Optical system and imaging device

Abstract

To provide an optical system with a wide field of view and good optical performance. [Solution] The optical system includes a first lens G1, which is a negative refractive meniscus lens positioned closest to the object, and a second lens G2, which is adjacent to the first lens on the image side and also has a negative refractive power. When the focal length of the first lens is f1, the focal length of the air lens between the first and second lenses is f12, and the focal length of the optical system is f, the following conditions are satisfied: -180.0 ≤ f1 / f ≤ -35.0 and 12.5 ≤ f12 / f ≤ 100.0.

Description

Technical Field

[0001] The present invention relates to an optical system suitable for imaging.

Background Art

[0002] As an optical system used for imaging ultra-wide-angle videos, Patent Document 1 discloses an optical system having an angle of view of approximately 180°.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] When a negative meniscus lens with a large curvature is used on the most object side of the optical system as described above, there is a risk that light incident from the object side and reflected by the surface of the meniscus lens on the image side with a large opening angle will generate a ghost.

Means for Solving the Problems

[0005] An optical system according to one aspect of the present invention includes a first lens that is a meniscus lens with negative refractive power disposed on the most object side, and a second lens with negative refractive power adjacent to the first lens on the image side. When the total angle of view of the optical system is 160° or more, f1 is the focal length of the first lens, f12 is the focal length of the air lens between the first lens and the second lens, and f is the focal length of the optical system, -180.0≦f1 / f≦-35.0 12.5≦f12 / f≦100.0 The optical system is characterized by satisfying the following conditions.

[0006] Furthermore, another aspect of the present invention is an optical system comprising a first lens, which is a negative refractive power meniscus lens positioned closest to the object, and a second lens with negative refractive power adjacent to the first lens on the image side, characterized in that the total angle of view is 160° or more. An imaging device equipped with the above optical system also constitutes another aspect of the present invention. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical system that has a wide field of view while having good optical performance. [Brief explanation of the drawing]

[0008] [Figure 1] Cross-sectional view of the optical system of Example 1. [Figure 2] Longitudinal aberration diagram of the optical system in Example 1. [Figure 3] Cross-sectional view of the optical system in Example 2. [Figure 4] Longitudinal aberration diagram of the optical system in Example 2. [Figure 5] A schematic diagram of an imaging device equipped with the optical system of each embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] Figures 1 and 3 show the optical system configurations of Example 1 and Example 2, respectively. Figures 1 and 3 also show the optical paths of the on-axial beam and the beam with the maximum half-angle of view. In each figure, the left side is the object side and the right side is the image side.

[0011] The optical systems of each embodiment can be used as imaging optical systems for various imaging devices such as digital cameras, video cameras, broadcast cameras, cinema cameras, surveillance cameras, and silver halide film cameras. Furthermore, the optical systems of each embodiment can also be used as projection optical systems for projectors.

[0012] The optical system of each embodiment includes a meniscus lens (first lens) G1 with negative refractive power disposed closest to the object side, a lens (second lens) G2 with negative refractive power adjacent to the meniscus lens G1 on the image side, and a plurality of lenses disposed on the image side of the lens G2. On the image side of the lens G2, two negative meniscus lenses are included from the object side, and further two or more negative lenses and two or more positive lenses are respectively included.

[0013] Note that the negative lens G2 may be a meniscus lens, or may be another type of lens. Further, a cover glass or the like having no refractive power may be disposed on the object side of the negative meniscus lens G1.

[0014] The optical system of each embodiment preferably has a total field angle of 160° or more. In addition, SP denotes an aperture stop, and IP denotes an image plane. On the image plane IP, an imaging surface (light-receiving surface) of an imaging element or a film surface (photosensitive surface) of a silver halide film is disposed.

[0015] In the optical system of each embodiment, where f1 is the focal length of the negative meniscus lens G1, f12 is the focal length of the air lens between the negative lenses G2, and f is the focal length of the entire optical system, it is preferable to satisfy at least one of the conditions of the following expressions (1) and (2).

[0016] -180.0≦f1 / f≦-35.0 (1) 12.5≦f12 / f≦100.0 (2) In an optical system with a high field angle, the aperture angle at the peripheral portion of the lens disposed on the image side of the negative meniscus lens G1 becomes large. For this reason, there is a risk that light incident on the optical system from the object side and reflected at the peripheral portion of the lens surface on the image side of the negative meniscus lens G1 passes through the lenses after the negative lens G2 and reaches the image plane, causing a ghost. The light that causes a ghost (hereinafter referred to as ghost light) often has high intensity because it reaches the image plane with a single reflection, or is reflected at the lens periphery where the film thickness of the antireflection film is thin. Therefore, it is necessary to prevent such ghost light from reaching the image plane.

[0017] In order to avoid single-reflection ghosts, it is effective to increase the incident angle of light on the peripheral portion of the image-side lens surface of the negative meniscus lens G1, so that the light reflected here is directed in a direction exiting outside the effective diameter. As a method for this, first, increasing the radius of curvature of the image-side lens surface of the negative meniscus lens G1 can be mentioned. By increasing the radius of curvature, the opening angle of the lens surface becomes larger, and the incident light can be reflected outward.

[0018] As a result of the increased radius of curvature, the focal length of the negative meniscus lens G1 becomes longer. For this reason, satisfying the condition of formula (1) is effective.

[0019] If f1 / f exceeds the upper limit of formula (1), the refractive power of the negative meniscus lens G1 becomes too small, making it difficult to maintain the high field angle of the optical system, which is not preferable. If f1 / f falls below the lower limit of formula (1), the opening angle on the image side of the negative meniscus lens G1 becomes too large, and single-reflection ghost light reaches the image plane, which is not preferable.

[0020] It is more preferable to set the lower limit of formula (1) to -170.0, -150.0, -120.0 or -90.0. It is also more preferable to set the upper limit of formula (1) to -40.0, -45.0 or -50.0.

[0021] Secondly, increasing the positive refractive power of the air lens formed by the air gap between the negative meniscus lens G1 and the negative lens G2 can be mentioned. The light reflected by the negative meniscus lens G1 and directed toward the direction outside the effective diameter can be refracted by the positive refractive power of the air lens. For this reason, satisfying the condition of formula (2) is effective. If f12 / f exceeds the upper limit of formula (2), the refractive power of the air lens becomes too weak, and the single-reflection ghost light reaches the image plane without exiting outside the effective diameter, which is not preferable. If f12 / f falls below the lower limit of formula (2), the positive refractive power of the air lens becomes too strong, and the combined focal length of the negative meniscus lens G1 and the negative lens G2 becomes too weak. As a result, the high field angle of the optical system cannot be maintained, which is not preferable.

[0022] Furthermore, it is more preferable to set the lower limit of equation (2) to 20.0, 25.0, or 30.0. Also, it is more preferable to set the upper limit of equation (2) to 90.0, 80.0, 70.0, or 60.0.

[0023] By satisfying the above configuration and conditions, it is possible to provide an optical system that offers a wide field of view while suppressing ghosting.

[0024] Furthermore, it is preferable that the optical system of each embodiment satisfies at least one of the following conditions.

[0025] In each embodiment, the optical system preferably satisfies the following condition (3), where N1 is the refractive index of the negative meniscus lens G1 at the d line.

[0026] 1.60 ≤ N1 ≤ 2.20 (3) If N1 falls below the lower limit of equation (3), the refractive power of the negative meniscus lens G1 becomes too weak, making it impossible to maintain a high angle of view of the optical system, which is undesirable. If N1 exceeds the upper limit of equation (3), the refractive power of the negative meniscus lens G1 becomes too strong, making it difficult to correct the field curvature and astigmatism generated by the negative meniscus lens G1, which is also undesirable.

[0027] Furthermore, it is more preferable to set the lower limit of equation (3) to 1.70, 1.80, or 1.90. Also, it is more preferable to set the upper limit of equation (3) to 2.15, 2.10, or 2.05.

[0028] In each embodiment, the optical system preferably satisfies the following condition (4) when the focal length of the negative lens G2 is f2.

[0029] -80.0 ≤ f² / f ≤ -30.0 (4) If f2 / f falls below the lower limit of equation (4), the refractive power of the negative lens G2 becomes too strong, making it difficult to correct the field curvature and astigmatism generated by the negative lens G2, which is undesirable. Also, the optical material of the negative lens G2 becomes a relatively high-dispersion material, resulting in large chromatic aberrations that are difficult to correct, which is undesirable. If f2 / f exceeds the upper limit of equation (4), the refractive power of the second lens G2 becomes too weak, making it impossible to maintain a high angle of view of the optical system, which is undesirable.

[0030] Furthermore, it is more preferable to set the lower limit of equation (4) to -70.0, -65.0, or -60.0. Also, it is more preferable to set the upper limit of equation (4) to -20.0, -30.0, or -40.0.

[0031] In each embodiment, the optical system preferably satisfies the following condition (5), where N2 is the refractive index of the negative lens G2 at the d line.

[0032] 1.60 ≤ N2 ≤ 2.20 (5) If N2 falls below the lower limit of equation (5), the refractive power of the negative lens G2 becomes too weak, making it impossible to maintain a high angle of view of the optical system, which is undesirable. If N2 exceeds the upper limit of equation (5), the refractive power of the negative lens G2 becomes too strong, making it difficult to correct the field curvature and astigmatism generated by the negative meniscus lens G1, which is also undesirable. Furthermore, if the optical material of the negative lens G2 becomes a relatively high-dispersion material, the chromatic aberration generated by the negative lens G2 becomes large, and its correction becomes difficult, which is also undesirable.

[0033] Furthermore, it is more preferable to set the lower limit of equation (5) to 1.70, 1.80, or 1.90. Also, it is more preferable to set the upper limit of equation (5) to 2.15 or 2.10.

[0034] In the optical system of each embodiment, it is preferable that the negative 2 lens G2 is a meniscus lens with a convex surface facing the object. By having the object-side lens surface of the negative 2 lens G2 convex toward the object, it is possible to strengthen the positive refractive power of the air lens.

[0035] In the optical system of each embodiment, let R11 be the radius of curvature of the object-side lens surface of the negative meniscus lens G1, R12 be the radius of curvature of the image-side lens surface of the negative meniscus lens G1, and S1 = (R11 - R12) / (R11 + R12) be the shape factor of the negative meniscus lens G1. In this case, it is preferable that the following condition of equation (6) is satisfied.

[0036] 0.10 ≤ S1 ≤ 0.40 (6) If S1 exceeds the upper limit of equation (6), the refractive power of the negative meniscus lens G1 becomes too weak, making it difficult to capture light rays at high angles of view, which is undesirable. If S1 falls below the lower limit of equation (6), the refractive power of the negative meniscus lens G1 becomes too strong, increasing the opening angle of the image-side lens surface. As a result, ghosting due to one-time reflections is more likely to occur, which is undesirable. Furthermore, off-axis aberrations such as field curvature, astigmatism, and chromatic aberration occur in large quantities, making their correction difficult, which is also undesirable.

[0037] Furthermore, it is more preferable to set the lower limit of equation (6) to 0.15, 0.17, or 0.19. Also, it is more preferable to set the upper limit of equation (6) to 0.35, 0.30, or 0.26.

[0038] In the optical system of each embodiment, let R21 be the radius of curvature of the object-side lens surface of the negative lens G2, and R22 be the radius of curvature of the image-side lens surface of the negative lens G2, and let S2 = (R21 - R22) / (R21 + R22) be the shape factor of the negative lens G2. In this case, it is preferable that the following condition of equation (7) is satisfied.

[0039] 0.10 ≤ S² ≤ 0.50 (7) If S2 exceeds the upper limit of equation (7), the refractive power of the negative lens G2 becomes too weak, making it difficult to capture high-angle light rays, which is undesirable. If S2 falls below the lower limit of equation (7), the refractive power of the negative lens G2 becomes too strong, increasing the opening angle of the image-side lens surface. This is undesirable because it makes it easier for ghosting due to one-time reflections to occur. Furthermore, off-axis aberrations such as field curvature, astigmatism, and chromatic aberration become large, and these become difficult to correct, which is also undesirable.

[0040] Furthermore, it is more preferable to set the lower limit of equation (7) to 0.14 or 0.18. Also, it is more preferable to set the upper limit of equation (7) to 0.40 or 0.30.

[0041] In the optical system of each embodiment, let R12 be the radius of curvature of the object-side lens surface of the air lens between the negative meniscus lens G1 and the negative lens (meniscus lens) G2, R21 be the radius of curvature of the image-side lens surface of the air lens, and S2 = (R12 - R21) / (R12 + R21) be the shape factor of the air lens. In this case, it is preferable that the following condition of equation (8) is satisfied.

[0042] -0.03 ≤ S12 ≤ 0.03 (8) If S12 exceeds the upper limit of equation (8), the refractive power of the negative lens G2 becomes too weak, making it difficult to capture high-angle light rays, which is undesirable. If S12 falls below the lower limit of equation (8), the refractive power of the negative lens G2 becomes too strong, increasing the opening angle of the image-side lens surface. This is undesirable because it makes it easier for single-reflection ghosting to occur. Furthermore, it is undesirable because it causes significant off-axis aberrations such as field curvature, astigmatism, and chromatic aberration, making their correction difficult.

[0043] Furthermore, it is more preferable to set the lower limit of equation (8) to -0.02 or -0.01. Also, it is more preferable to set the upper limit of equation (8) to 0.02 or 0.01.

[0044] In order to image light rays with a wider field of view, the optical system of each embodiment preferably satisfies the following condition (9), where ω is the maximum half-angle of view.

[0045] 90.0°≦ω (9) Furthermore, it is more preferable to set the lower limit of equation (9) to 150.0° or 179.9°.

[0046] In order to image light rays with a high angle of view of 180° or more, the optical system of each embodiment preferably satisfies the following condition of equation (10), where θ is the half-opening angle at the position of the maximum effective diameter on the object-side lens surface of the negative meniscus lens G1.

[0047] 90.0°≦θ≦180.0° (10) Furthermore, it is more preferable to set the lower limit of equation (10) to 92.6° or 95.3°. Also, it is more preferable to set the upper limit of equation (10) to 153.4° or 126.7°.

[0048] Numerical examples 1 and 2, corresponding to Examples 1 and 2 respectively, are shown below. The surface number i indicates the order of the surfaces when counted from the object surface, r is the radius of curvature of the i-th surface, and d indicates the lens thickness or air gap on the optical axis between the i-th surface and the (i+1)th surface. nd is the refractive index of the optical material at the d-line between the i-th surface and the (i+1)th surface. νd is the Abbe number with respect to the d-line of the optical material between the i-th surface and the (i+1)th surface. The Abbe number νd with respect to the d-line is expressed as νd = (Nd-1) / (NF-NC), where Nd, NF, and NC are the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm).

[0049] Furthermore, d, focal length (mm), F-number, and half-angle of view (°) are values ​​obtained when the optical system is focused on an object at infinity. BF (back focus) is the distance along the optical axis from the image-side lens surface (final surface) of the optical system to the paraxial image plane, expressed in terms of air equivalent length. The total length of the lens is the distance along the optical axis from the object-side lens surface (frontmost surface) to the final surface of the optical system, plus the back focus.

[0050] The asterisk (*) next to the surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following formula, where x is the displacement from the surface vertex in the direction of the optical axis, h is the height from the optical axis in the direction perpendicular to the optical axis, the direction of light propagation is positive, R is the radius of paraxial curvature, K is the cone constant, and A4, A6, A8, A10 are aspherical coefficients.

[0051] x=( h 2 / R) / [1+√{1-(1+k)(h / R) 2}] +A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 It is expressed as follows. The cone constant and aspheric coefficient "e±Z" are ×10 ±Z It means...

[0052] Furthermore, Figures 2 and 4 show the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical systems of Examples 1 and 2, respectively. In the spherical aberration diagram, Fno indicates the F number, the solid line shows the spherical aberration at the d line (wavelength 587.6 nm), and the dashed line shows the spherical aberration at the g line (wavelength 435.8 nm). In the astigmatism diagram, the solid line S shows the astigmatism at the sagittal image plane, and the dashed line M shows the astigmatism at the meridional image plane. The distortion diagram shows the distortion at the d line. Note that the distortion is calculated based on equidistant projection. The chromatic aberration diagram shows the lateral chromatic aberration at the g line. ω is the half-angle of view (°). [Numerical Example 1] Unit: mm Surface data Face number rd nd νd 1 51.037 2.50 2.00502 28.9 2 30.339 18.85 3 30.875 2.00 1.90984 36.4 4 17.114 10.08 5 31.645 1.50 1.96763 25.9 6 8.583 11.13 7 -14.184 0.80 1.87280 40.5 8 12.756 1.72 9 26.631 6.23 1.87141 23.6 10 -15.148 3.46 11 -13.598 0.80 1.92845 34.6 12 -17.977 1.04 13 31.410 6.38 1.71016 30.9 14 -15.500 0.48 15 -9.748 0.50 1.49802 79.3 16 -79.400 1.00 17 17.151 1.19 1.91277 36.1 18 -25.037 0.53 19 (aperture) ∞ 0.41 20 -13.139 0.50 1.82135 22.9 21 10.101 0.30 22 9.772 2.02 1.78043 48.7 23 145.789 0.30 24 150.450 1.03 1.76147 50.7 25 -12.785 0.40 26 8.793 1.35 1.50466 80.3 27 -9.126 0.32 28 -8.598 1.00 1.80815 22.8 29 -9.445 0.36 30 -7.249 0.80 1.81135 22.8 31 12.536 0.39 32 23.338 1.34 1.72923 54.7 33 -14.200 4.34 Image plane ∞ Various data Focal length 1.42 F-number 2.79 Half-angle (°): 185.0 Image height 4.00 Lens length: 85.02 BF 4.34 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd 1 71.897 5.00 2.00100 29.1 2 39.099 22.20 3 37.580 2.50 2.00100 29.1 4 23.676 12.00 5* 31.554 2.00 1.88668 38.8 6 12.410 8.37 7 78.963 1.00 1.59522 67.7 8 12.638 5.16 9 -15.698 0.80 1.59522 67.7 10 11.710 2.30 11* 40.794 2.95 1.96568 24.9 12 -509.283 0.30 13 1062.045 4.21 1.93160 33.8 14* -17.841 7.92 15* -12.309 0.80 1.81466 22.8 16 -16.614 0.75 17 20.369 2.64 1.59513 67.5 18 341.584 1.20 19 273.339 2.16 1.72922 54.7 20 -16.554 0.41 21 -9.991 0.50 1.49700 81.5 22 -37.488 0.85 23 15.501 1.48 1.80725 46.0 24 -23.981 0.48 25 (aperture) ∞ 0.39 26* -12.961 0.50 1.69301 29.3 27 10.172 0.47 28 11.950 1.09 1.73908 53.4 29 189.429 0.30 30 299.903 0.91 1.65588 61.0 31 -14.519 0.31 32 10.859 1.11 1.49700 81.5 33 -11.802 0.75 34 -10.865 0.80 1.80810 22.8 35 12.142 0.44 36 25.444 1.20 1.77250 49.6 37* -141.365 0.30 38 209.095 1.21 1.59522 67.7 39 -13.727 3.10 Image plane ∞ Aspherical data 5th page K = 0.00000e+00 A 4=-8.10166e-06 A 6= 1.38874e-08 A 8=-3.09318e-11 A10 = 3.96310e-14 Page 11 K = 0.00000e+00 A 4=-2.38743e-05 A 6=-8.27601e-07 A 8=-7.32387e-09 A10 = -2.64958e-11 Side 14 K = 0.00000e+00 A 4=-2.21199e-06 A 6=-3.65149e-07 A 8=-4.42720e-10 A10 = 2.22297e-11 Page 15 K = 0.00000e+00 A 4= 8.11020e-05 A 6=-2.08816e-08 A 8= 1.94718e-07 A10 = -4.55195e-09 Page 26 K = 0.00000e+00 A 4=-2.50906e-04 A 6=-1.88517e-04 A 8= 1.20885e-04 A10 = -2.18158e-05 Page 37 K = 0.00000e+00 A 4=-5.47859e-05 A 6=-2.97190e-05 A 8= 4.25749e-07 A10 = -1.66408e-07 Various data Focal length 1.55 F-number 2.79 Half-angle (°): 185.0 Image height 4.00 Lens length: 100.86 BF 3.10 Table 1 summarizes the values ​​corresponding to equations (1) to (10) in numerical examples 1 and 2. Table 1 shows the values ​​for the d-line as the reference wavelength.

[0053] [Table 1]

[0054] [Imaging device] Figure 5 shows a digital still camera as an imaging device equipped with the optical systems of Examples 1 and 2. 10 is the camera body, and 11 is the imaging optical system composed of the optical systems of Examples 1 and 2. The imaging optical system 11 may be detachable from the camera body 12, or it may be integrated into the camera body 12. 12 is an image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor, which is built into the camera body 11 and converts the subject image formed by the imaging optical system 11 into photoelectric data (i.e., images the subject through the optical system).

[0055] By using the optical systems of each embodiment, a compact imaging device with high optical performance can be obtained.

[0056] Furthermore, if the imaging device is of the interchangeable lens type, it may be a single-lens reflex camera with a quick-turn mirror, or a mirrorless camera without a quick-turn mirror.

[0057] The above embodiments include the following configuration.

[0058] (Composition 1) An optical system comprising a first lens, which is a negative refractive meniscus lens positioned closest to the object, and a second lens with negative refractive power adjacent to the first lens on the image side, The total field of view of the optical system is 160° or more. When the focal length of the first lens is f1, the focal length of the air lens between the first lens and the second lens is f12, and the focal length of the optical system is f, -180.0 ≤ f1 / f ≤ -35.0 12.5 ≤ f12 / f ≤ 100.0 An optical system characterized by satisfying the following conditions. (Configuration 2) When the refractive index of the first lens at the d line is N1, 1.60 ≤ N1 ≤ 2.20 The optical system according to configuration 1, characterized by satisfying the following conditions. (Composition 3) When the focal length of the second lens is f2, -80.0 ≤ f² / f ≤ -30.0 The optical system according to configuration 1 or 2, characterized by satisfying the following conditions. (Composition 4) When the refractive index of the second lens at the d line is N2, 1.60 ≤ N2 ≤ 2.20 An optical system according to any one of configurations 1 to 3, characterized by satisfying the following conditions. (Composition 5) The optical system according to any one of configurations 1 to 4, characterized in that the second lens is a meniscus lens with a convex surface facing the object. (Composition 6) When the radius of curvature of the object-side lens surface of the first lens is R11, the radius of curvature of the image-side lens surface of the first lens is R12, and the shape factor of the first lens is S1 = (R11 - R12) / (R11 + R12), 0.10 ≤ S1 ≤ 0.40 An optical system according to any one of configurations 1 to 5, characterized by satisfying the following conditions. (Composition 7) When the radius of curvature of the object-side lens surface of the second lens is R21, the radius of curvature of the image-side lens surface of the second lens is R22, and the shape factor of the second lens is S2 = (R21 - R22) / (R21 + R22), 0.10 ≤ S² ≤ 0.50 An optical system according to any one of configurations 1 to 6, characterized by satisfying the following conditions. (Composition 8) When the radius of curvature of the object-side lens surface of the air lens is R12, the radius of curvature of the image-side lens surface of the air lens is R21, and the shape factor of the air lens is S2 = (R12 - R21) / (R12 + R21), -0.03 ≤ S12 ≤ 0.03 An optical system according to any one of configurations 1 to 7, characterized by satisfying the following conditions. (Composition 9) When the maximum half-angle of view of the optical system is ω, 90.0°≦ω An optical system according to any one of configurations 1 to 8, characterized by satisfying the following conditions. (Composition 10) When θ is the half-opening angle at the position of the effective diameter on the object-side lens surface of the first lens, 90.0°≦θ≦180.0° An optical system according to any one of configurations 1 to 9, characterized by satisfying the following conditions. (Composition 11) The first lens is a meniscus lens with negative refractive power, located closest to the object. When N1 is the refractive index of the first lens at the d line and θ is the half-opening angle at the position of the effective diameter on the object-side lens surface of the first lens, 1.60 ≤ N1 ≤ 2.20 90.0°≦θ≦180.0° An optical system according to any one of configurations 1 to 10, characterized by satisfying the following conditions. (Composition 12) The first lens is a meniscus lens with negative refractive power positioned closest to the object, The first lens is adjacent to a second lens with negative refractive power on the image side. An optical system characterized by having a total field of view of 160° or more. (Composition 13) The optical system described in any one of configurations 1 to 12, An imaging device characterized by having an image sensor that captures an image of a subject through the optical system.

[0059] The embodiments described above are merely representative examples, and various modifications and changes can be made to each embodiment when implementing the present invention. [Explanation of Symbols]

[0060] G1 Negative Meniscus Lens (First Lens) G2 Negative Lens (Second Lens) IP image plane

Claims

1. An optical system comprising a first lens, which is a negative refractive meniscus lens positioned closest to the object, and a second lens with negative refractive power adjacent to the first lens on the image side, The total field of view of the optical system is 160° or more. When the focal length of the first lens is f1, the focal length of the air lens between the first lens and the second lens is f12, and the focal length of the optical system is f, -180.0 ≤ f1 / f ≤ -35.0 12.5 ≤ f12 / f ≤ 100.0 An optical system characterized by satisfying the following conditions.

2. When the refractive index of the first lens at the d-line is N1, 1.60 ≤ N1 ≤ 2.20 The optical system according to claim 1, characterized in that it satisfies the following conditions.

3. When the focal length of the second lens is f2, -80.0 ≤ f² / f ≤ -30.0 The optical system according to claim 1, characterized in that it satisfies the following conditions.

4. When the refractive index of the second lens at the d-line is N2, 1.60 ≤ N2 ≤ 2.20 The optical system according to claim 1, characterized in that it satisfies the following conditions.

5. The optical system according to claim 1, characterized in that the second lens is a meniscus lens with a convex surface facing the object.

6. When the radius of curvature of the object-side lens surface of the first lens is R11, the radius of curvature of the image-side lens surface of the first lens is R12, and the shape factor of the first lens is S1 = (R11 - R12) / (R11 + R12), 0.10 ≤ S1 ≤ 0.40 The optical system according to claim 1, characterized in that it satisfies the following conditions.

7. When the radius of curvature of the object-side lens surface of the second lens is R21, the radius of curvature of the image-side lens surface of the second lens is R22, and the shape factor of the second lens is S2 = (R21 - R22) / (R21 + R22), 0.10 ≤ S² ≤ 0.50 The optical system according to claim 1, characterized in that it satisfies the following conditions.

8. When the radius of curvature of the object-side lens surface of the air lens is R12, the radius of curvature of the image-side lens surface of the air lens is R21, and the shape factor of the air lens is S2 = (R12 - R21) / (R12 + R21), -0.03 ≤ S12 ≤ 0.03 The optical system according to claim 1, characterized in that it satisfies the following conditions.

9. When the maximum half-angle of view of the optical system is ω, 90.0°≦ω The optical system according to claim 1, characterized in that it satisfies the following conditions.

10. When θ is the half-opening angle at the position of the effective diameter on the object-side lens surface of the first lens, 90.0° ≤ θ ≤ 180.0° The optical system according to claim 1, characterized in that it satisfies the following conditions.

11. The first lens is a meniscus lens with negative refractive power, located closest to the object. When the refractive index of the first lens at the d-line is N1, and the half-opening angle at the position of the effective diameter on the object-side lens surface of the first lens is θ, 1.60 ≤ N1 ≤ 2.20 90.0° ≤ θ ≤ 180.0° The optical system according to claim 1, characterized in that it satisfies the following conditions.

12. The first lens is a meniscus lens with negative refractive power positioned closest to the object, The first lens is adjacent to a second lens with negative refractive power on the image side. An optical system characterized by having a total field of view of 160° or more.

13. An optical system according to any one of claims 1 to 12, An imaging device characterized by having an image sensor that captures an image of a subject through the optical system.

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