Optical system and imaging apparatus

Abstract

To obtain an optical system that is compact and lightweight and has a high optical characteristic.SOLUTION: An optical system has one or more positive lenses Gp1 and one or more negative lenses Gn1. A positive lens disposed closest to an object side among the one or more positive lenses is a positive lens Gp1, and a negative lens disposed closer to an image side than the positive lens Gp1 and disposed closest to the object side among the one or more negative lenses is a negative lens Gn1. At least one of an object side surface and an image side surface of the positive lens Gp1 is an aspherical surface. A relation among the total lens length of the optical system, a focal distance of the optical system, and a distance on an optical axis from the image side surface of the positive lens Gp1 to an object side surface of the negative lens Gn1 is defined.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system and an imaging device. [Background technology]

[0002] Optical systems used in imaging devices are required to be compact and lightweight as a whole, and to have high optical performance capable of effectively correcting various aberrations, including chromatic aberration. Known optical systems that can be configured to be compact as a whole include so-called telephoto optical systems, in which an optical system with positive refractive power is arranged on the object side and an optical system with negative refractive power is arranged on the image side. However, telephoto optical systems tend to become larger as the focal length increases, and the use of large-diameter or heavy lenses tends to increase the overall weight of the optical system.

[0003] Patent Document 1 proposes an optical system that is lightweight by devising a lens configuration that is arranged closer to the object than the aperture stop. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-8047 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, methods for further reducing the weight of an optical system include reducing the number of lenses that make up the optical system, and constructing the optical system using lenses with weak refractive power. However, in the former case, the refractive power of each lens becomes strong, which tends to worsen various aberrations, and in the latter case, the total length of the lens in the optical system becomes long, which tends to make the optical system large.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide an optical system that is small, lightweight, and has high optical characteristics. [Means for solving the problem]

[0007] The optical system of the present invention has two or more positive lenses and one or more negative lenses, and the optical system comprises, arranged in order from the object side to the image side, a first lens group having positive refractive power that does not move during focusing, a second lens group having positive refractive power that moves during focusing, and a third lens group having negative refractive power that does not move during focusing, wherein the second lens group moves toward the object side during focusing from an object at infinity to an object at the closest distance, and among the positive lenses arranged in the optical system, the positive lens arranged closest to the object is designated as positive lens Gp1, and among the negative lenses arranged in the optical system, the negative lens that is arranged closer to the image than the positive lens Gp1 and is arranged closest to the object is designated as negative lens Gn1, and among the positive lenses arranged in the optical system, the positive lens that is second closest to the object is designated as positive lens Gp2, and of the positive lenses arranged in the optical system, the positive lens arranged on the image side of the positive lens Gp3 that is arranged third from the object side is defined as a positive lens Gp4, the third lens group has the positive lens Gp4 and a negative lens Gn2 arranged on the image side of the positive lens Gp4, at least one of the object side surface and the image side surface of the positive lens Gp1 is aspherical, the lens arranged adjacent to the image side of the positive lens Gp1 has positive refractive power, the total lens length of the optical system is LD, the focal length of the optical system is f, the distance on the optical axis from the image side surface of the positive lens Gp1 to the object side surface of the negative lens Gn1 is Dpn, the refractive index to the d-line of the material of the positive lens Gp2 is Ndp2, the Abbe number based on the d-line is vdp2, the refractive index to the d-line of the material of the negative lens Gn2 is Ndn2, and the Abbe number based on the d-line is vdn2, 0.20 <LD / f<1.00 0.382 <Dpn / LD<0.800 1.400 <Ndp2<1.630 61.0<νdp2<96.0 1.400 <Ndn2<1.630 61.0<νdn2<96.0 The present invention is characterized in that the following conditional expression is satisfied: [Effects of the Invention]

[0008] According to the present invention, it is possible to obtain an optical system that is small, lightweight, and has high optical characteristics. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of an optical system according to a first embodiment. [Figure 2] 3A to 3C are aberration diagrams of the optical system of Example 1. [Figure 3] FIG. 10 is a cross-sectional view of an optical system according to a second embodiment. [Figure 4] 10A to 10C are aberration diagrams of the optical system of Example 2. [Figure 5] FIG. 10 is a cross-sectional view of an optical system according to a third embodiment. [Figure 6] 10A to 10C are aberration diagrams of the optical system of Example 3. [Figure 7] FIG. 10 is a cross-sectional view of an optical system according to a fourth embodiment. [Figure 8] 10A to 10C are aberration diagrams of the optical system of Example 4. [Figure 9] FIG. 10 is a cross-sectional view of an optical system according to a fifth embodiment. [Figure 10] 10A to 10C are aberration diagrams of the optical system of Example 5. [Figure 11] FIG. 10 is a cross-sectional view of an optical system according to a sixth embodiment. [Figure 12] 10A to 10C are aberration diagrams of the optical system of Example 6. [Figure 13] FIG. 10 is a cross-sectional view of an optical system according to a seventh embodiment. [Figure 14] 10A to 10C are aberration diagrams of the optical system of Example 7. [Figure 15] FIG. 10 is a cross-sectional view of the optical system of Example 8. [Figure 16] 10A to 10C are aberration diagrams of the optical system of Example 8. [Figure 17] FIG. 1 is a schematic diagram of an imaging device. [Figure 18] FIG. 10 is an explanatory diagram of a method for calculating a conditional expression for an aspherical surface shape. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of an optical system and an imaging apparatus having the same according to the present invention will be described with reference to the accompanying drawings.

[0011] [Example of optical system] The optical system of each embodiment is a photographic optical system used in imaging devices such as digital still cameras, broadcast cameras, silver halide film cameras, and surveillance cameras.

[0012] 1, 3, 5, 7, 9, 11, 13, and 15 are cross-sectional views of the optical system L0 of each of Examples 1 to 8 when focusing on an object at infinity. In each cross-sectional view, the left side is the object side (front) and the right side is the image side (rear). The aperture stop SP determines (limits) the light beam at the maximum F-number (Fno). When focusing from an object at infinity to an object at the closest distance, the focus lens group moves as indicated by the arrows in the figures. When the optical system L0 is used as the photographic optical system of a digital still camera or digital video camera, the image plane IP becomes the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor. When the optical system L0 is used as the photographic optical system of a silver halide film camera, the image plane IP corresponds to the film surface.

[0013] 2, 4, 6, 8, 10, 12, 14, and 16 are aberration diagrams of the optical system L0 of Examples 1 to 8 when focusing on an object at infinity. In the spherical aberration diagrams, Fno is the F-number, and shows the amount of spherical aberration for the d-line (wavelength 587.56 nm) and the g-line (wavelength 435.8 nm). In the astigmatism diagrams, dS shows the amount of astigmatism on the sagittal image plane, and dM shows the amount of astigmatism on the meridional image plane. In the distortion diagrams, the amount of distortion for the d-line is shown. In the chromatic aberration diagrams, the amount of chromatic aberration for the g-line is shown. ω is the half angle of view (°) of the image obtained by paraxial calculation.

[0014] In order to obtain an optical system L0 that is small, lightweight, and has high optical characteristics, it is important to appropriately determine the surface shape and arrangement of the lenses that are positioned relatively closer to the object and tend to have larger diameters.

[0015] Therefore, the optical system L0 according to this embodiment has a positive lens Gp1 and a negative lens Gn1 arranged on the image side of the positive lens Gp1. The positive lens Gp1 is the positive lens arranged closest to the object among the positive lenses included in the optical system L0, and the negative lens Gn1 is the negative lens arranged closest to the object among the negative lenses included in the optical system L0. By configuring a telephoto optical system by arranging the negative lens Gn1 on the image side of the positive lens Gp1, the overall lens length of the optical system L0 can be shortened and various aberrations generated by the positive lens Gp1 can be corrected by the negative lens Gn1.

[0016] Furthermore, in the optical system L0 according to this embodiment, at least one of the object-side surface and the image-side surface of the positive lens Gp1 is configured as an aspheric surface. This makes it possible to reduce the occurrence of various aberrations, such as spherical aberration and coma, that occur in the positive lens Gp1. In particular, it is preferable that the positive lens Gp1 has a shape in which the negative refractive power increases from the vertex toward the periphery (the outer periphery of the positive lens Gp1). This makes it possible to enhance the effect of reducing spherical aberration, coma, and the like. Furthermore, the optical system L0 according to this embodiment satisfies the following conditional expressions (1) and (2). 0.20 <LD / f<1.00 ···(1) 0.382 <Dpn / LD<0.800 ···(2)

[0017] Here, LD is the total lens length of the optical system L0, f is the focal length of the optical system L0, and Dpn is the distance on the optical axis from the image-side surface of the positive lens Gp1 to the object-side surface of the negative lens Gn1.

[0018] Conditional formula (1) defines the relationship between the focal length of optical system L0 and the overall lens length of optical system L0. If the upper limit of conditional formula (1) is exceeded and the overall lens length becomes long, optical system L0 becomes large, which is undesirable. If the lower limit of conditional formula (1) is exceeded and the overall lens length becomes short, the refractive power of each lens element constituting optical system L0 becomes strong, which is undesirable because it makes it difficult to correct various aberrations, including chromatic aberration of magnification.

[0019] Conditional expression (2) defines the relationship between the axial distance between the positive lens Gp1 and the negative lens Gn1 and the overall lens length. By increasing the distance between the positive lens Gp1 and the negative lens Gn2 so as to satisfy conditional expression (2), the diameter of the axial light beam incident on the negative lens Gn1 can be reduced, thereby enabling the diameter of the negative lens Gn1 to be reduced. By decreasing the diameter of the negative lens Gn1, which is positioned relatively closer to the object in the optical system L0, the weight of the negative lens Gn1 can be reduced, thereby enabling the optical system L0 to be made lighter. If the distance between the positive lens Gp1 and the negative lens Gn1 is increased beyond the upper limit of conditional expression (2), it becomes difficult for the negative lens Gn1 to correct various aberrations, such as spherical aberration, coma, and lateral chromatic aberration, which occur in the positive lens Gp1. If the distance between the positive lens Gp1 and the negative lens Gn1 is decreased below the lower limit of conditional expression (2), the diameter of the axial light beam incident on the negative lens Gn1 increases. This is undesirable because it increases the diameter of the negative lens Gn1 and makes it difficult to reduce the weight of the optical system L0. It is preferable that the numerical ranges of the conditional expressions (1) and (2) be set to the numerical ranges of the following conditional expressions (1a) and (2a). 0.50 <LD / f<0.98 ···(1a) 0.391 <Dpn / LD<0.600 ···(2a) Furthermore, it is preferable that the numerical ranges of the conditional expressions (1) and (2) be set to the numerical ranges of the following conditional expressions (1b) and (2b). 0.60 <LD / f<0.97 ···(1b) 0.426 <Dpn / LD<0.500 ···(2b)

[0020] Next, a preferred configuration of the optical system L0 according to the embodiment will be described. In telephoto optical systems, the height of the marginal rays of the axial light beam passing through lenses located relatively closer to the object is high. Therefore, the configuration of lenses located relatively closer to the object is important for effectively correcting spherical aberration. Therefore, the optical system L0 according to the embodiment preferably includes one or more positive lenses, more preferably two or more positive lenses, located on the image side of the positive lens Gp1 and closer to the object than the aperture stop SP. By sharing the positive refractive power among multiple positive lenses, including the positive lens Gp1, the radius of curvature of the single positive lens can be made larger than when only one positive lens with strong refractive power is located. This allows the positive refractive power of the optical system L0 to be maintained, shortening the overall lens length while reducing the occurrence of various aberrations, including spherical aberration. Furthermore, it is preferable that the optical system L0 include a positive lens Gp1, a positive lens Gp2, a negative lens Gn1, and a positive lens Gp3, arranged in succession from the most object-side to the image side. This facilitates correction of spherical aberration and coma in the optical system L0.

[0021] It is preferable that the optical system L0 comprises, arranged in order from the object side to the image side, a first lens group B1 that does not move during focusing, a second lens group B2 that moves during focusing, and a third lens group B3 that does not move during focusing. The first lens group B1 has positive refractive power, and the second and third lens groups B3 each have positive or negative refractive power. The positive refractive power of the first lens group B1 converges the light beam passing through the first lens group B1, thereby reducing the diameter of the light beam passing through the second lens group B2. This allows the diameter of the second lens group B2 to be reduced. This allows the weight of the second lens group B2, which is the lens group that moves during focusing, to be reduced, and mechanisms such as an actuator for driving the second lens group B2 to be simplified. It is also preferable that the second lens group B2 be composed of three or fewer lenses. This further reduces the weight of the second lens group B2, thereby reducing the weight of the optical system L0.

[0022] It is preferable that the third lens group B3 includes a positive lens Gp4 located closer to the image side than the third positive lens, counting from the object side, among the positive lenses included in the optical system L0, and one or more negative lenses located on the image side of the positive lens Gp4. By arranging a positive lens and a negative lens in order from the object side to the image side, relatively closer to the image side of the optical system L0, the refractive power arrangement of the subsystems of the optical system L0 can also be made telephoto type. This further facilitates shortening the overall lens length and enhances the compactness of the optical system L0. In particular, it is preferable that multiple negative lenses (negative lens Gn2 and negative lens Gn3) be located on the image side of the positive lens Gp4. In telephoto type optical systems, the height of the chief ray of off-axis light beams passing through the image-side lenses tends to be high, so the configuration of the lenses located relatively closer to the image side of the optical system L0 is important for effectively correcting distortion. By arranging multiple negative lenses closer to the image side of the positive lens Gp4 to share the negative refractive power, the radius of curvature of the single negative lens can be made larger than when only a single negative lens with strong refractive power is located. This makes it possible to reduce the occurrence of various aberrations, including distortion, while maintaining the negative refractive power necessary for miniaturizing the optical system L0. Furthermore, it is preferable that the optical system L0 according to the embodiment satisfies one or more of the following conditional expressions (3) to (22). 1.493 <Ndp1<1.700 ···(3) 55.0<νdp1<96.0 (4) 1.400 <Ndp2<1.630 ···(5) 61.0<νdp2<96.0 (6) 1.400 <Ndp3<1.630 ···(7) 61.0<νdp3<96.0 (8) 1.400 <Ndp4<1.630 ···(9) 50.0<νdp4<96.0 (10) 1.600 <Ndn1<1.950 ···(11) 20.0<νdn1<50.0 (12) 1.400 <Ndn2<1.630 ···(13) 61.0<νdn2<96.0 (14) 1,800 <Ndn3<2.200 ···(15) 14.0<νdn3<24.0 (16) 0.10 <f1 / f<1.20 ···(17) 0.00001 <DRGp1×Fno / f<0.00500 ···(18) 0.10<(rp2+rp1) / (rp2-rp1)<2.00 (19) 0.20 <f11 / f<2.00 ···(20) 0.20 <d12 / f11<0.60 ···(21) 20 <YASPH<200 ···(22)

[0023] Here, the refractive index of the material of the positive lens Gp1 with respect to the d-line is Ndp1, and the Abbe number of the material of the positive lens Gp1 with respect to the d-line is νdp1.

[0024] In this specification, the Abbe number νd of a material based on the d-line is expressed as follows, where Nd, NF, and NC are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm) of the Fraunhofer lines: νd=(Nd-1) / (NF-NC) It is expressed as:

[0025] When the optical system L0 has two or more positive lenses, the refractive index of the material of the positive lens Gp2, which is the second positive lens included in the optical system L0 as counted from the object side, is defined as Ndp1, and the Abbe number of the material of the positive lens Gp2, which is referenced to the d line, is defined as νdp2. When the optical system L0 has three or more positive lenses, the refractive index of the material of the positive lens Gp3, which is the third positive lens included in the optical system L0 as counted from the object side, is defined as Ndp3, and the Abbe number of the material of the positive lens Gp3, which is referenced to the d line, is defined as νdp3. When the optical system L0 has four or more positive lenses, the positive lens included in the optical system L0 that is located closer to the image side than the positive lens Gp3, which is the third positive lens included in the optical system L0 as counted from the object side, is defined as positive lens Gp4. In this case, the refractive index of the material of the positive lens Gp4 as counted from the d line is defined as Ndp4, and the Abbe number of the material of the positive lens Gp4, which is referenced to the d line, is defined as νdp4.

[0026] The refractive index of the material of the negative lens Gn1 with respect to the d-line is Ndn1, and the Abbe number of the material of the negative lens Gn1 with respect to the d-line is νdn1.

[0027] When the optical system L0 consists of a first lens group B1, a second lens group B2, and a third lens group B3 arranged in that order from the object side to the image side, the third lens group has a negative lens Gn2. In this case, the refractive index of the material of the negative lens Gn2 at the d-line is defined as Ndn2, and the Abbe number of the material of the negative lens Gn2 referenced to the d-line is defined as νdn2. When the third lens group has a negative lens Gn3, the refractive index of the material of the negative lens Gn3 at the d-line is defined as Ndn3, and the Abbe number of the material of the negative lens Gn3 referenced to the d-line is defined as νdn3.

[0028] When an optical system L0 is composed of a first lens unit B1, a second lens unit B2, and a third lens unit B3 arranged in that order from the object side to the image side, the focal length of the first lens unit B1 is defined as f1. The focal length of the optical system is defined as f. The aspherical amount of the aspherical surface of the positive lens Gp1 at a position corresponding to 70% of the effective diameter is defined as DRGp1, and the F-number of the optical system is defined as Fno.

[0029] Here, the effective diameter of a lens refers to the diameter of a circle whose radius is the height from the optical axis of a ray of light that passes through the lens surface at a position farthest from the optical axis.

[0030] Next, the aspherical amount at the 70% position of the effective diameter of the positive lens Gp1 will be described with reference to FIG. 18. The 70% position of the effective diameter of the positive lens Gp1 refers to the position 70% of the way from the position on the optical axis (the vertex of the surface) of the positive lens Gp1 to the position that determines the effective diameter. If the F-number when the optical system L0 is focused on an object at infinity is Fno, the effective diameter ΦGp1 of the positive lens Gp1 is ΦGp1 = f / Fno. The height yea from the optical axis at position P that determines the effective diameter on the aspherical surface is y = ΦGp1 / 2, and the 70% position of the effective diameter of the positive lens Gp1 is expressed as y = 0.7 × yea. The aspherical amount is the difference in position along the optical axis between an arbitrary position on a spherical surface (reference spherical surface) connecting the effective diameter position P on the aspherical surface and the vertex of the positive lens Gp1 and a position on the aspherical surface at the same height as that position. Therefore, the aspherical amount at 70% of the effective diameter is expressed as DR=X-Xr in FIG.

[0031] The radius of curvature of the object-side surface of the positive lens Gp1 is rp1, and the radius of curvature of the image-side surface of the positive lens Gp1 is rp2. In the case of an aspherical surface, the radius of curvature of that surface is the radius of curvature of the approximate spherical surface when the area near the axis is approximated by a spherical surface. The focal length of the positive lens Gp1 is f11.

[0032] When the optical system L0 has two or more positive lenses, the second positive lens included in the optical system L0, counting from the object side, is defined as the positive lens Gp2, and the distance on the optical axis from the image side surface of the positive lens Gp1 to the object side surface of the positive lens Gp2 is defined as d12.

[0033] The maximum height of the incident point of the axial ray on the aspheric surface of the positive lens Gp1 when focusing on an object at infinity is defined as YASPH (mm). Note that the height here refers to the distance from the optical axis in the direction perpendicular to the optical axis (radial direction).

[0034] Conditional expression (3) defines the refractive index of the material of the positive lens Gp1. By using a material with a moderately high refractive index, both the size and weight of the optical system L0 can be reduced. With typical optical materials, the higher the refractive index, the greater the specific gravity. Therefore, if the refractive index of the material of the positive lens Gp1 becomes high enough to exceed the upper limit of conditional expression (3), the specific gravity of the positive lens Gp1, which has the largest diameter in the optical system L0, becomes large, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the refractive index of the material of the positive lens Gp1 becomes low enough to fall below the lower limit of conditional expression (3), the positive refractive power of the positive lens Gp1 becomes weak, making it difficult to reduce the size of the optical system L0, which is undesirable.

[0035] Conditional formula (4) defines the Abbe number of the material of the positive lens Gp1. By setting the Abbe number appropriately, high optical performance and lightweight design can be achieved at the same time.

[0036] Generally, optical materials have a tendency for their specific gravity to increase as their Abbe number increases. Therefore, if the Abbe number increases beyond the upper limit of conditional expression (4), the specific gravity of the positive lens Gp1 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the Abbe number of the material of the positive lens Gp2 decreases below the lower limit of conditional expression (4), it becomes difficult to correct chromatic aberrations such as chromatic aberration of magnification that occur in the positive lens Gp2, which is undesirable.

[0037] Condition (5) defines the refractive index of the material of the positive lens Gp2. By using a material with an appropriately high refractive index, the optical system L0 can be made both compact and lightweight.

[0038] If the refractive index of the material of the positive lens Gp2 becomes higher than the upper limit of conditional expression (5), the specific gravity of the positive lens Gp2 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the refractive index of the material of the positive lens Gp2 becomes lower than the lower limit of conditional expression (5), the refractive power of the positive lens Gp2 weakens, the overall lens length increases, and it becomes difficult to reduce the size of the optical system L0, which is undesirable. Conditional expression (6) defines the Abbe number of the material of the positive lens Gp2. By setting the Abbe number appropriately, high optical performance and lightweight design are achieved. If the Abbe number of the material of the positive lens Gp2 becomes higher than the upper limit of conditional expression (6), the specific gravity of the positive lens Gp2 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the Abbe number of the material of the positive lens Gp2 becomes lower than the lower limit of conditional expression (6), it becomes undesirable because chromatic aberrations, such as chromatic aberration of magnification, generated by the positive lens Gp2 become large.

[0039] Conditional expression (7) defines the refractive index of the material of the positive lens Gp3. By using a material with a moderately high refractive index, both size and weight of the optical system L0 can be reduced. If the refractive index of the material of the positive lens Gp3 becomes high enough to exceed the upper limit of conditional expression (7), the specific gravity of the positive lens Gp3 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the refractive index of the material of the positive lens Gp3 becomes low enough to fall below the lower limit of conditional expression (7), the refractive power of the positive lens Gp3 weakens, increasing the overall lens length and making it difficult to reduce the size of the optical system L0, which is undesirable.

[0040] Conditional formula (8) defines the Abbe number of the material of the positive lens Gp3. By setting the Abbe number appropriately, high optical performance and lightweight design can be achieved at the same time.

[0041] If the Abbe number of the material of the positive lens Gp3 becomes large enough to exceed the upper limit of conditional expression (8), the specific gravity of the positive lens Gp3 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable.If the Abbe number of the material of the positive lens Gp3 becomes small enough to fall below the lower limit of conditional expression (8), chromatic aberrations such as chromatic aberration of magnification that occur in the positive lens Gp3 become large, which is undesirable.

[0042] Conditional expression (9) defines the refractive index of the material of the positive lens Gp4. By using a material with a moderately high refractive index, both size and weight of the optical system L0 can be reduced. If the refractive index of the material of the positive lens Gp4 becomes too high, exceeding the upper limit of conditional expression (9), the specific gravity of the positive lens Gp4 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the refractive index of the material of the positive lens Gp4 becomes too low, below the lower limit of conditional expression (9), the refractive power of the positive lens Gp4 becomes weak, making it difficult to reduce the size of the optical system L0, which is undesirable.

[0043] Conditional expression (10) defines the Abbe number of the material of the positive lens Gp4. By setting the Abbe number appropriately, both high optical performance and lightweight design are achieved. If the Abbe number of the material of the positive lens Gp4 becomes large enough to exceed the upper limit of conditional expression (10), the specific gravity of the positive lens Gp4 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the Abbe number of the material of the positive lens Gp4 becomes small enough to fall below the lower limit of conditional expression (10), it becomes difficult to correct chromatic aberrations such as chromatic aberration of magnification that occur in the positive lens Gp4, which is undesirable.

[0044] Conditional expression (11) specifies the refractive index of the material of the negative lens Gn1. This allows for the optical system L0 to be compact, lightweight, and have high image quality. In a telephoto optical system L0, the overall lens length is shortened by placing a lens with negative refractive power relatively closer to the image side of the optical system L0. However, increasing the negative refractive power tends to increase the Petzval sum and the curvature of field in the negative direction. Therefore, by constructing the negative lens Gn1 from a material with a relatively high refractive index, it becomes easier to achieve good optical performance while shortening the overall lens length. However, since the specific gravity of general optical materials tends to increase with a high refractive index, increasing the refractive index of the negative lens Gn1 too much makes it difficult to reduce the weight of the optical system L0. If the refractive index of the material of the negative lens Gn1 increases beyond the upper limit of conditional expression (11), the specific gravity of the negative lens Gn1 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the refractive index of the material of the negative lens Gn1 falls below the lower limit of conditional expression (11), the Petzval sum increases in the negative direction, and the curvature of field increases in the negative direction. This makes it difficult to achieve high image quality, which is undesirable.

[0045] Conditional expression (12) defines the Abbe number of the material of the negative lens Gn1. By appropriately setting the Abbe number of the material of the negative lens Gn1, chromatic aberration can be effectively corrected while also achieving a lightweight optical system L0. With typical optical materials, a small Abbe number of the material tends to result in a large partial dispersion ratio θgF. If the Abbe number increases beyond the upper limit of conditional expression (12), the partial dispersion ratio θgF of the negative lens Gn1 becomes too small. This makes it difficult to correct second-order chromatic aberration, which is undesirable. If the Abbe number of the material of the negative lens Gn1 decreases below the lower limit of conditional expression (12), the correction effect of first-order chromatic aberration is insufficient, which is undesirable. In order to effectively correct first-order chromatic aberration, the refractive power of the negative lens Gn1 must be increased, which is undesirable because it becomes difficult to achieve both high performance and lightweight design.

[0046] Here, the partial dispersion ratio θgF is expressed as follows, where Nd, NF, NC, and Ng are the refractive indices at the Fraunhofer d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm). θgF=(Nd-Ng) / (NF-NC) It is expressed as:

[0047] Conditional expression (13) defines the refractive index of the material of the negative lens Gn2. If the upper limit of conditional expression (13) is exceeded and the refractive index of the material of the negative lens Gn2 becomes high, the specific gravity of the negative lens Gn2 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the lower limit of conditional expression (13) is exceeded and the refractive index of the material of the negative lens Gn2 becomes low, the Petzval sum becomes large on the negative side, which is undesirable because it causes a large negative curvature of field. Condition (14) defines the Abbe number of the material of the negative lens Gn2.

[0048] If the Abbe number exceeds the upper limit of conditional expression (14) and becomes large, it becomes difficult to reduce the weight, which is undesirable. In a telephoto optical system, the lens configuration arranged on the image side has a negative refractive power as a whole. Therefore, by increasing the Abbe number of the negative lens on the image side, it becomes easy to suppress the occurrence of lateral chromatic aberration. If the Abbe number becomes small below the lower limit of conditional expression (14), it becomes difficult to correct lateral chromatic aberration, which is undesirable. Furthermore, it is possible to disperse the negative refractive power of the negative lens Gn2 by arranging multiple negative lenses that satisfy conditional expressions (13) and (14). This makes it easy to correct distortion.

[0049] Conditional expression (15) defines the refractive index of the material of the negative lens Gn3. By appropriately setting the refractive index of the material of the negative lens Gn3, the weight of the optical system L0 can be reduced and curvature of field can be reduced. If the upper limit of conditional expression (15) is exceeded and the refractive index of the material of the negative lens Gn3 becomes high, the specific gravity of the negative lens Gn3 increases, making it difficult to reduce the weight of the optical system L0, which is undesirable. If the lower limit of conditional expression (15) is exceeded and the refractive index of the material of the negative lens Gn3 becomes low, the Petzval sum becomes large on the negative side, which is undesirable because significant curvature of field occurs on the negative side.

[0050] Conditional expression (16) defines the Abbe number of the material of the negative lens Gn3. By satisfying conditional expression (16), both weight reduction and correction of lateral chromatic aberration of the optical system L0 are achieved. To correct lateral chromatic aberration, it is preferable to increase the partial dispersion ratio θgF of the negative lens, which is positioned relatively closer to the image and where the height of the chief ray of the off-axis light beam passing through the lens increases. If the Abbe number of the material of the negative lens Gn3 increases beyond the upper limit of conditional expression (16), the partial dispersion ratio θgF becomes too small. This makes it difficult to correct second-order chromatic aberration, which is undesirable. If the Abbe number of the material of the negative lens Gn3 decreases below the lower limit of conditional expression (16), it makes it difficult to correct first-order chromatic aberration, which is undesirable. Attempting to correct this would require increasing the number of lenses constituting the optical system L0, which is undesirable because it would make it difficult to reduce the weight of the optical system L0.

[0051] Conditional expression (17) defines the ratio between the focal length of the positive lens Gp1 and the focal length of the optical system L0. By satisfying conditional expression (17), both a compact size and high optical performance of the optical system L0 are achieved. If the upper limit of conditional expression (17) is exceeded and the focal length of the positive lens Gp1 becomes long, it becomes difficult to achieve a telephoto type refractive power arrangement. This makes it difficult to compact the optical system L0, which is undesirable. If the lower limit of conditional expression (17) is exceeded and the focal length of the positive lens Gp1 becomes short and the refractive power of the positive lens Gp1 becomes strong, it becomes difficult to correct lateral chromatic aberration, axial chromatic aberration, etc., which is undesirable.

[0052] Conditional expression (18) defines the aspherical amount of the positive lens Gp1. If the aspherical amount becomes large enough to exceed the upper limit of conditional expression (18), it becomes difficult to process the positive lens Gp1, making manufacturing difficult, which is undesirable. If the aspherical amount becomes small enough to fall below the lower limit of conditional expression (18), it becomes difficult to correct spherical aberration and coma, which is undesirable.

[0053] Conditional expression (19) defines the shape factor (shape) of the positive lens Gp1. A larger shape factor results in a stronger meniscus shape, which is advantageous for aberration correction but disadvantageous for weight reduction. If the value of the shape factor increases beyond the upper limit of conditional expression (19), the shape of the positive lens Gp1 will be a meniscus shape with a large waist. This makes it difficult to reduce the weight of the positive lens Gp1, which is undesirable. If the value of the shape factor decreases below the lower limit of conditional expression (19), the positive lens Gp1 will be a biconvex lens with a large thickness in the optical axis direction. This results in large spherical aberration and coma, which are undesirable because their correction will be difficult.

[0054] Conditional expression (20) defines the ratio of the focal length of the first lens group B1 to the focal length of the optical system L0. If the upper limit of conditional expression (20) is exceeded, the focal length of the first lens group B1 becomes long and the refractive power of the first lens group B1 becomes weak, which is undesirable because the overall lens length of the optical system L0 becomes long and it becomes difficult to make the optical system L0 compact. If the lower limit of conditional expression (20) is exceeded, the focal length of the first lens group B1 becomes short and the refractive power of the first lens group B1 becomes strong, which is undesirable because it becomes difficult to correct various aberrations.

[0055] Conditional expression (21) defines the relationship between the axial distance from the image-side surface of the positive lens Gp1 to the positive lens Gp2 and the overall lens length of the optical system L0. Satisfying conditional expression (21) achieves both compactness and lightweighting of the optical system L0. If the upper limit of conditional expression (21) is exceeded and the distance between the positive lens Gp1 and the positive lens Gp2 becomes wider, the overall lens length becomes longer, which is undesirable. If the distance between the positive lens Gp1 and the positive lens Gp2 becomes narrower and the lower limit of conditional expression (21) is exceeded, the diameter of the positive lens Gp2, which is located on the object side and has a relatively large luminous flux diameter, becomes larger. This makes it difficult to reduce the weight of the optical system L0, which is undesirable.

[0056] Conditional expression (22) defines the maximum value for the height (ray height) of the incident point of an axial ray when passing through the aspherical surface of the positive lens Gp1 when focusing on an object at infinity. To fully utilize the aberration correction effect of the aspherical surface, the ray height of the axial ray passing through the aspherical surface must be relatively large. If the ray height is too small, below the lower limit, spherical aberration correction will be insufficient, making it difficult to achieve high image quality, which is undesirable. If the ray height is too large, above the upper limit, the effective diameter of the aspherical surface will increase, making it difficult to achieve a lightweight lens, which is undesirable. It is more preferable that the numerical ranges of the conditional expressions (3) to (22) be within the ranges of the following conditional expressions (3a) to (22a). 1.495 <Ndp1<1.650 ···(3a) 60.00<νdp1<82.0 (4a) 1.420 <Ndp2<1.550 ···(5a) 70.0<νdp2<96.0 (6a) 1.420 <Ndp3<1.550 ···(7a) 70.0<νdp3<96.0 (8a) 1.420 <Ndp4<1.550 ···(9a) 80.0<νdp4<95.5 (10a) 1.700 <Ndn1<1.900 ···(11a) 22.0<νdn1<32.0 (12a) 1.420 <Ndn2<1.550 ···(13a) 70.0<νdn2<95.5 (14a) 1.850 <Ndn3<2.100 ···(15a) 16.0<νdn3<21.0 (16a) 0.20 <f1 / f<1.00 ···(17a) 0.00010 <DRGp1×Fno / f<0.00100 ···(18a) 0.30<(rp2+rp1) / (rp2-rp1)<1.50 (19a) 0.40 <f11 / f<1.20 ···(20a) 0.30 <d12 / f11<0.55 ···(21a) 30 <YASPH<100 ···(22a) It is more preferable that the numerical ranges of the conditional expressions (3) to (22) be the numerical ranges of the following conditional expressions (3b) to (22b). 1.585 <Ndp1<1.620 ···(3b) 62.0<νdp1<70.0 (4b) 1.430 <Ndp2<1.510 ···(5b) 80.0<νdp2<95.5 (6b) 1.430 <Ndp3<1.510 ···(7b) 80.0<νdp3<95.5 (8b) 1.430 <Ndp4<1.520 ···(9b) 90.0<νdp4<95.0 (10b) 1,800 <Ndn1<1.860 ···(11b) 24.0<νdn1<26.0 (12b) 1.430 <Ndn2<1.510 ···(13b) 80.0<νdn2<95.0 (14b) 1.920 <Ndn3<2.050 ···(15b) 17.0<νdn3<19.0 (16b) 0.30 <f1 / f<0.95 ···(17b) 0.00020 <DRGp1×Fno / f<0.00090 ···(18b) 0.40<(rp2+rp1) / (rp2-rp1)<1.21 (19b) 0.50 <f11 / f<0.90 ···(20b) 0.40 <d12 / f11<0.52 ···(21b) 40 <YASPH<80 ···(22b)

[0057] Next, the optical system L0 of each embodiment will be described in detail. In the optical systems L0 according to Examples 1 to 8, the first lens group B1 and the third lens group B3 do not move during focusing, and only the second lens group B2 moves during focusing. In other words, the optical system L0 is an optical system in which the spacing between adjacent lens groups changes during focusing.

[0058] The optical system L0 of Example 1 comprises, arranged in order from the object side to the image side, a first lens unit B1 with positive refractive power, a second lens unit B2 with positive refractive power, and a third lens unit B3 with negative refractive power. In the optical system L0 of Example 1, the second lens unit B2 moves toward the object side during focusing from an object at infinity to an object at the closest distance. The object-side surface of the positive lens Gp1, which is arranged closest to the object side of the optical system L0, is aspheric.

[0059] The optical system L0 of Examples 2 to 6 comprises, arranged in order from the object side to the image side, a first lens unit B1 with positive refractive power, a second lens unit B2 with negative refractive power, and a third lens unit B3 with positive refractive power. In the optical system L0 of Examples 2 to 6, the second lens unit B2 moves toward the image side during focusing from an object at infinity to an object at the closest distance. The object-side surface of the positive lens Gp1, arranged closest to the object side of the optical system L0, is aspheric.

[0060] The optical system L0 of Example 7 comprises, arranged in order from the object side to the image side, a first lens unit B1 with positive refractive power, a second lens unit B2 with negative refractive power, and a third lens unit B3 with negative refractive power. In the optical system L0 of Example 7, the second lens unit B2 moves toward the image side during focusing from an object at infinity to an object at the closest distance. The object-side surface of the positive lens Gp1, which is arranged closest to the object side of the optical system L0, is aspheric.

[0061] The optical system L0 of Example 8 comprises, arranged in order from the object side to the image side, a first lens unit B1 with positive refractive power, a second lens unit B2 with positive refractive power, and a third lens unit B3 with negative refractive power. In the optical system L0 of Example 8, the second lens unit B2 moves toward the object side during focusing from an object at infinity to an object at the closest distance. The image-side surface of the positive lens Gp1, which is arranged closest to the object side of the optical system L0, is aspheric.

[0062] In the optical system L0 of Examples 1 to 8, the four lenses counting from the object side are, in order from the object side to the image side, a positive lens Gp1, a positive lens Gp2, a negative lens Gn1, and a positive lens Gp3, which are arranged consecutively, thereby achieving a compact size of the optical system L0 and reducing the occurrence of various aberrations such as spherical aberration.

[0063] The third lens group B3 has a positive lens Gp4, and negative lenses Gn2 and Gn3 arranged on the image side of the positive lens Gp4. In the optical systems L0 of Examples 1 to 3 and 8, the negative lens Gn2 is arranged closer to the object than the negative lens Gn3. In the optical systems L0 of Examples 4 to 7, the negative lens Gn3 is arranged closer to the object than the negative lens Gn2. This achieves the effect of reducing the size of the optical system L0 and reduces the occurrence of various aberrations such as distortion.

[0064] The aperture diaphragm SP may be located on the object side or the image side of the second lens group B2. When the aperture diaphragm SP is located on the image side of the second lens group B2, as in the optical systems L0 of Examples 1, 4, and 7, it becomes easy to reduce the diameter of the aperture diaphragm SP, and it becomes possible to reduce the size of the lens apparatus including the optical system L0. When the aperture diaphragm SP is located on the object side of the second lens group B2, as in the optical systems L0 of Examples 2, 3, 5, 6, and 8, it becomes easy to ensure the amount of peripheral light when the aperture diaphragm SP is set to a small aperture state.

[0065] In Examples 1, 2, and 4 to 7, the third lens group B3 has a flat plate with an infinite radius of curvature on both sides, so that the overall lens length and the like do not change even if the user inserts a filter such as an ND filter instead of the flat plate.

[0066] In the optical system L0 of Examples 1 to 8, all surfaces having refractive power are constructed as refractive surfaces. Compared to a case where surfaces are constructed from diffractive optical elements or reflective surfaces, optical performance equal to or better than that of a case where surfaces are constructed from diffractive optical elements or reflective surfaces can be easily obtained with a lower manufacturing difficulty.

[0067] In the optical system L0 of Examples 1 to 8, image blur correction may be reduced by moving a part of the optical system L0 in a direction including a component perpendicular to the optical axis. In particular, by making the part that moves during image blur correction part of the third lens group, which has a relatively small diameter, it is possible to make the actuator for driving it compact, and to reduce the size of the lens device including the optical system L0.

[0068] Numerical Examples 1 to 8 corresponding to Examples 1 to 8, respectively, are shown below. In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial distance (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. Also, nd represents the refractive index of each optical element with respect to the d-line, and vd represents the Abbe number of the optical element with respect to the d-line. The definition of the Abbe number is as described above.

[0069] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values ​​when the optical system L0 of each example is focused on an object at infinity. The back focus BF is the air-equivalent value of the distance from the final lens surface (the surface closest to the image) of the optical system L0 to the image plane. The total lens length of the optical system L0 is the value obtained by adding the back focus to the distance from the first lens surface to the final lens surface.

[0070] If the optical surface is aspherical, an asterisk (*) is added to the right of the surface number. The aspherical shape is expressed as follows: X is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10, and A12 are the aspherical coefficients of each order. x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 In addition, "e±XX" in each aspherical coefficient is "×10 ±XX " means.

[0071] Furthermore, values ​​corresponding to conditional expressions (1) to (22) in Numerical Examples 1 to 8 are shown in [Table 1].

[0072] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1* 280.819 13.31 1.59349 67.0 2 -662.008 155.41 3 83.002 10.00 1.43387 95.1 4 2343.445 0.20 5 246.274 1.70 1.85478 24.8 6 51.565 1.83 7 52.263 11.35 1.43387 95.1 8 705.477 9.27 9 52.406 5.29 1.89286 20.4 10 105.791 0.30 11 76.403 1.50 1.65412 39.7 12 31.854 13.02 1.43875 94.7 13 -2658.460 2.00 14 668.114 1.20 1.83481 42.7 15 41.557 18.61 16 (Aperture) ∞ 2.10 17 -336.337 2.76 1.43875 94.7 18 -67.619 1.00 19 228.172 3.68 1.80518 25.5 20 -75.220 1.30 1.69680 55.5 21 53.781 3.35 22 -81.585 1.20 1.61800 63.4 23 118.400 3.46 24 87.428 2.72 1.84666 23.8 25 -507.253 3.50 26 ∞ 2.00 1.51633 64.1 27∞15.47 28 -362.217 6.49 1.66565 35.6 29 -36.199 1.70 1.43875 94.7 30 63.962 6.24 31 92.212 10.06 1.66565 35.6 32 -39.445 1.20 1.94595 18.0 33 -263.530 0.20 34 53.267 2.86 1.72047 34.7 35 79.604 54.90 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4=-1.72042e-008 A 6=-1.87003e-013 A 8= 2.28183e-018 A 10=-8.44369e-023 Focal length 390.15 F-number 2.91 Half angle of view (°) 3.17 Image height 21.64 Lens total length 371.16 BF 54.90 Lens group data Group starting plane focal length 1 1 321.47 2 9 91.31 3 14 -127.61

[0073] [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1* 188.273 11.23 1.59349 67.0 2 -503.174 94.27 3 57.957 11.11 1.43387 95.1 4 -689.601 0.20 5 260.836 1.70 1.85478 24.8 6 38.276 1.73 7 39.048 8.19 1.43387 95.1 8 135.287 7.88 9 46.526 5.01 1.89286 20.4 10 135.378 0.30 11 72.225 1.50 1.80420 46.5 12 30.248 7.75 1.43875 94.7 13 188.650 2.00 14 (Aperture) ∞ 1.94 15 2244.521 1.10 1.63854 55.4 16 36.994 11.20 17 115.338 3.47 1.43875 94.7 18 -76.882 1.00 19 834.139 2.43 1.92286 20.9 20 -87.993 1.30 1.56384 60.7 21 39.072 3.03 22 -73.039 1.20 1.72916 54.7 23 70.746 2.70 24 68.806 3.09 1.51742 52.4 25 -259.482 10.02 26 ∞ 2.00 1.51633 64.1 27∞2.00 28 86.337 8.70 1.61340 44.3 29 -41.712 1.70 1.43875 94.7 30 47.340 0.75 31 51.354 9.49 1.66565 35.6 32 -54.505 1.20 1.94595 18.0 33 -624.434 52.99 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4=-5.28832e-008 A 6=-1.45196e-012 A 8= 2.18686e-017 A 10=-7.31885e-021 Focal length 292.50 F-number 2.91 Half angle of view (°) 4.23 Image height 21.64 Lens length 274.19 BF 52.99 Lens group data Group starting plane focal length 1 1 121.78 2 15 -58.92 3 17 233.37

[0074] [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1* 204.916 17.53 1.49700 81.5 2 -560.323 155.11 3 55.653 11.71 1.43387 95.1 4 -906.488 0.30 5 603.672 1.80 1.85478 24.8 6 39.895 0.61 7 40.089 10.35 1.43387 95.1 8 274.117 7.48 9 46.770 7.05 1.89286 20.4 10 305.115 0.20 11 171.992 1.50 1.80400 46.5 12 30.980 8.16 1.43875 94.7 13 225.443 1.74 14 (Aperture) ∞ 1.00 15 966.501 1.30 1.74320 49.3 16 45.459 20.37 17 328.466 2.73 1.51742 52.4 18 -94.698 2.00 19 129.182 4.24 1.80610 33.3 20 -54.881 1.40 1.53775 74.7 21 42.446 4.86 22 -58.304 1.40 1.76385 48.5 23 59.365 2.69 24 61.179 7.92 1.66565 35.6 25 -39.245 1.70 1.43875 94.7 26 83.633 3.65 27 72.159 8.81 1.66565 35.6 28 -40.604 1.80 1.94595 18.0 29 -506.009 15.98 30 83.596 3.31 1.85478 24.8 31 263.097 38.43 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4=-2.26814e-008 A 6=-5.40105e-013 A 8= 3.39277e-018 A 10=-9.95340e-022 Focal length 390.15 F-number 2.91 Half angle of view (°) 3.17 Image height 21.64 Lens length 347.13 BF 38.43 Lens group data Group starting plane focal length 1 1 167.04 2 15 -64.22 3 17 199.83

[0075] [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd 1* 219.655 10.73 1.61800 63.4 2 -3012.869 163.50 3 59.914 10.02 1.43387 95.1 4 4865.272 0.20 5 589.841 1.80 1.85478 24.8 6 47.637 0.20 7 47.187 8.26 1.43387 95.1 8 298.427 21.03 9 46.798 5.01 1.89286 20.4 10 165.350 0.30 11 115.172 1.50 1.80420 46.5 12 30.444 6.97 1.43875 94.7 13 136.906 2.00 14 806.974 1.20 1.83481 42.7 15 57.417 15.24 16 150.735 3.00 1.43875 94.7 17 -116.306 2.00 18 ∞ 4.80 19 111.695 3.63 1.80000 29.8 20 -77.218 1.30 1.69680 55.5 21 46.019 2.84 22 -83.070 1.20 1.72916 54.7 23 124.163 5.23 24 36.314 4.53 1.54814 45.8 25 604.977 2.18 26 ∞ 2.00 1.51633 64.1 27 ∞ 16.44 28 132.934 4.41 1.61340 44.3 29 -64.251 1.20 1.59522 67.7 30 28.401 0.20 31 28.442 12.13 1.66565 35.6 32 -31.162 1.20 1.94595 18.0 33 -156.312 2.51 34 -45.608 1.40 1.43875 94.7 35 98.837 4.97 1.66565 35.6 36 -71.558 2.68 37 -32.000 1.60 1.49700 81.6 38 -61.495 55.61 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4=-8.02700e-009 A 6=-1.86355e-013 A 8= 2.89947e-018 A 10=-7.42167e-022 Focal length 489.84 F-number 4.12 Half angle of view (°) 2.53 Image height 21.64 Lens total length 385.02 BF 55.61 Lens group data Group starting plane focal length 1 1 189.17 2 14 -74.10 3 16 712.80

[0076] [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd 1* 224.322 10.73 1.61700 62.8 2 -2298.790 162.69 3 60.451 10.02 1.43387 95.1 4 3457.269 0.20 5 470.680 1.80 1.85478 24.8 6 47.276 0.43 7 47.033 8.32 1.43387 95.1 8 285.083 18.88 9 (Aperture) ∞ 2.00 10 47.188 4.96 1.89286 20.4 11 160.551 0.30 12 109.879 1.50 1.80420 46.5 13 30.776 6.91 1.43875 94.7 14 133.954 2.00 15 982.964 1.20 1.83481 42.7 16 57.866 16.29 17 165.576 2.99 1.43875 94.7 18 -110.306 6.71 19 114.097 3.62 1.80000 29.8 20 -76.911 1.30 1.69680 55.5 21 46.536 2.81 22 -84.720 1.20 1.72916 54.7 23 121.397 4.81 24 36.775 4.45 1.54814 45.8 25 697.080 2.15 26 ∞ 2.00 1.51633 64.1 27∞17.17 28 130.003 4.29 1.61340 44.3 29 -68.119 1.20 1.59522 67.7 30 28.425 0.20 31 28.460 12.04 1.66565 35.6 32 -31.688 1.20 1.94595 18.0 33 -164.733 2.36 34 -45.396 1.40 1.43875 94.7 35 99.036 5.09 1.66565 35.6 36 -68.698 2.50 37 -32.793 1.60 1.49700 81.6 38 -65.842 55.71 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4=-8.67032e-009 A 6=-1.93063e-013 A 8= 3.23293e-018 A 10=-7.35981e-022 Focal length 489.83 F-number 4.12 Half angle of view (°) 2.53 Image height 21.64 Lens total length 385.02 BF 55.71 d14 2.00 d16 16.29 d38 55.71 Lens group data Group starting plane focal length 1 1 186.72 2 15 -73.70 3 17 762.73

[0077] [Numerical Example 6] Unit: mm Surface Data Surface number rd nd νd 1* 285.093 12.55 1.59349 67.0 2 -1479.042 190.55 3 69.072 11.87 1.43387 95.1 4 685.012 0.20 5 228.115 1.80 1.85478 24.8 6 53.787 3.19 7 54.922 9.82 1.43387 95.1 8 244.661 12.90 9 56.988 6.15 1.89286 20.4 10 143.410 0.30 11 106.556 1.50 1.80420 46.5 12 36.998 11.01 1.43875 94.7 13 287.228 2.00 14 (Aperture) ∞ 1.89 15 2060.029 1.20 1.83481 42.7 16 63.704 31.52 17 288.621 3.43 1.43875 94.7 18 -91.977 4.37 19 151.454 2.98 2.00069 25.5 20 -154.501 1.30 1.72916 54.7 21 48.458 3.45 22 -92.062 1.20 1.72916 54.7 23 97.879 2.62 24 74.517 3.90 1.71736 29.5 25 -99.598 0.45 26 -80.109 1.20 1.92286 20.9 27 -120.673 15.00 28 125.923 6.79 1.61340 44.3 29 -32.480 1.20 1.59522 67.7 30 49.025 0.20 31 43.296 6.42 1.66565 35.6 32 -72.016 1.20 1.94595 18.0 33 151.132 2.00 34 ∞ 2.00 1.51633 64.1 35∞27.40 36 153.921 1.40 1.43875 94.7 37 57.557 5.17 1.66565 35.6 38 -437.624 2.66 39 -60.164 1.60 1.49700 81.6 40 -204.792 55.69 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4=-6.76072e-009 A 6=-8.09258e-014 A 8= 9.85458e-019 A 10=-1.39258e-022 Various data Zoom ratio 1.00 Focal length 584.73 F-number 4.12 Half angle of view (°) 2.12 Image height 21.64 Lens total length 452.08 BF 55.69 Lens group data Group starting plane focal length 1 1 185.15 2 15 -78.77 3 17 4600.69

[0078] [Numerical Example 7] Unit: mm Surface Data Surface number rd nd νd 1* 225.654 11.32 1.59349 67.0 2 2469.202 184.69 3 98.977 12.83 1.43387 95.1 4 -192.506 0.20 5 -220.566 1.80 1.85478 24.8 6 164.470 1.00 7 83.667 7.41 1.43387 95.1 8 565.944 18.66 9 90.641 5.20 1.89286 20.4 10 2008.811 0.41 11 -10922.623 1.20 1.80420 46.5 12 46.022 8.57 1.43875 94.7 13 676.931 2.00 14 646.937 1.62 1.80420 46.5 15 98.935 50.26 16 (Aperture) ∞ 22.00 17 207.606 2.09 1.43875 94.7 18 -167.383 1.00 19 103.573 2.85 2.00069 25.5 20 -153.956 1.76 1.72916 54.7 21 42.557 2.86 22 -79.511 1.62 1.72916 54.7 23 92.583 2.50 24 59.043 2.74 1.62588 35.7 25 -388.216 2.00 26 138.802 4.36 1.66565 35.6 27 -35.745 1.20 1.59522 67.7 28 52.963 0.20 29 49.235 5.06 1.66565 35.6 30 -45.137 1.20 1.94595 18.0 31 554.146 2.00 32 ∞ 2.00 1.51633 64.1 33∞30.69 34 147.955 5.79 1.51742 52.4 35 -35.983 1.20 1.59522 67.7 36 -227.566 1.85 37 -50.132 2.00 1.49700 81.5 38 -99.040 82.90 Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4=-6.52695e-010 A 6=-2.94089e-014 A 8= 6.84453e-019 A 10=-4.68155e-022 Focal length 789.82 F-number 5.88 Half angle of view (°) 1.57 Image height 21.64 Lens total length 489.04 BF 82.90 Lens group data Group starting plane focal length 1 1 240.54 2 14 -145.43 3 16 -245.69

[0079] [Numerical Example 8] Unit: mm Surface Data Surface number rd nd νd 1 217.301 13.28 1.59349 67.0 2* -3954.670 153.07 3 123.739 11.90 1.43387 95.1 4 -164.195 0.28 5 -159.815 2.00 1.85478 24.8 6 196.442 0.20 7 91.799 12.22 1.43387 95.1 8 -143.545 0.20 9 -151.037 2.10 1.80420 46.5 10 686.188 3.66 11 70.494 9.66 1.43387 95.1 12 -1026.781 0.20 13 74.990 2.20 1.56040 44.7 14 42.795 11.82 15 (Aperture) ∞ 11.42 16 60.563 5.77 1.66305 33.7 17 522.937 4.40 18 96.483 4.00 1.84666 23.8 19 -496.627 1.50 1.79576 44.7 20 38.172 5.68 21 99.376 4.45 1.84666 23.8 22 -106.119 1.10 1.66368 49.0 23 58.316 2.94 24 -153.332 1.10 1.74914 51.9 25 73.206 4.58 26 34.594 3.64 1.49700 81.5 27 76.678 1.18 28 239.545 1.10 1.98493 30.2 29 44.613 4.78 1.84666 23.8 30 -375.542 18.48 31 -48.459 1.10 1.43875 94.7 32 25.822 11.79 1.62004 36.3 33 -267.592 0.20 34 61.776 11.45 1.61340 44.3 35 -34.301 1.10 1.95906 17.5 36 -117.040 12.31 37 -28.824 1.10 1.94595 18.0 38 -42.636 (variable) Image plane 32.32 Aspheric data 2nd side K = 0.00000e+000 A 4= 4.49620e-009 A 6=-4.48946e-014 A 8=-9.10918e-018 A 10= 8.90247e-022 Focal length 390.15 F-number 2.91 Half angle of view (°) 3.17 Image height 21.64 Lens length 370.27 BF 32.32 Lens group data Group starting plane focal length 1 1 361.39 2 16 102.79 3 18 -55.59 [Table 1]

[0080] [Example of imaging device] Next, an embodiment of the imaging device will be described with reference to FIG. 17. FIG. 17 is a diagram showing the configuration of an imaging device 10. The imaging device 10 includes a camera body 13, a lens device 11 including an optical system L0 according to any one of the first to eighth embodiments described above, and an imaging element (light receiving element) 12 that photoelectrically converts an image formed by the optical system L0. An imaging element such as a CCD sensor or a CMOS sensor can be used as the imaging element 12. The lens device 11 and the camera body 13 may be configured as an integrated unit, or may be configured as detachable elements. The imaging device 10 of this embodiment is small and lightweight, and can achieve high optical performance.

[0081] The imaging device according to the embodiment of the present invention is not limited to the digital still camera shown in FIG. 17, but can be applied to various imaging devices such as broadcast cameras, cameras for silver halide film, and surveillance cameras.

[0082] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various combinations, modifications, and alterations are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0083] L0 optical system IP image plane Gp1 positive lens Gn1 negative lens

Claims

1. An optical system having one or more positive lenses and one or more negative lenses, a positive lens Gp1 is a positive lens arranged closest to the object side among the one or more positive lenses, and a negative lens Gn1 is a negative lens arranged closer to the image side than the positive lens Gp1 and arranged closest to the object side among the one or more negative lenses, At least one of the object-side surface and the image-side surface of the positive lens Gp1 is aspherical, When the total lens length of the optical system is LD, the focal length of the optical system is f, the distance on the optical axis from the image-side surface of the positive lens Gp1 to the object-side surface of the negative lens Gn1 is Dpn, the radius of curvature of the object-side surface of the positive lens Gp1 is rp1, the radius of curvature of the image-side surface of the positive lens Gp1 is rp2, and the focal length of the positive lens Gp1 is f11, 0.20<LD / f<1.00 0.382<Dpn / LD<0.800 0.10<(rp2+rp1) / (rp2-rp1)≦0.8958 0.20<f11 / f≦0.8906 An optical system characterized by satisfying the following conditional expression:

2. When the refractive index of the material of the positive lens Gp1 with respect to the d-line is Ndp1 and the Abbe number based on the d-line is νdp1, 1.493<Ndp1<1.700 55.0<νdp1<96.0 2. The optical system according to claim 1, wherein the following condition is satisfied:

3. When the optical system has two or more positive lenses, and the second positive lens among the two or more positive lenses counting from the object side is a positive lens Gp2, and the refractive index of the material of the positive lens G2 with respect to the d-line is Ndp1, and the Abbe number based on the d-line is νdp2, 1.400<Ndp2<1.630 61.0<νdp2<96.0 3. The optical system according to claim 1, wherein the following condition is satisfied:

4. When the optical system has three or more positive lenses, and the third positive lens among the three or more positive lenses counting from the object side is designated as a positive lens Gp3, and the refractive index of the material of the positive lens G3 with respect to the d-line is designated as Ndp3, and the Abbe number based on the d-line is designated as νdp3, then: 1.400<Ndp3<1.630 61.0<νdp3<96.0 4. The optical system according to claim 1, wherein the following condition is satisfied:

5. When the optical system has four or more positive lenses, and the positive lens Gp4 is located closer to the image side than the positive lens Gp3 that is located third from the object side among the four or more positive lenses, and the refractive index of the material of the positive lens Gp4 with respect to the d-line is Ndp4 and the Abbe number based on the d-line is νdp4, 1.400<Ndp4<1.630 50.0<νdp4<96.0 5. The optical system according to claim 1, wherein the following condition is satisfied:

6. When the refractive index of the material of the negative lens Gn1 with respect to the d-line is Ndn1 and the Abbe number based on the d-line is νdn1, 1.600<Ndn1<1.950 20.0<νdn1<50.0 6. The optical system according to claim 1, wherein the following condition is satisfied:

7. 7. The optical system according to claim 1, comprising, arranged in order from the object side to the image side, a first lens group having positive refractive power that does not move during focusing, a second lens group having positive or negative refractive power that moves during focusing, and a third lens group having positive or negative refractive power that does not move during focusing.

8. 8. The optical system according to claim 7, wherein the optical system has four or more positive lenses, and when a positive lens Gp4 is defined as a positive lens that is located on the image side of a positive lens Gp3 that is located third from the object side among the four or more positive lenses, the third lens group has the positive lens Gp4 and a negative lens that is located on the image side of the positive lens Gp4.

9. The third lens group has a negative lens Gn2 arranged closer to the image than the positive lens Gp4, and when the refractive index of the material of the negative lens Gn2 with respect to the d-line is Ndn2 and the Abbe number with respect to the d-line as the reference is νdn2, then: 1.400<Ndn2<1.630 61.0<νdn2<96.0 9. The optical system according to claim 8, wherein the following condition is satisfied:

10. The third lens group has a negative lens Gn3 arranged closer to the image than the positive lens Gp4, and when the refractive index of the material of the negative lens Gn3 with respect to the d-line is Ndn3 and the Abbe number with respect to the d-line as the reference is νdn3, then: 1.800<Ndn3<2.200 14.0<νdn3<24.0 10. The optical system according to claim 8, wherein the following condition is satisfied:

11. When the focal length of the first lens group is f1, 0.10<f1 / f<1.20 11. The optical system according to claim 7, wherein the following condition is satisfied:

12. the second lens group has a positive refractive power, and the third lens group has a negative refractive power; 12. The optical system according to claim 7, wherein the second lens group moves toward the object during focusing from an object at infinity to a closest object.

13. the second lens group has negative refractive power, and the third lens group has positive refractive power; 12. The optical system according to claim 7, wherein the second lens group moves toward the image side during focusing from an object at infinity to an object at the closest distance.

14. the second lens group has negative refractive power, the third lens group has negative refractive power, 12. The optical system according to claim 7, wherein the second lens group moves toward the image side during focusing from an object at infinity to an object at the closest distance.

15. 15. The optical system according to claim 7, wherein the second lens group is composed of three or less lenses.

16. When the aspherical amount at 70% of the effective diameter of the aspherical surface is DRGp1 and the F-number of the optical system is Fno, 0.00001<DRGp1×Fno / f<0.00500 16. The optical system according to claim 1, wherein the following condition is satisfied:

17. The optical system has two or more positive lenses, and the second positive lens among the two or more positive lenses, counting from the object side, is designated as a positive lens Gp2. When the distance on the optical axis from the image side surface of the positive lens Gp1 to the object side surface is designated as d12 and the focal length of the positive lens Gp1 is designated as f11, 0.20<d12 / f11<0.60 17. The optical system according to claim 1, wherein the following condition is satisfied:

18. When the maximum height of the incident point of an axial ray on the aspherical surface when focusing on an object at infinity is YASPH (mm), 30<YASPH<100 18. The optical system according to claim 1, wherein the following condition is satisfied:

19. 19. The optical system according to claim 1, comprising the positive lens Gp1, the positive lens Gp2, the negative lens Gn1, and the positive lens Gp3, which are arranged in succession in this order from the most object side to the image side.

20. 20. The optical system according to claim 1, wherein the aspherical surface has a shape in which negative refractive power increases from the vertex toward the periphery.

21. 21. An imaging device comprising: the optical system according to claim 1; and an imaging element that receives an image formed by the optical system.

Images