A low-distortion fisheye lens

Abstract

The present invention discloses a low-distortion fisheye lens, comprising first to sixth lenses arranged sequentially along an optical axis from the object side to the image side. The first lens has negative refractive power, the second lens has negative refractive power, the third lens has positive refractive power, the fourth lens has positive refractive power, the fifth lens has negative refractive power, and the sixth lens has positive refractive power. The low-distortion fisheye lens of the present invention adopts a glass-plastic hybrid design, with an optical TTL of less than 15mm, a small overall lens size, and easy installation and use. The lens F-Theta distortion is controlled within |-5%|, with perfect distortion control, minimal deformation of the edges of the captured image, and is conducive to later image processing. The lens has a large imaging target area, suitable for 1 / 2.7" chips, better photosensitivity, and a low imaging signal-to-noise ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of optical lenses, and in particular to a low-distortion fisheye lens. Background Art

[0002] A fisheye lens has a focal length of 16mm or less and a viewing angle approaching or equal to 180°. It is an extreme wide-angle lens, commonly known as "fisheye lens." To maximize the viewing angle, the front element of this lens has a very short diameter and bulges outward in a parabolic shape, resembling a fish's eye, hence the name "fisheye lens."

[0003] Most existing fisheye lenses have the following problems: many lenses and large lens size make the overall cost and weight of the lens too high, and the installation and use are limited; due to the large field of view of the lens and poor edge distortion control, the captured image is obviously deformed, affecting later image processing; the lens imaging target area is small, the signal-to-noise ratio is high, and the photosensitivity is poor.

[0004] In view of this, the inventors of the present application invented a low-distortion fisheye lens. Summary of the Invention

[0005] The object of the present invention is to provide a low-distortion fisheye lens with small distortion, small volume and large imaging target surface.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a low-distortion fisheye lens comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in sequence along an optical axis from the object side to the image side, wherein each of the first to sixth lenses includes an object-side surface facing the object side and through which imaging light passes, and an image-side surface facing the image side and through which imaging light passes;

[0007] The first lens has a negative refractive power, and the object-side surface of the first lens is convex, and the image-side surface is concave;

[0008] The second lens has a negative refractive power, and the object-side surface of the second lens is convex, and the image-side surface of the second lens is concave;

[0009] The third lens has positive refractive power, and the object-side surface and image-side surface of the third lens are convex;

[0010] The fourth lens element has positive refractive power, and the object-side surface and image-side surface of the fourth lens element are convex;

[0011] The fifth lens element has a negative refractive power, and the object side surface of the fifth lens element is convex near the optical axis, and the image side surface is concave;

[0012] The sixth lens element has positive refractive power, and the object-side surface and the image-side surface of the sixth lens element are convex.

[0013] Furthermore, the fisheye lens satisfies: -5 <f1<-4,-3<f2<-2,4<f3<5,3<f4<4,-3<f5<-2,12<f6<3,

[0014] Among them, f1, f2, f3, f4, f5, and f6 are the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens, respectively.

[0015] Furthermore, the fisheye lens satisfies: 3<|f1 / f|<4, 2<|f2 / f|<3, 2.5<|f3 / f|<3.5, 2<|f4 / f|<3, 1<|f5 / f|<2, 1.5<|f6 / f|<2.5,

[0016] Wherein, f is the overall focal length of the lens, and f1, f2, f3, f4, f5, and f6 are the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens, respectively.

[0017] Furthermore, the fisheye lens satisfies: 3 <f 456 / f<5, where f 456 is the combined focal length of the fourth lens, the fifth lens, and the sixth lens, and f is the overall focal length of the lens.

[0018] Furthermore, the fisheye lens meets the following requirements: 1.7 <nd1<1.9,45<vd1<60,1.5<nd2<1.7,50<vd2<60,1.7<nd3<2,19<vd3<30,1.5<nd4<1.7,50<vd4<70,1.6<nd5<1.7,18<vd5<25,1.5<nd6<1.7,50<vd6<60,

[0019] Among them, nd1, nd2, nd3, nd4, nd5, and nd6 are the refractive indices of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens respectively, and vd1, vd2, vd3, vd4, vd5, and vd6 are the chromatic aberration coefficients of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens respectively.

[0020] Furthermore, the fisheye lens satisfies: ImgH / AAG<1, wherein ImgH is the image height on the imaging plane of the lens, and AAG is the sum of the air gaps between the first lens to the sixth lens.

[0021] Furthermore, the fisheye lens satisfies: ALT / AAG>2.0, wherein ALT is the sum of center thicknesses of the first lens to the sixth lens, and AAG is the sum of air gaps between the first lens to the sixth lens.

[0022] Furthermore, the first lens and the third lens are both glass spherical lenses, and the second lens, the fourth lens, the fifth lens, and the sixth lens are all plastic aspherical lenses.

[0023] Furthermore, it also includes an aperture, which is located on the image side surface of the third lens.

[0024] Furthermore, the total optical length TTL of the fisheye lens satisfies: TTL<15 mm.

[0025] After adopting the above technical solution, the present invention has the following advantages:

[0026] The low-distortion fisheye lens of this invention adopts a glass-plastic hybrid design, with an optical TTL of less than 15mm. The lens is compact and easy to install and use. The F-Theta distortion of the lens is controlled within |-5%|, with perfect distortion control. The edge deformation of the captured image is small, which is conducive to post-processing. The lens has a large imaging target area, suitable for 1 / 2.7" chips, with better photosensitivity and low imaging signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a light path diagram of Example 1 of the present invention;

[0028] Figure 2 This is an MTF curve of the lens in Example 1 of the present invention under visible light 435nm-650nm;

[0029] Figure 3 This is a defocus curve diagram of the lens of Example 1 of the present invention under visible light 435nm-650nm;

[0030] Figure 4 This is a graph showing the lateral chromatic aberration of the lens of Example 1 of the present invention under visible light of 435nm-650nm;

[0031] Figure 5 This is a graph showing the longitudinal chromatic aberration of the lens of Example 1 of the present invention under visible light of 435nm-650nm;

[0032] Figure 6 This is a diagram of field curvature and distortion of the lens in Example 1 of the present invention under visible light of 435nm-650nm;

[0033] Figure 7 This is a relative illumination diagram of the lens of Example 1 of the present invention under visible light 435nm-650nm;

[0034] Figure 8 This is a light path diagram of Example 2 of the present invention;

[0035] Figure 9 This is an MTF curve of the lens in Example 2 of the present invention under visible light 435nm-650nm;

[0036] Figure 10 This is a defocus curve diagram of the lens of Example 2 of the present invention under visible light 435nm-650nm;

[0037] Figure 11 This is a graph showing the lateral chromatic aberration of the lens of Example 2 of the present invention under visible light of 435nm-650nm;

[0038] Figure 12 This is a graph showing the longitudinal chromatic aberration of the lens of Example 2 of the present invention under visible light of 435nm-650nm;

[0039] Figure 13 This is a diagram of field curvature and distortion of the lens in Example 2 of the present invention under visible light 435nm-650nm;

[0040] Figure 14 This is a relative illumination diagram of the lens of Example 2 of the present invention under visible light 435nm-650nm;

[0041] Figure 15 This is a light path diagram of Example 3 of the present invention;

[0042] Figure 16 This is an MTF curve of the lens of Example 3 of the present invention under visible light 435nm-650nm;

[0043] Figure 17 This is a defocus curve diagram of the lens of Example 3 of the present invention under visible light 435nm-650nm;

[0044] Figure 18 This is a graph showing the lateral chromatic aberration of the lens of Example 3 of the present invention under visible light of 435nm-650nm;

[0045] Figure 19 This is a graph showing the longitudinal chromatic aberration of the lens of Example 3 of the present invention under visible light of 435nm-650nm;

[0046] Figure 20 This is a diagram of field curvature and distortion of the lens of Example 3 of the present invention under visible light 435nm-650nm;

[0047] Figure 21 This is a relative illumination diagram of the lens of Example 3 of the present invention under visible light 435nm-650nm;

[0048] Figure 22This is a light path diagram of Example 4 of the present invention;

[0049] Figure 23 This is an MTF curve of the lens of Example 4 of the present invention under visible light 435nm-650nm;

[0050] Figure 24 This is a defocus curve diagram of the lens of Example 4 of the present invention under visible light 435nm-650nm;

[0051] Figure 25 This is a graph showing the lateral chromatic aberration of the lens of Example 4 of the present invention under visible light of 435nm-650nm;

[0052] Figure 26 This is a graph showing the longitudinal chromatic aberration of the lens of Example 4 of the present invention under visible light ranging from 435nm to 650nm;

[0053] Figure 27 This is a diagram of field curvature and distortion of the lens of Example 4 of the present invention under visible light 435nm-650nm;

[0054] Figure 28 This is a relative illumination diagram of the lens of Example 4 of the present invention under visible light 435nm-650nm;

[0055] Figure 29 This is a light path diagram of Example 5 of the present invention;

[0056] Figure 30 This is an MTF curve of the lens of Example 5 of the present invention under visible light 435nm-650nm;

[0057] Figure 31 This is a defocus curve diagram of the lens of Example 5 of the present invention under visible light 435nm-650nm;

[0058] Figure 32 This is a graph showing the lateral chromatic aberration of the lens of Example 5 of the present invention under visible light of 435nm-650nm;

[0059] Figure 33 This is a graph showing the longitudinal chromatic aberration of the lens of Example 5 of the present invention under visible light ranging from 435nm to 650nm;

[0060] Figure 34 This is a diagram of field curvature and distortion of the lens of Example 5 of the present invention under visible light 435nm-650nm;

[0061] Figure 35 This is a relative illumination diagram of the lens of Example 5 of the present invention under visible light 435nm-650nm.

[0062] Description of reference numerals:

[0063] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Protective glass. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0065] Here, "a lens having a positive (or negative) refractive power" means that the lens's paraxial refractive power, calculated using Gaussian optics theory, is positive (or negative). The "object-side (or image-side) of a lens" is defined as the specific area of the lens surface through which the imaging light passes. The concavity or convexity of a lens's surface can be determined using the same method commonly used by those skilled in the art: the sign of the radius of curvature (abbreviated as R value). R values are commonly used in optical design software such as Zemax or CodeV. R values are also commonly found in lens data sheets within optical design software. For the object-side surface, a positive R value indicates a convex surface; a negative R value indicates a concave surface. Conversely, for the image-side surface, a positive R value indicates a concave surface; a negative R value indicates a convex surface.

[0066] The present invention discloses a low-distortion fisheye lens, comprising a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a sixth lens 6, which are arranged in sequence along an optical axis from the object side to the image side. The first lens 1 to the sixth lens 6 each include an object-side surface facing the object side and through which imaging light passes, and an image-side surface facing the image side and through which imaging light passes.

[0067] The first lens 1 has a negative refractive power, and the object side surface of the first lens 1 is convex, and the image side surface is concave;

[0068] The second lens element 2 has a negative refractive power, and the object side surface of the second lens element 2 is convex, and the image side surface is concave;

[0069] The third lens element 3 has positive refractive power, and the object-side surface and image-side surface of the third lens element 3 are convex;

[0070] The fourth lens element 4 has positive refractive power, and the object-side surface and image-side surface of the fourth lens element 4 are convex.

[0071] The fifth lens element 5 has a negative refractive power, and the object side surface of the fifth lens element 5 is convex near the optical axis, and the image side surface is concave;

[0072] The sixth lens 6 has a positive refractive power, and the object side surface of the sixth lens 6 is convex, and the image side surface is convex;

[0073] The first lens 1 and the third lens 3 are both glass spherical lenses, and the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all plastic aspherical lenses. In addition, it further includes an aperture, and the aperture is located on the image side surface of the third lens 3.

[0074] This fish-eye lens satisfies: 1.7 < nd1 < 1.9, 45 < vd1 < 60, 1.5 < nd2 < 1.7, 50 < vd2 < 60, 1.7 < nd3 < 2, 19 < vd3 < 30, 1.5 < nd4 < 1.7, 50 < vd4 < 70, 1.6 < nd5 < 1.7, 18 < vd5 < 25, 1.5 < nd6 < 1.7, 50 < vd6 < 60, where nd1, nd2, nd3, nd4, nd5, and nd6 are the refractive indices of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 respectively, and vd1, vd2, vd3, vd4, vd5, and vd6 are the dispersion coefficients of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 respectively.

[0075] A glass-plastic hybrid design is adopted. Among them, a four-piece plastic aspherical design is adopted, which is more conducive to correcting secondary spectrum and higher-order aberrations; at the same time, high-refractive-index materials are selected for the glass lenses, which can better optimize the optical structure and facilitate the lens structure design, and reduce the lens cost.

[0076] This fish-eye lens satisfies: -5 < f1 < -4, -3 < f2 < -2, 4 < f3 < 5, 3 < f4 < 4, -3 < f5 < -2, 12 < f6 < 3, where f1, f2, f3, f4, f5, and f6 are the focal length values of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 respectively.

[0077] This fish-eye lens satisfies: 3 < |f1 / f| < 4, 2 < |f2 / f| < 3, 2.5 < |f3 / f| < 3.5, 2 < |f4 / f| < 3, 1 < |f5 / f| < 2, 1.5 < |f6 / f| < 2.5, where f is the overall focal length of the lens, and f1, f2, f3, f4, f5, and f6 are the focal lengths of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 respectively.

[0078] This fish-eye lens satisfies: 3 < f 456 / f < 5, where f 456is the combined focal length of the fourth lens 4, the fifth lens 5, and the sixth lens 6, and f is the overall focal length of the lens. The optical power of each lens is rationally allocated to ensure system performance.

[0079] The fisheye lens satisfies: ImgH / AAG<1, where ImgH is the image height on the imaging surface of the lens, and AAG is the sum of the air gaps between the first lens 1 to the sixth lens 6 .

[0080] The fisheye lens satisfies: ALT / AAG>2.0, wherein ALT is the sum of the center thicknesses of the first lens 1 to the sixth lens 6 , and AAG is the sum of the air gaps between the first lens 1 to the sixth lens 6 .

[0081] The total optical length TTL of this fisheye lens meets the following requirements: TTL<15mm, and the overall size of the lens is small, making it extremely convenient to install and use.

[0082] This fisheye lens has high illumination, with an edge relative illumination higher than 55%, and has good imaging quality. It has a large field of view (FOV = 200°), which increases the overall field of view of the lens and improves its practicality. The edge MTF of the lens at 125lp / mm is higher than 40%, with high resolution and good imaging quality.

[0083] The low-distortion fisheye lens of the present invention will be described in detail below with reference to specific embodiments.

[0084] Example 1

[0085] Reference Figure 1 As shown, the present invention discloses a low-distortion fisheye lens, comprising a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a sixth lens 6, which are arranged in sequence along an optical axis from the object side to the image side. The first lens 1 to the sixth lens 6 each include an object-side surface facing the object side and allowing imaging light to pass through, and an image-side surface facing the image side and allowing imaging light to pass through.

[0086] The first lens 1 has a negative refractive power, and the object side surface of the first lens 1 is convex, and the image side surface is concave;

[0087] The second lens element 2 has a negative refractive power, and the object side surface of the second lens element 2 is convex, and the image side surface is concave;

[0088] The third lens element 3 has positive refractive power, and the object-side surface and image-side surface of the third lens element 3 are convex;

[0089] The fourth lens element 4 has positive refractive power, and the object-side surface and image-side surface of the fourth lens element 4 are convex.

[0090] The fifth lens element 5 has a negative refractive power, and the object side surface of the fifth lens element 5 is convex near the optical axis, and the image side surface is concave;

[0091] The sixth lens element 6 has positive refractive power, and the object-side surface and the image-side surface of the sixth lens element 6 are convex.

[0092] The detailed optical data of this specific embodiment are shown in Table 1-1.

[0093] Table 1-1 Detailed optical data of Example 1

[0094]

[0095] In this embodiment, the first lens 1 and the third lens 3 are both glass spherical lenses, and the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all plastic aspherical lenses. Both surfaces of the plastic aspherical lenses are aspherical. The equation for the surface curve of the aspherical lens is expressed as follows:

[0096]

[0097] in,

[0098] z: Depth of the aspheric surface (the vertical distance between the point y away from the optical axis on the aspheric surface and the tangent plane tangent to the vertex on the optical axis of the aspheric surface);

[0099] c: the vertex curvature of the aspheric surface;

[0100] K: Conic Constant;

[0101] radial distance;

[0102] r n : normalization radius (NRADIUS);

[0103] u:r / r n ;

[0104] a m : mth order Q con Coefficient (is the m th Q con coefficient);

[0105] Q m con : mth order Q con Polynomial th Q conpolynomial).

[0106] The aspheric surface data in this embodiment are shown in Table 1-2.

[0107] Table 1-2 Aspheric surface data of Example 1

[0108]

[0109] In this embodiment, please refer to the MTF curve of the lens under 435nm-650nm visible light. Figure 2 As can be seen from the figure, when the spatial frequency of this lens reaches 125lp / mm, the MTF value is greater than 0.5, the lens has high resolution and excellent imaging quality. For the defocus curve of the lens under 435nm-650nm visible light, please refer to Figure 3 As can be seen from the figure, the defocus curves of each field of view of this lens under visible light are relatively concentrated, and the defocus amount is small. For the lateral chromatic aberration curve of the lens under 435nm-650nm visible light, please refer to Figure 4 ,As can be seen from the figure, the lateral chromatic aberration is less than 12um, the chromatic aberration is small, and the image color reproduction is high.

[0110] Please refer to the longitudinal chromatic aberration curve of the lens under 435nm-650nm visible light. Figure 5 As can be seen from the figure, the axial chromatic aberration is less than ±0.02mm, the color reproduction is good, the color difference is small, and the blue-purple fringing phenomenon is not obvious. Please refer to the field curvature and distortion diagram of the lens under 435nm-650nm visible light. Figure 6 As can be seen from the figure, the field curvature of each wavelength is basically the same, the chromatic aberration is small, and the optical distortion of the system is <|-5%|, which is small, controlling the wide-angle distortion and improving the image quality. There is no need for post-processing of the image algorithm to correct the distortion, which is convenient for application. Please refer to the relative illumination diagram of the lens under 435nm-650nm visible light. Figure 7 ,As can be seen from the figure, the relative illumination is > 55%, and the ,imaging is uniform and of good quality.

[0111] Example 2

[0112] like Figure 8 As shown, the present embodiment is different from the embodiment 1 mainly in optical parameters such as the curvature radius of each lens surface and the lens thickness.

[0113] The detailed optical data of this specific embodiment are shown in Table 2-1.

[0114] Table 2-1 Detailed optical data of Example 2

[0115]

[0116]

[0117] In this embodiment, the first lens 1 and the third lens 3 are both glass spherical lenses, while the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all plastic aspherical lenses. Both surfaces of the plastic aspherical lenses are aspherical. The aspherical surface data for this embodiment is shown in Table 2-2.

[0118] Table 2-2 Aspheric surface data of Example 2

[0119]

[0120] In this embodiment, please refer to the MTF curve of the lens under 435nm-650nm visible light. Figure 9 As can be seen from the figure, when the spatial frequency of this lens reaches 125lp / mm, the MTF value is greater than 0.4, the lens has high resolution and excellent imaging quality. For the defocus curve of the lens under 435nm-650nm visible light, please refer to Figure 10 As can be seen from the figure, the defocus curves of each field of view of this lens under visible light are relatively concentrated, and the defocus amount is small. For the lateral chromatic aberration curve of the lens under 435nm-650nm visible light, please refer to Figure 11 ,As can be seen from the figure, the lateral chromatic aberration is less than 12um, the chromatic aberration is small, and the image color reproduction is high.

[0121] Please refer to the longitudinal chromatic aberration curve of the lens under 435nm-650nm visible light. Figure 12 As can be seen from the figure, the axial chromatic aberration is less than ±0.03mm, the color reproduction is good, the color difference is small, and the blue-purple fringing phenomenon is not obvious. Please refer to the field curvature and distortion diagram of the lens under 435nm-650nm visible light. Figure 13 As can be seen from the figure, the field curvature of each wavelength is basically the same, the chromatic aberration is small, and the optical distortion of the system is <|-5%|, which is small, controlling the wide-angle distortion and improving the image quality. There is no need for post-processing of the image algorithm to correct the distortion, which is convenient for application. Please refer to the relative illumination diagram of the lens under 435nm-650nm visible light. Figure 14 ,As can be seen from the figure, the relative illumination is > 55%, and the ,imaging is uniform and of good quality.

[0122] Example 3

[0123] like Figure 15 As shown, the present embodiment is different from the embodiment 1 mainly in optical parameters such as the curvature radius of each lens surface and the lens thickness.

[0124] The detailed optical data of this specific embodiment are shown in Table 3-1.

[0125] Table 3-1 Detailed optical data of Example 3

[0126]

[0127] In this embodiment, the first lens 1 and the third lens 3 are both glass spherical lenses, while the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all plastic aspherical lenses. Both surfaces of the plastic aspherical lenses are aspherical. The aspherical surface data for this embodiment is shown in Table 3-2.

[0128] Table 3-2 Aspheric surface data of Example 3

[0129]

[0130] In this embodiment, please refer to the MTF curve of the lens under 435nm-650nm visible light. Figure 16 As can be seen from the figure, when the spatial frequency of this lens reaches 125lp / mm, the MTF value is greater than 0.4, the lens has high resolution and excellent imaging quality. For the defocus curve of the lens under 435nm-650nm visible light, please refer to Figure 17 As can be seen from the figure, the defocus curves of each field of view of this lens under visible light are relatively concentrated, and the defocus amount is small. For the lateral chromatic aberration curve of the lens under 435nm-650nm visible light, please refer to Figure 18 ,As can be seen from the figure, the lateral chromatic aberration is less than 8um, the chromatic aberration is small, and the image color reproduction is high.

[0131] Please refer to the longitudinal chromatic aberration curve of the lens under 435nm-650nm visible light. Figure 19 As can be seen from the figure, the axial chromatic aberration is less than ±0.02mm, the color reproduction is good, the color difference is small, and the blue-purple fringing phenomenon is not obvious. Please refer to the field curvature and distortion diagram of the lens under 435nm-650nm visible light. Figure 20 As can be seen from the figure, the field curvature of each wavelength is basically the same, the chromatic aberration is small, and the optical distortion of the system is <|-2%|, which is small, controlling the wide-angle distortion and improving the image quality. There is no need for post-processing of image algorithms to correct the distortion, which is convenient for application. Please refer to the relative illumination diagram of the lens under 435nm-650nm visible light. Figure 21 ,As can be seen from the figure, the relative illumination is > 55%, and the ,imaging is uniform and of good quality.

[0132] Example 4

[0133] like Figure 22 As shown, the present embodiment is different from the embodiment 1 mainly in optical parameters such as the curvature radius of each lens surface and the lens thickness.

[0134] The detailed optical data of this specific embodiment are shown in Table 4-1.

[0135] Table 4-1 Detailed optical data of Example 4

[0136]

[0137] In this embodiment, the first lens 1 and the third lens 3 are both glass spherical lenses, while the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all plastic aspherical lenses. Both surfaces of the plastic aspherical lenses are aspherical. The aspherical surface data for this embodiment is shown in Table 4-2.

[0138] Table 4-2 Aspheric surface data of Example 4

[0139]

[0140]

[0141] In this embodiment, please refer to the MTF curve of the lens under 435nm-650nm visible light. Figure 23 As can be seen from the figure, when the spatial frequency of this lens reaches 125lp / mm, the MTF value is greater than 0.4, the lens has high resolution and excellent imaging quality. For the defocus curve of the lens under 435nm-650nm visible light, please refer to Figure 24 As can be seen from the figure, the defocus curves of each field of view of this lens under visible light are relatively concentrated, and the defocus amount is small. For the lateral chromatic aberration curve of the lens under 435nm-650nm visible light, please refer to Figure 25 ,As can be seen from the figure, the lateral chromatic aberration is less than 8um, the chromatic aberration is small, and the image color reproduction is high.

[0142] Please refer to the longitudinal chromatic aberration curve of the lens under 435nm-650nm visible light. Figure 26 As can be seen from the figure, the axial chromatic aberration is less than ±0.015mm, the color reproduction is good, the color difference is small, and the blue-purple fringing phenomenon is not obvious. Please refer to the field curvature and distortion diagram of the lens under 435nm-650nm visible light. Figure 27 As can be seen from the figure, the field curvature of each wavelength is basically the same, the chromatic aberration is small, and the optical distortion of the system is <|-2.5%|, which is small, controls wide-angle distortion, improves image quality, and does not require post-processing image algorithm to correct distortion, making it easy to use. Please refer to the relative illumination diagram of the lens under 435nm-650nm visible light. Figure 28 ,As can be seen from the figure, the relative illumination is > 55%, and the ,imaging is uniform and of good quality.

[0143] Example 5

[0144] like Figure 29 As shown, the present embodiment is different from the embodiment 1 mainly in optical parameters such as the curvature radius of each lens surface and the lens thickness.

[0145] The detailed optical data of this specific embodiment are shown in Table 5-1.

[0146] Table 5-1 Detailed optical data of Example 5

[0147]

[0148] In this embodiment, the first lens 1 and the third lens 3 are both glass spherical lenses, while the second lens 2, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all plastic aspherical lenses. Both surfaces of the plastic aspherical lenses are aspherical. The aspherical surface data for this embodiment is shown in Table 5-2.

[0149] Table 5-2 Aspheric surface data of Example 5

[0150]

[0151] In this embodiment, please refer to the MTF curve of the lens under 435nm-650nm visible light. Figure 30 As can be seen from the figure, when the spatial frequency of this lens reaches 125lp / mm, the MTF value is greater than 0.4, the lens has high resolution and excellent imaging quality. For the defocus curve of the lens under 435nm-650nm visible light, please refer to Figure 31 As can be seen from the figure, the defocus curves of each field of view of this lens under visible light are relatively concentrated, and the defocus amount is small. For the lateral chromatic aberration curve of the lens under 435nm-650nm visible light, please refer to Figure 32 ,As can be seen from the figure, the lateral chromatic aberration is less than 7um, the chromatic aberration is small, and the image color reproduction is high.

[0152] Please refer to the longitudinal chromatic aberration curve of the lens under 435nm-650nm visible light. Figure 33 As can be seen from the figure, the axial chromatic aberration is less than ±0.03mm, the color reproduction is good, the color difference is small, and the blue-purple fringing phenomenon is not obvious. Please refer to the field curvature and distortion diagram of the lens under 435nm-650nm visible light. Figure 34 As can be seen from the figure, the field curvature of each wavelength is basically the same, the chromatic aberration is small, and the optical distortion of the system is <|-3.5%|, which is small, controlling the wide-angle distortion and improving the image quality. There is no need for post-processing of image algorithms to correct the distortion, which is convenient for application. Please refer to the relative illumination diagram of the lens under 435nm-650nm visible light. Figure 35 ,As can be seen from the figure, the relative illumination is > 55%, and the ,imaging is uniform and of good quality.

[0153] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A low-distortion fisheye lens, characterized by: It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in sequence along an optical axis from the object side to the image side. Each of the first lens to the sixth lens includes an object side facing the object side through which imaging light passes and an image side facing the image side through which imaging light passes; The first lens has a negative refractive power, and the object side of the first lens is convex, and the image side is concave; The second lens has a negative refractive power, and the object side of the second lens is convex, and the image side is concave; The third lens has a positive refractive power, and the object side of the third lens is convex, and the image side is convex; The fourth lens has a positive refractive power, and the object side of the fourth lens is convex, and the image side is convex; The fifth lens has a negative refractive power, and the object side of the fifth lens is convex near the optical axis, and the image side is concave; The sixth lens has a positive refractive power, and the object side of the sixth lens is convex, and the image side is convex; This fish-eye lens satisfies: -5mm < f1 < -4mm, -3mm < f2 < -2mm, 4mm < f3 < 5mm, 3mm < f4 < 4mm, -3mm < f5 < -2mm, 2.396mm ≤ f6 < 3mm. Wherein, f1, f2, f3, f4, f5, f6 are the focal length values of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens respectively.

2. The low-distortion fisheye lens according to claim 1, wherein: This fish-eye lens satisfies: 3 < |f1 / f| < 4, 2 < |f2 / f| < 3, 2.5 < |f3 / f| < 3.5, 2 < |f4 / f| < 3, 1 < |f5 / f| < 2, 1.5 < |f6 / f| < 2.5, Wherein, f is the overall focal length of the lens, and f1, f2, f3, f4, f5, f6 are the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens respectively.

3. The low-distortion fisheye lens according to claim 1, wherein: The fisheye lens meets: 3 <f 456 / f<5, where f 456 is the combined focal length of the fourth lens, the fifth lens, and the sixth lens, and f is the overall focal length of the lens.

4. The low-distortion fisheye lens according to claim 1, wherein: This fish-eye lens satisfies: 1.7 < nd1 < 1.9, 45 < vd1 < 60, 1.5 < nd2 < 1.7, 50 < vd2 < 60, 1.7 < nd3 < 2, 19 < vd3 < 30, 1.5 < nd4 < 1.7, 50 < vd4 < 70, 1.6 < nd5 < 1.7, 18 < vd5 < 25, 1.5 < nd6 < 1.7, 50 < vd6 < 60, Wherein, nd1, nd2, nd3, nd4, nd5, nd6 are the refractive indices of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens respectively, and vd1, vd2, vd3, vd4, vd5, vd6 are the dispersion coefficients of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens respectively.

5. The low-distortion fisheye lens according to claim 1, wherein: This fish-eye lens satisfies: ImgH / AAG < 1. Wherein, ImgH is the image height on the imaging surface of the lens, and AAG is the sum of the air gaps between the first lens and the sixth lens.

6. The low-distortion fisheye lens according to claim 1 or 5, characterized in that: This fish-eye lens satisfies: ALT / AAG > 2.

0. Wherein, ALT is the sum of the central thicknesses of the first lens to the sixth lens, and AAG is the sum of the air gaps between the first lens and the sixth lens.

7. The low-distortion fisheye lens according to claim 1, wherein: The first lens and the third lens are both glass spherical lenses, and the second lens, the fourth lens, the fifth lens, and the sixth lens are all plastic aspherical lenses.

8. The low-distortion fisheye lens according to claim 1 or 7, wherein: The optical system further includes a stop located on the image-side surface of the third lens.

9. The low-distortion fisheye lens according to claim 1, wherein: The total optical length TTL of the fisheye lens meets the following requirements: TTL<15mm.

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