Variable magnification optical system and imaging 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 disclosed herein relates to a variable magnification optical system and an imaging device. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-148949 [Patent Document 2] Japanese Patent Publication No. 2021-076829 [Overview of the project] [Problems that the invention aims to solve]

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

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

[0006] A first aspect of this 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 fewer lens groups and has a negative refractive power as a whole throughout the entire magnification range, the middle group includes only one lens group having a positive refractive power as a lens group, and the rear group consists of three or fewer lens groups, an aperture diaphragm is positioned between the lens surface closest to the image of the front group and the lens surface closest to the object of the rear group, and when magnification is changed, the distance between the front group and the middle group changes, the distance between the middle group and the rear group changes, and if the front group consists of two lens groups, the distance between adjacent lens groups within the front group changes when magnification is changed, and if the rear group consists of multiple lens groups, the distance between adjacent lens groups within the rear group changes when magnification is changed When the spacing of all the matching lens groups changes, and the front group includes at least three negative lenses and at least one positive lens, and the front group has a first lens with a meniscus shape and negative refractive power with its convex surface facing the object, and when the lens is in focus on an object at infinity at the wide-angle end, the sum of the distance along the optical axis from the lens surface on the object side of the front group to the lens surface on the image side of the rear group and the back focus in air equivalent distance of the entire system is TLw, the focal length of the entire system when the lens is in focus on an object at infinity at the wide-angle end is fw, the focal length of the entire system when the lens is in focus on an object at infinity at the telephoto end is ft, and the maximum half-angle of view when the lens is in focus 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 conditions (1) and (2) expressed by are satisfied.

[0007] A second aspect of this disclosure is, in the first aspect, when the open aperture F-number at the telephoto end with focus on an object at infinity is FNot, 1.5 <FNot / (ft / fw)<3 (3) This is a variable magnification optical system that satisfies the condition (3) expressed by .

[0008] A third aspect of this disclosure is, in the first or second aspect, when the focal length of the front group is fFw and the focal length of the middle group is fM when the lens is in focus on an object at infinity at the wide-angle end, 0.1<(-fFw) / fM<1.6 (4) which is a variable magnification optical system satisfying the conditional expression (4) represented by the above formula.

[0009] According to a fourth aspect of the present disclosure, in any one of the first to third aspects, when fFw is the focal length of the front group in a state focused on an object at infinity at the wide-angle end,[__END]] 0.6<(-fFw) / (fw×ft) 1 / 2 <1.3 (5) which is a variable magnification optical system satisfying the conditional expression (5) represented by the above formula.

[0010] According to a fifth aspect of the present disclosure, in any one of the first to fourth aspects, when fM is the focal length of the middle group,[__END]] 0.65<fM / (fw×ft) 1 / 2 <3.7 (6) which is a variable magnification optical system satisfying the conditional expression (6) represented by the above formula.

[0011] According to a sixth aspect of the present disclosure, in any one of the first to fifth aspects, when fL1 is the focal length of the first lens and fFw is the focal length of the front group in a state focused on an object at infinity at the wide-angle end,[__END]] 1<fL1 / fFw<3.5 (7) which is a variable magnification optical system satisfying the conditional expression (7) represented by the above formula.

[0012] According to a seventh aspect of the present disclosure, in any one of the first to sixth aspects, when fFw is the focal length of the front group in a state focused on an object at infinity at the wide-angle end, and FNot is the open F-number in a state focused on an object at infinity at the telephoto end,[__END]] 1.8<(-fFw) / (ft / FNot)<4 (8) which is a variable magnification optical system satisfying the conditional expression (8) represented by the above formula.

[0013] According to an eighth aspect of the present disclosure, in any one of the first to seventh aspects, when D1 is the center thickness of the first lens and FNot is the open F-number in a state focused on an object at infinity at the telephoto end,[__END]] 0.08 <D1 / (ft / FNot)<0.42 (9) This is a variable magnification optical system that satisfies the conditional equation (9) represented by .

[0014] The ninth aspect of this disclosure is, in any one of the first to eighth aspects, where ωw is the maximum half-angle of view when in focus on an object at infinity at the wide-angle end, and FNow is the maximum aperture F-number when in focus on an object at infinity at the wide-angle end, 0.3 <tanωw / FNow<0.47 (10) This is a variable magnification optical system that satisfies the conditional equation (10) represented by .

[0015] A tenth aspect of this disclosure is, in any one of the first to ninth aspects, where the horizontal magnification of the middle group when in focus on an object at infinity at the wide-angle end is βMw, and the horizontal magnification of the middle group when in focus on an object at infinity at the telephoto end is βMt, -4 < βMt / βMw < 3.5 (11) This is a variable magnification optical system that satisfies the conditional equation (11) represented by .

[0016] An eleventh aspect of this disclosure is, in any one of the first to tenth aspects, where the focal length of the rear group is fRw when in focus on an object at infinity at the wide-angle end, 0.15 < (fw × ft) 1 / 2 / |fRw|<1.1 (12) This is a variable magnification optical system that satisfies the conditional equation (12) represented by .

[0017] A twelfth aspect of this disclosure is, in any one of the first to eleventh aspects, when the lateral magnification of the image-side lens group of the rear group is βRrw when in focus on an object at infinity at the wide-angle end, -2 < βRrw < 3 (13) This is a variable magnification optical system that satisfies the conditional equation (13) represented by .

[0018] A thirteenth aspect of this disclosure is, in any one of the first to twelfth aspects, where DDFSTw is the distance along the optical axis from the lens surface closest to the object of the front group to the aperture diaphragm when in focus on an object at infinity at the wide-angle end, and fFw is the focal length of the front group when in focus on an object at infinity at the wide-angle end, 1.4 <DDFSTw / |fFw|<4 (14) This is a variable magnification optical system that satisfies the conditional equation (14) represented by .

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

[0020] A 15th aspect of this disclosure is, in any one of the 1st to 14th aspects, where DDFSTw is the distance along the optical axis from the lens surface closest to the object of the front group to the aperture diaphragm when in focus on an object at infinity at the wide-angle end, and ωw is the maximum half-angle of view when in focus on an object at infinity at the wide-angle end, 5 <DDFSTw / {(fw×tanωw)×log(ft / fw)}<10 (16) This is a variable magnification optical system that satisfies the conditional equation (16) represented by .

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

[0022] A 17th aspect of this disclosure is, in any one of the 1 to 16 aspects, where DDFSTw is the distance along the optical axis from the lens surface closest to the object in the front group to the aperture diaphragm when in focus on an object at infinity at the wide-angle end, 0.3 <DDFSTw / TLw<0.7 (18) This is a variable magnification optical system that satisfies the conditional equation (18) represented by .

[0023] The eighteenth aspect of this disclosure is, in any one of the first to seventeenth aspects, when the back focus of the entire system in terms of air-equivalent distance is Bfw when in focus on an object at infinity at the wide-angle end, 0.08 <Bfw / TLw<0.27 (19) This is a variable magnification optical system that satisfies the conditional equation (19) represented by .

[0024] A 19th aspect of this disclosure is, in any one of the first to 18th aspects, when the system is in focus on an object at infinity at the wide-angle end, and Expw is the sum of the distance along the optical axis from the paraxial exit pupil position to the image-side lens surface of the rear group and the back focus in air equivalent distance for the entire system, 0.28 <fw / Expw<0.65 (20) This is a variable magnification optical system that satisfies the conditional equation (20) represented by .

[0025] A 20th aspect of this disclosure is, in any one of the first to 19 aspects, 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, 1.5 < (Rf + Rr) / (Rf - Rr) < 4.2 (21) This is a variable magnification optical system that satisfies the conditional equation (21) represented by .

[0026] A 21st aspect of this disclosure is, in any one of the first to 20 aspects, where νRpave is the average value of the d-line reference Abbe numbers of all positive lenses in the rear group, 40 < νRpave < 90 (22) This is a variable magnification optical system that satisfies the conditional equation (22) represented by .

[0027] A 22nd aspect of this disclosure is a method in which, in any one of the first to 21st aspects, the difference in the optical axis direction between the position of the middle group when in focus on an object at infinity at the wide-angle end and the position of the middle group when in focus on an object at infinity at the telephoto end is defined as DMwt, the sign of DMwt is positive if the position of the middle group when in focus on an object at infinity at the telephoto end is closer to the image than the position of the middle group when in focus on an object at infinity at the wide-angle end, and negative if the position of the middle group when in focus on an object at infinity at the telephoto end is closer to the object than the position of the middle group when in focus on an object at infinity at the wide-angle end, and the unit of DMwt is millimeters, -0.2 < (ft / fw) / DMwt < -0.04 (23) This is a variable magnification optical system that satisfies the conditional equation (23) represented by .

[0028] A 23rd aspect of this disclosure is, in any one of the first to 22 aspects, where the refractive index of the first lens with respect to the d line is NL1, and the refractive index of the second negative lens from the object side in the front group with respect to the d line is NLn2, 1.58 < (NL1 + NLn2) / 2 < 2.2 (24) This is a variable magnification optical system that satisfies the conditional equation (24) represented by .

[0029] A 24th aspect of this disclosure is configured such that in any one of the first to 23 aspects, the image-side surface of the lens with the strongest positive refractive power in the rear group is convex, and the focal length of the lens with the strongest positive refractive power in the rear group is fRLp, and the focal length of the rear group when in focus on an object at infinity at the wide-angle end is fRw, -10 <fRw / fRLp<5 (25) This is a variable magnification optical system that satisfies the conditional equation (25) represented by .

[0030] A 25th aspect of this disclosure is a variable magnification optical system in which, in the 24th aspect, the lens with the strongest positive refractive power in the rear group is a biconvex lens.

[0031] A 26th aspect of this disclosure is, in any one of the first to 25 aspects, where the effective diameter of the lens surface closest to the object in the front group is EDf and the effective diameter of the lens surface closest to the image in the rear group is EDr, 1.1 <EDf / EDr<2.1 (26) This is a variable magnification optical system that satisfies the conditional equation (26) represented by .

[0032] A 27th aspect of this disclosure is, in any one of the first to 26 aspects, where the effective diameter of the lens surface closest to the object in the front group is EDf, 0.2 <EDf / TLw<0.45 (27) This is a variable magnification optical system that satisfies the conditional equation (27) represented by .

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

[0034] A 29th aspect of this disclosure, in the 28th aspect, is a variable magnification optical system comprising one negative lens and one positive lens.

[0035] A 30th aspect of the present disclosure, in the 29th aspect, is a variable magnification optical system in which the focusing group consists of a cemented lens formed by joining one negative lens and one positive lens.

[0036] A 31st aspect of this disclosure, in a 28th aspect, is a variable magnification optical system consisting of a single lens.

[0037] A 32nd aspect of this disclosure is a variable magnification optical system in which, in any one of the first to 28 aspects, there is only one focusing group that moves along the optical axis when focusing, and the focusing group is located in the rear group.

[0038] A 33rd aspect of this disclosure is a variable magnification optical system in any one of the first to 28 aspects, wherein the front group consists of a single lens group that moves during magnification.

[0039] A 34th aspect of this disclosure is a variable magnification optical system that is a zoom lens, wherein, in any one of the first to 28 aspects, the lens group closest to the object in the front group is fixed with respect to the image plane during magnification.

[0040] A 35th aspect of this disclosure is a variable magnification optical system in any one of the first to 28 aspects, which includes at least two cemented lenses, each consisting of one positive lens and one negative lens, on the image side of the front group.

[0041] A 36th aspect of the present disclosure is a variable magnification optical system in any one of the first to 28 aspects, wherein at least one of the middle group and the rear group includes a composite aspherical lens in which a resin having an aspherical air contact surface is formed on the spherical surface of a glass lens.

[0042] A 37th aspect of this disclosure is, in any one of the first to 28 aspects, where νLn3 is the d-line reference Abbe number of the third negative lens from the object side among the negative lenses in the front group, 50 < νLn3 < 95 (28) This is a variable magnification optical system that satisfies the conditional equation (28) represented by .

[0043] A 38th aspect of the present disclosure is a variable magnification optical system in any one of the first to 28 aspects, wherein the rear group of lenses closest to the object has a positive refractive power.

[0044] A 39th aspect of this disclosure is a variable magnification optical system in which the rear group consists of a single lens group having a positive refractive power and moving during magnification.

[0045] A forty-thorough aspect of this disclosure, in a third aspect, is a variable magnification optical system in which the front group consists of a single lens group that moves during magnification.

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

[0049] A forty-fourth aspect of this disclosure is a variable magnification optical system in which, in the forty-third aspect, all lens groups in the rear group move during magnification.

[0050] A forty-fifth aspect of this disclosure is a variable magnification optical system in which the front group consists of a single lens group that moves during magnification, in the forty-third or forty-fourth aspect.

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

[0052] A forty-seventh aspect of the present disclosure is a variable magnification optical system in which, in the forty-sixth 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 forty-eighth aspect of this disclosure includes, in any one of the forty-third to forty-seventh aspects, a focusing group that moves along the optical axis when focusing, wherein the focusing group is a variable magnification optical system consisting of a single lens.

[0054] A forty-ninth aspect of this disclosure is a variable magnification optical system in which, in the third-eighth aspect, the rear group consists of, in order from the object side to the image side, a group of lenses having a positive refractive power, a group of lenses having a positive refractive power, and a group of lenses having a negative refractive power.

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

[0056] A 51st aspect of this disclosure is a variable magnification optical system in which the front group consists of a single lens group that moves during magnification, in the 49th or 50th aspect.

[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 negative refractive power and a meniscus shape with a convex surface facing the object side, a third lens having a negative refractive power and a concave surface facing the image side, and a fourth lens having a positive refractive power and a convex surface facing the object side.

[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 this disclosure, in the 38th aspect, is a variable magnification optical system in which the rear group consists of, in order from the object side to the image side, a lens group having a positive refractive power, a lens group having a negative refractive power, and a lens group having a positive refractive power.

[0060] A 55th aspect of this disclosure is a variable magnification optical system in which, in the 54th aspect, all lens groups in the rear group move during magnification.

[0061] A 56th aspect of this disclosure is a variable magnification optical system in which, in the 54th aspect, the lens group closest to the image in the rear group is fixed with respect to the image plane during magnification.

[0062] A fiftieth aspect of the present disclosure is a variable magnification optical system in any one of the fiftieth to fiftieth aspects, wherein the front group consists of a single lens group that moves during magnification.

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

[0064] A 59th aspect of this disclosure is a variable magnification optical system which is a zoom lens, wherein, during magnification, the lens group closest to the object in the front group is fixed with respect 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, in which the front group includes, in order from the object side to the image side, a first lens, a second lens having a negative refractive power and a meniscus shape with a convex surface facing the object side, a third lens having a negative refractive power and a concave surface facing the image side, and a fourth lens having a positive refractive power and a convex surface facing the object side.

[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 a variable magnification optical system in any one of the 54th to 61st aspects, wherein the rear group includes a focusing group that moves along the optical axis when focusing, and the focusing group consists of two or fewer lenses.

[0068] A 63rd aspect of this disclosure, in the 62nd aspect, is a variable magnification optical system comprising a single negative lens in the focusing group.

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

[0070] A 65th aspect of this disclosure is a variable magnification optical system in which, in the 64th aspect, all lens groups in the rear group move during magnification.

[0071] A 66th aspect of this disclosure is a variable magnification optical system in which the front group consists of a single lens group that moves during magnification, in the 64th or 65th aspect.

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

[0073] A 68th aspect of this disclosure is a variable magnification optical system which is a zoom lens, wherein, during magnification, the lens group closest to the object in the front group is fixed with respect 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, in which the front group includes, in order from the object side to the image side, a first lens, a second lens having a negative refractive power and a meniscus shape with a convex surface facing the object side, a third lens having a negative refractive power and a concave surface facing the image side, and a fourth lens having a 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 a variable magnification optical system in any one of the first to 37 aspects, wherein the rear group of lenses closest to the object has a negative refractive power.

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

[0078] A 73rd aspect of this disclosure is a variable magnification optical system in which, in the 72nd aspect, all lens groups in the rear group move during magnification.

[0079] A 74th aspect of this disclosure is a variable magnification optical system in which the front group consists of a single lens group that moves during magnification, as described in the 72nd or 73rd aspect.

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

[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 includes, in any one of the 72nd to 76th aspects, a focusing group that moves along the optical axis when focusing, wherein the focusing group is a variable magnification optical system consisting of a cemented lens comprising one positive lens and one negative lens.

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

[0084] A 79th aspect of this disclosure is a variable magnification optical system in which, in the 78th aspect, all lens groups in the rear group move during magnification.

[0085] An 80th aspect of the present disclosure, in an aspect 78 or 79, is a variable magnification optical system in which the front group consists of one lens group that moves during magnification.

[0086] An 81st aspect of the present disclosure is a variable magnification optical system in any one of the 78th to 80th aspects, in which the front group includes, in order from the object side to the image side, a first lens, a second lens having a negative refractive power and a meniscus shape with a convex surface facing the object side, a third lens having a negative refractive power and a concave surface facing the image side, and a fourth lens having a 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 includes, in any one of the 78th to 82nd aspects, a focusing group that moves along the optical axis when focusing, wherein the focusing group is a variable magnification optical system consisting of a cemented lens comprising one positive lens and one negative lens.

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

[0090] An eighty-fifth aspect of this disclosure is a variable magnification optical system in which, in the eighty-fourth aspect, all lens groups in the rear group move during magnification.

[0091] An 86th aspect of this disclosure is a variable magnification optical system in which the front group consists of a single lens group that moves during magnification, in an 84th or 85th aspect.

[0092] An 87th aspect of the present disclosure is a variable magnification optical system in any one of the 84th to 86th aspects, in which the front group includes, in order from the object side to the image side, a first lens, a second lens having a negative refractive power and a meniscus shape with a convex surface facing the object side, a third lens having a negative refractive power and a concave surface facing the image side, and a fourth lens having a 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 includes, in any one of the 84th to 88th aspects, a focusing group that moves along the optical axis when focusing, wherein the focusing group is a variable magnification optical system consisting of a cemented lens comprising one positive lens and one negative lens.

[0095] A 90th aspect of the present disclosure, in a 71st aspect, is a variable magnification optical system in which the rear group consists 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 91st aspect of this disclosure is a variable magnification optical system in which, in a 90th aspect, all lens groups in the rear group move during magnification.

[0097] A 92nd aspect of the present disclosure is a variable magnification optical system in which the front group consists of a single lens group that moves during magnification.

[0098] A 93rd aspect of the present disclosure is a variable magnification optical system in any one of the 90th to 92nd aspects, in which the front group includes, in order from the object side to the image side, a first lens, a second lens having a negative refractive power and a meniscus shape with a convex surface facing the object side, a third lens having a negative refractive power and a concave surface facing the image side, and a fourth lens having a 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 includes, in any one of the 90th to 94th aspects, a focusing group that moves along the optical axis when focusing, wherein the focusing group is a variable magnification optical system consisting of a cemented lens comprising one positive lens and one negative lens.

[0101] A 96th aspect of this disclosure, in a 71st aspect, is a variable magnification optical system in which the rear group consists 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 this disclosure is a variable magnification optical system in which, in the 96th aspect, all lens groups in the rear group move during magnification.

[0103] A 98th aspect of the present disclosure is a variable magnification optical system in which the front group consists of a single lens group that moves during magnification, as described in the 96th or 97th aspect.

[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 negative refractive power and a meniscus shape with a convex surface facing the object side, a third lens having a negative refractive power and a concave surface facing the image side, and a fourth lens having a positive refractive power and a convex surface facing the object side.

[0105] A hundredth aspect of the present disclosure is a variable magnification optical system in which, in the ninth 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 includes, in any one of the 96th to 100th aspects, a focusing group that moves along the optical axis when focusing, wherein the focusing group is a variable magnification optical system consisting of a cemented lens comprising one positive lens and one negative lens.

[0107] A 102nd aspect of this disclosure is an imaging device comprising a variable magnification optical system of any one of the first to 101 aspects.

[0108] Furthermore, the terms "~consisting of" and "~consisting of" in this specification are intended to include, in addition to the listed components, lenses that substantially have no refractive power, optical elements other than lenses such as apertures, filters, and cover glass, 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 "a lens group having positive refractive power" mean that the group as a whole has positive refractive power. Similarly, "a lens group having negative refractive power" and "a lens group having negative refractive power" mean that the 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, "lens groups" such as "first lens group," "front group," "middle group," "rear group," and "focusing group" are not limited to configurations consisting of multiple lenses, but may also consist of only one lens.

[0110] For lenses including aspherical surfaces, the radius of curvature, the sign of the refractive power, and the surface shape shall be those of the paraxial region unless otherwise specified. The sign of the radius of curvature shall be positive for surfaces with a convex shape facing the object, and negative for surfaces with a convex shape facing the image.

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

[0112] According to this disclosure, it is possible to provide a variable magnification optical system that has a wide field of view, is miniaturized, and maintains good optical performance, as well as an imaging device equipped with this variable magnification optical system. [Brief explanation of the drawing]

[0113] [Figure 1] This figure corresponds to the magnification optical system of Example 1 and shows a cross-sectional view and movement direction of the configuration of the magnification optical system according to one embodiment. [Figure 2] Figure 1 shows the configuration of the variable magnification optical system and a cross-sectional view of the light beam. [Figure 3] This diagram explains the symbols used in each conditional expression. [Figure 4] This is a diagram to explain the effective diameter. [Figure 5] These are aberration diagrams for the variable magnification optical system of Example 1. [Figure 6] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 2. [Figure 7] These are aberration diagrams for the variable magnification optical system of Example 2. [Figure 8] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 3. [Figure 9] These are aberration diagrams for the variable magnification optical system of Example 3. [Figure 10] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 4. [Figure 11]These are aberration diagrams for the variable magnification optical system of Example 4. [Figure 12] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 5. [Figure 13] These are aberration diagrams for the variable magnification optical system of Example 5. [Figure 14] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 6. [Figure 15] These are aberration diagrams for the variable magnification optical system of Example 6. [Figure 16] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 7. [Figure 17] These are aberration diagrams for the variable magnification optical system of Example 7. [Figure 18] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 8. [Figure 19] These are aberration diagrams for the variable magnification optical system of Example 8. [Figure 20] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 9. [Figure 21] These are aberration diagrams for the variable magnification optical system of Example 9. [Figure 22] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 10. [Figure 23] These are aberration diagrams for the variable magnification optical system of Example 10. [Figure 24] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 11. [Figure 25] These are aberration diagrams for the variable magnification optical system of Example 11. [Figure 26] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 12. [Figure 27] These are aberration diagrams for the variable magnification optical system of Example 12. [Figure 28] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 13. [Figure 29] These are aberration diagrams for the variable magnification optical system of Example 13. [Figure 30] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 14. [Figure 31] These are aberration diagrams for the variable magnification optical system of Example 14. [Figure 32] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 15. [Figure 33] These are aberration diagrams for the variable magnification optical system of Example 15. [Figure 34] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 16. [Figure 35] These are aberration diagrams for the variable magnification optical system of Example 16. [Figure 36] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 17. [Figure 37] These are aberration diagrams for the variable magnification optical system of Example 17. [Figure 38] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 18. [Figure 39] These are aberration diagrams for the variable magnification optical system of Example 18. [Figure 40] This figure shows a cross-sectional view and movement direction of the variable magnification optical system configuration of Example 19. [Figure 41] These are aberration diagrams for the variable magnification optical system of Example 19. [Figure 42] This is a front perspective view of an imaging device according to one embodiment. [Figure 43] This is a perspective view of the rear side of an imaging device according to one embodiment. [Modes for carrying out the invention]

[0114] Embodiments of this disclosure will be described below with reference to the drawings.

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

[0116] In Figure 2, the luminous beams are shown as follows: the top row shows the on-axial luminous beam wa and the luminous beam wb with the maximum half-angle of view ωw; the middle row shows the on-axial luminous beam ma and the luminous beam mb with the maximum half-angle of view ωm; and the bottom row shows the on-axial luminous beam ta and the luminous beam tb with the maximum half-angle of view ωt. The examples shown in Figures 1 and 2 correspond to the variable magnification optical system of Example 1 described later. In Figures 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 this disclosure consists of a front group GF, a middle group GM, and a rear group GR, arranged in order from the object side to the image side along the optical axis Z. The front group GF consists of two or fewer lens groups and has a negative refractive power as a whole throughout the entire magnification range. The middle group GM contains only one lens group that has a positive refractive power as a lens group. That is, the middle group GM contains only one lens group. The rear group GR consists of three or fewer lens groups. An aperture diaphragm St is positioned between the lens surface closest to the image in the front group GF and the lens surface closest to the object in the rear group GR.

[0118] In this specification, a "lens group" is a component of a variable magnification optical system, comprising at least one lens, separated by an air gap that changes during magnification. During magnification, each lens group is moved or fixed, and the inter-lens spacing 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 itself does not change. Note that a "lens group" may also include components other than lenses that do not have refractive power, such as an aperture diaphragm St.

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

[0120] Having the front lens group GF, which is closest to the object, have a negative refractive power makes it easy to achieve a wide angle of view at the wide-angle end. Placing the middle lens group GM, which has a positive refractive power, on the image side of the front lens group GF, and placing the rear lens group GR on the image side of the middle lens group GM makes it easy to realize a high-performance optical system while maintaining miniaturization. Placing the aperture diaphragm St between the lens surface closest to the image of the front lens group GF and the lens surface closest to the object of the rear lens group GR makes it possible to miniaturize the aperture unit, which is also advantageous for miniaturizing the entire lens system.

[0121] As an example, the variable magnification optical system in Figure 1 consists of a first lens group G1, a second lens group G2, and a third lens group G3, in order from the object side to the image side. As an example, each lens group in Figure 1 is configured as follows: 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, and an aperture diaphragm St, in order from the object side to the image side. The third lens group G3 consists of five lenses, L31 to L35, in order from the object side to the image side. Note that the aperture diaphragm St in Figure 1 does not represent its shape or size, but rather its position in the optical axis direction. This method of illustrating the aperture diaphragm St is the same in other figures as well.

[0122] In the example in Figure 1, during magnification, the first lens group G1, the second lens group G2, and the third lens group G3 move along the optical axis Z by changing the spacing between adjacent lens groups. The diagonal arrows between the top and middle sections of Figure 1 schematically show the direction of movement of each lens group when magnifying from the wide-angle end to the intermediate focal length state. The diagonal arrows between the middle and bottom sections of Figure 1 schematically show the direction of movement of each lens group when magnifying from the intermediate focal length state to the telephoto end. In the example in 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] The example shown in Figure 1 is just one example, and the variable magnification optical system of this disclosure can be modified in various ways without departing from the spirit of the art of this 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 differ from the example in Figure 1. Preferred and possible configurations of the variable magnification optical system of this disclosure are described below.

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

[0125] Alternatively, the front group GF may be configured to consist of two lens groups, one with negative refractive power and the other with positive refractive power, arranged in order from the object side to the image side. In this case, it is advantageous to obtain a high magnification ratio while suppressing aberration fluctuations during magnification.

[0126] The variable magnification optical system of this 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 with respect to the image plane Sim during magnification. In this case, the number of lens groups that move during magnification can be reduced, making it less susceptible to the effects of eccentricity, and the configuration of the lens frame can be simplified. Furthermore, since the overall length of the optical system remains constant during magnification, the change in the center of gravity of the optical system during magnification can be reduced, thereby improving convenience during shooting.

[0127] The front group GF preferably includes a first lens that is positioned closest to the object and has a meniscus shape with a convex surface facing the object, exhibiting negative refractive power. Furthermore, the front group GF preferably includes at least three negative lenses, including the first lens, and at least one positive lens. By making the first lens, which is the negative lens closest to the object, a meniscus shape with a convex surface facing the object, the refraction angle of the light beam incident on this first lens can be reduced, which is advantageous for correcting image field curvature and the like. By arranging three or more negative lenses in the front group GF, the negative refractive power of the front group GF can be increased, which is advantageous for widening the angle of view at the wide-angle end. By arranging at least one positive lens in the front group GF, the diameter of the light beam incident from the front group GF to the middle group GM can be reduced, which is advantageous for miniaturization. In the example in Figure 1, lens L11 corresponds to the first lens.

[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 with a meniscus shape and negative refractive power with a convex surface facing the object side, a third lens with negative refractive power with a concave surface facing the image side, and a fourth lens with positive refractive power with a convex surface facing the object side. In this case, correction of image field curvature, widening of the field of view at the wide-angle end, and miniaturization are more advantageous. In the example in Figure 1, lenses L12, L13, and L14 correspond to the second lens, third lens, and fourth lens, respectively. The front group GF may be configured to consist of the four lenses described above, from the first to the fourth lens. Alternatively, the front group GF may be configured to consist of a total of five lenses, including the four lenses described above, from the first to the fourth lens.

[0129] In this specification, "including ~ and ~ in order from the object side to the image side" refers to the inclusion of components in a continuous or discontinuous manner. For example, "including A and B in order from the object side to the image side" may include A and B arranged continuously, or it may include A and B arranged discontinuously with another element placed between them.

[0130] When the front group GF includes the above-described first lens and second lens, the first lens may be configured such that its object-side and image-side lens surfaces are spherical, and the second lens may be configured such that its object-side and image-side lens surfaces are aspherical. In optical systems with a wide angle of view, manufacturing costs can be reduced by making the first lens, which tends to be large in diameter, a spherical lens. Making the second lens an aspherical lens is advantageous in making the optical system smaller while suppressing aberrations at the wide-angle end.

[0131] The variable magnification optical system of this disclosure is preferably configured to include at least two cemented lenses, each consisting of one positive lens and one negative lens, on the image side of the front group GF. This configuration is advantageous in suppressing lateral chromatic aberration and axial chromatic aberration across the entire magnification range.

[0132] When magnification is applied, it is preferable to configure the lens group within the middle group to move. This configuration makes it easier to suppress aberration fluctuations during magnification, which is advantageous for improving performance.

[0133] The aperture diaphragm St may be positioned on the image side of the middle group GM, between two lens surfaces within the middle group, or on the object side of the rear group GR. The aperture diaphragm St may be configured to move integrally with adjacent lenses during magnification, or to move on a different trajectory from any of the lenses during magnification.

[0134] At least one of the middle group GM and the rear group GR may be configured to include a composite 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 keeping manufacturing costs down, thus enabling good correction of various aberrations while reducing costs. In this disclosure, the composite aspherical lens composed of the above resin and the above glass lens is not considered a bonded lens in which two lenses are joined together, but is treated as a single lens.

[0135] The lens group closest to the object in the rear GR group may be configured to have a positive refractive power. This configuration is particularly advantageous for suppressing spherical aberration at the telephoto end.

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

[0137] The rear lens group GR may be configured to consist of a single lens group that has positive refractive power and moves during magnification. In this case, the entire rear lens group moves as a whole during magnification, thus simplifying the mechanism for moving the lens group during magnification. Furthermore, having positive refractive power in the rear lens group GR is advantageous in suppressing spherical aberration, especially at the telephoto end.

[0138] Alternatively, the rear group GR may be configured to consist of a lens group with negative refractive power and another lens group with negative refractive power, in order from the object side to the image side. In this case, it becomes easier to suppress fluctuations in distortion aberration during magnification.

[0139] Alternatively, the rear group GR may include multiple lens groups, and these multiple lens groups may include both lens groups with positive refractive power and lens groups with negative refractive power. In this case, it becomes easier to suppress aberration fluctuations during magnification.

[0140] If the rear lens group GR consists of two lens groups, the rear lens group GR may be configured such that, from the object side to the image side, it consists of a lens group with positive refractive power and a lens group with negative refractive power. Alternatively, the rear lens group GR may be configured such that, from the object side to the image side, it consists of a lens group with negative refractive power and a lens group with positive refractive power.

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

[0142] The lens may be configured so that all lens groups within the rear group move during magnification. This configuration is advantageous for obtaining a high magnification ratio while suppressing aberration fluctuations during magnification.

[0143] Alternatively, during magnification, the lens group closest to the image plane (Sim) of the rear group GR may be configured to be fixed relative to the image plane. In this case, the mechanism for moving the lens group during magnification can be simplified.

[0144] The variable magnification optical system of this 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 achieved 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 lenses L31 and L32 in the upper part of Figure 1 indicate that the focusing group consists of lenses L31 and L32, and that when focusing from an object at infinity to a nearby object, this focusing group moves toward the object.

[0146] The focusing group is preferably included in the rear group GR. By placing the focusing group within the rear group, it becomes easier to reduce the diameter of the focusing group, thereby facilitating control of the focusing group.

[0147] The focusing group may be positioned closest to the object in the rear group GR. In this case, the focusing group can be easily miniaturized, 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 positioned in the second lens group from the object side within the rear group.

[0148] The focusing group preferably consists of two or fewer lenses. By reducing the number of lenses constituting the focusing group, the mechanism for controlling the focusing group can be simplified, and rapid focusing becomes easier.

[0149] The focusing group may be configured to consist of one negative lens and one positive lens. In this case, the negative and positive lenses within the focusing group can cancel out various aberrations, making it easier to suppress aberration fluctuations during focusing, which 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. In this case, it is possible to make it smaller compared to the case where it is not cemented. By making the focusing group smaller, the mechanism for controlling the focusing group can be simplified and rapid focusing can be easily achieved.

[0151] The focusing group may be configured to consist of a single lens. A "single lens" is a single lens that is not joined together. When the focusing group consists of a single lens, further miniaturization is possible compared to when the focusing group consists of two or more lenses. Miniaturization of the focusing group allows for a simpler mechanism for controlling the focusing group and facilitates rapid focusing.

[0152] The focusing group may be configured to consist of a single negative lens. In this case, further miniaturization is possible compared to when the focusing group consists of two or more lenses. Miniaturization of the 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 give the focusing group a strong refractive power, which is advantageous in suppressing the amount of movement of the focusing group during focusing.

[0153] The variable magnification optical system of this 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 is located in the rear group.

[0154] The preferred and possible configurations of the conditional formulas for the variable magnification optical system of this disclosure are described below. In the following explanation of the conditional formulas, the same symbols will be used for terms with the same definition, and some redundant explanations of symbols will be omitted to avoid redundant explanations. Also, in the following, to avoid redundant explanations, "the variable magnification optical system of this disclosure" will also be simply referred to as "the variable magnification optical system."

[0155] The variable magnification optical system preferably satisfies the following condition (1). Here, TLw is the sum of the distance along the optical axis from the lens surface closest to the object of the front group GF to the lens surface closest to the image of the rear group GR, when the system is in focus on an object at infinity at the wide-angle end, and the back focus Bfw in air equivalent distance for the entire system. Also, ft is the focal length of the entire system when the system is in focus on an object at infinity at the telephoto end, and ωt is the maximum half-angle of view when the system is in focus on an object at infinity at the telephoto end. TLw is the total length when the system is in focus on an object at infinity at the wide-angle end. In condition (1), tan is the tangent, and this notation is the same for other condition equations. Keeping the corresponding value in condition (1) above the lower limit is advantageous in suppressing various aberrations throughout the entire magnification range. Keeping the corresponding value in condition (1) above the upper limit is advantageous in miniaturizing the entire optical system. To obtain better characteristics, the variable magnification optical system is more preferably satisfied with the following condition (1-1), and even more preferably satisfied with the following condition (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, Figure 3 shows the back focus Bfw and total length TLw of the entire system in air equivalent distance when the variable magnification optical system of Figure 1 is focused on an object at infinity at its wide-angle end. "Back focus" is the distance along the optical axis from the image-side lens surface to the image plane Sim of the variable magnification optical system. As in the example in Figure 3, if no components are placed between the image-side lens surface and the image plane Sim of the variable magnification optical system, the geometric length from the image-side lens surface to the image plane Sim is equal to the back focus Bfw in air equivalent distance. However, unlike the example in Figure 3, if components such as filters or cover glass are placed between the image-side lens surface and the image plane Sim of the variable magnification optical system, the geometric length from the image-side lens surface to the image plane Sim is different from the back focus Bfw in air equivalent distance. Therefore, the back focus Bfw is calculated by air equivalent to the thickness of the component along the optical axis.

[0157] When the focal length of the entire system is fw when focused on an object at infinity at the wide-angle end, it is preferable that the variable magnification optical system satisfies the following condition (2). By ensuring that the corresponding value of condition (2) does not fall below the lower limit, it is advantageous to suppress various aberrations throughout the entire magnification range. By ensuring that the corresponding value of condition (2) does not exceed the upper limit, it is advantageous to miniaturize the entire optical system or to obtain a sufficient magnification ratio for the variable magnification optical system. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (2-1), and even more preferable that it satisfies the following condition (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] When the maximum aperture F-number at the telephoto end, when focused on an object at infinity, is denoted as FNot, it is preferable that the variable magnification optical system satisfies the following condition (3). In condition (3), ft / fw is the maximum magnification ratio. Ensuring that the corresponding value in condition (3) does not fall below the lower limit is advantageous for miniaturizing the entire optical system, or particularly advantageous for suppressing various aberrations at the telephoto end. Ensuring that the corresponding value in condition (3) does not exceed the upper limit makes it easier to obtain sufficient brightness at the telephoto end. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (3-1), and even more preferable that it satisfies the following condition (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 is fFw and the focal length of the middle group GM is fM in a state where the lens is focused on an object at infinity at the wide-angle end, it is preferable that the variable magnification optical system satisfies the following condition (4). By ensuring that the corresponding value of condition (4) does not fall below the lower limit, the refractive power of the middle group GM does not become too weak, which is advantageous in correcting spherical aberration, especially at the telephoto end. By ensuring that the corresponding value of condition (4) does not exceed the upper limit, the refractive power of the front group GF does not become too weak, which makes it easier to suppress the enlargement of the front group GF, and also makes it easier to suppress the amount of movement of the front group GF during magnification if the front group GF moves during magnification. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (4-1), and even more preferable that it satisfies the following condition (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 satisfies the following conditional expression (5). By preventing the corresponding value of conditional expression (5) from falling below the lower limit, the refractive power of the front group GF does not become excessively large, which is advantageous for suppressing aberration fluctuation during zooming. By preventing the corresponding value of conditional expression (5) from exceeding the upper limit, the refractive power of the front group GF does not become excessively weak, which makes it easy to suppress an increase in size of the front group GF, and also makes it easy to suppress the movement amount of the front group GF during zooming when the front group GF moves during zooming. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional expression (5-1), and it is even more preferable that the variable magnification optical system satisfies 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 satisfies the following conditional expression (6). By preventing the corresponding value of conditional expression (6) from falling below the lower limit, the refractive power of the middle group GM does not become excessively large, so that field curvature generated in the middle group GM can be suppressed, which is advantageous for aberration correction during zooming. By preventing the corresponding value of conditional expression (6) from exceeding the upper limit, the refractive power of the middle group GM does not become excessively weak, so that the movement amount of the middle group GM during zooming can be suppressed, which is advantageous for shortening the total length of the optical system. In order to obtain better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional expression (6-1), and it is even more preferable that the variable magnification optical system satisfies 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 where the front group GF includes the first lens described above, when the focal length of the first lens is fL1, it is preferable that the variable magnification optical system satisfies the following conditional equation (7). By ensuring that the corresponding value of conditional equation (7) does not fall below the lower limit, the refractive power of the first lens does not become too strong, making it easier to suppress higher-order aberrations at the telephoto end. Alternatively, by ensuring that the corresponding value of conditional equation (7) does not fall below the lower limit, the refractive power of the front group GF does not become too weak, making it easier to suppress the enlargement of the front group GF, thus being advantageous for miniaturizing the front group GF. In this specification, "higher-order aberration" means aberration of the fifth order or higher. By ensuring that the corresponding value of conditional equation (7) does not exceed the upper limit, the refractive power of the front group GF does not become too strong, which is advantageous for suppressing aberration fluctuations during magnification. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional equation (7-1), and even more preferable that it satisfies the following conditional equation (7-2). 1 <fL1 / fFw<3.5 (7) 1.1 <fL1 / fFw<3.2 (7-1) 1.2 <fL1 / fFw<3 (7-2)

[0163] When the maximum aperture F-number at the telephoto end, when focused on an object at infinity, is denoted as FNot, it is preferable that the variable magnification optical system satisfies the following condition (8). Ensuring that the corresponding value in condition (8) does not fall below the lower limit is advantageous for improving performance. Ensuring that the corresponding value in condition (8) does not exceed the upper limit prevents the refractive power of the front group GF from becoming too weak, making it easier to suppress the enlargement of the front group GF, thus advantageous for miniaturizing the front group GF. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (8-1), and even more preferable that it satisfies the following condition (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 where the front group GF includes the first lens described above, if the center thickness of the first lens is D1, it is preferable that the variable magnification optical system satisfies the following condition (9). By ensuring that the corresponding value of condition (9) does not fall below the lower limit, it becomes easier to ensure the mechanical strength of the first lens. By ensuring that the corresponding value of condition (9) does not exceed the upper limit, it is advantageous to reduce the weight of the first lens. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (9-1), and even more preferable that it satisfies the following condition (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 ωw is the maximum half-angle of view when in focus on an object at infinity at the wide-angle end, and FNow is the maximum aperture F-number when in focus on an object at infinity at the wide-angle end, then it is preferable that the variable magnification optical system satisfies the following condition (10). By ensuring that the corresponding value in condition (10) does not fall below the lower limit, it becomes easier to widen the angle of view at the wide-angle end while decreasing the maximum aperture F-number at the wide-angle end. By ensuring that the corresponding value in condition (10) does not exceed the upper limit, it becomes easier to suppress the increase in the number of lenses and the increase in the size of the optical system while obtaining good optical performance. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (10-1), and even more preferable that it satisfies the following condition (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] When the lateral magnification of the middle group GM in the state where it is focused on an object at infinity at the wide-angle end is βMw, and the lateral magnification of the middle group GM in the state where it is focused on an object at infinity at the telephoto end is βMt, it is preferable that the variable magnification optical system satisfies the following condition (11). By ensuring that the corresponding value of condition (11) does not fall below the lower limit, it is advantageous to achieve a high magnification ratio. By ensuring that the corresponding value of condition (11) does not exceed the upper limit, it is advantageous to suppress aberration fluctuations during magnification. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (11-1), and even more preferable that it satisfies the following condition (11-2). -4 < βMt / βMw < 3.5 (11) -3.5 < βMt / βMw < 3 (11-1) -3 < βMt / βMw < 2.5 (11-2)

[0167] When the focal length of the rear group GR is fRw in the state where it is focused on an object at infinity at the wide-angle end, it is preferable that the variable magnification optical system satisfies the following condition (12). By ensuring that the corresponding value of condition (12) does not fall below the lower limit, it is advantageous to suppress various aberrations throughout the entire magnification range. By ensuring that the corresponding value of condition (12) does not exceed the upper limit, it is advantageous to suppress the sensitivity of the rear group GR to errors. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (12-1), and even more preferable that it satisfies the following condition (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] When the lateral magnification of the image-side lens group of the rear group GR is focused on an object at infinity at the wide-angle end, βRrw is the preferred condition of the variable magnification optical system to satisfy the following condition (13). Ensuring that the corresponding value of condition (13) does not fall below the lower limit is advantageous for achieving a high magnification ratio. Ensuring that the corresponding value of condition (13) does not exceed the upper limit is advantageous for suppressing aberrations across the entire magnification range. To obtain even better characteristics, it is more preferable for the variable magnification optical system to satisfy the following condition (13-1), and even more preferable to satisfy the following condition (13-2). -2 < βRrw < 3 (13) -1 < βRrw < 2.75 (13-1) -0.5 < βRrw < 2.5 (13-2)

[0169] When the lens is focused on an object at infinity at the wide-angle end, and DDFSTw is the distance along the optical axis from the lens surface closest to the object of the front group GF to the aperture diaphragm St, it is preferable that the variable magnification optical system satisfies the following condition (14). As an example, Figure 3 shows the distance DDFSTw defined above for the variable magnification optical system of Figure 1. By ensuring that the corresponding value of condition (14) does not fall below the lower limit, the distance from the lens surface closest to the object of the front group GF to the aperture diaphragm St does not become too short, so the range of motion of the middle group GM does not become too small, which is advantageous for achieving a high magnification ratio. Alternatively, by ensuring that the corresponding value of condition (14) does not fall below the lower limit, the refractive power of the front group GF does not become too weak, which is advantageous for achieving both miniaturization and a high magnification ratio. By ensuring that the corresponding value in condition (14) does not exceed the upper limit, the distance from the lens surface closest to the object of the front group GF to the entrance pupil position at the wide-angle end does not become too long, thus suppressing the increase in diameter of the front group GF, and thereby facilitating miniaturization. Alternatively, by ensuring that the corresponding value in condition (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. To obtain even better characteristics, it is more preferable for the variable magnification optical system to satisfy the following condition (14-1), and even more preferable to satisfy the following condition (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] The variable magnification optical system preferably satisfies the following condition (15). Here, Enpw is the distance along the optical axis from the lens surface closest to the object of the front group GF to the paraxial entrance pupil position Pen when the system is in focus on an object at infinity at the wide-angle end. As an example, Figure 3 shows the paraxial entrance pupil position Pen and the distance Enpw defined above when the variable magnification optical system of Figure 1 is in focus 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 on the object side of the lens surface closest to the object of the front group GF, and positive if the paraxial entrance pupil position Pen is on the image side of the lens surface closest to the object of the front group GF. By ensuring that the corresponding value of condition (15) does not fall below the lower limit, the distance from the lens surface closest to the object of the front group GF 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. By ensuring that the corresponding value in condition (15) does not exceed the upper limit, the distance from the lens surface closest to the object of the front group GF to the paraxial entrance pupil position Pen at the wide-angle end does not become too long, thus suppressing the increase in diameter of the front group GF, and thereby facilitating miniaturization. To obtain even better characteristics, it is more preferable for the variable magnification optical system to satisfy the following condition (15-1), and even more preferable to satisfy the following condition (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] The variable magnification optical system preferably satisfies the following condition (16). By ensuring that the corresponding value of condition (16) does not fall below the lower limit, the distance from the lens surface closest to the object of the front group GF to the entrance pupil position at the wide-angle end does not become too short, making it easier to suppress aberration fluctuations during magnification. By ensuring that the corresponding value of condition (16) does not exceed the upper limit, the distance from the lens surface closest to the object of the front group GF to the entrance pupil position at the wide-angle end does not become too long, thus suppressing the increase in diameter of the front group GF, and thereby making miniaturization easier. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (16-1), and even more preferable that it satisfies the following condition (16-2). 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] The variable magnification optical system preferably satisfies the following condition (17). By ensuring that the corresponding value of condition (17) does not fall below the lower limit, the distance from the lens surface closest to the object of the front group GF 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. By ensuring that the corresponding value of condition (17) does not exceed the upper limit, the distance from the lens surface closest to the object of the front group GF to the paraxial entrance pupil position Pen at the wide-angle end does not become too long, thus suppressing the increase in diameter of the front group GF, and thereby making miniaturization easier. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (17-1), and even more preferable that it satisfies the following condition (17-2). 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] The variable magnification optical system preferably satisfies the following condition (18). By ensuring that the corresponding value of condition (18) does not fall below the lower limit, the distance from the lens surface closest to the object of the front group GF to the entrance pupil position at the wide-angle end does not become too short, making it easier to suppress aberration fluctuations during magnification. By ensuring that the corresponding value of condition (18) does not exceed the upper limit, the distance from the lens surface closest to the object of the front group GF to the entrance pupil position at the wide-angle end does not become too long, thus suppressing the increase in diameter of the front group GF, and thereby making miniaturization easier. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (18-1), and even more preferable that it satisfies the following condition (18-2). 0.3 <DDFSTw / TLw<0.7 (18) 0.38 <DDFSTw / TLw<0.6 (18-1) 0.43 <DDFSTw / TLw<0.5 (18-2)

[0174] When the back focus of the entire system in air equivalent distance when focused on an object at infinity at the wide-angle end is defined as Bfw, it is preferable that the variable magnification optical system satisfies the following condition (19). By ensuring that the corresponding value of condition (19) does not fall below the lower limit, the back focus Bfw defined above does not become too short, making it easier to attach the mount exchange mechanism. By ensuring that the corresponding value of condition (19) does not exceed the upper limit, the back focus Bfw defined above does not become too long, making it easier to miniaturize. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (19-1), and even more preferable that it satisfies the following condition (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] The variable magnification optical system preferably satisfies the following condition (20). Here, Expw is defined as the sum of the distance along the optical axis from the paraxial exit pupil position Pex to the image-side lens surface of the rear group GR when the system is in focus on an object at infinity at the wide-angle end, and the back focus Bfw in air equivalent distance for the entire system. As an example, Figure 3 shows the paraxial exit pupil position Pex and the distance Expw defined above when the variable magnification optical system of Figure 1 is in focus 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 on the object side of the image plane Sim, and negative if the paraxial exit pupil position Pex is on the image side of the image plane Sim. By ensuring that the corresponding value of condition (20) does not fall below the lower limit, it becomes easier to shorten the overall length of the optical system, which is advantageous for miniaturization. By ensuring that the corresponding value in condition (20) does not exceed the upper limit, it becomes easier to reduce the incident angle of the off-axis principal rays on the image plane Sim, which is advantageous for securing peripheral light intensity. To obtain even better characteristics, it is more preferable for the variable magnification optical system to satisfy the following condition (20-1), and even more preferable to satisfy the following condition (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 where the front group GF includes the first lens described above, if 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 satisfies the following conditional equation (21). By ensuring that the corresponding value of conditional equation (21) does not fall below the lower limit, it becomes easier to correct astigmatism, especially on the telephoto side. By ensuring that the corresponding value of conditional equation (21) does not exceed the upper limit, the refractive power of the first lens does not become too weak, making it easier to widen the angle. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional equation (21-1), and even more preferable that it satisfies the following conditional equation (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] When νRpave is the average value of the Abbe numbers of all positive lenses in the rear group GR with respect to the d line, it is preferable that the variable magnification optical system satisfies the following condition (22). Ensuring that the corresponding value of condition (22) does not fall below the lower limit is advantageous in correcting axial chromatic aberration, especially at the telephoto end. Ensuring that the corresponding value of condition (22) does not exceed the upper limit is advantageous in correcting aberrations other than chromatic aberration. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (22-1), and even more preferable that it satisfies the following condition (22-2). 40 < νRpave < 90 (22) 45 < νRpave < 86 (22-1) 50 < νRpave < 82 (22-2)

[0178] When DMwt is 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, it is preferable that the variable magnification optical system satisfies the following condition (23). As an example, Figure 2 shows the difference DMwt defined above for the variable magnification optical system of Figure 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, and 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 condition (23) does not fall below the lower limit, the amount of movement of the middle group GM during magnification can be suppressed, which is advantageous for miniaturizing the optical system. By ensuring that the corresponding value in conditional equation (23) does not exceed the upper limit, it is advantageous to suppress aberration fluctuations during magnification. To obtain even better characteristics, it is more preferable for the magnification optical system to satisfy the following conditional equation (23-1), and even more preferable for it to satisfy the following conditional equation (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 where the front group GF includes at least three negative lenses, including the first lens, and the refractive index of the first lens with respect to the d line is NL1, and the refractive index of the second negative lens from the object side in the front group with respect to the d line is NLn2, it is preferable that the variable magnification optical system satisfies the following conditional equation (24). By ensuring that the corresponding value of conditional equation (24) does not fall below the lower limit, it becomes easier to suitably secure the refractive power of the front group GF, which is advantageous in suppressing 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 equation (24) does not exceed the upper limit, it is possible to suppress the weight increase of the first lens and the second negative lens from the object side in the front group. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following conditional equation (24-1), and even more preferable that it satisfies the following conditional equation (24-2). 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 convex. This is advantageous for correcting spherical aberration across the entire magnification range. It is preferable that the lens with the strongest positive refractive power in the rear group is a biconvex lens. This is particularly advantageous for correcting spherical aberration at the telephoto end.

[0181] In a configuration where the image-side surface of the lens with the strongest positive refractive power in the rear group is convex, if 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 satisfies the following condition (25). Ensuring that the corresponding value of condition (25) does not fall below the lower limit is advantageous for correcting spherical aberration, especially at the telephoto end. Ensuring that the corresponding value of condition (25) does not exceed the upper limit makes it easier to reduce the angle of incidence of off-axis principal rays to the image plane Sim, especially at the wide-angle end, which is advantageous for securing peripheral illumination. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (25-1), and even more preferable that it satisfies the following condition (25-2). -10 <fRw / fRLp<5 (25) -9.5 <fRw / fRLp<4.5 (25-1) -9 <fRw / fRLp<4 (25-2)

[0182] When the effective diameter of the lens surface closest to the object in the front group GF is EDf, and the effective diameter of the lens surface closest to the image in the rear group GR is EDr, it is preferable that the variable magnification optical system satisfies the following condition equation (26). Generally, in order to reduce the diameter of the lens closest to the object, the refractive power of the front group GF becomes stronger, and when the refractive power of the front group GF becomes stronger, aberration fluctuations during magnification tend to increase. For these reasons, by ensuring that the corresponding value of condition equation (26) does not fall below the lower limit, the diameter of the lens closest to the object does not become too small, which is advantageous in suppressing aberration fluctuations during magnification. Alternatively, by ensuring that the corresponding value of condition equation (26) does not fall below the lower limit, the diameter of the lens closest to the object does not become too small, which is advantageous in securing the peripheral illumination ratio of the maximum image height. By ensuring that the corresponding value of condition equation (26) does not exceed the upper limit, the enlargement of the lens closest to the object can be suppressed, making miniaturization easier. To obtain better characteristics, the variable magnification optical system is more preferably satisfied with the following condition (26-1), and even more preferably satisfied with the following condition (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 between the outermost ray passing through the lens surface and the lens surface, and the optical axis Z, among the light rays that enter the lens surface from the object side and are emitted towards the image side. Here, "outer" refers to the radially outer side with respect to the optical axis Z, that is, the side away from the optical axis Z. Furthermore, the "outermost ray passing through the lens surface" is determined by considering the entire range of magnification.

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

[0185] The variable magnification optical system preferably satisfies the following condition (27). By ensuring that the corresponding value in condition (27) does not fall below the lower limit, the overall length of the optical system can be suppressed, making it easier to miniaturize in the optical axis direction. By ensuring that the corresponding value in condition (27) does not exceed the upper limit, the diameter of the lens closest to the object can be suppressed, making it easier to miniaturize in the radial direction. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (27-1), and even more preferable that it satisfies the following condition (27-2). 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 where the front group GF includes at least three negative lenses, if the Abbe number of the third negative lens from the object side in the front group, based on the d line, is νLn3, then it is preferable that the variable magnification optical system satisfies the following condition (28). By ensuring that the corresponding value of condition (28) does not fall below the lower limit, it is possible to suppress overcorrection of axial chromatic aberration at the telephoto end. By ensuring that the corresponding value of condition (28) does not exceed the upper limit, it is possible to suppress undercorrection of axial chromatic aberration at the telephoto end. To obtain even better characteristics, it is more preferable that the variable magnification optical system satisfies the following condition (28-1), and even more preferable that it satisfies the following condition (28-2). 50 < νLn3 < 95 (28) 55 < νLn3 < 91 (28-1) 60 < νLn3 < 87 (28-2)

[0187] The preferred and possible configurations described above can be combined in any way and are preferably selected as appropriate according to the required specifications. The preferred conditional expressions that the variable magnification optical system of this disclosure satisfies are not limited to those described in formula form, but include all conditional expressions obtained by arbitrarily combining lower and upper limits from the preferred, more preferred, and even more preferred conditional expressions.

[0188] As an example, a 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 fewer lens groups and has a negative refractive power as a whole throughout the entire magnification range, the middle group GM includes only one lens group having a positive refractive power as a lens group, and the rear group GR consists of three or fewer lens groups, with an aperture diaphragm St positioned between the lens surface closest to the image of the front group GF and the lens surface closest to the object of the rear group GR, and the distance between the front group GF and the middle group GM changes during magnification. The distance between the middle group GM and the rear group GR changes, and if the front group GF consists of two lens groups, the distance between adjacent lens groups within the front group changes during magnification, and if the rear group GR consists of multiple lens groups, the distance between all adjacent lens groups within the rear group changes during magnification, and the front group GF includes at least three negative lenses and at least one positive lens, and the front group GF has a first lens with a negative refractive power and a meniscus shape with a convex surface facing the object side, thus satisfying the above conditions (1) and (2).

[0189] Next, embodiments of the variable magnification optical system of this disclosure will be described with reference to the drawings. Note that the reference numerals attached to the lenses in the cross-sectional views of each embodiment are used independently for each embodiment to avoid complexity in explanation and drawings due to an increase in the number of digits of the reference numerals. Therefore, even if the same reference numerals are used in drawings of different embodiments, the configuration is not necessarily the same. Furthermore, embodiments 4, 10-12, and 19 below are embodiments of this disclosure, while embodiments 1-3, 5-9, and 13-18 are reference embodiments of this disclosure.

[0190] [Example 1] The configuration and movement direction of the variable magnification optical system of Example 1 are shown in Figure 1, and the method of illustration and configuration are as described above, so some redundant explanations will be omitted here. The variable magnification optical system of Example 1 consists 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, in order from the object side to the image side. 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, and an aperture diaphragm St, in order from the object side to the image side. The third lens group G3 consists of five lenses, L31 to L35, in order from the object side to the image side.

[0191] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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, L31 and L32. When focusing from an object at infinity to an object at a close distance, the focusing group moves towards the object.

[0192] Table 1 shows the basic lens data for the variable magnification optical system of Example 1, Table 2 shows the specifications and variable plane spacing, and Table 3 shows the aspherical coefficient. The table of basic lens data is written as follows: The Sn column shows the plane number, with the plane closest to the object being the first plane and the number increasing by one as you move toward the image side. The R column shows the radius of curvature of each plane. The D column shows the plane spacing on the optical axis between each plane and the plane adjacent to it on the image side. The Nd column shows the refractive index of each component with respect to the d line. The νd column shows the Abbe number of each component with respect to the d line. The ED column shows the effective diameter at the lens plane closest to the object and the lens plane closest to the image.

[0193] In the basic lens data table, the sign of the radius of curvature of a surface with a convex shape facing the object is positive, and the sign of the radius of curvature of a surface with a convex shape facing the image is negative. In the column for the surface number of the surface corresponding to the aperture diaphragm St, the surface number and the phrase (St) are entered. The value in the bottom column of column D of the table is the distance between the image-side surface in the table and the image plane Sim. For variable surface spacing, the symbol DD[ ] is used, and the surface number on the object side for this spacing is placed inside the brackets and entered in column D.

[0194] Table 2 shows the magnification ratio Zr, focal length f, back focus Bf in air equivalent distance, maximum aperture F number FNo., maximum angle of view 2ω, and variable plane spacing during magnification, relative to the d line. If the magnification optical system is a zoom lens, the magnification 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, intermediate focal length state, and telephoto end state, respectively.

[0195] In the basic lens data, the aspherical surface number is marked with an asterisk (*), and the column for the radius of curvature of the aspherical surface shows the value of the paraxial radius of curvature. In Table 3, the row labeled Sn shows the aspherical surface number, and the rows labeled KA and Am show the aspherical coefficient values ​​for each aspherical surface. Note that m in Am is an integer greater than or equal to 3 and varies depending on the surface. For example, in the third surface of Example 1, m = 4, 6, 8, 10, 12. The "E±n" (n: integer) value of the aspherical coefficient in Table 3 is "×10 ±n This means "[...]. KA and Am are the aspheric coefficients in the aspheric equation expressed by the following formula. Zd = C × h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspherical depth (length of the perpendicular line drawn from a point on the aspherical surface at height h to a plane perpendicular to the optical axis Z to which the aspherical surface vertex is tangent). h: Height (distance from the optical axis Z to the lens surface) C: Reciprocal of the radius of paraxial curvature KA, Am: Aspherical coefficients Therefore, the Σ in aspherical formulas represents the summation with respect to m.

[0196] Furthermore, in the basic lens data, the surface numbers of the aspherical surfaces of composite aspherical lenses are marked with **. For example, in Example 1, lens L33 is a composite aspherical lens, and the surface number of the 19th surface 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 for angles and millimeters as the unit for lengths. However, since optical systems can be used with proportional magnification or reduction, other appropriate units can also be used. Furthermore, the values ​​in the tables below are rounded to a predetermined number of decimal places.

[0198] [Table 1]

[0199] [Table 2]

[0200] [Table 3]

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

[0202] Unless otherwise specified, the symbols, meanings, description methods, and illustration methods for each data related to Example 1 described above are basically the same in the following examples, so repeated descriptions are omitted below.

[0203] [Example 2] FIG. 6 shows the configuration and movement direction of the variable magnification optical system of Example 2. The variable magnification optical system of Example 2 comprises, 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, and a fourth lens group G4 having negative 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 and an aperture stop St in order from the object side to the image side. The third lens group G3 consists of two lenses L31 to L32 in order from the object side to the image side. The fourth lens group G4 consists of three lenses L41 to L43 in order from the object side to the image side.

[0204] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 an object at a close distance, the focusing group moves towards the object.

[0205] For the variable magnification optical system of Example 2, the basic lens data is shown in Table 4, the specifications and variable plane spacing in Table 5, the aspherical coefficient in Table 6, and the aberration diagrams in Figure 7.

[0206] [Table 4]

[0207] [Table 5]

[0208] [Table 6]

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

[0210] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 an object at a close distance, the focusing group moves towards the object.

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

[0212] [Table 7]

[0213] [Table 8]

[0214] [Table 9]

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

[0216] During zooming, all lens groups move along the optical axis Z by 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 an object at a close distance, 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 spacings are shown in Table 11, aspheric coefficients are shown in Table 12, and various aberration diagrams are shown in Figure 11.

[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 of four lenses, namely lenses L11 to L14, in order from the object side to the image side. The second lens group G2 consists of three lenses, namely lenses L21 to L23, and an aperture stop St, in order from the object side to the image side. The third lens group G3 consists of two lenses, namely lenses L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of two lenses, namely lenses L41 to L42, in order from the object side to the image side. The fifth lens group G5 consists of one lens, namely lens L51.

[0222] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 an object at a close distance, the focusing group moves towards the object.

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

[0224] [Table 13]

[0225] [Table 14]

[0226] [Table 15]

[0227] [Example 6] Figure 14 shows the configuration and movement direction of the variable magnification optical system of Example 6. The variable magnification optical system of Example 6 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 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 diaphragm 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 two lenses, L51 and L52, arranged in order from the object side to the image side.

[0228] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 fourth lens group G4. When focusing from an object at infinity to an object at close range, the focusing group moves towards the image.

[0229] For the variable magnification optical system of Example 6, the basic lens data is shown in Table 16, the specifications and variable plane spacing are shown in Table 17, the aspherical coefficient is shown in Table 18, and the aberration diagrams are shown in Figure 15.

[0230] [Table 16]

[0231] [Table 17]

[0232] [Table 18]

[0233] [Example 7] Figure 16 shows the configuration and movement direction of the variable magnification optical system of Example 7. The variable magnification optical system of Example 7 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 five lenses, L11 to L15, 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 diaphragm St and three lenses, L31 to L33, in order from the object side to the image side. The lens group consists of the following elements. The fourth lens group G4 consists of one lens, lens L41. The fifth lens group G5 consists of two lenses, L51 and L52, arranged in order from the object side to the image side.

[0234] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 fourth lens group G4. When focusing from an object at infinity to an object at close range, the focusing group moves towards the image.

[0235] For the variable magnification optical system of Example 7, the basic lens data is shown in Table 19, the specifications and variable plane spacing are shown in Table 20, the aspherical coefficient is shown in Table 21, and the aberration diagrams are shown in Figure 17.

[0236] [Table 19]

[0237] [Table 20]

[0238] [Table 21]

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

[0240] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 fourth lens group G4. When focusing from an object at infinity to an object at close range, the focusing group moves towards the image.

[0241] For the variable magnification optical system of Example 8, the basic lens data is shown in Table 22, the specifications and variable plane spacing in Table 23, the aspherical coefficient in Table 24, and the aberration diagrams in Figure 19.

[0242] [Table 22]

[0243] [Table 23]

[0244] [Table 24]

[0245] [Example 9] Figure 20 shows the configuration and movement direction of the variable magnification optical system of Example 9. The variable magnification optical system of Example 9 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 negative 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, and an aperture diaphragm St, in order from the object side to the image side. The third lens group G3 consists of 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 two lenses, L51 and L52, arranged in order from the object side to the image side.

[0246] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 fourth lens group G4. When focusing from an object at infinity to an object at close range, the focusing group moves towards the image.

[0247] For the variable magnification optical system of Example 9, the basic lens data is shown in Table 25, the specifications and variable plane spacing in Table 26, the aspherical coefficient in Table 27, and the aberration diagrams in Figure 21.

[0248] [Table 25]

[0249] [Table 26]

[0250] [Table 27]

[0251] [Example 10] Figure 22 shows the configuration and movement direction of the variable magnification optical system of Example 10. The variable magnification optical system of Example 10 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 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 of four lenses, L11 to L14, in order from the object side to the image side. The second lens group G2 consists of lenses L21 to L22, an aperture diaphragm St, and lenses L23 to L25, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of two lenses, L41 to L42, in order from the object side to the image side. The fifth lens group G5 consists of a single lens, lens L51.

[0252] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 an object at close range, the focusing group moves towards the image.

[0253] For the variable magnification optical system of Example 10, the basic lens data is shown in Table 28, the specifications and variable plane spacing in Table 29, the aspherical coefficient in Table 30, and the aberration diagrams in Figure 23.

[0254] [Table 28]

[0255] [Table 29]

[0256] [Table 30]

[0257] [Example 11] Figure 24 shows the configuration and movement direction of the variable magnification optical system of Example 11. The variable magnification optical system of Example 11 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 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 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 diaphragm St and two lenses, L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of three lenses, L41 to L43, in order from the object side to the image side. The fifth lens group G5 consists of three lenses, L51 to L53, arranged in order from the object side to the image side.

[0258] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 an object at close range, the focusing group moves towards the image.

[0259] For the variable magnification optical system of Example 11, the basic lens data is shown in Table 31, the specifications and variable plane spacing in Table 32, the aspherical coefficient in Table 33, and the aberration diagrams in Figure 25.

[0260] [Table 31]

[0261] [Table 32]

[0262] [Table 33]

[0263] [Example 12] Figure 26 shows the configuration and movement direction of the variable magnification optical system of Example 12. The variable magnification optical system of Example 12 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 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 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 diaphragm St and two lenses, L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of four lenses, L41 to L44, in order from the object side to the image side. The fifth lens group G5 consists of three lenses, L51 to L53, arranged in order from the object side to the image side.

[0264] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 an object at close range, the focusing group moves towards the image.

[0265] For the variable magnification optical system of Example 12, the basic lens data is shown in Table 34, the specifications and variable plane spacing in Table 35, the aspherical coefficient in Table 36, and the aberration diagrams in Figure 27.

[0266] [Table 34]

[0267] [Table 35]

[0268] [Table 36]

[0269] [Example 13] Figure 28 shows the configuration and movement direction of the variable magnification optical system of Example 13. The variable magnification optical system of Example 13 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 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, and an aperture diaphragm St, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of three lenses, L41 to L43, in order from the object side to the image side. The fifth lens group G5 consists of a single lens, lens L51.

[0270] During magnification, 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 by changing the spacing between adjacent lens groups, while the fifth lens group G5 is fixed relative to the image plane Sim. The grounding symbol written below the fifth lens group G5 in the upper and middle sections of Figure 28 indicates that the fifth lens group G5 is fixed relative to the image plane Sim during magnification. The method of illustrating this grounding symbol 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 an object at close range, the focusing group moves toward the object.

[0271] For the variable magnification optical system of Example 13, the basic lens data is shown in Table 37, the specifications and variable plane spacing in Table 38, the aspherical coefficient in Table 39, and the aberration diagrams in Figure 29.

[0272] [Table 37]

[0273] [Table 38]

[0274] [Table 39]

[0275] [Example 14] Figure 30 shows the configuration and movement direction of the variable magnification optical system of Example 14. The variable magnification optical system of Example 14 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 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, and an aperture diaphragm St, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of three lenses, L41 to L43, in order from the object side to the image side. The fifth lens group G5 consists of a single lens, lens L51.

[0276] During magnification, 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 by 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, 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 an object at a close distance, the focusing group moves toward the object.

[0277] For the variable magnification optical system of Example 14, the basic lens data is shown in Table 40, the specifications and variable plane spacing are shown in Table 41, the aspherical coefficient is shown in Table 42, and the aberration diagrams are shown in Figure 31.

[0278] [Table 40]

[0279] [Table 41]

[0280] [Table 42]

[0281] [Example 15] Figure 32 shows the configuration and movement direction of the variable magnification optical system of Example 15. The variable magnification optical system of Example 15 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 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, and an aperture diaphragm St, in order from the object side to the image side. The third lens group G3 consists of two lenses, L31 to L32, in order from the object side to the image side. The fourth lens group G4 consists of three lenses, L41 to L43, in order from the object side to the image side. The fifth lens group G5 consists of a single lens, lens L51.

[0282] During magnification, 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 by 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, 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 an object at a close distance, the focusing group moves toward the object.

[0283] For the variable magnification optical system of Example 15, the basic lens data is shown in Table 43, the specifications and variable plane spacing are shown in Table 44, the aspherical coefficient is shown in Table 45, and the aberration diagrams are shown in Figure 33.

[0284] [Table 43]

[0285] [Table 44]

[0286] [Table 45]

[0287] [Example 16] Figure 34 shows the configuration and movement direction of the variable magnification optical system of Example 16. 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 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 diaphragm 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 two lenses, L51 and L52, arranged in order from the object side to the image side.

[0288] During 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 by 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 fourth lens group G4. When focusing from an object at infinity to an object at close range, the focusing group moves towards the image.

[0289] For the variable magnification optical system of Example 16, the basic lens data is shown in Table 46, the specifications and variable plane spacing are shown in Table 47, the aspherical coefficient is shown in Table 48, and the aberration diagrams are shown in Figure 35.

[0290] [Table 46]

[0291] [Table 47]

[0292] [Table 48]

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

[0294] During 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 by 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 a close distance, the focusing group moves toward the object.

[0295] For the variable magnification optical system of Example 17, the basic lens data is shown in Table 49, the specifications and variable plane spacing are shown in Table 50, the aspherical coefficient is shown in Table 51, and the aberration diagrams are shown in Figure 37.

[0296] [Table 49]

[0297] [Table 50]

[0298] [Table 51]

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

[0300] During magnification, 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 by 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, the basic lens data is shown in Table 52, the specifications and variable plane spacing are shown in Table 53, the aspherical coefficient is shown in Table 54, and the aberration diagrams are shown in Figure 39.

[0302] [Table 52]

[0303] [Table 53]

[0304] [Table 54]

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

[0306] During magnification, all lens groups change their spacing with adjacent lens groups and move along the optical axis Z. 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 an object at close range, the focusing group moves towards the image.

[0307] For the variable magnification optical system of Example 19, the basic lens data is shown in Table 55, the specifications and variable plane spacing are shown in Table 56, the aspherical coefficient is shown in Table 57, and the aberration diagrams are shown in Figure 41.

[0308] [Table 55]

[0309] [Table 56]

[0310] [Table 57]

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

[0312] [Table 58]

[0313] [Table 59]

[0314] [Table 60]

[0315] [Table 61]

[0316] The variable magnification optical systems of Examples 1 to 19, while being compact in size, achieve a wide field of view, with the entire field of view exceeding 100 degrees at the wide-angle end. The variable magnification optical systems of Examples 1 to 19 have a maximum magnification ratio of 1.7 or higher, which is relatively high for a wide-field-of-view optical system. Furthermore, 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. Figures 42 and 43 show external views of a camera 30, which is an imaging device according to one embodiment of the present disclosure. Figure 42 shows a perspective view of the camera 30 from the front, and Figure 43 shows a perspective view of the camera 30 from the rear. The camera 30 is a so-called mirrorless type digital camera, and an interchangeable lens 20 can be detachably attached. The interchangeable lens 20 is configured to include a variable magnification optical system 1 according to one embodiment of the present disclosure, which is housed in the lens barrel.

[0318] The camera 30 comprises a camera body 31, the top of which is provided a shutter button 32 and a power button 33. The rear of the camera body 31 is provided with an operation unit 34, an operation unit 35, and a display unit 36. The display unit 36 ​​can display captured images and images within the field of view before capture.

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

[0320] The camera body 31 contains an image sensor 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 image sensor to generate an image, and a recording medium for recording the generated image. The camera 30 can take still images or videos by pressing the shutter button 32, and the image data obtained from this shooting is recorded on the recording medium.

[0321] Although the technology of this disclosure has been described above with reference to embodiments and examples, the technology of this disclosure is not limited to the above embodiments and examples, and various modifications are possible. For example, the radius of curvature, interplanar spacing, refractive index, Abbe number, and aspheric coefficient of each lens are not limited to the values ​​shown in each of the above embodiments, but can take other values.

[0322] Furthermore, the imaging device according to the embodiments of this disclosure is not limited to the above example, and can take various forms, such as cameras other than mirrorless cameras, film cameras, video cameras, and security cameras. [Explanation of Symbols]

[0323] 1. Variable magnification optical system 20 interchangeable lenses 30 Cameras 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 3rd 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 diaphragm 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 ωt Maximum half-angle ωw Maximum half-angle

Claims

1. A variable magnification optical system consisting of a front group, a middle group, and a rear group, arranged in order from the object side to the image side, The aforementioned variable magnification optical system is a zoom lens, The aforementioned front group consists of a lens group having a single negative refractive power that moves during magnification. The aforementioned middle group includes only one lens group having a positive refractive power, The aforementioned rear group consists of three or fewer lens groups. A lens group with negative refractive power is positioned at the object-side end of the aforementioned rear group. An aperture diaphragm is positioned between the image-side lens surface of the front group and the object-side lens surface of the rear group. During scaling, the distance between the front group and the middle group changes, and the distance between the middle group and the rear group changes. If the rear group consists of multiple lens groups, when magnification is changed, the spacing between all adjacent lens groups within the rear group changes. The aforementioned front group includes at least three negative lenses and at least one positive lens. At the front group closest to the object, a first lens with a meniscus shape and negative refractive power, with its convex surface facing the object, is positioned. When the system is in focus on an object at infinity at the wide-angle end, the sum of the distance along the optical axis from the lens surface closest to the object in the front group to the lens surface closest to the image in the rear group, and the back focus of the entire system in air equivalent distance is TLw. fw is the focal length of the entire system when in focus on an object at infinity at the wide-angle end. The focal length of the entire system when in focus on an object at infinity at the telephoto end is ft. The maximum half-angle of view when focusing on an object at infinity at the telephoto end is ωt. The focal length of the middle group is fM, The focal length of the rear group when in focus 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. If Rr is the radius of curvature of the image-side surface of the first lens, 3.8<TLw / (ft×tanωt)<5.2 (1) 1<(fw×TLw) / ft ２ <1.75 (2-3) 0.65<fM / (fw×ft) 1 / 2 ≦0.855 (6-3) 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 following conditions: (1), (2-3), (6-3), (12-3), and (21-3).

2. If FNot is the maximum aperture F-number when the lens is in focus on an object at infinity at the telephoto end, 1.5<FNot / (ft / fw)<3 (3) A variable magnification optical system according to claim 1 that satisfies the conditional expression (3) represented by .

3. If the focal length of the front group when in focus on an object at infinity at the wide-angle end is fFw, 0.1<(-fFw) / fM<1.6 (4) A variable magnification optical system according to claim 1 or 2 that satisfies the conditional expression (4) represented by .

4. If the focal length of the front group when in focus on an object at infinity at the wide-angle end is fFw, 0.6<(-fFw) / (fw×ft) １／２ <13 (5) A variable magnification optical system according to any one of claims 1 to 3 that satisfies the conditional expression (5) represented by .

5. The focal length of the first lens is fL1, If the focal length of the front group when in focus on an object at infinity at the wide-angle end is fFw, 1<fL1 / fFw<3.5 (7) A variable magnification optical system according to any one of claims 1 to 4 that satisfies the conditional expression (7) represented by .

6. The focal length of the front group when in focus on an object at infinity at the wide-angle end is fFw. If FNot is the maximum aperture F-number when the lens is in focus on an object at infinity at the telephoto end, 1.8<(-fFw) / (ft / FNot)<4 (8) A variable magnification optical system according to any one of claims 1 to 5 that satisfies the conditional expression (8) represented by .

7. The central thickness of the first lens is D1, If FNot is the maximum aperture F-number when the lens is in focus on an object at infinity at the telephoto end, 0.08<D1 / (ft / FNot)<0.42 (9) A variable magnification optical system according to any one of claims 1 to 6 that satisfies the conditional expression (9) represented by .

8. The maximum half-angle when in focus on an object at infinity at the wide-angle end is ωw. If FNow is the maximum aperture F-number when focusing on an object at infinity at the wide-angle end, 0.3<tanωw / FNow<0.47 (10) A variable magnification optical system according to any one of claims 1 to 7 that satisfies the conditional expression (10) represented by .

9. When the lens group is in focus on an object at infinity at the wide-angle end, the distance along the optical axis from the lens surface closest to the object in the front group to the aperture diaphragm is DDFSTw. If the focal length of the front group when in focus on an object at infinity at the wide-angle end is fFw, 1.4<DDFSTw / |fFw|<4 (14) A variable magnification optical system according to any one of claims 1 to 8 that satisfies the conditional expression (14) represented by .

10. When the lens group is in focus on an object at infinity at the wide-angle end, the distance along the optical axis from the lens surface closest to the object in the front group to the aperture diaphragm is DDFSTw. If ωw is the maximum half-angle when in focus on an object at infinity at the wide-angle end, 5<DDFSTw / {(fw×tanωw)×log(ft / fw)}<10 (16) A variable magnification optical system according to any one of claims 1 to 9 that satisfies the conditional expression (16) represented by .

11. When the lens group is in focus on an object at infinity at the wide-angle end, and the distance along the optical axis from the lens surface closest to the object in the front group to the aperture diaphragm is denoted as DDFSTw, 0.3<DDFSTw / TLw<0.7 (18) A variable magnification optical system according to any one of claims 1 to 10 that satisfies the conditional expression (18) represented by .

12. If Bfw is the back focus of the entire system in terms of air-equivalent distance when focused on an object at infinity at the wide-angle end, 0.08<Bfw / TLw<0.27 (19) A variable magnification optical system according to any one of claims 1 to 11 that satisfies the conditional expression (19) represented by .

13. If νRPave is the average value of the Abbe numbers of all positive lenses in the aforementioned rear group, with respect to the d line, 40<νRpave<90 (22) A variable magnification optical system according to any one of claims 1 to 12 that satisfies the conditional expression (22) represented by .

14. The difference in the optical axis direction between the position of the middle lens group when focused on an object at infinity at the wide-angle end and the position of the middle lens group when focused on an object at infinity at the telephoto end is DMwt. 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) A variable magnification optical system according to any one of claims 1 to 13 that satisfies the conditional expression (23) represented by .

15. The refractive index of the first lens with respect to the d line is NL1, If the refractive index of the second negative lens from the object side among the negative lenses in the aforementioned front group is NLn2 with respect to the d line, 1.58<(NL1+NLn2) / 2<2.2 (24) A variable magnification optical system according to any one of claims 1 to 14 that satisfies the conditional expression (24) represented by .

16. The image-side surface of the lens with the strongest positive refractive power within the aforementioned group is convex. The focal length of the lens with the strongest positive refractive power within the aforementioned rear group is fRLp. If the focal length of the rear group when in focus on an object at infinity at the wide-angle end is fRw, -10<fRw / fRLp<5 (25) A variable magnification optical system according to any one of claims 1 to 15 that satisfies the conditional expression (25) represented by .

17. The variable magnification optical system according to claim 16, wherein the lens with the strongest positive refractive power in the aforementioned rear group is a biconvex lens.

18. The effective diameter of the lens surface closest to the object in the aforementioned front group is EDf. If the effective diameter of the image-side lens surface of the aforementioned rear group is defined as EDr, 1.1<EDf / EDr<2.1 (26) A variable magnification optical system according to any one of claims 1 to 17 that satisfies the conditional expression (26) represented by .

19. If the effective diameter of the lens surface closest to the object in the aforementioned front group is denoted as EDf, 0.2<EDf / TLw<0.45 (27) A variable magnification optical system according to any one of claims 1 to 18 that satisfies the conditional expression (27) represented by .

20. The aforementioned rear group includes a focusing group that moves along the optical axis when focusing occurs. The variable magnification optical system according to any one of claims 1 to 19, wherein the focusing group comprises two or fewer lenses.

21. The variable magnification optical system according to claim 20, wherein the focusing group comprises one negative lens and one positive lens.

22. It includes only one focusing group that moves along the optical axis during focusing. The variable magnification optical system according to any one of claims 1 to 20, wherein the focusing group is arranged within the rear group.

23. A variable magnification optical system according to any one of claims 1 to 20, comprising at least two cemented lenses, each consisting of one positive lens and one negative lens, on the image side of the front group.

24. If the Abbe number of the third negative lens from the object side among the negative lenses in the aforementioned front group is denoted as νLn3, then 50<νLn3<95 (28) A variable magnification optical system according to any one of claims 1 to 20 that satisfies the conditional expression (28) represented by .

25. A variable magnification optical system according to any one of claims 1 to 24, wherein all lens groups in the rear group move when the magnification is changed.

26. The variable magnification optical system according to any one of claims 1 to 25, wherein the front group comprises, in order from the object side to the image side, the first lens, the second lens having a negative refractive power and a meniscus shape with a convex surface facing the object side, the third lens having a negative refractive power and a concave surface facing the image side, and the fourth lens having a positive refractive power and a convex surface facing the object side.

27. An imaging apparatus comprising a variable magnification optical system according to any one of claims 1 to 26.

Images