as follows:

10. DDFSTw is the distance on the optical axis from the lens surface of the front group closest to the object to the aperture stop when focused on an object at infinity at the wide-angle end, When the focal length of the front group is set to fFw when focused on an object at infinity at the wide-angle end, 1.4<DDFSTw / |fFw|<4 (14) 10. The variable magnification optical system according to claim 1, which satisfies conditional expression (14) expressed as follows:

11. DDFSTw is the distance on the optical axis from the lens surface of the front group closest to the object to the aperture stop when focused on an object at infinity at the wide-angle end, When the maximum half angle of view at the wide-angle end when focused on an object at infinity is ωw, 5<DDFSTw / {(fw×tanωw)×log(ft / fw)}<10 (16) 11. The variable magnification optical system according to claim 1, which satisfies conditional expression (16) expressed as follows:

12. When the distance on the optical axis from the lens surface of the front group closest to the object to the aperture stop in a state in which the lens is focused on an object at infinity at the wide-angle end is denoted by DDFSTw, 0.3<DDFSTw / TLw<0.7 (18) 12. The variable magnification optical system according to claim 1, which satisfies conditional expression (18) expressed as follows:

13. When the back focus of the entire system in the air equivalent distance when focused on an object at infinity at the wide-angle end is Bfw, 0.08<Bfw / TLw<0.27 (19) 13. The variable magnification optical system according to claim 1, which satisfies conditional expression (19) expressed as follows:

14. When the average value of the Abbe numbers of all the positive lenses in the rear group based on the d-line is νR, 40<νRpave<90 (22) 14. The variable magnification optical system according to claim 1, which satisfies conditional expression (22) expressed as follows:

15. DMwt is the difference in the optical axis direction between the position of the middle group when focused on an object at infinity at the wide-angle end and the position of the middle group when focused on an object at infinity at the telephoto end, The sign of DMwt is positive if the position of the middle group when focused on an object at infinity at the telephoto end is closer to the image side than the position of the middle group when focused on an object at infinity at the wide-angle end, and negative if the position of the middle group when focused on an object at infinity at the telephoto end is closer to the object side than the position of the middle group when focused on an object at infinity at the wide-angle end, and when DMwt is expressed in millimeters, -0.2<(ft / fw) / DMwt<-0.04 (23) 15. The variable magnification optical system according to claim 1, which satisfies conditional expression (23) expressed as follows:

16. The refractive index of the first lens with respect to the d-line is NL1, When the refractive index of the second negative lens from the object side among the negative lenses in the front group is NLn2, 1.58<(NL1+NLn2) / 2<2.2 (24) 16. A variable magnification optical system according to claim 1, which satisfies conditional expression (24) expressed as follows:

17. the image-side surface of the lens element with the strongest positive refractive power in the rear group is a convex surface, The focal length of the lens with the strongest positive refractive power in the rear group is fRLp, When the focal length of the rear lens group at the wide-angle end is focused on an object at infinity, fRw is: -10<fRw / fRLp<5 (25) 17. The variable magnification optical system according to claim 1, which satisfies conditional expression (25) expressed as follows:

18. 18. A variable magnification optical system according to claim 17, wherein the lens having the strongest positive refractive power in the rear group is a biconvex lens.

19. The effective diameter of the lens surface of the front group closest to the object is EDf. When the effective diameter of the lens surface of the rear group closest to the image side is EDr, 1.1<EDf / EDr<2.1 (26) 19. The variable magnification optical system according to claim 1, which satisfies conditional expression (26) expressed as follows:

20. When the effective diameter of the lens surface of the front group closest to the object side is EDf, 0.2<EDf / TLw<0.45 (27) 20. The variable magnification optical system according to claim 1, which satisfies conditional expression (27) expressed as follows:

21. the rear group includes a focusing group that moves along the optical axis during focusing; 21. The variable magnification optical system according to claim 1, wherein the focusing group is made up of two or less lenses.

22. 22. The variable magnification optical system according to claim 21, wherein the focusing group comprises one negative lens element and one positive lens element.

23. including only one focusing group that moves along the optical axis during focusing; 22. A variable magnification optical system according to claim 1, wherein the focusing group is disposed within the rear group.

24. 22. A variable magnification optical system according to claim 1, further comprising at least two cemented lenses, each cemented lens having one positive lens and one negative lens, disposed closer to the image side than the front group.

25. When the Abbe number based on the d-line of the third negative lens from the object side among the negative lenses in the front group is νLn3, 50<νLn3<95 (28) 22. The variable magnification optical system according to claim 1, which satisfies conditional expression (28) expressed as follows:

26. 26. A variable magnification optical system according to claim 1, wherein all lens groups in the rear group move during magnification variation.

27. 27. The variable magnification optical system according to claim 1, wherein the front group includes, in order from the object side to the image side, the first lens, a second lens having a meniscus shape with a convex surface facing the object side and negative refractive power, a third lens having a concave surface facing the image side and negative refractive power, and a fourth lens having a convex surface facing the object side and positive refractive power.

28. An imaging device comprising the variable magnification optical system according to any one of claims 1 to 27.

Images