A fisheye lens

Abstract

The invention discloses a fisheye lens, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence from an object plane to an image plane along an optical axis, wherein the first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens, the fifth lens is a positive power lens, the sixth lens is a negative power lens, the seventh lens is a positive power lens, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the fifth lens is f3, the focal length of the sixth lens is f4, the focal length of the sixth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, the focal length of the seventh lens is f8, the focal length of the seventh lens is f9, the focal length of the seventh lens is f11, the focal length of the seventh lens is f12, the focal length of the seventh lens is f13, the focal length of the seventh lens is f14, the focal length of the seventh lens is f15, the focal length of the seventh lens is f16, the focal length of the seventh lens is f17, the focal length of the seventh lens is f18, the focal length of the seventh lens is f29, the focal length of the seventh lens is f30, the focal length of the seventh lens is f31, the focal length of the seventh lens is f32, the focal length of the seventh lens is f33, the focal length of the seventh lens is f34, the focal length of the seventh lens is f35, the focal length of the seventh lens is f36, the focal length of the seventh lens is f37, the focal length of the seventh lens is f38, the focal length of the seventh lens is f39, the focal length of the seventh lens is f41, the focal length of the seventh lens is f42, the focal length of the seventh lens is f43, the focal length of the seventh lens is f44, the focal length of the seventh lens is f5 The focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the fisheye lens is f, wherein: 2.8≤|f1 / f|≤4.6, 0.6≤|f2 / f|≤3.2, |f3 / f|≥1.2, 2.3≤|f4 / f|≤4.1, 0.6≤|f5 / f|≤2.9, 0.32≤|f6 / f|≤2.47, 0.28≤|f7 / f|≤3.6. The fisheye lens provided by the present invention improves the imaging quality and meets the requirements of high-definition image quality.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of optical devices, and in particular to a fisheye lens. Background Art

[0002] Fisheye lens is a super fisheye lens with a shorter focal length and an angle close to or even exceeding 180°. It is called fisheye lens because its structure is similar to the eyes of fish. Due to its large field of view, fisheye lens can accommodate more scenes and can meet the shooting needs of many narrow spaces. With the popularization of digitalization, it is very convenient for fisheye lens to achieve 360-degree panoramic effect. However, due to the large optical distortion of fisheye lens, the edge image is severely deformed and compressed, so the image quality is poor and cannot meet the current needs of high-definition image quality. Summary of the invention

[0003] The present invention provides a fisheye lens to improve imaging quality and meet the requirements of high-definition image quality.

[0004] In a first aspect, an embodiment of the present invention provides a fisheye lens, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence from an object plane to an image plane along an optical axis;

[0005] The first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens, the fifth lens is a positive power lens, the sixth lens is a negative power lens, and the seventh lens is a positive power lens;

[0006] The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the fisheye lens is f, wherein:

[0007] 2.8≤|f1 / f|≤4.6; 0.6≤|f2 / f|≤3.2; |f3 / f|≥1.2; 2.3≤|f4 / f|≤4.1; 0.6≤|f5 / f|≤2.9; 0.32≤|f6 / f|≤2.47; 0.28≤|f7 / f|≤3.6.

[0008] Optionally, the first lens and the fourth lens are both glass spherical lenses; the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are all plastic aspherical lenses;

[0009] The fisheye lens further includes a stop, which is disposed in an optical path between the fourth lens and the fifth lens.

[0010] Optionally, the refractive index of the first lens is n1, and the Abbe number is v1; the refractive index of the third lens is n3; and the refractive index of the fourth lens is n4; wherein: n1≥1.6, v1≥17; n3≥1.51; and n4≥1.65.

[0011] Optionally, a clear aperture of the first lens is D1, and a distance from an optical axis center of the image-side surface of the seventh lens to an image plane is BFL, wherein BFL / D1≥0.16.

[0012] Optionally, the radius of curvature of the object side surface of the second lens is R21, the radius of curvature of the image side surface of the second lens is R22, the radius of curvature of the object side surface of the seventh lens is R71, and the radius of curvature of the image side surface of the seventh lens is R72, wherein 0.8≤|R21 / R22|≤6.1, and / or, 0.2≤|R71 / R72|≤1.4.

[0013] Optionally, the air interval from the third lens to the fourth lens is TH34, and the air interval from the fifth lens to the sixth lens is TH56, wherein TH34≥0, and / or TH56≥0.

[0014] Optionally, the distance from the optical axis center of the image side surface of the seventh lens to the image plane is BFL, and the distance from the optical axis center of the object side surface of the first lens to the image plane is TTL, wherein 0.06≤BFL / TTL≤0.89.

[0015] Optionally, the aperture number of the fisheye lens is F, where 1.8≤F≤2.2.

[0016] Optionally, the horizontal field of view angle of the fisheye lens is FOV-H, and the diagonal field of view angle of the fisheye lens is FOV-D, wherein 175°≤FOV-H≤190°, and 180°≤FOV-D≤205°.

[0017] Optionally, the incident angle of the principal ray corresponding to the maximum field angle of the fisheye lens on the image plane is CRA, where CRA≤15°.

[0018] The fisheye lens provided in the embodiment of the present invention ensures the balance of the incident angles of the front and rear lens groups of the fisheye lens at a low cost by reasonably setting the number of lenses in the fisheye lens, the optical power of each lens, and the relative relationship between the focal lengths of each lens, thereby reducing the sensitivity of the lens, improving the possibility of production, ensuring that the fisheye lens has a high resolution, improving the imaging quality, and meeting the requirements of high-definition image quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A schematic diagram of the structure of a fisheye lens provided by an embodiment of the present invention;

[0020] Figure 2 A spherical aberration curve diagram of a fisheye lens provided by an embodiment of the present invention;

[0021] Figure 3 A light fan diagram of a fisheye lens provided by an embodiment of the present invention;

[0022] Figure 4 A visible light point diagram of a fisheye lens provided by an embodiment of the present invention;

[0023] Figure 5 A vertical axis chromatic aberration diagram of a fisheye lens provided by an embodiment of the present invention;

[0024] Figure 6 A field curvature distortion diagram of a fisheye lens provided by an embodiment of the present invention;

[0025] Figure 7 An F-Theta distortion diagram of a fisheye lens provided by an embodiment of the present invention;

[0026] Figure 8 This is an MTF diagram of a fisheye lens provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0028] Figure 1 A schematic diagram of the structure of a fisheye lens provided by an embodiment of the present invention is shown in FIG. Figure 1As shown, the fisheye lens provided by the embodiment of the present invention comprises a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160 and a seventh lens 170 which are arranged in sequence from the object plane to the image plane along the optical axis; the first lens 110 is a negative power lens, the second lens 120 is a negative power lens, the third lens 130 is a positive power lens, the fourth lens 140 is a positive power lens, the fifth lens 150 is a positive power lens, the sixth lens 160 is a negative power lens, and the seventh lens 170 is a positive power lens; the focal length of the first lens 110 is f1, the focal length of the second lens 120 is f2, the focal length of the third lens 130 is f3, the focal length of the fourth lens 140 is f4, the focal length of the fifth lens 150 is f5, the focal length of the sixth lens 160 is f6, the focal length of the seventh lens 170 is f7, and the focal length of the fisheye lens is f, wherein 2.8≤|f1 / f|≤4.6; 0.6≤|f2 / f|≤3.2; |f3 / f|≥1.2; 2.3≤|f4 / f|≤4.1; 0.6≤|f5 / f|≤2.9; 0.32≤|f6 / f|≤2.47; 0.28≤|f7 / f|≤3.6.

[0029] Exemplarily, the focal length is equal to the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, and it characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal length, the stronger the ability to bend light, and the smaller the absolute value of the focal length, the weaker the ability to bend light. When the focal length is a positive number, the refraction of light is convergent; when the focal length is a negative number, the refraction of light is divergent. The focal length can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (i.e., a lens group). In the fisheye lens provided in this embodiment, each lens can be fixed to a lens barrel ( Figure 1 In the optical system (not shown), the first lens 110 is set as a negative power lens to control the incident angle of light in the optical system; the second lens 120 and the sixth lens 160 are negative power lenses; the third lens 130, the fourth lens 140, the fifth lens 150 and the seventh lens 170 are positive power lenses; the fifth lens 150, the sixth lens 160 and the seventh lens 170 are used to correct off-axis aberrations, including field curvature, coma, astigmatism and other aberrations. The power of the entire fisheye lens is distributed according to a certain ratio to ensure the balance of the incident angles of the front and rear lens groups, so as to reduce the sensitivity of the lens and improve the possibility of production.

[0030] Further, the focal length f1 of the first lens 110, the focal length f2 of the second lens 120, the focal length f3 of the third lens 130, the focal length f4 of the fourth lens 140, the focal length f5 of the fifth lens 150, the focal length f6 of the sixth lens 160, the focal length f7 of the seventh lens 170 and the focal length f of the fisheye lens are set to satisfy: 2.8≤|f1 / f|≤4.6; 0.6≤|f2 / f|≤3.2; |f3 / f|≥1.2; 2.3≤|f4 / f|≤4.1; 0.6≤|f5 / f|≤2.9; 0.32≤|f6 / f|≤2.47; 0.28≤|f7 / f|≤3.6. By rationally allocating the focal lengths of the lenses, it is beneficial to correct aberrations and ensure that the lens has a high resolution.

[0031] Furthermore, the second lens 120 may be a meniscus lens, which is composed of two spherical surfaces with small curvature radii and little numerical difference. By setting the second lens 120 as a meniscus lens, the light incident angle balance tolerance can be alleviated.

[0032] The fisheye lens provided in the embodiment of the present invention ensures the balance of the incident angles of the front and rear lens groups of the fisheye lens at a low cost by reasonably setting the number of lenses in the fisheye lens, the optical power of each lens, and the relative relationship between the focal lengths of each lens, thereby reducing the sensitivity of the lens, improving the possibility of production, ensuring that the fisheye lens has a high resolution, improving the imaging quality, and meeting the requirements of high-definition image quality.

[0033] Optionally, the first lens 110 and the fourth lens 140 are both glass spherical lenses; the second lens 120, the third lens 130, the fifth lens 150, the sixth lens 160 and the seventh lens 170 are all plastic aspherical lenses.

[0034] Among them, the aspherical lens plays a role in correcting all high-order aberrations. Since the cost of plastic lenses is much lower than that of glass lenses, the fisheye lens provided by the embodiment of the present invention has good image quality and low cost by setting 5 plastic aspherical lenses. And because the two types of materials have a mutual compensation effect, it can ensure that the fisheye lens can still be used normally in high and low temperature environments.

[0035] Continue to refer Figure 1 Optionally, the fisheye lens provided in the embodiment of the present invention further includes an aperture 180 , and the aperture 180 is arranged in the optical path between the fourth lens 140 and the fifth lens 150 .

[0036] Among them, by setting the aperture 180 in the light path between the fourth lens 140 and the fifth lens 150, the propagation direction of the light beam can be adjusted, and the incident angle of the light beam can be adjusted, which is beneficial to further improve the imaging quality.

[0037] Optionally, the refractive index of the first lens 110 is n1, and the Abbe number is v1; the refractive index of the third lens 130 is n3; and the refractive index of the fourth lens 140 is n4; wherein: n1≥1.6, v1≥17; n3≥1.51; and n4≥1.65.

[0038] Among them, the refractive index is the ratio of the propagation speed of light in a vacuum to the propagation speed of light in the medium. It is mainly used to describe the material's ability to refract light. Different materials have different refractive indices. The Abbe number is an index used to represent the dispersion ability of a transparent medium. The more severe the dispersion of the medium, the smaller the Abbe number; conversely, the milder the dispersion of the medium, the larger the Abbe number. In this way, by matching the refractive index and Abbe number of each lens in the fisheye lens, the balance of the incident angle of the front and rear lens groups is ensured to reduce the sensitivity of the lens and improve the possibility of production.

[0039] Optionally, the first lens 110 has a light aperture of D1, and the distance from the center of the optical axis of the image-side surface of the seventh lens 170 to the image plane is BFL, wherein BFL / D1≥0.16.

[0040] Among them, the distance from the center of the optical axis of the image-side surface of the seventh lens 170 to the image plane can be understood as the back focus (In air) of the fisheye lens. By reasonably setting the maximum light clearance D1 of the first lens 110 and the back focus BFL of the fisheye lens to satisfy BFL / D1≥0.16, the entire fisheye lens can be kept compact while meeting the amount of light entering the fisheye lens.

[0041] Optionally, the radius of curvature of the object-side surface of the second lens 120 is R21, the radius of curvature of the image-side surface of the second lens 120 is R22, the radius of curvature of the object-side surface of the seventh lens 170 is R71, and the radius of curvature of the image-side surface of the seventh lens 170 is R72, wherein 0.8≤|R21 / R22|≤6.1, and / or, 0.2≤|R71 / R72|≤1.4.

[0042] Specifically, the unit of the radius of curvature is millimeter (mm). By setting the radius of curvature R21 of the object side surface of the second lens 120 and the radius of curvature R22 of the image side surface of the second lens 120 to satisfy 0.8≤|R21 / R22|≤6.1, and / or the radius of curvature R71 of the object side surface of the seventh lens 170 and the radius of curvature R72 of the image side surface of the seventh lens 170 to satisfy 0.2≤|R71 / R72|≤1.4, the object side surface and the image side surface of the second lens 120 and / or the seventh lens 170 are curved in the same direction, which is conducive to realizing the miniaturization design of the fisheye lens. At the same time, by optimizing the shapes of the second lens 120 and the seventh lens 170, it is conducive to improving the imaging quality of the fisheye lens. Among them, the image side surface of the seventh lens 170 can adopt a large convex surface, which plays a role in reducing the incident angle of the image plane light of the fisheye lens.

[0043] Optionally, the air interval between the third lens 130 and the fourth lens 140 is TH34, and the air interval between the fifth lens 150 and the sixth lens 160 is TH56, wherein TH34≥0, and / or TH56≥0.

[0044] Among them, by reasonably constraining the total length of the air space, the lens structure can be made more compact, and the effective focal length and total length of the fisheye lens can be kept within a reasonable range while achieving high image quality.

[0045] Exemplarily, by setting TH34=0, and / or TH56=0, the image side surface of the third lens 130 and the object side surface of the fourth lens 140 can be glued together, and / or the image side surface of the fifth lens 150 and the object side surface of the sixth lens 160 can be glued together, so that the third lens 130 and the fourth lens 140 can be combined into a glued lens, and / or the fifth lens 150 and the sixth lens 160 can be combined into a glued lens; the use of a glued lens can effectively reduce the air gap between the third lens 130 and the fourth lens 140, and / or the air gap between the fifth lens 150 and the sixth lens 160 can be effectively reduced, thereby reducing the total length of the lens. In addition, the glued lens can be used to minimize or eliminate chromatic aberration, so that various aberrations of the fisheye lens can be fully corrected, and the resolution can be improved under the premise of compact structure, and the optical properties such as distortion and CRA can be optimized; and the light loss caused by reflection between lenses can be reduced, and the illumination can be improved, thereby improving the image quality and the clarity of the lens imaging. In addition, the use of cemented lenses can also reduce the number of components between the two lenses, simplify the assembly process during the lens manufacturing process, reduce costs, and reduce the tolerance sensitivity of the lens unit due to tilt / eccentricity caused during the assembly process.

[0046] Optionally, the distance from the optical axis center of the image-side surface of the seventh lens 170 to the image plane is BFL, and the distance from the optical axis center of the object-side surface of the first lens 110 to the image plane is TTL, wherein 0.06≤BFL / TTL≤0.89.

[0047] Among them, the distance BFL from the optical axis center of the image side surface of the seventh lens 170 to the image plane can be understood as the back focus of the fisheye lens, and the distance TTL from the optical axis center of the object side surface of the first lens 110 to the image plane can be understood as the total length of the fisheye lens. By reasonably setting the relationship between the back focus of the fisheye lens and the total length of the fisheye lens, the entire fisheye lens structure can be compact and the fisheye lens can be highly integrated.

[0048] Optionally, the aperture number of the fisheye lens provided in the embodiment of the present invention is F, where 1.8≤F≤2.2.

[0049] The fisheye lens provided by the embodiment of the present invention can meet the requirement of a larger light throughput, thereby meeting the monitoring requirements under low illumination conditions.

[0050] Optionally, the horizontal field of view angle of the fisheye lens provided in the embodiment of the present invention is FOV-H, and the diagonal field of view angle of the fisheye lens is FOV-D, wherein 175°≤FOV-H≤190°, and 180°≤FOV-D≤205°.

[0051] The fisheye lens provided in the embodiment of the present invention is a fisheye lens with an ultra-large field of view, which meets the requirement of an ultra-large field of view.

[0052] Optionally, the incident angle of the principal ray on the image plane corresponding to the maximum field angle of the fisheye lens provided in the embodiment of the present invention is CRA, where CRA≤15°.

[0053] Among them, by limiting the incident angle CRA of the principal ray corresponding to the maximum field angle of the fisheye lens on the image plane, the angle at which the light in the system is incident on the photosensitive element can be effectively suppressed to improve the sensitivity of the fisheye lens on the photosensitive element.

[0054] The fisheye lens provided in the embodiment of the present invention ensures the balance of the incident angles of the front and rear lens groups of the fisheye lens at a low cost by reasonably allocating the optical power, surface shape, refractive index, Abbe number, etc. of each lens, reduces the sensitivity of the lens, ensures that the fisheye lens has a high resolution, improves the imaging quality, and meets the requirements of high-definition image quality.

[0055] As a feasible implementation manner, the curvature radius, thickness, material and K factor of each lens surface in the fisheye lens are described below.

[0056] Table 1 Design values ​​of curvature radius, thickness, material and K factor of fisheye lens

[0057] Surface number Surface type Radius of curvature thickness Materials (n.d.) K Factor 1 Spherical 11.41 0.6 1.88 2 Spherical 3.75 2.05 3 Aspheric 8.81 0.7 1.53 -3.56 4 Aspheric 1.56 1.04 -0.79 5 Aspheric 4.86 0.70 1.66 -7.39 6 Aspheric 7.08 0.04 -5.35 7 Spherical 12.71 2.38 2.10 8 Spherical -12.71 0.03 STO PL Infinity 0.10 10 Aspheric 5.36 1.61 1.53 -14.36 11 Aspheric -2.80 0.05 0.57 12 Aspheric -1.75 0.79 1.66 1.76E-003 13 Aspheric 40.31 0.09 -475.4 14 Aspheric 2.57 3.11 1.53 -10.74 15 Aspheric -3.19 0.49 -0.23

[0058] Continue to refer Figure 1The fisheye lens provided in the embodiment of the present invention comprises a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160 and a seventh lens 170 arranged in sequence from the object plane to the image plane along the optical axis. Table 1 shows the optical physical parameters such as the radius of curvature, thickness and material of each lens in the fisheye lens provided in the embodiment. Among them, the surface number is numbered according to the surface order of each lens, for example, "1" represents the object surface of the first lens 110, "2" represents the image surface of the first lens 110, "10" represents the object surface of the fifth lens 150, "11" represents the image surface of the fifth lens 150, and so on; the radius of curvature represents the curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side; the thickness represents the central axial distance from the current surface to the next surface, and the units of the radius of curvature and thickness are both millimeters (mm).

[0059] On the basis of the above implementation, optionally, the third lens 130 and the fourth lens 140 are glass spherical lenses, and the first lens 110, the second lens 120, the fifth lens 150, the sixth lens 160 and the seventh lens 170 are all plastic aspherical lenses. The fisheye lens provided in the embodiment of the present invention also includes an aperture 180 (STO). By adding the aperture 180, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality. The aperture 180 can be located in the optical path between the fourth lens 140 and the fifth lens 150, but the embodiment of the present invention does not limit the specific setting position of the aperture 180. By setting the aperture at a suitable position, it is helpful to improve the relative illumination and reduce the CRA.

[0060] The aspherical surface shape equation Z of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160 and the seventh lens 170 satisfies:

[0061]

[0062] Wherein, Z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of y along the optical axis; c = 1 / R, R represents the paraxial curvature radius of the mirror surface; K is the cone coefficient; A, B, C, D, E, and F are high-order aspheric coefficients, where the units of Z, R, and y are all mm.

[0063] Exemplarily, Table 2 describes in detail the aspheric coefficients of each lens in this embodiment in a feasible implementation manner.

[0064] Table 2 Aspheric coefficients in fisheye lenses

[0065]

[0066]

[0067] Among them, 1.19E-03 means that the coefficient A of face number 3 is 1.19*10 -3 , and so on.

[0068] The F-Theta distortion of the fisheye lens provided by the embodiment of the present invention is positive distortion, and the F-Theta distortion is ≤10%; and the infrared defocus of the fisheye lens is within 10um.

[0069] Furthermore, Figure 2 A spherical aberration curve diagram of a fisheye lens provided by an embodiment of the present invention, such as Figure 2 As shown, the spherical aberration of the fisheye lens at different wavelengths (0.486 μm, 0.588 μm and 0.656 μm) is within 0.05 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of the fisheye lens is very small. Therefore, it can be seen that the fisheye lens provided by the embodiment of the present invention can correct the aberration well.

[0070] Figure 3 A light fan diagram of a fisheye lens provided by an embodiment of the present invention, such as Figure 3 As shown, the imaging range of different wavelengths of light (0.486μm, 0.588μm and 0.656μm) at different field angles of the fisheye lens is all within 50μm and the curve is very concentrated, ensuring that the aberration in different field areas is small, which means that the fisheye lens can better correct the aberration of the optical system.

[0071] Figure 4 The present invention provides a visible light spot diagram of a fisheye lens, wherein the spot diagram is one of the most commonly used evaluation methods in modern optical design. The spot diagram refers to a diffuse pattern formed by a plurality of light rays emitted by a point light source after passing through an optical system, where the intersection points of the light rays with the image plane are no longer concentrated at the same point due to aberration, but are scattered over a certain range. Figure 4As shown, in the fisheye lens provided by the embodiment of the present invention, the diffusion patterns of visible light of different wavelengths (0.4861μm, 0.5876μm and 0.6563μm) in each field of view are relatively concentrated and evenly distributed, and there is no phenomenon in which the diffusion pattern in a certain field of view is separated widely up and down with the wavelength, indicating that there is no obvious purple fringing. At the same time, the root mean square radius values ​​(RMSradius) of visible light of different wavelengths (0.4861μm, 0.5876μm and 0.6563μm) at each field of view of the fisheye lens are 2.180mm, 1.819mm, 1.826mm, 1.927mm, 2.065mm, 1.928mm, 2.105mm, 2.377mm and 4.857mm, respectively, indicating that the RMS radius of each field of view is less than 5μm, which means that the fisheye lens has lower chromatic aberration and aberration in the full field of view, solves the purple fringing problem of imaging in the visible light band, and can achieve high-resolution imaging.

[0072] Figure 5 A vertical axis chromatic aberration diagram of a fisheye lens provided in an embodiment of the present invention is shown in FIG. Figure 5 As shown in the figure, the vertical direction represents the normalized field of view angle, 0 represents the optical axis, and the vertical vertex represents the maximum field of view radius; the horizontal direction represents the offset of the meridian range based on 0.587μm, in μm. The numbers on the curve in the figure represent the wavelength represented by the curve, in μm, which is Figure 5 It can be seen that the vertical axis chromatic aberration can be controlled within the range of (-3μm, 14μm).

[0073] Figure 6 A field curvature distortion diagram of a fisheye lens provided by an embodiment of the present invention, such as Figure 6 As shown, in the left coordinate system, the horizontal coordinate represents the magnitude of field curvature, in mm; the vertical coordinate represents the normalized image height, without unit; T represents meridian, S represents arc loss; Figure 6 It can be seen that the fisheye lens provided in this embodiment is effectively controlled in field curvature from light with a wavelength of 486nm to light with a wavelength of 656nm, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the coordinate system on the right, the horizontal coordinate represents the size of the distortion, in units of %; the vertical coordinate represents the normalized image height, without units; Figure 6 It can be seen that the distortion of the fisheye lens provided in this embodiment is well corrected, the imaging distortion is small, and the requirement of low distortion is met.

[0074] Figure 7 An F-Theta distortion diagram of a fisheye lens provided by an embodiment of the present invention, such as Figure 7As shown, the F-Theta distortion of the fisheye lens provided by the embodiment of the present invention is positive distortion, and the F-Theta distortion is ≤10%, which shows that the fisheye lens provided by the embodiment of the present invention has a good imaging effect.

[0075] Figure 8 The MTF diagram of a fisheye lens provided by an embodiment of the present invention is as follows: Figure 8 As shown, the transfer functions at 160 line pairs / mm in the MTF curve are basically above 0.2, which can meet the 4K image quality requirements.

[0076] In summary, the fisheye lens provided by the embodiment of the present invention has the advantages of ultra-large field of view, high-definition image quality and no obvious purple fringing. The design adopts a 7-piece structure, which can achieve 4K image quality requirements at a low cost. The glass-plastic hybrid structure can meet the requirement of no focus deviation in an environment of -30℃-80℃.

[0077] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fisheye lens, characterized in that: It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are arranged in sequence from the object plane to the image plane along the optical axis; The first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens, the fifth lens is a positive power lens, the sixth lens is a negative power lens, and the seventh lens is a positive power lens; The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the fisheye lens is f, wherein: 2.8≤|f1 / f|≤4.6; 0.6≤|f2 / f|≤3.2; |f3 / f|≥1.2; 2.3≤|f4 / f|≤4.1; 0.6≤|f5 / f|≤2.9; 0.32≤|f6 / f|≤2.47; 0.28≤|f7 / f|≤3.6; The horizontal field of view angle of the fisheye lens is FOV-H, and the diagonal field of view angle of the fisheye lens is FOV-D, wherein 175°≤FOV-H≤190°, and 180°≤FOV-D≤205°; The incident angle of the chief light corresponding to the maximum field angle of the fisheye lens on the image plane is CRA, where CRA≤15°.

2. The fisheye lens according to claim 1, characterized in that: The first lens and the fourth lens are both glass spherical lenses; the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are all plastic aspherical lenses; The fisheye lens further includes a stop, which is disposed in an optical path between the fourth lens and the fifth lens.

3. The fisheye lens according to claim 1, characterized in that: The refractive index of the first lens is n1, and the Abbe number is v1; the refractive index of the third lens is n3; and the refractive index of the fourth lens is n4; wherein: n1≥1.6, v1≥17; n3≥1.51; and n4≥1.

65.

4. The fisheye lens according to claim 1, characterized in that: The clear aperture of the first lens is D1, and the distance from the center of the optical axis of the image-side surface of the seventh lens to the image plane is BFL, wherein BFL / D1≥0.

16.

5. The fisheye lens according to claim 1, characterized in that: The object side surface of the second lens has a curvature radius of R21, the image side surface of the second lens has a curvature radius of R22, the object side surface of the seventh lens has a curvature radius of R71, and the image side surface of the seventh lens has a curvature radius of R72, wherein 0.8≤|R21 / R22|≤6.1, and / or, 0.2≤|R71 / R72|≤1.

4.

6. The fisheye lens according to claim 1, characterized in that: The air interval between the third lens and the fourth lens is TH34, and the air interval between the fifth lens and the sixth lens is TH56, wherein TH34≥0, and / or TH56≥0.

7. The fisheye lens according to claim 1, characterized in that: The distance from the optical axis center of the image side surface of the seventh lens to the image plane is BFL, and the distance from the optical axis center of the object side surface of the first lens to the image plane is TTL, wherein 0.06≤BFL / TTL≤0.

89.

8. The fisheye lens according to claim 1, characterized in that: The aperture number of the fisheye lens is F, wherein 1.8≤F≤2.2.

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