Optical system and imaging device having the same

Abstract

To provide a compact, light-weight optical system that offers high optical performance by appropriately setting refractive indices and power arrangement of lenses.SOLUTION: An optical system L0 provided herein comprises a first lens L1 with positive refractive power located on the most object side and a final lens Lr with positive refractive power located on the most image side, and satisfies the following conditional expressions: 0.05<f1 / fr<1.0, 1.64<PNdave<2.10, 1.4<TTL / ftanω<3.2, where f1 represents a focal length of the first lens, fr represents a focal length of the final lens, PNdave represents an average refractive index of materials of all positive lenses included in the optical system for the d-line, f represents a focal length of the optical system, TTL represents an optical axial distance from an object-side surface of the first lens to a paraxial image plane using a back focus as an air-equivalent length, and ω represents a half angle of view (°).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system and is suitable for digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and the like. [Background technology]

[0002] In recent years, imaging devices have become smaller, and the image sensors used in these devices have become higher pixel counts. With the miniaturization and increased pixel count of image sensors, the optical systems used in imaging devices are required to have high optical performance, be small and lightweight. Patent Document 1 discloses an optical system that satisfies these requirements, consisting of six lenses: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens, arranged in order from the object side to the image side. The first lens is a positive refractive power lens with a convex surface facing the object side near the optical axis. The second lens is a negative refractive power lens with a concave surface facing the image side near the optical axis. The third lens is a lens with a convex surface facing the object side near the optical axis. The fourth lens is a lens with a convex surface facing the image side near the optical axis. The fifth lens is a lens with a convex surface facing the object side near the optical axis. The sixth lens is a lens with a concave surface facing the image side near the optical axis. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-115174 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] To miniaturize the optical system, it is effective to adopt a telephoto-type power configuration, increasing both the positive refractive power on the object side and the negative refractive power on the image side. However, increasing the negative refractive power on the image side causes significant distortion, making it difficult to correct both distortion and field curvature with a limited number of lenses.

[0005] The optical system described in Patent Document 1 corrects distortion and field curvature by using multiple aspherical lenses. However, because the Petzval sum of the entire system is large, there are challenges in correcting field curvature when applying it to imaging devices with large sensor sizes.

[0006] The present invention aims to provide a compact and lightweight optical system with high optical performance by appropriately setting the refractive index and power distribution of each lens. [Means for solving the problem]

[0007] One aspect of the present invention is the optical system, An optical system comprising a first lens, an aperture diaphragm, a second lens, a third lens, a fourth lens, a fifth lens, and a final lens, arranged in order from the object side to the image side, wherein the focal length of the first lens is f1, the focal length of the final lens is fr, the average refractive index of all positive lenses in the optical system at the d line is PNdave, the focal length of the optical system is f, the distance along the optical axis from the lens surface on the object side of the first lens to the image plane, with the back focus being the air equivalent length, is TTL, and the imaging half-angle of view (°) corresponding to the maximum image height of the optical system is ω, 0.05 <f1 / fr<1.0 1.64 <PNdave<2.10 1.4 <TTL / (f×tanω)<3.2 It is characterized by satisfying the following conditional expression.

[0008] Other objects and features of the present invention are described in the following embodiments. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an optical system that has high optical performance and is small and lightweight. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view of the optical system of Example 1. [Figure 2] This is an aberration diagram for Example 1 when the object is in focus at infinity. [Figure 3] This is a cross-sectional view of the optical system of Example 2. [Figure 4] This is an aberration diagram for Example 2 when the object is in focus at infinity. [Figure 5] This is a cross-sectional view of the optical system of Example 3. [Figure 6] This is an aberration diagram for Example 3 when the object is in focus at infinity. [Figure 7] This is a cross-sectional view of the optical system of Example 4. [Figure 8] It is an aberration diagram at infinity focus in Example 4. [Figure 9] It is a cross-sectional view of the optical system of Example 5. [Figure 10] It is an aberration diagram at infinity focus in Example 5. [Figure 11] It is a schematic diagram of the imaging device.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the optical system of the present invention and an imaging device having the same will be described based on the accompanying drawings. In each figure, the same members are denoted by the same reference numerals, and overlapping descriptions are omitted.

[0012] FIG. 1, FIG. 3, FIG. 5, FIG. 7, and FIG. 9 are cross-sectional views of the optical systems L0 of Examples 1 to 5, respectively. The optical system L0 of each embodiment is an optical system used in an imaging device such as a digital video camera, a digital still camera, a broadcast camera, a silver salt film camera, and a surveillance camera.

[0013] In each lens cross-sectional view, the left side is the object side and the right side is the image side. The optical system L0 of each embodiment is configured with a plurality of lenses. L1 represents the lens disposed on the most object side among the lenses included in the optical system L0. Lr represents the lens disposed on the most image side among the lenses included in the optical system L0.

[0014] In each lens cross-sectional view, "Li" (i is a natural number) represents the "i-th lens" when the lenses constituting the optical system L0 are counted in order from the object side to the image side.

[0015] SP is an aperture diaphragm. IP is the image plane, and when the optical system L0 of each embodiment is used as the shooting optical system of a digital still camera or digital video camera, the image plane of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed on it. When the optical system L0 of each embodiment is used as the shooting optical system of a silver halide film camera, a photosensitive surface corresponding to the film plane is placed on the image plane IP.

[0016] Furthermore, by moving the entire optical system L0 along the optical axis, focusing is achieved from an object point at infinity to an object point at a close distance.

[0017] Furthermore, in the optical system L0 of each embodiment, one or more lenses may be eccentrically positioned to include a component perpendicular to the optical axis during image shake correction, thereby providing a vibration-damping optical system. Additionally, a parallel plate with virtually no refractive power, such as a low-pass filter or an infrared cut filter, may be placed between the lens positioned closest to the image and the imaging plane.

[0018] Figures 2, 4, 6, 8, and 10 are aberration diagrams of the optical systems L0 of Examples 1 to 5 when they are in focus at infinity.

[0019] In the spherical aberration diagram, Fno is the F-number and indicates the amount of spherical aberration for the d-line (wavelength 587.56 nm) and the g-line (wavelength 435.84 nm). In the astigmatism diagram, dS indicates the amount of astigmatism at the sagittal image plane, and dM indicates the amount of astigmatism at the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration at the g-line is shown. ω is the half-angle of view (°).

[0020] Next, we will describe the characteristic configuration of the optical system L0 in each embodiment.

[0021] The optical system L0 of each embodiment includes a first lens L1 with positive refractive power positioned closest to the object and a final lens Lr with positive refractive power positioned closest to the image.

[0022] Furthermore, the optical system L0 of each embodiment satisfies the following condition (1) when the focal length of the first lens L1 is f1 and the focal length of the final lens Lr is fr.

[0023] 0.05 <f1 / fr<1.0 ···(1) Conditional equation (1) specifies the ratio of the focal length of the first lens L1 to the focal length of the final lens Lr. If the refractive power of the first lens L1 weakens beyond the upper limit of conditional equation (1), it becomes difficult to maintain the telephoto power arrangement, and the overall optical length increases, which is undesirable. If the refractive power of the final lens Lr weakens below the lower limit of conditional equation (1), pincushion distortion becomes insufficiently corrected, and it becomes difficult to achieve both field curvature and distortion, which is undesirable.

[0024] Furthermore, the optical system L0 of each embodiment satisfies the following condition (2), where PNdave is the average refractive index of all positive lens materials included in the optical system L0 at the d-line (wavelength 587.56 nm).

[0025] 1.64 <PNdave<2.10 ···(2) Condition (2) specifies the average refractive index of the positive lenses included in the optical system L0. If the refractive index is higher than the upper limit of condition (2), the dispersion of colors will increase, making it difficult to correct axial chromatic aberration, which is undesirable. If the refractive index is lower than the lower limit of condition (2), the Petzval sum of the optical system L0 will increase, making it difficult to correct field curvature, which is also undesirable.

[0026] Furthermore, in each embodiment, the optical system L0 satisfies the following condition (3), where f is the focal length of the optical system L0, TTL is the distance along the optical axis from the object-side lens surface of the first lens L1 (with air equivalent length as the back focus) to the image plane IP (paraxial), and ω is the half-angle of view (°). The half-angle of view may be defined as the half-angle of view of light that is imaged at the edge of the image circle of the optical system L0, or as the half-angle of view of light that is imaged at the maximum image height of the image sensor of the imaging device on which the optical system L0 is mounted.

[0027] 1.4 <TTL / (f×tanω)<3.2 ···(3) Condition (3) defines the total optical length of the optical system L0. Exceeding the upper limit of condition (3) is undesirable because it increases the total optical length. If the total optical length falls below the lower limit of condition (3), it becomes shorter, which is undesirable because it increases the telephoto power distribution, making it difficult to achieve both field curvature and distortion.

[0028] Furthermore, it is preferable that the numerical ranges of conditional expressions (1) to (3) be the numerical ranges of the following conditional expressions (1a) to (3a).

[0029] 0.10 <f1 / fr<0.95 ···(1a) 1.64 <PNdave<1.90 ···(2a) 1.7 <TTL / (f×tanω)<3.2 ···(3a) Furthermore, it is even more preferable to set the numerical ranges of conditional expressions (1) to (3) to the numerical ranges of the following conditional expressions (1b) to (3b).

[0030] 0.15 <f1 / fr<0.92 ···(1b) 1.64 <PNdave<1.85 ···(2b) 1.9 <TTL / (f×tanω)<3.1 ···(3b) Next, we will describe the conditions and configurations that are preferable for the optical system L0 of each embodiment to satisfy. It is preferable that the optical system L0 of each embodiment satisfies one or more of the following conditions (4) to (9) and the following configurations.

[0031] The optical system L0 of each embodiment preferably satisfies the following condition (4).

[0032] 0.6 <f1 / f<2.0 ···(4) Conditional equation (4) specifies the ratio of the focal length of the first lens L1 to the focal length of the optical system L0. If the refractive power of the first lens L1 weakens beyond the upper limit of conditional equation (4), it becomes difficult to maintain the telephoto power arrangement, and the overall optical length increases, which is undesirable. If the refractive power of the first lens L1 strengthens below the lower limit of conditional equation (4), pincushion distortion increases, and it becomes difficult to achieve both field curvature and distortion, which is undesirable.

[0033] The optical system L0 of each embodiment preferably satisfies the following condition (5).

[0034] 0.8 <fr / f<8.0 ···(5) Conditional equation (5) specifies the ratio of the focal length of the final lens Lr to the focal length of the optical system L0. If the refractive power of the final lens Lr becomes weaker than the upper limit of conditional equation (5), pincushion distortion will not be adequately corrected, making it difficult to achieve both field curvature and distortion, which is undesirable. If the refractive power of the final lens Lr becomes stronger than the lower limit of conditional equation (5), it will be difficult to maintain the telephoto power arrangement, and the overall optical length will increase, which is also undesirable.

[0035] In each embodiment, the optical system L0 preferably satisfies the following condition (6), where sk is the distance along the optical axis (air-equivalent length) from the image-side lens surface of the final lens Lr to the image plane IP.

[0036] 0.2 <sk / f<0.5 ···(6) Conditional equation (6) specifies the ratio of the back focus to the focal length of the optical system L0. If the back focus is too long, exceeding the upper limit of conditional equation (6), the overall optical length will increase, which is undesirable. If the back focus is too short, falling below the lower limit of conditional equation (6), the shadows of foreign objects attached to the lens will be more likely to appear in the photograph, which is also undesirable.

[0037] In each embodiment, the optical system L0 preferably satisfies the following condition (7), where SPIP is the distance along the optical axis from the aperture diaphragm SP (with the back focus equivalent to the length of air) to the image plane IP (paraxial).

[0038] 0.60 <SPIP / TTL<0.95 ···(7) Conditional equation (7) specifies the ratio of the position of the aperture diaphragm SP to the total optical length. If the position of the aperture diaphragm SP is on the object side, exceeding the upper limit of conditional equation (7), vignetting bias is likely to occur, resulting in an abnormal shape of the bokeh, which is undesirable. If the position of the aperture diaphragm SP is on the image side, below the lower limit of conditional equation (7), the angle of off-axis light rays incident on the image plane IP becomes large, making shading by the image sensor more likely, which is also undesirable.

[0039] In each embodiment, it is preferable that the optical system L0 has the aperture diaphragm SP positioned adjacent to the image side of the first lens L1.

[0040] In each embodiment, the optical system L0 preferably has a lens Ln with negative refractive power to correct chromatic aberration and field curvature.

[0041] In each embodiment, the optical system L0 preferably satisfies the following condition (8) when the object-side paraxial curvature radius of the negative refractive power lens Ln is R1 and the image-side paraxial curvature radius is R2.

[0042] 1.0<(R1+R2) / (R2-R1)<100.0 (8) Conditional equation (8) defines the shape of lens Ln. If the values ​​of R1 and R2 approach each other beyond the upper limit of conditional equation (8), the refractive power of lens Ln weakens, resulting in insufficient correction of chromatic aberration, which is undesirable. If the values ​​fall below the lower limit of conditional equation (8), lens Ln becomes a biconcave lens, making it difficult to achieve both field curvature and distortion, which is also undesirable.

[0043] In each embodiment, the optical system L0 preferably satisfies the following condition, where Ndn is the refractive index of lens Ln at the d line and νdn is the Abbe number.

[0044] Ndn<4.19450 / νdn+1.52010 ···(9) Conditional equation (9) specifies the refractive index of lens Ln. If the refractive index of the negative lens Ln is large, exceeding the upper limit of conditional equation (9), the Petzval sum of the optical system L0 becomes large, making it difficult to correct for field curvature, which is undesirable.

[0045] Furthermore, it is more preferable to use the numerical ranges of the following conditional expressions (4) to (9) as the numerical ranges of conditional expressions (4a) to (9a).

[0046] 0.64 <f1 / f<1.50 ···(4a) 0.90 <fr / f<6.00 ···(5a) 0.24 <sk / f<0.45 ···(6a) 0.65 <SPIP / TTL<0.90 ···(7a) 1.0<(R1+R2) / (R2-R1)<50.0 (8a) Ndn<4.19450 / νdn+1.48010 ···(9a) Furthermore, it is even more preferable to use the numerical ranges of the following conditional expressions (4) to (9) as the numerical ranges of the conditional expressions (4b) to (9b).

[0047] 0.68 <f1 / f<1.20 ···(4b) 0.90 <fr / f<4.20 ···(5b) 0.28 <sk / f<0.39 ···(6b) 0.69 <SPIP / TTL<0.90 ···(7b) 2.0<(R1+R2) / (R2-R1)<10.0 (8b) Ndn<4.19450 / νdn+1.45710 ···(9b) In order to achieve both high optical performance and miniaturization, the optical system L0 of each embodiment is preferably composed of 5 to 8 lenses. In other words, the optical system L0 of each embodiment preferably has 3 or more lenses with positive refractive power and 2 or more lenses with negative refractive power, and the total number of lenses included in the optical system L0 is preferably 8 or less.

[0048] Note that cover glass and IR cut filters are not considered lenses, and cover glass and IR cut filters may be placed on the object side of the first lens L1 in the optical system L0 of each embodiment, or between the final lens Lr and the image plane IP. Furthermore, the refractive power of the lens represents the refractive power near the optical axis (paraxial). Here, near the optical axis is the paraxial region, and in the case of an aspherical lens, the concave and convex surfaces near the optical axis are defined by the sign of the paraxial radius of curvature. Similarly, the sign of the refractive power is also calculated from the paraxial radius of curvature.

[0049] Next, the optical system L0 of each embodiment will be described in detail.

[0050] The optical system L0 of Example 1 consists of a first lens L1, an aperture diaphragm SP, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6, arranged in order from the object side to the image side. The first lens L1 has a positive refractive power. The second lens L2 has a positive refractive power. The third lens L3 has a negative refractive power. The fourth lens L4 has a negative refractive power near the optical axis. The fifth lens L5 has a positive refractive power near the optical axis. The sixth lens L6 has a positive refractive power near the optical axis. The fourth lens L4 is lens Ln, and the sixth lens is the final lens Lr. The fourth lens L4 has aspherical surfaces formed on both sides, with the object-side surface facing the object side near the optical axis as a concave surface, and the image-side surface facing the image side near the optical axis as a convex surface. The fifth lens L5 has aspherical surfaces formed on both sides, with the object-side surface facing the object near the optical axis as a concave surface, and the image-side surface facing the image near the optical axis as a convex surface. The sixth lens L6 has aspherical surfaces formed on both sides, with the object-side surface facing the object near the optical axis as a convex surface, and the image-side surface facing the image near the optical axis as a concave surface.

[0051] The optical system L0 of Example 2 consists of a first lens L1, a second lens L2, an aperture diaphragm SP, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7, arranged in order from the object side to the image side. The first lens L1 has a positive refractive power. The second lens L2 has a negative refractive power. The third lens L3 has a negative refractive power. The fourth lens L4 has a positive refractive power. The fifth lens L5 has a negative refractive power near the optical axis. The sixth lens L6 has a negative refractive power near the optical axis. The seventh lens L7 has a positive refractive power near the optical axis. The sixth lens L6 is lens Ln, and the seventh lens is the final lens Lr. The fifth lens L5 has aspherical surfaces formed on both sides, with the object-side surface facing the object side near the optical axis and the image-side surface facing the image side near the optical axis. The sixth lens L6 has aspherical surfaces formed on both sides, with the object-side surface facing the object near the optical axis as a concave surface, and the image-side surface facing the image near the optical axis as a convex surface. The seventh lens L7 has aspherical surfaces formed on both sides, with the object-side surface facing the object near the optical axis as a convex surface, and the image-side surface facing the image near the optical axis as a concave surface.

[0052] The optical system L0 of Example 3 consists of a first lens L1, an aperture diaphragm SP, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6, arranged in order from the object side to the image side. The first lens L1 has a positive refractive power. The second lens L2 has a negative refractive power. The third lens L3 has a positive refractive power. The fourth lens L4 has a negative refractive power near the optical axis. The fifth lens L5 has a negative refractive power near the optical axis. The sixth lens L6 has a positive refractive power. The fifth lens L5 is lens Ln, and the sixth lens is the final lens Lr. The fourth lens L4 has aspherical surfaces formed on both sides, with the object-side surface facing the object side near the optical axis and the image-side surface facing the image side near the optical axis. The fifth lens, L5, has aspherical surfaces formed on both sides. The object-side surface faces the object side concavely near the optical axis, while the image-side surface faces the image side convex near the optical axis.

[0053] The optical system L0 of Example 4 consists of a first lens L1, an aperture diaphragm SP, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7, arranged in order from the object side to the image side. The first lens L1 has a positive refractive power. The second lens L2 has a negative refractive power. The third lens L3 has a positive refractive power. The fourth lens L4 has a negative refractive power near the optical axis. The fifth lens L5 has a negative refractive power. The sixth lens L6 has a negative refractive power near the optical axis. The seventh lens has a positive refractive power. The sixth lens L6 is lens Ln, and the seventh lens is the final lens Lr. The fourth lens L4 has aspherical surfaces formed on both sides, with the object-side surface facing the object side near the optical axis as a concave surface, and the image-side surface facing the image side near the optical axis as a convex surface. The sixth lens, L6, has aspherical surfaces formed on both sides; the object-side surface faces the object side concave near the optical axis, while the image-side surface faces the image side convex near the optical axis.

[0054] The optical system L0 of Example 5 consists of a first lens L1, a second lens L2, an aperture diaphragm SP, a third lens L3, a fourth lens L4, and a fifth lens L5, arranged in order from the object side to the image side. The first lens L1 has a positive refractive power. The second lens L2 has a negative refractive power near the optical axis. The third lens L3 has a negative refractive power near the optical axis. The fourth lens L4 has a positive refractive power near the optical axis. The fifth lens L5 has a positive refractive power near the optical axis. The third lens L3 is lens Ln, and the fifth lens is the final lens Lr. The second lens L2 has aspherical surfaces formed on both sides, with the object-side surface facing the object side near the optical axis and the image-side surface facing the image side near the optical axis. The third lens L3 has aspherical surfaces on both sides, with the object-side surface facing the object near the optical axis as a concave surface, and the image-side surface facing the image near the optical axis as a convex surface. The fourth lens L4 has aspherical surfaces on both sides, with the object-side surface facing the object near the optical axis as a concave surface, and the image-side surface facing the image near the optical axis as a convex surface. The fifth lens L5 has aspherical surfaces on both sides, with the object-side surface facing the object near the optical axis as a convex surface, and the image-side surface facing the image near the optical axis as a concave surface.

[0055] The numerical Examples 1 to 5 corresponding to Examples 1 to 5 are shown below.

[0056] 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 m-th 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 with respect to the d-line of each optical member, and νd represents the Abbe number of the optical member. The Abbe number νd of a certain material is calculated as follows when the refractive indices at the d-line (587.56 nm), F-line (486.13 nm), and C-line (656.27 nm) of the Fraunhofer lines are Nd, NF, and NC: νd=(Nd - 1) / (NF - NC) and is represented by the following formula.

[0057] In each numerical example, d, focal length (mm), F-number, and half angle (°) are all values when the optical system L0 of each example is focused on an infinite object. "Back focus" represents the distance on the optical axis from the final surface of the lens (the lens surface closest to the image side) to the paraxial image plane, expressed in terms of the air-equivalent length. "Total lens length" is the length obtained by adding the back focus to the distance on the optical axis from the front surface of the optical system L0 (the lens surface closest to the object side) to the final surface.

[0058] When the optical surface is an aspherical surface, an asterisk (*) is attached to the right side of the surface number. The aspherical shape is expressed as follows when X is the displacement amount 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, A12, and A14 are the aspherical coefficients of each order: x=(h 2 / R) / [1 + {1 - (1 + k)(h / R) 2}^(1 / 2)] + A4×h 1 / 2 ^2 + A6×h 4 ^3 + A8×h 6 ^4 + A10×h 8 ^5 + A12×h 10 ^6 + A14×h 12 ^7 14 Here, "e±XX" in each aspherical coefficient means "×10±..."XX It means "...".

[0059] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd 1 6.329 0.74 1.80400 46.5 2 13.054 0.95 3 (aperture) ∞ 0.39 4 5.899 0.99 1.90043 37.4 5 -105.473 0.39 1.76182 26.5 6 4.159 2.09 7* -8.544 0.66 1.67070 19.3 8* -25.539 0.54 9* -7.071 1.28 1.63560 23.9 10* -5.018 0.49 11* 7.499 1.90 1.53500 56.0 12* 9.164 5.12 Image plane ∞ Aspherical data Side 7 K = 0.00000e+000 A 4=-1.30571e-002 A 6= 1.07357e-003 A 8= 1.13910e-006 A10=-3.23336e-006 A12=-1.01049e-006 Side 8 K = 0.00000e+000 A 4=-1.05055e-002 A 6= 1.04691e-003 A 8=-3.89159e-005 A10=-5.44432e-007 A12= 2.59956e-008 9th page K = 0.00000e+000 A 4= 8.11468e-003 A 6=-6.75729e-004 A 8= 3.07488e-005 A10=-1.29401e-007 A12=-2.06278e-008 Side 10 K = 0.00000e+000 A 4= 3.89314e-003 A 6= 1.26901e-004 A 8=-2.57098e-005 A10= 1.67415e-006 A12=-3.50220e-008 Page 11 K = 0.00000e+000 A 4=-6.73863e-003 A 6= 2.57932e-004 A 8=-4.04258e-006 A10=-1.83896e-008 A12= 1.37821e-009 A14=-1.37275e-011 Side 12 K = 0.00000e+000 A 4=-6.31402e-003 A 6= 2.43612e-004 A 8=-8.06405e-006 A10= 1.82462e-007 A12=-2.06718e-009 A14= 7.83470e-012 Focal length 13.40 F-number 2.88 Half-angle (°): 30.49 Image height 7.89 Lens length: 15.54 BF 5.12 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd 1 8.917 1.75 1.72916 54.7 2 53.474 1.59 3 110.968 0.40 1.76182 26.5 4 15.775 1.86 5 (aperture) ∞ 1.09 6 -14.365 0.40 1.63980 34.5 7 6.486 1.82 1.90043 37.4 8 -17.168 0.34 9* 9.476 0.89 1.61550 25.8 10* 6.491 3.00 11* -4.673 1.83 1.67070 19.3 12* -6.154 0.16 13* 9.059 2.54 1.53110 56.0 14* 16.292 5.33 Image plane ∞ Aspherical data 9th page K = 0.00000e+000 A 4=-1.47605e-003 A 6=-7.24096e-005 A 8= 1.67984e-006 A10=6.08218e-009 A12=-6.41411e-010 Side 10 K = 0.00000e+000 A 4=-7.98986e-004 A 6=-8.47257e-005 A 8= 4.35324e-006 A10=-1.17355e-007 A12= 1.16124e-009 Page 11 K = 0.00000e+000 A 4= 4.71331e-003 A 6=-2.39662e-004 A 8= 1.71673e-005 A10=-6.14369e-007 A12= 9.63727e-009 Side 12 K = 0.00000e+000 A 4= 1.60831e-003 A 6=-6.73267e-005 A 8= 4.14213e-006 A10=-1.33308e-007 A12= 1.38871e-009 Page 13 K =-9.93925e+000 A 4=-6.74925e-004 A 6= 4.38677e-006 A 8= 7.67983e-007 A10=-3.63317e-008 A12= 6.50603e-010 A14=-4.11880e-012 Side 14 K =-4.54666e+001 A 4=-3.65548e-004 A 6=-2.35017e-005 A 8= 1.25198e-006 A10=-3.17708e-008 A12= 3.87238e-010 A14=-1.78166e-012 Focal length 18.21 F-number 2.06 Half-angle (°): 23.43 Image height 7.89 Lens length: 22.99 BF 5.33 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd 1 4.707 1.13 1.61800 63.4 2 9.145 1.07 3 (aperture) ∞ 0.88 4 -13.939 0.40 1.60342 38.0 5 4.094 1.49 1.85150 40.8 6 -10.702 0.16 7* -20.317 0.92 1.63560 23.9 8* 16.176 2.24 9* -2.684 1.11 1.67070 19.3 10* -4.213 0.07 11 144.002 2.21 1.90366 31.3 12 -15.708 4.19 Image plane ∞ Aspherical data Side 7 K = 0.00000e+000 A 4=-4.18307e-003 A 6= 1.49689e-003 A 8=-8.47348e-004 A10= 2.67501e-004 A12=-3.97751e-005 A14= 2.16051e-006 Side 8 K = 0.00000e+000 A 4=-2.16772e-003 A 6= 5.73321e-004 A 8=-1.35772e-004 A10= 2.41817e-005 A12=-1.37987e-006 A14=-9.50059e-009 9th page K =-4.70448e+000 A 4=-2.76003e-002 A 6= 5.61591e-003 A 8=-1.38408e-003 A10= 2.30576e-004 A12=-2.32076e-005 A14= 9.79590e-007 Side 10 K = 0.00000e+000 A 4= 1.27980e-003 A 6= 5.55638e-005 A 8=-5.37022e-006 A10= 9.26509e-007 A12=-6.95746e-008 A14= 2.53834e-009 Focal length 12.64 F-number 2.91 Half-angle (°): 31.97 Image height 7.89 Lens length: 15.87 BF 4.19 [Numerical Example 4] Unit: mm Surface data Face number rd nd νd 1 4.508 1.10 1.69680 55.5 2 10.717 1.00 3 (aperture) ∞ 1.02 4 -13.463 0.40 1.69895 30.1 5 4.776 1.39 1.83481 42.7 6 -9.237 0.16 7* -16.299 0.43 1.53110 55.9 8* -187.887 1.34 9 -2.854 0.86 1.92286 20.9 10 -4.834 0.42 11* -4.029 0.55 1.53110 55.9 12* -5.433 0.15 13 132.002 2.50 2.00100 29.1 14 -13.257 4.19 Image plane ∞ Aspherical data Side 7 K = 0.00000e+000 A 4=-8.03294e-003 A 6= 6.42603e-004 A 8=-1.71864e-005 A10=-2.18210e-005 A12= 5.95829e-006 A14=-3.26994e-007 Side 8 K = 0.00000e+000 A 4=-9.37478e-003 A 6= 5.54245e-004 A 8=-6.69460e-005 A10=-6.99311e-006 A12= 1.91513e-006 A14=-4.31530e-008 Page 11 K = 0.00000e+000 A 4= 2.04929e-003 A 6= 2.43258e-004 A 8=-7.52984e-005 A10= 7.10962e-006 A12=-4.53349e-007 A14= 1.70146e-008 Side 12 K = 0.00000e+000 A 4= 2.56257e-003 A 6= 2.07946e-004 A 8=-4.35551e-005 A10= 3.28693e-006 A12=-1.10371e-007 A14= 1.45867e-009 Focal length 12.94 F-number 2.80 Half-angle (°): 31.36 Image height 7.89 Lens length: 15.50 BF 4.19 [Numerical Example 5] Unit: mm Surface data Face number rd nd νd 1 7.954 2.78 1.80400 46.5 2 25.319 1.00 3* 7.414 1.00 1.68040 18.1 4* 4.296 2.33 5 (aperture) ∞ 3.25 6* -12.993 1.26 1.68040 18.1 7* -25.239 0.58 8* -6.219 2.12 1.53110 56.0 9* -4.485 0.12 10* 7.640 1.98 1.61550 25.8 11* 8.146 7.26 Image plane ∞ Aspherical data 3rd page K =-2.58067e+000 A 4=-5.41202e-004 A 6= 1.94663e-005 A 8=-2.43063e-006 A10= 2.31169e-007 A12=-1.06694e-008 A14= 1.86696e-010 Page 4 K = 0.00000e+000 A 4=-1.88087e-003 A 6= 4.04775e-007 A 8=-5.28924e-006 A10= 4.48328e-007 A12=-2.58274e-008 Page 6 K = 0.00000e+000 A 4=-3.19421e-003 A 6=-2.59784e-005 A 8=-1.24961e-005 A10= 7.53563e-007 A12=-3.76179e-008 Page 7 K = 0.00000e+000 A 4=-2.65156e-003 A 6= 6.08301e-005 A 8=-8.76121e-006 A10= 7.51566e-007 A12=-3.23701e-008 A14= 5.11926e-010 Page 8 K = 0.00000e+000 A 4= 2.03003e-003 A 6=-8.06286e-005 A 8= 1.42128e-005 A10=-7.91272e-007 A12= 2.01159e-008 A14=-1.92473e-010 Page 9 K =-7.27163e-001 A 4= 7.57285e-004 A 6= 1.03175e-006 A 8= 8.75017e-007 A10=-7.26569e-008 A12= 3.48036e-009 A14=-4.91632e-011 Side 10 K = 0.00000e+000 A 4=-2.01129e-003 A 6= 1.04519e-004 A 8=-4.91147e-006 A10= 1.28533e-007 A12=-1.80303e-009 A14= 9.55073e-012 Page 11 K = 0.00000e+000 A 4=-2.92697e-003 A 6= 1.56717e-004 A 8=-6.57509e-006 A10= 1.63168e-007 A12=-2.23969e-009 A14= 1.25036e-011 Focal length 19.42 F-number 1.85 Half-angle (°): 22.11 Image height 7.89 Lens length: 23.68 BF 7.26 The various values ​​in each numerical example are summarized in Table 1 below.

[0060] TIFF0007853001000001.tif45158

[0061] [Imaging device] Next, an example of a digital still camera (imaging device) 10 using the optical system L0 of each embodiment as the imaging optical system will be described with reference to Figure 11. In Figure 11, 13 is the camera body, and 11 is the imaging optical system composed of one of the optical systems L0 described in Examples 1 to 5. 12 is a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor, which is built into the camera body 13 and receives the optical image formed by the imaging optical system 11 and converts it into photoelectric light. The camera body 13 may be a so-called single-lens reflex camera with a quick-turn mirror, or a so-called mirrorless camera without a quick-turn mirror.

[0062] By applying the optical system L0 of each embodiment to an imaging device such as a digital still camera, an imaging device with a compact lens can be obtained.

[0063] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various combinations, modifications, and changes are possible within the scope of its essence. [Explanation of Symbols]

[0064] L1 First Lens Lr final lens

Claims

1. An optical system comprising a first lens, an aperture diaphragm, a second lens, a third lens, a fourth lens, a fifth lens, and a final lens, arranged in order from the object side to the image side, When the focal length of the first lens is f1, the focal length of the final lens is fr, the average refractive index of all positive lens materials in the optical system at the d line is PNdave, the focal length of the optical system is f, the distance on the optical axis from the object-side lens surface of the first lens to the image plane is TTL (with the back focus as the air equivalent length), and the imaging half-angle of view (°) corresponding to the maximum image height of the optical system is ω, 0.05<f1 / fr<1.0 1.64<PNdave<2.10 1.4<TTL / (f×tanω)<3.2 An optical system characterized by satisfying the following conditional equation.

2. 1.7188 ≤ PNdave < 2.10 The optical system according to claim 1, characterized in that it satisfies the following condition.

3. 0.6<f1 / f<2.0 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. 0.8<fr / f<8.0 An optical system according to any one of claims 1 to 3, characterized in that it satisfies the following conditional expression.

5. When sk is the air-equivalent length of the distance along the optical axis from the image-side lens surface of the final lens to the image surface, 0.2<sk / f<0.5 An optical system according to any one of claims 1 to 4, characterized in that it satisfies the following conditional expression.

6. When SPIP is defined as the distance along the optical axis from the aperture diaphragm to the image plane, with the back focus being the air equivalent length, 0.60<SPIP / TTL<0.95 An optical system according to any one of claims 1 to 5, characterized in that it satisfies the following conditional expression.

7. The optical system according to any one of claims 1 to 6, further comprising an aperture diaphragm arranged adjacent to the image side of the first lens.

8. When R1 is the object-side paraxial radius of curvature of the negative refractive power lens positioned on the object side of the final lens, and R2 is the image-side paraxial radius of curvature of the negative refractive power lens, 1.0<(R1+R2) / (R2-R1)<100.0 The optical system according to claim 1, characterized in that it satisfies the following condition.

9. An imaging device characterized by having an optical system according to any one of claims 1 to 8, and an image sensor that receives an image formed by the optical system.

Images