Zoom lens and imaging apparatus

Abstract

To prevent a reduction in optical performance due to changes in temperature and humidity in a zoom lens including resin lenses.SOLUTION: A zoom lens includes: a first lens group L1 arranged on the side closest to the object; a positive intermediate lens group GP arranged on the closer side to an image than the first lens group; and two or more subsequent lens groups arranged on the closer side to the image than the intermediate lens group. The intermediate lens group includes a positive resin lens Pp and a negative resin lens Pn. An air lens between the positive resin lens and the negative resin lens has a negative refractive power. The subsequent lens groups include a negative focus lens group GF. When the focal length of the intermediate lens group is defined as fGP, and the focal length of the positive resin lens as fp, a condition of 0<fp / fGP≤1.95 is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a zoom lens suitable for imaging devices such as digital still cameras, video cameras, broadcast cameras, and surveillance cameras. [Background technology]

[0002] In order to realize a small-sized zoom lens with a large aperture and good correction of aberrations, it is preferable to arrange an aspherical lens with strong refractive power in a lens group near the aperture stop through which the diameter of the passing light beam is large. Also, in order to reduce the weight of the zoom lens, it is preferable to use a resin material as the lens material.

[0003] However, the shape and refractive index of resin lenses change significantly with temperature changes, which can easily cause fluctuations in the focal position and aberration. Patent Document 1 discloses a zoom lens in which a resin lens with positive refractive power and a resin lens with negative refractive power are arranged in the same lens group, so that fluctuations in the focal position and aberration caused by temperature changes are cancelled out between the resin lenses.

[0004] In addition, generally, high-dispersion resin materials have a high water absorption rate, and the shape and refractive index change significantly with changes in humidity. Therefore, when a high-dispersion material is used for a resin lens, such as the zoom lens of Patent Document 1, the fluctuations in the focus position and aberration due to moisture absorption are large, and it is necessary to suppress this. However, it takes a long time for the characteristics of a moisture-absorbed resin lens to stabilize, and the degree of moisture absorption varies from resin lens to resin lens, making it difficult to predict the fluctuations in the focus position and aberration due to changes in humidity, and it is difficult to cancel out the fluctuations between resin lenses. Patent Document 2 discloses a method of weakening the refractive power of a resin lens using a high-dispersion material as a method of suppressing the fluctuations in the focus position and aberration due to changes in humidity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-219655 A [Patent Document 2] Japanese Patent Application Publication No. 5-113537 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] However, when the refractive power of a resin lens having a high water absorption rate is weakened as in the method of Patent Document 2, the convergence and divergence of light rays is weakened, and the zoom lens becomes larger.

[0007] The present invention provides a small and lightweight zoom lens that uses resin lenses and is capable of suppressing degradation of optical performance due to changes in temperature and humidity. [Means for solving the problem]

[0008] A zoom lens according to another aspect of the present invention has a plurality of lens groups, and the distance between adjacent lens groups changes during zooming. The plurality of lens groups include a first lens group arranged closest to the object, an intermediate lens group arranged closer to the image side than the first lens group and having positive refractive power, and two or more subsequent lens groups arranged closer to the image side than the intermediate lens group. The intermediate lens group includes a positive resin lens with positive refractive power and a negative resin lens with negative refractive power. When the space between the positive resin lens and the negative resin lens is considered to be entirely air, the refractive power of an air lens formed between the positive resin lens and the negative resin lens is negative. The subsequent lens group includes a focus lens group that has negative refractive power and moves during focusing. When the focal length of the intermediate lens group is fGP and the focal length of the positive resin lens is fp, 0 <fp / fGP≦1.95 The present invention is characterized in that the above conditions are satisfied. An image pickup apparatus including the above zoom lens also constitutes another aspect of the present invention. Effect of the Invention

[0009] According to the present invention, in a small and lightweight zoom lens using a resin lens, degradation of optical performance due to changes in temperature and humidity can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a zoom lens according to a first embodiment. [Diagram 2] 5A to 5C are aberration diagrams of the zoom lens of Example 1 at the wide-angle end, at a middle zoom position, and at the telephoto end. [Diagram 3] FIG. 11 is a cross-sectional view of a zoom lens according to a second embodiment. [Figure 4] 10A to 10C are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Diagram 5] FIG. 11 is a cross-sectional view of a zoom lens according to a third embodiment. [Figure 6] 11A to 11C are aberration diagrams of the zoom lens of Example 3 at the wide-angle end, at a middle zoom position, and at the telephoto end. [Figure 7] FIG. 11 is a cross-sectional view of a zoom lens according to a fourth embodiment. [Figure 8] 11A to 11C are aberration diagrams of the zoom lens of Example 4 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 9] FIG. 13 is a cross-sectional view of a zoom lens according to a fifth embodiment. [Figure 10] 13A to 13C are aberration diagrams of the zoom lens of Example 5 at the wide-angle end, at a middle zoom position, and at the telephoto end. [Figure 11] FIG. 13 is a cross-sectional view of a zoom lens according to a sixth embodiment. [Figure 12] 13A to 13C are aberration diagrams of the zoom lens of Example 6 at the wide-angle end, at a middle zoom position, and at the telephoto end. [Figure 13] FIG. 13 is a cross-sectional view of a zoom lens according to a seventh embodiment. [Figure 14] 13A to 13C are aberration diagrams of the zoom lens of Example 7 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 15] FIG. 1 is a diagram showing an imaging device equipped with a zoom lens according to any one of the first to seventh embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, before describing specific embodiments 1 to 7, matters common to each embodiment will be described. The zoom lens of each embodiment is used as an imaging optical system in imaging devices such as digital still cameras, video cameras, broadcast cameras, and surveillance cameras.

[0012] 1, 3, 5, 7, 9, 11 and 13 respectively show the configuration of the zoom lenses of Examples 1 to 7 at the wide-angle end and in a state where the lens is focused on an object at infinity (hereinafter referred to as an infinity focused state). Li (i=1, 2, 3, ...) indicates the i-th lens group when counting from the object side (left side of the figure) to the image side (right side of the figure). SP indicates an aperture stop, and IP indicates an image plane. The imaging surface (light receiving surface) of an image sensor or the film surface (photosensitive surface) of a silver halide film is disposed on the image plane IP.

[0013] The zoom lens of each embodiment includes a first lens group L1 arranged closest to the object side, and a middle lens group GP with positive refractive power arranged closer to the image side than the first lens group L1. The middle lens group GP includes a plurality of lenses, and the resin lenses among the plurality of lenses are a resin lens (positive resin lens) Pp with positive refractive power and a resin lens (negative resin lens) Pn with negative refractive power. An air lens with negative refractive power is formed between the resin lenses Pp and Pn in the middle lens group GP. The refractive power of each resin lens and air lens is a paraxial refractive power.

[0014] Furthermore, the zoom lens of each embodiment has two or more subsequent lens groups arranged on the image side of the intermediate lens group GP. The subsequent lens groups include a focus lens group GF having negative refractive power and one or more lens groups on the image side of the focus lens group GF.

[0015] In a zoom lens, a lens group is a group of one or more lenses that move together when zooming between the wide-angle end and the telephoto end, or when adjusting the focus between an object at infinity and a close distance. In other words, the distance between adjacent lens groups changes when zooming or focusing. The lens group may include an aperture stop. The wide-angle end and the telephoto end respectively indicate the zoom states of the maximum angle of view (shortest focal length) and the minimum angle of view (maximum focal length) when the lens group that moves during zooming is located at both ends of the range that can be moved mechanically or controlled on the optical axis.

[0016] In each figure, the solid arrow indicates the movement locus of the lens group that moves during zooming from the wide-angle end to the telephoto end, and the dashed arrow indicates the movement direction of the focus lens group GF during focusing from an object at infinity to a close object.

[0017] The zoom lens of each embodiment is a large-aperture zoom lens including resin lenses Pp and Pn with strong refractive power in an intermediate lens group GP arranged near the aperture stop SP (adjacent to the aperture stop SP on the image side or including the aperture stop SP). The variation of the focal position of the entire system, spherical aberration, coma aberration, curvature of field, and other aberrations caused by the change in the shape and refractive power of the resin lenses Pp and Pn when the temperature changes are suppressed. Specifically, the change in the focal position and various aberrations is cancelled out between the resin lens Pp with positive refractive power and the resin lens Pn with negative refractive power. If the resin lenses Pp and Pn are arranged in different lens groups, the diameter and angle of the light beam passing through these lenses are significantly different between the resin lenses Pp and Pn. For this reason, it becomes difficult to cancel out the spherical aberration that is likely to occur at a position where the light beam diameter is wide and the curvature of field that is likely to occur at a position where the light beam angle is large between the resin lenses Pp and Pn. Therefore, in each embodiment, the resin lenses Pp, Pn are arranged in the same intermediate lens group GP, and the refractive power and shape of the resin lenses Pp, Pn are appropriately set, thereby effectively suppressing fluctuations in the focus position and various aberrations when the temperature changes.

[0018] In addition, the zoom lens of each embodiment also suppresses the variation of the focus position and various aberrations of the entire system caused by the change in the shape and the change characteristics of the refractive power due to moisture absorption of the resin lens made of a highly dispersive material with a strong refractive power. Specifically, the movement of the focus lens group GF, whose refractive power and arrangement are appropriately set, in the optical axis direction cancels out the changes in the focus position and various aberrations caused by the change in the shape and the refractive power due to moisture absorption. By matching the ratio of the amount of variation of the focus position and the amount of variation of the various aberrations caused by moisture absorption of the resin lens to the ratio of the amount of variation of the focus position and the amount of variation of the various aberrations caused by the movement of the focus lens group GF, it becomes possible to cancel out these variations regardless of the degree of moisture absorption. To achieve this, the arrangement and refractive power of the lens group GF are appropriately set according to the arrangement and refractive power of the resin lens Pn and the diameter and angle of the light beam passing through it. Positioning the focus lens group GF closer to the intermediate lens group GP than to a position such as the final lens group closest to the object, where the diameter and angle of the light rays passing through are significantly different from those of the plastic lens Pn, makes it possible to effectively suppress fluctuations in the focus position and various aberrations that occur when moisture is absorbed.

[0019] Furthermore, in the zoom lens of each embodiment, when the space between the resin lenses Pp and Pn is considered to be entirely air, the refractive power Φ of the air lens Pa formed between the resin lenses Pp and Pn is negative. Note that Φ is the refractive power on the paraxial line and is calculated by the following formula.

[0020] Φ=(1-ndp) / Rp-(1-ndn) / Rn +(1-ndp) (1-ndn) d / (Rp Rn) In the above formula, ndp and ndp are the refractive indices of the resin lenses Pp and Pn at the d-line, respectively. Rp is the radius of curvature of the lens surface Sp of the resin lens Pp that faces the resin lens Pn, and Rn is the radius of curvature of the lens surface Sn of the resin lens Pn that faces the resin lens Pp. d is the distance on the optical axis between the lens surfaces Sp and Sn.

[0021] The zoom lens of each embodiment satisfies the condition of the following formula (1), where the focal length of the entire intermediate lens group GP is fGP and the focal length of the resin lens Pp is fp. Note that each focal length is a paraxial focal length.

[0022] 0 <fp / fGP≦1.95 (1) The condition of formula (1) indicates an appropriate range of the ratio of the focal lengths of the intermediate lens group GP and the resin lens Pp so that the resin lens Pp has a sufficient light beam convergence effect. If the refractive power of the resin lens Pp is weakened so that fp / fGP exceeds the upper limit of formula (1), the light beam convergence effect is weakened and an additional lens is required to compensate for this. As a result, the zoom lens becomes large, which is undesirable. By setting the lower limit of formula (1) to 0, the refractive power of the intermediate lens group GP is limited to positive. In order to make the zoom lens compact, it is preferable to provide the lens group near the aperture stop SP with a convergence effect due to a positive refractive power.

[0023] It is more preferable to set the numerical range of formula (1) as follows:

[0024] 0.35≦fp / fGP≦1.85 (1a) It is more preferable to set the numerical range of formula (1) as follows:

[0025] 0.70≦fp / fGP≦1.75 (1b) By having the above configuration and satisfying the condition of formula (1), it is possible to realize a small, lightweight, large-aperture zoom lens that has an aspherical resin lens with strong refractive power in the intermediate lens group GP near the aperture stop SP, while being able to suppress degradation of optical performance due to changes in temperature and humidity.

[0026] The zoom lens of each embodiment preferably satisfies at least one of the conditions of the following expressions (2) to (9). Here, the focal length of the resin lens Pn is fn, the focal length at the telephoto end of the entire zoom lens system is ft, the focal length of the lens group GF is fGF, the F-number at the telephoto end of the entire zoom lens system is Ft, and the specific gravity of the resin lens Pp is ρp. In addition, the specific gravity of the resin lens Pn is ρn, the Abbe number of the resin lens Pn based on the d-line is νdn, and the refractive power of the air lens Pa between the resin lenses Pp and Pn is Φ.

[0027] -2.45≦fn / ft≦-0.10 (2) -1.20≦fn / fp≦-0.25 (3) -1.80≦(Rn+Rp) / (Rn-Rp)<0 (4) -1.90≦fGF / ft≦-0.40 (5) 1.00≦Ft≦5.60 (6) ρp≦1.70 and ρn≦1.70 (7) 15.00≦νdn≦40.00 (8) -2.30≦Φ·ft<0 (9) The condition of formula (2) indicates an appropriate range of the refractive power of the resin lens Pn in order to realize a compact zoom lens by the sufficient light beam convergence action of the resin lens Pn while suppressing the performance degradation caused by the change in temperature and humidity. If the refractive power of the resin lens Pn becomes too strong so that fn / ft exceeds the upper limit of formula (2), it is not preferable because it becomes difficult to suppress the fluctuation of the focus position and various aberrations caused by the change in temperature and humidity. If the refractive power of the resin lens Pn becomes weak so that fn / ft falls below the lower limit of formula (2), an additional lens is required due to the weakened light beam convergence action of the resin lens Pn, and the zoom lens becomes large, which is not preferable. The condition of formula (3) indicates an appropriate range of the focal length ratio of the resin lenses Pp, Pn so that the resin lenses Pp, Pn cancel out fluctuations in the focal position and various aberrations caused by changes in the shape and refractive power of the resin lenses Pp, Pn due to temperature changes. If the focal length ratio of the resin lenses Pp, Pn is far from -1 so that fn / fp exceeds the numerical range of formula (3), it becomes difficult for the resin lenses Pp, Pn to cancel out the above-mentioned fluctuations caused by temperature changes, which is not preferable.

[0028] The condition of formula (4) indicates the appropriate range of the shape of the air lens Pa to suppress the fluctuation of the focal position and various aberrations due to changes in temperature and humidity. If the radius of curvature of the lens surface Sn becomes larger than that of the lens surface Sp so that (Rn+Rp) / (Rn-Rp) exceeds the upper limit of formula (4), it is difficult for the resin lenses Pp, Pn to cancel out the temperature change caused by the temperature change, which is not preferable. If the radius of curvature of the lens surface Sn becomes smaller than that of the lens surface Sp so that (Rn+Rp) / (Rn-Rp) falls below the lower limit of formula (4), the above fluctuations when the resin lens Pn absorbs moisture become large, and it is difficult to suppress the fluctuations by moving the focus lens group GF, which is not preferable.

[0029] The condition of formula (5) is a condition for performing good imaging of objects from infinity to close distances while correcting the fluctuations in the focal position and various aberrations caused by changes in the shape and refractive power of the resin lens Pn due to moisture absorption by moving the focus lens group GF. This indicates an appropriate range of the ratio between the focal length of the focus lens group GF and the focal length of the entire zoom lens system. If the refractive power of the focus lens group GF becomes strong so that fGF / ft exceeds the upper limit of formula (5), the fluctuations in aberrations caused by the movement of the focus lens group GF become large, making it difficult to achieve good imaging performance for objects over the entire range from infinity to close distances, which is undesirable. If the refractive power of the focus lens group GF becomes weak so that fGF / ft falls below the lower limit of formula (5), the amount of movement of the focus lens group GF required to correct the above fluctuations due to moisture absorption increases, and the zoom lens becomes large, which is undesirable.

[0030] The condition of formula (6) indicates the appropriate range of the F-number at the telephoto end. When Ft satisfies the range of formula (6), a bright large-aperture zoom lens can be obtained.

[0031] The condition of formula (7) indicates the appropriate range of the specific gravity of the resin material of the resin lenses Pp and Pn. The specific gravity here is the ratio of the mass of the material at room temperature under the standard atmospheric pressure of 101.325 kPa to the mass of pure water at 4°C that has the same volume as the material. If ρp and ρn exceed the upper limit of formula (7), it becomes difficult to reduce the weight of the zoom lens, which is not preferable.

[0032] The condition of formula (8) indicates an appropriate range of the Abbe number of the resin material of the resin lens Pn. If the resin material is low-dispersion so that νdn exceeds the upper limit of formula (8), it becomes difficult to correct the chromatic aberration generated in the positive lens in the middle lens group GP, which is not preferable. If the resin material is high-dispersion so that νdn falls below the lower limit of formula (8), it becomes excessively corrected for chromatic aberration, which is not preferable.

[0033] The condition of formula (9) indicates the appropriate range of the product of the refractive power of the air lens Pa between the resin lenses Pp and Pn and the focal length of the entire system in order to suppress fluctuations in the focal position and various aberrations due to changes in temperature and humidity while realizing good optical performance. If the refractive power Φ of the air lens Pa becomes positive so that Φ·ft exceeds the upper limit of formula (9), it becomes difficult to simultaneously correct the spherical aberration and suppress the above-mentioned fluctuations when the temperature changes, which is not preferable. If the refractive power Φ of the air lens Pa becomes strongly negative so that Φ·ft falls below the lower limit of formula (9), it becomes difficult to simultaneously correct the spherical aberration and suppress the above-mentioned fluctuations when moisture is absorbed, which is not preferable.

[0034] It is more preferable that the numerical ranges of the formulas (2) to (9) are as follows:

[0035] -2.35≦fn / ft≦-0.20 (2a) -1.10≦fn / fp≦-0.35 (3a) -1.70≦(Rn+Rp) / (Rn-Rp)≦-0.15 (4a) -1.80≦fGF / ft≦-0.50 (5a) 1.20≦Ft≦5.00 (6a) 0.80≦ρp≦1.60 and 0.80≦ρn≦1.60 (7a) 17.25≦νdn≦35.00 (8a) -2.20≦Φ·ft≦-0.15 (9a) Moreover, it is more preferable that the numerical ranges of the formulas (2) to (9) are as follows:

[0036] -2.25≦fn / ft≦-0.30 (2b) -1.00≦fn / fp≦-0.45 (3b) -1.60≦(Rn+Rp) / (Rn-Rp)≦-0.25 (4b) -1.70≦fGF / ft≦-0.60 (5b) 1.80≦Ft≦4.50 (6b) 0.90≦ρp≦1.50 and 0.90≦ρn≦1.50 (7b) 20.00≦νdn≦30.00 (8b) -2.10≦Φ·ft≦-0.35 (9b) Examples 1 to 7 will be described in detail below, and Numerical Examples 1 to 7 corresponding to Examples 1 to 7 will be shown. In each Numerical Example, surface number i indicates the order of the surface from the object side. r is the radius of curvature of the i-th surface (mm), d is the lens thickness or air space (mm) on the optical axis between the i-th surface and the (i+1)-th surface. nd is the refractive index at the d-line of the optical material between the i-th surface and the (i+1)-th surface, and νd is the Abbe number based on the d-line of the optical material.

[0037] The Abbe number νd based on the d-line is expressed as νd=(Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the Fraunhofer d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm).

[0038] BF stands for back focus (mm). Back focus is the distance on the optical axis from the final surface of a zoom lens (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. The total lens length (mm) is the distance on the optical axis from the frontmost surface of a zoom lens (the lens surface closest to the object) to the final surface plus the back focus.

[0039] An "*" next to a surface number means that the surface is a lens surface with an aspheric shape. An aspheric shape is expressed by the following formula, where x is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in a direction perpendicular to the optical axis, the direction of light travel is positive, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, and A10 are aspheric coefficients. The conic constant and aspheric coefficient "eM" are expressed as x 10 -M means.

[0040] x=(h 2 / R) / [1+{1-(1+K)(h / R) 2}] 1 / 2 +A4×h 4 +A6×h 6 +A8×h 8 +A8×h 8 +A10×h 10 Moreover, the values ​​of the conditions of the above-mentioned expressions (1) to (9) in Numerical Examples 1 to 7 are summarized in Table 1.

[0041] Further, Fig. 2, Fig. 4, Fig. 6, Fig. 8, Fig. 10, Fig. 12 and Fig. 14 respectively show longitudinal aberrations (spherical aberration, astigmatism, distortion and chromatic aberration) of the zoom lenses of Numerical Examples 1 to 7 at (A) the wide-angle end, (B) the intermediate zoom position and (C) the telephoto end. In the spherical aberration diagrams, Fno indicates the F-number, the solid line indicates the spherical aberration for the d-line (wavelength 587.6 nm), and the two-dot chain line indicates the spherical aberration for the g-line (wavelength 435.8 nm). In the astigmatism diagrams, the solid line ΔS indicates the sagittal image plane and the dashed line ΔM indicates the meridional image plane. The distortion aberration is shown for the d-line. The chromatic aberration diagrams show the chromatic aberration of magnification at the g-line. ω is the half angle of view (°).

[0042] The zoom lenses of Examples (Numerical Examples) 1 to 3 shown in Figures 1, 3 and 5 are composed of, arranged in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 (GP) with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 (GF) with negative refractive power, and a sixth lens group L6 with positive refractive power. The third lens group L3 includes an aperture stop SP on the most object side.

[0043] In addition, in the first and third embodiments, the third lens group L3 as the intermediate lens group GP is composed of a positive lens, an aspherical resin lens Pp with positive refractive power, and an aspherical resin lens Pn with negative refractive power, which are arranged in this order from the object side to the image side. With this lens configuration, the aspherical lenses Pp and Pn arranged at a position where the light beam diameter is large can effectively correct spherical aberration and coma aberration. In addition, the strong refractive power of each lens allows the zoom lens to be made compact, while the influence of changes in the resin lenses Pp and Pn due to temperature changes is cancelled out between the resin lenses Pp and Pn, suppressing fluctuations in the focal position and various aberrations.

[0044] The fifth lens group L5 as the focus lens group GF is composed of one negative lens. With this lens configuration, the focus lens group GF can be made small and light, and the entire zoom lens can be made small and smooth focusing can be achieved. In the first and third embodiments, the focus lens group GF is disposed closer to the object side than the sixth lens group L6, which is the final lens group. With this lens configuration, the diameter and angle of the light passing through the focus lens group GF approach those of the plastic lens Pn, and the above-mentioned fluctuations due to moisture absorption of the plastic lens Pn can be well corrected by moving the focus lens group GF.

[0045] In the second embodiment, the third lens group L3 as the intermediate lens group GP is composed of an aspherical resin lens Pp with positive refractive power, a positive lens, and an aspherical resin lens Pn with negative refractive power, which are arranged in this order from the object side to the image side. Unlike the third lens group L3 in the first and third embodiments, a glass lens is arranged between the resin lenses Pp and Pn. By appropriately setting the shape of the air lens Pa between the resin lenses Pp and Pn, the same effect as in the first and third embodiments can be obtained. The lens configuration of the fifth lens group L5 as the focus lens group GF is the same as in the first and third embodiments.

[0046] 7 is composed of a first lens group L1 having a positive refractive power, a second lens group L2 having a negative refractive power, a third lens group L3 (GP) having a positive refractive power, a fourth lens group L4 (GF) having a negative refractive power, and a fifth lens group L5 having a positive refractive power, arranged in this order from the object side to the image side. The third lens group L3 includes an aperture stop SP on the most object side thereof.

[0047] In the fourth embodiment, the third lens group L3 as the intermediate lens group GP is composed of a positive lens, an aspherical resin lens Pp having a positive refractive power, an aspherical resin lens Pn having a negative refractive power, a positive lens, a negative lens, and a positive lens, which are arranged in this order from the object side to the image side. Although the lens configuration is different from that of the third lens group L3 in the first and third embodiments, by appropriately setting the shape of the air lens Pa between the resin lenses Pp and Pn, it is possible to suppress the fluctuation of the focus position and various aberrations due to temperature changes, as in the first and third embodiments. The lens configuration of the fourth lens group GF as the focus lens group GF is the same as that of the fifth lens group L5 in the first to third embodiments.

[0048] 9 is composed of a first lens group L1 having a negative refractive power, a second lens group L2 (GP) having a positive refractive power, a third lens group L3 having a positive refractive power, a fourth lens group L4 (GF) having a negative refractive power, and a fifth lens group L5 having a positive refractive power, arranged in this order from the object side to the image side. The second lens group L2 includes an aperture stop SP on the most object side thereof.

[0049] The lens configuration of the second lens group L2 as the intermediate lens group GP in Example 5 is composed of, in order from the object side to the image side, a cemented lens of a positive lens and a negative lens, an aspherical resin lens Pp having a positive refractive power, and an aspherical resin lens Pn having a negative refractive power. The lens configuration of the fourth lens group L4 as the focus lens group GF is the same as that of the fifth lens group L5 in Examples 1 to 3.

[0050] 11, the zoom lens of Example 6 includes, in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 (GP) with positive refractive power, a third lens group L3 (GF) with negative refractive power, and a fourth lens group L4 with positive refractive power. The second lens group L2 includes an aperture stop SP on the most object side.

[0051] The lens configuration of the second lens group L2 serving as the intermediate lens group GP in Example 6 is similar to that of the third lens group L3 in Example 4. The lens configuration of the third lens group L3 serving as the focus lens group GF is similar to that of the fifth lens group L5 in Examples 1 to 3.

[0052] 13, the zoom lens of Example 7 is composed of, arranged in order from the object side to the image side, a first lens group L1 with positive refractive power, a second lens group L2 with negative refractive power, a third lens group L3 (GP) with positive refractive power, a fourth lens group L4 with positive refractive power, a fifth lens group L5 (GF) with negative refractive power, and a sixth lens group L6 with negative refractive power. The third lens group L3 includes an aperture stop SP on the most object side thereof.

[0053] In Example 7, the third lens group L3 as the intermediate lens group GP is composed of a positive lens, an aspherical resin lens Pn with negative refractive power, and an aspherical resin lens Pp with positive refractive power, which are arranged in this order from the object side to the image side. Unlike the third lens group L3 in Examples 1 and 3, the power arrangement of the resin lenses is reversed, but by appropriately setting the shape of the air lens Pa between the resin lenses Pn and Pp, the same effect as in Examples 1 and 3 can be obtained. The lens configuration of the fifth lens group L5 as the focus lens group GF is the same as in Examples 1 to 3.

[0054] In each of the above embodiments, by arranging an aspherical lens in a lens group through which the diameter of the light beam passing through is large, spherical aberration and coma aberration are well corrected, and the zoom lens is made compact and has a large aperture. In addition, by using a resin material for the aspherical lens, the zoom lens is made lighter. Furthermore, by arranging two resin lenses Pp and Pn in the same lens group, the diameter and angle of the light beam passing through the resin lenses Pp and Pn are close to each other. This allows the resin lenses Pp and Pn to cancel out fluctuations in the focus position and various aberrations caused by temperature changes.

[0055] In addition, chromatic aberration is effectively corrected by using a high-dispersion material for the resin lens Pn. Fluctuations in the focus position and various aberrations that occur when moisture is absorbed, which is an issue with high-dispersion materials, are cancelled out by the movement of the focus lens group GF. By making the refractive power of the focus lens group GF negative and bringing the diameter and angle of the light rays passing through the focus lens group GF closer to those of the resin lens Pn, the above fluctuations caused by changes in the resin lens Pn when moisture is absorbed are effectively corrected. [Numerical example 1] Unit: mm Surface Data Surface number rd nd νd 1 79.989 2.00 1.80810 22.8 2 65.410 7.49 1.72916 54.7 3 506.830 (variable) 4 87.802 1.40 1.77250 49.6 5 19.211 8.83 6 -55.299 1.20 1.59282 68.6 7 22.961 0.30 8 23.982 4.46 2.00069 25.5 9 109.654 6.87 10 -27.491 1.20 1.69895 30.1 11 -37.687 (variable) 12 (Aperture) ∞ 1.00 13 38.862 3.67 1.49700 81.5 14 -197.027 0.30 15* 36.306 3.92 1.53110 55.9 16* 93944.273 6.98 17* -32.592 1.20 1.63550 23.9 18* -6377.998 (variable) 19 29.494 7.13 1.49700 81.5 20 -37.021 0.20 21* 108.899 2.80 1.58313 59.4 22* -70.469 (variable) 23 316.449 1.40 1.77047 29.7 24 31.627 (variable) 25 -760.657 1.20 1.77047 29.7 26 29.630 7.68 1.89286 20.4 27 -1261.259 (variable) Image plane ∞ Aspheric Data Page 15 K = 0.00000e+00 A4= 2.82566e-06 A6= 2.27809e-08 A8=-4.41573e-10 A10=-1.69132e-13 Page 16 K = 0.00000e+00 A4=-2.24408e-06 A6= 1.92276e-08 A8=-1.01596e-09 A10 = 2.17482e-12 Page 17 K = 0.00000e+00 A4=-2.91532e-05 A6= 2.28516e-07 A8=-2.70941e-09 A10= 1.19387e-11 Side 18 K = 0.00000e+00 A4=-1.67625e-05 A6= 2.08851e-07 A8=-1.74802e-09 A10= 7.42786e-12 Page 21 K = 0.00000e+00 A4=-1.68719e-05 A6=-7.68292e-08 A8= 7.43758e-10 A10=-6.54672e-13 Page 22 K = 0.00000e+00 A4= 8.36618e-06 A6=-4.99678e-08 A8= 7.03081e-10 A10=-2.66968e-13 Various data Zoom ratio 1.98 Wide Angle Mid-Telephoto Focal length 24.70 36.56 48.80 F-number 2.90 2.90 2.90 Half angle of view (°) 37.93 30.17 23.91 Image height 19.25 21.25 21.64 Lens length 127.00 135.58 146.40 BF 19.97 25.52 29.15 Focused at infinity d 3 0.85 10.97 20.57 d11 15.19 6.78 2.22 d18 6.60 4.15 3.07 d22 2.42 2.00 2.00 d24 10.74 14.93 18.14 d27 19.97 25.52 29.15 Lens Group Data Group starting plane focal length 1 1 132.59 2 4 -21.86 3 12 62.27 4 19 24.30 5 23 -45.71 6 25 261.78 Single lens data Lens starting surface focal length 1 1 -473.12 2 2 102.27 3 4 -32.12 4 6 -27.21 5 8 29.90 6 10 -152.77 7 13 65.65 8 15 68.38 9 17 -51.55 10 19 34.25 11 21 73.79 12 23 -45.71 13 25 -36.99 14 26 32.51 [Numerical example 2] Unit: mm Surface Data Surface number rd nd νd 1 86.676 2.00 1.80810 22.8 2 71.189 6.65 1.72916 54.7 3 605.239 (variable) 4 73.570 1.40 1.77250 49.6 5 19.593 9.41 6 -57.278 1.20 1.59282 68.6 7 25.364 0.30 8 25.888 4.42 2.00069 25.5 9 114.296 7.42 10 -27.338 1.20 1.69895 30.1 11 -37.963 (variable) 12 (Aperture) ∞ 1.00 13* 31.119 4.46 1.53110 55.9 14* 95732.963 0.30 15 41.863 3.45 1.49700 81.5 16 -2313.475 7.08 17* -32.609 1.20 1.63550 23.9 18* -7728.688 (variable) 19 30.206 7.59 1.49700 81.5 20 -35.211 0.20 21* 51.306 2.80 1.58313 59.4 22* -328.247 (variable) 23 123.918 1.40 1.77047 29.7 24 28.207 (variable) 25 -278.220 1.20 1.77047 29.7 26 27.746 8.41 1.89286 20.4 27 -2028.233 (variable) Image plane ∞ Aspheric Data Page 13 K = 0.00000e+00 A4= 9.75109e-07 A6=-2.47430e-09 A8= 2.27842e-11 A10=-2.00675e-12 Side 14 K = 0.00000e+00 A4=-1.00949e-06 A6=-3.96522e-09 A8=-1.12328e-10 A10=-1.68078e-12 Page 17 K = 0.00000e+00 A4=-1.96647e-05 A6= 2.80336e-07 A8=-2.57774e-09 A10= 8.63812e-12 Side 18 K = 0.00000e+00 A4=-8.36532e-06 A6= 2.70558e-07 A8=-2.20902e-09 A10= 7.29764e-12 Page 21 K = 0.00000e+00 A4=-8.50964e-06 A6=-4.77167e-08 A8=-1.00397e-10 A10=-3.96226e-13 Page 22 K = 0.00000e+00 A4= 1.50082e-05 A6=-3.35489e-08 A8=-9.31220e-11 A10=-1.77216e-13 Various data Zoom ratio 1.98 Wide Angle Mid-Telephoto Focal length 24.70 35.97 48.80 F-number 2.90 2.90 2.90 Half angle of view (°) 38.21 30.81 23.91 Image height 19.44 21.45 21.64 Lens length 127.00 135.22 145.57 BF 17.03 23.57 29.81 Focused at infinity d 3 0.85 11.22 19.94 d11 15.74 7.39 2.18 d18 6.30 4.04 2.79 d22 2.98 2.36 2.00 d24 11.02 13.55 15.77 d27 17.03 23.57 29.81 Lens Group Data Group starting plane focal length 1 1 141.41 2 4 -22.99 3 12 65.34 4 19 24.25 5 23 -47.70 6 25 478.94 Single lens data Lens starting surface focal length 1 1 -523.26 2 2 110.07 3 4 -34.96 4 6 -29.49 5 8 32.63 6 10 -146.55 7 13 58.61 8 15 82.78 9 17 -51.53 10 19 34.02 11 21 76.30 12 23 -47.70 13 25 -32.69 14 26 30.71 [Numerical example 3] Unit: mm Surface Data Surface number rd nd νd 1 80.700 2.00 1.80810 22.8 2 73.040 7.23 1.72916 54.7 3 917.549 (variable) 4 131.215 1.40 1.77250 49.6 5 23.076 8.38 6 -83.289 1.20 1.59282 68.6 7 23.213 0.30 8 24.679 4.64 2.00069 25.5 9 74.871 5.81 10 -32.618 1.20 1.69895 30.1 11 -49.761 (variable) 12 (Aperture) ∞ 1.00 13 29.251 5.95 1.49700 81.5 14 284.450 0.30 15* 39.714 4.86 1.53110 55.9 16*∞7.57 17* -37.442 1.20 1.63550 23.9 18* 27207.661 (variable) 19 30.896 7.01 1.49700 81.5 20 -49.006 0.30 21 -95.754 1.20 1.54072 47.2 22 126.902 0.98 23* 101.129 2.80 1.58313 59.4 24* -82.213 (variable) 25 146.739 1.40 1.77047 29.7 26 47.346 (variable) 27 579.837 1.20 1.77047 29.7 28 34.148 8.13 1.89286 20.4 29 -1261.259 (variable) Image plane ∞ Aspheric Data Page 15 K = 0.00000e+00 A4=-5.66251e-07 A6=-5.06782e-09 A8= 6.07693e-11 A10=-8.72090e-14 Page 16 K = 0.00000e+00 A4=-1.23985e-06 A6=-2.06146e-08 A8= 7.57254e-11 A10=-2.40531e-13 Page 17 K = 0.00000e+00 A4=-2.35956e-05 A6= 1.37872e-07 A8=-5.35615e-10 A10 = 5.08486e-13 Side 18 K = 0.00000e+00 A4=-1.59876e-05 A6= 1.45363e-07 A8=-5.08230e-10 A10= 7.78772e-13 Page 23 K = 0.00000e+00 A4=-1.08712e-05 A6=-2.37564e-08 A8= 2.64645e-10 A10 = 2.50409e-13 Page 24 K = 0.00000e+00 A4= 9.61654e-06 A6=-1.71080e-09 A8= 1.87603e-10 A10= 5.53953e-13 Various data Zoom ratio 2.75 Wide Angle Mid-Telephoto Focal length 24.70 45.00 67.90 F-number 2.90 2.90 2.90 Half angle of view (°) 37.63 25.68 17.67 Image height 19.04 21.64 21.64 Lens length 141.13 155.45 173.50 BF 13.00 24.93 31.83 Focused at infinity d 3 0.85 14.77 26.05 d11 25.04 11.12 4.82 d18 7.25 3.62 2.00 d24 8.39 3.70 2.00 d26 10.54 21.26 30.75 d29 13.00 24.93 31.83 Lens Group Data Group starting plane focal length 1 1 122.12 2 4 -22.45 3 12 58.58 4 19 36.29 5 25 -91.28 6 27 178.51 Single lens data Lens starting surface focal length 1 1 -1078.17 2 2 108.44 3 4 -36.45 4 6 -30.49 5 8 35.16 6 10 -139.48 7 13 65.10 8 15 74.78 9 17 -58.84 10 19 39.27 11 21 -100.74 12 23 78.21 13 25 -91.28 14 27 -47.14 15 28 37.35 [Numerical example 4] Unit: mm Surface Data Surface number rd nd νd 1 616.910 2.00 1.57501 41.5 2 75.207 9.01 1.49700 81.5 3 232.616 0.20 4 124.192 6.17 1.88300 40.8 5 2120.493 (variable) 6 85.284 1.40 1.88300 40.8 7 26.925 13.02 8 -98.869 1.20 1.51742 52.4 9 29.169 0.30 10 30.569 8.01 1.90200 25.1 11 205.366 7.65 12 -43.983 1.20 1.56873 63.1 13 -72.869 (variable) 14(Aperture) ∞ 1.00 15 53.525 4.80 1.49700 81.5 16 -105.021 1.00 17* 33.005 4.56 1.53110 55.9 18* 284.168 10.08 19* -134.760 1.70 1.63550 23.9 20* 31.358 8.15 21 47.465 6.01 1.49700 81.5 22 -25.161 4.00 23 -29.043 1.20 1.49700 81.5 24 -228.771 0.20 25* 81.445 2.80 1.58313 59.4 26* -518.657 (variable) 27 -141.649 1.40 1.77047 29.7 28 97.978 (variable) 29 134.255 1.20 1.77047 29.7 30 38.025 9.97 1.89286 20.4 31 -1261.259 (variable) Image plane ∞ Aspheric Data Page 17 K = 0.00000e+00 A4=-4.71933e-06 A6=-7.49466e-09 A8= 8.85103e-11 A10= 5.63749e-13 Page 18 K = 0.00000e+00 A4=-5.25159e-06 A6= 9.60654e-09 A8= 1.99059e-10 A10 = 2.18984e-13 Page 19 K = 0.00000e+00 A4= 1.65477e-05 A6=-2.12733e-09 A8=-2.10165e-10 A10=-5.42771e-13 Page 20 K = 0.00000e+00 A4= 2.78314e-05 A6=-4.57377e-11 A8=-3.06723e-10 A10=-4.40553e-13 Page 25 K = 0.00000e+00 A4=-1.90150e-06 A6=-1.14006e-08 A8= 1.94372e-10 A10=-3.13798e-13 Page 26 K = 0.00000e+00 A4= 1.21404e-06 A6=-1.47608e-08 A8= 1.60536e-10 A10=-8.19478e-14 Various data Zoom ratio 3.53 Wide Angle Mid-Telephoto Focal length 28.84 63.61 101.85 F-number 4.12 4.12 4.12 Half angle of view (°) 33.94 18.78 11.99 Image height 19.41 21.64 21.64 Lens length 185.56 213.24 248.11 BF 19.76 22.67 23.79 Focused at infinity d 5 0.84 36.72 63.26 d13 43.96 12.08 1.99 d26 1.99 6.61 7.55 d28 10.77 26.93 43.30 d31 19.76 22.67 23.79 Lens Group Data Group starting plane focal length 1 1 224.21 2 6 -37.47 3 14 42.35 4 27 -74.98 5 29 103.98 Single lens data Lens starting surface focal length 1 1 -149.15 2 2 219.45 3 4 149.18 4 6 -45.07 5 8 -43.39 6 10 38.97 7 12 -198.07 8 15 72.06 9 17 69.87 10 19 -39.87 11 21 34.02 12 23 -67.07 13 25 120.92 14 27 -74.98 15 29 -69.23 16 30 41.49 [Numerical example 5] Unit: mm Surface Data Surface number rd nd νd 1 70.328 1.40 1.77250 49.6 2 22.088 10.97 3 -73.723 1.20 1.59282 68.6 4 48.767 0.30 5 40.202 5.90 2.00069 25.5 6 -8724.550 7.15 7 -107.745 1.20 1.76182 26.5 8 870.757 (variable) 9(Aperture) ∞ 1.00 10 51.791 8.00 1.49700 81.5 11 -40.676 1.30 1.51742 52.4 12 -75.751 1.00 13* 48.716 5.32 1.53110 55.9 14*∞ 7.01 15* -45.803 1.20 1.63550 23.9 16* -8392.994 (variable) 17 28.658 7.00 1.49700 81.5 18 -126.321 8.28 19* 57.529 2.67 1.58313 59.4 20* -174.229 (variable) 21 467.602 1.40 1.77047 29.7 22 33.495 (variable) 23 -280.157 1.20 1.77047 29.7 24 30.922 7.40 1.89286 20.4 25 -1261.259 (variable) Image plane ∞ Aspheric Data Page 13 K = 0.00000e+00 A4= 1.17635e-06 A6= 8.39348e-09 A8=-2.94742e-11 A10 = 1.03909e-13 Side 14 K = 0.00000e+00 A4=-1.43138e-06 A6=-1.43985e-08 A8=-2.42734e-11 A10= 3.61930e-14 Page 15 K = 0.00000e+00 A4=-3.12399e-05 A6=-4.17327e-08 A8= 2.23000e-10 A10=-2.14430e-13 Page 16 K = 0.00000e+00 A4=-2.70604e-05 A6=-1.40614e-08 A8= 2.31374e-10 A10=-2.89584e-13 Page 19 K = 0.00000e+00 A4=-4.08586e-07 A6= 2.10261e-08 A8=-1.05799e-10 A10=-1.64767e-13 Page 20 K = 0.00000e+00 A4= 2.25647e-05 A6= 5.45961e-08 A8=-1.63079e-10 A10 = 1.36031e-13 Various data Zoom ratio 1.37 Wide Angle Mid-Telephoto Focal length 24.70 28.06 33.95 F-number 2.06 2.06 2.06 Half angle of view (°) 37.63 35.20 31.36 Image height 19.04 19.79 20.69 Lens length 142.44 137.16 130.51 BF 13.00 16.72 18.74 Focused at infinity d 8 25.08 18.61 9.99 d16 12.80 10.20 6.65 d20 2.06 2.00 2.81 d22 8.60 8.73 11.42 d25 13.00 16.72 18.74 Lens Group Data Group starting plane focal length 1 1 -34.95 2 9 60.33 3 17 32.42 4 21 -46.89 5 23 520.52 Single lens data Lens starting surface focal length 1 1 -42.22 2 3 -49.33 3 5 40.00 4 7 -125.79 5 10 47.20 6 11 -171.96 7 13 91.70 8 15 -72.47 9 17 47.71 10 19 74.48 11 21 -46.89 12 23 -36.08 13 24 33.90 [Numerical example 6] Unit: mm Surface Data Surface number rd nd νd 1 64.794 1.40 1.77250 49.6 2 23.437 7.39 3 -119.163 1.20 1.59282 68.6 4 29.329 0.30 5 33.632 2.64 2.00069 25.5 6 39.199 9.00 7 48.688 2.50 1.69895 30.1 8 267.818 (variable) 9(Aperture) ∞ 1.00 10 22.214 4.10 1.49700 81.5 11 118.949 0.30 12* 28.009 3.85 1.53110 55.9 13* -11943.073 8.48 14* -32.272 1.20 1.63550 23.9 15* 97.739 2.00 16 31.986 5.00 1.49700 81.5 17 -20.425 0.86 18 -20.300 1.20 1.61772 49.8 19 973.519 1.71 20* 3287.795 2.80 1.58313 59.4 21* -36.400 (variable) 22 -65.742 1.40 1.77047 29.7 23 112.714 (variable) 24 150.483 1.20 1.77047 29.7 25 30.328 8.40 1.89286 20.4 26 -1261.259 (variable) Image plane ∞ Aspheric Data Side 12 K = 0.00000e+00 A4= 6.81112e-06 A6= 3.46070e-08 A8= 4.87552e-10 Page 13 K = 0.00000e+00 A4= 9.57446e-06 A6= 3.63132e-08 A8= 4.23627e-10 Side 14 K = 0.00000e+00 A4= 6.63625e-05 A6=-1.32141e-06 A8= 7.49398e-09 Page 15 K = 0.00000e+00 A4= 9.55795e-05 A6=-1.21597e-06 A8= 6.66698e-09 Page 20 K = 0.00000e+00 A4= 1.49199e-05 A6= 3.14851e-07 A8=-2.24040e-09 A10= 3.53478e-12 Page 21 K = 0.00000e+00 A4= 3.86494e-05 A6= 3.02828e-07 A8=-5.03393e-10 A10=-4.30998e-12 Various data Zoom ratio 1.37 Wide Angle Mid-Telephoto Focal length 24.70 28.14 33.95 F-number 3.61 3.61 3.61 Half angle of view (°) 37.62 35.11 31.76 Image height 19.04 19.79 21.02 Lens length 117.52 112.99 107.27 BF 13.12 12.36 12.12 Focused at infinity d 8 24.81 17.79 8.36 d21 2.66 4.56 8.20 d23 9.01 10.36 10.66 d26 13.12 12.36 12.12 Lens Group Data Group starting plane focal length 1 1 -37.50 2 9 31.51 3 22 -53.71 4 24 101.85 Single lens data Lens starting surface focal length 1 1 -48.24 2 3 -39.58 3 5 191.29 4 7 84.74 5 10 54.20 6 12 52.62 7 14 -38.04 8 16 25.90 9 18 -32.18 10 20 61.76 11 22 -53.71 12 24 -49.51 13 25 33.27 [Numerical example 7] Unit: mm Surface Data Surface number rd nd νd 1 88.460 2.00 1.80810 22.8 2 72.394 7.62 1.72916 54.7 3 313.995 (variable) 4 62.185 1.40 1.77250 49.6 5 19.078 13.11 6 -113.489 1.20 1.59282 68.6 7 23.488 6.30 2.00069 25.5 8 87.411 5.31 9 -30.794 1.50 2.00100 29.1 10 -36.180 (variable) 11 (Aperture) ∞ 1.00 12 62.743 4.19 1.49700 81.5 13 -38.530 3.19 14*∞ 1.51 1.63550 23.9 15* 38.254 5.00 16* 197.396 3.98 1.53110 55.9 17* -79.858 (variable) 18 32.688 8.00 1.49700 81.5 19 -42.952 0.20 20* 190.191 3.00 1.58313 59.4 21* -65.233 (variable) 22 174.335 1.40 1.77047 29.7 23 26.357 (variable) 24 -136.709 1.20 1.77047 29.7 25 30.118 7.43 1.89286 20.4 26 -1261.259 (variable) Image plane ∞ Aspheric Data Side 14 K = 0.00000e+00 A4=-5.45988e-05 A6= 1.08548e-07 A8= 2.86309e-10 A10=-1.19684e-12 Page 15 K = 0.00000e+00 A4=-2.62729e-05 A6= 9.68181e-08 A8= 5.86803e-11 A10 = 1.59233e-12 Page 16 K = 0.00000e+00 A4= 2.09208e-05 A6=-1.00232e-07 A8=-5.64735e-10 A10= 2.87305e-12 Page 17 K = 0.00000e+00 A4=-1.96431e-06 A6=-7.51385e-08 A8=-3.02722e-10 A10= 7.29195e-13 Page 20 K = 0.00000e+00 A4=-8.39646e-06 A6=-2.20276e-08 A8= 3.44078e-10 A10=-5.99556e-13 Page 21 K = 0.00000e+00 A4= 1.01249e-05 A6=-5.72739e-09 A8= 3.18518e-10 A10=-4.47050e-13 Various data Zoom ratio 1.98 Wide Angle Mid-Telephoto Focal length 24.70 36.85 48.80 F-number 2.90 2.90 2.90 Half angle of view (°) 38.86 30.19 23.91 Image height 19.90 21.44 21.64 Lens length 141.33 149.69 160.22 BF 18.26 27.93 25.11 Focused at infinity d 3 0.85 11.71 26.06 d10 19.40 9.19 2.00 d17 11.70 7.78 6.58 d21 4.52 2.04 2.00 d23 8.06 12.49 19.94 d26 18.26 27.93 25.11 Lens Group Data Group starting plane focal length 1 1 171.25 2 4 -30.40 3 11 73.35 4 18 27.53 5 22 -40.47 6 24 -1188.08 Single lens data Lens starting surface focal length 1 1 -522.33 2 2 127.34 3 4 -36.14 4 6 -32.72 5 7 30.59 6 9 -240.10 7 12 48.70 8 14 -60.20 9 16 107.59 10 18 38.71 11 20 83.66 12 22 -40.47 13 24 -31.93 14 25 33.03

[0056] [Table 1]

[0057] 15 shows a digital camera as an imaging device using the zoom lens of each of the above-mentioned embodiments as an imaging optical system. Reference numeral 20 denotes a camera body, and 21 denotes an imaging optical system constituted by any of the zoom lenses of embodiments 1 to 5. Reference numeral 22 denotes a solid-state imaging element such as a CCD sensor or a CMOS sensor that is built into the camera body 20 and captures an optical image (subject image) formed by the imaging optical system 21. Reference numeral 23 denotes a recording unit that records image data generated by processing an imaging signal from the imaging element 22, and 24 denotes a rear display that displays the image data.

[0058] By using the zoom lens of each embodiment, it is possible to obtain a small, lightweight digital camera that has high optical performance regardless of changes in temperature or humidity.

[0059] The digital camera may be a single-lens reflex camera having a quick-turn mirror, or a mirrorless camera having no quick-turn mirror, or may be a camera for silver halide film.

[0060] The above embodiment includes the following configurations.

[0061] (Configuration 1) A zoom lens having a plurality of lens groups, in which the spacing between adjacent lens groups changes during zooming, the plurality of lens groups include a first lens group arranged closest to the object, an intermediate lens group arranged closer to the image side than the first lens group and having positive refractive power, and two or more subsequent lens groups arranged closer to the image side than the intermediate lens group, the intermediate lens group includes a plurality of lenses, and among the plurality of lenses, the resin lenses are a positive resin lens having a positive refractive power and a negative resin lens having a negative refractive power; When the space between the positive resin lens and the negative resin lens is considered to be entirely air, the refractive power of an air lens formed between the positive resin lens and the negative resin lens is negative; the subsequent lens group includes a focus lens group that has negative refractive power and moves during focusing; When the focal length of the intermediate lens group is fGP and the focal length of the positive resin lens is fp, 0 <fp / fGP≦1.95 A zoom lens characterized by satisfying the following conditions. (Configuration 2) The refractive power Φ of the air lens is expressed by the following equation: where ndp and ndp are the refractive indices at the d-line of the positive resin lens and the negative resin lens, respectively, Rp and Rn are the radii of curvature of the lens surface of the positive resin lens on the negative resin lens side and the lens surface of the negative resin lens on the positive resin lens side, respectively, and d is the distance on the optical axis between the lens surface on the negative resin lens side and the lens surface on the positive resin lens side. Φ=(1-ndp) / Rp-(1-ndn) / Rn +(1-ndp) (1-ndn) d / (Rp Rn) 2. The zoom lens according to claim 1, wherein: (Configuration 3) 3. The zoom lens according to configuration 1 or 2, wherein the intermediate lens group is adjacent to the aperture stop on the image side or includes the aperture stop. (Configuration 4) 4. The zoom lens according to any one of configurations 1 to 3, wherein the positive resin lens and the negative resin lens each have one or more aspheric lens surfaces. (Configuration 5) Let fn be the focal length of the positive resin lens, and ft be the focal length of the zoom lens at the telephoto end. -2.45≦fn / ft≦-0.10 5. The zoom lens according to any one of configurations 1 to 4, which satisfies the following condition: (Configuration 6) When the focal length of the positive resin lens is fn, -1.20≦fn / fp≦-0.25 6. The zoom lens according to any one of configurations 1 to 5, which satisfies the following condition: (Configuration 7) Let Rp and Rn be the radii of curvature of the lens surface of the positive resin lens facing the negative resin lens and the lens surface of the negative resin lens facing the positive resin lens, respectively. -1.80≦(Rn+Rp) / (Rn-Rp)<0 7. The zoom lens according to any one of configurations 1 to 6, which satisfies the following condition: (Configuration 8) When the focal length of the focus lens group is fGF, -1.90≦fGF / ft≦-0.40 8. The zoom lens according to any one of configurations 1 to 7, which satisfies the following condition: (Configuration 9) When the F-number of the zoom lens at the telephoto end is Ft, 1.00≦Ft≦5.60 9. The zoom lens according to any one of configurations 1 to 8, which satisfies the following condition: (Configuration 10) When the specific gravity of the positive resin lens is ρp and the specific gravity of the negative resin lens is ρn, ρp≦1.70 and ρn≦1.70 10. The zoom lens according to any one of configurations 1 to 9, which satisfies the following condition: (Configuration 11) When the Abbe number of the negative resin lens based on the d line is νdn, 15.00≦νdn≦40.00 11. The zoom lens according to any one of configurations 1 to 10, characterized in that the following condition is satisfied: (Configuration 12) -2.30≦Φ<0 3. The zoom lens according to claim 2, wherein the following condition is satisfied: (Configuration 13) 13. The zoom lens according to any one of configurations 1 to 12, wherein the subsequent lens group includes one or more lens groups arranged closer to the image side than the focus lens group. (Configuration 14) The zoom lens according to any one of configurations 1 to 13, characterized in that the multiple lens groups are composed of, arranged in order from the object side to the image side, the first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group as the intermediate lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group as the focus lens group having negative refractive power, and a sixth lens group having positive refractive power. (Configuration 15) The zoom lens according to any one of configurations 1 to 13, characterized in that the multiple lens groups are composed of, arranged in order from the object side to the image side, the first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group as the intermediate lens group having positive refractive power, a fourth lens group as the focus lens group having negative refractive power, and a fifth lens group having positive refractive power. (Configuration 16) The zoom lens according to any one of configurations 1 to 13, characterized in that the multiple lens groups are composed of, arranged in order from the object side to the image side, the first lens group having negative refractive power, a second lens group serving as the intermediate lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group serving as the focus lens group having negative refractive power, and a fifth lens group having positive refractive power. (Configuration 17) The zoom lens according to any one of configurations 1 to 13, characterized in that the multiple lens groups are composed of, arranged in order from the object side to the image side, the first lens group having negative refractive power, a second lens group serving as the intermediate lens group having positive refractive power, a third lens group serving as the focus lens group having negative refractive power, and a fourth lens group having positive refractive power. (Configuration 18) The zoom lens according to any one of configurations 1 to 17; and an image sensor for capturing an optical image formed by the zoom lens.

[0062] The embodiments described above are merely representative examples, and various modifications and alterations are possible for each embodiment when implementing the present invention. [Explanation of symbols]

[0063] L1 First lens group GP intermediate lens group Pp positive resin lens Pn negative resin lens GF Focus Lens Group SP aperture stop

Claims

1. A zoom lens having a plurality of lens groups, in which the spacing between adjacent lens groups changes during zooming, the plurality of lens groups include a first lens group arranged closest to the object, an intermediate lens group arranged closer to the image side than the first lens group and having positive refractive power, and two or more subsequent lens groups arranged closer to the image side than the intermediate lens group, the intermediate lens group includes a plurality of lenses, and among the plurality of lenses, the resin lenses are a positive resin lens having a positive refractive power and a negative resin lens having a negative refractive power; When the space between the positive resin lens and the negative resin lens is considered to be entirely air, the refractive power of an air lens formed between the positive resin lens and the negative resin lens is negative; the subsequent lens group includes a focus lens group that has negative refractive power and moves during focusing; When the focal length of the intermediate lens group is fGP and the focal length of the positive resin lens is fp, 0<fp / fGP≦1.95 A zoom lens characterized by satisfying the following conditions.

2. The refractive power Φ of the air lens is expressed by the following equation: where ndp and ndp are the refractive indices at the d-line of the positive resin lens and the negative resin lens, respectively; Rp and Rn are the radii of curvature of the lens surface of the positive resin lens on the negative resin lens side and the lens surface of the negative resin lens on the positive resin lens side, respectively; and d is the distance on the optical axis between the lens surface on the negative resin lens side and the lens surface on the positive resin lens side. Φ=(1-ndp) / Rp-(1-ndn) / Rn +(1-ndp)・(1-ndn)・d / (Rp・Rn) 2. The zoom lens according to claim 1, wherein:

3. 2. The zoom lens according to claim 1, wherein the intermediate lens group is adjacent to the aperture stop on the image side or includes the aperture stop.

4. 2. The zoom lens according to claim 1, wherein the positive resin lens and the negative resin lens each have one or more aspheric lens surfaces.

5. When the focal length of the positive resin lens is fn and the focal length of the zoom lens at the telephoto end is ft, -2.45≦fn / ft≦-0.10 2. The zoom lens according to claim 1, which satisfies the following condition:

6. When the focal length of the positive resin lens is fn, -1.20≦fn / fp≦-0.25 2. The zoom lens according to claim 1, which satisfies the following condition:

7. Let Rp and Rn be the radii of curvature of the lens surface of the positive resin lens facing the negative resin lens and the lens surface of the negative resin lens facing the positive resin lens, respectively. -1.80≦(Rn+Rp) / (Rn-Rp)<0 2. The zoom lens according to claim 1, which satisfies the following condition:

8. When the focal length of the focus lens group is fGF, −1.90≦fGF / ft≦−0.40 2. The zoom lens according to claim 1, which satisfies the following condition:

9. When the F-number of the zoom lens at the telephoto end is Ft, 1.00≦Ft≦5.60 2. The zoom lens according to claim 1, which satisfies the following condition:

10. When the specific gravity of the positive resin lens is ρp and the specific gravity of the negative resin lens is ρn, ρp≦1.70 and ρn≦1.70 2. The zoom lens according to claim 1, which satisfies the following condition:

11. When the Abbe number of the negative resin lens based on the d line is νdn, 15.00≦νdn≦40.00 2. The zoom lens according to claim 1, which satisfies the following condition:

12. −2.30≦Φ<0 3. The zoom lens according to claim 2, which satisfies the following condition:

13. 2. The zoom lens according to claim 1, wherein the subsequent lens group includes one or more lens groups arranged closer to the image side than the focus lens group.

14. 2. The zoom lens according to claim 1, wherein the plurality of lens groups are comprised of, arranged in order from the object side to the image side, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group serving as the intermediate lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group serving as the focus lens group having negative refractive power, and a sixth lens group having positive refractive power.

15. 2. The zoom lens according to claim 1, wherein the plurality of lens groups are arranged in order from the object side to the image side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group serving as the intermediate lens group having positive refractive power, a fourth lens group having negative refractive power as the focus lens group, and a fifth lens group having positive refractive power.

16. 2. The zoom lens according to claim 1, wherein the plurality of lens groups are arranged in order from the object side to the image side: the first lens group having negative refractive power, a second lens group serving as the intermediate lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group serving as the focus lens group having negative refractive power, and a fifth lens group having positive refractive power.

17. 2. The zoom lens according to claim 1, wherein the plurality of lens groups are arranged in order from the object side to the image side: the first lens group having negative refractive power, a second lens group serving as the intermediate lens group having positive refractive power, a third lens group serving as the focus lens group having negative refractive power, and a fourth lens group having positive refractive power.

18. A zoom lens according to any one of claims 1 to 17; and an image sensor for capturing an optical image formed by the zoom lens.

Images