Optical system and imaging device having the same

Abstract

To provide a compact optical system with high optical performance. [Solution] An optical system having a front group with negative refractive power, an aperture diaphragm, and a rear group with positive refractive power, arranged in order from the object side to the image side, wherein the optical system has at least 8 lenses, the rear group includes an aspherical lens having an inflection point, and the maximum image height of the optical system is ImgH, the total optical length of the optical system is L, the focal length of the front group is f1, the focal length of the first lens G1 located furthest towards the object in the front group is fG1, and the focal length of the entire optical system is f. The specified condition must be satisfied.

Description

[Technical Field]

[0001] The disclosures herein relate to optical systems and are suitable for digital still cameras, digital video cameras, surveillance cameras, in-vehicle cameras, smartphone cameras, and the like. [Background technology]

[0002] In wide-angle optical systems, there is a demand for a compact design while maintaining high optical performance. Patent Document 1 discloses a wide-angle optical system in which a front lens group with negative refractive power, an aperture diaphragm, and a rear lens group with positive refractive power are arranged in that order from the object side. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-184065 [Overview of the project] [Problems that the invention aims to solve]

[0004] To realize an optical system that is compact yet possesses high optical performance, it is necessary to appropriately set the refractive power and arrangement of the lenses that make up the optical system. [Means for solving the problem]

[0005] One aspect of the present invention is an optical system having a front group with negative refractive power, an aperture diaphragm, and a rear group with positive refractive power, arranged in order from the object side to the image side, wherein the optical system has at least 8 lenses, the rear group includes an aspherical lens having an inflection point, and when the maximum image height of the optical system is ImgH, the total optical length of the optical system is L, the focal length of the front group is f1, and the focal length of the lens G1 located furthest towards the object in the front group is fG1, 0.40 <ImgH / L 0.52 <fG1 / f1 -2.98 <f1 / f<0.00 It is characterized by satisfying the following conditional expression.

[0006] Furthermore, as another aspect of the present invention, the optical system is an optical system having a front group with negative refractive power, an aperture diaphragm, and a rear group with positive refractive power, arranged in order from the object side to the image side, wherein the optical system has an aspherical lens with an inflection point, the front group includes two or more lenses, and when the maximum image height of the optical system is ImgH and the total optical length of the optical system is L, 0.40 <ImgH / L It is characterized by satisfying the following conditional expression. [Effects of the Invention]

[0007] This makes it possible to provide a compact optical system with high optical performance. [Brief explanation of the drawing]

[0008] [Figure 1] Cross-sectional view of the optical system of Example 1 at infinity focus. [Figure 2] Longitudinal aberration diagram corresponding to Example 1 [Figure 3] Cross-sectional view of the optical system of Example 2 at infinity focus. [Figure 4] Longitudinal aberration diagram corresponding to Example 2 [Figure 5] Cross-sectional view of the optical system of Example 3 at infinity focus. [Figure 6] Longitudinal aberration diagram corresponding to Example 3 [Figure 7] Cross-sectional view of the optical system of Example 4 at infinity focus. [Figure 8] Longitudinal aberration diagram corresponding to Example 4 [Figure 9] Schematic diagram of sag amount in the first lens G1 [Figure 10] Schematic diagram of the hit point of off-axis rays on an optical surface. [Figure 11] Schematic diagram of an imaging device using the optical systems of Examples 1 to 4 [Figure 12] Schematic diagram of a lens device using the optical systems of Examples 1 to 4 [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant descriptions are omitted.

[0010] FIGS. 1, 3, 5, and 7 are cross-sectional views of the optical system L0 at infinity focus in Examples 1 to 4, respectively. The optical system L0 of each example is used in an imaging device such as a digital still camera, a digital video camera, a surveillance camera, or an in-vehicle camera.

[0011] In each cross-sectional view, the left side is the object side and the right side is the image side. The optical system L0 of each example has a plurality of lens groups. Note that the lens group in this specification refers to a collection of lenses separated by the aperture stop SP. Also, each lens group may be composed of one lens or a plurality of lenses. Further, each lens group may include an aspherical lens, a Fresnel lens, a metalens, a diffractive optical element, and the like.

[0012] In the optical system L0 of each example, Li represents the i-th (i is a natural number) lens group counted from the object side among the lens groups included in the optical system L0. Also, Gk represents the k-th (k is a natural number) lens counted from the object side among the lenses included in the optical system.

[0013] In the optical system L0 of each example, L1 (LF) represents the front group as a lens group disposed on the object side of the aperture stop. Also, L2 (LR) represents the rear group as a lens group disposed on the image side of the aperture stop.

[0014] In each cross-sectional view, SP is the aperture diaphragm. FL is an optical element corresponding to an optical filter, low-pass filter, infrared cut filter, etc. IP is the image plane, and when the optical system L0 of each embodiment is used as the imaging optical system of a digital still camera or digital video camera, the imaging plane of a solid-state image sensor such as a CCD sensor or CMOS sensor is positioned there. When the optical system L0 of each embodiment is used as the imaging optical system of a silver halide film camera, the image plane IP becomes the photosensitive surface corresponding to the film plane. The optical system of each embodiment may also be used as a projection lens for a projector, etc. In this case, the left side is the screen side, and the right side is the projected image side.

[0015] Figures 2, 4, 6, and 8 are aberration diagrams of the optical systems L0 of Examples 1 to 4 at infinity focus, respectively. In each figure, spherical aberration, astigmatism, distortion, and chromatic aberration are shown from left to right. In the spherical aberration diagram, Fno. is the F number, the solid line shows the amount of spherical aberration with respect to the d line (wavelength 587.6 nm), and the dashed line shows the amount of spherical aberration with respect to the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line shows the amount of field curvature of the sagittal image plane, and the dashed line shows the amount of field curvature of the meridional image plane. In the distortion aberration diagram, the solid line shows the amount of distortion with respect to the d line. In the chromatic aberration diagram, the dashed line shows the chromatic aberration at the g line. Also, ω is the half-angle of view [°].

[0016] Figure 9 is a cross-sectional view of the front group L1 in the optical system L0 of each of the embodiments 1 to 4. In Figure 9, Ea represents the effective diameter of the first lens G1, and Sag represents the distance in the optical axis direction between the vertex of the surface of the first lens G1 and the effective diameter position.

[0017] Here, we will explain the off-axis focal lengths used in each embodiment. The off-axis focal length is the focal length of an off-axis ray that is incident on the optical axis at an angle ω[°] relative to the optical axis, passes through the center of the aperture diaphragm SP, and forms an image on the image side, when the maximum half-angle of view of the optical system L0 with an on-axis focal length of f0 is ω[°].

[0018] Figure 10 shows the method for calculating the off-axis focal length. In Figure 10, Gi is an optical surface such as a lens surface, and the direction of the optical axis on the optical surface is defined as the Z direction. Of the directions perpendicular to the Z direction, two mutually orthogonal directions are defined as the X direction and the Y direction. When the Z direction is parallel to the horizontal direction, the X direction is also parallel to the horizontal direction, and the Y direction is parallel to the vertical direction.

[0019] In Figure 10, the intersection point of the on-axis ray and the optical surface Gi is defined as hp_0. The intersection point of the off-axis ray incident at the maximum field of view ω[°] and the optical surface Gi is defined as the hit point hp_ω. Calculating the curvature near the off-axis principal ray at the hit point hp_ω reveals that this curvature differs depending on the azimuth angle. As described in Reference 1 below, the focal length for the off-axis principal ray can be determined by calculating the curvature at the hit point. (Reference 1) Keisuke Araki, "Development of Non-Coaxial Optical Systems for Imaging Systems," Optics, The Optical Society of Japan, June 2008, Vol. 37, No. 6, pp. 334-339.

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

[0021] The optical system L0 in each embodiment has, in order from the object side, a front group L1 with negative refractive power, an aperture diaphragm SP, and a rear group L2. Because the front group L1 has negative refractive power, the optical system L0 has a so-called retrofocus type configuration, so the principal point is located on the image side and back focus can be secured. In addition, the optical system L0 can be miniaturized in the radial direction.

[0022] The optical system L0 of each embodiment includes an aspherical lens. Furthermore, in the optical system L0 of each embodiment, the lens surface of the aspherical lens included in the rear group L2 has an inflection point. An inflection point on the lens surface is a point where the sign of the refractive power of the lens changes from near the optical axis to the periphery of the lens surface. By including an aspherical lens with an inflection point, image field distortion and astigmatism can be effectively corrected.

[0023] As an example of an aspherical lens with an inflection point, the object-side lens surface of the aspherical lens is convex towards the object near the optical axis and concave towards the object at the periphery. Similarly, the image-side lens surface of the aspherical lens is concave towards the image near the optical axis and convex towards the image at the periphery. This allows for correction of Petzval sum near the optical axis while correcting astigmatism at the periphery. Furthermore, the object-side lens surface of the aspherical lens may be concave towards the object near the optical axis and convex towards the object at the periphery. Similarly, the image-side lens surface of the aspherical lens may be concave towards the image near the optical axis and convex towards the image at the periphery.

[0024] Furthermore, the optical system L0 of each embodiment is characterized in that, when the maximum image height of the optical system L0 is ImgH and the total optical length is L, the following condition (1) is satisfied. 0.40 <ImgH / L (1)

[0025] Condition (1) specifies the ratio of the maximum image height to the total optical length of the optical system L0. Here, the maximum image height of the optical system L0 refers to the distance from the position on the optical axis where the peripheral light intensity is 10% when the position on the optical axis is defined as having 100% light intensity, to the optical axis. The total optical length L of the optical system L0 refers to the distance on the optical axis from the vertex of the object-side lens surface of the first lens G1, which is positioned closest to the object in the front group L1, to the image plane. By satisfying condition (1), the optical system L0 can be miniaturized. If it falls below the lower limit of condition (1), the total length of the optical system L0 becomes longer, which is undesirable because it makes the optical system larger. Furthermore, in order to ensure the total length of the optical system is sufficient to correct various aberrations well, it is preferable to set the upper limit of condition (2) to one of 3.00, 2.95, 2.90, 2.85, 2.80, 2.75, 2.70, 2.65, 2.60, 2.55, or 2.50. Furthermore, it is more preferable to set the upper limit of condition (2) to one of the following: 2.45, 2.40, 2.35, 2.30, 2.25, 2.20, 2.15, 2.10, 2.05, or 2.00.

[0026] Furthermore, it is more preferable to set the numerical range of conditional expression (1) to the range of (1a) below.

[0027] With the above distinctive configuration, a compact optical system L0 with high optical performance can be realized.

[0028] Next, we will describe the conditions that are preferable for the optical system L0 of each embodiment to satisfy.

[0029] When the focal length of the first lens G1, which is positioned closest to the object in the optical system L0, is fG1, it is preferable that the following condition (2) is satisfied. 0.52 <fG1 / f1 (2)

[0030] Condition (2) specifies the focal length of the front group L1 and the focal length of the first lens G1, which is positioned closest to the object in the front group L1. By satisfying condition (2), barrel distortion aberration occurring in the optical system L0 can be well corrected. If the value falls below the lower limit of condition (2), strong barrel distortion aberration occurs, which is undesirable. Furthermore, in order to well correct the distortion aberration, it is more preferable to set the upper limit of condition (2) to one of 2.00, 1.95, 1.90, 1.85, 1.80, 1.75, 1.70, 1.65, 1.60, 1.55, or 1.50.

[0031] In each embodiment, the optical system L0 preferably satisfies the following condition (3), where f1 is the focal length of the front group L1 and f is the total focal length of the optical system L0. -2.98 <f1 / f<0.00 (3)

[0032] Condition (3) specifies the relationship between the focal length of the front group L1 and the overall focal length of the optical system L0. If the value falls below the lower limit of condition (3), the absolute value of the negative refractive power of the front group L1 becomes small. In this case, in order to achieve both distortion correction and field curvature correction, it is necessary to increase the thickness ratio of the lenses constituting the front group L1, which is undesirable because it reduces the moldability of the lenses. If the value exceeds the upper limit of condition (3), the front group L1 has a positive refractive power, making it difficult to correct distortion and field curvature, which is undesirable.

[0033] When the off-axis focal length in the sagittal direction of the front group L1 is fω1, it is preferable that the following condition (4) is satisfied. 0.00 <fω1 / f1<3.00 (4)

[0034] Conditional equation (4) specifies the ratio of the on-axis focal length to the off-axis focal length of the front group L1. If it falls below the lower limit of conditional equation (4), the front group L1 will have a positive refractive power with respect to off-axis rays, making it difficult to shorten the overall length, which is undesirable. If it exceeds the upper limit of conditional equation (4), the front group L1 will have a weaker off-axis refractive power with respect to the paraxial axis, making it difficult to correct barrel distortion and field curvature, which is also undesirable.

[0035] When the focal length of the lens GR, which is positioned closest to the image in the rear group L2, is fGR, and the focal length of the rear group L2 is f2, it is preferable that the following condition (5) is satisfied. -6.00 <fGR / f2<-2.00 (5)

[0036] Conditional equation (5) specifies the preferred range for the focal length of lens GR. If the focal length falls below the lower limit of conditional equation (5), the negative refractive power of lens GR relative to the rear group L2 becomes too weak. This is undesirable because it increases the back focus of optical system L0 and lengthens the overall length of optical system L0. If the focal length exceeds the upper limit of conditional equation (5), the negative refractive power of lens GR relative to the rear group L2 becomes too strong. This is undesirable because it shortens the back focus of optical system L0 and brings the image plane IP and lens GR too close together.

[0037] When the sag amount, which is the distance in the optical axis direction between the vertex of the object-side surface of the first lens G1 and the effective diameter position, is denoted as Sag, and the effective diameter is denoted as Ea, it is preferable that the following condition (6) is satisfied. Here, the sag amount of the optical system L0 is considered positive in the direction toward the image side. 0.00 <Sag / Ea<0.25 (6)

[0038] Conditional equation (6) specifies a preferred range for the distance in the optical axis direction between the vertex of the surface of the first lens G1 and the effective diameter position. If the distance falls below the lower limit of conditional equation (6), the object-side lens surface of the lens G1 will have a shape in which the concave surface faces the object at the periphery, resulting in insufficient correction for distortion aberration, which is undesirable. If the distance exceeds the upper limit of conditional equation (6), the curvature of the lens surface at the periphery of the first lens G1 becomes stronger, reducing the moldability of the first lens G1, which is also undesirable.

[0039] When the half-angle of view of the optical system L0 is ω, it is preferable that the following condition (7) is satisfied. 48.0 < ω < 70.0 (7)

[0040] Conditional equation (7) specifies the preferred range of half-angle of view in the optical system L0. If it falls below the lower limit of conditional equation (7), it results in excessive correction for distortion and field curvature, which is undesirable. If it exceeds the upper limit of conditional equation (7), it results in insufficient correction for distortion, which is also undesirable.

[0041] When the Abbe number of the material of the negative lens GN1, which is located closest to the object among the negative lenses included in the rear group L2, is νd, it is preferable that the following condition (8) is satisfied. 12.0 < νd < 40.0 (8)

[0042] Conditional equation (8) specifies the preferred range of Abbe numbers for the lens GN1 material. If the value falls below the lower limit of conditional equation (8), it results in excessive correction for axial chromatic aberration, which is undesirable. If the value exceeds the upper limit of conditional equation (8), it results in insufficient correction for axial chromatic aberration, which is also undesirable.

[0043] Furthermore, when the refractive index of the negative lens GN1, which is located closest to the image side among the negative lenses included in the rear group L2, is denoted as nd, it is preferable that the following condition (9) is satisfied. 1.50 <nd<1.80 (9)

[0044] Conditional equation (9) specifies the preferred range of refractive index for the material of the negative lens GN1. If the refractive index falls below the lower limit of conditional equation (9), it will result in insufficient correction for spherical aberration, which is undesirable. If the refractive index exceeds the upper limit of conditional equation (9), it will result in excessive correction for spherical aberration, which is also undesirable.

[0045] Furthermore, it is more preferable to set the numerical range of conditional expressions (1) to (9) to the range of conditional expressions (1a) to (9a) below. 0.41 <ImgH / L<1.50 (1a) 0.56 <fG1 / f1 (2a) -2.80 <f1 / f<‐1.00 (3a) 0.50 <fω1 / f1<2.50 (4a) -5.80 <fGR / f2<-2.20(5a) 0.05 <Sag / Ea<0.23 (6a) 48.0 < ω < 70.0 (7a) 15.0 < νd < 40.0 (8a) 1.52 <nd<1.75 (9a)

[0046] Furthermore, it is even more preferable to set the numerical range of conditional expressions (1) to (9) to the range of conditional expressions (1b) to (9b) below. 0.42 <ImgH / L<1.30 (1b) 0.60 <fG1 / f1 (2b) -2.75 <f1 / f<‐2.00 (3b) 0.80 <fω1 / f1<2.20 (4b) -5.50 <fGR / f2<-2.80 (5b) 0.10 <Sag / Ea<0.20 (6b) 50.0 < ω < 65.0 (7b) 16.0 < νd < 35.0 (8a) 1.55 <nd<1.73 (9a)

[0047] Next, we will describe the preferred configurations that the optical system L0 of each embodiment should satisfy.

[0048] The optical system L0 of each embodiment preferably has at least eight lenses. By distributing the refractive power among the lenses, the sensitivity of each lens can be reduced.

[0049] In the optical system L0 of each embodiment, it is preferable that the front group L1 includes at least two lenses. This allows for sufficient number of lenses to widen the optical system while effectively correcting distortion in the front group L1.

[0050] In the optical system L0 of each embodiment, it is preferable that the front group L1 includes a positive lens. Since the rear group L2 as a whole has a positive refractive power, by placing a positive lens in the front group L1, lenses with positive refractive power are placed on both the object side and the image side of the aperture diaphragm SP, respectively, so that field curvature and distortion aberrations can be corrected well.

[0051] In each embodiment, it is preferable that at least one of the object-side lens surface and the image-side lens surface of at least one lens included in the optical system L0 is aspherical. In particular, making the lens surface of the lens G1 located closest to the object in the front group L1 aspherical is preferable because it reduces the incident angle of off-axis light rays incident on lens G1, which is advantageous for correcting distortion and ensuring sufficient peripheral light. Furthermore, to enhance the above-mentioned effects, it is even more preferable that both the object-side lens surface and the image-side lens surface of lens G1 are aspherical.

[0052] In the optical system L0 of each embodiment, it is preferable that the rear group L2 has a positive lens, a positive lens, and a negative lens arranged in order from the object side. By arranging the positive lens near the image side of the aperture diaphragm SP, the light rays incident on the rear group L2 are converged, and the distance from the aperture diaphragm SP to the image plane can be shortened.

[0053] In each embodiment, among the lenses included in the optical system L0, it is preferable that the object-side lens surface of the lens GR, which is positioned closest to the image, is convex towards the object near the optical axis and concave towards the object at its periphery. Similarly, it is preferable that the image-side lens surface of lens GR is concave towards the image near the optical axis and convex towards the image at its periphery. This allows for correction of Petzval sum near the optical axis of lens GR while correcting astigmatism at its periphery.

[0054] Furthermore, using resin lenses for the lenses included in the optical system L0 is preferable because it allows for the realization of an aspherical lens shape with the inflection point described above.

[0055] Next, we will describe the detailed configurations of Examples 1 to 4. Note that for the optical system L0 of each example, we will omit the explanation of configurations similar to the optical system L0 of Example 1, and will mainly describe the differences from Example 1.

[0056] [Example 1] The optical system L0 of Example 1 consists of a front group L1 with negative refractive power, an aperture diaphragm SP, and a rear group L2 with positive refractive power, in that order from the object side. Because the front group L1 has negative refractive power, the optical system L0 has a so-called retrofocus type configuration, so the principal point is located on the image side, and the optical system L0 can be miniaturized in the radial direction while ensuring back focus.

[0057] In the optical system L0 of Example 1, the front group L1 consists of G1 to G3 lenses, and the rear group L2 consists of G4 to G9 lenses. An optical filter FL is also positioned on the image side of the rear group L2.

[0058] In the optical system L0 of Example 1, both the object-side and image-side lens surfaces of the lens G1, which is positioned closest to the object in the front group L1, have an aspherical shape. This reduces the incident angle of off-axis light rays incident on lens G1, which is advantageous for correcting distortion and ensuring sufficient peripheral illumination.

[0059] In the optical system L0 of Example 1, the rear group L2 has positive lenses, positive lenses, and negative lenses arranged in order from the object side. As a result, there is a positive refractive power near the image side of the aperture diaphragm SP, which converges the light rays incident on the rear group L2 and shortens the distance from the aperture diaphragm SP to the image plane.

[0060] In the optical system L0 of Example 1, the front group L1 includes a positive lens G3. As a result, lenses with positive refractive power are positioned on both the object side and the image side of the aperture diaphragm SP, which allows for good correction of field curvature and distortion.

[0061] In the optical system L0 of Example 1, the object-side lens surface of lens GR, which is positioned furthest towards the image in the rear group L2, is convex towards the object near the optical axis and concave towards the object in the peripheral area. Similarly, the image-side lens surface of lens GR is concave towards the image near the optical axis and convex towards the image in the peripheral area. This allows for correction of Petzval sum near the optical axis of lens GR while correcting astigmatism in the peripheral area. Furthermore, the negative lens GN1, which is positioned furthest towards the object among the negative lenses included in the rear group L2, has a lens shape similar to that of lens GR.

[0062] In the optical system L0 of Example 1, the negative lens GN1, which is located closest to the object in the rear group L2, is a resin lens. This improves the moldability of the negative lens GN1 and makes it possible to realize an aspherical lens shape with an inflection point in the negative lens GN1.

[0063] [Example 2] In the optical system L0 of Example 2, the front group L1 consists of G1 and G2 lenses, and the rear group L2 consists of G3 to G8 lenses. An optical filter FL is also placed on the image side of the rear group L2. By having eight lenses make up the optical system L0, the overall optical length is shortened, and the optical system L0 can be made more compact.

[0064] In the optical system L0 of Example 2, the front group L1 includes a positive lens G2. As a result, lenses with positive refractive power are positioned on both the object side and the image side of the aperture diaphragm SP, which allows for good correction of field curvature and distortion.

[0065] [Example 3] In the optical system L0 of Example 3, the front group L1 consists of G1 to G3 lenses, and the rear group L2 consists of G4 to G10 lenses. By having the optical system L0 consist of 10 lenses, the refractive power can be shared among the lenses, thereby reducing the sensitivity of each lens.

[0066] [Example 4] In the optical system L0 of Example 1, the front group L1 consists of G1 to G4 lenses, and the rear group L2 consists of G5 to G11 lenses. An optical filter FL is also placed on the image side of the rear group L2. By having an optical system L0 consisting of 11 lenses, the refractive power can be shared among the lenses, thereby reducing the sensitivity of each lens.

[0067] In the optical system L0 of Example 4, the front group L1 has three negative lenses arranged in order from the object side. In order to ensure sufficient back focus in a wide-angle optical system, a strong negative refractive force is required on the object side of the optical system. By distributing this negative refractive force among three negative lenses, the refractive force per negative lens can be reduced, thereby suppressing barrel distortion and field curvature.

[0068] Numerical examples 1 to 4 corresponding to Examples 1 to 4 are shown below.

[0069] In the surface data of each numerical example, r [mm] represents the radius of curvature of each optical surface, and d [mm] represents the distance on the optical axis between the k-th surface and the (k + 1)-th surface. Here, k is the surface number counted from the object side. Also, nd represents the refractive index with respect to the d-line of each optical member, and νd represents the Abbe number of each optical member. Here, for the Abbe number νd, when the refractive indices of the c-line (656.3 nm), d-line (587.56 nm), and F-line (486.1 nm) of the Fraunhofer lines are nC, nd, and nF respectively, νd=(nd-1) / (nF-nC) is expressed as.

[0070] In each numerical example, the half angle (°) of the optical system is shown, and the maximum image height corresponding to the half angle is shown as the "image height". Further, in each numerical example, as lens group data, the focal length in the d-line of each lens group is shown. Note that d, focal length [mm], F-number, and half angle [°] are the values of the optical system of each example when focused at infinity. "BF (back focus)" represents the value obtained by air-converting the distance on the optical axis from the last surface of the lens (the most image-side surface) to the paraxial image plane. "Total lens length" is the length obtained by adding the distance on the optical axis from the frontmost surface of the lens (the most object-side surface) to the last surface of the optical system and the back focus.

[0071] Also, when the optical surface is an aspherical surface, an asterisk symbol is attached to the right side of the surface number. The aspherical shape is such that 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, A14, A16, A18, A20 are the aspherical coefficients of each order, X=(h 14 , 10 , 12 , 6 , 8 , 4 , 20 , 16 , 18 / R) / [1+{1-(1+k)(h / R) 2}] 1 / 2 +A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h<\(0000008\)>+A14×h<\(0000009\)>+A16×h<\(0000010\)>+A18×h<\(0000011\)>+A20×h<\(0000012\)> It is expressed as follows: "e±XX" in each aspherical coefficient is "×10± XX It means "...".

[0072] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd Effective diameter 1* 4.591 0.48 1.54400 56.0 4.01 2* 1.877 0.09 3.17 3* 1.772 0.38 1.69800 16.3 2.80 4* 1.154 0.19 2.15 5* 1.082 0.30 1.62100 23.6 1.93 6* 1.538 (variable) 1.57 7 (aperture) ∞ 0.12 1.43 8* -3.711 0.29 1.59100 27.2 1.35 9* -2.488 -0.08 1.43 10 ∞ 0.10 1.45 11* 10.601 0.86 1.54400 56.0 1.61 12* -1.224 0.07 2.01 13* 114.877 0.35 1.59100 27.2 2.25 14* 3.206 0.30 2.47 15* -5.202 0.29 1.69800 16.3 2.50 16* -62.071 0.09 2.76 17* -2.015 0.56 1.54400 56.0 2.87 18* -1.826 0.09 3.45 19* 1.865 0.87 1.54400 56.0 3.59 20* 2.593 0.84 5.23 21 ∞ 0.26 1.51700 64.2 7.15 22 ∞ (variable) 7.38 Image plane ∞ Aspherical data Front page K = 0.00000e+00 A 4= 2.54970e-02 A 6=-6.40902e-04 A 8=-4.27401e-03 A10= 1.50107e-03 A12=-1.58449e-04 2nd side K = 0.00000e+00 A 4= 6.33958e-02 A 6=-7.37338e-02 A 8= 1.68063e-02 A10=-2.07051e-03 3rd page K = 0.00000e+00 A 4= 3.77375e-02 A 6=-1.67398e-01 A 8= 1.74110e-01 A10=-7.73265e-02 A12= 1.12872e-02 Side 4 K = 0.00000e+00 A 4=-6.13897e-02 A 6=-3.88994e-01 A 8= 5.79202e-01 A10=-3.12293e-01 5th page K = 0.00000e+00 A 4=-5.70688e-02 A 6=-2.95821e-01 Side 6 K = 0.00000e+00 A 4= 9.60136e-02 A 6=-6.18947e-02 A 8=-5.95627e-01 A10= 6.65492e-01 A18=-5.15324e-01 A20= 1.37029e-01 Side 8 K = 0.00000e+00 A 4=-1.23212e-01 A 6=-4.76965e-03 9th page K = 0.00000e+00 A 4= 4.16656e-02 A 6=-4.78646e-01 A 8=-2.02302e-01 A10= 1.76310e+01 A12=-1.08531e+02 A14= 3.42880e+02 A16=-6.16495e+02 A18= 5.98947e+02 A20=-2.44370e+02 Page 11 K = 0.00000e+00 A 4= 1.47619e-01 A 6=-7.54190e-01 A 8= 2.62330e+00 A10=-6.06508e+00 A12= 8.07422e+00 A14=-4.81606e+00 A16=-9.74318e-01 A18= 2.62662e+00 A20=-8.39803e-01 Page 12 K = 0.00000e+00 A 4= 5.09820e-02 A 6=-1.78266e-02 Page 13 K = 0.00000e+00 A 4=-1.80286e-01 A 6= 4.80067e-02 Page 14 K = 0.00000e+00 A 4=-1.78921e-01 A 6=-1.21046e-01 A 8= 5.69246e-01 A10=-1.53447e+00 A12= 2.53863e+00 A14=-2.73111e+00 A16= 1.80510e+00 A18=-6.50599e-01 A20= 9.73099e-02 Page 15 K = 1.55073e+01 A 4=-1.83875e-01 A 6= 7.68870e-02 A 8= 2.49362e-01 A10=-1.40344e+00 A12= 3.35432e+00 A14=-4.49764e+00 A16= 3.38996e+00 A18=-1.32669e+00 A20= 2.09991e-01 Page 16 K =-1.00000e+00 A 4=-3.02303e-01 A 6= 4.25798e-01 A 8=-5.97774e-01 A10= 7.34558e-01 A12=-6.19998e-01 A14= 3.17882e-01 A16=-9.02908e-02 A18= 1.19372e-02 A20=-3.39726e-04 Page 17 K = 0.00000e+00 A 4= 2.19111e-01 A 6=-6.65840e-02 Page 18 K = 0.00000e+00 A 4= 1.22189e-01 A 6=-1.86431e-02 A 8= 2.18119e-03 A10= 3.38466e-05 Page 19 K = 0.00000e+00 A 4=-1.61286e-01 A 6= 1.54522e-02 A 8=-6.00885e-03 Page 20 K = 0.00000e+00 A 4=-7.36344e-02 A 6= 7.74757e-03 A 8=-1.27965e-03 A10= 1.28730e-04 A12=-1.17664e-05 Various data Focal length 2.94 F-number 2.21 Field of view 52.79 Image height 3.88 Lens length 7.13 BF 1.52 Lens group data Group starting plane focal length L1 1 -6.65 L2 7 2.33 Single lens data Lens starting plane, focal length G1 1 -6.22 G2 3 -6.36 G3 5 4.70 G4 8 11.73 G5 11 2.07 G6 13 -5.59 G7 15 -8.15 G8 17 17.56 G9 19 -8.58 G10 21 0.00

[0073] [Numerical Example 2] Unit: mm Surface data Face number rd nd νd Effective diameter 1* 4.622 0.50 1.54400 56.0 4.00 2* 1.164 0.87 2.52 3* 3.589 0.20 1.62100 23.6 1.83 4* 3.796 0.32 1.49 5 (aperture) ∞ (variable) 1.23 6* 4.080 0.39 1.59100 27.2 1.23 7* -28.072 0.06 1.33 8* 3.557 0.61 1.54400 56.0 1.36 9* -3.300 0.17 1.48 10* -3.789 0.30 1.69800 16.3 1.56 11* -66.948 0.08 2.05 12* 1.808 0.49 1.54400 56.0 2.73 13* -86.602 0.12 3.07 14* -17.210 0.51 1.54400 56.0 3.25 15* -4.078 0.36 3.42 16* 10.065 0.65 1.70500 14.0 3.53 17* 2.735 0.30 4.86 18 ∞ 0.21 1.51700 64.2 5.59 19 ∞ (variable) 5.74 Image plane ∞ Aspherical data Front page K =-1.09449e+01 A 4= 4.21461e-02 A 6=-1.02324e-02 A 8= 4.89806e-03 A10=-1.63399e-03 A12= 3.39007e-04 A14=-3.57982e-05 A16= 9.91744e-07 A18=-8.66980e-08 A20= 1.61150e-09 2nd side K =-4.77071e+00 A 4= 3.86428e-01 A 6=-5.68268e-01 A 8= 1.27418e+00 A10=-2.12005e+00 A12= 2.29734e+00 A14=-1.48840e+00 A16= 5.06978e-01 A18=-6.55830e-02 A20=-1.99040e-03 3rd page K = 0.00000e+00 A 4= 7.09504e-02 A 6= 2.20062e-01 A 8=-3.07588e-01 A10= 4.31630e-01 A12=-1.24465e+00 A14= 1.42501e+00 A16=-3.31675e-01 A18=-2.81020e-01 A20= 4.67600e-02 Side 4 K = 2.25764e+01 A 4= 1.85210e-01 A 6= 9.82566e-01 A 8=-5.30993e+00 A10= 2.24078e+01 A12=-5.72662e+01 A14= 7.39959e+01 A16=-2.94485e+01 A18=-2.28850e+01 A20= 9.50830e+00 Page 6 K = 0.00000e+00 A 4= 5.77219e-02 A 6= 2.95467e-02 A 8=-1.81855e+00 A10= 1.58735e+00 A12= 1.08936e+02 A14=-8.82560e+02 A16= 3.01080e+03 A18=-4.90080e+03 A20= 3.11340e+03 Page 7 K = 0.00000e+00 A 4=-1.35288e-01 A 6= 5.51389e-01 A 8=-6.52425e+00 A10= 4.50622e+01 A12=-1.94162e+02 A14= 5.16831e+02 A16=-8.29792e+02 A18= 7.34640e+02 A20=-2.75210e+02 Page 8 K = 0.00000e+00 A 4=-6.02118e-02 A 6= 7.63129e-01 A 8=-5.14082e+00 A10= 2.51467e+01 A12=-7.57406e+01 A14= 1.40016e+02 A16=-1.46692e+02 A18= 6.84050e+01 A20=-2.68246e+00 Page 9 K = 2.12397e+00 A 4= 6.57713e-02 A 6=-2.03053e+00 A 8= 8.36111e+00 A10=-2.35565e+01 A12= 4.52377e+01 A14=-5.63275e+01 A16= 4.36473e+01 A18=-1.89155e+01 A20= 3.49253e+00 Page 10 K =-1.77841e+01 A 4= 2.88919e-01 A 6=-2.73548e+00 A 8= 7.86385e+00 A10=-1.63038e+01 A12= 2.51925e+01 A14=-3.31230e+01 A16= 3.67650e+01 A18=-2.72793e+01 A20= 8.00798e+00 Page 11 K = 3.74686e+03 A 4= 1.63652e-01 A 6=-1.65162e+00 A 8= 4.80541e+00 A10=-7.84942e+00 A12= 8.14447e+00 A14=-5.41416e+00 A16= 2.23548e+00 A18=-5.39182e-01 A20= 6.30107e-02 Page 12 K =-5.85659e+00 A 4=-9.43399e-02 A 6=-3.67868e-01 A 8= 1.10109e+00 A10=-1.44062e+00 A12= 1.11738e+00 A14=-5.50431e-01 A16= 1.70838e-01 A18=-3.05712e-02 A20= 2.37267e-03 Page 13 K = 0.00000e+00 A 4=-5.31965e-03 A 6= 7.84844e-04 A 8=-1.36639e-03 Page 14 K = 0.00000e+00 A 4=-3.58813e-03 A 6= 1.12176e-03 A 8=-2.20043e-04 A10= 3.94519e-05 Page 15 K = 0.00000e+00 A 4= 3.47171e-03 A 6= 1.99077e-02 A 8=-3.06640e-01 A10= 5.02628e-01 A12=-3.64013e-01 A14= 1.38631e-01 A16=-2.74899e-02 A18= 2.35659e-03 A20=-3.02755e-05 Page 16 K = 0.00000e+00 A 4=-1.19473e-01 A 6= 1.04106e-01 A 8=-6.02809e-01 A10= 9.19869e-01 A12=-6.71299e-01 A14= 2.74179e-01 A16=-6.43304e-02 A18=8.13327e-03 A20=-4.31857e-04 Page 17 K = 0.00000e+00 A 4=-2.80744e-02 A 6=-1.62828e-01 A 8= 1.45446e-01 A10=-6.32545e-02 A12= 1.63531e-02 A14=-2.64957e-03 A16= 2.65366e-04 A18=-1.50195e-05 A20= 3.63367e-07 Various data Focal length 1.92 F-number 2.21 Field of view 58.21 Image height 3.10 Lens length 6.50 BF 0.41 Lens group data Group starting plane focal length L1 1 -3.11 L2 6 1.71 Single lens data Lens starting plane, focal length G1 1 -3.02 G2 3 77.96 G3 6 6.05 G4 8 3.25 G5 10 -5.76 G6 12 3.26 G7 14 9.69 G8 16 -5.53 G9 18 0.00

[0074] [Numerical Example 3] Unit: mm Surface data Face number rd nd νd Effective diameter 1* 4.052 0.50 1.54400 56.0 4.97 2* 2.130 0.12 3.95 3* 2.256 0.40 1.69800 16.3 3.64 4* 1.715 0.73 3.03 5* 1.915 0.33 1.62100 23.6 1.97 6* 2.290 (variable) 1.54 7 (aperture) ∞ 0.10 1.42 8* -8.985 0.32 1.59100 27.2 1.42 9* -3.828 0.13 1.54 10* 126.934 0.85 1.54400 56.0 1.61 11* -1.576 0.10 2.05 12* -13.008 0.30 1.59100 27.2 2.17 13* 3.580 0.30 2.48 14* -4.280 0.30 1.69800 16.3 2.55 15* -5.779 0.24 3.10 16* -17.744 0.63 1.54400 56.0 4.01 17* -2.291 0.10 4.34 18* 2.732 0.87 1.54400 56.0 4.99 19* 3.042 0.35 5.93 20* 14.123 0.71 1.70500 14.0 6.84 21* 3.877 0.38 7.50 22 ∞ 0.26 1.51700 64.2 7.61 23 ∞ (variable) 7.75 Image plane ∞ Aspherical data Front page K = 0.00000e+00 A 4=-3.07731e-03 A 6= 3.00737e-03 A 8=-8.47144e-04 A10= 1.21092e-04 A12=-6.93945e-06 2nd side K = 0.00000e+00 A 4= 2.86153e-02 A 6=-3.02061e-02 A 8= 9.25596e-03 A10=-1.37869e-03 3rd page K = 0.00000e+00 A 4= 6.15659e-02 A 6=-4.70842e-02 A 8= 1.50910e-02 A10=-2.32884e-03 A12= 2.32308e-05 Side 4 K = 0.00000e+00 A 4= 3.86307e-02 A 6=-4.60362e-02 A 8= 1.68308e-02 A10=-4.98505e-03 5th page K = 0.00000e+00 A 4= 3.66836e-02 A 6= 2.61744e-02 Side 6 K = 0.00000e+00 A 4= 8.63360e-02 A 6= 1.36372e-01 A 8=-2.19196e-01 A10= 2.29418e-01 A18=-5.15324e-01 A20= 1.37029e-01 Page 8 K = 0.00000e+00 A 4=-1.03223e-01 A 6=-9.83741e-02 Page 9 K = 0.00000e+00 A 4=-3.64040e-02 A 6=-1.43447e-01 A 8=-5.71314e-01 A10= 5.77888e+00 A12=-2.47397e+01 A14= 6.16318e+01 A16=-9.00846e+01 A18= 7.18831e+01 A20=-2.41209e+01 Page 10 K = 0.00000e+00 A 4= 1.11675e-01 A 6=-1.51230e-01 A 8=-3.40553e-01 A10= 3.41133e+00 A12=-1.18030e+01 A14= 2.25319e+01 A16=-2.45121e+01 A18= 1.40973e+01 A20=-3.29067e+00 Page 11 K = 0.00000e+00 A 4= 3.16674e-02 A 6=-3.34507e-02 Page 12 K = 0.00000e+00 A 4=-3.06293e-01 A 6= 1.14326e-01 Page 13 K = 0.00000e+00 A 4=-2.82012e-01 A 6=-2.15392e-02 A 8= 4.70890e-01 A10=-1.36401e+00 A12= 2.26373e+00 A14=-2.28280e+00 A16= 1.39120e+00 A18=-4.73228e-01 A20= 6.95500e-02 Page 14 K =-6.52180e+00 A 4= 1.60212e-02 A 6=-1.14233e-01 A 8= 1.34753e-01 A10=-3.61854e-01 A12= 6.51815e-01 A14=-7.07864e-01 A16= 4.64806e-01 A18=-1.75866e-01 A20= 2.96999e-02 Page 15 K =-1.00000e+00 A 4=-2.27112e-02 A 6= 1.02657e-02 A 8=-2.01315e-02 A10= 3.22438e-02 A12=-3.06026e-02 A14= 1.42662e-02 A16=-3.20216e-03 A18= 3.04576e-04 A20=-5.54668e-06 Page 16 K = 0.00000e+00 A 4= 6.26857e-02 A 6=-1.40260e-02 Page 17 K = 0.00000e+00 A 4= 6.95417e-02 A 6= 1.29310e-02 A 8=-8.04863e-03 A10= 9.39637e-04 Page 18 K = 0.00000e+00 A 4=-5.92072e-02 A 6= 4.64173e-03 A 8=-3.64040e-04 Page 19 K = 0.00000e+00 A 4=-3.98586e-02 A 6= 3.65251e-03 A 8=-4.07558e-04 A10= 3.33785e-05 A12=-2.86780e-06 Page 20 K = 0.00000e+00 A 4=-4.90605e-03 A 6=-4.51089e-03 A 8= 1.75998e-03 A10=-2.96272e-04 A12= 2.67864e-05 A14=-1.26658e-06 A16= 2.47217e-08 Page 21 K = 0.00000e+00 A 4=-3.29180e-02 A 6= 4.26108e-03 A 8=-3.93460e-04 A10= 1.76042e-05 A12=-6.00855e-08 A14=-3.39119e-09 A16=-9.90108e-10 Various data Focal length 3.02 F-number 2.21 Field of view 52.06 Image height 3.88 Lens length 8.70 BF 0.45 Lens group data Group starting plane focal length L1 1 -8.21 L2 7 2.53 Single lens data Lens starting plane, focal length G1 1 -9.08 G2 3 -14.67 G3 5 14.10 G4 8 11.03 G5 10 2.87 G6 12 -4.72 G7 14 -25.75 G8 16 4.77 G9 18 24.73 G10 20 -7.80

[0075] [Numerical Example 4] Unit: mm Surface data Face number rd nd νd Effective diameter 1* 5.000 0.50 1.54400 56.0 5.88 2* 2.227 0.34 4.24 3* 2.344 0.40 1.69800 16.3 3.76 4* 1.793 0.47 3.29 5* 6.487 0.30 1.54400 56.0 3.07 6* 4.232 0.19 2.76 7* 1.969 0.30 1.62100 23.6 2.09 8* 2.592 (variable) 1.75 9 (aperture) ∞ 0.10 1.46 10* -5.665 0.30 1.59100 27.2 1.35 11* -2.538 0.08 1.47 12* 89.117 0.83 1.54400 56.0 1.56 13* -1.557 0.10 1.93 14* -3.735 0.30 1.59100 27.2 1.97 15* 6.169 0.34 2.34 16* -5.072 0.35 1.69800 16.3 2.43 17* -8.148 0.10 3.12 18* 27.830 0.72 1.54400 56.0 4.01 19* -2.347 0.16 4.39 20* 2.820 0.87 1.54400 56.0 5.22 21* 2.961 0.24 5.82 22* 8.518 0.71 1.70500 14.0 6.28 23* 4.126 0.38 7.13 24 ∞ 0.26 1.51700 64.2 7.32 25 ∞ (variable) 7.43 Image plane ∞ Aspherical data Front page K = 0.00000e+00 A 4=-6.07893e-04 A 6= 1.32175e-03 A 8=-2.93328e-04 A10= 3.07045e-05 A12=-1.25878e-06 2nd side K = 0.00000e+00 A 4= 3.03485e-02 A 6=-1.67125e-02 A 8= 6.33996e-03 A10=-1.07597e-03 3rd page K = 0.00000e+00 A 4= 9.16094e-02 A 6=-3.58801e-02 A 8= 1.03115e-02 A10=-2.84761e-03 A12= 2.39186e-04 Side 4 K = 0.00000e+00 A 4= 9.51787e-02 A 6=-2.90906e-02 A 8=-9.16503e-03 A10= 1.21401e-03 5th page K = 0.00000e+00 A 4= 1.12544e-01 A 6=-2.08590e-02 A 8= 8.45431e-04 A10=-5.73030e-04 Side 6 K = 0.00000e+00 A 4= 1.55899e-01 A 6=-5.98208e-02 Side 7 K = 0.00000e+00 A 4= 6.97646e-02 A 6=-3.75828e-02 Page 8 K = 0.00000e+00 A 4= 5.97916e-02 A 6= 2.65502e-01 A 8=-6.09114e-01 A10= 5.87441e-01 A18=-5.15324e-01 A20= 1.37029e-01 Page 10 K = 0.00000e+00 A 4=-8.55150e-02 A 6=-1.28438e-01 Page 11 K = 0.00000e+00 A 4= 1.59565e-01 A 6=-6.60450e-01 A 8= 7.69393e-01 A10=-3.08663e-01 A12= 8.56686e-02 A14=-3.97626e+00 A16= 1.40912e+01 A18=-1.89261e+01 A20= 9.22077e+00 Page 12 K = 0.00000e+00 A 4= 3.35567e-01 A 6=-6.23402e-01 A 8= 3.12741e-01 A10= 2.85469e+00 A12=-1.11485e+01 A14= 2.10627e+01 A16=-2.22059e+01 A18= 1.20228e+01 A20=-2.44933e+00 Page 13 K = 0.00000e+00 A 4= 1.44043e-02 A 6=-3.33594e-02 Page 14 K = 0.00000e+00 A 4=-4.07482e-01 A 6= 1.58953e-01 Page 15 K = 0.00000e+00 A 4=-3.34168e-01 A 6= 6.35319e-03 A 8= 5.01334e-01 A10=-1.43512e+00 A12= 2.41307e+00 A14=-2.48412e+00 A16= 1.54198e+00 A18=-5.33067e-01 A20= 7.98230e-02 Page 16 K =-1.26320e+01 A 4= 1.85302e-02 A 6=-1.69465e-01 A 8= 1.85576e-01 A10=-3.88721e-01 A12= 6.94163e-01 A14=-7.92491e-01 A16= 5.32772e-01 A18=-1.98749e-01 A20= 3.05655e-02 Page 17 K =-1.00000e+00 A 4=-1.50198e-02 A 6=-5.99313e-03 A 8=-1.78373e-02 A10= 3.19572e-02 A12=-3.04820e-02 A14= 1.52540e-02 A16=-4.63191e-03 A18= 9.11564e-04 A20=-9.37171e-05 Page 18 K = 0.00000e+00 A 4= 4.50798e-02 A 6=-1.13848e-02 Page 19 K = 0.00000e+00 A 4= 6.75442e-02 A 6= 1.15663e-02 A 8=-7.29456e-03 A10= 8.55124e-04 Page 20 K = 0.00000e+00 A 4=-6.04143e-02 A 6= 7.15022e-03 A 8=-5.74141e-04 Page 21 K = 0.00000e+00 A 4=-5.00251e-02 A 6= 4.21282e-03 A 8=-3.31094e-04 A10= 5.54193e-05 A12=-6.88983e-06 Page 22 K = 0.00000e+00 A 4=-1.08354e-02 A 6=-3.65405e-03 A 8= 1.55345e-03 A10=-2.31254e-04 A12= 1.62608e-05 A14=-5.90919e-07 A16= 1.15953e-08 Page 23 K = 0.00000e+00 A 4=-3.19763e-02 A 6= 4.61814e-03 A 8=-4.53528e-04 A10= 1.92003e-05 A12= 1.72738e-08 A14= 4.58410e-10 A16=-1.34101e-09 Various data Focal length 2.58 F-number 2.21 Field of view 56.35 Image height 3.88 Lens length 9.00 BF 0.45 Lens group data Group starting plane focal length L1 1 -6.13 L2 9 2.36 Single lens data Lens starting plane, focal length G1 1 -7.88 G2 3 -15.55 G3 5 -23.47 G4 7 11.15 G5 10 7.51 G6 12 2.82 G7 14 -3.89 G8 16 -20.19 G9 18 4.01 G10 20 34.20 G11 22 -12.16

[0076] The values ​​of the conditions in formulas (1) to (9) in each embodiment are shown in Table 1.

[0077] [Table 1]

[0078] [Imaging device] Next, we will describe an imaging device that uses the optical system L0 of each embodiment as the imaging optical system.

[0079] Figure 11 is a schematic diagram of an imaging device 10 equipped with the optical system L0 of each embodiment. The imaging device 10 comprises a camera body 13, an optical system 11 which is the same as any of the optical systems L0 described in Embodiments 1 to 4 above, and a light-receiving element 12 which converts the image formed by the optical system 11 into photoelectricity.

[0080] Furthermore, an image sensor such as a CCD or CMOS sensor can be used as the light-receiving element 12. In this case, the output image can be made higher quality by correcting various aberrations such as distortion and chromatic aberration of the image acquired by the light-receiving element 12, for example, using an electrical method.

[0081] Furthermore, the optical system L0 in each embodiment is not limited to the digital still camera shown in Figure 11, but can be applied to various optical devices such as digital video cameras and silver halide film cameras. Also, the camera can be either a fixed-lens type or a lens-interchangeable type.

[0082] [Lens device] Next, we will describe the lens apparatus using the optical system L0 of each embodiment.

[0083] Figure 12 is a schematic diagram of the external appearance of a lens device 20 equipped with the optical system L0 of each embodiment. The lens device 20 is a so-called interchangeable lens that is detachably attached to a camera body (not shown). The lens device 20 has a photographic optical system 21 composed of one of the optical systems described in Embodiments 1 to 4. The lens device 20 also has a focus operation means 22 and an operation means 23 for changing the shooting mode.

[0084] By operating the focus control means 22, the arrangement of the imaging optical system 21 can be changed mechanically or electrically, thereby changing the focal position.

[0085] Furthermore, the user may operate the operating means 23 to change the arrangement of the lens group of the imaging optical system 21 for purposes other than focusing. For example, the arrangement of the lens group of the imaging optical system 21 may be changed mechanically or electrically in conjunction with the operation of the operating means 23, thereby changing the aberration of the imaging optical system 21. In this case, it is preferable that the focus position does not change substantially.

[0086] Although preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of its gist.

[0087] Furthermore, the disclosures herein include the following configurations.

[0088] (Composition 1) An optical system having a front group with negative refractive power, an aperture diaphragm, and a rear group with positive refractive power, arranged in order from the object side to the image side, The optical system has at least eight lenses, The aforementioned group includes an aspherical lens having an inflection point. When the maximum image height of the optical system is ImgH, the total optical length of the optical system is L, the focal length of the front group is f1, and the focal length of the lens G1 located closest to the object in the front group is fG1, 0.40 <ImgH / L 0.52 <fG1 / f1 -2.98 <f1 / f<0.00 An optical system characterized by satisfying the following conditional equation.

[0089] (Configuration 2) An optical system having a front group with negative refractive power, an aperture diaphragm, and a rear group with positive refractive power, arranged in order from the object side to the image side, The aforementioned front group includes at least two lenses, The aforementioned group includes an aspherical lens having an inflection point. When the maximum image height of the optical system is ImgH and the total optical length of the optical system is L, 0.40 <ImgH / L An optical system characterized by satisfying the following conditional equation.

[0090] (Composition 3) The optical system according to configuration 1 or 2, characterized in that in the rear group, a positive lens, a positive lens, and a negative lens are arranged in order from the object side to the image side.

[0091] (Composition 4) When the off-axis focal length in the sagittal direction of the aforementioned front group is fω1, 0.00 <fω1 / f1<3.00 An optical system according to any one of configurations 1 to 3, characterized by satisfying the following conditional expression.

[0092] (Composition 5) When the focal length of the lens GR, which is positioned closest to the image in the rear group, is fGR, and the focal length of the rear group is f2, -6.00 <fGR / f2<-2.00 An optical system according to any one of configurations 1 to 4, characterized in that it satisfies the following conditional expression.

[0093] (Composition 6) The optical system has lenses made of resin material, The optical system according to any one of configurations 1 to 5, characterized in that at least one of the object-side lens surface and the image-side lens of the lens made of the resin material is aspherical.

[0094] (Configuration 7) When the distance in the optical axis direction at the effective diameter position from the vertex of the object-side lens surface of the lens G1 is Sag and the effective diameter of the lens G1 is Ea, 0.00 < Sag / Ea < 0.25 The optical system according to any one of Configurations 1 to 6, characterized by satisfying the conditional expression.

[0095] (Configuration 8) When the semi-field angle corresponding to the maximum image height is ω [°], 48.0 < ω < 70.0 The optical system according to any one of Configurations 1 to 7, characterized by satisfying the conditional expression.

[0096] (Configuration 9) When the Abbe number of the material of the negative lens GN1 arranged closest to the object side among the negative lenses included in the rear group is νd, 12.0 < νd < 40.0 The optical system according to any one of Configurations 1 to 8, characterized by satisfying the conditional expression.

[0097] (Configuration 10) When the refractive index with respect to the d-line of the material of the negative lens GN1 arranged closest to the object side among the negative lenses included in the rear group is nd, 1.50 < nd < 1.70 The optical system according to any one of Configurations 1 to 9, characterized by satisfying the conditional expression.

[0098] (Configuration 11) The object-side lens surface of the negative lens GN1 arranged closest to the object side among the negative lenses included in the rear group is convex on the object side near the optical axis and concave on the object side in the peripheral part, The image-side lens surface of the negative lens GN1 is concave on the image side near the optical axis and convex on the image side in the peripheral part, and the optical system according to any one of Configurations 1 to 10 is characterized thereby.

[0099] (Configuration 12) The object-side lens surface of lens GR, which is positioned closest to the image in the aforementioned rear group, is convex towards the object near the optical axis and concave towards the object at its periphery. The optical system according to any one of configurations 1 to 11, characterized in that the image-side lens surface of the lens GR is concave towards the image side near the optical axis and convex towards the image side at the periphery.

[0100] (Composition 13) The optical system according to any one of configurations 1 to 12, characterized in that the front group consists of two lenses and the rear group consists of six lenses.

[0101] (Composition 14) The optical system according to any one of configurations 1 to 12, characterized in that the front group consists of three lenses and the rear group consists of six lenses.

[0102] (Composition 15) The optical system according to any one of configurations 1 to 12, characterized in that the front group consists of three lenses and the rear group consists of seven lenses.

[0103] (Composition 16) The optical system according to any one of configurations 1 to 12, characterized in that the front group consists of four lenses and the rear group consists of seven lenses.

[0104] (Composition 17) The optical system described in any one of configurations 1 to 16, An imaging device characterized by having an image sensor that receives light from an image formed by the optical system.

[0105] (Composition 18) A lens device characterized by having an optical system according to any one of configurations 1 to 16 and an operating means operated by a user. [Explanation of Symbols]

[0106] L1 front group L2 rear group SP aperture diaphragm FL Optical Filter IP image plane

Claims

1. An optical system having a front group with negative refractive power, an aperture diaphragm, and a rear group with positive refractive power, arranged in order from the object side to the image side, The optical system has at least eight lenses, The aforementioned group includes an aspherical lens having an inflection point. When the maximum image height of the optical system is ImgH, the total optical length of the optical system is L, the focal length of the front group is f1, the focal length of the first lens G1 positioned closest to the object in the front group is fG1, and the focal length of the entire optical system is f, 0.40<ImgH / L 0.52<fG1 / f1 -2.98<f1 / f<0.00 An optical system characterized by satisfying the following conditional equation.

2. The optical system according to claim 1, characterized in that in the rear group, a positive lens, a positive lens, and a negative lens are arranged in order from the object side to the image side.

3. When the off-axis focal length in the sagittal direction of the aforementioned front group is fω1, 0.00<fω1 / f1<3.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. When the focal length of lens GR, which is positioned closest to the image in the rear group, is fGR, and the focal length of the rear group is f2, -6.00<fGR / f2<-2.00 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

5. The optical system has lenses made of resin material, The optical system according to claim 1 or 2, characterized in that at least one of the object-side lens surface and the image-side lens of the lens made of the resin material is aspherical.

6. When Sag is the distance in the optical axis direction from the vertex of the object-side lens surface of the lens G1 to the effective diameter position, and Ea is the effective diameter of the lens G1, 0.00<Sag / Ea<0.25 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

7. When the half-angle of view corresponding to the maximum image height is ω [°], 48.0<ω<70.0 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

8. When the Abbe number of the material of the negative lens GN1, which is located closest to the object among the negative lenses included in the aforementioned group, is νd, 12.0<νd<40.0 The optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

9. When the refractive index of the material of the negative lens GN1 with respect to the d line is nd, 1.50<nd<1.70 The optical system according to claim 8, characterized in that it satisfies the following conditional expression.

10. The object-side lens surface of the negative lens GN1, which is positioned closest to the object among the negative lenses included in the aforementioned rear group, is convex towards the object near the optical axis and concave towards the object at its periphery. The optical system according to claim 1 or 2, characterized in that the image-side lens surface of the negative lens GN1 is concave towards the image side near the optical axis and convex towards the image side at the periphery.

11. The object-side lens surface of the lens GR, which is positioned closest to the image in the aforementioned rear group, is convex towards the object near the optical axis and concave towards the object at its periphery. The optical system according to claim 1 or 2, characterized in that the image-side lens surface of the lens GR is concave towards the image side near the optical axis and convex towards the image side at the periphery.

12. The optical system according to claim 1 or 2, characterized in that the front group consists of two lenses and the rear group consists of six lenses.

13. The optical system according to claim 1 or 2, characterized in that the front group consists of three lenses and the rear group consists of six lenses.

14. The optical system according to claim 1 or 2, characterized in that the front group consists of three lenses and the rear group consists of seven lenses.

15. The optical system according to claim 1 or 2, characterized in that the front group consists of four lenses and the rear group consists of seven lenses.

16. An optical system having a front group with negative refractive power, an aperture diaphragm, and a rear group with positive refractive power, arranged in order from the object side to the image side, The aforementioned front group includes at least two lenses, The aforementioned group includes an aspherical lens having an inflection point. When the maximum image height of the optical system is ImgH and the total optical length of the optical system is L, 0.40<ImgH / L An optical system characterized by satisfying the following conditional equation.

17. The optical system according to any one of claims 1 to 16, An imaging device characterized by having an image sensor that receives light from an image formed by the optical system.

18. A lens device characterized by having an optical system according to any one of claims 1 to 16 and an operating means operated by a user.

Images