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

Abstract

The variable magnification optical system (ZL) is configured from a first lens group (G1) having a positive refractive power, a second lens group (G2) having a negative refractive power, a third lens group (G3) having a positive refractive power, and a rear group (GR) having at least five lens groups, which are arranged in order from the object side along the optical axis, and the interval between adjacent lens groups changes during magnification change. The first lens group (G1) is fixed with respect to the image plane (I), and the following conditional expression is satisfied: 0.05 < (-f2) / f1 < 1.00, 0.02 < Bft / ft < 0.15 where f1 is the focal length of the first lens group (G1), f2 is the focal length of the second lens group (G2), ft is the focal length of the variable magnification optical system (ZL) in a telephoto end state, and Bft is the back focal length of the variable magnification optical system (ZL) in a telephoto end state.

Description

Technical Field

[0001] The present 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, variable magnification optical systems suitable for still cameras, electronic still cameras, video cameras, etc. have been proposed (for example, see Patent Document 1). In such variable magnification optical systems, it is difficult to achieve brightness and good optical performance while being compact.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-52338 Summary of the Invention

[0006] The first variable power optical system of the present invention comprises a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a rear lens group having at least five lens groups, arranged in sequence along the optical axis from the object side. During variable power, the intervals between adjacent lens groups change, the first lens group is fixed relative to the image plane, and the variable power optical system satisfies the following conditional expression: 0.05<(-f2) / f1<1.00 0.02<Bft / ft<0.15 Wherein, f1: focal length of the first lens group, f2: focal length of the second lens group, ft: focal length of the zoom optical system at the telephoto end, Bft: back focal length of the variable magnification optical system in the telephoto end state.

[0007] The second zoom optical system of the present invention comprises a first lens group having positive optical power, a second lens group having negative optical power, a third lens group having positive optical power, and a rear group having at least five lens groups, which are arranged in sequence from the object side along the optical axis. When zooming, the intervals between adjacent lens groups change. The first lens group is fixed relative to the image plane. The at least five lens groups of the rear group include a first focusing lens group having negative optical power and a second focusing lens group having positive optical power and arranged on the image side of the first focusing lens group. When focusing, the first focusing lens group and the second focusing lens group move along the optical axis with different trajectories. The zoom optical system satisfies the following conditional expression: 0.10<(-fF1) / fF2<1.30 0.01<Bfw / fw<0.50 Wherein, fF1: the focal length of the first focusing lens group, fF2: focal length of the second focusing lens group, fw: focal length of the variable magnification optical system at the wide-angle end, Bfw: The back focal length of the variable magnification optical system in the wide-angle end state.

[0008] The optical device of the present invention is configured to include the above-mentioned variable magnification optical system.

[0009] The first aspect of the present invention is a method for manufacturing a variable magnification optical system, wherein the variable magnification optical system comprises a first lens group having positive focal length, a second lens group having negative focal length, a third lens group having positive focal length, and a rear group having at least five lens groups, which are arranged in sequence from the object side along the optical axis, wherein the method for manufacturing the variable magnification optical system comprises the step of arranging the lenses in the lens barrel in the following manner: when the magnification is changed, the intervals between adjacent lens groups change, the first lens group is fixed relative to the image plane, and the variable magnification optical system satisfies the following conditional expression, namely, 0.05<(-f2) / f1<1.00 0.02<Bft / ft<0.15 Wherein, f1: focal length of the first lens group, f2: focal length of the second lens group, ft: focal length of the zoom optical system at the telephoto end, Bft: back focal length of the variable magnification optical system in the telephoto end state.

[0010] The second aspect of the present invention is a method for manufacturing a variable power optical system, wherein the variable power optical system is composed of a first lens group with positive optical focal length and a second lens group with negative optical focal length, which are arranged in sequence from the object side along the optical axis, wherein the method for manufacturing the variable power optical system has the step of arranging the lenses in the lens barrel in the following manner: when changing the power, the intervals between adjacent lens groups change, the first lens group is fixed relative to the image plane, the at least five lens groups of the rear group include a first focusing lens group with negative optical focal length and a second focusing lens group with positive optical focal length which is arranged closer to the image plane than the first focusing lens group, when focusing, the first focusing lens group and the second focusing lens group move along the optical axis with different trajectories, and the variable power optical system satisfies the following conditional expression, that is, 0.10<(-fF1) / fF2<1.30 0.01<Bfw / fw<0.50 Wherein, fF1: the focal length of the first focusing lens group, fF2: focal length of the second focusing lens group, fw: focal length of the variable magnification optical system at the wide-angle end, Bfw: The back focal length of the variable magnification optical system in the wide-angle end state. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0012] Figure 2 These are diagrams showing various aberrations of the variable power optical system of Example 1 when focusing at infinity at the wide-angle end.

[0013] Figure 3 These are diagrams showing various aberrations of the variable power optical system of Example 1 in the telephoto end state when focusing at infinity.

[0014] Figure 4 This is a diagram showing the lens configuration of the variable power optical system according to the second embodiment.

[0015] Figure 5 These are diagrams showing various aberrations of the variable power optical system of Example 2 when focusing at infinity at the wide-angle end.

[0016] Figure 6 These are diagrams showing various aberrations of the variable power optical system of Example 2 in the telephoto end state when focusing at infinity.

[0017] Figure 7 This is a diagram showing the lens configuration of the variable power optical system according to the third embodiment.

[0018] Figure 8 These are diagrams showing various aberrations of the variable power optical system of Example 3 when focusing at infinity at the wide-angle end.

[0019] Figure 9 These are diagrams showing various aberrations of the variable power optical system of Example 3 in the telephoto end state when focusing at infinity.

[0020] Figure 10 The diagrams illustrate the configuration of a camera including a variable power optical system according to each embodiment.

[0021] Figure 11 This is a flowchart showing a method for manufacturing the variable power optical system according to the first embodiment.

[0022] Figure 12 This is a flowchart showing a method for manufacturing the variable power optical system according to the second embodiment. DETAILED DESCRIPTION

[0023] Hereinafter, preferred embodiments of the present invention will be described. Figure 10A camera (optical device) having a variable magnification optical system according to each embodiment will be described. Figure 10 As shown, the camera 1 consists of a main body 2 and a taking lens 3 mounted on the main body 2. The main body 2 includes an image sensor 4, a main body control unit (not shown) that controls the operation of the digital camera, and a liquid crystal display 5. The taking lens 3 includes a variable magnification optical system ZL composed of multiple lens groups and a lens position control mechanism (not shown) that controls the position of each lens group. The lens position control mechanism is composed of sensors that detect the position of the lens groups, motors that move the lens groups back and forth along the optical axis, and a control circuit that drives the motor.

[0024] 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 then 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 in response to user operations. In addition, the camera can be either a mirrorless camera or a single-lens reflex camera with a quick-return mirror. In addition, Figure 10 The illustrated variable magnification optical system ZL schematically represents the variable magnification optical system included in the photographic lens 3 , and the lens structure of the variable magnification optical system ZL is not limited to this structure.

[0025] Next, the variable magnification optical system of the first embodiment will be described. Figure 1 As shown, a variable power optical system ZL (1) as an example of a variable power optical system (zoom lens) ZL according to a first embodiment is composed of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a rear lens group GR having at least five lens groups arranged in order from the object side along the optical axis. During zooming, the intervals between adjacent lens groups change, and the first lens group G1 is fixed relative to the image plane I.

[0026] With the above-described configuration, the variable power optical system ZL of the first embodiment satisfies the following conditional expressions (1) and (2). 0.05<(-f2) / f1<1.00 …(1) 0.02<Bft / ft<0.15 …(2) Where, f1: focal length of the first lens group G1 f2: Focal length of the second lens group G2 ft: Focal length of the zoom optical system ZL at the telephoto end Bft: Back focal length of the zoom optical system ZL at the telephoto end

[0027] According to the first embodiment, a variable magnification optical system that is compact, bright, and has good optical performance, and an optical device including the variable magnification optical system can be obtained. The variable magnification optical system ZL of the first embodiment can also be Figure 4 The variable magnification optical system ZL(2) shown can also be Figure 7 The variable magnification optical system ZL(3) shown.

[0028] Conditional expression (1) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the first lens group G1. By satisfying conditional expression (1), spherical aberration, coma, and field curvature can be corrected well.

[0029] If the corresponding value of conditional expression (1) exceeds the upper limit, the optical power of the first lens group G1 becomes stronger, making it difficult to correct spherical aberration, coma, and field curvature generated by the first lens group G1. By setting the upper limit of conditional expression (1) to 0.80, 0.70, 0.50, 0.40, and further to 0.37, the effect of the first embodiment can be made more reliable.

[0030] If the corresponding value of conditional expression (1) is lower than the lower limit, the optical power of the second lens group G2 becomes stronger, making it difficult to correct the spherical aberration, coma, and field curvature generated by the second lens group G2. By setting the lower limit of conditional expression (1) to 0.10, 0.15, 0.20, 0.25, and further to 0.30, the effect of the first embodiment can be made more reliable.

[0031] Conditional expression (2) specifies an 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 (2), a variable magnification optical system that is bright and has good optical performance while being compact can be obtained. By setting the upper limit value of conditional expression (2) to 0.12 and further to 0.10, the effect of the first embodiment can be made more reliable. In addition, by setting the lower limit value of conditional expression (2) to 0.02, 0.04, and further to 0.05, the effect of the first embodiment can be made more reliable.

[0032] Next, the variable magnification optical system of the second embodiment will be described. The variable magnification optical system ZL of the second embodiment has the same structure as the variable magnification optical system ZL of the first embodiment, and therefore the same reference numerals as those of the first embodiment will be used for description. Figure 1As shown, the variable magnification optical system ZL (1) as an example of the variable magnification optical system (zoom lens) ZL of the second 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, and a rear group GR having at least five lens groups, which are arranged in sequence from the object side along the optical axis. When changing magnification, the intervals between adjacent lens groups change, and the first lens group G1 is fixed relative to the image plane. The at least five lens groups of the rear group GR include a first focusing lens group GF1 with negative optical focal length and a second focusing lens group GF2 with positive optical focal length, which is arranged on the image side of the first focusing lens group GF1. When focusing, the first focusing lens group GF1 and the second focusing lens group GF2 move along the optical axis with different trajectories. In addition, the lens groups that move when focusing in the wide-angle end state can be referred to as the first focusing lens group GF1, the second focusing lens group GF2, ... in sequence from the object side.

[0033] With the above configuration, the variable power optical system ZL of the second embodiment satisfies the following conditional expressions (3) and (4). 0.10<(-fF1) / fF2<1.30…(3) 0.01<Bfw / fw<0.50 …(4) Where, fF1: focal length of the first focusing lens group GF1 fF2: Focal length of the second focusing lens group GF2 fw: Focal length of the zoom optical system ZL at the wide-angle end Bfw: Back focal length of the zoom optical system ZL at the wide-angle end

[0034] According to the second embodiment, a variable magnification optical system that is compact, bright, and has good optical performance, and an optical device including the variable magnification optical system can be obtained. The variable magnification optical system ZL of the second embodiment can also be Figure 4 The variable magnification optical system ZL(2) shown can also be Figure 7 The variable magnification optical system ZL(3) shown.

[0035] Conditional expression (3) defines an appropriate relationship between the focal length of the first focus lens group GF1 and the focal length of the second focus lens group GF2. By satisfying conditional expression (3), spherical aberration can be corrected well.

[0036] If the corresponding value of conditional expression (3) exceeds the upper limit, the refractive power of the second focusing lens group GF2 becomes stronger, making it difficult to correct spherical aberration and coma generated during focusing. By setting the upper limit of conditional expression (3) to 1.20, 1.10, 1.00, 0.90, and further to 0.80, the effect of the second embodiment can be made more reliable.

[0037] If the corresponding value of conditional expression (3) is lower than the lower limit, the optical power of the first focusing lens group GF1 becomes stronger, making it difficult to correct the spherical aberration generated during focusing. By setting the lower limit of conditional expression (3) to 0.15, 0.20, 0.25, 0.35, 0.45, and further to 0.50, the effect of the second embodiment can be made more reliable.

[0038] Conditional expression (4) specifies an appropriate relationship between the back focal length of the variable magnification optical system ZL in the wide-angle end state and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (4), a variable magnification optical system that is bright and has good optical performance while being compact can be obtained. By setting the upper limit value of conditional expression (4) to 0.45, 0.40, 0.35, 0.33, 0.30, and further setting it to 0.28, the effect of the second embodiment can be made more reliable. In addition, by setting the lower limit value of conditional expression (4) to 0.05, 0.10, and further setting it to 0.13, the effect of the second embodiment can be made more reliable.

[0039] The zoom optical system ZL of the first embodiment can satisfy the aforementioned conditional expression (4). By satisfying conditional expression (4), as in the second embodiment, a zoom optical system that is bright and has good optical performance while being compact can be obtained. By setting the upper limit value of conditional expression (4) to 0.45, 0.40, 0.35, 0.33, 0.30, and further setting it to 0.28, the effect of the first embodiment can be made more reliable. In addition, by setting the lower limit value of conditional expression (4) to 0.05, 0.10, and further setting it to 0.13, the effect of the first embodiment can be made more reliable.

[0040] In the variable power optical system ZL of the first embodiment, at least five lens groups of the rear group GR may include a first focusing lens group GF1 having a negative optical focal length and a second focusing lens group GF2 having a positive optical focal length and being arranged on the image side of the first focusing lens group GF1. When focusing, the first focusing lens group GF1 and the second focusing lens group GF2 move along the optical axis in different trajectories. In addition, the variable power optical system ZL of the first embodiment may satisfy the aforementioned conditional expression (3). By satisfying the conditional expression (3), spherical aberration can be well corrected as in the second embodiment. By setting the upper limit value of the conditional expression (3) to 1.20, 1.10, 1.00, 0.90, and further to 0.80, the effect of the first embodiment can be made more reliable. Furthermore, by setting the lower limit value of conditional expression (3) to 0.15, 0.20, 0.25, 0.35, 0.45, and further to 0.50, the effect of the first embodiment can be made more reliable.

[0041] The variable power optical system ZL according to the first embodiment and the second embodiment can satisfy the following conditional expression (5). 0.50<f2 / fF1<1.00 …(5) Where, f2: focal length of the second lens group G2

[0042] Conditional expression (5) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the second focus lens group GF2. By satisfying conditional expression (5), spherical aberration can be corrected well.

[0043] If the corresponding value of conditional expression (5) exceeds the upper limit, the optical power of the first focusing lens group GF1 becomes stronger, making it difficult to correct the spherical aberration generated during focusing. By setting the upper limit of conditional expression (5) to 0.95, and further to 0.90, the effects of each embodiment can be made more reliable.

[0044] If the corresponding value of conditional expression (5) is lower than the lower limit, the optical power of the second lens group G2 becomes stronger, making it difficult to correct the spherical aberration, coma, and field curvature generated by the second lens group G2. By setting the lower limit of conditional expression (5) to 0.60, 0.65, and further to 0.70, the effects of each embodiment can be made more reliable.

[0045] The variable power optical system ZL according to the first embodiment and the second embodiment can satisfy the following conditional expression (6). 1.20<f1 / fF2<2.00 …(6) Where, f1: focal length of the first lens group G1

[0046] Conditional expression (6) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the second focus lens group GF2. By satisfying conditional expression (6), spherical aberration and coma can be corrected well.

[0047] If the corresponding value of conditional expression (6) exceeds the upper limit, the optical power of the second focusing lens group GF2 becomes stronger, making it difficult to correct spherical aberration and coma generated during focusing. By setting the upper limit of conditional expression (6) to 1.90 and further to 1.85, the effects of each embodiment can be made more reliable.

[0048] If the corresponding value of conditional expression (6) is lower than the lower limit, the optical power of the first lens group G1 becomes stronger, making it difficult to correct spherical aberration, coma, and field curvature generated by the first lens group G1. By setting the lower limit of conditional expression (6) to 1.25, 1.30, and further to 1.35, the effects of each embodiment can be made more reliable.

[0049] The variable power optical system ZL according to the first embodiment and the second embodiment can satisfy the following conditional expression (7). 0.50<f3 / fF2<1.00 …(7) Where, f3: focal length of the third lens group G3

[0050] Conditional expression (7) defines an appropriate relationship between the focal length of the third lens group G3 and the focal length of the second focus lens group GF2. By satisfying conditional expression (7), spherical aberration and coma can be corrected well.

[0051] If the corresponding value of conditional expression (7) exceeds the upper limit, the optical power of the second focusing lens group GF2 becomes stronger, making it difficult to correct spherical aberration and coma generated during focusing. By setting the upper limit of conditional expression (7) to 0.95 and further to 0.90, the effects of each embodiment can be made more reliable.

[0052] If the corresponding value of conditional expression (7) is lower than the lower limit, the optical power of the third lens group G3 becomes stronger, making it difficult to correct the spherical aberration, coma, and field curvature generated by the third lens group G3. By setting the lower limit of conditional expression (7) to 0.60, 0.65, and further to 0.70, the effects of each embodiment can be made more reliable.

[0053] In the zoom optical system ZL of the first embodiment and the second embodiment, the second focusing lens group GF2 may be composed of a single lens component. This makes it possible to make the zoom optical system compact and lightweight. In addition, in each embodiment, the lens component represents a single lens or a cemented lens. The second focusing lens group GF2 may be composed of a positive lens. The second focusing lens group GF2 may be composed of a cemented positive lens.

[0054] The variable power optical system ZL according to the first embodiment and the second embodiment can satisfy the following conditional expression (8). 2.00<TLw / fw<6.00 …(8) Where, fw: focal length of the zoom optical system ZL at the wide-angle end TLw: Total length of the zoom optical system ZL at the wide-angle end

[0055] Conditional expression (8) specifies an appropriate relationship between the total length of the variable magnification optical system ZL in the wide-angle end state and the focal length of the variable magnification optical system ZL in the wide-angle end state. By satisfying conditional expression (8), a variable magnification optical system that is bright and has good optical performance while being compact can be obtained. By setting the upper limit value of conditional expression (8) to 5.50, 5.00, 4.50, and further to 4.00, the effects of each embodiment can be made more reliable. In addition, by setting the lower limit value of conditional expression (8) to 2.50, 2.80, 3.00, and further to 3.10, the effects of each embodiment can be made more reliable.

[0056] The variable power optical system ZL according to the first embodiment and the second embodiment can satisfy the following conditional expression (9). 0.01<(-f2) / f3<2.00 …(9) Where, f2: focal length of the second lens group G2 f3: Focal length of the third lens group G3

[0057] Conditional expression (9) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the third lens group G3. By satisfying conditional expression (9), spherical aberration, coma, and field curvature can be corrected well.

[0058] If the corresponding value of conditional expression (9) exceeds the upper limit, the optical power of the third lens group G3 becomes stronger, making it difficult to correct the spherical aberration, coma, and field curvature generated by the third lens group G3. By setting the upper limit of conditional expression (9) to 1.80, 1.60, 1.50, 1.35, 1.10, and further to 1.00, the effect of this embodiment can be made more reliable.

[0059] If the corresponding value of conditional expression (9) is lower than the lower limit, the optical power of the second lens group G2 becomes stronger, making it difficult to correct the spherical aberration, coma, and field curvature generated by the second lens group G2. By setting the lower limit of conditional expression (9) to 0.10, 0.20, 0.30, 0.35, 0.45, 0.50, and further to 0.55, the effect of this embodiment can be made more reliable.

[0060] The variable power optical system ZL according to the first embodiment and the second embodiment can satisfy the following conditional expression (10). 1.80<f1 / f3<2.50 …(10) Where, f1: focal length of the first lens group G1 f3: Focal length of the third lens group G3

[0061] Conditional expression (10) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the third lens group G3. By satisfying conditional expression (10), spherical aberration, coma, and field curvature can be corrected well.

[0062] If the corresponding value of conditional expression (10) exceeds the upper limit, the optical power of the third lens group G3 becomes stronger, making it difficult to correct the spherical aberration, coma, and field curvature generated by the third lens group G3. By setting the upper limit of conditional expression (10) to 2.45, 2.40, and further to 2.35, the effect of this embodiment can be made more reliable.

[0063] If the corresponding value of conditional expression (10) is lower than the lower limit, the optical power of the first lens group G1 becomes stronger, making it difficult to correct the spherical aberration, coma, and field curvature generated by the first lens group G1. By setting the lower limit of conditional expression (10) to 1.85 and further to 1.90, the effect of this embodiment can be made more reliable.

[0064] In the variable power optical system ZL of the first and second embodiments, at least five lens groups of the rear group GR may include the final lens group GE disposed most toward the image plane, and may satisfy the following conditional expression (11). 0.01<|fr1 / fr|<5.00…(11) Where, fr: focal length of the final lens group GE fr1: Focal length of the lens group in the rear lens group GR arranged on the object side of the final lens group GE

[0065] Conditional expression (11) defines an appropriate relationship between the focal length of the lens group arranged on the object side of the final lens group GE in the rear group GR and the focal length of the final lens group GE. By satisfying conditional expression (11), field curvature can be corrected well.

[0066] If the corresponding value of conditional expression (11) exceeds the upper limit, the optical power of the final lens group GE becomes stronger, making it difficult to correct the field curvature generated by the final lens group GE. By setting the upper limit of conditional expression (11) to 4.80, 4.50, 4.30, 3.50, 3.30, 3.00, 2.80, and further to 2.50, the effect of this embodiment can be made more reliable.

[0067] If the corresponding value of conditional expression (11) is lower than the lower limit, the optical power of the lens group arranged on the object side of the final lens group GE in the rear lens group GR becomes stronger, making it difficult to correct the coma and field curvature generated by the lens group arranged on the object side of the final lens group GE. By setting the lower limit of conditional expression (11) to 0.10, 0.20, 0.25, 0.35, 0.45, and further to 0.50, the effect of this embodiment can be made more reliable.

[0068] In the variable power optical system ZL of the first and second embodiments, at least five lens groups of the rear group GR include the final lens group GE disposed most toward the image plane, and satisfy the following conditional expression (12). 0.10<f2 / fr1<0.75 …(12) Where, f2: focal length of the second lens group G2 fr1: Focal length of the lens group in the rear lens group GR arranged on the object side of the final lens group GE

[0069] Conditional expression (12) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the lens group arranged on the object side of the final lens group GE in the rear group GR. By satisfying conditional expression (12), coma and field curvature can be corrected well.

[0070] If the corresponding value of conditional expression (12) exceeds the upper limit, the optical power of the lens group arranged on the object side of the final lens group GE in the rear lens group GR becomes stronger, making it difficult to correct the coma and field curvature generated by the lens group arranged on the object side of the final lens group GE. By setting the upper limit of conditional expression (12) to 0.70 and further to 0.68, the effect of this embodiment can be made more reliable.

[0071] If the corresponding value of conditional expression (12) is lower than the lower limit, the optical power of the second lens group G2 becomes stronger, making it difficult to correct the spherical aberration, coma, and image curvature generated by the second lens group G2. By setting the lower limit of conditional expression (12) to 0.15 and further to 0.20, the effect of this embodiment can be made more reliable.

[0072] In the variable power optical system ZL of the first and second embodiments, the at least five lens groups of the rear group GR may include a final lens group GE disposed closest to the image plane, and during zooming, the final lens group GE may be fixed relative to the image plane I. This allows for miniaturization of the variable power optical system.

[0073] In the variable power optical system ZL of the first and second embodiments, the at least five lens groups of the rear lens group GR may include a final lens group GE positioned closest to the image plane. The final lens group GE may be composed of a negative lens and a positive lens arranged in order from the object side along the optical axis. This allows for excellent correction of chromatic aberration.

[0074] Next, refer to Figure 11 The manufacturing method of the zoom optical system ZL of the first embodiment is briefly described. First, a first lens group G1 with positive optical power, a second lens group G2 with negative optical power, a third lens group G3 with positive optical power, and a rear group GR are arranged in sequence from the object side along the optical axis (step ST1). At this time, at least five lens groups are arranged in the rear group GR. Next, the intervals between adjacent lens groups change when zooming, and the first lens group G1 is fixed relative to the image plane I (step ST2). Then, each lens is arranged in the lens barrel in a manner that satisfies at least the above-mentioned conditional expressions (1) and (2) (step ST3). According to such a manufacturing method, a zoom optical system that is bright and has good optical performance while being miniaturized can be manufactured.

[0075] Next, refer to Figure 12 , a manufacturing method of the variable power optical system ZL of the second embodiment is briefly described. First, a first lens group G1 with positive optical power, a second lens group G2 with negative optical power, a third lens group G3 with positive optical power, and a rear group GR are sequentially arranged along the optical axis from the object side (step ST11). At this time, at least five lens groups including a first focusing lens group GF1 with negative optical power and a second focusing lens group GF2 with positive optical power arranged on the image side of the first focusing lens group GF1 are arranged in the rear group GR. Next, it is configured so that when the magnification is changed, the intervals between adjacent lens groups change, and the first lens group G1 is fixed relative to the image plane I (step ST12). In addition, it is configured so that when focusing, the first focusing lens group GF1 and the second focusing lens group GF2 move along the optical axis with different trajectories (step ST13). Then, each lens is arranged in the lens barrel in a manner that satisfies at least the above-mentioned conditional expressions (3) and (4) (step ST14). According to such a manufacturing method, a variable magnification optical system can be manufactured that is compact, bright, and has excellent optical performance.

[0076] Example

[0077] Hereinafter, a variable power optical system ZL according to an example of each embodiment will be described with reference to the drawings. Figure 1 、 Figure 4 、 Figure 7The present invention is a cross-sectional view showing the structure and focal power distribution of the variable magnification optical system ZL {ZL(1) to ZL(3)} of the first to third embodiments. In the cross-sectional views of the variable magnification optical system ZL(1) to ZL(3) of the first to third embodiments, arrows are used to indicate the movement direction of each lens group when zooming from the wide-angle end state (W) to the telephoto end state (T). In addition, the word "focus" and arrows are used to indicate the movement direction of the focus lens group when focusing from infinity to a close object.

[0078] exist Figure 1 、 Figure 4 and Figure 7 In the examples, each lens group is represented by a combination of the symbol G and a number, and each lens is represented by a combination of the symbol L and a number. To prevent the increase in the number and variety of symbols and numbers that would lead to complexity, each embodiment uses a unique combination of symbols and numbers to represent lens groups, etc. Therefore, even if the same combination of symbols and numbers is used in different embodiments, it does not mean that the structures are the same.

[0079] Tables 1 to 3 are shown below. Table 1 shows the parameter data for the first embodiment, Table 2 shows the parameter data for the second embodiment, and Table 3 shows the parameter data for the third embodiment. In each embodiment, the d-line (wavelength λ = 587.6 nm) and the g-line (wavelength λ = 435.8 nm) were selected as the targets for calculation of aberration characteristics.

[0080] In the "Overall Parameters" table, f represents the focal length of the entire lens system, FNO represents the F-number, ω represents the half-angle of view (in degrees), and Y represents the image height. TL represents the distance on the optical axis from the lens surface closest to the object to the lens surface closest to the image plane of the zoom optical system when focusing at infinity, plus Bf (back focal length). Bf represents the distance on the optical axis from the lens surface closest to the image plane of the zoom optical system when focusing at infinity. These values ​​are shown for the wide-angle position (W), intermediate focal length (M), and telephoto position (T).

[0081] 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 represents the radius of curvature of each optical surface (the surface with the center of curvature on the image side is a positive value), D represents the distance on the optical axis from each optical surface to the next optical surface (or image surface), i.e., the surface spacing, nd represents the refractive index of the material of the optical component for the d-line, and νd represents the Abbe number of the material of the optical component based on the d-line. The "∞" of the curvature radius represents a plane or opening, and (aperture S) represents 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 * mark is added to the surface number, and the paraxial curvature radius is shown in the curvature radius R column.

[0082] In the table of [Aspheric Surface Data], the shape of the aspheric surface shown in [Lens Parameters] 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 conic constant, and Ai represents the aspheric coefficient of the i-th order. "En" represents "×10 -n For example, 1.234E-05 = 1.234×10 -5 In addition, the second-order aspheric coefficient A2 is 0, and its record is omitted.

[0083] 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 …(A)

[0084] The [Variable Spacing Data] table shows the surface spacing at surface number i, which is labeled (Di) in the [Lens Parameters] table. The [Variable Spacing Data] table also shows the surface spacing for infinity focus and close focus. D0 represents the distance from the object to the lens surface closest to the object in a variable magnification optical system.

[0085] The table of [Lens Group Data] shows the initial surface (the surface closest to the object) and the focal length of each lens group.

[0086] In the following, in all parameter values, unless otherwise specified, the focal length f, curvature radius R, surface spacing D and other lengths are generally recorded in "mm", but since the optical system can obtain the same optical performance even if it is proportionally enlarged or reduced, it is not limited to this.

[0087] The descriptions so far are common to all embodiments, and repeated descriptions are omitted below.

[0088] (First embodiment)

[0089] For the first embodiment, use Figures 1 to 3 and Table 1 for explanation. Figure 1This is a diagram showing the lens structure of the zoom optical system of the first embodiment. The zoom optical system ZL (1) of 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, a sixth lens group G6 with positive optical focal length, a seventh lens group G7 with positive optical focal length, an eighth lens group G8 with negative optical focal length, and a ninth lens group G9 with positive optical focal length, which are arranged in sequence from the object side along the optical axis. When zooming from the wide-angle end state (W) to the telephoto end state (T), the second lens group G2, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 are arranged as follows. Figure 1 As shown by the arrows, the lens groups move along the optical axis, changing the spacing between adjacent lens groups. Furthermore, during zooming, the first lens group G1, the third lens group G3, and the ninth lens group G9 are fixed relative to the image plane I. Furthermore, an aperture stop S is disposed between the third lens group G3 and the fourth lens group G4. During zooming, the aperture stop S, along with the third lens group G3, is fixed relative to the image plane I. The symbol (+) or (-) appended to each lens group number indicates the optical power of each lens group, and this applies to all of the following embodiments.

[0090] The first lens group G1 is composed of a cemented positive lens formed by a negative meniscus lens L11 with a convex surface facing the object side and a biconvex positive lens L12, which are arranged in order from the object side along the optical axis, and a positive meniscus lens L13 with a convex surface facing the object side.

[0091] The second lens group G2 is composed of a meniscus-shaped negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a meniscus-shaped positive lens L23 with a convex surface facing the object side, and a biconcave negative lens L24, which are arranged in sequence from the object side along the optical axis.

[0092] The third lens group G3 is composed of a meniscus-shaped positive lens L31 with the convex surface facing the object side, a meniscus-shaped positive lens L32 with the convex surface facing the object side, and a cemented positive lens formed by cementing a meniscus-shaped negative lens L33 with the convex surface facing the object side and a meniscus-shaped positive lens L34 with the convex surface facing the object side, which are arranged in sequence along the optical axis from the object side.

[0093] The fourth lens group G4 is composed of a biconcave negative lens L41 arranged in order from the object side along the optical axis, and a cemented negative lens formed by cementing a biconcave negative lens L42 and a meniscus positive lens L43 with a convex surface facing the object side.

[0094] The fifth lens group G5 is composed of a biconvex positive lens L51 and a cemented positive lens formed by cementing a biconvex positive lens L52 and a biconcave negative lens L53, arranged in order from the object side along the optical axis. The object-side lens surface of the positive lens L51 is aspherical.

[0095] The sixth lens group G6 is composed of a biconvex positive lens L61.

[0096] The seventh lens group G7 consists of a positive meniscus lens L71 with its concave surface facing the object side, a negative meniscus lens L72 with its convex surface facing the object side, a cemented negative lens formed by cementing a biconvex positive lens L73 and a biconcave negative lens L74, and a biconvex positive lens L75, arranged in order from the object side along the optical axis. The image-side lens surface of the negative meniscus lens L72.

[0097] The eighth lens group G8 is composed of a negative meniscus lens L81 having a concave surface facing the object side.

[0098] The ninth lens group G9 is composed of a negative meniscus lens L91 with a concave surface facing the object side and a biconvex positive lens L92 arranged in order from the object side along the optical axis. An image surface I is arranged on the image side of the ninth lens group G9.

[0099] In this embodiment, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, the eighth lens group G8, and the ninth lens group G9 constitute the rear group GR. In the rear group GR, the fourth lens group G4 corresponds to the first focus lens group GF1, and the sixth lens group G6 corresponds to the second focus lens group GF2. In addition, the eighth lens group G8 corresponds to the third focus lens group GF3, and the ninth lens group G9 corresponds to the final lens group GE. In the wide-angle end state, when focusing from an object at infinity to an object at close distance, the first focus lens group GF1 (the fourth lens group G4) and the third focus lens group GF3 (the eighth lens group G8) move along the optical axis toward the image plane with different trajectories (movement amounts), and the second focus lens group GF2 (the sixth lens group G6) moves along the optical axis toward the object side. In the intermediate focal length state and the telephoto end state, when focusing from an object at infinity to an object at close range, the first focusing lens group GF1 (the fourth lens group G4) and the second focusing lens group GF2 (the sixth lens group G6) move along the optical axis toward the object side with different trajectories (movement amounts), and the third focusing lens group GF3 (the eighth lens group G8) moves along the optical axis toward the image plane side.

[0100] Table 1 below lists the parameter values ​​of the variable power optical system of Example 1.

[0101] (Table 1)

[0102] [Overall parameters]

[0103] [Lens parameters]

[0104] [Aspherical surface data] Page 27 κ=1.000, A4=-1.64920E-06, A6=3.15497E-10, A8=-5.63176E-13, A10=5.03223E-16 Page 37 κ=1.000, A4=-5.24407E-07, A6=1.13434E-10, A8=-1.32855E-12, A10=4.32537E-15

[0105] [Variable interval data]

[0106] [Lens group data]

[0107] Figure 2 These are diagrams showing various aberrations of the variable power optical system of Example 1 when focusing at infinity at the wide-angle end. Figure 3 These are the various aberration diagrams when focusing at infinity in the telephoto end state of the zoom optical system of the first embodiment. In each aberration diagram, FNO represents the F value, and Y represents the image height. In addition, the value of the F value corresponding to the maximum aperture is shown in the spherical aberration diagram, the maximum value of the image height is shown in the astigmatism diagram and the distortion diagram, respectively, and the value of each image height is shown in the coma diagram. 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 various embodiments shown below, the same symbols as those of the present embodiment are used, and repeated descriptions are omitted.

[0108] As can be seen from the various aberration diagrams, the variable power optical system of the first embodiment corrects various aberrations well from the wide-angle end state to the telephoto end state, and has excellent imaging performance.

[0109] (Second embodiment)

[0110] For the second embodiment, use Figures 4 to 6 and Table 2 for explanation. Figure 4This is a diagram showing the lens structure of the zoom optical system of the second embodiment. The zoom optical system ZL (2) of the second 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, a sixth lens group G6 with positive optical focal length, a seventh lens group G7 with negative optical focal length, and an eighth lens group G8 with negative optical focal length, which are arranged in sequence from the object side along the optical axis. When zooming from the wide-angle end state (W) to the telephoto end state (T), the second lens group G2, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 are arranged as follows. Figure 4 The first lens group G1, the third lens group G3, and the eighth lens group G8 are fixed relative to the image plane I during zooming. Furthermore, an aperture stop S is disposed between the third lens group G3 and the fourth lens group G4. During zooming, the aperture stop S, along with the third lens group G3, is fixed relative to the image plane I.

[0111] The first lens group G1 is composed of a cemented positive lens formed by a negative meniscus lens L11 with a convex surface facing the object side and a biconvex positive lens L12, which are arranged in order from the object side along the optical axis, and a positive meniscus lens L13 with a convex surface facing the object side.

[0112] The second lens group G2 is composed of a meniscus-shaped negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a meniscus-shaped positive lens L23 with a convex surface facing the object side, and a biconcave negative lens L24, which are arranged in sequence from the object side along the optical axis.

[0113] The third lens group G3 is composed of a meniscus-shaped positive lens L31 with the convex surface facing the object side, a meniscus-shaped positive lens L32 with the convex surface facing the object side, and a cemented positive lens formed by cementing a meniscus-shaped negative lens L33 with the convex surface facing the object side and a meniscus-shaped positive lens L34 with the convex surface facing the object side, which are arranged in sequence along the optical axis from the object side.

[0114] The fourth lens group G4 is composed of a meniscus-shaped negative lens L41 with its convex surface facing the object side, which is arranged in sequence along the optical axis from the object side, and a cemented negative lens formed by cementing a biconcave negative lens L42 and a meniscus-shaped positive lens L43 with its convex surface facing the object side.

[0115] The fifth lens group G5 is composed of a biconvex positive lens L51 and a cemented positive lens formed by cementing a biconvex positive lens L52 and a biconcave negative lens L53, arranged in order from the object side along the optical axis. The object-side lens surface of the positive lens L51 is aspherical.

[0116] The sixth lens group G6 is composed of a biconvex positive lens L61.

[0117] The seventh lens group G7 consists of a biconvex positive lens L71, arranged in order from the object side along the optical axis; a negative meniscus lens L72 with its convex surface facing the object; a cemented negative lens formed by cementing a positive meniscus lens L73 with its concave surface facing the object side and a biconcave negative lens L74; and a biconvex positive lens L75. The image-side lens surface of the negative meniscus lens L72 is aspherical.

[0118] The eighth lens group G8 is composed of a negative meniscus lens L81 with a concave surface facing the object side and a biconvex positive lens L82 arranged in order from the object side along the optical axis. An image surface I is arranged on the image side of the eighth lens group G8.

[0119] In this embodiment, the 4th lens group G4, the 5th lens group G5, the 6th lens group G6, the 7th lens group G7 and the 8th lens group G8 constitute the rear group GR. In the rear group GR, the 4th lens group G4 is equivalent to the 1st focusing lens group GF1, and the 6th lens group G6 is equivalent to the 2nd focusing lens group GF2. In addition, the 8th lens group G8 is equivalent to the final lens group GE. In the wide-angle end state and the intermediate focal length state, when focusing from an object at infinity to an object at a close distance, the 1st focusing lens group GF1 (4th lens group G4) and the 2nd focusing lens group GF2 (6th lens group G6) move along the optical axis toward the object side with different trajectories (movement amounts). In the telephoto end state, when focusing from an object at infinity to an object at a close distance, only the 2nd focusing lens group GF2 (6th lens group G6) moves along the optical axis toward the object side.

[0120] Table 2 below lists the parameter values ​​of the variable power optical system of Example 2.

[0121] (Table 2)

[0122] [Overall parameters]

[0123] [Lens parameters]

[0124] [Aspherical surface data] Page 27 κ=1.000, A4=-2.00672E-06, A6=2.68755E-10, A8=-3.53434E-13, A10=2.25579E-16 Page 37 κ=1.000, A4=-6.78662E-07, A6=-6.07215E-10, A8=-3.52567E-13, A10=6.36352E-16

[0125] [Variable interval data]

[0126] [Lens group data]

[0127] Figure 5 These are diagrams showing various aberrations of the variable power optical system of Example 2 when focusing at infinity at the wide-angle end. Figure 6 These are diagrams of various aberrations of the variable power optical system of Example 2 at the telephoto end, when focusing at infinity. As can be seen from these diagrams, the variable power optical system of Example 2 has excellent aberration correction from the wide-angle end to the telephoto end, resulting in excellent imaging performance.

[0128] (Third embodiment)

[0129] For the third embodiment, use Figures 7 to 9 and Table 3 for explanation. Figure 7 This is a diagram showing the lens structure of the zoom optical system of the third embodiment. The zoom optical system ZL (3) of 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 negative optical focal length, a fifth lens group G5 with negative optical focal length, a sixth lens group G6 with positive optical focal length, a seventh lens group G7 with positive optical focal length, an eighth lens group G8 with negative optical focal length, and a ninth lens group G9 with negative optical focal length, which are arranged in sequence from the object side along the optical axis. When zooming from the wide-angle end state (W) to the telephoto end state (T), the second lens group G2, the third lens group G3, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 are arranged as follows. Figure 7 The first lens group G1, the fourth lens group G4, and the ninth lens group G9 are fixed relative to the image plane I during zooming. Furthermore, an aperture stop S is disposed between the third lens group G3 and the fourth lens group G4. During zooming, the aperture stop S and the fourth lens group G4 are both fixed relative to the image plane I.

[0130] The first lens group G1 is composed of a cemented positive lens formed by a negative meniscus lens L11 with a convex surface facing the object side and a biconvex positive lens L12, which are arranged in order from the object side along the optical axis, and a positive meniscus lens L13 with a convex surface facing the object side.

[0131] The second lens group G2 is composed of a meniscus-shaped negative lens L21 with a convex surface facing the object side, a biconcave negative lens L22, a meniscus-shaped positive lens L23 with a convex surface facing the object side, and a biconcave negative lens L24, which are arranged in sequence from the object side along the optical axis.

[0132] The third lens group G3 is composed of a biconvex positive lens L31 and a meniscus positive lens L32 whose convex surface faces the object side, which are arranged in order from the object side along the optical axis.

[0133] The fourth lens group G4 is composed of a cemented negative lens formed by cementing, in order from the object side along the optical axis, a negative meniscus lens L41 having a convex surface facing the object side and a positive meniscus lens L42 having a convex surface facing the object side.

[0134] The fifth lens group G5 is composed of a biconcave negative lens L51, a meniscus negative lens L52 with a convex surface facing the object side, and a meniscus positive lens L53 with a convex surface facing the object side, which are arranged in order from the object side along the optical axis.

[0135] The sixth lens group G6 is composed of a biconvex positive lens L61 arranged in order from the object side along the optical axis, and a cemented positive lens formed by cementing a meniscus negative lens L62 with a convex surface facing the object side and a biconvex positive lens L63.

[0136] The seventh lens group G7 is composed of a positive meniscus lens L71 having a convex surface facing the object side.

[0137] The eighth lens group G8 is composed of a meniscus-shaped negative lens L81 with a convex surface facing the object side and a biconvex positive lens L82, arranged in order from the object side along the optical axis. The object-side lens surface of the meniscus-shaped negative lens L81 is aspherical.

[0138] The ninth lens group G9 consists of a negative meniscus lens L91 with its concave surface facing the object, and a biconvex positive lens L92, arranged in order from the object side along the optical axis. The object-side lens surface of the negative meniscus lens L91 is aspherical. Image surface I is located on the image side of the ninth lens group G9.

[0139] In this embodiment, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, the eighth lens group G8, and the ninth lens group G9 constitute the rear group GR. In the rear group GR, the fifth lens group G5 corresponds to the first focusing lens group GF1, and the seventh lens group G7 corresponds to the second focusing lens group GF2. In addition, the ninth lens group G9 corresponds to the final lens group GE. In the wide-angle end state, the intermediate focal length state, and the telephoto end state, when focusing from an object at infinity to an object at a close distance, the first focusing lens group GF1 (fifth lens group G5) and the second focusing lens group GF2 (seventh lens group G7) move along the optical axis toward the object side with different trajectories (movement amounts).

[0140] Table 3 below lists the parameter values ​​of the variable power optical system of Example 3.

[0141] (Table 3)

[0142] [Overall parameters]

[0143] [Lens parameters]

[0144] [Aspherical surface data] Page 35 κ=1.000, A4=4.10175E-06, A6=1.87631E-10, A8=1.07919E-12, A10=0.00000E+00 Page 39 κ=1.000, A4=1.01290E-06, A6=-7.68488E-09, A8=3.60877E-11, A10=-8.29554E-14

[0145] [Variable interval data]

[0146] [Lens group data]

[0147] Figure 8 These are diagrams showing various aberrations of the variable power optical system of Example 3 when focusing at infinity at the wide-angle end. Figure 9These are diagrams of various aberrations of the zoom optical system of Example 3 at the telephoto end, when focusing at infinity. As can be seen from these diagrams, the zoom optical system of Example 3 has excellent aberration correction from the wide-angle end to the telephoto end, resulting in excellent imaging performance.

[0148] Next, a table of [conditional expression corresponding values] is shown below. In this table, values ​​corresponding to the conditional expressions (1) to (12) are collectively shown for all examples (first to third examples).

[0149] Conditional formula (1) 0.05<(-f2) / f1<1.00

[0150] Conditional expression (2) 0.02<Bft / ft<0.15

[0151] Conditional formula (3) 0.10<(-fF1) / fF2<1.30

[0152] Conditional formula (4) 0.01<Bfw / fw<0.50

[0153] Conditional formula (5) 0.50<f2 / fF1<1.00

[0154] Conditional formula (6) 1.20<f1 / fF2<2.00

[0155] Conditional formula (7) 0.50<f3 / fF2<1.00

[0156] Conditional formula (8) 2.00<TLw / fw<6.00

[0157] Conditional formula (9) 0.01<(-f2) / f3<2.00

[0158] Conditional formula (10) 1.80<f1 / f3<2.50

[0159] Conditional formula (11) 0.01<|fr1 / fr|<5.00

[0160] Conditional formula (12) 0.10<f2 / fr1<0.75

[0161] [Conditional Expression Corresponding Value] (First to Third Embodiments)

[0162] According to the above-described embodiments, a variable magnification optical system that is compact, bright, and has excellent optical performance can be realized.

[0163] The above-mentioned embodiments are merely specific examples of the present invention, and the present invention is not limited thereto.

[0164] The following contents can be appropriately adopted within the range that does not affect the optical performance of the variable power optical system of each embodiment.

[0165] While examples of the variable power optical systems of each embodiment are shown with 8-group and 9-group structures, the present application is not limited thereto, and variable power optical systems with other group structures (e.g., 10-group, 11-group, 12-group, etc.) may also be configured. For example, a structure may include an additional lens or lens group on the object side or image side of the variable power optical system of each embodiment. Another example may include an additional lens or lens group on the object side or image side of the rear group of the variable power optical system of each embodiment. Furthermore, a lens group refers to a portion comprising at least one lens, separated by air spaces that change during zooming.

[0166] In the variable magnification optical system of each embodiment, the first to third focus lens groups described above are not limited thereto. Alternatively, a single lens group, multiple lens groups, or a portion of a lens group may be used as a focus lens group that moves along the optical axis to focus from an object at infinity to an object at a close distance. The focus lens group can be used for both autofocus and motor drive (using an ultrasonic motor, etc.) for autofocus.

[0167] The anti-shake lens group can correct image shake caused by hand shaking by causing the lens group or part of the lens group to move with a component in a direction perpendicular to the optical axis or to rotate (swing) in a plane including the optical axis.

[0168] The lens surface can be spherical, flat, or aspherical. Spherical or flat lens surfaces are preferred because they facilitate lens processing, assembly, and adjustment, and prevent degradation of optical performance due to these processes. Furthermore, even in the event of image plane displacement, degradation of imaging performance is minimized, making this a preferred option.

[0169] In the case of an aspheric lens surface, the aspheric surface can be any of the following: a polished aspheric surface, a glass molded aspheric surface formed by molding glass into an aspheric shape, or a composite aspheric surface formed by molding resin onto the glass surface into an aspheric shape. Furthermore, the lens surface can also function as a diffractive surface, and the lens can be a distributed refractive index lens (GRIN lens) or a plastic lens.

[0170] The aperture stop is preferably disposed between the third lens group and the fourth lens group, but a member serving as the aperture stop may be omitted and its function may be replaced by the lens frame.

[0171] In order to reduce glare and ghosting and achieve high-contrast optical performance, an anti-reflection coating with high transmittance in a wide band can be applied to each lens surface.

[0172] Label Description 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 7th lens group G8 8th lens group G9 9th lens group I Image plane S Aperture stop

Claims

1. A variable magnification optical system, wherein: The variable power optical system is composed of a first lens group with positive optical power, a second lens group with negative optical power, a third lens group with positive optical power, and a rear lens group having at least five lens groups arranged in sequence from the object side along the optical axis. When changing magnification, the intervals between adjacent lens groups change, and the first lens group is fixed relative to the image plane. The variable magnification optical system satisfies the following conditional formula: 0.05<(-f2) / f1<1.00 0.02<Bft / ft<0.15 Wherein, f1: focal length of the first lens group, f2: focal length of the second lens group, ft: focal length of the zoom optical system at the telephoto end, Bft: back focal length of the variable magnification optical system in the telephoto end state.

2. The variable magnification optical system according to claim 1, wherein: The variable magnification optical system satisfies the following conditional formula: 0.01<Bfw / fw<0.50 Wherein, fw: focal length of the variable magnification optical system in the wide-angle end state, Bfw: The back focal length of the variable magnification optical system in the wide-angle end state.

3. The variable magnification optical system according to claim 1 or 2, wherein: The at least five lens groups of the rear group include a first focusing lens group having negative refractive power and a second focusing lens group disposed on the image side of the first focusing lens group and having positive refractive power. During focusing, the first focusing lens group and the second focusing lens group move along the optical axis in different tracks. The variable magnification optical system satisfies the following conditional formula: 0.10<(-fF1) / fF2<1.30 Wherein, fF1: the focal length of the first focusing lens group, fF2: focal length of the second focusing lens group.

4. A variable magnification optical system, wherein: The variable power optical system is composed of a first lens group with positive optical power, a second lens group with negative optical power, a third lens group with positive optical power, and a rear lens group having at least five lens groups arranged in sequence from the object side along the optical axis. When changing magnification, the intervals between adjacent lens groups change, and the first lens group is fixed relative to the image plane. The at least five lens groups of the rear group include a first focusing lens group having negative refractive power and a second focusing lens group disposed on the image side of the first focusing lens group and having positive refractive power. During focusing, the first focusing lens group and the second focusing lens group move along the optical axis in different tracks. The variable magnification optical system satisfies the following conditional formula: 0.10<(-fF1) / fF2<1.30 0.01<Bfw / fw<0.50 Wherein, fF1: the focal length of the first focusing lens group, fF2: focal length of the second focusing lens group, fw: focal length of the variable magnification optical system at the wide-angle end, Bfw: The back focal length of the variable magnification optical system in the wide-angle end state.

5. The variable magnification optical system according to claim 3 or 4, wherein: The variable magnification optical system satisfies the following conditional formula: 0.50<f2 / fF1<1.00 Wherein, f2 is the focal length of the second lens group.

6. The variable magnification optical system according to any one of claims 3 to 5, wherein: The variable magnification optical system satisfies the following conditional formula: 1.20<f1 / fF2<2.00 Wherein, f1 is the focal length of the first lens group.

7. The variable magnification optical system according to any one of claims 3 to 6, wherein: The variable magnification optical system satisfies the following conditional formula: 0.50<f3 / fF2<1.00 Wherein, f3 is the focal length of the third lens group.

8. The variable magnification optical system according to any one of claims 3 to 7, wherein: The second focusing lens group is composed of one lens component.

9. The variable magnification optical system according to any one of claims 1 to 8, wherein: The variable magnification optical system satisfies the following conditional formula: 2.00<TLw / fw<6.00 Wherein, fw: focal length of the variable magnification optical system in the wide-angle end state, TLw: The total length of the variable power optical system in the wide-angle end state.

10. The variable magnification optical system according to any one of claims 1 to 9, wherein: The variable magnification optical system satisfies the following conditional formula: 0.01<(-f2) / f3<2.00 Wherein, f2: focal length of the second lens group, f3: focal length of the third lens group.

11. The variable magnification optical system according to any one of claims 1 to 10, wherein: The variable magnification optical system satisfies the following conditional formula: 1.80<f1 / f3<2.50 Wherein, f1: focal length of the first lens group, f3: focal length of the third lens group.

12. The variable magnification optical system according to any one of claims 1 to 11, wherein: The at least five lens groups of the rear group include a final lens group disposed closest to the image plane side. The variable magnification optical system satisfies the following conditional formula: 0.01<|fr1 / fr|<5.00 Where, fr: focal length of the final lens group, fr1: The focal length of the lens group in the rear group arranged on the object side of the final lens group.

13. The variable magnification optical system according to any one of claims 1 to 12, wherein: The at least five lens groups of the rear group include a final lens group disposed closest to the image plane side. The variable magnification optical system satisfies the following conditional formula: 0.10<f2 / fr1<0.75 Wherein, f2: focal length of the second lens group, fr1: The focal length of the lens group in the rear group arranged on the object side of the final lens group.

14. The variable magnification optical system according to any one of claims 1 to 13, wherein: The at least five lens groups of the rear group include a final lens group disposed closest to the image plane side. During zooming, the final lens group is fixed relative to the image plane.

15. The variable magnification optical system according to any one of claims 1 to 14, wherein: The at least five lens groups of the rear group include a final lens group disposed closest to the image plane side. The final lens group is composed of a negative lens and a positive lens arranged in this order from the object side along the optical axis. 16 . An optical device comprising the variable power optical system according to claim 1 .

17. A method for manufacturing a variable magnification optical system, the variable magnification optical system comprising a first lens group having positive optical power, a second lens group having negative optical power, a third lens group having positive optical power, and a rear lens group having at least five lens groups arranged in sequence along an optical axis from the object side, wherein: The method for manufacturing the variable magnification optical system comprises the steps of arranging each lens in the lens barrel in the following manner: When changing magnification, the intervals between adjacent lens groups change, and the first lens group is fixed relative to the image plane. The variable magnification optical system satisfies the following conditional expression, namely, 0.05<(-f2) / f1<1.00 0.02<Bft / ft<0.15 Wherein, f1: focal length of the first lens group, f2: focal length of the second lens group, ft: focal length of the zoom optical system at the telephoto end, Bft: back focal length of the variable magnification optical system in the telephoto end state.

18. A method for manufacturing a variable magnification optical system, the variable magnification optical system comprising a first lens group with positive optical power, a second lens group with negative optical power, a third lens group with positive optical power, and a rear lens group having at least five lens groups arranged in sequence along an optical axis from the object side, wherein: The method for manufacturing the variable magnification optical system comprises the steps of arranging each lens in the lens barrel in the following manner: When changing magnification, the intervals between adjacent lens groups change, and the first lens group is fixed relative to the image plane. The at least five lens groups of the rear group include a first focusing lens group having negative refractive power and a second focusing lens group disposed on the image side of the first focusing lens group and having positive refractive power. During focusing, the first focusing lens group and the second focusing lens group move along the optical axis in different tracks. The variable magnification optical system satisfies the following conditional expression, namely, 0.10<(-fF1) / fF2<1.30 0.01<Bfw / fw<0.50 Wherein, fF1: the focal length of the first focusing lens group, fF2: focal length of the second focusing lens group, fw: focal length of the variable magnification optical system at the wide-angle end, Bfw: The back focal length of the variable magnification optical system in the wide-angle end state.

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