Variable magnification imaging optical system

Abstract

This invention provides a variable-magnification imaging optical system that achieves miniaturization and weight reduction while suppressing chromatic aberration during magnification and axial chromatic aberration, enabling faster focusing, and providing excellent optical performance from infinity to close range across the entire zoom range. [Solution] The variable magnification imaging optical system according to the present invention comprises, in order from the object side, 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, an intermediate group GM consisting of one or more lens groups including an aperture diaphragm S, a focusing group GF, and a subsequent group GR consisting of one lens group. The spacing between adjacent lens groups changes during magnification, and the focusing group GF moves along the optical axis when focusing from an object at infinity to an object at close range.

Description

Technical Field

[0001] The present invention relates to a zoom imaging optical system suitable for an imaging optical system used in imaging devices such as digital cameras and video cameras.

Background Art

[0002] In recent years, with the progress of mirrorless digital cameras and video cameras, high-performance cameras have been installed in smartphones and mobile data terminals. In order to differentiate digital cameras and video cameras from these mobile devices, the demand for ultra-telephoto zoom lenses is increasing.

[0003] In addition, in recent years, digital cameras and video cameras have further advanced in the high pixel count of imaging elements, and the demand for higher performance in imaging optical systems has been increasing.

[0004] Patent Documents 1 to 3 describe examples of zoom imaging optical systems with a half angle of view at the telephoto end of approximately 3 degrees or less.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] In an ultra-telephoto zoom lens with a narrow angle of view at the telephoto end, in order to improve the usability as a zoom lens, it is necessary to achieve three points: making the zoom ratio as large as possible, miniaturizing for improved portability, and imaging performance.

[0007] To achieve a large magnification ratio, it is common practice to place the lens group with the most positive refractive power closest to the object and extend it toward the object through magnification, thereby maximizing the telephoto ratio (the optical length divided by the focal length) at the telephoto end and improving image formation performance at telephoto focal lengths.

[0008] In telephoto lenses, aberrations generated in the converging lens group located near the object are amplified by the rear lens group. With a prime lens, image performance can be improved simply by suppressing the aberrations generated in the object-side converging system based on this relationship. However, with zoom lenses, various aberrations fluctuate due to changes in power distribution caused by the magnification, making it impossible to simplify the process as with prime lenses. In particular, chromatic aberration, which is a problem in lenses in the super-telephoto range with a narrow field of view, changes direction as the magnification changes. Therefore, in order to reduce the size of the optical system while suppressing chromatic aberration across the entire zoom range, it is important to select optical materials that correspond to the changes in power distribution caused by the magnification.

[0009] The optical system described in Patent Document 1 is an example of a fixed-length super-telephoto zoom lens. While aberrations are suppressed throughout the entire zoom range and imaging performance is high, attempting to increase the magnification ratio while maintaining imaging performance in such a fixed-length type results in a significantly enlarged optical system, which is undesirable.

[0010] The optical system described in Patent Document 2 is an example of a super-telephoto zoom lens with a variable overall length in which the first lens group extends. However, the back focus (distance from the final lens to the image plane) is large relative to the total optical length, and considering the shortened flange back due to the recent shift to mirrorless cameras, it is insufficient in terms of miniaturizing the optical system. Furthermore, the chromatic aberration of magnification varies greatly from the wide-angle end to the telephoto end, and the correction is insufficient.

[0011] The optical system described in Patent Document 3 is an example of a super-telephoto zoom lens that supports a short flange back, but the chromatic aberration of magnification varies greatly from the wide-angle end to the telephoto end, the correction is insufficient, and the suppression of the overall optical length at the wide-angle end is also insufficient.

[0012] This invention has been made in view of these problems, and aims to provide a variable-magnification imaging optical system that achieves miniaturization and weight reduction while suppressing magnification chromatic aberration and axial chromatic aberration during magnification, enabling faster focusing, and providing good optical performance from infinity to close range throughout the entire zoom range. [Means for solving the problem]

[0013] To solve the above problems, one embodiment of the variable magnification imaging optical system according to the present invention comprises, in order from the object side, 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, an intermediate group GM consisting of one or more lens groups including an aperture diaphragm S, a focusing group GF, and a subsequent group GR consisting of one lens group, wherein the spacing between adjacent lens groups changes during magnification, and the focusing group GF moves along the optical axis when focusing from an object at infinity to an object at close range. [Effects of the Invention]

[0014] According to at least some embodiments of the present invention, a variable-magnification imaging optical system can be provided that achieves miniaturization and weight reduction while suppressing magnification chromatic aberration and axial chromatic aberration during magnification, enabling faster focusing, and providing good optical performance from infinity to close range across the entire zoom range. [Brief explanation of the drawing]

[0015] [Figure 1] This is a lens configuration diagram of Embodiment 1 of the variable magnification imaging optical system of the present invention when the wide-angle end is focused at infinity. [Figure 2] This is a longitudinal aberration diagram at the wide-angle end when the variable magnification imaging optical system of the present invention is in focus at infinity, according to Embodiment 1. [Figure 3] This is a longitudinal aberration diagram of the intermediate focal length at infinity focus according to Embodiment 1 of the variable magnification imaging optical system of the present invention. [Figure 4] This is a longitudinal aberration diagram at infinity focus at the telephoto end according to Embodiment 1 of the variable magnification imaging optical system of the present invention. [Figure 5]It is a lateral aberration diagram at infinity focus at the wide-angle end according to Example 1 of the zoom imaging optical system of the present invention. [Figure 6] It is a lateral aberration diagram at infinity focus at the intermediate focal length according to Example 1 of the zoom imaging optical system of the present invention. [Figure 7] It is a lateral aberration diagram at infinity focus at the telephoto end according to Example 1 of the zoom imaging optical system of the present invention. [Figure 8] It is a lateral aberration diagram at focus when the object distance is 2.5 m at the wide-angle end according to Example 1 of the zoom imaging optical system of the present invention. [Figure 9] It is a lateral aberration diagram at focus when the object distance is 2.5 m at the intermediate focal length according to Example 1 of the zoom imaging optical system of the present invention. [Figure 10] It is a lateral aberration diagram at focus when the object distance is 2.5 m at the telephoto end according to Example 1 of the zoom imaging optical system of the present invention. [Figure 11] It is a lens configuration diagram at infinity focus at the wide-angle end according to Example 2 of the zoom imaging optical system of the present invention. [Figure 12] It is a longitudinal aberration diagram at infinity focus at the wide-angle end according to Example 2 of the zoom imaging optical system of the present invention. [Figure 13] It is a longitudinal aberration diagram at infinity focus at the intermediate focal length according to Example 2 of the zoom imaging optical system of the present invention. [Figure 14] It is a longitudinal aberration diagram at infinity focus at the telephoto end according to Example 2 of the zoom imaging optical system of the present invention. [Figure 15] It is a lateral aberration diagram at infinity focus at the wide-angle end according to Example 2 of the zoom imaging optical system of the present invention. [Figure 16] It is a lateral aberration diagram at infinity focus at the intermediate focal length according to Example 2 of the zoom imaging optical system of the present invention. [Figure 17] It is a lateral aberration diagram at infinity focus at the telephoto end according to Example 2 of the zoom imaging optical system of the present invention. [Figure 18] It is a lateral aberration diagram at focus when the object distance is 2.5 m at the wide-angle end according to Example 2 of the zoom imaging optical system of the present invention. [Figure 19] It is a lateral aberration diagram at focus when the object distance is 2.5 m at the intermediate focal length according to Example 2 of the zoom imaging optical system of the present invention. [Figure 20]This is a lateral aberration diagram of Embodiment 2 of the variable magnification imaging optical system of the present invention when the object distance at the telephoto end is 2.5m and in focus. [Figure 21] This is a lens configuration diagram for the wide-angle end at infinity focus according to Embodiment 3 of the variable magnification imaging optical system of the present invention. [Figure 22] This is a longitudinal aberration diagram at the wide-angle end when infinity focus is achieved, according to Embodiment 3 of the variable magnification imaging optical system of the present invention. [Figure 23] This is a longitudinal aberration diagram at infinity focus according to Embodiment 3 of the variable magnification imaging optical system of the present invention. [Figure 24] This is a longitudinal aberration diagram at infinity focus at the telephoto end according to Embodiment 3 of the variable magnification imaging optical system of the present invention. [Figure 25] This is a diagram of the lateral aberration at the wide-angle end when the variable magnification imaging optical system of the present invention is in focus at infinity, according to Embodiment 3 of the present invention. [Figure 26] This is a diagram of the transverse aberration at infinity focus according to Embodiment 3 of the variable magnification imaging optical system of the present invention. [Figure 27] This is a diagram of the transverse aberration at infinity focus at the telephoto end according to Embodiment 3 of the variable magnification imaging optical system of the present invention. [Figure 28] This is a lateral aberration diagram of the wide-angle end at an object distance of 2.5m, according to Embodiment 3 of the variable magnification imaging optical system of the present invention. [Figure 29] This is a lateral aberration diagram for Embodiment 3 of the variable magnification imaging optical system of the present invention, when the object distance is 2.5m and the intermediate focal length is in focus. [Figure 30] This is a lateral aberration diagram of Embodiment 3 of the variable magnification imaging optical system of the present invention when the object distance at the telephoto end is 2.5m and in focus. [Figure 31] This is a lens configuration diagram for Embodiment 4 of the variable magnification imaging optical system of the present invention, when the wide-angle end is focused at infinity. [Figure 32] This is a longitudinal aberration diagram at the wide-angle end when the variable magnification imaging optical system of the present invention is in focus at infinity, according to Embodiment 4. [Figure 33] This is a longitudinal aberration diagram of the intermediate focal length at infinity focus according to Embodiment 4 of the variable magnification imaging optical system of the present invention. [Figure 34] This is a longitudinal aberration diagram at infinity focus at the telephoto end according to Embodiment 4 of the variable magnification imaging optical system of the present invention. [Figure 35]This is a diagram of the lateral aberration at the wide-angle end when the variable magnification imaging optical system of the present invention is in focus at infinity, according to Embodiment 4. [Figure 36] This is a diagram of the transverse aberration at infinity focus according to Embodiment 4 of the variable magnification imaging optical system of the present invention. [Figure 37] This is a diagram of the transverse aberration at infinity focus at the telephoto end according to Embodiment 4 of the variable magnification imaging optical system of the present invention. [Figure 38] This is a lateral aberration diagram of Embodiment 4 of the variable magnification imaging optical system of the present invention when the object distance is 1.7m at the wide-angle end and in focus. [Figure 39] This is a lateral aberration diagram for Embodiment 4 of the variable magnification imaging optical system of the present invention, when the object distance is 1.7m and the intermediate focal length is in focus. [Figure 40] This is a lateral aberration diagram of Embodiment 4 of the variable magnification imaging optical system of the present invention when the object distance at the telephoto end is 1.7m and in focus. [Figure 41] This is a lens configuration diagram for the wide-angle end at infinity focus according to Embodiment 5 of the variable magnification imaging optical system of the present invention. [Figure 42] This is a longitudinal aberration diagram at the wide-angle end when the variable magnification imaging optical system of the present invention is in focus at infinity, according to Embodiment 5. [Figure 43] This is a longitudinal aberration diagram of the intermediate focal length at infinity focus according to Embodiment 5 of the variable magnification imaging optical system of the present invention. [Figure 44] This is a longitudinal aberration diagram at infinity focus at the telephoto end according to Embodiment 5 of the variable magnification imaging optical system of the present invention. [Figure 45] This is a diagram of the lateral aberration at the wide-angle end when the variable magnification imaging optical system of the present invention is in focus at infinity, according to Embodiment 5. [Figure 46] This is a diagram of the transverse aberration at infinity focus according to Embodiment 5 of the variable magnification imaging optical system of the present invention. [Figure 47] This is a diagram of the transverse aberration at infinity focus at the telephoto end according to Embodiment 5 of the variable magnification imaging optical system of the present invention. [Figure 48] This is a lateral aberration diagram of the wide-angle end at an object distance of 2.5m when the variable magnification imaging optical system of the present invention is in focus, according to Embodiment 5. [Figure 49] This is a lateral aberration diagram for Embodiment 5 of the variable magnification imaging optical system of the present invention, when the object distance is 2.5m and the intermediate focal length is in focus. [Figure 50]This is a lateral aberration diagram of Embodiment 5 of the variable magnification imaging optical system of the present invention when the object distance at the telephoto end is 2.5m and in focus. [Figure 51] This is a lens configuration diagram for Embodiment 6 of the variable magnification imaging optical system of the present invention, showing the lens configuration when the wide-angle end is focused at infinity. [Figure 52] This is a longitudinal aberration diagram at the wide-angle end when infinity is in focus, according to Embodiment 6 of the variable magnification imaging optical system of the present invention. [Figure 53] This is a longitudinal aberration diagram of the intermediate focal length at infinity focus according to Embodiment 6 of the variable magnification imaging optical system of the present invention. [Figure 54] This is a longitudinal aberration diagram at infinity focus at the telephoto end according to Embodiment 6 of the variable magnification imaging optical system of the present invention. [Figure 55] This is a diagram of the lateral aberration at the wide-angle end when the variable magnification imaging optical system of the present invention is in focus at infinity, according to Embodiment 6. [Figure 56] This is a lateral aberration diagram at infinity focus according to Embodiment 6 of the variable magnification imaging optical system of the present invention. [Figure 57] This is a diagram of the transverse aberration at infinity focus at the telephoto end according to Embodiment 6 of the variable magnification imaging optical system of the present invention. [Figure 58] This is a lateral aberration diagram of the wide-angle end at an object distance of 2.5m when the variable magnification imaging optical system of the present invention is in focus, according to Embodiment 6. [Figure 59] This is a lateral aberration diagram for Embodiment 6 of the variable magnification imaging optical system of the present invention, when the object distance is 2.5m and the intermediate focal length is in focus. [Figure 60] This is a lateral aberration diagram of Embodiment 6 of the variable magnification imaging optical system of the present invention, when the object distance at the telephoto end is 3.3m and in focus. [Modes for carrying out the invention]

[0016] The following describes a variable-magnification imaging optical system according to an embodiment of the present invention. The following description of the embodiment illustrates an example of a variable-magnification imaging optical system according to the present invention, and the present invention is not limited to this embodiment and can be modified within the scope of the invention without departing from its spirit. For example, it is possible to make surfaces formed as spheres or planes aspherical, to use optical element materials other than optical glass, such as crystalline materials or plastics, to use diffractive optical elements, or to apply an anti-reflective coating to the lens surface. Furthermore, the object side will be described as the front and the image side as the rear.

[0017] In describing embodiments of the present invention, when counting the number of lenses, unless otherwise specified, a single lens is counted as one lens, and in the case of a cemented lens, each single lens constituting it is counted as one lens. For example, a cemented lens consisting of a convex lens and a concave lens is counted as two lenses. For lenses that have a shape or structure that provides an aberration correction effect on a substrate lens such as a composite aspherical lens or a diffractive optical element using resin, the substrate and the added shape or structure are considered as one unit and counted as one lens. The bonding resin layer of a cemented lens is not counted as a lens. Even if the bonding resin of a cemented lens has an aberration correction effect, the resin part is considered as a structure added to one of the lenses being bonded and is not counted as a single lens. Parallel flat plates such as filters that do not have refractive power are also not counted as lenses.

[0018] Furthermore, in the description of embodiments of the present invention, the term "meniscus" used to define the shape of a lens refers to a lens in which the object-side and image-side surfaces are composed of curved surfaces having the same radius of curvature. For example, a concave meniscus lens with a convex surface facing the object side refers to a lens in which both the object-side and image-side surfaces have positive radii of curvature, with the image-side surface having a smaller radius of curvature. In the case of aspherical lenses, the lens shape is determined by the paraxial radius of curvature.

[0019] In the description of embodiments of the present invention, a lens group is defined as a plane whose spacing on the optical axis changes due to magnification or focusing, with the plane serving as the boundary between each lens group. Therefore, when the aperture diaphragm S moves independently due to magnification or focusing, the aperture diaphragm S is treated as a single lens group.

[0020] In the following description of the examples, the refractive indices of the materials for the g-line (wavelength 435.8 nm), F-line (486.1 nm), d-line (587.6 nm), and C-line (656.3 nm) are Ng, NF, Nd, and NC, respectively. Then, the Abbe number vd, partial dispersion ratio PgF, and anomalous dispersion ΔPgF are defined as follows: vd = (Nd-1) / (NF-NC) PgF = (Ng-NF) / (NF-NC) ΔPgF = PgF-0.64833+0.00180×vd It is expressed as follows.

[0021] In the description of embodiments of the present invention, there are mentions of ray heights such as on-axis marginal ray height and off-axis principal ray height. However, these basically refer to the distance from the optical axis, so the concepts of positive and negative do not arise, and the optical axis is treated as 0, with the direction away from it being treated as positive. However, regarding the off-axis principal rays in conditional equations (9) and (10), a positive and negative relationship arises because it deals with the relationship between the image height of the off-axis principal ray and the height of the off-axis principal ray passing through the second lens group G2.

[0022] In super-telephoto zoom lenses such as the variable magnification imaging optical system according to the present invention, suppressing chromatic aberration is an essential element for achieving high performance. There are two types of chromatic aberration: axial chromatic aberration and lateral chromatic aberration, and in order to suppress both of them throughout the entire zoom range, it is important to select appropriate glass materials according to the changes in power distribution.

[0023] In general, the chromatic aberration of an optical system composed of thin lenses is given by the sum of the aberrations of each lens as shown in (Reference Equation 1) below, and can be considered as follows. (Reference formula 1)Σ(h·hb·φ / v) h: On-axis marginal ray height hb: Off-axis principal ray height φ: Refractive force v: Abbe number Furthermore, the on-axial marginal ray is defined as the ray included in the on-axial beam that passes through the aperture at its maximum height from the optical axis, and the principal ray is defined as the ray that passes through the point where the aperture plane and the optical axis intersect.

[0024] When a lens with positive refractive power is placed on the object side of the aperture, the peripheral light beam passing through the lens will pass through the quadrant opposite to the image formation position. In the case of typical optical glass, due to the dispersion characteristics, longer wavelengths will be imaged at a lower image height, and the C line will be observed as underexposure chromatic aberration. Similarly, when a lens with negative refractive power is placed on the object side of the aperture, the opposite phenomenon occurs. Also, when a lens is placed on the image side of the aperture, the peripheral light beam passing through the lens and the image formation position will pass through the same quadrant, resulting in the opposite phenomenon to when the lens is placed on the object side of the aperture.

[0025] Similarly, the axial chromatic aberration of an optical system composed of thin lenses is given by the following (Reference Equation 2) as the sum of the aberrations of each lens, and can be considered as follows. (Reference formula 2)Σ(h·h·φ / v) h: On-axis marginal ray height φ: Refractive force v: Abbe number Furthermore, the on-axial marginal ray is defined as the ray included in the on-axial light beam that passes through the aperture at its maximum height from the optical axis.

[0026] Regarding (Reference Equation 2), focusing on the axial marginal ray height, lenses where the axial marginal ray passes at a higher position relative to the effective diameter exhibit greater axial chromatic aberration, while lenses where the axial marginal ray passes at a lower position exhibit less axial chromatic aberration. Therefore, to suppress axial and lateral chromatic aberration across the entire zoom range, it is necessary to appropriately select the glass material in accordance with the changes in ray height between the axial marginal ray and the off-axis principal ray that occur during zooming.

[0027] In super-telephoto zoom lenses, such as the variable magnification imaging optical system according to the present invention, where the first lens group has positive refractive power and extends significantly when magnifying from the wide-angle end to the telephoto end, widening the gap with the aperture diaphragm, chromatic aberration occurs in most cases where the C line is overexposed at the wide-angle end and underexposed at the telephoto end, and this fluctuates with magnification. Therefore, if the image is combined in a way that cancels out color between the g line and the C line, and the difference in imaging magnification with other wavelengths is large, a secondary spectrum of color fringing, such as reddish-purple, may appear around the outline of the subject, which is undesirable.

[0028] This phenomenon occurs because, when changing magnification from wide-angle to telephoto, the first lens group extends, widening the distance from the aperture diaphragm, and the subsequent lens groups move closer to the aperture diaphragm. This change in power distribution causes a significant alteration in the correction effect of chromatic aberration in the subsequent lens groups, in addition to the change in chromatic aberration occurring in the first lens group. The further away from the aperture diaphragm the lens group, the higher the off-axis principal rays pass, further away from the optical axis. As shown in (Reference Equation 1), this change in ray height leads to a change in chromatic aberration.

[0029] Furthermore, to correct secondary spectra, it is effective to appropriately arrange glass materials with anomalous dispersion properties in accordance with the change in the correction effect of magnification chromatic aberration due to the change in magnification. For example, in cases where chromatic aberration is corrected between the g-line and the C-line, but secondary spectra become a problem between the g-line and the d-line, if one tries to correct the chromatic aberration between the d-line and the C-line, the g-line will be insufficiently corrected. However, by using glass materials with anomalous dispersion properties, it becomes possible to compensate for the insufficient correction of the g-line, and as a result, secondary spectra can be reduced. Below, an embodiment of the present invention that suppresses secondary spectra across the entire zoom range and effectively corrects magnification chromatic aberration will be described, focusing on the correction of the g-line.

[0030] As can be seen from the numerical examples and the configuration diagrams of each example, the variable magnification imaging optical system according to the present invention consists of, in order from the object side, 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, an intermediate group GM consisting of one or more lens groups including an aperture diaphragm S, a focusing group GF, and a subsequent group GR consisting of one lens group. The spacing between adjacent lens groups changes during magnification, and the focusing group GF moves along the optical axis when focusing from an object at infinity to an object at close range.

[0031] The first lens group G1, which has positive refractive power, the second lens group G2, which also has positive refractive power, and the third lens group G3, which has negative refractive power, achieve the main magnification effect of the variable-magnification imaging optical system when the magnification changes from the wide-angle end to the telephoto end. In this way, the first lens group G1 moves toward the object, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. Furthermore, it is preferable that the second lens group G2 moves toward the image side when the magnification changes from the wide-angle end to the telephoto end, as this enhances the correction effect of chromatic aberration, which will be explained later.

[0032] When changing magnification from the wide-angle end to the telephoto end, the first lens group G1, which has positive refractive power, moves towards the object, increasing the distance between the first lens group G1 and the second lens group G2, and decreasing the distance between the second lens group G2 and the third lens group G3. The lens group including the aperture diaphragm S also moves towards the object, and the distance between the second lens group G2 and the aperture diaphragm S decreases. As a result, the off-axis principal rays in the second lens group G2, which passed at a high position at the wide-angle end, now pass at a lower position at the telephoto end. Consequently, the correction effect of chromatic aberration in the second lens group G2 is greater at the wide-angle end and smaller at the telephoto end.

[0033] On the other hand, the first lens group G1 moves towards the object at the telephoto end, and the distance between it and the second lens group G2 increases. As a result, the on-axial marginal ray height at infinity focus is lower for the second lens group G2 than for the first lens group G1, and for the second lens group G2, the on-axial marginal ray height at the telephoto end becomes lower than the off-axis principal ray height at the wide-angle end where the angle of view is at its maximum.

[0034] Furthermore, the second lens group G2 uses glass material with positive anomalous dispersion for the concave lens and glass material with negative anomalous dispersion for the convex lens, which makes it possible to correct the g-line in the underexposure direction at the wide-angle end, thus making it easier to correct chromatic aberration.

[0035] The intermediate group GM, consisting of one or more lens groups and including the aperture diaphragm S, has the effect of converging the light beam diverged by the third lens group G3, and controls the height of the light rays incident on the focusing group GF to an appropriate height. This contributes to the weight reduction of the focusing group GF and also plays a role in image plane compensation during magnification.

[0036] The focusing group GF moves along the optical axis when focusing from an object at infinity to an object at a close distance, correcting for shifts in the image formation position when the object distance changes.

[0037] The subsequent GR lens group, consisting of a single lens group, is responsible for image plane compensation and corrects chromatic aberration, which becomes more pronounced at the telephoto end. By using glass with positive anomalous dispersion for the concave lens and glass with negative anomalous dispersion for the convex lens of the subsequent GR lens group, an effect is created to correct the g-line in the overexposure direction, making it possible to correct chromatic aberration at the telephoto end. Furthermore, in the subsequent GR lens group, the on-axial marginal rays pass through at a lower ray height relative to the off-axis principal rays, so the deterioration of on-axial chromatic aberration is minimized, while the correction effect of chromatic aberration at the lateral end becomes greater at higher image heights.

[0038] On the other hand, if the subsequent GR group uses glass with positive anomalous dispersion for the concave lens and glass with negative anomalous dispersion for the convex lens to correct chromatic aberration at the telephoto end, the g-line will be overcorrected at the wide-angle end, worsening chromatic aberration. By offsetting this worsening of chromatic aberration at the wide-angle end with the corrective effect of the second lens group G2, which has a significant effect of correcting the g-line in the under-correction direction at the wide-angle end, it becomes possible to correct chromatic aberration well across the entire range from the wide-angle end to the telephoto end.

[0039] In the variable magnification imaging optical system according to the present invention, it is desirable to arrange one or more concave lenses satisfying the following condition (1) between the aperture diaphragm S and the subsequent lens group GR in order to effectively correct the magnification chromatic aberration that occurs at the telephoto end. (1)ΔPgFLnSr>0.013 ΔPgFLnSr: Anomalous dispersion of the concave lens placed between the aperture diaphragm S and the subsequent lens group GR.

[0040] In the variable magnification imaging optical system according to the present invention, at the telephoto end, short wavelengths, especially those shorter than the g-line, are not adequately corrected, resulting in a decrease in imaging magnification and residual chromatic aberration in the underexposure direction. To effectively correct this, it is desirable to use a glass material with a large ΔPgF and strong positive anomalous dispersion for the concave lens group behind the aperture diaphragm S. By satisfying condition (1), it becomes possible to effectively correct chromatic aberration that occurs at the telephoto end.

[0041] When the lower limit of condition (1) is exceeded and the anomalous dispersion of the concave lens positioned between the aperture diaphragm S and the subsequent lens group GR decreases, the effect of overcorrecting the g line at the peripheral image height on the telephoto side decreases, making it difficult to correct chromatic aberration across the entire zoom range.

[0042] Furthermore, regarding the lower limit of conditional equation (1), it is possible to more reliably achieve the aforementioned effect by specifying the lower limit as 0.015, and more preferably as 0.020.

[0043] In the variable magnification imaging optical system according to the present invention, it is desirable that the first lens group G1 includes a concave lens that satisfies the following condition (2) in order to achieve both a reduction in the overall length of the optical system and improved performance. (2) ndLN1 < 1.80 ndLN1: Refractive index of the concave lens with the highest refractive index included in the first lens group G1.

[0044] Conditional equation (2) specifies the refractive index of the concave lens with the highest refractive index included in the first lens group G1. In super-telephoto zoom lenses with a narrow field of view, such as the variable magnification imaging optical system according to the present invention, suppressing chromatic aberration is essential for high performance. To suppress chromatic aberration occurring in the first lens group which has positive refractive power, special low-dispersion lenses with high positive anomalous dispersion or glass materials such as fluorite are used for the convex lenses and combined with concave lenses to provide an achromatic effect. However, if high-refractive-index glass materials are used for the concave lenses, the Petzval sum deteriorates, making it difficult to ensure the flatness of the image plane. By including a concave lens that satisfies conditional equation (2) in the first lens group G1, it becomes possible to achieve both a reduction in the overall length of the optical system and high performance.

[0045] If the upper limit of condition (2) is exceeded and the refractive index of the highest refractive index concave lens included in the first lens group G1 becomes high, the Petzval sum deteriorates, making it difficult to ensure the flatness of the image plane, which is undesirable.

[0046] Furthermore, regarding condition (2), it is possible to make the aforementioned effect more certain by preferably setting the upper limit to 1.75, and even more preferably to 1.73.

[0047] Furthermore, in the variable magnification imaging optical system according to the present invention, conditional equations (3) to (6) define the relationship between the second lens group G2 and the lens groups before and after it, which is necessary for the second lens group G2 to effectively correct the chromatic aberration of magnification that changes with zooming from the wide-angle end to the telephoto end.

[0048] In the variable magnification imaging optical system according to the present invention, it is desirable that the second lens group G2 satisfies the following condition (3) in order to effectively correct the chromatic aberration of magnification that changes with zooming from the wide-angle end to the telephoto end. (3) 0.005 <DG1G2W / DG1G2T<0.400 DG1G2W: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the wide-angle end at infinity. DG1G2T: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the infinity telephoto end.

[0049] Conditional equation (3) specifies the ratio of the distance between the first lens group G1 and the second lens group G2 on the optical axis at the wide-angle end and the telephoto end at infinity. It is desirable that the second lens group G2 has a corrective effect on lateral chromatic aberration, correcting the g-line in the under-angle direction at the wide-angle end. To enhance this effect, it is desirable that the off-axis principal ray height passes through a higher position at the wide-angle end, and as mentioned above, it is desirable that the on-axis marginal ray height passes through a lower position at the telephoto end. Therefore, it is desirable that the distance between the first lens group G1 and the second lens group G2 be small at the wide-angle end and large at the telephoto end. By satisfying conditional equation (3), it becomes possible to miniaturize the lens while effectively correcting lateral chromatic aberration.

[0050] If the upper limit of condition (3) is exceeded, and the ratio of the distance between the first lens group G1 and the second lens group G2 on the optical axis at the wide-angle end and the telephoto end at infinity becomes large, the distance between the first lens group G1 and the second lens group G2 at the telephoto end becomes small, and the axial marginal ray height does not decrease sufficiently at the telephoto end, leading to a deterioration of axial chromatic aberration, which is undesirable. Also, if the distance between the first lens group G1 and the second lens group G2 becomes large at the wide-angle end, it will have the effect of increasing the overall length of the product, which is also undesirable.

[0051] If the lower limit of condition (3) is exceeded, and the ratio of the distance between the first lens group G1 and the second lens group G2 on the optical axis at the infinity wide-angle end and the infinity telephoto end becomes small, the change in the off-axis principal rays in the second lens group G2 becomes too large when zooming from the infinity wide-angle end to the infinity telephoto end, making it difficult to correct astigmatism and field curvature, which is undesirable.

[0052] Furthermore, regarding condition (3), it is preferable to set the lower limit to 0.009 and the upper limit to 0.250 to make the aforementioned effect more certain.

[0053] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable that the second lens group G2 satisfies the following condition (4) in order to effectively correct the chromatic aberration of magnification that changes with zooming from the wide-angle end to the telephoto end. (4) 1.00 <DG2G3W / DG2G3T<80.00 DG2G3W: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end of infinity. DG2G3T: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end.

[0054] Conditional equation (4) specifies the ratio of the distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end and the telephoto end at infinity. It is desirable that the second lens group G2 has a corrective effect on lateral chromatic aberration, correcting the g-line in the under-angle direction at the wide-angle end. To enhance this effect, it is desirable that the off-axis principal ray height passes through a higher position at the wide-angle end, and as mentioned above, it is desirable that the on-axis marginal ray height passes through a lower position at the telephoto end. Therefore, it is desirable that the distance between the second lens group G2 and the third lens group G3 be large at the wide-angle end and small at the telephoto end. By satisfying conditional equation (4), it is possible to effectively correct lateral chromatic aberration.

[0055] If the upper limit of condition (4) is exceeded, and the ratio of the distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity wide-angle end and the infinity telephoto end becomes large, the change in the off-axis principal ray in the second lens group G2 becomes too large when zooming from the infinity wide-angle end to the infinity telephoto end, making it difficult to correct astigmatism and field curvature, which is undesirable.

[0056] If the lower limit of condition (4) is exceeded and the ratio of the distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end and the telephoto end at infinity becomes small, the distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end becomes small, and the off-axis principal ray height cannot pass through a sufficiently high position at the wide-angle end, reducing the magnification chromatic aberration correction effect that corrects the g-line in the underexposure direction, which is undesirable. Also, if the distance between the second lens group G2 and the third lens group G3 on the optical axis becomes large at the telephoto end, the on-axial marginal ray height passing through the second lens group G2 at the telephoto end does not decrease sufficiently, leading to a deterioration of on-axial chromatic aberration, which is undesirable.

[0057] Furthermore, regarding conditional equation (4), it is preferable to set the lower limit to 2.00 and the upper limit to 40.00 to make the aforementioned effect more certain.

[0058] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (5) in order to effectively correct the chromatic aberration of magnification that fluctuates when the second lens group G2 moves by zooming from the wide-angle end to the telephoto end. (5) 0.01 <DG1G2W / DG2G3W<2.00 DG1G2W: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the wide-angle end at infinity. DG2G3W: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end of infinity.

[0059] Conditional equation (5) specifies the ratio of the distance on the optical axis between the first lens group G1 and the second lens group G2, and the distance on the optical axis between the second lens group G2 and the third lens group G3, at the wide-angle end at infinity. It is desirable that the second lens group G2 has a corrective effect on lateral chromatic aberration, correcting the g-line in the under-angle direction at the wide-angle end. To enhance this effect, it is desirable that the off-axis principal ray height passes through a higher position at the wide-angle end, and as mentioned above, it is desirable that the on-axis marginal ray height passes through a lower position at the telephoto end. Therefore, at the wide-angle end at infinity, the closer the second lens group G2 is to the first lens group G1, the shorter the distance to the first lens group G1, and the wider the distance to the third lens group G3, the higher the off-axis principal ray height passing through the second lens group G2, and thus the more effectively lateral chromatic aberration is corrected. By satisfying condition (5), it becomes possible to effectively correct the chromatic aberration of magnification that fluctuates as the second lens group G2 moves from the wide-angle end to the telephoto end during zooming.

[0060] When the upper limit of condition (5) is exceeded, and the ratio of the distance between the first lens group G1 and the second lens group G2 on the optical axis to the distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end at infinity becomes large, the second lens group G2 comes too close to the third lens group G3 at the wide-angle end at infinity. As a result, the off-axis principal rays passing through the second lens group G2 pass at a low position, making it difficult to effectively correct chromatic aberration, which is undesirable.

[0061] If the lower limit of condition (5) is exceeded, and the ratio of the distance between the first lens group G1 and the second lens group G2 on the optical axis to the distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end at infinity becomes small, the second lens group G2 will come too close to the first lens group G1 at the wide-angle end at infinity. This will cause the off-axis principal rays passing through the second lens group G2 to pass at a higher position, increasing the effective diameter of the second lens group G2 and increasing the weight of the optical system, which is undesirable.

[0062] Furthermore, regarding condition (5), it is preferable to set the lower limit to 0.03 and the upper limit to 1.50 to make the aforementioned effect more certain.

[0063] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (6) in order to effectively correct the chromatic aberration of magnification that fluctuates when the second lens group G2 moves by zooming from the wide-angle end to the telephoto end. (6) 2.0 <DG1G2T / DG2G3T<200.0 DG1G2T: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the infinity telephoto end. DG2G3T: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end.

[0064] Conditional equation (6) specifies the ratio of the distance on the optical axis between the first lens group G1 and the second lens group G2, and the distance on the optical axis between the second lens group G2 and the third lens group G3 at the infinity telephoto end. It is desirable that the second lens group G2 has a corrective effect on lateral chromatic aberration, correcting the g-line in the under-angle direction at the wide-angle end. To enhance this effect, it is desirable that the off-axis principal ray height passes at a higher position at the wide-angle end, and as mentioned above, it is desirable that the on-axial marginal ray height passes at a lower position at the telephoto end. Therefore, at the infinity telephoto end, if the second lens group G2 is closer to the third lens group G3, the distance between it and the first lens group G1 increases, and the distance between it and the third lens group G3 decreases, the on-axial marginal ray passes at a lower position, thus suppressing the deterioration of axial chromatic aberration. By satisfying conditional equation (6), it is possible to effectively correct the lateral chromatic aberration that fluctuates when the second lens group G2 moves due to zooming from the wide-angle end to the telephoto end.

[0065] If the upper limit of condition (6) is exceeded, and the ratio of the distance between the first lens group G1 and the second lens group G2 on the optical axis to the distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end becomes large, the distance between the first lens group G1 and the second lens group G2 on the optical axis at the infinity telephoto end becomes too large, causing the optical system to become bloated, which is undesirable.

[0066] When the lower limit of condition (6) is exceeded, and the ratio of the distance between the first lens group G1 and the second lens group G2 on the optical axis to the distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end becomes small, the distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end does not decrease, and the axial marginal rays pass through a higher point, which leads to a deterioration of axial chromatic aberration and is undesirable.

[0067] Furthermore, regarding conditional equation (6), it is possible to more reliably achieve the aforementioned effect by preferably setting the lower limit to 3.0 and the upper limit to 150.0, and more preferably setting the lower limit to 4.0 and the upper limit to 120.0.

[0068] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (7) in order to achieve effective correction of chromatic aberration across the entire zoom range. (7) 1.2 <DG2Sw / DG2St<5.0 DG2Sw: Distance from the top of the lens face closest to the object in the second lens group G2 at the wide-angle end to the aperture diaphragm S. DG2St: Distance from the top of the lens face closest to the object in the second lens group G2 at the telephoto end to the aperture diaphragm S.

[0069] Conditional equation (7) defines a desirable range for the ratio of the distance from the top of the object side of the lens closest to the object in the second lens group G2 to the aperture diaphragm S at the wide-angle end and the telephoto end. As described above, when the magnification of the variable-magnification imaging optical system according to the present invention changes from the wide-angle end to the telephoto end, the second lens group G2 moves toward the image side, and the distance between it and the third lens group G3 decreases, so the distance to the aperture diaphragm S included in the intermediate group GM decreases. Since it is desirable that the effect of correcting chromatic aberration of magnification by the second lens group G2 be large at the wide-angle end and small at the telephoto end, it is desirable that the second lens group G2 approaches the aperture diaphragm S at the telephoto end, and the height of the off-axis principal rays passing through the second lens group G2 decreases. By satisfying conditional equation (7), effective correction of chromatic aberration of magnification is possible throughout the entire zoom range.

[0070] When the lower limit of condition (7) is exceeded, and the ratio of the distance from the top of the object's side to the aperture of the lens closest to the object in the second lens group G2 at the wide-angle and telephoto ends becomes small, the amount of change due to the scaling of the distance between the second lens group G2 and the aperture aperture S becomes small, and the change due to the scaling of the off-axis principal rays passing through the second lens group G2 becomes small. As a result, the change in the correction effect of chromatic aberration becomes small, making it difficult to effectively correct chromatic aberration throughout the entire zoom range, which is undesirable.

[0071] When the upper limit of condition (7) is exceeded, and the ratio of the distance from the top of the object's side surface to the aperture of the lens closest to the object in the second lens group G2 at the wide-angle and telephoto ends becomes large, the amount of change due to the scaling of the distance between the second lens group G2 and the aperture aperture S becomes large, requiring the off-axis light beam at the wide-angle end to pass through a higher point, which leads to an increase in the outer diameter of the second lens group G2, and is therefore undesirable.

[0072] Furthermore, regarding conditional equation (7), it is preferable to set the lower limit to 1.4 and the upper limit to 3.5 to make the aforementioned effect more certain.

[0073] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (8) in order to effectively correct axial chromatic aberration and lateral chromatic aberration throughout the entire zoom range. (8) 0.2 <g2AXhW / g2AXhT<1.5 g2AXhW: Height of the axial marginal rays on the leading plane of the second lens group G2 at the wide-angle end at infinity with the aperture wide open. g2AXhT: Height of the axial marginal rays on the leading plane of the second lens group G2 at the telephoto end at infinity with the aperture wide open. On-axial marginal rays are defined as the rays included in the on-axial beam that pass through the aperture at the maximum height from the optical axis.

[0074] Conditional equation (8) defines the ratio of the height of the axial marginal rays on the leading surface of the second lens group G2 at the wide-angle end at infinity with the aperture wide open, to the height of the axial marginal rays on the leading surface of the second lens group G2 at the telephoto end at infinity with the aperture wide open. In the second lens group G2, as mentioned above, it is desirable to use glass material with positive anomalous dispersion for the concave lens in order to correct the g line in the underexposure direction at the wide-angle end and suppress lateral chromatic aberration. On the other hand, if glass material with strong positive anomalous dispersion and a large ΔPgF is used for the concave lens of the second lens group G2, the image formation position of the g line and C line in the axial beam shifts towards the image side, which acts in the direction of increasing the secondary spectrum and is detrimental to the correction of axial chromatic aberration. Furthermore, axial chromatic aberration becomes more noticeable as the angle of view narrows towards the telephoto end, so in order to improve image quality, the deterioration of axial chromatic aberration must also be suppressed. Therefore, in order to use glass materials with strong positive anomalous dispersion, which are advantageous for correcting lateral chromatic aberration at the wide-angle end, while preventing deterioration of axial chromatic aberration, it is necessary to control the axial marginal ray height to be small relative to the effective diameter of the second lens group G2 (in the case of the second lens group G2, the effective diameter is determined by the height of the off-axis light beam at the maximum angle of view at the wide-angle end), and the control of the axial marginal ray height is particularly important at the telephoto end. By satisfying condition (8), it becomes possible to effectively correct axial chromatic aberration and lateral chromatic aberration throughout the entire zoom range.

[0075] When the upper limit of condition (8) is exceeded, and the ratio of the height of the axial marginal rays on the leading surface of the second lens group G2 at the wide-angle end at infinity with the aperture wide open to the height of the axial marginal rays on the leading surface of the second lens group G2 at the telephoto end at infinity with the aperture wide open becomes large, the height of the axial marginal rays on the leading surface of the second lens group G2 at the wide-angle end at infinity with the aperture wide open becomes too large, making it difficult to correct axial chromatic aberration on the wide-angle side. At the same time, it becomes necessary to increase the refractive power of the first lens group G1 in order to lower the height of the axial marginal rays on the telephoto side, which leads to a deterioration of various aberrations and makes it difficult to improve performance.

[0076] When the lower limit of condition (8) is exceeded, and the ratio of the height of the axial marginal rays on the leading surface of the second lens group G2 at the wide-angle end at infinity with the aperture wide open to the height of the axial marginal rays on the leading surface of the second lens group G2 at the telephoto end at infinity with the aperture wide open becomes small, the height of the axial marginal rays on the leading surface of the second lens group G2 at the telephoto end at infinity with the aperture wide open becomes large, making it difficult to correct axial chromatic aberration and hindering high performance.

[0077] Furthermore, regarding conditional equation (8), it is possible to more reliably achieve the aforementioned effect by preferably setting the lower limit to 0.3 and the upper limit to 1.3, and even more preferably setting the lower limit to 0.4 and the upper limit to 1.1.

[0078] Furthermore, in the variable magnification imaging optical system according to the present invention, the second lens group G2, which exhibits a large change in the ray height of the off-axis principal rays when zooming from the wide-angle end to the telephoto end, plays an important role in effectively correcting the chromatic aberration of magnification that fluctuates with zooming. To improve the performance of the optical system, it is desirable to satisfy the following conditions (9) and (10). (9)-1.8<(g2OAhW / Wih)-(g2OAhT / Tih)<-0.3 (10) 0.6 < |g2OAhW / g2AXhT| < 2.5 With: Image height of the off-axis principal ray at the widest angle of view at infinity. Tih: Image height of the off-axis principal ray at the maximum field of view at the telephoto end of infinity. g2OAhW: Height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end of infinity. g2OAhT: Height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the infinity telephoto end. g2AXhT: Height of the axial marginal rays on the leading plane of the second lens group G2 at the telephoto end at infinity with the aperture wide open. Note that the g2OAhW ray corresponds to Wih, and the g2OAhT ray corresponds to Tih. The second lens group G2 is located on the object side of the aperture diaphragm S, and the quadrant through which the rays pass is reversed, so g2OAhW and g2OAhT have opposite signs for Wih and Tih. Furthermore, the on-axial marginal ray is defined as the ray included in the on-axial beam that passes through the diaphragm at the maximum height from the optical axis.

[0079] Conditional equation (9) defines a desirable range for the difference between the ratio of the height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end at infinity to the image height of the off-axis principal rays at the maximum angle of view at the wide-angle end, and the ratio of the height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at infinity to the image height of the off-axis principal rays at the telephoto end at infinity. When this difference approaches 0 and becomes large, it means that the change in the off-axis principal rays in the second lens group G2 is small when zooming from the wide-angle end at infinity to the telephoto end at infinity. Conversely, when it moves away from 0 and becomes small, it means that the change in the off-axis principal rays in the second lens group G2 is large when zooming from the wide-angle end at infinity to the telephoto end at infinity. By satisfying conditional equation (9), it becomes possible to effectively correct the chromatic aberration of magnification that fluctuates with zooming.

[0080] When the upper limit of condition (9) is exceeded, and the difference between the ratio of the height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end and the image height of the off-axis principal rays at the maximum angle of view at the wide-angle end, and the ratio of the height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the telephoto end, increases in a way that approaches 0, the change in the off-axis principal rays in the second lens group G2 becomes smaller when zooming from the wide-angle end to the telephoto end, the correction effect of chromatic aberration becomes smaller, and chromatic aberration cannot be sufficiently corrected at either the wide-angle or telephoto end, which is undesirable.

[0081] When the lower limit of condition (9) is exceeded, and the difference between the ratio of the height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end and the image height of the off-axis principal rays at the maximum angle of view at the wide-angle end, and the ratio of the height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the telephoto end and the image height of the off-axis principal rays at the telephoto end, decreases in the direction away from 0, the change in the off-axis principal rays in the second lens group G2 becomes too large when zooming from the wide-angle end to the telephoto end, making it difficult to correct astigmatism and field curvature, which is undesirable.

[0082] Furthermore, regarding conditional equation (9), it is preferable to set the lower limit to -1.5 and the upper limit to -0.4 to make the aforementioned effect more certain.

[0083] Condition (10) defines the absolute value of the ratio between the height of the off-axis principal ray at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end at infinity and the height of the on-axis marginal ray at the leading surface of the second lens group G2 at the telephoto end at infinity with the aperture wide open. The off-axis principal ray defined in condition (10) refers to the off-axis principal ray at the maximum angle of view at the wide-angle end at infinity, as defined in condition (9). By satisfying condition (10), it becomes possible to effectively correct chromatic aberration that fluctuates with zooming.

[0084] When the upper limit of condition (10) is exceeded, and the absolute value of the ratio between the height of the off-axis principal ray at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end at infinity and the height of the on-axis marginal ray on the leading surface of the second lens group G2 at the telephoto end at infinity with the aperture wide open becomes large, it becomes necessary to increase the refractive power of the first lens group G1 in order to lower the height of the on-axis marginal ray at the telephoto end, which leads to a deterioration of various aberrations and makes it difficult to improve performance.

[0085] When the lower limit of condition (10) is exceeded, and the absolute value of the ratio between the height of the off-axis principal ray at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end at infinity and the height of the on-axis marginal ray at the leading surface of the second lens group G2 at the telephoto end at infinity with the aperture wide open becomes small, the height of the on-axis marginal ray does not decrease sufficiently on the telephoto side, increasing the on-axis chromatic aberration generated in the second lens group G2 and making it difficult to achieve high performance. Also, the absolute value of the height of the off-axis principal ray at the maximum angle of view at the wide-angle end at infinity becomes small (simply put, without considering the concept of signs, this is equivalent to the height of the off-axis principal ray from the optical axis becoming lower), making it difficult to correct lateral chromatic aberration on the wide-angle side and making it difficult to achieve high performance.

[0086] Furthermore, regarding conditional equation (10), it is preferable to set the lower limit to 0.8 and the upper limit to 1.9 to make the aforementioned effect more certain.

[0087] Furthermore, in the variable magnification imaging optical system according to the present invention, the second lens group G2, which exhibits a large change in the ray height of the off-axis principal rays when zooming from the wide-angle end to the telephoto end, plays an important role in effectively correcting the chromatic aberration of magnification that fluctuates with zooming, and it is desirable that at least one of these lenses be a concave lens.

[0088] In the second lens group G2, it is important to use glass materials that have the effect of correcting the g-line in the underexposure direction at the wide-angle end, in order to effectively correct chromatic aberration at the wide-angle end. For convex lenses, it is desirable to select glass materials with negative anomalous dispersion, and for concave lenses, it is desirable to select glass materials with positive anomalous dispersion. Examples of glass materials with negative anomalous dispersion from HOYA include high refractive index, low dispersion glass materials such as TAFD30 and Kurzflint-type glass materials such as LAF45. Examples of glass materials with positive anomalous dispersion from HOYA include low refractive index, low dispersion glass materials such as FCD1, high refractive index, high dispersion glass materials such as E-FDS1-W and high dispersion glass materials such as FD270. Comparing the two, glass materials with positive anomalous dispersion have a larger number of glass types and greater freedom in glass material selection, and also have greater anomalous dispersion. Therefore, it is desirable to place at least one concave lens in the second lens group G2, and it is desirable that this concave lens be made of glass material with high positive anomalous dispersion. By including at least one concave lens in the second lens group G2, it becomes possible to effectively correct chromatic aberration that fluctuates with zooming.

[0089] Furthermore, in the variable magnification imaging optical system according to the present invention, the second lens group G2, which experiences a large change in the ray height of the off-axis principal rays when zooming from the wide-angle end to the telephoto end, plays an important role in effectively correcting the chromatic aberration of magnification that fluctuates with zooming. For this purpose, it is desirable to include at least one concave lens that satisfies the following condition (11). (11)ΔPgFLg2>0.0090 ΔPgFLg2: Anomalous dispersion of the concave lens with the greatest anomalous dispersion among the concave lenses included in the second lens group G2.

[0090] Conditional equation (11) specifies the desirable range of anomalous dispersion for one or more concave lenses included in the second lens group G2. Note that the concave lenses referred to here may be individual lenses or concave lenses that are part of a cemented lens.

[0091] As mentioned above, the second lens group G2 moves toward the image plane when zooming from the wide-angle end to the telephoto end, and the off-axis principal rays passing through the second lens group G2 pass at a higher position at the wide-angle end and a lower position at the telephoto end. In order to suppress chromatic aberration across the entire zoom range and improve performance, the second lens group G2 needs to correct the g-line to be more underexposed at the wide-angle end. Therefore, a large ΔPgF and strong positive anomalous dispersion are advantageous for correcting the g-line. By satisfying condition (11), it becomes possible to effectively correct chromatic aberration that fluctuates with zooming.

[0092] When the anomalous dispersion of the concave lens with the greatest anomalous dispersion among the concave lenses included in the second lens group G2 decreases beyond the lower limit of condition equation (11), the effect of correcting the g line to be underexposed at the wide-angle end decreases, making it difficult to suppress chromatic aberration across the entire zoom range and improve performance.

[0093] Furthermore, regarding conditional equation (11), the aforementioned effect can be made more certain by preferably setting the lower limit to 0.0095, more preferably to 0.0100, and even more preferably to 0.0150.

[0094] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable that the subsequent group GR includes at least one concave lens that satisfies the following condition (12). Note that the concave lens referred to here may be a lens arranged individually or a concave lens arranged as part of a cemented lens. (12)ΔPgFnLr>0.009 ΔPgFnLr: Anomalous dispersion of concave lenses in the subsequent GR group

[0095] Conditional equation (12) specifies the anomalous dispersion of concave lenses, which are desirable to include one or more in the subsequent group GR of the variable magnification imaging optical system according to the present invention. In the variable magnification imaging optical system according to the present invention, at the telephoto end, short wavelengths, especially light rays shorter than the g-line, are not adequately corrected, resulting in a decrease in imaging magnification and remaining chromatic aberration in the underexposure direction. To effectively correct this, it is desirable to use glass material with a large ΔPgF and strong positive anomalous dispersion for the concave lenses in the group behind the aperture diaphragm S. By satisfying conditional equation (12), it becomes possible to effectively correct chromatic aberration across the entire zoom range.

[0096] When the lower limit of condition (12) is exceeded and the anomalous dispersion of the concave lens constituting the subsequent GR group decreases, the effect of overcorrecting the g line at the peripheral image height on the telephoto side decreases, making it difficult to correct chromatic aberration across the entire zoom range.

[0097] Furthermore, regarding the lower limit of conditional equation (12), it is possible to make the aforementioned effect more certain by specifying the lower limit as 0.010, more preferably 0.011, and even more preferably 0.013.

[0098] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable that the subsequent group GR includes at least one concave lens that satisfies the following condition (13). Note that the concave lens referred to here may be a lens arranged individually or a concave lens arranged as part of a cemented lens. (13)vdnLr×ΔPgFnLr>0.80 vdnLr: Abbe number of concave lenses included in the subsequent group GR ΔPgFnLr: Anomalous dispersion of concave lenses included in the subsequent group GR

[0099] Conditional equation (13) defines the relationship between the Abbe number and anomalous dispersion of concave lenses, which are desirable to include in the subsequent group GR of the variable magnification imaging optical system according to the present invention, with one or more lenses. In the variable magnification imaging optical system according to the present invention, at the telephoto end, short wavelengths, especially light rays shorter than the g-line, are undercorrected, resulting in a decrease in imaging magnification and remaining chromatic aberration in the underexposure direction. To effectively correct this, it is desirable to use glass materials with a large ΔPgF and large positive anomalous dispersion for the concave lenses in the group behind the aperture diaphragm S. Furthermore, glass materials that satisfy conditional equation (12) generally have a relatively low refractive index of about 1.7 or less, and not only do they have the anomalous dispersion desirable for correcting chromatic aberration, but their low refractive index is also advantageous for correcting the Petzval sum. By satisfying conditional equation (13), it becomes possible to effectively correct chromatic aberration across the entire zoom range.

[0100] When the lower limit of condition (13) is exceeded and the anomalous dispersion of at least one concave lens included in the subsequent GR group decreases, the effect of overcorrecting the g line at the peripheral image height on the telephoto side decreases, making it difficult to correct chromatic aberration across the entire zoom range.

[0101] Furthermore, regarding the lower limit of conditional equation (13), it is possible to more reliably achieve the aforementioned effect by specifying the lower limit as 0.85, and more preferably as 0.90.

[0102] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable that the subsequent group GR includes at least one convex lens that satisfies the following condition (14). Note that the convex lens referred to here may be a lens arranged individually or a convex lens arranged as part of a cemented lens. (14)ΔPgFpLr<-0.0010 ΔPgFpLr: Anomalous dispersion of convex lenses included in the subsequent group GR

[0103] Conditional equation (14) specifies the anomalous dispersion of at least one convex lens included in the subsequent group GR of the variable magnification imaging optical system according to the present invention. In the variable magnification imaging optical system according to the present invention, the imaging magnification of short wavelengths, especially from the g-line onwards, decreases at the telephoto end, and chromatic aberration in the underexposure direction remains. To effectively correct this, it is desirable to use glass material with a small ΔPgF and strong negative anomalous dispersion for the convex lenses in the group behind the aperture diaphragm S. By satisfying conditional equation (14), it becomes possible to effectively correct chromatic aberration across the entire zoom range.

[0104] If the upper limit of condition (14) is exceeded and the anomalous dispersion of at least one convex lens included in the subsequent GR group becomes large, the effect of overcorrecting the g line at the telephoto end decreases, making it difficult to suppress chromatic aberration across the entire zoom range.

[0105] Furthermore, regarding conditional equation (14), the aforementioned effect can be made more certain by specifying the upper limit to -0.0020 if preferable, -0.0030 if more preferable, and -0.0040 if even more preferable.

[0106] Furthermore, in the variable-magnification imaging optical system according to the present invention, it is desirable that the average value of the anomalous dispersion of the two convex lenses closest to the image side satisfies the range of condition equation (15). Note that the convex lenses referred to here may be lenses arranged individually or convex lenses arranged as part of a cemented lens. (15)ΔPgFprAVE<-0.0010 ΔPgFprAVE: Average value of the anomalous dispersion of the two convex lenses closest to the image.

[0107] Conditional equation (15) defines the average value of the anomalous dispersion of the two convex lenses closest to the image in the variable magnification imaging optical system according to the present invention. In the variable magnification imaging optical system according to the present invention, the imaging magnification of short wavelengths, especially from the g-line onwards, decreases at the telephoto end, and chromatic aberration in the underexposure direction remains. To effectively correct this, it is desirable to use glass material with a small ΔPgF and strong negative anomalous dispersion for the convex lenses in the group behind the aperture diaphragm S. Furthermore, the closer the lens is to the image side, the higher the correction effect of chromatic aberration in terms of lateral aberration because off-axis rays pass through higher points.

[0108] When the upper limit of condition (15) is exceeded and the average value of the anomalous dispersion of the two convex lenses closest to the image becomes large, the effect of overcorrecting the g line at the telephoto end decreases, making it difficult to suppress chromatic aberration across the entire zoom range.

[0109] Furthermore, regarding conditional equation (15), the aforementioned effect can be made more certain by specifying the upper limit to -0.0020 if preferable, -0.0030 if more preferable, and -0.0040 if even more preferable.

[0110] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (16) in order to achieve both a reduction in the overall length of the optical system and improved performance. (16) 0.18 <f1 / fT<1.00 f1: Focal length of the first lens group G1 fT: Focal length of the variable magnification optical system at the telephoto end of infinity.

[0111] Conditional equation (16) defines the ratio of the focal length of the first lens group G1 to the focal length of the variable magnification imaging optical system at the infinity telephoto end, indicating a desirable range for shortening the overall length of the optical system and reducing the weight of the lens barrel. By satisfying conditional equation (16), it is possible to achieve both a reduction in the overall optical length and improved performance.

[0112] If the upper limit of condition (16) is exceeded and the focal length of the first lens group G1 becomes longer than the focal length of the variable magnification imaging optical system at the infinity telephoto end, the overall optical length at the telephoto end becomes too long, increasing the amount of movement of the first lens group G1 due to zooming, making the movement mechanism more complex and resulting in a larger lens barrel.

[0113] When the lower limit of condition (16) is exceeded, and the focal length of the first lens group G1 becomes shorter than the focal length of the variable magnification imaging optical system at the infinity telephoto end, the imaging magnification of the combined system from the second lens group G2 onwards at the telephoto end becomes too high, making it difficult to correct aberrations such as axial chromatic aberration at the telephoto end.

[0114] Furthermore, regarding conditional equation (16), it is possible to more reliably achieve the aforementioned effect by preferably setting the lower limit to 0.20 and the upper limit to 0.85, and even more preferably setting the lower limit to 0.24 and the upper limit to 0.70.

[0115] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (17) in order to achieve both a reduction in the overall length of the optical system and improved performance. (17) 0.1 <f2 / fT<1.4 f2: Focal length of the second lens group G2 fT: Focal length of the variable magnification optical system at the telephoto end of infinity.

[0116] Conditional equation (17) defines the ratio of the focal length of the second lens group G2 to the focal length of the variable magnification imaging optical system at the infinity telephoto end, and indicates the desirable range for shortening the overall length of the optical system and reducing the weight of the lens barrel. Satisfying conditional equation (17) makes it possible to shorten the overall optical length and reduce the weight of the lens barrel.

[0117] If the upper limit of condition (17) is exceeded and the focal length of the second lens group G2 becomes longer than the focal length of the variable magnification imaging optical system at the infinity telephoto end, the combined positive refractive power of the first lens group G1 and the second lens group G2 decreases, making it difficult to shorten the overall length of the optical system. Furthermore, if the insufficient combined refractive power of the first lens group G1 and the second lens group G2 is compensated for by strengthening the refractive power of the first lens group G1, it becomes difficult to use low refractive index, low dispersion glass such as fluorite for the convex lens of the first lens group G1, which plays an important role in correcting axial chromatic aberration, making it difficult to improve performance.

[0118] When the lower limit of condition (17) is exceeded and the focal length of the second lens group G2 becomes smaller than the focal length of the variable magnification imaging optical system at the infinity telephoto end, the refractive power of the second lens group G2 increases, making it difficult to suppress astigmatism, especially at the wide-angle end where the off-axis principal rays pass at a high position, and thus making it difficult to improve performance.

[0119] Furthermore, regarding conditional equation (17), it is preferable to specify a lower limit of 0.20 and an upper limit of 1.10 to make the aforementioned effect more certain.

[0120] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (18) in order to achieve both a reduction in the overall length of the optical system and improved performance. (18) 0.6 <f1 / f2<2.2 f1: Focal length of the first lens group G1 f2: Focal length of the first lens group G2

[0121] Conditional equation (18) indicates the desirable range for the ratio of the focal lengths of the first lens group G1 and the second lens group G2. By satisfying conditional equation (18), it is possible to achieve both a reduction in the overall optical length and improved performance.

[0122] When the upper limit of condition (18) is exceeded and the ratio of the focal lengths of the first lens group G1 to the second lens group G2 becomes large, it means that the refractive power of the first lens group G1 becomes smaller than that of the second lens group G2. This is undesirable because it leads to insufficient refractive power of the first lens group G1 and an increase in the size of the optical system.

[0123] When the lower limit of condition (18) is exceeded and the ratio of the focal lengths of the first lens group G1 and the second lens group G2 becomes small, it means that the refractive power of the first lens group G1 becomes greater than that of the second lens group G2. This results in an image magnification of the combined system from the second lens group G2 onward at the telephoto end becoming too high, making it difficult to correct aberrations such as axial chromatic aberration at the telephoto end.

[0124] Furthermore, regarding conditional equation (18), it is preferable to set the lower limit to 0.7 and the upper limit to 1.8 to make the aforementioned effect more certain.

[0125] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (19) in order to achieve both a reduction in the overall length of the optical system and improved performance. (19) 1.0 <f1 / fW<5.0 f1: Focal length of the first lens group G1 fW: Focal length of the variable magnification imaging optical system at the wide-angle end at infinity.

[0126] Conditional equation (19) defines the ratio of the focal length of the variable magnification imaging optical system to the focal length of the first lens group G1 at the wide-angle end at infinity, and indicates a desirable range for achieving both a reduction in the overall length of the optical system and improved performance. By satisfying conditional equation (19), it is possible to achieve both a reduction in the overall length of the optical system and improved performance.

[0127] If the upper limit of condition (19) is exceeded and the focal length of the first lens group G1 becomes larger than the focal length of the variable magnification imaging optical system at the wide-angle end at infinity, the refractive power of the first lens group G1 becomes insufficient, making it difficult to shorten the overall length of the optical system, which is undesirable.

[0128] When the lower limit of condition (19) is exceeded, and the focal length of the first lens group G1 becomes smaller than the focal length of the variable magnification imaging optical system at the wide-angle end at infinity, the refractive power of the first lens group G1 becomes too strong, making it difficult to correct various aberrations such as spherical aberration and astigmatism, which hinders high performance and is undesirable.

[0129] Furthermore, regarding conditional equation (19), it is preferable to set the lower limit to 1.3 and the upper limit to 4.0 to make the aforementioned effect more certain.

[0130] Furthermore, in the variable magnification imaging optical system according to the present invention, it is desirable to satisfy the following condition (20) in order to achieve both a reduction in the overall length of the optical system and improved performance. (20) 0.5 <f2 / fW<8.5 f2: Focal length of the second lens group G2 fW: Focal length of the variable magnification imaging optical system at the wide-angle end at infinity.

[0131] Conditional equation (20) defines the ratio of the focal length of the variable magnification imaging optical system to the focal length of the second lens group G2 at the wide-angle end at infinity, and indicates a desirable range for achieving both a reduction in the overall length of the optical system and improved performance. By satisfying conditional equation (20), it is possible to achieve both a reduction in the overall length of the optical system and improved performance.

[0132] When the upper limit of condition (20) is exceeded and the focal length of the second lens group G1 becomes larger than the focal length of the variable magnification imaging optical system at the wide-angle end at infinity, the refractive power of the second lens group G2 becomes insufficient, making it difficult to shorten the overall length of the optical system. At the same time, it becomes necessary to compensate for the insufficient refractive power by strengthening the refractive power of the first lens group G1, which increases the aberrations generated in the first lens group G1, making it difficult to improve performance and is undesirable.

[0133] When the lower limit of condition (20) is exceeded, and the focal length of the second lens group G2 becomes smaller than the focal length of the variable magnification imaging optical system at the wide-angle end at infinity, the refractive power of the second lens group G2 becomes too strong, resulting in increased coma aberration and astigmatism in the second lens group, making it difficult to achieve high performance, which is undesirable.

[0134] Furthermore, regarding conditional equation (20), it is preferable to set the lower limit to 0.7 and the upper limit to 7.5 to make the aforementioned effect more reliable.

[0135] Furthermore, it is desirable that the variable magnification imaging optical system according to the present invention satisfies the following condition (21). (21) 0.04 < |fF / fT| < 0.35 fF: Focal length of the focusing group GF fT: Focal length of the variable magnification optical system at the telephoto end of infinity.

[0136] A shorter travel distance of the focusing group GF from infinity to the near end improves focusing speed, but this requires increasing the refractive power of the focusing group GF, which leads to a significant decrease in focusing performance and is undesirable. Taking this into consideration, condition (21) defines a desirable range for the absolute value of the ratio between the focal length of the focusing group GF and the focal length of the variable magnification imaging optical system at the infinity telephoto end, in order to increase focusing speed while suppressing the decrease in focusing performance. Satisfying condition (21) makes it possible to achieve high focusing speed while effectively correcting various aberrations.

[0137] When the lower limit of condition (21) is exceeded and the absolute value of the ratio of the focal length of the focusing group GF to the focal length of the variable magnification imaging optical system at the infinity telephoto end becomes small, the refractive power of the focusing group GF becomes too strong, and the performance fluctuations due to the deterioration of various aberrations during focusing become too large, which is undesirable.

[0138] When the upper limit of condition (21) is exceeded, and the absolute value of the ratio of the focal length of the focusing group GF to the focal length of the variable magnification imaging optical system at the infinity telephoto end becomes large, the refractive power of the focusing group GF becomes insufficient, and the amount of movement of the focusing group GF from infinity to the nearest end increases, which is undesirable as it leads to a decrease in focusing speed.

[0139] Furthermore, regarding conditional equation (21), it is preferable to set the lower limit to 0.06 and the upper limit to 0.20 to make the aforementioned effect more certain.

[0140] Furthermore, it is desirable that the variable magnification imaging optical system according to the present invention satisfies the following condition (22). (22)2.0<|{1-(βFT)^2}×(βRT)^2|<20.0 βFT: Horizontal magnification at the infinity telephoto end of the focusing group GF βRT: Horizontal magnification at infinity for all lens groups positioned on the image side of the focusing group GF.

[0141] Conditional equation (22) defines the absolute value of the focus sensitivity of the focusing group GF. Focus sensitivity is the ratio (ΔL / Δd) of the amount of movement Δd in the optical axis direction of the focusing group GF to the amount of movement ΔL in the optical axis direction of the image formation position due to the movement of the focusing group GF. The larger the absolute value of focus sensitivity, the greater the amount of movement of the image formation point in the optical axis direction that can be achieved with only a small amount of movement of the focusing group. By satisfying conditional equation (22), it is possible to achieve a faster focusing speed while effectively correcting various aberrations.

[0142] When the lower limit of condition equation (22) is exceeded and the absolute value of the focus sensitivity of the focusing group GF becomes small, the amount of movement of the focusing group GF increases during focusing, which is undesirable because it leads to a decrease in focusing speed.

[0143] If the upper limit of condition equation (22) is exceeded and the absolute value of the focus sensitivity of the focusing group GF becomes large, the refractive power of the focusing group GF becomes too strong, which is undesirable because it leads to excessive performance fluctuations due to the deterioration of various aberrations during focusing.

[0144] Furthermore, regarding conditional equation (22), it is possible to more reliably achieve the aforementioned effect by setting the lower limit to 2.5 and the upper limit to 15.0, and more preferably the lower limit to 3.0 and the upper limit to 12.5.

[0145] Furthermore, in the variable-magnification imaging optical system according to the present invention, the mechanism is kept fixed relative to the image plane during magnification, thereby preventing complexity. This is preferable because if a portion of the third lens group G3 is moved approximately perpendicular to the optical axis and used as an anti-vibration group, the drive unit and wiring do not move during magnification, thus simplifying the mechanism. Note that the position of the anti-vibration group is not necessarily limited to a portion of the third lens group G3. For example, a portion of the lens group on the image side of the aperture can be moved approximately perpendicularly and used as an anti-vibration group.

[0146] Furthermore, in the variable magnification imaging optical system according to the present invention, in order to prevent the mechanical mechanism from becoming more complex, it is desirable that the lens group closest to the image plane among the subsequent group GR be fixed to the image plane during zooming.

[0147] Next, the lens configuration of an embodiment of the imaging optical system of the present invention will be described, and specific numerical data will be shown. In the following description, the lens configuration will be described in order from the object side to the image side.

[0148] In the [Surface Data], the surface number is the number of the lens surface or aperture diaphragm S counted from the object side, r is the radius of curvature of each lens surface, d is the spacing between each lens surface, nd is the refractive index for the d line (wavelength 587.56 nm), vd is the Abbe number for the d line, and ΔPgF is a value calculated using the formula PgF - 0.64833 + 0.00180 × vd. Furthermore, the glass materials listed are examples of glass materials from HOYA Corporation, Ohara Corporation, and Hikari Glass Co., Ltd., as examples of glass corresponding to the refractive index, Abbe number, and ΔPgF listed in the [Surface Data].

[0149] The asterisk (*) next to the surface number indicates that the lens surface shape is aspherical. BF indicates the back focus, and the object surface distance indicates the distance from the subject to the first lens surface.

[0150] The (diaphragm) appended to the surface number indicates that an aperture diaphragm S is located at that position. The radius of curvature relative to the plane or aperture diaphragm S is indicated with ∞ (infinity).

[0151] The [Aspherical Data] section shows the values ​​of the coefficients that give the aspherical shape of the lens surface marked with an asterisk (*) in the [Surface Data] section. The shape of the aspherical surface is expressed by the following formula. In the following formula, y represents the displacement from the optical axis in the direction perpendicular to the optical axis, z represents the displacement (sag) in the direction of the optical axis from the intersection of the optical axis with the aspherical surface, r represents the radius of curvature of the reference sphere, and K represents the conic coefficient. The 4th, 6th, 8th, and 10th order aspherical coefficients are represented by A4, A6, A8, and A10, respectively. TIFF2026082399000002.tif26166

[0152] The [Various Data] section shows values ​​such as the zoom ratio and focal length at each shooting distance and focus state.

[0153] The [Variable Interval Data] section shows the variable interval and BF values ​​for each shooting distance focus state.

[0154] The [Lens Group Data] shows the object-side face number for each lens group and the combined focal length of the entire group.

[0155] Furthermore, in the aberration diagrams corresponding to each embodiment, d, g, and C represent the d line, g line, and C line, respectively, and ΔS and ΔM represent the sagittal image plane and meridional image plane, respectively.

[0156] In addition, for all the specifications listed below, the units of focal length f, radius of curvature r, lens plane spacing d, and other lengths are millimeters (mm) unless otherwise specified. However, since similar optical performance can be obtained in proportional magnification and proportional reduction in optical systems, this is not the only unit used.

[0157] Furthermore, the lenses will be designated as follows: the lens closest to the object will be L1, the second lens positioned towards the image will be L2, the third lens will be L3, and so on.

[0158] Furthermore, in the lens configuration diagrams of each embodiment, I is the image plane, F is the optical filter, and the dashed line passing through the center is the optical axis.

[0159] [Example 1] Figure 1 is a diagram of the lens configuration of the variable magnification imaging optical system according to Example 1 when it is focused at the wide-angle end and infinity.

[0160] The variable magnification imaging optical system in Figure 1 consists of, in order from the object side, an intermediate group GM comprising a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, and a fourth lens group G4; a focusing group GF comprising a fifth lens group G5 that moves along the optical axis when focusing from an object at infinity to an object at close range; and a subsequent group GR comprising a sixth lens group G6.

[0161] The first lens group G1 consists of a cemented lens of a concave meniscus lens L1 with its convex surface facing the object and a biconvex lens L2, and a convex meniscus lens L3 with its convex surface facing the object. The second lens group G2 consists of a cemented lens of a biconvex lens L4 and a concave meniscus lens L5 with its convex surface facing the image. The third lens group G3 consists of a cemented lens of a biconcave lens L6 and a convex meniscus lens L7 with its convex surface facing the object, a concave meniscus lens L8 with its convex surface facing the object, and a cemented lens of a biconcave lens L9 and a biconvex lens L10. In addition, it is possible to make lenses L8 to L10 of the third lens group G3 function as an anti-vibration group by moving them together in a direction approximately perpendicular to the optical axis, but lenses other than L8 to L10 may also be used as an anti-vibration group. The fourth lens group G4 consists of a biconvex lens L11, a cemented lens of biconvex lens L12 and biconcave lens L13, a biconvex lens L14, a cemented lens of biconcave lens L15 and biconvex lens L16, and an aperture diaphragm S. The fifth lens group G5 consists of a cemented lens of biconvex lens L17 and concave meniscus lens L18 with its convex surface facing the image side. The sixth lens group G6 consists of a convex meniscus lens L19 with its convex surface facing the image side, a biconcave lens L20, a cemented lens of biconvex lens L21 and biconcave lens L22, a cemented lens of convex meniscus lens L23 with its convex surface facing the image side and concave meniscus lens L24 with its convex surface facing the image side, and concave meniscus lens L25 with its convex surface facing the image side.

[0162] When changing magnification from the wide-angle end to the telephoto end, the third lens group G3 and the sixth lens group G6 are fixed relative to the image plane, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, the fourth lens group G4 moves toward the object, and the fifth lens group G5 moves toward the object and then moves toward the image. The distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 decreases, the distance between the fourth lens group G4 and the fifth lens group G5 increases, and the distance between the fifth lens group G5 and the sixth lens group G6 increases and then decreases. The distance becomes smaller at the telephoto end compared to the wide-angle end, and when focusing from an object at infinity to an object at close range, the fifth lens group G5 moves toward the object.

[0163] L18 is a concave lens that satisfies condition (1). L1 is a concave lens that satisfies condition (2). L5 is a concave lens that satisfies condition (11). L22 and L24 are concave lenses that satisfy condition (12). L22 and L24 are concave lenses that satisfy condition (13). L21 and L23 are convex lenses that satisfy condition (14). L21 and L23 are convex lenses that satisfy condition (15).

[0164] The specifications of the variable magnification imaging optical system according to Example 1 are shown below.

[0165] Numerical Example 1 Unit: mm [Surface data] Face number rd nd vd ΔPgF Applicable glass material Object surface ∞ (d0) 1 345.9465 3.0000 1.62205 41.09 -0.0051 S-NBM52 2 140.9130 10.5135 1.49700 81.61 0.0373 FCD1 3 -1128.2312 0.3000 4 134.8320 9.7064 1.43700 95.10 0.0564 FCD100 5 2787.0673 (d5) 6 264.3969 5.7045 1.74077 27.76 0.0093 E-FD13 7 -94.9663 1.7000 1.92286 20.88 0.0281 E-FDS1-W 8 -277.3703 (d8) 9 -265.8088 1.1000 1.90366 31.32 0.0027 TAFD25 10 42.3251 5.5864 1.80809 22.76 0.0212 FD225 11 375.1338 1.6610 12 2722.3332 1.0000 1.85150 40.78 -0.0055 S-LAH89 13 65.4454 3.7639 14 -38.2291 1.0000 1.76385 48.49 -0.0022 S-LAH96 15 96.7123 4.0500 1.85451 25.15 0.0071 NBFD25 16 -103.1166 (d16) 17 90.7216 4.2035 1.95375 32.32 -0.0002 TAFD45 18 -134.5523 0.3000 19 41.8225 8.0651 1.43700 95.10 0.0564 FCD100 20 -33.5158 3.1409 1.91082 35.25 -0.0017 TAFD35L 21 128.5130 2.0000 22 115.2168 5.3307 1.78880 28.43 0.0036 S-NBH58 23 -44.4459 0.3000 24 -178.6582 1.0000 1.85883 30.00 0.0035 NBFD30 25 29.2459 5.6004 1.43700 95.10 0.0564 FCD100 26 -159.6203 3.0000 27 (aperture) ∞ (d27) 28 58.2157 4.7813 1.76182 26.61 0.0117 FD140 29 -60.1979 0.8996 1.94594 17.98 0.0385 FDS18-W 30 -654.0263 (d30) 31 -76.3851 2.7042 1.85451 25.15 0.0071 NBFD25 32 -44.8928 2.0780 33 -50.6789 1.0000 1.76385 48.49 -0.0022 S-LAH96 34 51.3733 12.5744 35 52.4424 6.6039 1.61396 44.29 -0.0055 LAF45 36 -40.0023 1.0999 1.43700 95.10 0.0564 FCD100 37 98.2579 3.5590 38 -189.9223 5.2514 1.61396 44.29 -0.0055 LAF45 39 -27.1949 1.0001 1.59282 68.62 0.0192 FCD515 40 -123.8366 7.0234 41 -33.9240 1.0003 2.05090 26.94 0.0052 TAFD65 42 -53.1149 38.0000 43 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 44 ∞ (BF) Image plane ∞ [Various Data] Zoom ratio 3.78 Wide-angle, Medium, Telephoto Focal length 153.00 280.00 577.80 F-numbers: 5.16, 5.79, 6.48 Full angle of view 2ω 15.78 8.63 4.18 Image height Y 21.63 21.63 21.63 Lens length: 292.66 x 330.78 x 377.11 [Variable interval data] Focusing at infinity Wide-angle, Medium, Telephoto d0 ∞ ∞ ∞ d5 26.6891 66.7920 133.7564 d8 25.7840 23.7989 3.1654 d16 35.7986 19.5283 2.0000 d27 24.2472 39.1282 60.9559 d30 7.0431 8.4323 4.1330 BF 1.0000 1.0000 1.0000 When focusing on a short distance object Wide-angle, Medium, Telephoto d0 2500.0000 2500.0000 2500.0000 d5 26.6891 66.7920 133.7564 d8 25.7840 23.7989 3.1654 d16 35.7986 19.5283 2.0000 d27 22.0146 32.3613 37.0986 d30 9.2757 15.1992 27.9903 BF 1.0000 1.0000 1.0000 [Lens group data] Group Starting plane Focal length G1 1 226.88 G2 6 238.33 G3 9 -31.22 G4 17 59.67 G5 28 86.77 G6 31 -53.28

[0166] [Example 2] Figure 11 is a diagram of the lens configuration of the variable magnification imaging optical system according to Example 2 when it is focused at the wide-angle end and infinity.

[0167] The variable magnification imaging optical system in Figure 11 consists of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, an intermediate group GM consisting of the fourth lens group G4 and the fifth lens group G5, a focusing group GF consisting of the sixth lens group G6, and a subsequent group GR consisting of the seventh lens group G7.

[0168] The first lens group G1 consists of a biconvex lens L1 and a cemented lens of a biconvex lens L2 and a biconcave lens L3. The second lens group G2 consists of a cemented lens of a biconvex lens L4 and a concave meniscus lens L5 with its convex surface facing the image side. The third lens group G3 consists of a cemented lens of a biconcave lens L6 and a convex meniscus lens L7 with its convex surface facing the object side, a biconcave lens L8, and a cemented lens of a biconcave lens L9 and a biconvex lens L10. In addition, it is possible to make lenses L8 to L10 of the third lens group G3 function as an anti-vibration group by moving them together in a direction approximately perpendicular to the optical axis, but lenses other than L8 to L10 may also be used as the anti-vibration group. The fourth lens group G4 consists of a biconvex lens L11 and a cemented lens of a biconvex lens L12 and a biconcave lens L13. The fifth lens group G5 consists of a biconvex lens L14, a cemented lens of a biconcave lens L15 and a biconvex lens L16, and an aperture diaphragm S. The sixth lens group G6 consists of a cemented lens of a biconvex lens L17 and a concave meniscus lens L18 with its convex surface facing the image side. The seventh lens group G7 consists of a cemented lens of a convex meniscus lens L19 with its convex surface facing the image side and a biconcave lens L20, a cemented lens of a biconvex lens L21 and a concave meniscus lens L22 with its convex surface facing the image side, a cemented lens of a convex meniscus lens L23 with its convex surface facing the image side and a concave meniscus lens L24 with its convex surface facing the image side, and a cemented lens of a convex meniscus lens L25 with its convex surface facing the image side and a concave meniscus lens L26 with its convex surface facing the image side.

[0169] When changing magnification from the wide-angle end to the telephoto end, the third lens group G3 and the seventh lens group G7 are fixed relative to the image plane, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, the fourth lens group G4 and the fifth lens group G5 move toward the object, and the sixth lens group G6 moves toward the object and then toward the image. The distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 decreases, the distance between the fourth lens group G4 and the fifth lens group G5 decreases, the distance between the fifth lens group G5 and the sixth lens group G6 increases, and the distance between the sixth lens group G6 and the seventh lens group G7 increases and then decreases. The distance becomes smaller at the telephoto end compared to the wide-angle end, and when focusing from an object at infinity to an object at close range, the sixth lens group G6 moves toward the object.

[0170] L18 is a concave lens that satisfies condition (1). L3 is a concave lens that satisfies condition (2). L5 is a concave lens that satisfies condition (11). L22 and L24 are concave lenses that satisfy condition (12). L22 and L24 are concave lenses that satisfy condition (13). L21, L23, and L25 are convex lenses that satisfy condition (14). L23 and L25 are convex lenses that satisfy condition (15).

[0171] The specifications of the variable magnification imaging optical system according to Example 2 are shown below.

[0172] Numerical Example 2 Unit: mm [Surface data] Face number rd nd vd ΔPgF Applicable glass material Object surface ∞ (d0) 1 246.3262 8.0991 1.48749 70.44 0.0090 FC5 2 -521.9818 21.6806 3 113.3245 10.6205 1.49700 81.61 0.0373 FCD1 4 -1379.8535 3.0000 1.62205 41.09 -0.0051 S-NBM52 5 187.3779 (d5) 6 130.3929 8.0135 1.72825 28.32 0.0101 E-FD10L 7 -90.8458 1.7000 1.92286 20.88 0.0281 E-FDS1-W 8 -289.4240 (d8) 9 -342.1128 1.1871 1.90366 31.32 0.0027 TAFD25 10 61.1799 3.5455 1.80809 22.76 0.0212 FD225 11 289.8002 1.8879 12 -1350.9782 1.0000 1.91082 35.25 -0.0017 TAFD35L 13 64.7567 4.3236 14 -44.2797 1.0000 1.75500 52.32 -0.0069 TAC6 15 76.6115 3.8563 1.85451 25.15 0.0071 NBFD25 16 -174.2122 (d16) 17 213.6019 3.5839 1.76385 48.49 -0.0022 S-LAH96 18 -109.2397 0.3000 19 35.8827 7.5362 1.43700 95.10 0.0564 FCD100 20 -50.1883 1.0000 1.88300 40.81 -0.0094 TAFD30 21 394.3367 (d21) 22 103.0473 6.2284 1.84666 23.84 0.0145 FDS90-SGP 23 -76.3576 0.3000 24 -192.1579 1.0000 1.90366 31.32 0.0027 TAFD25 25 29.1129 5.8898 1.43700 95.10 0.0564 FCD100 26 -103.2647 3.0000 27 (aperture) ∞ (d27) 28 57.2282 6.6864 1.80000 29.84 0.0070 S-NBH55 29 -43.9330 0.8997 1.94594 17.98 0.0385 FDS18-W 30 -208.6497 (d30) 31 -73.3698 2.8737 1.85451 25.15 0.0071 NBFD25 32 -38.8116 1.0000 1.76385 48.49 -0.0022 S-LAH96 33 44.9874 11.0319 34 148.5616 6.5851 1.62205 41.09 -0.0051 S-NBM52 35 -29.4697 1.1001 1.43700 95.10 0.0564 FCD100 36 -43.0593 6.0350 37 -58.6201 3.0322 1.61340 44.27 -0.0054 S-NBM51 38 -36.6823 1.0000 1.59282 68.62 0.0192 FCD515 39 -353.4323 15.1583 40 -48.8049 3.1541 1.61340 44.27 -0.0054 S-NBM51 41 -33.4762 1.0002 1.76385 48.49 -0.0022 S-LAH96 42 -97.3460 38.0000 43 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 44 ∞ (BF) Image plane ∞ [Various data] Zoom ratio 3.78 Wide angle, intermediate, telephoto Focal length 153.00 280.00 577.80 F-number 5.15 5.79 6.47 Full picture angle 2ω 15.75 8.62 4.18 Image height Y 21.63 21.63 21.63 Overall lens length 285.59 334.99 385.59 [Variable interval data] When focused at infinity Wide angle, intermediate, telephoto d0 ∞ ∞ ∞ d 5 1.6589 54.4346 116.6097 d 8 20.2099 16.8330 5.2591 d 16 37.9067 21.5640 2.0000 d 21 3.3685 2.0000 2.9042 d 27 17.0854 34.4725 55.1218 d 30 5.5517 5.8757 3.8863<000091l2>BF 1.0000 1.0000 1.0000 When focused on a nearby object Wide angle, intermediate, telephoto d0 2500.0000 2500.0000 2500.0000 d 5 1.6589 54.4346 116.6097 d 8 20.2099 16.8330 5.2591 d 16 37.9067 21.5640 2.0000 d 21 3.3685 2.00o0 2.9042 [[ID=S8]]d 27 15.6470 30.0689 39.6710 d 30 6.9901 10.2793 19.3371 BF 1.0000 1.0000 1.0000 [Lens group data] Group Starting plane Focal length G1 1 248.94 G2 6 151.64 G3 9 -29.60 G4 17 77.56 G5 22 317.07 G6 28 66.20 G7 31 -42.39

[0173] [Example 3] Figure 21 is a diagram of the lens configuration of the variable magnification imaging optical system according to Example 3 when it is focused at the wide-angle end and infinity.

[0174] The variable magnification imaging optical system in Figure 21 consists of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, an intermediate group GM consisting of the fourth lens group G4, the fifth lens group G5, and the sixth lens group, a focusing group GF consisting of the seventh lens group G7, and a subsequent group GR consisting of the eighth lens group G8.

[0175] The first lens group G1 consists of a biconvex lens L1 and a cemented lens of a convex meniscus lens L2 with its convex surface facing the object and a concave meniscus lens L3 with its convex surface facing the object. The second lens group G2 consists of a biconvex lens L4 and a concave meniscus lens L5 with its convex surface facing the image. The third lens group G3 consists of a cemented lens of a biconcave lens L6 and a convex meniscus lens L7 with its convex surface facing the object, a biconcave lens L8, and a cemented lens of a biconcave lens L9 and a biconvex lens L10. In addition, it is possible to make lenses L8 to L10 of the third lens group G3 function as an anti-vibration group by moving them together in a direction approximately perpendicular to the optical axis, but lenses other than L8 to L10 may also be used as the anti-vibration group. The fourth lens group G4 consists of a biconvex lens L11 and a cemented lens of a biconvex lens L12 and a concave meniscus lens L13 with its convex surface facing the image. The fifth lens group G5 consists of a biconvex lens L14, a cemented lens of a biconcave lens L15 and a biconvex lens L16, and an aperture diaphragm S. The sixth lens group G6 consists of a cemented lens of a biconvex lens L17 and a concave meniscus lens L18 with its convex surface facing the image side. The seventh lens group G7 consists of a cemented lens of a convex meniscus lens L19 with its convex surface facing the image side and a biconcave lens L20. The eighth lens group G8 consists of a cemented lens of a biconvex lens L21 and a biconcave lens L22, a cemented lens of a biconvex lens L23 and a biconcave lens L24, a convex meniscus lens L25 with its convex surface facing the image side and a concave meniscus lens L26 with its convex surface facing the image side.

[0176] When changing magnification from the wide-angle end to the telephoto end, the third lens group G3, the seventh lens group G7, and the eighth lens group G8 are fixed relative to the image plane, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, the fourth lens group G4 and the fifth lens group G5 move toward the object, and the sixth lens group G6 moves toward the image. The distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 decreases, the distance between the fourth lens group G4 and the fifth lens group G5 decreases, the distance between the fifth lens group G5 and the sixth lens group G6 increases, and the distance between the sixth lens group G6 and the seventh lens group G7 decreases. When focusing from an object at infinity to an object at close range, the seventh lens group G7 moves toward the image.

[0177] L18 is a concave lens that satisfies condition (1). L3 is a concave lens that satisfies condition (2). L5 is a concave lens that satisfies condition (11). L22 and L24 are concave lenses that satisfy condition (12). L22 and L24 are concave lenses that satisfy condition (13). L21, L23, and L25 are convex lenses that satisfy condition (14). L23 and L25 are convex lenses that satisfy condition (15).

[0178] The specifications of the variable magnification imaging optical system according to Example 3 are shown below.

[0179] Numerical Example 3 Unit: mm [Surface data] Face number rd nd vd ΔPgF Applicable glass material Object surface ∞ (d0) 1 201.9201 8.5220 1.48749 70.44 0.0090 FC5 2 -620.3600 26.8056 3 98.5807 12.0000 1.45860 90.19 0.0491 FCD10A 4 17562.5671 3.0000 1.62205 41.09 -0.0051 S-NBM52 5 154.6697 (d5) 6 190.7861 7.9231 1.72825 28.32 0.0101 E-FD10L 7 -65.6159 1.7000 1.92286 20.88 0.0281 E-FDS1-W 8 -158.4359 (d8) 9 -153.6076 1.0000 1.90366 31.32 0.0027 TAFD25 10 47.0924 4.2886 1.80809 22.76 0.0212 FD225 11 3445.6155 1.9748 12 -195.3640 1.0000 1.91082 35.25 -0.0017 TAFD35L 13 83.9103 3.9323 14 -47.7254 1.0000 1.76385 48.49 -0.0022 S-LAH96 15 81.1278 4.0989 1.85451 25.15 0.0071 NBFD25 16 -119.4206 (d16) 17 146.5472 3.9267 1.71736 29.50 0.0087 E-FD1L 18 -101.7137 0.3000 19 46.3650 6.8510 1.43700 95.10 0.0564 FCD100 20 -46.9487 1.0000 1.91082 35.25 -0.0017 TAFD35L 21 -1334.2238 (d21) 22 111.7091 4.2741 1.84666 23.84 0.0145 FDS90-SGP 23 -77.0188 1.3107 24 -170.4019 1.0152 1.85451 25.15 0.0071 NBFD25 25 32.3336 4.9322 1.43700 95.10 0.0564 FCD100 26 -418.3874 3.0000 27 (aperture) ∞ (d27) 28 62.3581 6.9109 1.71736 29.50 0.0087 E-FD1L 29 -40.7604 0.8998 1.86966 20.02 0.0310 FDS20-W 30 -176.1068 (d30) 31 -1785.8064 4.2928 1.85451 25.15 0.0071 NBFD25 32 -34.5414 1.0000 1.80100 34.97 0.0009 S-LAM66 33 39.3006 (d33) 34 121.2362 7.1844 1.62205 41.09 -0.0051 S-NBM52 35 -29.5373 1.1000 1.43700 95.10 0.0564 FCD100 36 80.7540 1.0090 37 44.1021 7.9698 1.55298 55.07 -0.0046 J-KZFH4 38 -32.6885 1.0000 1.59282 68.62 0.0192 FCD515 39 133.6593 4.3775 40 -62.7216 3.6206 1.62205 41.09 -0.0051 S-NBM52 41 -32.9941 1.0000 1.85150 40.78 -0.0055 S-LAH89 42 -369.4182 38.0000 43 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 44 ∞ (BF) Image plane ∞ [Various Data] Zoom ratio 3.78 Wide-angle, Medium, Telephoto Focal length 153.00 280.00 577.80 F-numbers: 5.16, 5.79, 6.48 Full angle of view 2ω 15.84 8.64 4.18 Image height Y 21.63 21.63 21.63 Lens length: 293.09 x 334.25 x 383.09 [Variable interval data] Focusing at infinity Wide-angle, Medium, Telephoto d0 ∞ ∞ ∞ d5 8.8892 50.5572 111.4441 d8 15.7049 15.2045 3.1500 d16 38.7670 21.8715 2.0000 d21 4.2824 2.0000 2.0000 d27 6.3382 26.1318 49.9144 d30 7.8268 7.2111 3.3000 d33 25.5563 25.5565 25.5563 BF 1.0000 1.0000 1.0000 When focusing on a short distance object Wide-angle, Medium, Telephoto d0 2500.0000 2500.0000 2500.0000 d5 8.8892 50.5572 111.4441 d8 15.7049 15.2045 3.1500 d16 38.7670 21.8715 2.0000 d21 4.2824 2.0000 2.0000 d27 6.3382 26.1318 49.9144 d30 9.4866 12.5565 24.2853 d33 23.8965 20.2111 4.5710 BF 1.0000 1.0000 1.0000 [Lens group data] Group Starting plane Focal length G1 1 246.08 G2 6 151.03 G3 9 -30.96 G4 17 77.95 G5 22 438.00 G6 28 79.17 G7 31 -51.76 G8 34 627.68

[0180] [Example 4] Figure 31 is a diagram of the lens configuration of the variable magnification imaging optical system according to Example 4 when it is focused at the wide-angle end and infinity.

[0181] The variable magnification imaging optical system in Figure 31 consists of, in order from the object side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, an intermediate group GM consisting of the fourth lens group G4 and the fifth lens group G5, a focusing group GF consisting of the sixth lens group G6, and a subsequent group GR consisting of the seventh lens group G7.

[0182] The first lens group G1 consists of a biconvex lens L1 and a cemented lens of a convex meniscus lens L2 with its convex surface facing the object and a concave meniscus lens L3 with its convex surface facing the object. The second lens group G2 consists of a biconvex lens L4 and a cemented lens of a concave meniscus lens L5 with its convex surface facing the image. The third lens group G3 consists of a cemented lens of a biconcave lens L6 and a convex meniscus lens L7 with its convex surface facing the object, a concave meniscus lens L8 with its convex surface facing the object, and a cemented lens of a biconcave lens L9 and a biconvex lens L10. In addition, it is possible to make lenses L8 to L10 of the third lens group G3 function as an anti-vibration group by moving them together in a direction approximately perpendicular to the optical axis, but lenses other than L8 to L10 may also be used as the anti-vibration group. The fourth lens group G4 consists of a biconvex lens L11 and a cemented lens of a biconvex lens L12 and a biconcave lens L13. The fifth lens group G5 consists of a biconvex lens L14, a cemented lens of a concave meniscus lens L15 with its convex surface facing the object, a biconvex lens L16, and an aperture diaphragm S. The sixth lens group G6 consists of a cemented lens of a biconvex lens L17 and a concave meniscus lens L18 with its convex surface facing the image. The seventh lens group G7 consists of a cemented lens of a convex meniscus lens L19 with its convex surface facing the image and a biconcave lens L20, a cemented lens of a biconvex lens L21 and a concave meniscus lens L22 with its convex surface facing the image, a cemented lens of a convex meniscus lens L23 with its convex surface facing the image and a concave meniscus lens L24 with its convex surface facing the image, and a cemented lens of a convex meniscus lens L25 with its convex surface facing the image and a concave meniscus lens L26 with its convex surface facing the image.

[0183] When changing magnification from the wide-angle end to the telephoto end, the third lens group G3 and the seventh lens group G7 are fixed relative to the image plane, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, the fourth lens group G4 and the fifth lens group G5 move toward the object, and the sixth lens group G6 moves toward the object and then toward the image. The distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 decreases, the distance between the fourth lens group G4 and the fifth lens group G5 decreases, the distance between the fifth lens group G5 and the sixth lens group G6 increases, and the distance between the sixth lens group G6 and the seventh lens group G7 increases and then decreases. The distance becomes smaller at the telephoto end compared to the wide-angle end, and when focusing from an object at infinity to an object at close range, the sixth lens group G6 moves toward the object.

[0184] L18 is a concave lens that satisfies condition (1). L3 is a concave lens that satisfies condition (2). L5 is a concave lens that satisfies condition (11). L22 and L24 are concave lenses that satisfy condition (12). L22 and L24 are concave lenses that satisfy condition (13). L21, L23, and L25 are convex lenses that satisfy condition (14). L23 and L25 are convex lenses that satisfy condition (15).

[0185] The specifications of the variable magnification imaging optical system according to Example 4 are shown below.

[0186] Numerical Example 4 Unit: mm [Surface data] Face number rd nd vd ΔPgF Applicable glass material Object surface ∞ (d0) 1 185.6932 7.2164 1.55032 75.50 0.0274 FCD705 2 -439.8661 11.9991 3 75.9499 9.1160 1.49700 81.61 0.0373 FCD1 4 5766.0730 2.2991 1.62205 41.09 -0.0051 S-NBM52 5 113.1096 (d5) 6 105.3273 6.3716 1.72825 28.32 0.0101 E-FD10L 7 -87.5070 1.6991 1.92286 20.88 0.0281 E-FDS1-W 8 -273.7133 (d8) 9 -242.8108 1.0000 1.91082 35.25 -0.0017 TAFD35L 10 61.8013 2.9767 1.86966 20.02 0.0310 FDS20-W 11 215.8847 1.5480 12 228.6680 1.0000 1.85150 40.78 -0.0055 S-LAH89 13 38.4023 4.5618 14 -33.2288 1.0000 1.76385 48.49 -0.0022 S-LAH96 15 49.1151 3.7209 1.85451 25.15 0.0071 NBFD25 16 -188.4172 (d16) 17 139.8919 3.2365 1.91650 31.60 -0.0004 S-LAH88 18 -123.1233 0.3000 19 45.7865 5.9677 1.43700 95.10 0.0564 FCD100 20 -35.2881 1.0000 1.91082 35.25 -0.0017 TAFD35L 21 1068.9881 (d21) 22 77.5041 4.1047 1.80518 25.46 0.0131 FD60-W 23 -75.5322 0.3000 24 199.0936 1.0000 1.84666 23.84 0.0145 FDS90-SGP 25 26.9476 5.3854 1.43700 95.10 0.0564 FCD100 26 -102.8073 3.0000 27 (aperture) ∞ (d27) 28 48.3995 5.2831 1.68893 31.16 0.0066 E-FD8 29 -46.8058 0.8988 1.92286 20.88 0.0281 E-FDS1-W 30 -199.6440 (d30) 31 -124.7029 3.4402 1.90110 27.06 0.0074 NBFD27 32 -29.8333 1.0000 1.85150 40.78 -0.0055 S-LAH89 33 37.8096 5.5000 34 56.4605 6.9737 1.62205 41.09 -0.0051 S-NBM52 35 -21.2086 1.0994 1.43700 95.10 0.0564 FCD100 36 -653.8570 3.8992 37 -36.6025 3.0122 1.61340 44.27 -0.0054 S-NBM51 38 -26.0581 0.9993 1.59282 68.62 0.0192 FCD515 39 -132.0424 5.5510 40 -24.3024 4.7405 1.55298 55.07 -0.0046 J-KZFH4 41 -17.3134 0.9978 1.95375 32.32 -0.0002 TAFD45 42 -23.0109 35.8318 43 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 44 ∞ (BF) Image plane ∞ [Various Data] Zoom ratio 3.77 Wide-angle, Medium, Telephoto Focal length 102.80 188.00 388.00 F-number 4.99 6.07 6.46 Full angle of view 2ω 23.64 12.94 6.23 Image height Y 21.63 21.63 21.63 Lens length: 225.00 247.12 292.00 [Variable interval data] Focusing at infinity Wide-angle, Medium, Telephoto d0 ∞ ∞ ∞ d5 1.5000 24.1160 75.4942 d8 9.0000 8.5000 2.0058 d16 24.5388 8.0303 2.0000 d21 7.0308 5.2259 2.0000 d27 16.5176 27.1364 45.5207 d30 4.8830 12.5775 3.4494 BF 1.0000 1.0000 1.0000 When focusing on a short distance object Wide-angle, Medium, Telephoto d0 1680.0000 1680.0000 1680.0000 d5 1.5000 24.1160 75.4942 d8 9.0000 8.5000 2.0058 d16 24.5388 8.0303 2.0000 d21 7.0308 5.2259 2.0000 d27 15.1678 23.2492 30.8696 d30 6.2327 16.4647 18.1006 BF 1.0000 1.0000 1.0000 [Lens group data] Group Starting plane Focal length G1 1 177.94 G2 6 124.71 G3 9 -21.82 G4 17 94.01 G5 22 70.02 G6 28 72.18 G7 31 -50.84

[0187] [Example 5] Figure 41 is a diagram of the lens configuration of the variable magnification imaging optical system according to Example 5 when it is focused at the wide-angle end and infinity.

[0188] The variable magnification imaging optical system in Figure 41 consists, in order from the object side, of a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, an intermediate group GM consisting of a fourth lens group G4 and a fifth lens group G5, a focusing group GF consisting of a sixth lens group G6, and a subsequent group GR consisting of a seventh lens group G7.

[0189] The first lens group G1 consists of a biconvex lens L1, a convex meniscus lens L2 with its convex surface facing the object, and a cemented lens of a convex meniscus lens L3 with its convex surface facing the object and a concave meniscus lens L4 with its convex surface facing the object. The second lens group G2 consists of a biconvex lens L5 and a concave meniscus lens L6 with its convex surface facing the image. The third lens group G3 consists of a cemented lens of a biconcave lens L7 and a convex meniscus lens L8 with its convex surface facing the object, a biconcave lens L9, and a cemented lens of a biconcave lens L10 and a biconvex lens L11. In addition, it is possible to make lenses L9 to L11 of the third lens group G3 function as an anti-vibration group by moving them together in a direction approximately perpendicular to the optical axis, but lenses other than L9 to L11 may also be used as an anti-vibration group. The fourth lens group G4 consists of a biconvex lens L12 and a cemented lens of a biconvex lens L13 and a biconcave lens L14. The fifth lens group G5 consists of a biconvex lens L15, a cemented lens of a biconcave lens L16 and a biconvex lens L17, and an aperture diaphragm S. The sixth lens group G6 consists of a cemented lens of a biconvex lens L18 and a concave meniscus lens L19 with its convex surface facing the image side. The seventh lens group G7 consists of a cemented lens of a convex meniscus lens L20 with its convex surface facing the image side and a biconcave lens L21, a cemented lens of a biconvex lens L22 and a concave meniscus lens L23 with its convex surface facing the image side, a cemented lens of a convex meniscus lens L24 with its convex surface facing the image side and a biconcave lens L25, and a cemented lens of a convex meniscus lens L26 with its convex surface facing the image side and a concave meniscus lens L27 with its convex surface facing the image side.

[0190] When changing magnification from the wide-angle end to the telephoto end, the third lens group G3 and the seventh lens group G7 are fixed relative to the image plane, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, the fourth lens group G4 and the fifth lens group G5 move toward the object, and the sixth lens group G6 moves slightly toward the image. The distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 decreases, and the distance between the fourth lens group G4 and the fifth lens group G5 decreases and then increases, with the distance becoming larger at the telephoto end compared to the wide-angle end. The distance between the fifth lens group G5 and the sixth lens group G6 increases, and the distance between the sixth lens group G6 and the seventh lens group G7 decreases slightly. When focusing from an object at infinity to an object at close range, the sixth lens group G6 moves toward the object.

[0191] L19 is a concave lens that satisfies condition (1). L4 is a concave lens that satisfies condition (2). L6 is a concave lens that satisfies condition (11). L23 and L25 are concave lenses that satisfy condition (12). L23 and L25 are concave lenses that satisfy condition (13). L22, L24, and L26 are convex lenses that satisfy condition (14). L24 and L26 are convex lenses that satisfy condition (15).

[0192] The specifications of the variable magnification imaging optical system according to Example 5 are shown below.

[0193] Numerical Example 5 Unit: mm [Surface data] Face number rd nd vd ΔPgF Applicable glass material Object surface ∞ (d0) 1 337.1179 6.6999 1.49700 81.54 0.0358 S-FPL51 2 -581.8826 18.5972 3 235.7554 6.1028 1.43875 94.66 0.0560 S-FPL55 4 7101.9638 0.3000 5 93.9288 9.1859 1.49700 81.54 0.0358 S-FPL51 6 349.7573 3.0000 1.72047 34.71 -0.0025 S-NBH8 7 126.4244 (d7) 8 134.1399 7.5178 1.58144 40.89 0.0019 E-FL5 9 -148.8086 1.7000 1.80809 22.76 0.0212 FD225 10 -598.4548 (d10) 11 -342.8200 1.0000 1.85150 40.78 -0.0055 S-LAH89 12 46.2637 3.1531 1.86966 20.02 0.0310 FDS20-W 13 95.1303 2.9095 14 -219.2346 1.0000 1.76385 48.49 -0.0022 S-LAH96 15 72.6713 3.9865 16 -45.0373 1.0000 1.76385 48.49 -0.0022 S-LAH96 17 104.0425 3.9451 1.85451 25.15 0.0071 NBFD25 18 -99.8737 (d18) 19 173.0741 3.9090 1.83400 37.34 -0.0022 NBFD10 20 -94.4675 0.3000 21 41.0379 7.4740 1.43700 95.10 0.0564 FCD100 22 -41.7054 1.2500 1.91082 35.25 -0.0017 TAFD35L 23 12145.2652 (d23) 24 133.6881 4.8068 1.85451 25.15 0.0071 NBFD25 25 -65.7993 0.3000 26 -232.8929 1.0000 1.90366 31.32 0.0027 TAFD25 27 31.3191 5.2605 1.43700 95.10 0.0564 FCD100 28 -267.9501 3.0000 29 (aperture) ∞ (d29) 30 48.1447 5.1363 1.67270 32.17 0.0058 E-FD5 31 -42.8133 0.9001 1.94594 17.98 0.0385 FDS18-W 32 -123.1479 (d32) 33 -230.2065 3.8721 1.90110 27.06 0.0074 NBFD27 34 -32.6293 1.0000 1.79952 42.24 -0.0049 S-LAH52Q 35 39.3064 26.2619 36 56.4665 7.5034 1.61310 44.36 -0.0081 E-ADF10 37 -40.0385 1.1000 1.48071 85.29 0.0413 FCD915 38 -62.8720 2.0000 39 -89.0940 3.6057 1.65253 39.48 -0.0042 NBFD38 40 -38.5516 1.0000 1.59282 68.62 0.0192 FCD515 41 194.8441 2.5814 42 -63.7426 4.5130 1.61310 44.36 -0.0081 E-ADF10 43 -26.5259 1.0000 1.89190 37.13 -0.0035 S-LAH92 44 -203.6607 38.0000 45 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 46 ∞ (BF) Image plane ∞ [Various Data] Zoom ratio 3.78 Wide-angle, Medium, Telephoto Focal length 153.00 280.00 577.80 F-numbers: 5.16, 5.79, 6.48 Full angle of view 2ω 15.83 8.62 4.18 Image height Y 21.63 21.63 21.63 Lens length: 293.15 x 325.34 x 372.11 [Variable interval data] Focusing at infinity Wide-angle, Medium, Telephoto d0 ∞ ∞ ∞ d7 1.8002 33.1380 105.3427 d10 27.7342 28.5792 3.1500 d18 38.0563 22.3685 2.0000 d23 4.4466 3.1063 5.6350 d29 17.8727 35.4733 53.3131 d32 3.8724 3.3000 3.3000 BF 1.0001 1.0001 1.0001 When focusing on a short distance object Wide-angle, Medium, Telephoto d0 2500.0000 2500.0000 2500.0000 d7 1.8002 33.1380 105.3427 d10 27.7342 28.5792 3.1500 d18 38.0563 22.3685 2.0000 d23 4.4466 3.1063 5.6350 d29 16.4652 31.0973 38.1679 d32 5.2800 7.6760 18.4451 BF 1.0001 1.0001 1.0001 [Lens group data] Group Starting plane Focal length G1 1 216.36 G2 8 240.28 G3 11 -29.85 G4 19 70.36 G5 24 400.29 G6 30 65.84 G7 33 -39.48

[0194] [Example 6] Figure 51 is a diagram of the lens configuration of the variable magnification imaging optical system according to Example 6 when it is focused at the wide-angle end and infinity.

[0195] The variable magnification imaging optical system in Figure 51 consists, in order from the object side, of a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, an intermediate group GM consisting of a fourth lens group G4 and a fifth lens group G5, a focusing group GF consisting of a sixth lens group G6, and a subsequent group GR consisting of a seventh lens group G7.

[0196] The first lens group G1 consists of a biconvex lens L1 and a cemented lens of a biconvex lens L2 and a biconcave lens L3. The second lens group G2 consists of a cemented lens of a biconvex lens L4 and a concave meniscus lens L5 with its convex surface facing the image side. The third lens group G3 consists of a cemented lens of a biconcave lens L6 and a biconvex lens L7, a biconcave lens L8, and a cemented lens of a biconcave lens L9 and a biconvex lens L10. In addition, it is possible to make lenses L8 to L10 of the third lens group G3 function as an anti-vibration group by moving them together in a direction approximately perpendicular to the optical axis, but lenses other than L8 to L10 may also be used as the anti-vibration group. The fourth lens group G4 consists of a biconvex lens L11 and a cemented lens of a biconvex lens L12 and a biconcave lens L13. The fifth lens group G5 consists of a biconvex lens L14, a cemented lens of a biconcave lens L15 and a convex meniscus lens L16 with its convex surface facing the object, and an aperture diaphragm S. The sixth lens group G6 consists of a cemented lens of a biconvex lens L17 and a concave meniscus lens L18 with its convex surface facing the image. The seventh lens group G7 consists of a biconcave aspherical lens L19, which has aspherical surfaces on both the object side and the image side, a cemented lens of a biconvex lens L20 and a biconcave lens L21, a cemented lens of a biconvex lens L22 and a biconcave lens L23, a cemented lens of a biconvex lens L24 and a biconcave lens L25, a cemented lens of a biconvex lens L26 and a concave meniscus lens L27 with its convex surface facing the image, and a concave meniscus lens L28 with its convex surface facing the image.

[0197] When changing magnification from the wide-angle end to the telephoto end, the third lens group G3 and the seventh lens group G7 are fixed relative to the image plane, the first lens group G1 moves toward the object, the second lens group G2 moves toward the image, the fourth lens group G4 and the fifth lens group G5 move toward the object, and the sixth lens group G6 moves toward the object and then toward the image. The distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 decreases, the distance between the fourth lens group G4 and the fifth lens group G5 decreases, the distance between the fifth lens group G5 and the sixth lens group G6 increases, and the distance between the sixth lens group G6 and the seventh lens group G7 increases and then decreases. The distance becomes smaller at the telephoto end compared to the wide-angle end, and when focusing from an object at infinity to an object at close range, the sixth lens group G6 moves toward the object.

[0198] L18 is a concave lens that satisfies condition (1). L3 is a concave lens that satisfies condition (2). L5 is a concave lens that satisfies condition (11). L25 and L27 are concave lenses that satisfy condition (12). L25 and L27 are concave lenses that satisfy condition (13). L24 and L26 are convex lenses that satisfy condition (14). L24 and L26 are convex lenses that satisfy condition (15).

[0199] The specifications of the variable magnification imaging optical system according to Example 6 are shown below.

[0200] Numerical Example 6 Unit: mm [Surface data] Face number rd nd vd ΔPgF Applicable glass material Object surface ∞ (d0) 1 234.3304 8.7895 1.49700 81.61 0.0373 FCD1 2 -444.4309 16.4201 3 105.5481 11.2111 1.43700 95.10 0.0564 FCD100 4 -1051.9595 2.9998 1.62205 41.09 -0.0051 S-NBM52 5 215.8567 (d5) 6 204.3611 6.9940 1.69895 30.05 0.0084 E-FD15L 7 -143.7381 2.0999 1.92286 20.88 0.0281 E-FDS1-W 8 -613.6512 (d8) 9 -156.0722 1.0997 1.91082 35.25 -0.0017 TAFD35L 10 47.6583 4.1019 1.80809 22.76 0.0212 FD225 11 -5107.1670 1.8750 12 -216.7389 1.0000 1.90525 35.04 -0.0005 S-LAH93 13 61.9481 4.6451 14 -37.1044 1.0000 1.76385 48.49 -0.0022 S-LAH96 15 67.5560 4.5336 1.85451 25.15 0.0071 NBFD25 16 -80.7681 (d16) 17 263.5469 4.3751 1.72825 28.32 0.0101 E-FD10L 18 -55.0230 0.3000 19 48.4645 6.5294 1.43700 95.10 0.0564 FCD100 20 -36.8526 1.0494 1.91082 35.25 -0.0017 TAFD35L 21 1231.1199 (d21) 22 93.9243 4.3227 1.80610 33.27 -0.0001 NBFD15-W 23 -63.9916 0.5046 24 -213.9541 1.0000 1.85451 25.15 0.0071 NBFD25 25 38.3982 3.9687 1.43700 95.10 0.0564 FCD100 26 1803.9151 3.0405 27 (aperture) ∞ (d27) 28 52.0735 4.9684 1.67270 32.17 0.0058 E-FD5 29 -39.8030 0.8982 1.92286 20.88 0.0281 E-FDS1-W 30 -116.9564 (d30) 31* -494.4630 1.0000 1.85136 40.07 -0.0076 MC-TAFD315 32* 53.9214 2.4713 33 77.9286 5.8550 1.73037 32.23 -0.0005 NBFD32 34 -17.1696 0.9988 1.90525 35.04 -0.0005 S-LAH93 35 48.5723 1.6498 36 62.4617 6.3739 1.64769 33.84 0.0049 E-FD2 37 -18.6020 1.0995 1.69680 55.46 -0.0060 LAC14 38 118.0218 1.5231 39 65.7250 5.9379 1.61396 44.29 -0.0055 LAF45 40 -24.6783 1.0001 1.49700 81.61 0.0373 FCD1 41 72.8157 6.1659 42 46.9437 6.3940 1.61396 44.29 -0.0055 LAF45 43 -42.7103 1.1000 1.43700 95.10 0.0564 FCD100 44 -105.5770 5.5000 45 -36.7159 1.0000 2.05090 26.94 0.0052 TAFD65 46 -271.3804 38.0000 47 ∞ 2.5000 1.51680 64.20 0.0014 BSC7 48 ∞ (BF) Image plane ∞ [Aspherical data] Pages 31 and 32 K 0.00000 0.00000 A4 -5.41588E-06 -1.22981E-05 A6 7.90388E-08 6.46908E-08 A8 -2.58788E-10 -2.46765E-10 A10 2.86921E-13 0.00000E+00 [Various Data] Zoom ratio 6.29 Wide-angle, Medium, Telephoto Focal length 123.60 450.00 777.00 F-number 6.15 8.39 9.06 Full angle of view 2ω 19.78 5.38 3.11 Image height Y 21.63 21.63 21.63 Lens length: 292.27 x 344.49 x 388.89 [Variable interval data] Focusing at infinity Wide-angle, Medium, Telephoto d0 ∞ ∞ ∞ d5 2.5189 40.5047 120.7136 d8 25.2707 39.5006 3.6968 d16 42.4059 9.8506 2.0000 d21 10.6039 2.0000 1.9996 d27 17.0587 56.2957 69.1748 d30 7.1167 9.0388 4.0108 BF 1.0000 1.0000 1.0000 When focusing on a short distance object Wide-angle, Medium, Telephoto d0 2500.0000 2500.0000 3300.0000 d5 2.5189 40.5047 120.7136 d8 25.2707 39.5006 3.6968 d16 42.4059 9.8506 2.0000 d21 10.6039 2.0000 1.9996 d27 16.2689 47.8203 52.3102 d30 7.9065 17.5142 20.8754 BF 1.0000 1.0000 1.0000 [Lens group data] Group Starting plane Focal length G1 1 225.06 G2 6 297.27 G3 9 -27.86 G4 17 77.41 G5 22 156.54 G6 28 69.27 G7 31 -29.97

[0201] Furthermore, a list of the corresponding values ​​for the conditional expressions in each of these examples is shown.

[0202] [Conditional expression corresponding value] Condition Expression Number Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 (1) 0.038 0.038 0.031 0.028 0.038 0.028 (2) 1.622 1.622 1.622 1.622 1.720 1.622 (3) 0.1995 0.0142 0.0798 0.0199 0.0171 0.0209 (4) 8.146 3.843 4.986 4.487 8.805 6.836 (5) 1.035 0.082 0.566 0.167 0.065 0.100 (6) 42.26 22.17 35.38 37.64 33.44 32.65 (7) 1.89 1.78 1.85 1.64 1.92 2.17 (8) 0.77 0.73 0.71 0.68 0.77 0.61 (9) -0.69 -0.63 -0.58 -0.51 -0.77 -0.82 (10) 1.29 1.18 1.13 1.36 1.42 1.60 (11) 0.0281 0.0281 0.0281 0.0281 0.0212 0.0281 (12) 0.0564 0.0564 0.0564 0.0564 0.0413 0.0564 (13) 5.364 5.364 5.364 5.364 3.522 5.364 (14) -0.0055 -0.0054 -0.0051 -0.0054 -0.0081 -0.0055 (15) -0.0055 -0.0054 -0.0048 -0.0050 -0.0061 -0.0055 (16) 0.39 0.43 0.43 0.46 0.37 0.29 (17) 0.41 0.26 0.26 0.32 0.42 0.38 (18) 0.95 1.64 1.63 1.43 0.90 0.76 (19) 1.48 1.63 1.61 1.73 1.41 1.82 (20) 1.56 0.99 0.99 1.21 1.57 2.41 (21) 0.150 0.115 0.090 0.186 0.114 0.089 (22) 3.69 5.90 5.31 4.21 6.05 6.83

[0203] Furthermore, this technology can also take the following configuration. [Section 1] A variable-magnification imaging optical system comprising, in order from the object side, 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, an intermediate group GM consisting of one or more lens groups including an aperture diaphragm S, a focusing group GF, and a subsequent group GR consisting of one lens group, wherein the spacing between adjacent lens groups changes during magnification, and the focusing group GF moves along the optical axis when focusing from an object at infinity to an object at close range. [Section 2] The variable magnification imaging optical system according to item 1, characterized in that one or more concave lenses satisfying the following condition (1) are arranged between the aperture diaphragm S and the subsequent lens group GR. (1)ΔPgFLnSr>0.013 ΔPgFLnSr: Anomalous dispersion of the concave lens placed between the aperture diaphragm S and the subsequent lens group GR. [Section 3] The variable magnification imaging optical system according to [Item 1] or [Item 2], characterized in that when the magnification is changed from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. [Section 4] A variable-magnification imaging optical system according to any one of [Item 1] to [Item 3], characterized in that when the magnification is changed from the wide-angle end to the telephoto end, the second lens group G2 moves toward the image side, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases. [Section 5] The variable magnification imaging optical system according to any one of [Item 1] to [Item 4], characterized in that the first lens group G1 includes a concave lens that satisfies the following condition (2). (2) ndLN1 < 1.80 ndLN1: Refractive index of the concave lens with the highest refractive index included in the first lens group G1. [Section 6] A variable-magnification imaging optical system according to any one of [Item 1] to [Item 5], characterized in that it satisfies the following condition (3). (3) 0.005 <DG1G2W / DG1G2T<0.400 DG1G2W: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the wide-angle end at infinity. DG1G2T: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the infinity telephoto end. [Section 7] A variable-magnification imaging optical system according to any one of [Item 1] to [Item 6], characterized in that it satisfies the following condition (4). (4) 1.00 <DG2G3W / DG2G3T<80.00 DG2G3W: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end of infinity. DG2G3T: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end. [Section 8] A variable-magnification imaging optical system according to any one of [Item 1] to [Item 7], characterized in that it satisfies the following condition (5). (5) 0.01 <DG1G2W / DG2G3W<2.00 DG1G2W: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the wide-angle end at infinity. DG2G3W: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end of infinity. [Section 9] A variable-magnification imaging optical system according to any one of [Item 1] to [Item 8], characterized in that it satisfies the following condition (6). (6) 2.0 <DG1G2T / DG2G3T<200.0 DG1G2T: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the infinity telephoto end. DG2G3T: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end. [Section 10] A variable-magnification imaging optical system according to any one of [Item 1] to [Item 9], characterized in that it satisfies the following condition (7). (7) 1.2 <DG2Sw / DG2St<5.0 DG2Sw: Distance from the top of the lens face closest to the object in the second lens group G2 at the wide-angle end to the aperture diaphragm S. DG2St: Distance from the top of the lens face closest to the object in the second lens group G2 at the telephoto end to the aperture diaphragm S. [Section 11] The variable magnification imaging optical system according to any one of [Item 1] to [Item 10], characterized in that the second lens group G2 satisfies the following condition (8). (8) 0.2 <g2AXhW / g2AXhT<1.5 g2AXhW: Height of the axial marginal rays on the leading plane of the second lens group G2 at the wide-angle end at infinity with the aperture wide open. g2AXhT: Height of the axial marginal rays on the leading plane of the second lens group G2 at the telephoto end at infinity with the aperture wide open. [Section 12] The variable magnification imaging optical system according to any one of [Item 1] to [Item 11], characterized in that the second lens group G2 satisfies the following conditions (9) and (10). (9)-1.8<(g2OAhW / Wih)-(g2OAhT / Tih)<-0.3 (10) 0.6 < |g2OAhW / g2AXhT| < 2.5 With: Image height of the off-axis principal ray at the widest angle of view at infinity. Tih: Image height of the off-axis principal ray at the maximum field of view at the telephoto end of infinity. g2OAhW: Height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end of infinity. g2OAhT: Height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the infinity telephoto end. g2AXhT: Height of the axial marginal rays on the leading plane of the second lens group G2 at the telephoto end at infinity with the aperture wide open. [Section 13] The variable magnification imaging optical system according to any one of [Clause 1] to [Clause 12], characterized in that the second lens group G2 includes one or more concave lenses. [Section 14] The variable magnification imaging optical system according to any one of [Item 1] to [Item 13], characterized in that the second lens group G2 includes at least one concave lens that satisfies the following condition (11). (11)ΔPgFLg2>0.0090 ΔPgFLg2: Anomalous dispersion of the concave lens with the greatest anomalous dispersion among the concave lenses included in the second lens group G2. [Section 15] The variable magnification imaging optical system according to any one of [Item 1] to [Item 14], characterized in that the subsequent group GR includes at least one concave lens that satisfies the following condition (12). (12)ΔPgFnLr>0.009 ΔPgFnLr: Anomalous dispersion of concave lenses in the subsequent GR group [Section 16] The variable magnification imaging optical system according to any one of [Item 1] to [Item 15], characterized in that the subsequent group GR includes at least one concave lens that satisfies the following condition (13). (13)vdnLr×ΔPgFnLr>0.80 vdnLr: Abbe number of concave lenses included in the subsequent group GR ΔPgFnLr: Anomalous dispersion of concave lenses included in the subsequent group GR [Section 17] The variable magnification imaging optical system according to any one of [Item 1] to [Item 16], characterized in that the subsequent group GR includes at least one convex lens that satisfies the following condition (14). (14)ΔPgFpLr<-0.0010 ΔPgFpLr: Anomalous dispersion of convex lenses included in the subsequent group GR [Section 18] The variable-magnification imaging optical system according to any one of [Item 1] to [Item 17], characterized in that the two convex lenses counting from the image side satisfy the following condition (15). (15)ΔPgFprAVE<-0.0010 ΔPgFprAVE: Average value of the anomalous dispersion of the two convex lenses closest to the image. [Section 19] The variable magnification imaging optical system according to any one of [Item 1] to [Item 18], characterized in that the first lens group G1 satisfies the following condition (16). (16) 0.18 <f1 / fT<1.00 f1: Focal length of the first lens group G1 fT: Focal length of the variable magnification optical system at the telephoto end of infinity. [Section 20] The variable magnification imaging optical system according to any one of [Item 1] to [Item 19], characterized in that the second lens group G2 satisfies the following condition (17). (17) 0.1 <f2 / fT<1.4 f2: Focal length of the second lens group G2 fT: Focal length of the variable magnification optical system at the telephoto end of infinity. [Section 21] The variable magnification imaging optical system according to any one of [Item 1] to [Item 20], characterized in that the first lens group G1 and the second lens group G2 satisfy the following condition (18). (18) 0.6 <f1 / f2<2.2 f1: Focal length of the first lens group G1 f2: Focal length of the second lens group G2 [Section 22] A variable-magnification imaging optical system according to any one of [Item 1] to [Item 21], characterized in that it satisfies the following condition (19). (19) 1.0 <f1 / fW<5.0 f1: Focal length of the first lens group G1 fW: Focal length of the variable magnification imaging optical system at the wide-angle end at infinity. [Section 23] A variable-magnification imaging optical system according to any one of [Item 1] to [Item 22], characterized in that it satisfies the following condition (20). (20) 0.5 <f2 / fW<8.5 f2: Focal length of the second lens group G2 fW: Focal length of the variable magnification imaging optical system at the wide-angle end at infinity. [Section 24] The variable magnification imaging optical system according to any one of [Item 1] to [Item 23], characterized in that the focusing group GF satisfies the following condition (21). (21) 0.04 < |fF / fT| < 0.35 fF: Focal length of the focusing group GF fT: Focal length of the variable magnification optical system at the telephoto end of infinity. [Section 25] A variable magnification imaging optical system according to any one of [Item 1] to [Item 24], characterized in that it satisfies the following condition (22). (22)2.0<|{1-(βFT)^2}×(βRT)^2|<20.0 βFT: Horizontal magnification at the infinity telephoto end of the focusing group GF βRT: Horizontal magnification at infinity for all lens groups positioned on the image side of the focusing group GF. [Section 26] The variable magnification imaging optical system according to any one of [Item 1] to [Item 25], characterized in that the third lens group G3 is fixed with respect to the image plane during magnification. [Section 27] The variable-magnification imaging optical system according to any one of [Item 1] to [Item 26], characterized in that the subsequent group GR is fixed with respect to the image plane during magnification. [Explanation of symbols]

[0204] G1 First 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 GM intermediate group GF focusing group GR follow-up group S Aperture diaphragm F Optical Filter I image plane

Claims

1. A variable-magnification imaging optical system comprising, in order from the object side, 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, an intermediate group GM consisting of one or more lens groups including an aperture diaphragm S, a focusing group GF, and a subsequent group GR consisting of one lens group, wherein the spacing between adjacent lens groups changes during magnification, and the focusing group GF moves along the optical axis when focusing from an object at infinity to an object at close range.

2. The variable magnification imaging optical system according to claim 1, characterized in that one or more concave lenses satisfying the following condition (1) are arranged between the aperture diaphragm S and the subsequent lens group GR. (1) ΔPgFLnSr>0.013 ΔPgFLnSr: Anomalous dispersion of the concave lens placed between the aperture diaphragm S and the subsequent lens group GR.

3. The variable magnification imaging optical system according to claim 1, characterized in that when the magnification is changed from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases.

4. The variable magnification imaging optical system according to claim 1, characterized in that when the magnification is changed from the wide-angle end to the telephoto end, the second lens group G2 moves toward the image side, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 decreases.

5. The variable magnification imaging optical system according to claim 1, characterized in that the first lens group G1 includes a concave lens that satisfies the following condition (2). (2) ndLN1<1.80 ndLN1: Refractive index of the concave lens with the highest refractive index included in the first lens group G1

6. The variable magnification imaging optical system according to claim 1, characterized in that it satisfies the following condition (3). (3) 0.005<DG1G2W / DG1G2T<0.400 DG1G2W: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the wide-angle end at infinity. DG1G2T: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the infinity telephoto end.

7. The variable magnification imaging optical system according to claim 1, characterized in that it satisfies the following condition (4). (4) 1.00<DG2G3W / DG2G3T<80.00 DG2G3W: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end at infinity. DG2G3T: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end.

8. The variable magnification imaging optical system according to claim 1, characterized in that it satisfies the following condition (5). (5) 0.01<DG1G2W / DG2G3W<2.00 DG1G2W: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the wide-angle end at infinity. DG2G3W: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the wide-angle end at infinity.

9. The variable magnification imaging optical system according to claim 1, characterized in that it satisfies the following condition (6). (6) 2.0<DG1G2T / DG2G3T<200.0 DG1G2T: Distance on the optical axis between the first lens group G1 and the second lens group G2 at the infinity telephoto end. DG2G3T: The distance between the second lens group G2 and the third lens group G3 on the optical axis at the infinity telephoto end.

10. The variable magnification imaging optical system according to claim 1, characterized in that it satisfies the following condition (7). (7) 1.2<DG2Sw / DG2St<5.0 DG2Sw: Distance from the top of the lens face closest to the object in the second lens group G2 at the wide-angle end to the aperture diaphragm S. DG2St: Distance from the top of the lens face closest to the object in the second lens group G2 at the telephoto end to the aperture diaphragm S.

11. The variable magnification imaging optical system according to claim 1, characterized in that the second lens group G2 satisfies the following condition (8). (8) 0.2<g2AXhW / g2AXhT<1.5 g2AXhW: Height of the axial marginal rays on the leading plane of the second lens group G2 at the wide-angle end at infinity with the aperture wide open. g2AXhT: Height of the on-axial marginal rays on the leading plane of the second lens group G2 at the telephoto end at infinity with the aperture wide open.

12. The variable magnification imaging optical system according to claim 1, characterized in that the second lens group G2 satisfies the following conditions (9) and (10). (9) -1.8<(g2OAhW / Wih)-(g2OAhT / Tih)<-0.3 (10) 0.6<|g2OAhW / g2AXhT|<2.5 With: Image height of the off-axis principal rays at the widest angle of view at infinity. Tih: Image height of the off-axis principal rays at the maximum field of view at the telephoto end of infinity. g2OAhW: Height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the wide-angle end at infinity. g2OAhT: Height of the off-axis principal rays at the maximum angle of view on the leading surface of the second lens group G2 at the infinity telephoto end. g2AXhT: Height of the on-axial marginal rays on the leading plane of the second lens group G2 at the telephoto end at infinity with the aperture wide open.

13. The variable magnification imaging optical system according to claim 1, characterized in that the second lens group G2 includes one or more concave lenses.

14. The variable magnification imaging optical system according to claim 1, characterized in that the second lens group G2 includes at least one concave lens that satisfies the following condition (11). (11)ΔPgFLg2>0.0090 ΔPgFLg2: The anomalous dispersion of the concave lens with the greatest anomalous dispersion among the concave lenses included in the second lens group G2.

15. The variable magnification imaging optical system according to claim 1, characterized in that the subsequent group GR includes at least one concave lens that satisfies the following condition (12). (12)ΔPgFnLr>0.009 ΔPgFnLr: Anomalous dispersion of concave lenses in the subsequent GR group

16. The variable magnification imaging optical system according to claim 1, characterized in that the subsequent group GR includes at least one concave lens that satisfies the following condition (13). (13) vdnLr × ΔPgFnLr > 0.80 vdnLr: Abbe number of concave lenses included in the subsequent group GR ΔPgFnLr: Anomalous dispersion of concave lenses included in the subsequent group GR

17. The variable magnification imaging optical system according to claim 1, characterized in that the subsequent group GR includes at least one convex lens that satisfies the following condition (14). (14) ΔPgFpLr<-0.0010 ΔPgFpLr: Anomalous dispersion of convex lenses included in the subsequent group GR

18. The variable magnification imaging optical system according to claim 1, characterized in that the two convex lenses counting from the image side satisfy the following condition (15). (15)ΔPgFprAVE<-0.0010 ΔPgFprAVE: The average value of the anomalous dispersion of the two convex lenses closest to the image.

19. The variable magnification imaging optical system according to claim 1, characterized in that the first lens group G1 satisfies the following condition (16). (16) 0.18<f1 / fT<1.00 f1: Focal length of the first lens group G1 fT: Focal length of the variable magnification imaging optical system at the telephoto end of infinity.

20. The variable magnification imaging optical system according to claim 1, characterized in that the second lens group G2 satisfies the following condition (17). (17) 0.1<f2 / fT<1.4 f2: Focal length of the second lens group G2 fT: Focal length of the variable magnification imaging optical system at the telephoto end of infinity.

21. The variable magnification imaging optical system according to claim 1, characterized in that the first lens group G1 and the second lens group G2 satisfy the following conditional equation (18). (18) 0.6<f1 / f2<2.2 f1: Focal length of the first lens group G1 f2: Focal length of the second lens group G2

22. The variable magnification imaging optical system according to claim 1, characterized in that it satisfies the following conditional equation (19). (19) 1.0<f1 / fW<5.0 f1: Focal length of the first lens group G1 fW: Focal length of the variable magnification imaging optical system at the wide-angle end at infinity

23. The variable magnification imaging optical system according to claim 1, characterized in that it satisfies the following conditional equation (20). (20) 0.5<f2 / fW<8.5 f2: Focal length of the second lens group G2 fW: Focal length of the variable magnification imaging optical system at the wide-angle end at infinity

24. The variable magnification imaging optical system according to claim 1, characterized in that the focusing group GF satisfies the following condition (21). (21) 0.04<|fF / fT|<0.35 fF: Focal length of the focusing group GF fT: Focal length of the variable magnification imaging optical system at the telephoto end of infinity.

25. The variable magnification imaging optical system according to claim 1, characterized in that it satisfies the following conditional equation (22). (22) 2.0<|{1-(βFT)^2}×(βRT)^2|<20.0 βFT: Lateral magnification at the infinity telephoto end of the focusing group GF. βRT: Horizontal magnification at infinity for all lens groups positioned on the image side of the focusing group GF.

26. The variable magnification imaging optical system according to claim 1, characterized in that the third lens group G3 is fixed with respect to the image plane during magnification.

27. The variable magnification imaging optical system according to claim 1, characterized in that the subsequent group GR is fixed with respect to the image plane during magnification.

Images