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

Abstract

This variable power optical system (ZL) has, in order from the object side, a first lens group (G1) having positive refractive power, and a rear group (GR) having a plurality of lens groups. When zooming, the distance between adjacent lens groups changes, and the first lens group is fixed with respect to an image plane (IP). The first lens group is composed of one or a plurality of convex lenses, and satisfies the following conditional expression.　0.01 < Df / TLt < 0.20, where Df is the radius of the outer diameter of a final lens disposed closest to the image side in the variable power optical system, and TLt is the total lens length of the variable power optical system at the telephoto end.

Description

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

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

[0002] Variable magnification optical systems suitable for photographic cameras, electronic still cameras, video cameras, etc. have been proposed (see, for example, Patent Document 1). Such variable magnification optical systems are required to be lightweight and compact, yet have high optical performance with various aberrations well corrected.

[0003] Special Publication No. 07-001332

[0004] A variable magnification optical system according to the present invention has, arranged in order from the object side, a first lens group having positive refractive power and a rear group having a plurality of lens groups, wherein the spacing between adjacent lens groups changes during magnification variation, the first lens group is fixed relative to the image plane, the first lens group is made up of one or a plurality of convex lenses, and satisfies the following condition: 0.01 < Df / TLt < 0.20, where Df is the outer radius of the final lens arranged closest to the image side in the variable magnification optical system, and TLt is the total lens length of the variable magnification optical system at the telephoto end.

[0005] An optical apparatus according to the present invention is configured to include the variable magnification optical system described above.

[0006] A method for manufacturing a variable magnification optical system according to the present invention includes, in order from the object side, a first lens group having positive refractive power and a rear group having a plurality of lens groups, the spacing between adjacent lens groups changing during magnification variation, and the first lens group being fixed relative to an image plane, and includes the steps of configuring the first lens group to consist of one or more convex lenses, and arranging the lenses in a lens barrel so as to satisfy the following condition: 0.01<Df / TLt<0.20 where D: outer radius of the final lens arranged closest to the image side in the variable magnification optical system TLt: total lens length of the variable magnification optical system at the telephoto end

[0007] FIG. 1 is a diagram showing the lens configuration of a variable magnification optical system according to Example 1. FIG. 2 is a diagram showing various aberrations of the variable magnification optical system according to Example 1 when focusing on infinity at the wide-angle end. FIG. 3 is a diagram showing various aberrations of the variable magnification optical system according to Example 1 when focusing on infinity at the telephoto end. FIG. 4 is a diagram showing the lens configuration of a variable magnification optical system according to Example 2. FIG. 5 is a diagram showing various aberrations of the variable magnification optical system according to Example 2 when focusing on infinity at the wide-angle end. FIG. 6 is a diagram showing various aberrations of the variable magnification optical system according to Example 3 when focusing on infinity at the wide-angle end. FIG. 7 is a diagram showing various aberrations of the variable magnification optical system according to Example 3 when focusing on infinity at the telephoto end. FIG. 8 is a diagram showing the lens configuration of a variable magnification optical system according to Example 4. FIG. 9 is a diagram showing various aberrations of the variable magnification optical system according to Example 4 when focusing on infinity at the wide-angle end. FIG. 10 is a diagram showing various aberrations of the variable magnification optical system according to Example 1 when focusing on infinity at the telephoto end. FIG. 11 is a diagram showing the lens configuration of a variable magnification optical system according to Example 15. Fig. 10 is a diagram illustrating various aberrations when the variable magnification optical system according to Example 5 is focused on infinity at the wide-angle end. Fig. 11 is a diagram illustrating various aberrations when the variable magnification optical system according to Example 5 is focused on infinity at the telephoto end. Fig. 12 is a diagram illustrating the configuration of a camera equipped with the variable magnification optical system according to each embodiment. Fig. 13 is a flowchart illustrating a method for manufacturing the variable magnification optical system according to each embodiment.

[0008] Preferred embodiments of the present invention will now be described. First, a camera (optical device) equipped with a variable magnification optical system according to each embodiment will be described with reference to FIG. 11 . As shown in FIG. 11 , this camera 1 comprises a body 2 and a photographic lens 3 attached to the body 2. The body 2 comprises an image sensor 4, a body control unit (not shown) that controls the operation of the digital camera, and an LCD screen 5. The photographic lens 3 comprises a variable magnification optical system ZL consisting 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 comprises a sensor that detects the position of the lens groups, a motor that moves the lens groups back and forth along the optical axis, a control circuit that drives the motor, and the like. The image sensor 4 is a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor that receives and photoelectrically converts an optical image formed by the variable magnification optical system ZL of the photographic lens 3.

[0009] Light from a subject is collected by the variable magnification optical system ZL of the photographing lens 3 and reaches the image plane I of the image sensor 4. The light from the subject that reaches the image plane IP is photoelectrically converted by the image sensor 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 in response to a user operation. Note that this camera may be a mirrorless camera or a single-lens reflex camera with a quick-return mirror. The variable magnification optical system ZL shown in FIG. 11 is a schematic representation of an optical system provided in the photographing lens 3, and the lens configuration of the variable magnification optical system ZL is not limited to this configuration.

[0010] Next, a variable magnification optical system ZL according to this embodiment will be described. A variable magnification optical system ZL(1), which is an example of the variable magnification optical system ZL according to this embodiment, has, as shown in FIG. 1 , a first lens group G1 having positive refractive power and a rear group GR having multiple lens groups, arranged in order from the object side along the optical axis. The spacing between adjacent lens groups changes during magnification, and the first lens group G1 is fixed relative to the image plane IP during magnification. The first lens group G1 is made up of one or more convex lenses.

[0011] With the above configuration, the variable magnification optical system ZL according to this embodiment satisfies the following conditional expression (1): 0.01<Df / TLt<0.20 (1) where Df is the outer radius of the final lens located closest to the image in the variable magnification optical system ZL, and TLt is the total lens length of the variable magnification optical system ZL at the telephoto end.

[0012] The total lens length of the variable magnification optical system ZL is the distance on the optical axis from the object-side lens surface of the lens located closest to the object (the lens surface closest to the object) in the variable magnification optical system ZL to the image plane IP.

[0013] According to this embodiment, it is possible to provide a variable magnification optical system ZL that is lightweight and compact, yet has high optical performance that can correct various aberrations such as field curvature, chromatic aberration, etc. The variable magnification optical system ZL according to this embodiment may be the variable magnification optical system ZL(2) shown in Fig. 3, the variable magnification optical system ZL(3) shown in Fig. 5, the variable magnification optical system ZL(4) shown in Fig. 7, or the variable magnification optical system ZL(5) shown in Fig. 9.

[0014] Conditional expression (1) defines an appropriate relationship between the outer radius of the final lens in the variable magnification optical system ZL and the overall lens length at the telephoto end of the variable magnification optical system ZL. By satisfying conditional expression (1), it is possible to achieve both a compact variable magnification optical system ZL and high optical performance in which various aberrations such as field curvature and chromatic aberration are corrected.

[0015] If the corresponding value of conditional expression (1) exceeds the upper limit, the outer diameter of the final lens element becomes large relative to the overall lens length at the telephoto end. This results in a larger lens shape for the final lens element, resulting in a larger variable-magnification optical system ZL. By setting the upper limit of conditional expression (1) to 0.18, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the upper limit of conditional expression (1) may be set to 0.16, 0.14, 0.12, or even 0.10.

[0016] If the corresponding value of conditional expression (1) falls below the lower limit, the outer diameter of the final lens element becomes small relative to the overall lens length at the telephoto end. This makes it difficult to apply the lens to a wide range of imaging surfaces. By setting the lower limit of conditional expression (1) to 0.015, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the lower limit of conditional expression (1) may be set to 0.02, 0.03, 0.04, or even 0.045.

[0017] The variable magnification optical system ZL according to this embodiment is preferably made up of one or two single lenses, which is desirable because it makes it possible to provide a lightweight variable magnification optical system ZL.

[0018] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (2): 0.30 < f1 / ft < 1.50 ... (2) where, f1: focal length of the first lens group G1, ft: focal length of the variable magnification optical system ZL at the telephoto end

[0019] Conditional expression (2) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the variable magnification optical system ZL at the telephoto end. Satisfying conditional expression (2) is desirable because it makes it possible to achieve both a compact variable magnification optical system ZL and high optical performance in which various aberrations such as curvature of field and chromatic aberration are corrected.

[0020] If the corresponding value of conditional expression (2) exceeds the upper limit, the focal length of the first lens group G1 becomes larger than the focal length of the variable magnification optical system ZL at the telephoto end. This results in a larger lens shape for the first lens group G1, which undesirably increases the size of the variable magnification optical system ZL. By setting the upper limit of conditional expression (2) to 1.45, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the upper limit of conditional expression (2) may be set to 1.35, 1.25, 1.15, or even 1.10.

[0021] If the corresponding value of conditional expression (2) falls below the lower limit, the focal length of the first lens group G1 becomes shorter than the focal length of the variable magnification optical system ZL at the telephoto end. This increases the power of each lens constituting the first lens group G1, resulting in higher-order spherical aberration, coma, field curvature, and distortion, making it difficult to correct these aberrations, which is undesirable. Setting the lower limit of conditional expression (2) to 0.40 further ensures the effects of this embodiment. To further ensure the effects of this embodiment, the lower limit of conditional expression (2) may be set to 0.45, 0.55, 0.60, or even 0.70.

[0022] In the variable magnification optical system ZL according to this embodiment, it is desirable that the lens having the smallest dispersion in the first lens group G1 satisfy the following conditional expressions (3) and (4): nd1min<1.70 (3) 63.00<νd1min (4) where, nd1min: refractive index for the d-line of the lens having the smallest dispersion in the first lens group G1 νd1min: Abbe number for the d-line of the lens having the smallest dispersion in the first lens group G1

[0023] Furthermore, it is more desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (3a) which sets a lower limit and the following conditional expression (4a) which sets an upper limit: 1.40<nd1min<1.70 (3a) 63.00<νd1min<100.00 (4a)

[0024] Conditional expressions (3) and (3a) define the refractive index for the d-line of the lens in the first lens group G1 that has the smallest dispersion. Satisfying conditional expression (3) or (3a) is desirable because it enables favorable correction of chromatic aberration.

[0025] It is undesirable for the corresponding values ​​of conditional expressions (3) and (3a) to exceed the upper limit values, since chromatic aberration cannot be corrected well. By setting the upper limit values ​​of conditional expressions (3) and (3a) to 1.680, the effects of this embodiment can be more reliably achieved. To further ensure the effects of this embodiment, the upper limit values ​​of conditional expressions (3) and (3a) may be set to 1.660, 1.640, 1.620, or even 1.600.

[0026] If the corresponding value of conditional expression (3a) falls below the lower limit, chromatic aberration cannot be corrected satisfactorily, which is undesirable. By setting the lower limit of conditional expression (3a) to 1.405, the effect of this embodiment can be more reliably achieved. To further ensure the effect of this embodiment, the lower limit of conditional expression (3a) may be set to 1.410, 1.415, 1.420, or even 1.425.

[0027] Conditional expressions (4) and (4a) define the Abbe number for the d-line of the lens in the first lens group G1 that has the smallest dispersion. Satisfying conditional expression (4) or (4a) is desirable because it enables favorable correction of chromatic aberration.

[0028] If the corresponding value of conditional expression (4a) exceeds the upper limit, it becomes impossible to effectively correct chromatic aberration, which is undesirable. By setting the upper limit of conditional expression (4a) to 99.00, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the upper limit of conditional expression (4a) may be set to 98.00, 97.00, 96.00, or even 95.50.

[0029] It is undesirable for the corresponding values ​​of conditional expressions (4) and (4a) to fall below the lower limit values, since chromatic aberration cannot be effectively corrected. By setting the lower limit values ​​of conditional expressions (4) and (4a) to 63.80, the effects of this embodiment can be more reliably achieved. To further ensure the effects of this embodiment, the lower limit values ​​of conditional expressions (4) and (4a) may be set to 64.60, 65.40, 66.20, or even 68.90.

[0030] In the variable magnification optical system ZL according to this embodiment, it is desirable that the lens group arranged closest to the image side is fixed with respect to the image plane IP during magnification variation, as this ensures the robustness of the variable magnification optical system ZL.

[0031] In the variable magnification optical system ZL according to this embodiment, it is desirable that the rear group GR have a fixed lens group with positive refractive power that is fixed relative to the image plane IP during magnification variation, and an aperture stop SP that is arranged closer to the image plane than the fixed lens group.

[0032] This is desirable because it allows for good correction of various aberrations while ensuring the smooth operation of the lens barrel's mechanical components.

[0033] In the variable magnification optical system ZL according to this embodiment, the rear group GR includes a second lens group G2 and a third lens group G3 arranged in that order from the object side, and it is desirable that the second lens group G2 and the third lens group G3 move toward the image side during magnification variation.

[0034] This is desirable because it allows for the maintenance of the magnification ratio and the suppression of chromatic aberration variations at different lens positions along the optical axis that accompany the magnification.

[0035] In the variable magnification optical system ZL according to this embodiment, it is desirable that the rear group GR has a plurality of lens groups, each consisting of a single lens, and an aperture stop SP arranged on the image side of the plurality of lens groups.

[0036] This is desirable because it allows for good correction of various aberrations while ensuring the smooth operation of the lens barrel's mechanical components.

[0037] It is desirable that the variable magnification optical system ZL according to this embodiment satisfy the following conditional expression (5): 0.80<ft / fw<4.00 (5) where ft is the focal length of the variable magnification optical system ZL at the telephoto end, and fw is the focal length of the variable magnification optical system ZL at the wide-angle end.

[0038] Conditional expression (5) defines an appropriate relationship between the focal length of the variable magnification optical system ZL at the telephoto end and the focal length of the variable magnification optical system ZL at the wide-angle end. Satisfying conditional expression (5) is desirable because it makes it possible to achieve a variable magnification optical system ZL that is lightweight yet has high optical performance.

[0039] If the corresponding value of conditional expression (5) exceeds the upper limit, the focal length of the variable magnification optical system ZL at the telephoto end becomes larger than the focal length of the variable magnification optical system ZL at the wide-angle end. This makes it difficult to ensure optical performance across the entire range from the wide-angle end to the telephoto end, which is undesirable. By setting the upper limit of conditional expression (5) to 3.60, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the upper limit of conditional expression (5) may be set to 3.50, 3.30, 3.00, or even 2.80.

[0040] If the corresponding value of conditional expression (5) falls below the lower limit, the focal length of the variable-magnification optical system ZL at the telephoto end becomes smaller than the focal length of the variable-magnification optical system ZL at the wide-angle end. This makes it difficult to achieve an optical system with an appropriate weight relative to the magnification ratio, which is undesirable. By setting the lower limit of conditional expression (5) to 1.00, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the lower limit of conditional expression (5) may be set to 1.20, 1.40, 1.65, or even 1.85.

[0041] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (6): 0.05 < BFt / ft < 0.20 ... (6) where, BFt: back focus of the variable magnification optical system ZL at the telephoto end, ft: focal length of the variable magnification optical system ZL at the telephoto end.

[0042] Conditional expression (6) defines an appropriate relationship between the back focus of the variable magnification optical system ZL at the telephoto end and the focal length of the variable magnification optical system ZL at the telephoto end. Satisfying conditional expression (6) is desirable because it makes it possible to achieve a variable magnification optical system ZL that can provide good optical performance while achieving compactness.

[0043] If the corresponding value of conditional expression (6) exceeds the upper limit, the back focus of the variable magnification optical system ZL at the telephoto end becomes large relative to the focal length of the variable magnification optical system ZL at the telephoto end. This undesirably increases the size of the variable magnification optical system ZL. By setting the upper limit of conditional expression (6) to 0.188, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the upper limit of conditional expression (6) may be set to 0.175, 0.160, 0.150, or even 0.140.

[0044] If the corresponding value of conditional expression (6) falls below the lower limit, the back focus of the variable magnification optical system ZL at the telephoto end becomes smaller relative to the focal length of the variable magnification optical system ZL at the telephoto end. This undesirably increases the diameter of the final lens and makes it heavier. By setting the lower limit of conditional expression (6) to 0.055, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the lower limit of conditional expression (6) may be set to 0.060, 0.065, 0.070, or even 0.075.

[0045] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (7): 0.70 < ft / TLt < 1.00 ... (7) where, ft: focal length of the variable magnification optical system ZL at the telephoto end TLt: total lens length of the variable magnification optical system ZL at the telephoto end

[0046] Conditional expression (7) defines an appropriate relationship between the focal length of the variable magnification optical system ZL at the telephoto end and the overall lens length of the variable magnification optical system ZL at the telephoto end. Satisfying conditional expression (7) is desirable because it makes it possible to achieve a variable magnification optical system ZL that can achieve good optical performance while achieving compactness.

[0047] If the corresponding value of conditional expression (7) exceeds the upper limit, the focal length of the variable magnification optical system ZL becomes large relative to the overall lens length of the variable magnification optical system ZL at the telephoto end. This makes it difficult to achieve the desired optical performance, mainly with respect to lateral chromatic aberration and axial chromatic aberration, which is undesirable. By setting the upper limit of conditional expression (7) to 0.98, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the upper limit of conditional expression (7) may be set to 0.95, 0.94, 0.92, or even 0.90.

[0048] If the corresponding value in conditional equation (7) falls below the lower limit, the focal length of the variable magnification optical system ZL becomes smaller than the total lens length of the variable magnification optical system ZL at the telephoto end. This results in the overall size of the variable magnification optical system ZL becoming larger, which is undesirable. Setting the lower limit of conditional equation (7) to 0.72 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the lower limit of conditional equation (7) may be set to 0.74, 0.75, 0.76, or even 0.78.

[0049] In the variable magnification optical system ZL according to this embodiment, the rear group GR has a stop SP, and the variable magnification optical system ZL preferably has five or more lens groups arranged closer to the object side than the stop SP.

[0050] This is desirable because it makes it possible to effectively suppress chromatic aberration fluctuations for each lens position in the optical axis direction using five or more lens groups.

[0051] In the variable magnification optical system ZL according to this embodiment, the rear group GR has an aperture SP, and it is desirable that the variable magnification optical system ZL satisfies the following condition (8): 0.50 < fAw / fw < 2.00 ... (8) where, fAw: combined focal length at the wide-angle end of the lens positioned on the object side of the aperture SP in the variable magnification optical system ZL fw: focal length of the variable magnification optical system ZL at the wide-angle end

[0052] Conditional equation (8) defines an appropriate relationship between the combined focal length at the wide-angle end of the lens positioned on the object side of the aperture SP in the variable magnification optical system ZL, and the focal length of the variable magnification optical system ZL at the wide-angle end. Satisfying conditional equation (8) is desirable because it allows for the achievement of a variable magnification optical system ZL that is miniaturized while providing good optical performance.

[0053] If the corresponding value of conditional expression (8) exceeds the upper limit, the combined focal length at the wide-angle end of the lens located on the object side of the aperture stop SP in the variable magnification optical system ZL will be larger than the focal length of the variable magnification optical system ZL at the wide-angle end. This makes it difficult to correct aberrations occurring before the aperture stop SP, and aberrations will remain throughout the variable magnification optical system ZL, which is undesirable. By setting the upper limit of conditional expression (8) to 1.925, the effects of this embodiment can be further ensured. To further ensure the effects of this embodiment, the upper limit of conditional expression (8) may be set to 1.850, 1.775, 1.700, or even 1.625.

[0054] If the corresponding value of conditional expression (8) falls below the lower limit, the combined focal length at the wide-angle end of the lens located on the object side of the aperture stop SP in the variable magnification optical system ZL will be smaller than the focal length of the variable magnification optical system ZL at the wide-angle end. This undesirably increases the overall length of the variable magnification optical system ZL in front of the aperture stop SP, thereby increasing the overall size of the variable magnification optical system ZL. Setting the lower limit of conditional expression (8) to 0.512 can further ensure the effects of this embodiment. To further ensure the effects of this embodiment, the lower limit of conditional expression (8) may be set to 0.54, 0.56, 0.60, or even 0.64.

[0055] The variable magnification optical system ZL according to this embodiment has a second positive lens group arranged closest to the object among the lens groups having positive refractive power arranged closer to the image than the first lens group G1, and a third positive lens group arranged closest to the object among the lens groups having positive refractive power arranged closer to the image than the second positive lens group, and it is desirable to satisfy the following conditional expression (9): 0.03<L23t / L23w<0.30 (9) where, L23w: the distance on the optical axis at the wide-angle end from the lens surface of the second positive lens group closest to the image to the lens surface of the third positive lens group closest to the object, L23t: the distance on the optical axis at the telephoto end from the lens surface of the second positive lens group closest to the image to the lens surface of the third positive lens group closest to the object.

[0056] Conditional equation (9) defines an appropriate relationship between the distance between the second and third positive lens groups at the wide-angle end and the distance between the second and third positive lens groups at the telephoto end. Satisfying conditional equation (9) is desirable because it allows for miniaturization while achieving a variable magnification optical system ZL with suppressed chromatic aberration fluctuations.

[0057] If the corresponding value in conditional equation (9) exceeds the upper limit, the distance between the second and third positive lens groups at the wide-angle end becomes larger than the distance between the second and third positive lens groups at the telephoto end. This is undesirable because it increases the amount of lens movement required for aberration correction, and the entire variable magnification optical system ZL becomes larger. Setting the upper limit of conditional equation (9) to 0.296 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the upper limit of conditional equation (9) may be set to 0.296, 0.290, 0.285, or even 0.280.

[0058] If the corresponding value in conditional equation (9) falls below the lower limit, the distance between the second and third positive lens groups at the wide-angle end becomes smaller than the distance between the second and third positive lens groups at the telephoto end. This makes it difficult to correct chromatic aberration variations between the wide-angle and telephoto ends, which is undesirable. Setting the lower limit of conditional equation (9) to 0.032 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the lower limit of conditional equation (9) may be set to 0.034, 0.036, 0.038, or even 0.040.

[0059] In the variable magnification optical system ZL according to this embodiment, the rear group GR has a lens group with positive refractive power that moves toward the object side when changing magnification from the wide-angle end to the telephoto end, and this lens group includes a convex lens and a concave lens, and it is desirable that this lens group satisfy the following conditional expression (10): 0.20<νp / νn<0.40 (10), where νp is the Abbe number of the convex lens included in the lens group with positive refractive power that moves toward the object side when changing magnification from the wide-angle end to the telephoto end in the rear group GR, and νn is the Abbe number of the concave lens included in the lens group with positive refractive power that moves toward the object side when changing magnification from the wide-angle end to the telephoto end in the rear group GR.

[0060] Conditional expression (10) defines an appropriate relationship between the Abbe number of the convex lens included in the lens group and the Abbe number of the concave lens included in the positive lens group. By satisfying conditional expression (10), it is possible to achieve a variable magnification optical system ZL in which chromatic aberration fluctuations are suppressed, which is desirable.

[0061] If the corresponding value of conditional expression (10) exceeds the upper limit, the Abbe number of the convex lens becomes larger than the Abbe number of the concave lens. This makes it difficult to correct chromatic aberration fluctuations between the wide-angle end and the telephoto end, which is undesirable. By setting the upper limit of conditional expression (10) to 0.385, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the upper limit of conditional expression (10) may be set to 0.370, 0.355, 0.340, or even 0.325.

[0062] If the corresponding value of conditional expression (10) falls below the lower limit, the Abbe number of the convex lens becomes smaller than the Abbe number of the concave lens. This makes it difficult to correct chromatic aberration fluctuations between the wide-angle end and the telephoto end, which is undesirable. By setting the lower limit of conditional expression (10) to 0.210, the effect of this embodiment can be further ensured. To further ensure the effect of this embodiment, the lower limit of conditional expression (10) may be set to 0.220, 0.230, 0.240, or even 0.245.

[0063] In the variable magnification optical system ZL according to this embodiment, it is desirable that the rear group GR consists of seven or more lens groups. This is desirable because it is possible to provide a variable magnification optical system ZL with high optical performance that can correct various aberrations such as field curvature and chromatic aberration.

[0064] A manufacturing method for the variable magnification optical system ZL according to this embodiment will now be described with reference to FIG. 12 . First, a first lens group G1 having positive refractive power and a rear group GR having multiple lens groups are arranged in order from the object side along the optical axis (Step ST1). Then, the first lens group G1 is configured so that the spacing between adjacent lens groups changes during magnification variation, and the first lens group G1 is fixed relative to the image plane IP during magnification variation (Step ST2). The first lens group G1 is configured to consist solely of convex lenses (Step ST3). Furthermore, the lenses are arranged within the lens barrel so as to satisfy at least the above-mentioned conditional expression (1) (Step ST4). This manufacturing method makes it possible to manufacture a variable magnification optical system ZL that is lightweight and compact, yet has high optical performance capable of correcting various aberrations such as field curvature and chromatic aberration.

[0065] Variable-magnification optical systems ZL according to examples of this embodiment will be described below with reference to the drawings. Figures 1, 3, 5, 7, and 9 are cross-sectional views showing the configurations of variable-magnification optical systems ZL {ZL(1) to ZL(5)} according to examples 1 to 5. In Figures 1, 3, 5, 7, and 9, the direction of movement of each lens group along the optical axis when focusing from infinity to a close-distance object is indicated by an arrow accompanied by the word (focusing).

[0066] 1, 3, 5, 7, and 9, 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, but each example represents a lens group, etc. independently. Therefore, even if the same symbols are used between examples, this does not mean that the examples have the same configuration.

[0067] Tables 1 to 5 are shown below, with Table 1 showing data on the various elements of the first embodiment, Table 1a showing a modified version of the first embodiment, Table 2 showing data on the various elements of the second embodiment, Table 3 showing data on the various elements of the third embodiment, Table 4 showing data on ...

[0068] In the table of [Overall Specifications], f denotes the focal length of the entire variable magnification optical system ZL, FNO denotes the F-number, ω denotes the half angle of view (unit: ° (degrees)), and Y denotes the image height. TL denotes the overall lens length of the variable magnification optical system ZL, and more specifically, the value obtained by adding the air-equivalent distance from the final lens surface on the optical axis to the image plane IP when focused at infinity to the distance from the lens surface closest to the object on the optical axis when focused at infinity. BF denotes the air-equivalent distance (back focus) from the final lens surface on the optical axis to the image plane IP when focused at infinity. Df denotes the outer radius of the final lens located closest to the image in the variable magnification optical system ZL. fAw denotes the composite focal length at the wide-angle end of the lens located closer to the object than the aperture stop SP in the variable magnification optical system ZL. fBw denotes the composite focal length at the wide-angle end of the lens located closer to the image than the aperture stop SP in the variable magnification optical system ZL. fAt denotes the composite focal length at the telephoto end of the lens located closer to the object than the aperture stop SP in the variable magnification optical system ZL. fBt denotes the composite focal length at the telephoto end of the lens located closer to the image than the aperture stop SP in the variable magnification optical system ZL. L23w denotes the distance on the optical axis from the lens surface of the second positive lens group closest to the image to the lens surface of the third positive lens group closest to the object at the wide-angle end. L23t denotes the distance on the optical axis from the lens surface of the second positive lens group closest to the image to the lens surface of the third positive lens group closest to the object at the telephoto end. Here, the second positive lens group refers to the lens group located closest to the object among the lens groups having positive refractive power that are located closer to the image than the first lens group G1. The third positive lens group refers to the lens group located closest to the object among the lens groups having positive refractive power that are located closer to the image than the second positive lens group. νp represents the Abbe number of the convex lens included in the lens group with positive refractive power in the rear group GR that moves toward the object side when zooming from the wide-angle end to the telephoto end. νn represents the Abbe number of the concave lens included in the lens group with positive refractive power in the rear group GR that moves toward the object side when zooming from the wide-angle end to the telephoto end. All of these values ​​are when the variable-magnification optical system ZL is focused at infinity.

[0069] In the "Lens Specifications" table, the surface number indicates the order of the optical surfaces from the object side along the direction of light ray travel, R is the radius of curvature of each optical surface (a surface whose center of curvature is located on the image plane side has a positive value), D is the surface spacing, which is the distance on the optical axis from each optical surface to the next optical surface (or image plane), nd is the refractive index of the optical element material referenced to the d-line, and vd is the Abbe number of the optical element material referenced to the d-line. The "∞" next to the radius of curvature indicates a plane or an aperture, and (aperture) indicates an aperture stop. The refractive index of air, nd = 1.00000, is omitted. If the optical surface is aspherical, an * is added to the surface number, and the paraxial radius of curvature is shown in the "radius of curvature R" column.

[0070] In the table of [Aspherical Data], the shape of the aspherical surface shown in [Lens Specifications] is expressed by the following formula (A). X(y) is the distance (sag) along the optical axis from the tangent plane at the vertex of the aspherical surface to the position on the aspherical surface at height y, R is the radius of curvature of the reference spherical surface (paraxial radius of curvature), κ is the conic constant, and Ai is the ith aspherical coefficient. "E-n" represents "×10-n." For example, 1.234E-05 = 1.234×10-5. Note that the second-order aspherical coefficient A2 is 0, and is therefore omitted.

[0071] X(y)=(y2 / R) / {1+(1-κ×y2 / R2)1 / 2}+A4×y4+A6×y6+A 8×y8+A10×y10+A12×y12 ... (A)

[0072] The "Variable Distance Data" table shows the surface spacings listed for the surface numbers in the "Lens Specifications" table that have a surface spacing of (variable), and shows the surface spacings when focused at infinity and when focused at close range. Note that β indicates the magnification. Furthermore, D0 indicates the distance from the object to the optical surface closest to the object in the optical system. Here, the surface spacings are shown for each magnification state at the wide-angle end (W), mid-focal length (M), and telephoto end (T) when focused at infinity and close range.

[0073] The table of [Lens Group Data] shows the first surface (the surface closest to the object) and focal length of each lens group.

[0074] In the following, for all specifications, the focal length, radius of curvature R, surface spacing D, and other lengths are generally expressed in "mm" unless otherwise specified, but this is not limited to this, as the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0075] The explanation of the tables up to this point is common to all the embodiments, and duplicate explanations will be omitted below.

[0076] First Example The first example will be described with reference to FIGS. 1, 2A, 2B, and Table 1. FIG. 1 shows the lens configuration of a variable magnification optical system ZL(1) according to the first example. The variable magnification optical system ZL(1) according to the first example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having negative refractive power, and an eighth lens group G8 having positive refractive power. The spacing between adjacent lens groups changes during magnification. When focusing from an object at infinity to a close object, the seventh lens group G7 moves toward the image side.

[0077] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a meniscus-shaped positive lens L11 with its convex surface facing the object side, and a meniscus-shaped positive lens L12 with its convex surface facing the object side.

[0078] The second lens group G2 is composed of, arranged in order from the object side along the optical axis, a negative meniscus lens L21 with its convex surface facing the object side, a negative meniscus lens L22 with its convex surface facing the object side, a positive meniscus lens L23 with its convex surface facing the object side, and a biconcave lens L24 with negative refractive power.

[0079] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconvex lens L31 having positive refractive power and a positive meniscus lens L32 with its convex surface facing the object side.

[0080] The fourth lens group G4 is composed of a biconcave lens L41 having negative refractive power, which is arranged in order from the object side along the optical axis.

[0081] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a biconvex lens L51 having positive refractive power, a biconvex lens L52 having positive refractive power, a biconcave lens L53 having negative refractive power, and a biconvex lens L54 having positive refractive power.

[0082] The sixth lens group G6 is composed of, arranged in order from the object side along the optical axis, a biconvex lens L61 having positive refractive power and a stop SP.

[0083] The seventh lens group G7 is composed of a biconcave lens L71 having negative refractive power, arranged in order from the object side along the optical axis.

[0084] The eighth lens group G8 is composed of, arranged in order from the object side along the optical axis, a meniscus-shaped positive lens L81 with its concave surface facing the object side, a biconcave lens L82 with negative refractive power, a biconvex lens L83 with positive refractive power, a biconvex lens L84 with positive refractive power, a meniscus-shaped positive lens L85 with its convex surface facing the object side, a meniscus-shaped negative lens L86 with its convex surface facing the object side, and a biconcave lens L87 with negative refractive power.

[0085] Table 1 below shows the values ​​of the specifications of the variable magnification optical system ZL(1) according to the first example.

[0086] (Table 1) [Overall specifications] Wide-angle end Intermediate telephoto end f 123.600 200.000 291.000 FNO 2.870 2.870 2.870 ω (°) 10.094 6.224 4.265 Y 21.700 21.700 21.700 TL 368.000 368.000 368.000 BF 30.000 30.000 30.000 Df=24.156 fAw=70.124 fBw=7510.843 fAt=165.098 fBt=7148.499 L23w=65.894 L23t=17.408 νp=95.100 νn=29.120 [Lens specifications] Surface number R D nd νd 1 249.0610 5.8780 1.59349 67.00 2 1116.7600 0.1000 3 121.8400 10.5952 1.43384 95.16 4 684.4240 Variable (D4) 5 326.8680 2.4000 1.80400 46.60 6 107.4350 1.7054 7 192.5990 2.4000 1.59319 67.90 8 60.0816 1.4311 9 61.3602 3.3666 1.89286 20.36 10 78.6609 8.0935 11 -104.4030 2.2000 1.83481 42.73 12 1293.4700 Variable (D12) 13 712.7520 5.3186 1.83481 42.73 14 -137.4720 0.1000 15 97.0499 5.5317 1.76684 46.78 16 751.9170 Variable (D16) 17 -240.2200 2.2000 1.48749 70.32 18 125.7060 Variable (D18) 19 105.4700 6.7114 1.49782 82.57 20 -153.5190 0.1000 21 69.0014 7.5541 1.43700 95.10 22 -143.6670 2.0000 2.00100 29.12 23 56.4879 0.1000 24 54.4846 6.4843 1.43700 95.10 25 -789.4580 Variable (D25) 26 83.7456 4.1940 1.90200 25.26 27 -5270.5600 4.5000 28 ∞ Variable (D28) (Aperture) 29 -702.4430 1.6775 1.71736 29.57 30 52.3964 Variable (D30) 31 -87.2369 3.1119 1.85478 24.80 32 -54.8673 0.1000 33 -69.3715 1.5000 1.83481 42.73 34 141.1600 2.0000 35 115.8150 4.7426 1.51680 64.13 36 -115.6310 44.2753 37 166.5400 8.0283 1.64000 60.19 38 -128.6460 15.2693 39 72.2323 6.6632 1.85478 24.80 40 360.9930 3.8736 41 55.4785 2.5000 1.59319 67.90 42 51.8229 12.0729 43 -196.0880 2.0000 1.66382 27.35 44 60.3729 30.0000 [Variable Interval Data] W M T W M T Infinite Infinite Infinite Short Short Short D0 ∞ ∞ ∞ 840.000 1240.000 1440.000 β - - - -0.132 -0.143 -0.180 D4 12.871 56.482 82.643 12.871 56.482 82.643 D12 37.828 19.625 1.500 37.828 19.625 1.500 D16 15.803 21.214 13.708 15.803 21.214 13.708 D18 47.892 13.063 1.500 47.892 13.063 1.50 D25 1.630 5.637 16.671 1.630 5.637 16.671 D28 4.199 4.273 4.199 9.840 14.323 23.199 D30 27.000 26.925 27.000 21.358 16.875 8.000 [Lens Group Data] Group Start Surface Focal Length G1 1 209.121 G2 5 -55.759 G3 13 70.798 G4 17 -168.948 G5 19 422.412 G6 26 91.426 G7 29 -67.908 G8 31 119.246.

[0087] FIG. 2A shows various aberration diagrams of the variable magnification optical system ZL(1) according to Example 1 at the wide-angle end when focusing at infinity. FIG. 2B shows various aberration diagrams of the variable magnification optical system ZL(1) according to Example 1 at the telephoto end when focusing at infinity. In each aberration diagram, FNO indicates the F-number, and Y indicates the image height. Also, in each aberration diagram, d indicates the aberration at the d-line (λ=587.6 nm), and g indicates the aberration at the g-line (λ=435.8 nm). Also, in the aberration diagrams showing the curvature of field, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. The distortion diagrams show distortion based on the d-line. Note that the same symbols as in this example are used in the aberration diagrams of each example shown below, and redundant explanations will be omitted.

[0088] From the various aberration diagrams, it can be seen that the variable magnification optical system ZL(1) according to the first example has excellent correction of various aberrations and has excellent imaging performance.

[0089] [Modification of First Example] A teleconverter lens TCL may be attached to the variable magnification optical system ZL(1) according to Example 1. In this case, the teleconverter lens TCL is disposed in the space between surfaces 36 and 37 of the variable magnification optical system ZL(1) according to Example 1.

[0090] Table 1a below lists the values ​​of the specifications of a variable magnification optical system ZL(1a) to which a teleconverter lens TCL according to a modification of the first embodiment is attached.

[0091] Furthermore, since the lens data for the variable magnification optical system ZL(1) according to the first example has already been shown in Table 1, the lens data in Table 1a shows values ​​for surfaces 36 and onward for the variable magnification optical system ZL(1a) in which a teleconverter lens TCL is attached in the space between surfaces 36 and 37 of the variable magnification optical system ZL(1).

[0092] (Table 1a) [Overall specifications] Wide-angle end Mid-telephoto end f 210.374 340.106 494.700 FNO 4.879 4.879 4.879 ω (°) 5.715 3.529 2.423 Y 21.700 21.700 21.700 TL 368.000 368.000 368.000 BF 30.000 30.000 30.000 [Lens specifications] Surface number R D nd νd 35 115.8150 4.7426 1.51680 64.13 36 -115.6310 2.0000 37 25.6976 6.5896 1.65412 39.68 38 191.5750 2.1135 39 109.3560 1.0000 2.00069 25.46 40 17.4015 6.8819 1.65412 39.68 41 -240.1120 0.1000 42 66.7830 1.0000 1.83481 42.73 43 20.8526 0.1215 44 21.0087 4.8111 1.64769 33.72 45 565.1140 1.0000 1.83481 42.73 46 28.6019 0.1000 47 26.2529 7.2294 1.69895 30.13 48 -19.7321 1.0000 1.83481 42.73 49 156.6450 1.1710 50 -79.9677 5.0646 1.65412 39.68 51 -16.6025 1.0000 1.59319 67.90 52 41.9602 3.0927 53 166.5400 8.0283 1.64000 60.19 54 -128.6460 15.2693 55 72.2323 6.6632 1.85478 24.80 56 360.9930 3.8736 57 55.4785 2.5000 1.59319 67.90 58 51.8229 12.0729 59 -196.0880 2.0000 1.66382 27.35 60 60.3729 30.0000.

[0093] Second Example The second example will be described with reference to FIGS. 3, 4A, 4B, and Table 2. FIG. 3 shows the lens configuration of a variable magnification optical system ZL(2) according to the second example. The variable magnification optical system ZL(2) according to the second example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, a seventh lens group G7 having positive refractive power, an eighth lens group G8 having negative refractive power, and a ninth lens group G9 having positive refractive power. The spacing between adjacent lens groups changes during magnification. When focusing from an object at infinity to an object at a close distance, the sixth lens group G6 moves toward the image side, and the eighth lens group G8 moves toward the image side.

[0094] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a biconvex lens L11 having positive refractive power and a positive meniscus lens L12 with its convex surface facing the object side.

[0095] The second lens group G2 is composed of a negative meniscus lens L21 with its convex surface facing the object side, arranged in order from the object side along the optical axis.

[0096] The third lens group G3 is composed of, arranged in order from the object side along the optical axis, a biconcave lens L31 having negative refractive power, a positive meniscus lens L32 with its convex surface facing the object side, and a biconcave lens L33 having negative refractive power.

[0097] The fourth lens group G4 is composed of a positive meniscus lens L41 with its convex surface facing the object side, which is arranged in order from the object side along the optical axis.

[0098] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a meniscus-shaped positive lens L51 with its convex surface facing the object side, a biconvex lens L52 with positive refractive power, a biconcave lens L53 with negative refractive power, a meniscus-shaped positive lens L54 with its convex surface facing the object side, and an aperture stop SP.

[0099] The sixth lens group G6 is composed of, arranged in order from the object side along the optical axis, a biconvex lens L61 having positive refractive power and a biconcave lens L62 having negative refractive power.

[0100] The seventh lens group G7 is composed of, arranged in order from the object side along the optical axis, a meniscus-shaped positive lens L71 with its concave surface facing the object side, and a biconvex lens L71 with positive refractive power.

[0101] The eighth lens group G8 is composed of a biconcave lens L81 having negative refractive power, arranged in order from the object side along the optical axis.

[0102] The ninth lens group G9 is composed of a positive meniscus lens L91 with its convex surface facing the object side, which is arranged in order from the object side along the optical axis.

[0103] Table 2 below shows the values ​​of the specifications of the variable magnification optical system ZL(2) according to the second example.

[0104] (Table 2) [Overall specifications] Wide-angle end Intermediate telephoto end f 103.000 200.000 291.000 FNO 2.880 2.880 2.880 ω (°) 11.758 6.089 4.186 Y 21.700 21.700 21.700 TL 350.000 350.000 350.000 BF 40.143 40.143 40.143 Df=21.842 fAw=123.825 fBw=303.471 fAt=324.482 fBt=251.282 L23w=34.1995 L23t=1.5000 νp=95.100 νn=23.800 [Lens specifications] Surface number R D nd νd 1 253.3460 8.5571 1.43700 95.10 2 -829.9830 18.1349 3 105.7040 9.1314 1.43700 95.10 4 296.6820 Variable (D4) 5 132.1390 ​​3.0000 1.48749 70.32 6 62.1941 Variable (D6) 7 -220.2510 2.6867 1.75500 52.34 8 102.9030 3.2842 1.90200 25.26 9 175.6020 6.4298 10 -145.1580 2.5835 1.49782 82.57 11 676.4150 Variable (D11) 12 123.0390 4.4303 1.75575 24.71 13 916.5290 Variable (D13) 14 51.5939 8.6660 1.43700 95.10 15 409.7960 18.1028 16 72.7769 6.7862 1.59282 68.62 17 -168.9610 2.2136 1.84666 23.80 18 68.6573 0.7270 19 65.8697 3.0000 1.59282 68.62 20* 125.7160 3.5153 21 ∞ Variable (D21) (Aperture) 22 289.9670 3.7823 1.50296 81.11 23 -130.0570 0.1000 24 -227.8420 1.9003 1.66131 32.75 25 97.5644 Variable (D25) 26 -1407.1700 2.4626 1.93139 23.86 27 -234.5340 0.1000 28 103.3090 4.3808 1.99869 30.02 29 -283.1820 Variable (D29) 30 -157.4620 1.8447 1.48749 70.32 31 40.3225 Variable (D31) 32 64.9730 2.8336 1.88000 41.00 33* 89.2023 40.1430 [Aspheric data] Surface 20 κ=0.0000, A4=2.06281576135564E-06, A6=3.7245630238531E-10 A8=1.74208218895097E-13, A10=7.02583944449562E-17 33rd side κ=0.0000, A4=-3.10484961678028E-07, A6=-2.61464836076392E-10 A8=1.21414793935461E-15, A10=-1.8582376550257E-17 [Variable interval data] W M T W M T Infinity Infinity Infinity Infinity Nearby Nearby Nearby D0 ∞ ∞ ∞ 405.000 855.000 1155.000 β - - - -0.173 -0.163 -0.179 D4 11.010 49.143 60.000 11.010 49.143 60.000 D6 33.287 34.548 37.683 33.287 34.548 37.683 D11 54.886 15.493 1.500 54.886 15.493 1.500 D13 34.200 18.649 1.500 34.200 18.649 1.500 D21 1.500 1.628 6.216 18.983 34.416 60.000 D25 29.240 44.663 57.225 11.759 11.875 3.440 D29 7.382 10.566 6.955 12.279 22.150 24.141 D31 19.699 16.514 20.125 14.803 4.931 2.939 [Lens group data] Initial focal length G1 1 207.070 G2 5 -244.458 G3 7 -86.352 G4 12 187.598 G5 14 140.952 G6 22 -248.311 G7 26 60.928 G8 30 -65.651 G9 32 257.7153.

[0105] 4A shows various aberration diagrams of the variable magnification optical system ZL(2) according to Example 2 when focused at infinity at the wide-angle end. 4B shows various aberration diagrams of the variable magnification optical system ZL(2) according to Example 2 when focused at infinity at the telephoto end. From these aberration diagrams, it can be seen that the variable magnification optical system ZL(2) according to Example 2 has excellent correction of various aberrations and has excellent imaging performance.

[0106] Third Example The third example will be described with reference to FIGS. 5, 6A, 6B, and Table 3. FIG. 5 shows the lens configuration of a variable magnification optical system ZL(3) according to the third example. The variable magnification optical system ZL(3) according to the third example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having positive refractive power, an eighth lens group G8 having negative refractive power, and a ninth lens group G9 having positive refractive power. The spacing between adjacent lens groups changes during magnification. When focusing from an object at infinity to a close object, the eighth lens group G8 moves toward the image side.

[0107] The first lens group G1 is composed of, arranged in order from the object side along the optical axis, a meniscus-shaped positive lens L11 with its convex surface facing the object side, and a biconvex lens L12 having positive refractive power.

[0108] The second lens group G2 is composed of a biconvex lens L21 having positive refractive power, which is arranged in order from the object side along the optical axis.

[0109] The third lens group G3 is composed of a biconcave lens L31 having negative refractive power, which is arranged in order from the object side along the optical axis.

[0110] The fourth lens group G4 is composed of a negative meniscus lens L41 with its concave surface facing the object side, arranged in order from the object side along the optical axis.

[0111] The fifth lens group G5 is composed of a biconvex lens L51 having positive refractive power, which is arranged in order from the object side along the optical axis.

[0112] The sixth lens group G6 is composed of, arranged in order from the object side along the optical axis, a biconvex lens L61 having positive refractive power, a biconvex lens L62 having positive refractive power, a biconcave lens L63 having negative refractive power, and a biconvex lens L64 having positive refractive power.

[0113] The seventh lens group G7 is composed of a biconvex lens L71 having positive refractive power, which is arranged in order from the object side along the optical axis.

[0114] The eighth lens group G8 is composed of a negative meniscus lens L81 with its convex surface facing the object side, arranged in order from the object side along the optical axis.

[0115] The ninth lens group G9 is composed of, arranged in order from the object side along the optical axis, an aperture stop SP, a meniscus-shaped positive lens L91 with its concave surface facing the object side, a biconcave lens L92 with negative refractive power, a meniscus-shaped positive lens L93 with its convex surface facing the object side, a biconvex lens L94 with positive refractive power, a meniscus-shaped positive lens L95 with its convex surface facing the object side, a meniscus-shaped negative lens L96 with its convex surface facing the object side, and a meniscus-shaped negative lens L97 with its concave surface facing the object side.

[0116] Table 3 below shows the values ​​of the specifications of the variable magnification optical system ZL(3) according to the third example.

[0117] (Table 3) [Overall specifications] Wide-angle end Intermediate telephoto end f 123.600 200.000 291.000 FNO 2.870 2.870 2.870 ω (°) 10.008 6.163 4.222 Y 21.700 21.700 21.700 TL 360.000 360.000 360.000 BF 38.377 38.377 38.377 Df=21.053 fAw=149.786 fBw=360.175 fAt=352.630 fBt=360.175 L23w=99.1531 L23t = 20.2495 νp = 94.660 νn = 24.800 [Lens specifications] Surface number R D nd νd 1 282.3790 4.5435 1.48749 70.32 2 686.3840 0.1000 3 142.5810 11.3803 1.43384 95.16 4 -2767.5900 Variable (D4) 5 579.5820 3.2934 1.85478 24.80 6 -1482.9300 Variable (D6) 7 -246.5720 2.2000 1.48749 70.32 8 71.1095 Variable (D8) 9 -100.6560 2.0000 1.84850 43.79 10 -1949.2700 Variable (D10) 11 201.6380 3.9348 1.89286 20.36 12 -24840.9000 Variable (D12) 13 241.6200 6.0430 1.59349 67.00 14 -181.9070 0.1000 15 129.8020 9.0994 1.43875 94.66 16 -109.6080 2.2000 1.85478 24.80 17 152.3500 0.1000 18 109.5280 7.0310 1.59522 67.73 19 -331.3230 Variable (D19) 20* 117.2540 5.7337 1.83481 42.73 21 -357.2150 Variable (D21) 22 4150.8100 1.7000 1.54072 47.23 23 54.5915 Variable (D23) 24 ∞ 7.0904 (Aperture) 25 -135.8000 3.0000 1.92286 18.90 26 -75.3043 0.1000 27 -90.7141 1.2000 1.84850 43.79 28 130.4900 8.6096 29 90.5356 3.2381 1.49782 82.57 30 618.4550 40.0000 31 115.2480 7.1376 1.48749 70.32 32 -98.8619 0.1000 33 43.0161 4.9398 1.80000 29.84 34 72.0464 0.1108 35 53.6207 2.0000 1.51680 64.13 36 32.7430 24.5597 37 -63.8653 1.2000 1.92286 18.90 38 -156.7730 38.3767 [Aspheric data] 20th surface κ=0.0000, A4=-3.31357842436924E-07, A6=-3.48715750266762E-11 A8=-2.88853078968892E-14, A10=2.40633347217063E-17 [Variable interval data] W M T W M T Infinity Infinity Infinity Near near Near near near D0 ∞ ∞ ∞ 840.000 1240.000 1440.000 β - - - -0.126 -0.140 -0.179 D4 1.500 51.479 89.315 1.500 51.479 89.315 D6 23.700 16.563 2.911 23.700 16.563 2.911 D8 30.001 9.801 11.639 30.001 9.801 11.639 D10 41.253 22.928 1.500 41.253 22.928 1.500 D12 30.425 15.860 1.500 30.425 15.860 1.500 D19 1.500 11.749 21.513 1.500 11.749 21.513 D21 2.622 1.645 3.500 7.093 9.781 19.501 D23 27.878 28.855 27.000 23.407 20.719 11.000 [Lens group data] Initial focal length G1 1 238.257 G2 5 487.871 G3 7 -112.961 G4 9 -125.150 G5 11 224.032 G6 13 143.829 G7 20 106.330 G8 22 -102.321 G9 24 360.1788

[0118] 6A shows various aberration diagrams of the variable magnification optical system ZL(3) according to Example 3 when focused at infinity at the wide-angle end. 6B shows various aberration diagrams of the variable magnification optical system ZL(3) according to Example 3 when focused at infinity at the telephoto end. From these aberration diagrams, it can be seen that the variable magnification optical system ZL(3) according to Example 3 has excellent correction of various aberrations and has excellent imaging performance.

[0119] Fourth Example The fourth example will be described with reference to FIGS. 7, 8A, 8B, and Table 4. FIG. 7 shows the lens configuration of a variable magnification optical system ZL(4) according to the fourth example. The variable magnification optical system ZL(4) according to the fourth example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having negative refractive power, and an eighth lens group G8 having positive refractive power. The spacing between adjacent lens groups changes during magnification. When focusing from an object at infinity to a close object, the seventh lens group G7 moves toward the image side.

[0120] The first lens group G1 is composed of a positive meniscus lens L11 with its convex surface facing the object side, arranged in order from the object side along the optical axis.

[0121] The second lens group G2 is composed of a positive meniscus lens L21 with its convex surface facing the object side, which are arranged in order from the object side along the optical axis.

[0122] The third lens group G3 is composed of a negative meniscus lens L31 with its convex surface facing the object side, arranged in order from the object side along the optical axis.

[0123] The fourth lens group G4 is composed of a negative meniscus lens L41 with its concave surface facing the object side, arranged in order from the object side along the optical axis.

[0124] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a biconvex lens L51 having positive refractive power, a biconvex lens L52 having positive refractive power, and a biconcave lens L53 having negative refractive power.

[0125] The sixth lens group G6 is composed of a biconvex lens L61 having positive refractive power, which is arranged in order from the object side along the optical axis.

[0126] The seventh lens group G7 is composed of a negative meniscus lens L71 with its convex surface facing the object side, arranged in order from the object side along the optical axis.

[0127] The eighth lens group G8 is composed of, arranged in order from the object side along the optical axis, an aperture stop SP, a meniscus-shaped positive lens L81 with its concave surface facing the object side, a biconcave lens L82 with negative refractive power, a biconvex lens L83 with positive refractive power, a biconcave lens L84 with negative refractive power, a biconvex lens L85 with positive refractive power, a biconvex lens L86 with positive refractive power, and a biconcave lens L87 with negative refractive power.

[0128] Table 4 below shows the values ​​of the specifications of the variable magnification optical system ZL(4) according to the fourth example.

[0129] (Table 4) [Overall specifications] Wide-angle end Intermediate telephoto end f 154.500 200.000 291.000 FNO 2.870 2.870 2.870 ω (°) 8.020 6.179 4.224 Y 21.700 21.700 21.700 TL 360.000 360.000 360.000 BF 30.000 30.000 30.000 Df=21.489 fAw=249.308 fBw=228.894 fAt=469.431 fBt=228.894 L23w=107.316 L23t=30.0557 νp=94.940 νn=29.740 [Lens specifications] Surface number R D nd νd 1 140.1322 12.0000 1.48749 70.32 2 4956.1383 Variable (D2) 3 125.0601 5.9503 1.66382 27.35 4 759.0614 Variable (D4) 5 74897.5299 2.2000 1.64000 60.19 6 70.1538 Variable (D6) 7 -84.8132 2.0000 1.95375 32.33 8 -339.8428 Variable (D8) 9 169.1795 8.6778 1.59522 67.73 10 -106.8163 0.1000 11 80.2562 11.7028 1.43875 94.94 12 -99.2203 2.0339 1.77047 29.74 13 3368.5995 Variable (D13) 14 140.1750 5.0786 1.83481 42.73 15 -327.4635 Variable (D15) 16* 4929.1495 1.5628 1.64804 36.55 17 56.0609 Variable (D17) 18 ∞ 7.9052 (twist) 19 -80.4629 3.0000 1.95906 17.47 20 -64.7690 4.8440 21 -89.1264 1.2000 1.77250 49.62 22 151.9523 3.0508 23 93.2418 3.8086 1.83481 42.73 24 -651.4437 36.0000 25 -344.0434 1.4000 1.84666 23.80 26 99.1271 7.3733 27 285.7174 5.3585 1.64000 60.19 28 -102.0911 0.1000 29 79.9376 6.0691 1.85478 24.80 30 -569.1037 29.0024 31 -227.4094 2.9659 1.93740 29.58 32 145.1622 30.0000 [Aspheric surface] 16th surface κ=0.0000, A4=3.84202281630537E-07, A6=-5.72544851913181E-11 A8=6.65595827171945E-15, A10=-2.19483390587923E-18 [Changeable Interval Data] WMT WMT Infinite Infinite Infinite Infinite Infinite Near Distance Near Distance Near Distance D0 ∞ ∞ ∞ 840.000 1240.000 1440.000 β - - - -0.150 -0.140 -0.183 D2 31.500 55.098 84.197 31.500 55.098 84.197 D4 15.523 16.222 12.305 15.523 16.222 12.305 D6 39.025 20.884 12.050 39.025 20.884 12.050 D8 48.568 33.152 1.500 48.568 33.152 1.500 D13 1.500 10.762 26.063 1.500 10.762 26.063 D15 3.631 1.858 3.500 10.296 9.857 19.500 D17 26.868 28.642 27.000 20.203 20.643 11.000 [Lens group data] Initial focal length G1 1 295.579 G2 3 224.715 G3 5 -109.719 G4 7 -118.955 G5 9 88.805 G6 14 118.164 G7 16 -87.515 G8 18 228.896.

[0130] Fig. 8A shows various aberration diagrams of the variable magnification optical system ZL(4) according to Example 4 when focused at infinity at the wide-angle end. Fig. 8B shows various aberration diagrams of the variable magnification optical system ZL(4) according to Example 4 when focused at infinity at the telephoto end. From these aberration diagrams, it can be seen that the variable magnification optical system ZL(4) according to Example 4 has excellent correction of various aberrations and has excellent imaging performance.

[0131] Fifth Example The fifth example will be described with reference to FIGS. 9, 10A, 10B, and Table 5. FIG. 9 shows the lens configuration of a variable magnification optical system ZL(5) according to the fifth example. The variable magnification optical system ZL(5) according to the fifth example is composed of, arranged in order from the object side along the optical axis, a first lens group G1 having positive refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having negative refractive power, and an eighth lens group G8 having positive refractive power. The spacing between adjacent lens groups changes during magnification. When focusing from an object at infinity to a close object, the seventh lens group G7 moves toward the image side.

[0132] The first lens group G1 is composed of a positive meniscus lens L11 with its convex surface facing the object side, arranged in order from the object side along the optical axis.

[0133] The second lens group G2 is composed of a positive meniscus lens L21 with its convex surface facing the object side, which are arranged in order from the object side along the optical axis.

[0134] The third lens group G3 is composed of a negative meniscus lens L31 with its convex surface facing the object side, arranged in order from the object side along the optical axis.

[0135] The fourth lens group G4 is composed of a negative meniscus lens L41 with its concave surface facing the object side, arranged in order from the object side along the optical axis.

[0136] The fifth lens group G5 is composed of, arranged in order from the object side along the optical axis, a biconvex lens L51 having positive refractive power, a biconvex lens L52 having positive refractive power, and a biconcave lens L53 having negative refractive power.

[0137] The sixth lens group G6 is composed of a biconvex lens L61 having positive refractive power, which is arranged in order from the object side along the optical axis.

[0138] The seventh lens group G7 is composed of a negative meniscus lens L71 with its convex surface facing the object side, arranged in order from the object side along the optical axis.

[0139] The eighth lens group G8 is composed of, arranged in order from the object side along the optical axis, an aperture stop SP, a meniscus-shaped positive lens L81 with its concave surface facing the object side, a biconcave lens L82 with negative refractive power, a biconvex lens L83 with positive refractive power, a biconcave lens L84 with negative refractive power, a meniscus-shaped positive lens L85 with its concave surface facing the object side, a biconvex lens L86 with positive refractive power, a meniscus-shaped positive lens L87 with its concave surface facing the object side, and a biconcave lens L88 with negative refractive power.

[0140] Table 5 below shows the values ​​of the specifications of the variable magnification optical system ZL(5) according to the fifth example.

[0141] (Table 5) [Overall specifications] Wide-angle end Intermediate telephoto end f 185.400 300.000 391.000 FNO 2.870 2.870 2.870 ω (°) 6.678 4.109 3.145 Y 21.700 21.700 21.700 TL 450.000 450.000 450.001 BF 30.000 30.000 30.000 Df=21.316 fAw=261.256 fBw=274.945 fAt=550.902 fBt=274.945 L23w=170.0276 L23t = 47.1018 νp = 94.940 νn = 29.740 [Lens specifications] Surface number R D nd νd 1 204.6679 13.3853 1.48749 70.32 2 18211.2138 Variable (D2) 3 148.4778 7.0077 1.66382 27.35 4 478.4457 Variable (D4) 5 398.4901 3.0000 1.64000 60.19 6 81.4950 Variable (D6) 7 -109.7518 2.4500 1.77047 29.74 8 -353.9500 Variable (D8) 9 146.3170 11.1261 1.43875 94.94 10 -149.4157 0.1000 11 85.2772 13.7666 1.43875 94.94 12 -147.5838 3.0000 1.77047 29.74 13 536.3131 Variable (D13) 14 118.5756 7.0839 1.83481 42.73 15 -441.8258 Variable (D15) 16* 471.5777 3.0000 1.98105 28.17 17 64.0813 Can be changed (D17) 18 ∞ 7.6877 (twisted) 19 -89.5998 2.3317 1.95906 17.47 20 -70.4698 0.1000 21 -117.5877 1.2000 1.77250 49.62 22 115.2030 12.0311 23 127.5287 4.0102 1.81153 25.50 24 -190.1073 36.0000 25 -50.0634 3.0000 1.92000 23.00 26 294.0818 1.2290 27 -10945.1730 5.6813 1.91487 28.97 28 -67.5875 0.1000 29 142.2212 7.3535 1.70810 31.11 30 -85.2225 16.0817 31 -162.6546 2.9289 1.49800 83.00 32 -94.1301 15.2515 33 -86.6112 1.3741 1.88000 41.00 34 941.8921 30.0000 [Astrospherical Data] 16th face κ=0.0000, A4=3.19858362981165E-07, A6=-4.73483919984472E-11 A8=-2.80770071881799E-15, A10=4.69607566841943E-18 [Changeable Interval Data] WMT WMT Infinite Infinite Infinite Infinite Near Distance Near Distance Near Distance D0 ∞ ∞ ∞ 1200.000 1600.000 1800.000 β - - - -0.123 -0.154 -0.183 D2 42.564 105.032 125.000 42.564 105.032 125.000 D4 25.694 26.574 24.968 25.694 26.574 24.968 D6 43.883 14.879 15.184 43.883 14.879 15.184 D8 95.000 39.729 1.500 95.000 39.729 1.500 D13 1.500 22.427 41.991 1.500 22.427 41.991 D15 13.197 8.042 4.078 18.418 18.451 20.079 D17 17.881 23.036 27.000 12.658 12.626 11.000 [Lens Group Data] Initial Focal Length G1 1 424.509 G2 3 321.594 G3 5 -160.666 G4 7 -207.375 G5 9 129.894 G6 14 112.633 G7 16 -75.867 G8 18 274.940.

[0142] Fig. 10A shows various aberration diagrams of the variable magnification optical system ZL(5) of Example 5 when focused at infinity at the wide-angle end. Fig. 10B shows various aberration diagrams of the variable magnification optical system ZL(5) of Example 5 when focused at infinity at the telephoto end. From these aberration diagrams, it can be seen that the variable magnification optical system ZL(5) of Example 5 has excellent correction of various aberrations and has excellent imaging performance.

[0143] Next, the table of [Values ​​Corresponding to Conditional Expressions] is shown below, which summarizes the values ​​corresponding to each of the conditional expressions (1) to (10) for all the examples (Examples 1 to 5). Conditional expression (1): 0.01<Df / TLt<0.20 Conditional expression (2): 0.30<f1 / ft<1.50 Conditional expression (3): nd1min<1.70 Conditional expression (4): 63.00<νd1min Conditional expression (5): 0.80<ft / fw<4.00 Conditional expression (6): 0.05<BFt / ft<0.20 Conditional expression (7): 0.70<ft / TLt<1.00 Conditional expression (8): 0.50<fAw / fw<2.00 Conditional expression (9): 0.03<L23t / L23w<0.30 Conditional expression (10): 0.20<νp / νn<0.40

[0144] [Conditional Expression Corresponding Values] (Examples 1 to 3) Conditional Expression Example 1 Example 2 Example 3 (1) 0.0656 0.0624 0.0585 (2) 0.7186 0.7116 0.8188 (3) 1.4338 1.4370 1.4338 (4) 95.16 95.10 95.16 (5) 2.3544 2.8252 2.3544 (6) 0.1031 0.1379 0.1319 (7) 0.7908 0.8314 0.8083 (8) 0.567 1.202 1.212 (9) 0.2641 0.0439 0.2042 (10) 0.3062 0.2503 0.2620

[0145] [Conditional Expression Corresponding Values] (Examples 4 to 5) Conditional Expression Example 4 Example 5 (1) 0.0597 0.0474 (2) 1.0157 1.0857 (3) 1.4875 1.4875 (4) 70.32 70.32 (5) 1.8835 2.1090 (6) 0.1031 0.0767 (7) 0.8083 0.8689 (8) 1.614 1.409 (9) 0.2801 0.2770 (10) 0.3133 0.3133

[0146] As described above, according to each embodiment, it is possible to realize a variable magnification optical system ZL that is lightweight and compact yet has high optical performance capable of correcting various aberrations such as field curvature and chromatic aberration, and an optical apparatus having the same.

[0147] In the above-described embodiment, the following contents can be appropriately adopted within the scope that does not impair the optical performance.

[0148] Although an eight-group or nine-group configuration has been shown as an example of the variable magnification optical system ZL of this embodiment, the present application is not limited to this, and a variable magnification optical system with more groups (for example, ten groups, eleven groups, etc.) can also be configured. Specifically, a configuration in which a lens or lens group is added to the most object-side or most image-side of the variable magnification optical system ZL of this embodiment can also be used. Furthermore, a configuration in which another focusing lens group is added in addition to one or two focusing lens groups can also be used. Here, a lens group refers to a portion having at least one lens separated by an air gap that changes during magnification.

[0149] The lens surface may be spherical, flat, or aspherical. Spherical or flat lens surfaces are preferred because they facilitate lens processing and assembly adjustment, and prevent degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, they are preferred because they minimize degradation of imaging performance even when the image plane is misaligned.

[0150] When the lens surface is aspherical, the aspherical surface may be any of a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, and a hybrid aspherical surface in which a resin is formed into an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, or the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0151] The aperture diaphragm may not be provided as a component, and the lens frame may play the role of the aperture diaphragm.

[0152] Each lens surface may be coated with an anti-reflection coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high-contrast optical performance.

[0153] ZL Variable magnification optical system GR Rear group G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group G6 Sixth lens group G7 Seventh lens group G8 Eighth lens group G9 Ninth lens group SP Aperture stop IP Image plane

Claims

1. A variable magnification optical system having, arranged in order from the object side, a first lens group having positive refractive power and a rear group having multiple lens groups, wherein the spacing between adjacent lens groups changes during magnification variation, the first lens group is fixed relative to the image plane, and the first lens group is made up of one or multiple convex lenses, and which satisfies the following condition: 0.01 < Df / TLt < 0.20, where Df is the outer radius of the final lens arranged closest to the image side in the variable magnification optical system, and TLt is the total lens length of the variable magnification optical system at the telephoto end.

2. The variable magnification optical system according to claim 1, wherein the first lens group consists of one or two single lenses.

3. The variable magnification optical system according to claim 1 or 2, which satisfies the following condition: 0.30<f1 / ft<1.50, where f1 is the focal length of the first lens group, and ft is the focal length of the variable magnification optical system at the telephoto end.

4. A variable magnification optical system according to any one of claims 1 to 3, wherein the lens in the first lens group having the smallest dispersion satisfies the following conditional expressions: nd1min<1.70 63.00<νd1min (<100.00) where, nd1min: refractive index for the d-line of the lens in the first lens group having the smallest dispersion νd1min: Abbe number for the d-line of the lens in the first lens group having the smallest dispersion 5. A variable magnification optical system according to any one of claims 1 to 4, wherein the lens group arranged closest to the image side is fixed relative to the image plane during magnification variation.

6. A variable magnification optical system according to any one of claims 1 to 5, wherein the rear group comprises: a fixed lens group with positive refractive power that is fixed relative to the image plane during magnification variation; and a diaphragm arranged closer to the image plane than the fixed lens group.

7. A variable magnification optical system according to any one of claims 1 to 6, wherein the rear group includes a second lens group and a third lens group arranged in that order from the object side, and the second lens group and the third lens group move toward the image side during magnification variation.

8. A variable magnification optical system according to any one of claims 1 to 7, wherein the rear group has a plurality of lens groups, each consisting of a single lens, and a diaphragm arranged on the image side of the plurality of lens groups.

9. A variable magnification optical system according to any one of claims 1 to 8, which satisfies the following condition: 0.80<ft / fw<4.00, where ft is the focal length of the variable magnification optical system at the telephoto end, and fw is the focal length of the variable magnification optical system at the wide-angle end.

10. A variable magnification optical system according to any one of claims 1 to 9, which satisfies the following condition: 0.05<BFt / ft<0.20, where BFt is the back focus of the variable magnification optical system at the telephoto end, and ft is the focal length of the variable magnification optical system at the telephoto end.

11. A variable magnification optical system according to any one of claims 1 to 10, which satisfies the following condition: 0.70<ft / TLt<1.00, where ft is the focal length of the variable magnification optical system at the telephoto end.

12. A variable magnification optical system according to any one of claims 1 to 11, wherein the rear group has an aperture stop, and the variable magnification optical system has five or more lens groups arranged closer to the object side than the aperture stop.

13. A variable magnification optical system according to any one of claims 1 to 12, wherein the rear group has a stop and satisfies the following condition: 0.50<fAw / fw<2.00, where fAw is the combined focal length at the wide-angle end of the lens located closer to the object than the stop in the variable magnification optical system, and fw is the focal length of the variable magnification optical system at the wide-angle end.

14. A variable magnification optical system according to any one of claims 1 to 13, comprising a second positive lens group arranged closest to the object among lens groups having positive refractive power arranged closer to the image than the first lens group, and a third positive lens group arranged closest to the object among lens groups having positive refractive power arranged closer to the image than the second positive lens group, and satisfying the following conditional formula: 0.03<L23t / L23w<0.30 where L23w is the distance on the optical axis at the wide-angle end from the lens surface of the second positive lens group closest to the image to the lens surface of the third positive lens group closest to the object, and L23t is the distance on the optical axis at the telephoto end from the lens surface of the second positive lens group closest to the image to the lens surface of the third positive lens group closest to the object.

15. A variable magnification optical system according to any one of claims 1 to 14, wherein the rear group has a lens group having positive refractive power that moves toward the object side when zooming from the wide-angle end to the telephoto end, the lens group including a convex lens and a concave lens, and the following conditional expression is satisfied: 0.20<νp / νn<0.40, where νp is the Abbe number of the convex lens included in the lens group, and νn is the Abbe number of the concave lens included in the lens group.

16. A variable magnification optical system according to any one of claims 1 to 15, wherein the rear group is made up of seven or more lens groups.

17. An optical instrument comprising a variable magnification optical system according to any one of claims 1 to 16.

18. A method for manufacturing a variable magnification optical system having, arranged in order from the object side, a first lens group having positive refractive power and a rear group having multiple lens groups, wherein the spacing between adjacent lens groups changes during magnification variation and the first lens group is fixed relative to the image plane, the method comprising the steps of: configuring the first lens group to consist of one or multiple convex lenses; and arranging the lenses in a lens barrel so as to satisfy the following condition: 0.01<Df / TLt<0.20, where D: outer radius of the final lens arranged closest to the image in the variable magnification optical system, TLt: total lens length of the variable magnification optical system at the telephoto end.

Images