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

Abstract

The variable magnification optical system (ZL) comprises, in order from the object side along the optical axis, an object-side lens group (GA) having a positive refractive power, an intermediate group (GM) having a positive refractive power, and a rear group (GR), the intermediate group (GM) having at least one lens group. The rear group (GR) has, in order from the object side along the optical axis, a first subsequent lens group (GR1) having a negative refractive power, a second subsequent lens group (GR2) having a positive refractive power, and a third subsequent lens group (GR3) having a negative refractive power, the interval between adjacent lens groups changes during zooming, the second subsequent lens group (GR2) moves along the optical axis during focusing, and the third subsequent lens group (GR3) moves along the optical axis during zooming. The variable magnification optical system (ZL) satisfies the following conditional expression: 1.05 < f1 / TLw < 2.00, where f1 is the focal length of the object-side lens group (GA), and TLw is the total length of the variable magnification optical system (ZL) in a wide-angle end state.

Description

Technical Field

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

[0002] Conventionally, there have been proposed variable-power optical systems suitable for still cameras, electronic still cameras, video cameras, and the like (see, for example, Patent Document 1). In such variable-power optical systems, it is difficult to obtain bright and good optical performance while miniaturizing the system.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-43375 Summary of the invention

[0006] The first embodiment relates to a variable power optical system comprising an object side lens group having positive optical power, an intermediate group having positive optical power, and a rear group arranged in sequence along the optical axis from the object side, wherein the intermediate group has at least one lens group, and the rear group has a first subsequent lens group having negative optical power, a second subsequent lens group having positive optical power, and a third subsequent lens group having negative optical power, arranged in sequence along the optical axis from the object side, wherein the intervals between adjacent lens groups change when variable power is performed, and the second subsequent lens group moves along the optical axis when focusing is performed, and the variable power optical system satisfies the following conditional expression: 1.05<f1 / TLw<2.00 Where, f1: the focal length of the object side lens group, TLw: The total length of the variable power optical system in the wide-angle end state.

[0007] The second embodiment involves a variable power optical system composed of an object side lens group with positive optical power, an intermediate group with positive optical power, and a rear group arranged in sequence along the optical axis from the object side, wherein the intermediate group has at least one lens group, and the rear group has a first subsequent lens group with negative optical power, a second subsequent lens group with positive optical power, and a third subsequent lens group with negative optical power, arranged in sequence along the optical axis from the object side, wherein the intervals between adjacent lens groups change when variable power is performed, and at least a part of the lens groups in the intermediate group are fixed relative to the image plane, and the variable power optical system satisfies the following conditional expression: 2.00<f1 / fMw<7.00 Where, f1: the focal length of the object side lens group, fMw: The combined focal length of the middle group in the wide-angle end state.

[0008] An optical device according to a third aspect is configured to include the above-mentioned variable power optical system.

[0009] A fourth aspect relates to a method for manufacturing a variable power optical system, wherein the variable power optical system is composed of an object side lens group having positive optical focal length, an intermediate group having positive optical focal length, and a rear group arranged in sequence along an optical axis from the object side, wherein the intermediate group has at least one lens group, and the rear group has a first subsequent lens group having negative optical focal length, a second subsequent lens group having positive optical focal length, and a third subsequent lens group having negative optical focal length, arranged in sequence along the optical axis from the object side, wherein when the power is changed, the intervals between adjacent lens groups change, and the second subsequent lens group moves along the optical axis when focusing, and the method for manufacturing the variable power optical system has the step of arranging the lenses in the lens barrel in a manner that satisfies the following conditional expression: 1.05<f1 / TLw<2.00 Where, f1: the focal length of the object side lens group, TLw: The total length of the variable power optical system in the wide-angle end state.

[0010] The fifth aspect relates to a method for manufacturing a variable power optical system, wherein the variable power optical system is composed of an object side lens group having positive optical focal length, an intermediate group having positive optical focal length, and a rear group arranged in sequence along the optical axis from the object side, wherein the intermediate group has at least one lens group, and the rear group has a first subsequent lens group having negative optical focal length, a second subsequent lens group having positive optical focal length, and a third subsequent lens group having negative optical focal length, arranged in sequence along the optical axis from the object side, wherein when the magnification is changed, the intervals between adjacent lens groups change, and at least a part of the lens groups in the intermediate group are fixed relative to the image plane, and the method for manufacturing the variable power optical system has the step of arranging the lenses in the lens barrel in a manner that satisfies the following conditional formula: 2.00<f1 / fMw<7.00 Where, f1: the focal length of the object side lens group, fMw: The combined focal length of the middle group in the wide-angle end state. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a diagram showing the lens structure of the variable power optical system according to the first embodiment.

[0012] Figure 2 (A) Figure 2 (B) are diagrams showing various aberrations when the variable power optical system according to the first embodiment is in focus at infinity in the wide-angle end state and the telephoto end state.

[0013] Figure 3It is a diagram showing the lens structure of the variable power optical system according to the second embodiment.

[0014] Figure 4 (A) Figure 4 (B) are diagrams showing various aberrations when the variable power optical system according to the second embodiment is in the wide-angle end state and the telephoto end state and is in focus at infinity.

[0015] Figure 5 It is a diagram showing the lens structure of the variable power optical system involved in the third embodiment.

[0016] Figure 6 (A) Figure 6 (B) are diagrams showing various aberrations when focusing at infinity in the wide-angle end state and the telephoto end state of the variable power optical system involved in the third embodiment.

[0017] Figure 7 It is a diagram showing the structure of a camera including a variable power optical system according to each embodiment.

[0018] Figure 8 This is a flowchart showing a method for manufacturing the variable power optical system according to the first embodiment.

[0019] Fig. 9 This is a flowchart showing a method for manufacturing the variable power optical system according to the second embodiment. DETAILED DESCRIPTION

[0020] Hereinafter, preferred embodiments of the present invention will be described. Figure 7 A camera (optical device) having a variable magnification optical system according to each embodiment will be described. Figure 7 As shown in FIG. 1 , the camera 1 is composed of a main body 2 and a photographic lens 3 mounted on the main body 2. The main body 2 includes a photographing element 4, a main body control unit (not shown) for controlling the operation of the digital camera, and a liquid crystal screen 5. The photographic lens 3 has a variable magnification optical system ZL composed of a plurality of lens groups and a lens position control mechanism (not shown) for controlling the position of each lens group. The lens position control mechanism is composed of a sensor for detecting the position of the lens group, a motor for moving the lens group forward and backward along the optical axis, and a control circuit for driving the motor.

[0021] The light from the subject is focused by the variable magnification optical system ZL of the photographic lens 3 and reaches the image plane I of the imaging element 4. The light from the subject that reaches the image plane I is photoelectrically converted by the imaging element 4 and recorded as digital image data in a memory (not shown). The digital image data recorded in the memory can be displayed on the LCD screen 5 according to the user's operation. In addition, the camera can be a mirrorless camera or a SLR camera with a quick return mirror. In addition, Figure 7The illustrated variable power optical system ZL schematically shows the variable power optical system included in the photographic lens 3 , and the lens structure of the variable power optical system ZL is not limited to this structure.

[0022] Next, the variable magnification optical system according to the first embodiment will be described. Figure 1 As shown, the variable power optical system ZL(1) as an example of the variable power optical system (zoom lens) ZL involved in the first embodiment is composed of an object side lens group GA with positive optical focal length, an intermediate group GM with positive optical focal length, and a rear group GR arranged in sequence along the optical axis from the object side. The intermediate group GM has at least one lens group. The rear group GR has a first subsequent lens group GR1 with negative optical focal length, a second subsequent lens group GR2 with positive optical focal length, and a third subsequent lens group GR3 with negative optical focal length, arranged in sequence along the optical axis from the object side. When changing the power, the intervals between adjacent lens groups change. The second subsequent lens group GR2 moves along the optical axis when focusing.

[0023] With the above configuration, the variable power optical system ZL according to the first embodiment satisfies the following conditional expression (1).

[0024] 1.05<f1 / TLw<2.00 …(1) Where, f1: focal length of the object side lens group GA TLw: The total length of the zoom optical system ZL at the wide-angle end

[0025] According to the first embodiment, a compact but bright variable power optical system having good optical performance and an optical device including the variable power optical system can be obtained. The variable power optical system ZL according to the first embodiment can be Figure 3 The variable magnification optical system ZL(2) shown can also be Figure 5 The variable magnification optical system ZL(3) shown.

[0026] Conditional expression (1) defines an appropriate relationship between the focal length of the object side lens group GA and the total length of the variable power optical system ZL in the wide angle end state. By satisfying conditional expression (1), spherical aberration can be corrected well.

[0027] When the corresponding value of conditional expression (1) exceeds the upper limit, the focal length of the object side lens group GA becomes weak, and it is difficult to miniaturize the zoom optical system ZL while correcting the spherical aberration. By setting the upper limit of conditional expression (1) to 1.90, 1.80, 1.70, 1.60, and further to 1.50, the effect of this embodiment can be made more reliable.

[0028] When the corresponding value of conditional expression (1) is lower than the lower limit, the focal length of the object side lens group GA becomes stronger, and it becomes difficult to correct the spherical aberration generated in the telephoto end state. By setting the lower limit of conditional expression (1) to 1.10, 1.15, 1.20, 1.25, and further to 1.30, the effect of this embodiment can be made more reliable.

[0029] Next, the variable power optical system according to the second embodiment will be described. The variable power optical system ZL according to the second embodiment has the same structure as the variable power optical system ZL according to the first embodiment, and thus the same reference numerals as those of the first embodiment will be added for description. Figure 1 As shown, the variable power optical system ZL(1) as an example of the variable power optical system (zoom lens) ZL involved in the second embodiment is composed of an object side lens group GA with positive optical focal length, an intermediate group GM with positive optical focal length, and a rear group GR arranged in sequence along the optical axis from the object side. The intermediate group GM has at least one lens group. The rear group GR has a first subsequent lens group GR1 with negative optical focal length, a second subsequent lens group GR2 with positive optical focal length, and a third subsequent lens group GR3 with negative optical focal length, arranged in sequence along the optical axis from the object side. When the magnification is changed, the intervals between adjacent lens groups change, and at least a part of the lens groups in the intermediate group GM are fixed relative to the image surface I.

[0030] With the above configuration, the variable power optical system ZL according to the second embodiment satisfies the following conditional expression (2).

[0031] 2.00<f1 / fMw<7.00 …(2) Where, f1: focal length of the object side lens group GA fMw: The composite focal length of the middle group GM at the wide-angle end

[0032] According to the second embodiment, a compact but bright variable power optical system having good optical performance and an optical device including the variable power optical system can be obtained. The variable power optical system ZL according to the second embodiment can be Figure 3 The variable magnification optical system ZL(2) shown can also be Figure 5 The variable magnification optical system ZL(3) shown.

[0033] Conditional expression (2) defines an appropriate relationship between the focal length of the object side lens group GA and the composite focal length of the middle group GM in the wide angle end state. By satisfying conditional expression (2), coma aberration and field curvature can be corrected well.

[0034] When the corresponding value of conditional expression (2) exceeds the upper limit, the focal length of the middle group GM in the wide-angle end state becomes stronger, and it becomes difficult to suppress the change of coma and field curvature during zooming. By setting the upper limit of conditional expression (2) to 6.75, 6.50, 6.25, 6.00, 5.75, and further to 5.50, the effect of this embodiment can be made more reliable.

[0035] When the corresponding value of conditional expression (2) is lower than the lower limit value, the focal length of the middle group GM in the wide-angle end state becomes weak, and it becomes difficult to miniaturize the zoom optical system ZL while correcting coma and field curvature. By setting the lower limit value of conditional expression (2) to 2.25, 2.50, 2.75, 3.00, 3.25, and further to 3.50, the effect of this embodiment can be made more reliable.

[0036] In the variable power optical system ZL according to the second embodiment, it is preferable that the second subsequent lens group GR2 moves along the optical axis during focusing.

[0037] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (3).

[0038] 1.50<f1 / (-fn1)<6.00…(3) fn1: the focal length of the lens group disposed closest to the object among the lens groups having negative refractive power in the variable magnification optical system ZL

[0039] Conditional expression (3) defines an appropriate relationship between the focal length of the object side lens group GA and the focal length of the lens group disposed closest to the object among the lens groups having negative refractive power in the variable power optical system ZL. By satisfying conditional expression (3), spherical aberration can be corrected well.

[0040] When the corresponding value of conditional expression (3) exceeds the upper limit, the focal length of the object side lens group GA becomes weak, and it is difficult to miniaturize the zoom optical system ZL while correcting the spherical aberration. By setting the upper limit of conditional expression (3) to 5.50, 5.00, 4.50, 4.00, and further to 3.50, the effects of each embodiment can be made more reliable.

[0041] When the corresponding value of conditional expression (3) is lower than the lower limit, the focal length of the object side lens group GA becomes stronger, and it becomes difficult to correct the spherical aberration generated in the telephoto end state. By setting the lower limit of conditional expression (3) to 1.75, 2.00, 2.25, and further to 2.50, the effects of each embodiment can be made more reliable.

[0042] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (4).

[0043] 0.05<(-fR3) / ft<1.00…(4) Where, fR3: focal length of the third subsequent lens group GR3 ft: Focal length of the zoom optical system ZL at the telephoto end

[0044] Conditional expression (4) defines an appropriate relationship between the focal length of the third subsequent lens group GR3 and the focal length of the variable power optical system ZL in the telephoto end state. By satisfying conditional expression (4), it is possible to correct distortion well while miniaturizing the lens.

[0045] When the corresponding value of conditional expression (4) exceeds the upper limit, the focal length of the third subsequent lens group GR3 becomes weak, and it becomes difficult to miniaturize the zoom optical system ZL while correcting the distortion. By setting the upper limit of conditional expression (4) to 0.80, 0.60, 0.50, and further to 0.40, the effects of each embodiment can be made more reliable.

[0046] When the corresponding value of conditional expression (4) is lower than the lower limit, the optical power of the third subsequent lens group GR3 becomes stronger, and it becomes difficult to suppress the change of distortion during zooming. By setting the lower limit of conditional expression (4) to 0.10, 0.15, 0.20, and further to 0.25, the effects of each embodiment can be made more reliable.

[0047] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (5).

[0048] 0.00<(-fR3) / fw<2.00…(5) Where, fR3: focal length of the third subsequent lens group GR3 fw: Focal length of the zoom optical system ZL at the wide-angle end

[0049] Conditional expression (5) defines an appropriate relationship between the focal length of the third subsequent lens group GR3 and the focal length of the variable power optical system ZL in the wide angle end state. By satisfying conditional expression (5), it is possible to correct distortion well while miniaturizing the lens.

[0050] When the corresponding value of conditional expression (5) exceeds the upper limit, the focal length of the third subsequent lens group GR3 becomes weak, and it becomes difficult to miniaturize the zoom optical system ZL while correcting the distortion. By setting the upper limit of conditional expression (5) to 1.75, 1.50, 1.25, and further to 1.00, the effects of each embodiment can be made more reliable.

[0051] When the corresponding value of conditional expression (5) is lower than the lower limit, the optical power of the third subsequent lens group GR3 becomes stronger, and it becomes difficult to suppress the change of distortion during zooming. By setting the lower limit of conditional expression (5) to 0.20, 0.40, 0.50, and further to 0.60, the effects of each embodiment can be made more reliable.

[0052] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (6).

[0053] 0.15<(TLt-TLw) / TLw<1.00…(6) Where, TLt: the total length of the zoom optical system ZL at the telephoto end TLw: The total length of the zoom optical system ZL at the wide-angle end

[0054] Conditional expression (6) defines an appropriate relationship between the total length of the variable power optical system ZL in the telephoto end state and the total length of the variable power optical system ZL in the wide angle end state. By satisfying conditional expression (6), spherical aberration can be corrected well.

[0055] When the corresponding value of conditional expression (6) exceeds the upper limit, the focal length of the object side lens group GA becomes weak, making it difficult to miniaturize the zoom optical system ZL while correcting the spherical aberration. By setting the upper limit of conditional expression (6) to 0.90, 0.80, 0.70, and further to 0.60, the effects of each embodiment can be made more reliable.

[0056] When the corresponding value of conditional expression (6) is lower than the lower limit, the focal length of the object side lens group GA becomes stronger, and it becomes difficult to correct the spherical aberration generated in the telephoto end state. By setting the lower limit of conditional expression (6) to 0.20, 0.25, 0.30, and further to 0.35, the effects of each embodiment can be made more reliable.

[0057] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (7).

[0058] 1.50<f1 / (-fR3)<6.00…(7) Where, fR3: focal length of the third subsequent lens group GR3

[0059] The conditional expression (7) defines an appropriate relationship between the focal length of the object side lens group GA and the focal length of the third subsequent lens group GR3. By satisfying the conditional expression (7), coma aberration can be corrected well.

[0060] When the corresponding value of conditional expression (7) exceeds the upper limit, the focal length of the object side lens group GA becomes weaker than the focal length of the third subsequent lens group GR3, and it becomes difficult to correct coma. By setting the upper limit of conditional expression (7) to 5.50, 5.00, 4.50, and further to 4.00, the effects of each embodiment can be made more reliable.

[0061] When the corresponding value of conditional expression (7) is lower than the lower limit, the focal length of the third subsequent lens group GR3 becomes weak, and it becomes difficult to miniaturize the zoom optical system ZL while correcting coma. By setting the lower limit of conditional expression (7) to 1.60, 1.70, 1.80, 1.90, and further to 2.00, the effects of each embodiment can be made more reliable.

[0062] In the variable power optical system ZL according to the first embodiment and the second embodiment, the third subsequent lens group GR3 preferably includes lenses satisfying the following conditional expressions (8) and (9).

[0063] 50.0<νd3<80.0 …(8) 1.45<nd3<1.58 …(9) Wherein, νd3: Abbe number of the lens in the third subsequent lens group GR3 nd3: refractive index of the lenses in the third subsequent lens group GR3 for the d-line

[0064] The conditional expression (8) specifies an appropriate range for the Abbe number of the lenses in the third subsequent lens group GR3. The conditional expression (9) specifies an appropriate range for the refractive index of the lenses in the third subsequent lens group GR3 for the d-line. By satisfying the conditional expressions (8) and (9), chromatic aberration of magnification can be corrected well.

[0065] When the corresponding value of conditional expression (8) exceeds the upper limit, the material of the lens in the third subsequent lens group GR3 becomes special glass, and the manufacturing cost becomes high. By setting the upper limit of conditional expression (8) to 79.0, 78.0, 77.0, and further to 75.0, the effects of each embodiment can be made more reliable.

[0066] When the corresponding value of conditional expression (8) is lower than the lower limit, it becomes difficult to correct the magnification chromatic aberration. By setting the lower limit of conditional expression (8) to 51.0, 52.0, 53.0, 54.0, and further to 55.0, the effects of each embodiment can be made more reliable.

[0067] When the corresponding value of conditional expression (9) exceeds the upper limit, the material of the lens in the third subsequent lens group GR3 becomes a high refractive index material, and the weight increases. By setting the upper limit of conditional expression (9) to 1.57, 1.56, and further to 1.55, the effects of each embodiment can be made more reliable.

[0068] When the corresponding value of conditional expression (9) is lower than the lower limit, the material of the lens in the third subsequent lens group GR3 becomes a low refractive index material, and the curvature of the surface of the lens needs to be increased, so it becomes difficult to correct the distortion. By setting the lower limit of conditional expression (9) to 1.46, 1.47, and further to 1.48, the effects of each embodiment can be made more reliable.

[0069] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (10).

[0070] 1.80<TLw / (-fR3)<2.70…(10) Where TLw: The total length of the zoom optical system ZL at the wide-angle end fR3: Focal length of the third subsequent lens group GR3

[0071] Conditional expression (10) defines an appropriate relationship between the total length of the variable power optical system ZL in the wide angle end state and the focal length of the third subsequent lens group GR3. By satisfying conditional expression (10), the total length of the variable power optical system ZL can be shortened while maintaining good optical performance.

[0072] When the corresponding value of conditional expression (10) exceeds the upper limit, the focal length of the third subsequent lens group GR3 becomes stronger, and it becomes difficult to suppress the change of distortion during zooming. By setting the upper limit of conditional expression (10) to 2.65, 2.60, 2.55, and further to 2.50, the effects of each embodiment can be made more reliable.

[0073] When the corresponding value of conditional expression (10) is lower than the lower limit value, the total length of the variable magnification optical system ZL in the wide-angle end state becomes longer, and it becomes difficult to shorten the total length of the variable magnification optical system ZL. By setting the lower limit value of conditional expression (10) to 1.85, 1.90, 1.95, and further to 2.00, the effects of each embodiment can be made more reliable.

[0074] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (11).

[0075] 0.30<(-fR1) / fR2<1.30…(11) Where, fR1: focal length of the first subsequent lens group GR1 fR2: Focal length of the second subsequent lens group GR2

[0076] The conditional expression (11) defines an appropriate relationship between the focal length of the first subsequent lens group GR1 and the focal length of the second subsequent lens group GR2. By satisfying the conditional expression (11), spherical aberration can be corrected well.

[0077] When the corresponding value of conditional expression (11) exceeds the upper limit, the optical power of the first subsequent lens group GR1 becomes weak, and it is difficult to miniaturize the zoom optical system ZL while correcting the spherical aberration. By setting the upper limit of conditional expression (11) to 1.20, 1.10, 1.00, and further to 0.90, the effects of each embodiment can be made more reliable.

[0078] When the corresponding value of conditional expression (11) is lower than the lower limit, the refractive power of the first subsequent lens group GR1 becomes strong, and it becomes difficult to correct spherical aberration. By setting the lower limit of conditional expression (11) to 0.40, 0.50, and further to 0.60, the effects of each embodiment can be made more reliable.

[0079] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (12).

[0080] 0.70<(-fR1) / fMw<2.00…(12) Where, fR1: focal length of the first subsequent lens group GR1 fMw: The composite focal length of the middle group GM at the wide-angle end

[0081] Conditional expression (12) defines an appropriate relationship between the focal length of the first subsequent lens group GR1 and the composite focal length of the middle group GM in the wide-angle end state. By satisfying conditional expression (12), spherical aberration can be corrected well.

[0082] When the corresponding value of conditional expression (12) exceeds the upper limit, the optical power of the first subsequent lens group GR1 becomes weak, and it is difficult to miniaturize the zoom optical system ZL while correcting the spherical aberration. By setting the upper limit of conditional expression (12) to 1.90, 1.80, 1.70, and further to 1.65, the effects of each embodiment can be made more reliable.

[0083] When the corresponding value of conditional expression (12) is lower than the lower limit, the optical power of the first subsequent lens group GR1 becomes stronger, and it becomes difficult to suppress the change of spherical aberration during zooming. By setting the lower limit of conditional expression (12) to 0.80, 0.90, 1.00, and further to 1.10, the effects of each embodiment can be made more reliable.

[0084] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (13).

[0085] 1.00<fR2 / fMw<3.00 …(13) Where, fR2: focal length of the second subsequent lens group GR2 fMw: The composite focal length of the middle group GM at the wide-angle end

[0086] Conditional expression (13) defines an appropriate relationship between the focal length of the second subsequent lens group GR2 and the composite focal length of the middle group GM in the wide-angle end state. By satisfying conditional expression (13), field curvature can be corrected well.

[0087] When the corresponding value of conditional expression (13) exceeds the upper limit, the optical power of the second subsequent lens group GR2 becomes weak, and it becomes difficult to miniaturize the zoom optical system ZL while correcting the image plane curvature. By setting the upper limit of conditional expression (13) to 2.90, 2.80, 2.70, 2.60, and further to 2.50, the effects of each embodiment can be made more reliable.

[0088] When the corresponding value of conditional expression (13) is lower than the lower limit, the optical power of the second subsequent lens group GR2 becomes stronger, and it becomes difficult to correct the field curvature. By setting the lower limit of conditional expression (13) to 1.10, 1.20, 1.30, 1.35, and further to 1.40, the effects of each embodiment can be made more reliable.

[0089] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (14).

[0090] 1.00<(-fR3) / fMw<3.50…(14) Where, fR3: focal length of the third subsequent lens group GR3 fMw: The composite focal length of the middle group GM at the wide-angle end

[0091] Conditional expression (14) defines an appropriate relationship between the focal length of the third subsequent lens group GR3 and the composite focal length of the middle group GM in the wide-angle end state. By satisfying conditional expression (14), it is possible to correct distortion well while miniaturizing the lens.

[0092] When the corresponding value of conditional expression (14) exceeds the upper limit, the focal length of the third subsequent lens group GR3 becomes weak, and it becomes difficult to miniaturize the zoom optical system ZL while correcting the distortion. By setting the upper limit of conditional expression (14) to 3.00, 2.50, 2.25, and further to 2.00, the effects of each embodiment can be made more reliable.

[0093] When the corresponding value of conditional expression (14) is lower than the lower limit, the optical power of the third subsequent lens group GR3 becomes stronger, and it becomes difficult to correct the distortion. By setting the lower limit of conditional expression (14) to 1.10, 1.15, 1.20, and further to 1.25, the effects of each embodiment can be made more reliable.

[0094] The variable power optical system ZL according to the first embodiment and the second embodiment preferably satisfies the following conditional expression (15).

[0095] 0.10<Bft / ft<0.80 …(15) Wherein: Bft: back focal length of the zoom optical system ZL at the telephoto end ft: Focal length of the zoom optical system ZL at the telephoto end

[0096] Conditional expression (15) specifies the appropriate relationship between the back focal length of the variable magnification optical system ZL in the telephoto end state and the focal length of the variable magnification optical system ZL in the telephoto end state. By satisfying conditional expression (15), a compact but bright variable magnification optical system with good optical performance can be obtained. By setting the upper limit value of conditional expression (15) to 0.75, 0.70, 0.65, 0.60, and further setting it to 0.50, the effect of the present embodiment can be made more reliable. In addition, by setting the lower limit value of conditional expression (15) to 0.15, 0.20, 0.25, and further setting it to 0.30, the effect of the present embodiment can be made more reliable.

[0097] In the variable power optical system ZL according to the first and second embodiments, it is preferable that, when performing variable power, the third subsequent lens group GR3 is fixed relative to the image plane I. This simplifies the structure of the components holding each lens group and reduces the weight of the variable power optical system ZL.

[0098] In the variable power optical system ZL according to the first embodiment and the second embodiment, it is preferable that the first subsequent lens group GR1 moves along the optical axis during focusing. This can satisfactorily suppress changes in field curvature during focusing.

[0099] Next, refer to Figure 8The manufacturing method of the variable power optical system ZL involved in the first embodiment is summarized. First, an object side lens group GA with positive optical focal length, an intermediate group GM with positive optical focal length, and a rear group GR are sequentially arranged along the optical axis from the object side (step ST1). At this time, at least one lens group is arranged in the intermediate group GM. In the rear group GR, a first subsequent lens group GR1 with negative optical focal length, a second subsequent lens group GR2 with positive optical focal length, and a third subsequent lens group GR3 with negative optical focal length are sequentially arranged along the optical axis from the object side. Next, it is configured so that the intervals between adjacent lens groups change when the magnification is changed (step ST2). Next, it is configured so that the second subsequent lens group GR2 moves along the optical axis when focusing (step ST3). Then, each lens is arranged in the lens barrel in a manner that at least satisfies the above-mentioned conditional formula (1) (step ST4). According to such a manufacturing method, a variable power optical system that is compact but bright and has good optical performance can be manufactured.

[0100] Next, refer to Fig. 9 The manufacturing method of the variable power optical system ZL involved in the second embodiment is summarized. First, an object side lens group GA with positive optical focal length, an intermediate group GM with positive optical focal length, and a rear group GR are sequentially arranged along the optical axis from the object side (step ST11). At this time, at least one lens group is arranged in the intermediate group GM. In the rear group GR, a first subsequent lens group GR1 with negative optical focal length, a second subsequent lens group GR2 with positive optical focal length, and a third subsequent lens group GR3 with negative optical focal length are sequentially arranged along the optical axis from the object side. Next, the structure is such that when the magnification is changed, the intervals between adjacent lens groups change, and at least a part of the lens groups in the intermediate group GM are fixed relative to the image plane I (step ST12). Then, each lens is arranged in the lens barrel in a manner that at least satisfies the above-mentioned conditional formula (2) (step ST13). According to such a manufacturing method, a variable power optical system that is compact but bright and has good optical performance can be manufactured.

[0101] Example

[0102] Hereinafter, a variable power optical system ZL according to an example of each embodiment will be described based on the drawings. Figure 1 , Figure 3 , Figure 5 This is a cross-sectional view showing the structure and focal length distribution of the variable power optical system ZL {ZL(1) to ZL(3)} involved in the first to third embodiments. In the cross-sectional view of the variable power optical system ZL(1) to ZL(3) involved in the first to third embodiments, the movement direction of each lens group when the zoom is changed from the wide-angle end state (W) to the telephoto end state (T) is indicated by an arrow. In addition, the movement direction of the focus lens group when focusing from infinity to a close object is indicated by an arrow together with the word "focus".

[0103] In these Figure 1 , Figure 3 , Figure 5 In the embodiment, each lens group is represented by a combination of a symbol G and a number, and each lens is represented by a combination of a symbol L and a number. In this case, in order to prevent the types and numbers of symbols and numbers from becoming large and complicated, a combination of symbols and numbers is used independently in each embodiment to represent a lens group, etc. Therefore, even if the same combination of symbols and numbers is used between embodiments, it does not mean that the same structure is used.

[0104] Tables 1 to 3 are shown below, wherein Table 1 is a table showing various parameter data in the first embodiment, Table 2 is a table showing various parameter data in the second embodiment, and Table 3 is a table showing various parameter data in the third embodiment. In each embodiment, the d line (wavelength λ=587.6nm) and the g line (wavelength λ=435.8nm) are selected as the calculation objects of the aberration characteristics.

[0105] In the table of [Overall parameters], f represents the focal length of the entire lens system, FNО represents the F value, 2ω represents the field of view angle (unit: ° (degrees), ω is the half field of view angle), and Y represents the image height. TL represents the distance obtained by adding Bf (back focal length) to the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image plane side of the zoom optical system when focusing at infinity, and Bf represents the distance on the optical axis from the lens surface closest to the image plane side of the zoom optical system when focusing at infinity to the image plane (air conversion distance). In addition, these values ​​are shown separately for each state of the zoom state at the wide-angle end (W), the middle focal length (M), and the telephoto end (T). In addition, in the table of [Overall parameters], fMw represents the composite focal length of the middle group in the wide-angle end state.

[0106] In the table of [lens parameters], the surface number indicates the order of the optical surfaces from the object side along the direction of light travel, R indicates the radius of curvature of each optical surface (the surface with the center of curvature on the image side is a positive value), D indicates the distance on the optical axis from each optical surface to the next optical surface (or image surface), i.e., the surface interval, nd indicates the refractive index of the material of the optical component for the d-line, and νd indicates the Abbe number of the material of the optical component based on the d-line. The "∞" of the radius of curvature indicates a plane or an opening, and (aperture S) indicates the aperture stop S. The record of the refractive index of air nd=1.00000 is omitted. In the case of an aspherical optical surface, an * is added to the surface number, and the paraxial curvature radius is shown in the column of the radius of curvature R.

[0107] In the table of [Aspheric surface data], for the aspheric surface shown in [Lens parameters], its shape is expressed by the following formula (A). X(y) represents the distance along the optical axis from the tangent plane at the vertex of the aspheric surface to the position on the aspheric surface at height y (the amount of concavity), R represents the curvature radius of the reference spherical surface (paraxial curvature radius), κ represents the cone constant, and Ai represents the i-th aspheric coefficient. "En" represents "×10 -n For example, 1.234E-05 = 1.234 × 10 -5 In addition, the secondary aspheric coefficient A2 is 0, and its description is omitted.

[0108] X(y)=(y 2 / R) / {1+(1-κ×y 2 / R 2 ) 1 / 2}+A4×y 4 +A6×y 6 +A8×y 8 +A10×y 10 +A12×y 12 … (A)

[0109] The table of [Variable Interval Data] shows the surface interval at the surface number i where the surface interval in the table of [Lens Parameters] is (Di). In addition, the table of [Variable Interval Data] shows the surface interval in the infinite focus state and the surface interval in the close focus state. D0 represents the distance from the object to the lens surface closest to the object in the variable magnification optical system.

[0110] In the table of [Lens Group Data], the initial surface (the surface closest to the object side) and the focal length of each lens group are shown.

[0111] In the following, all parameter values ​​disclosed, such as focal length f, radius of curvature R, surface spacing D, and other lengths, are generally expressed in "mm" unless otherwise specified. However, the optical system is not limited to this because the same optical performance can be achieved even if it is scaled up or down.

[0112] The description of the table so far is common to all the embodiments, and repeated description will be omitted below.

[0113] (First embodiment)

[0114] use Figure 1-2 and Table 1 illustrate the first embodiment. Figure 1: is a diagram showing the lens structure of the variable power optical system involved in the first embodiment. The variable power optical system ZL(1) involved in the first embodiment is composed of a first lens group G1 with positive optical focal length, a second lens group G2 with negative optical focal length, a third lens group G3 with positive optical focal length, a fourth lens group G4 with negative optical focal length, a fifth lens group G5 with positive optical focal length, and a sixth lens group G6 with negative optical focal length, which are arranged in sequence from the object side along the optical axis. When the magnification is changed from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 and the fourth lens group G4 move along the optical axis to the object side, and the second lens group G2 and the fifth lens group G5 move along the optical axis to the image plane side, and the intervals between adjacent lens groups change. In addition, when the magnification is changed, the third lens group G3 and the sixth lens group G6 are fixed relative to the image plane I. In addition, an aperture stop S is disposed between the second lens group G2 and the third lens group G3, and when the magnification is changed, the aperture stop S moves along the optical axis together with the second lens group G2. The symbol (+) or (-) attached to each lens group number indicates the optical power of each lens group, which is the same in all the following embodiments.

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

[0116] The second lens group G2 is composed of a cemented negative lens of a biconcave negative lens L21 and a positive meniscus lens L22 with a convex surface facing the object side, which are arranged in order from the object side along the optical axis, and a biconcave negative lens L23.

[0117] The third lens group G3 is composed of a positive meniscus lens L31 with a convex surface facing the object side, a biconvex positive lens L32, a biconcave negative lens L33, and a negative lens which is a cemented positive meniscus lens L34 with a convex surface facing the object side, a positive lens L35 with a convex surface on the object side, and a biconvex positive lens L36, which are arranged in order from the object side along the optical axis. The lens surfaces on both sides of the positive lens L35 are aspherical.

[0118] The fourth lens group G4 is composed of a cemented negative lens of a positive meniscus lens L41 having a convex surface facing the object side and a negative meniscus lens L42 having a convex surface facing the object side.

[0119] The fifth lens group G5 is composed of a positive meniscus lens L51 with a concave surface facing the object side. Both sides of the lens surface of the positive meniscus lens L51 are aspherical surfaces.

[0120] The sixth lens group G6 is composed of a negative meniscus lens L61 with a concave surface facing the object side. The lens surface on the object side of the negative meniscus lens L61 is an aspherical surface. An image surface I is arranged on the image side of the sixth lens group G6.

[0121] In the present embodiment, the first lens group G1 is equivalent to the object side lens group GA. The second lens group G2 and the third lens group G3 as a whole constitute an intermediate group GM having positive optical power. The fourth lens group G4 is equivalent to the first subsequent lens group GR1 constituting the rear group GR. The fifth lens group G5 is equivalent to the second subsequent lens group GR2 constituting the rear group GR. The sixth lens group G6 is equivalent to the third subsequent lens group GR3 constituting the rear group GR. When focusing from an object at infinity to an object at a close distance, the first subsequent lens group GR1 (the fourth lens group G4) moves along the optical axis to the image side, and the second subsequent lens group GR2 (the fifth lens group G5) moves along the optical axis to the object side.

[0122] Table 1 below shows the values ​​of parameters of the variable power optical system according to the first embodiment.

[0123] (Table 1)

[0124] [Overall parameters]

[0125] [Lens parameters]

[0126] [Aspherical surface data] Page 19 κ=0.000, A4=1.504E-09, A6=-6.079E-09, A8=4.173E-11, A10=-1.301E-13, A12=1.109E-16 Page 20 κ=0.000, A4=5.705E-06, A6=-4.363E-09, A8=2.313E-11, A10=-5.797E-14, A12=0.000E+00 Page 26 κ=0.000, A4=3.822E-07, A6=2.351E-08, A8=-1.490E-10, A10=5.248E-13, A12=-1.193E-15 Page 27 κ=0.000, A4=8.257E-06, A6=2.275E-08, A8=-1.369E-10, A10=4.522E-13, A12=-9.834E-16 Page 28 κ=0.000, A4=1.670E-05, A6=3.104E-09, A8=4.253E-12, A10=-5.342E-14, A12=1.371E-16

[0127] [Variable interval data]

[0128] [Lens group data]

[0129] Figure 2 (A) is a diagram showing various aberrations when the variable power optical system according to the first embodiment is in the wide-angle end state and is in infinity focus. Figure 2 (B) is a diagram of aberrations when the zoom optical system involved in the first embodiment is in the telephoto end state and is focused at infinity. In each aberration diagram, FNO represents the F value, and A represents the half field angle. In addition, the spherical aberration diagram shows the value of the F value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum half field angle, and the coma diagram shows the value of each half field angle. D represents the d-line (wavelength λ=587.6nm), and g represents the g-line (wavelength λ=435.8nm). In the astigmatism diagram, the solid line represents the sagittal image plane, and the dotted line represents the meridional image plane. In addition, in the aberration diagrams of the embodiments shown below, the same symbols as those of the present embodiment are used, and repeated descriptions are omitted.

[0130] As can be seen from the aberration diagrams, the variable power optical system according to the first embodiment corrects various aberrations well from the wide-angle end state to the telephoto end state and has excellent imaging performance.

[0131] (Second embodiment)

[0132] use Figure 3-4 And Table 2 illustrate the second embodiment. Figure 3: is a diagram showing the lens structure of the variable power optical system involved in the second embodiment. The variable power optical system ZL (2) involved in the second embodiment is composed of a first lens group G1 with positive optical focal length, a second lens group G2 with positive optical focal length, a third lens group G3 with negative optical focal length, a fourth lens group G4 with positive optical focal length, and a fifth lens group G5 with negative optical focal length, which are arranged in sequence from the object side along the optical axis. When the magnification is changed from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 and the third lens group G3 move along the optical axis toward the object side, and the fourth lens group G4 moves along the optical axis toward the image plane side, and the intervals between adjacent lens groups change. In addition, when the magnification is changed, the second lens group G2 and the fifth lens group G5 are fixed relative to the image plane I. In addition, an aperture stop S is arranged inside the second lens group G2, and when the magnification is changed, the aperture stop S is fixed relative to the image plane I.

[0133] The first lens group G1 is composed of a cemented positive lens of a negative meniscus lens L11 with a convex surface facing the object side and a positive meniscus lens L12 with a convex surface facing the object side, which are arranged in order from the object side along the optical axis, and a biconvex positive lens L13.

[0134] The second lens group G2 is composed of a negative lens composed of a biconcave negative lens L21 and a positive meniscus lens L22 with a convex surface facing the object side, a biconcave negative lens L23, a biconvex positive lens L24, a biconvex positive lens L25, a negative lens composed of a biconcave negative lens L26 and a biconvex positive lens L27, a biconvex positive lens L28, and a biconvex positive lens L29, which are arranged in order from the object side along the optical axis. The lens surfaces on both sides of the positive lens L28 are aspherical surfaces. An aperture stop S is arranged between the negative lens L23 and the positive lens L24 in the second lens group G2.

[0135] The third lens group G3 is composed of a cemented negative lens of a biconvex positive lens L31 and a biconcave negative lens L32.

[0136] The fourth lens group G4 is composed of a positive meniscus lens L41 with a concave surface facing the object side. Both sides of the lens surface of the positive meniscus lens L41 are aspherical surfaces.

[0137] The fifth lens group G5 is composed of a negative meniscus lens L51 with a concave surface facing the object side. Both sides of the lens surface of the negative meniscus lens L51 are aspherical surfaces. An image surface I is arranged on the image side of the fifth lens group G5.

[0138] In the present embodiment, the first lens group G1 is equivalent to the object side lens group GA. The second lens group G2 as a whole constitutes an intermediate group GM having positive optical power. The third lens group G3 is equivalent to the first subsequent lens group GR1 constituting the rear group GR. The fourth lens group G4 is equivalent to the second subsequent lens group GR2 constituting the rear group GR. The fifth lens group G5 is equivalent to the third subsequent lens group GR3 constituting the rear group GR. When focusing from an object at infinity to an object at a close distance, the first subsequent lens group GR1 (the third lens group G3) moves along the optical axis to the image plane side, and the second subsequent lens group GR2 (the fourth lens group G4) moves along the optical axis to the object side.

[0139] Table 2 below shows the values ​​of parameters of the variable power optical system according to the second embodiment.

[0140] (Table 2)

[0141] [Overall parameters]

[0142] [Lens parameters]

[0143] [Aspherical surface data] Page 19 κ=0.000, A4=-2.580E-06, A6=-2.781E-09, A8=6.087E-12, A10=-1.542E-14, A12=1.672E-17 Page 20 κ=0.000, A4=9.392E-08, A6=-2.660E-09, A8=2.889E-12, A10=-4.235E-15, A12=0.000E+00 Page 26 κ=0.000, A4=-1.401E-06, A6=8.643E-09, A8=-1.465E-11, A10=-2.254E-14, A12=-1.063E-16 Page 27 κ=0.000, A4=5.349E-06, A6=7.127E-09, A8=-1.507E-11, A10=7.454E-15, A12=-1.405E-16 Page 28 κ=0.000, A4=2.023E-05, A6=-3.714E-08, A8=1.151E-10, A10=-1.819E-13, A12=1.124E-16 Page 29 κ=0.000, A4=7.556E-06, A6=-3.415E-08, A8=1.029E-10, A10=-1.477E-13, A12=6.108E-17

[0144] [Variable interval data]

[0145] [Lens group data]

[0146] Figure 4 (A) is a diagram showing various aberrations when the variable power optical system according to the second embodiment is in the wide-angle end state and is in focus at infinity. Figure 4 (B) is a diagram of various aberrations when focusing at infinity in the telephoto end state of the variable power optical system involved in the second embodiment. According to the various aberration diagrams, it can be seen that the variable power optical system involved in the second embodiment corrects various aberrations well from the wide-angle end state to the telephoto end state and has excellent imaging performance.

[0147] (Third embodiment)

[0148] use Figure 5-6 And Table 3 illustrate the third embodiment. Figure 5 : is a diagram showing the lens structure of the variable power optical system involved in the third embodiment. The variable power optical system ZL (3) involved in the third embodiment is composed of a first lens group G1 with positive optical focal length, a second lens group G2 with negative optical focal length, a third lens group G3 with positive optical focal length, a fourth lens group G4 with positive optical focal length, a fifth lens group G5 with negative optical focal length, a sixth lens group G6 with positive optical focal length, and a seventh lens group G7 with negative optical focal length, which are arranged in sequence from the object side along the optical axis. When the magnification is changed from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1, the third lens group G3, and the fifth lens group G5 move along the optical axis toward the object side, and the second lens group G2 and the sixth lens group G6 move along the optical axis toward the image plane side, and the intervals between adjacent lens groups change. In addition, when the magnification is changed, the fourth lens group G4 and the seventh lens group G7 are fixed relative to the image plane I. In addition, an aperture stop S is arranged between the second lens group G2 and the third lens group G3. When the magnification is changed, the aperture stop S moves along the optical axis together with the third lens group G3.

[0149] The first lens group G1 is composed of a positive lens composed of a negative meniscus lens L11 with a convex surface facing the object side and a biconvex positive lens L12, and a positive meniscus lens L13 with a convex surface facing the object side, arranged in order from the object side along the optical axis.

[0150] The second lens group G2 is composed of a cemented negative lens of a biconcave negative lens L21 and a positive meniscus lens L22 with a convex surface facing the object side, which are arranged in order from the object side along the optical axis, and a biconcave negative lens L23.

[0151] The third lens group G3 is composed of a positive meniscus lens L31 having a convex surface facing the object side.

[0152] The fourth lens group G4 is composed of a positive meniscus lens L41 with a convex surface facing the object side, a negative meniscus lens L42 with a convex surface facing the object side, a negative lens formed by a positive meniscus lens L43 with a convex surface facing the object side, a positive meniscus lens L44 with a convex surface facing the object side, and a biconvex positive lens L45, which are arranged in order from the object side along the optical axis. The lens surfaces on both sides of the positive meniscus lens L44 are aspherical.

[0153] The fifth lens group G5 is composed of a cemented negative lens of a positive meniscus lens L51 having a convex surface facing the object side and a negative meniscus lens L52 having a convex surface facing the object side.

[0154] The sixth lens group G6 is composed of a positive meniscus lens L61 with a concave surface facing the object side. Both sides of the lens surface of the positive meniscus lens L61 are aspherical surfaces.

[0155] The seventh lens group G7 is composed of a plano-concave negative lens L71 with a flat surface facing the image side. The object side lens surface of the negative lens L71 is an aspherical surface. An image surface I is arranged on the image side of the seventh lens group G7.

[0156] In the present embodiment, the first lens group G1 is equivalent to the object side lens group GA. The second lens group G2, the third lens group G3 and the fourth lens group G4 constitute as a whole an intermediate group GM having positive optical power. The fifth lens group G5 is equivalent to the first subsequent lens group GR1 constituting the rear group GR. The sixth lens group G6 is equivalent to the second subsequent lens group GR2 constituting the rear group GR. The seventh lens group G7 is equivalent to the third subsequent lens group GR3 constituting the rear group GR. When focusing from an object at infinity to an object at a close distance, the first subsequent lens group GR1 (the fifth lens group G5) moves along the optical axis to the image plane side, and the second subsequent lens group GR2 (the sixth lens group G6) moves along the optical axis to the object side.

[0157] Table 3 below shows the values ​​of parameters of the variable power optical system according to the third embodiment.

[0158] (Table 3)

[0159] [Overall parameters]

[0160] [Lens parameters]

[0161] [Aspherical surface data] Page 19 κ=0.000, A4=3.529E-06, A6=7.180E-09, A8=1.864E-11, A10=0.000E+00, A12=0.000E+00 Page 20 κ=0.000, A4=1.102E-05, A6=8.970E-09, A8=1.747E-11, A10=0.000E+00, A12=0.000E+00 Page 26 κ=0.000, A4=-5.680E-07, A6=7.802E-09, A8=5.979E-12, A10=-4.891E-13, A12=1.108E-15 Page 27 κ=0.000, A4=9.289E-06, A6=5.070E-09, A8=8.783E-11, A10=-7.537E-13, A12=1.362E-15 Page 28 κ=0.000, A4=1.899E-05, A6=2.021E-08, A8=1.589E-11, A10=-1.257E-13, A12=3.238E-16

[0162] [Variable interval data]

[0163] [Lens group data]

[0164] Figure 6 (A) is a diagram showing various aberrations when the variable power optical system according to the third embodiment is in the wide-angle end state and is in focus at infinity. Figure 6 (B) is a diagram of various aberrations when focusing at infinity in the telephoto end state of the variable power optical system involved in the third embodiment. According to the various aberration diagrams, it can be seen that the variable power optical system involved in the third embodiment corrects various aberrations well from the wide-angle end state to the telephoto end state and has excellent imaging performance.

[0165] Next, a table of [conditional expression corresponding values] is shown below. In this table, values ​​corresponding to the conditional expressions (1) to (15) are collectively shown for all the examples (first to third examples).

[0166] Conditional formula (1) 1.05<f1 / TLw<2.00

[0167] Conditional formula (2) 2.00<f1 / fMw<7.00

[0168] Conditional formula (3) 1.50<f1 / (-fn1)<6.00

[0169] Conditional formula (4) 0.05<(-fR3) / ft<1.00

[0170] Conditional formula (5) 0.00<(-fR3) / fw<2.00

[0171] Conditional formula (6) 0.15<(TLt-TLw) / TLw<1.00

[0172] Conditional formula (7) 1.50<f1 / (-fR3)<6.00

[0173] Conditional formula (8) 50.0<νd3<80.0

[0174] Conditional expression (9)1.45<nd3<1.58

[0175] Conditional formula (10) 1.80<TLw / (-fR3)<2.70

[0176] Conditional formula (11) 0.30<(-fR1) / fR2<1.30

[0177] Conditional formula (12) 0.70<(-fR1) / fMw<2.00

[0178] Conditional formula (13) 1.00<fR2 / fMw<3.00

[0179] Conditional expression (14)1.00<(-fR3) / fMw<3.50

[0180] Conditional expression (15)0.10<Bft / ft<0.80

[0181] [Conditional Expression Corresponding Value] (First to Third Embodiments)

[0182] According to the above-described embodiments, a variable magnification optical system that is compact but bright and has excellent optical performance can be realized.

[0183] The above-mentioned embodiments are only specific examples of the present invention, and the present invention is not limited thereto.

[0184] The following contents can be appropriately adopted within the range that does not impair the optical performance of the variable power optical system of each embodiment.

[0185] As examples of the variable power optical system of each embodiment, a variable power optical system with a 5-group structure, a variable power optical system with a 6-group structure, and a variable power optical system with a 7-group structure are shown, but the present application is not limited thereto, and a variable power optical system with other group structures (e.g., 8-group, 9-group, 10-group, etc.) may also be configured. For example, a structure in which a lens or a lens group is added to the object side or the image plane side of the variable power optical system of each embodiment. In addition, for example, a structure in which a lens or a lens group is added to the object side or the image plane side of the middle group in the variable power optical system of each embodiment. In addition, a lens group refers to a portion having at least one lens separated by a variable air gap when changing the power.

[0186] In the variable power optical system of each embodiment, it is not limited to use the first subsequent lens group and the second subsequent lens group (that is, the fourth lens group and the fifth lens group, or the third lens group and the fourth lens group, or the fifth lens group and the sixth lens group) as the focus lens group, but it is also possible to use a single lens group or multiple lens groups, or part of the lens group as the focus lens group, and the focus lens group moves along the optical axis direction to focus from an infinitely distant object to a close object. The focus lens group is also suitable for autofocus and is also suitable for motor drive (using an ultrasonic motor, etc.) for autofocus.

[0187] Alternatively, a lens group or part of a lens group may be used as an anti-shake lens group, which moves in a direction having a component perpendicular to the optical axis, or rotates and moves (sways) in a plane including the optical axis to correct image shake caused by hand shake.

[0188] The lens surface may be formed by a spherical surface or a flat surface, or may be formed by an aspherical surface. When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment become easy, and degradation of optical performance caused by errors in processing and assembly adjustment can be prevented, so it is preferred. In addition, even in the case of deviation of the image plane, degradation of the image rendering performance is small, so it is preferred.

[0189] When the lens surface is an aspheric surface, the aspheric surface may be any of an aspheric surface processed by grinding, a glass molded aspheric surface formed by a mold into an aspheric shape, and a composite aspheric surface formed by forming a resin into an aspheric shape on the surface of glass. In addition, the lens surface may be a diffraction surface, and the lens may be a distributed refractive index lens (GRIN lens) or a plastic lens.

[0190] The aperture stop is preferably arranged inside the middle group (ie, between the second lens group and the third lens group or inside the second lens group), but a component serving as the aperture stop may not be provided and its function may be replaced by a lens frame.

[0191] In order to reduce glare and ghosting and achieve high-contrast optical performance, an antireflection film with high transmittance in a wide wavelength range may be applied to each lens surface.

[0192] Description of symbols G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group G5 5th lens group G6 6th lens group G7 Lens Group 7 I Image plane S Aperture stop

Claims

1. A variable magnification optical system, wherein: The variable power optical system is composed of an object side lens group with positive optical power, an intermediate lens group with positive optical power, and a rear lens group arranged in sequence from the object side along the optical axis. The intermediate group has at least one lens group, The rear group includes a first subsequent lens group having negative optical power, a second subsequent lens group having positive optical power, and a third subsequent lens group having negative optical power, which are arranged in order from the object side along the optical axis. When changing magnification, the intervals between adjacent lens groups change. The second subsequent lens group moves along the optical axis when focusing. The variable magnification optical system satisfies the following conditional formula: 1.05<f1 / TLw<2.00 Where, f1: the focal length of the object side lens group, TLw: The total length of the variable power optical system in the wide-angle end state.

2. A variable magnification optical system, wherein: It consists of an object-side lens group with positive refractive power, a middle lens group with positive refractive power, and a rear lens group arranged in order from the object side along the optical axis. The intermediate group has at least one lens group, The rear group includes a first subsequent lens group having negative optical power, a second subsequent lens group having positive optical power, and a third subsequent lens group having negative optical power, which are arranged in order from the object side along the optical axis. When changing the magnification, the intervals between adjacent lens groups change, and at least a portion of the lens groups in the intermediate group are fixed relative to the image plane. The variable magnification optical system satisfies the following conditional formula: 2.00<f1 / fMw<7.00 Where, f1: the focal length of the object side lens group, fMw: The combined focal length of the middle group in the wide-angle end state.

3. The variable magnification optical system according to claim 2, wherein: The second subsequent lens group moves along the optical axis when focusing.

4. The variable power optical system according to any one of claims 1 to 3, wherein: The variable magnification optical system satisfies the following conditional formula: 1.50<f1 / (-fn1)<6.00 Wherein, fn1 is the focal length of the lens group disposed closest to the object among the lens groups having negative optical power in the variable power optical system.

5. The variable power optical system according to any one of claims 1 to 4, wherein: The variable magnification optical system satisfies the following conditional formula: 0.05<(-fR3) / ft<1.00 Wherein, fR3: the focal length of the third subsequent lens group, ft: the focal length of the variable magnification optical system in the telephoto end state.

6. The variable power optical system according to any one of claims 1 to 5, wherein: The variable magnification optical system satisfies the following conditional formula: 0.00<(-fR3) / fw<2.00 Wherein, fR3: the focal length of the third subsequent lens group, fw: focal length of the variable power optical system in the wide-angle end state.

7. The variable power optical system according to any one of claims 1 to 6, wherein: The variable magnification optical system satisfies the following conditional formula: 0.15<(TLt-TLw) / TLw<1.00 Wherein, TLt: the total length of the variable magnification optical system in the telephoto end state, TLw: The total length of the variable power optical system in the wide-angle end state.

8. The variable power optical system according to any one of claims 1 to 7, wherein: The variable magnification optical system satisfies the following conditional formula: 1.50<f1 / (-fR3)<6.00 Wherein, fR3: focal length of the third subsequent lens group.

9. The variable power optical system according to any one of claims 1 to 8, wherein: The third subsequent lens group includes lenses that satisfy the following conditional formula: 50.0<νd3<80.0 1.45<nd3<1.58 Wherein, νd3: the Abbe number of the lens in the third subsequent lens group, nd3: the refractive index of the lens in the third subsequent lens group for the d-line.

10. The variable power optical system according to any one of claims 1 to 9, wherein: The variable magnification optical system satisfies the following conditional formula: 1.80<TLw / (-fR3)<2.70 Wherein, TLw: the total length of the variable magnification optical system in the wide-angle end state, fR3: focal length of the third subsequent lens group.

11. The variable power optical system according to any one of claims 1 to 10, wherein: The variable magnification optical system satisfies the following conditional formula: 0.30<(-fR1) / fR2<1.30 Wherein, fR1: the focal length of the first subsequent lens group, fR2: focal length of the second subsequent lens group.

12. The variable power optical system according to any one of claims 1 to 11, wherein: The variable magnification optical system satisfies the following conditional formula: 0.70<(-fR1) / fMw<2.00 Wherein, fR1: the focal length of the first subsequent lens group, fMw: The combined focal length of the middle group in the wide-angle end state.

13. The variable power optical system according to any one of claims 1 to 12, wherein: The variable magnification optical system satisfies the following conditional formula: 1.00<fR2 / fMw<3.00 Wherein, fR2: the focal length of the second subsequent lens group, fMw: The combined focal length of the middle group in the wide-angle end state.

14. The variable power optical system according to any one of claims 1 to 13, wherein: The variable magnification optical system satisfies the following conditional formula: 1.00<(-fR3) / fMw<3.50 Wherein, fR3: the focal length of the third subsequent lens group, fMw: The combined focal length of the middle group in the wide-angle end state.

15. The variable power optical system according to any one of claims 1 to 14, wherein: The variable magnification optical system satisfies the following conditional formula: 0.10<Bft / ft<0.80 Wherein, Bft: the back focal length of the variable magnification optical system in the telephoto end state, ft: the focal length of the variable magnification optical system in the telephoto end state.

16. The variable power optical system according to any one of claims 1 to 15, wherein: When changing magnification, the third subsequent lens group is fixed relative to the image plane.

17. The variable power optical system according to any one of claims 1 to 16, wherein: The first subsequent lens group moves along the optical axis when focusing.

18. An optical device comprising the variable power optical system according to any one of claims 1 to 17.

19. A method for manufacturing a variable-power optical system, the variable-power optical system comprising an object-side lens group having positive optical power, an intermediate lens group having positive optical power, and a rear lens group arranged in sequence from the object side along an optical axis, wherein: The intermediate group has at least one lens group, The rear group includes a first subsequent lens group having negative optical power, a second subsequent lens group having positive optical power, and a third subsequent lens group having negative optical power, which are arranged in order from the object side along the optical axis. When changing magnification, the intervals between adjacent lens groups change. The second subsequent lens group moves along the optical axis when focusing. The method for manufacturing the variable magnification optical system comprises the steps of arranging each lens in the lens barrel in a manner satisfying the following conditional expression: 1.05<f1 / TLw<2.00 Where, f1: the focal length of the object side lens group, TLw: The total length of the variable power optical system in the wide-angle end state.

20. A method for manufacturing a variable-power optical system, the variable-power optical system comprising an object-side lens group having positive optical power, an intermediate lens group having positive optical power, and a rear lens group arranged in sequence from the object side along an optical axis, wherein: The intermediate group has at least one lens group, The rear group includes a first subsequent lens group having negative optical power, a second subsequent lens group having positive optical power, and a third subsequent lens group having negative optical power, which are arranged in order from the object side along the optical axis. When changing the magnification, the intervals between adjacent lens groups change, and at least a portion of the lens groups in the intermediate group are fixed relative to the image plane. The method for manufacturing the variable magnification optical system comprises the steps of arranging each lens in the lens barrel in a manner satisfying the following conditional expression: 2.00<f1 / fMw<7.00 Where, f1: the focal length of the object side lens group, fMw: The combined focal length of the middle group in the wide-angle end state.

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