A fisheye lens

Abstract

The application provides a fisheye lens, which comprises first to eighth lenses and a protection glass in sequence along an optical axis from an object side to an image side, and a diaphragm is located between the fourth and fifth lenses; the first to third lenses all have negative refractive power, the object side surface is a convex surface, and the image side surface is a concave surface; the fourth and fifth lenses have positive refractive power and are biconvex; the sixth lens has negative refractive power, the object side surface is a concave surface, and the image side surface is a convex surface; the seventh lens has positive refractive power and is biconvex; the eighth lens has negative refractive power and is biconcave; all the lenses are glass spherical lenses; through specific refractive power arrangement, surface configuration, refractive index and Abbe number range limitation, a miniaturized structure with an optical total length less than 21 mm and an effective diameter of each lens less than phi 12 mm is realized, the MTF is greater than 0.6 in a 0.8 field of view at a spatial frequency of 83 lp / mm, the total field of view is greater than 0.45, the target surface height is greater than 4.6 mm to match a 1 / 2.4 inch sensor, the F-Theta distortion is less than 1%, and the relative luminance at the maximum field of view is greater than 55%.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and in particular to a fisheye lens. Background Technology

[0002] Fisheye lenses, as a type of ultra-wide-angle lens, typically have a field of view of over 180°, enabling imaging of ultra-wide scenes. They have a wide range of applications in fields such as security monitoring, vehicle imaging, panoramic shooting, virtual reality, and machine vision.

[0003] With the continuous expansion of application scenarios and the ongoing upgrade of image sensor chip technology, the market's performance requirements for fisheye lenses are increasing: on the one hand, image sensors with a larger target area are needed to meet the needs of high-resolution imaging; on the other hand, in low-light environments, the lens needs to have good relative illumination characteristics to ensure the brightness and uniformity of the image; at the same time, if the inherent barrel distortion of fisheye lenses is not effectively corrected, it will lead to severe distortion at the edges of the image, affecting the visual experience and the accuracy of subsequent image processing; in addition, in order to adapt to portable devices and space-constrained application scenarios, the miniaturization design of the lens has also become an important consideration.

[0004] In current technology, fisheye lens design faces numerous technical challenges. Traditional fisheye lens designs often employ a smaller number of lenses, resulting in simpler structures and lower costs, but they struggle to achieve an ideal balance between image quality and a large field of view. Some designs utilize five- or six-element structures, which, while achieving the basic functions of fisheye imaging, suffer from significant deficiencies in resolution, distortion control, and relative illumination. While some designs utilize a larger number of lenses to improve image quality, this often leads to an increase in overall lens length and size, making it difficult to meet miniaturization requirements. Furthermore, existing fisheye lens designs still face significant bottlenecks in simultaneously achieving large target area coverage, low F-Theta distortion (typically required to be controlled within 1%), high relative illumination (greater than 55%), and good modulation transfer function (MTF) characteristics (maintaining a high value at higher spatial frequencies). Summary of the Invention

[0005] This invention provides a fisheye lens, which can effectively solve the above-mentioned problems.

[0006] This invention is implemented as follows: A fisheye lens, comprising, from the object side to the image side along the optical axis, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a protective glass, with an aperture stop disposed between the fourth lens and the fifth lens; wherein, The first lens has negative refractive power, its object side is convex, and its image side is concave. The second lens has negative dioptric power, an object-side surface thereof is a convex surface, and an image-side surface thereof is a concave surface; The third lens has negative dioptric power, an object-side surface thereof is a convex surface, and an image-side surface thereof is a concave surface; The fourth lens has positive dioptric power, an object-side surface thereof is a convex surface, and an image-side surface thereof is a convex surface; The fifth lens has positive dioptric power, an object-side surface thereof is a convex surface, and an image-side surface thereof is a convex surface; The sixth lens has negative dioptric power, an object-side surface thereof is a concave surface, and an image-side surface thereof is a convex surface; The seventh lens has positive dioptric power, an object-side surface thereof is a convex surface, and an image-side surface thereof is a convex surface; The eighth lens has negative dioptric power, an object-side surface thereof is a concave surface, and an image-side surface thereof is a concave surface.

[0007] As a further improvement, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are all glass spherical lenses.

[0008] As a further improvement, the refractive index of the first lens is set as nd1, and nd1>1.75.

[0009] As a further improvement, the refractive index of the first lens is set as nd1, and 1.7<nd1<1.9, the Abbe number thereof is set as vd1, and 35<vd1<50; the refractive index of the second lens is set as nd2, and 1.9<nd2<2.1, the Abbe number thereof is set as vd2, and 20<vd2<40; the refractive index of the third lens is set as nd3, and 1.7<nd3<1.9, the Abbe number thereof is set as vd3, and 40<vd3<60; the refractive index of the fourth lens is set as nd4, and 1.95<nd4<2.05, the Abbe number thereof is set as vd4, and 20<vd4<30; the refractive index of the fifth lens is set as nd5, and 1.5<nd5<1.6, the Abbe number thereof is set as vd5, and 60<vd5<80; the refractive index of the sixth lens is set as nd6, and 1.9<nd6<2.0, the Abbe number thereof is set as vd6, and 15<vd6<25; the refractive index of the seventh lens is set as nd7, and 1.5<nd7<1.6, the Abbe number thereof is set as vd7, and 60<vd7<80; the refractive index of the eighth lens is set as nd8, and 1.95<nd8<2.05, the Abbe number thereof is set as vd8, and 20<vd8<30.

[0010] As a further improvement, the Abbe number vd5 of the fifth lens and the Abbe number vd6 of the sixth lens satisfy: |vd5-vd6|>40; the Abbe number vd7 of the seventh lens and the Abbe number vd8 of the eighth lens satisfy: |vd7-vd8|>40.

[0011] As a further improvement, the total optical system length TTL of the lens and the focal length F of the optical system satisfy: 12 <TTL / F<16。

[0012] As a further improvement, the total optical system length TTL of the lens and the aperture number FNO satisfy: 10 <TTL / FNO<12。

[0013] As a further improvement, the total optical length (TTL) of the lens is less than 21 mm, and the effective aperture of the first to eighth lenses is less than φ12 mm.

[0014] As a further improvement, the lens has an MTF greater than 0.6 within a 0.8 field of view and greater than 0.45 across the entire field of view at a spatial frequency of 83 lp / mm; the lens has a target surface height greater than 4.6 mm; the lens has an F-Theta distortion of less than 1%; and the lens has a relative illumination greater than 55% at the maximum field of view.

[0015] As a further improvement, the lens can be matched with a 1 / 2.4-inch image sensor.

[0016] The beneficial effects of this invention are: 1) By setting the total optical length (TTL) of the fisheye lens to less than 21mm and the effective light transmission diameter of each lens to less than φ12mm, a highly compact lens size is achieved while obtaining ultra-wide field-of-view imaging, greatly expanding its application range in space-constrained devices.

[0017] 2) By setting the fisheye lens to a spatial frequency of 83 lp / mm, the MTF value within the 0.8 field of view is greater than 0.6, and the MTF value within the entire field of view is greater than 0.45, which can meet the requirements of high-resolution imaging. The image is clear and sharp, with outstanding detail reproduction capability, achieving excellent imaging quality.

[0018] 3) By setting the F-Theta distortion of the fisheye lens to less than 1%, it is far superior to the 50% to 100% barrel distortion level that is usually present in traditional fisheye lenses. This extremely low distortion characteristic ensures that the image will not be affected by geometric deformation, making it particularly suitable for applications such as measurement, recognition, and post-image stitching that are sensitive to distortion.

[0019] 4) By setting the relative illumination of the fisheye lens to be greater than 55% at the maximum field of view, the problem of severe edge glare in traditional fisheye lenses is effectively solved, ensuring uniform illumination across the entire field of view and good brightness consistency in the image.

[0020] 5) By setting the target surface height of the fisheye lens to be greater than 4.6mm, it can be matched with a 1 / 2.4-inch image sensor chip, meeting the imaging requirements of high-pixel, large-target-surface sensors.

[0021] 6) By setting all lenses of the fisheye lens to be glass spherical lenses, the processing difficulty and manufacturing cost of the lenses are reduced while ensuring excellent optical performance. At the same time, glass material has good temperature stability and chemical stability, making it suitable for harsh environments with a wide temperature range. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of a fisheye lens according to Embodiment 1 of the present invention.

[0024] Figure 2 This is the MTF curve of the fisheye lens of Embodiment 1 of the present invention under visible light conditions.

[0025] Figure 3 This is a rayfan curve diagram of the fisheye lens according to Embodiment 1 of the present invention.

[0026] Figure 4 This is a field curvature and distortion curve diagram of the fisheye lens according to Embodiment 1 of the present invention.

[0027] Figure 5 This is a relative illumination diagram of the fisheye lens according to Embodiment 1 of the present invention.

[0028] Figure 6 This is a schematic diagram of the structure of the fisheye lens according to Embodiment 2 of the present invention.

[0029] Figure 7 This is the MTF curve of the fisheye lens of Embodiment 2 of the present invention under visible light conditions.

[0030] Figure 8 This is a rayfan curve diagram of the fisheye lens according to Embodiment 2 of the present invention.

[0031] Figure 9This is a field curvature and distortion curve diagram of the fisheye lens according to Embodiment 2 of the present invention.

[0032] Figure 10 This is a relative illumination diagram of the fisheye lens according to Embodiment 2 of the present invention.

[0033] Figure 11 This is a schematic diagram of the structure of the fisheye lens according to Embodiment 3 of the present invention.

[0034] Figure 12 This is the MTF curve of the fisheye lens of Embodiment 3 of the present invention under visible light conditions.

[0035] Figure 13 This is a rayfan curve diagram of the fisheye lens according to Embodiment 3 of the present invention.

[0036] Figure 14 This is a field curvature and distortion curve diagram of the fisheye lens according to Embodiment 3 of the present invention.

[0037] Figure 15 This is a relative illumination diagram of the fisheye lens according to Embodiment 3 of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] Reference Figures 1-15As shown, a fisheye lens comprises, in order from the object side to the image side along the optical axis direction: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a stop STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a protective glass CG.

[0041] Specifically, three first lens L1, second lens L2 and third lens L3 with negative refractive power are arranged at the front end of the lens. These three lenses form a front negative lens group, whose main function is to compress incident light rays with a large field of view, so that the light rays gradually converge toward the optical axis direction. It can effectively receive light incident from an ultra-wide angle, prevent the light from excessive divergence; and can greatly reduce the required aperture size of the rear lens group. The front negative lens group enables the lens to achieve both "large field of view" and "miniaturization".

[0042] Specifically, two fourth lens L4 and fifth lens L5 with positive refractive power are arranged in the middle section of the lens. These two lenses form a rear positive lens group, which is responsible for focusing the compressed converging light beam on the imaging surface. By reasonably distributing the refractive power ratio of the fourth lens L4 and the fifth lens L5, various aberrations of the system such as spherical aberration, coma, field curvature and astigmatism can be effectively controlled.

[0043] Specifically, the stop STO is arranged between the fourth lens L4 and the fifth lens L5. By adjusting the lens spacing before and after the stop STO, the astigmatism of the system can be significantly improved; meanwhile, the lens surface profile design near the stop STO can better compensate coma and distortion; in addition, arranging the stop between the positive refractive power group and the negative refractive power group is also conducive to controlling lateral chromatic aberration.

[0044] Further, the first lens has negative diopter, the object side surface thereof is a convex surface, and the image side surface thereof is a concave surface; the refractive index thereof is set as nd1, and nd1>1.75. By selecting a high refractive index material, the curvature of the surface of the first lens can be effectively reduced, thereby suppressing the generation of high-order aberrations and improving the overall performance of the system. Optimally, 1.7 < nd1 < 1.9, and the Abbe number thereof is set as vd1, and 35 < vd1 < 50.

[0045] The second lens has negative diopter, the object side surface thereof is a convex surface, and the image side surface thereof is a concave surface; the refractive index thereof is set as nd2, and 1.9 < nd2 < 2.1, the Abbe number thereof is set as vd2, and 20 < vd2 < 40.

[0046] The third lens has negative diopter, the object side surface thereof is a convex surface, and the image side surface thereof is a concave surface; the refractive index thereof is set as nd3, and 1.7 < nd3 < 1.9, the Abbe number thereof is set as vd3, and 40 < vd3 < 60.

[0047] The fourth lens has positive refractive power, an object-side surface that is convex, and an image-side surface that is convex; the refractive index thereof is set as nd4, 1.95 < nd4 < 2.05, and the Abbe number thereof is set as vd4, 20 < vd4 < 30.

[0048] The fifth lens has positive refractive power, an object-side surface that is convex, and an image-side surface that is convex; the refractive index thereof is set as nd5, 1.5 < nd5 < 1.6, and the Abbe number thereof is set as vd5, 60 < vd5 < 80.

[0049] The sixth lens has negative refractive power, an object-side surface that is concave, and an image-side surface that is convex; the refractive index thereof is set as nd6, 1.9 < nd6 < 2.0, and the Abbe number thereof is set as vd6, 15 < vd6 < 25.

[0050] The seventh lens has positive refractive power, an object-side surface that is convex, and an image-side surface that is convex; the refractive index thereof is set as nd7, 1.5 < nd7 < 1.6, and the Abbe number thereof is set as vd7, 60 < vd7 < 80.

[0051] The eighth lens has negative refractive power, an object-side surface that is concave, and an image-side surface that is concave; the refractive index thereof is set as nd8, 1.95 < nd8 < 2.05, and the Abbe number thereof is set as vd8, 20 < vd8 < 30.

[0052] Further, the Abbe number vd5 of the fifth lens and the Abbe number vd6 of the sixth lens satisfy: |vd5-vd6|>40; the Abbe number vd7 of the seventh lens and the Abbe number vd8 of the eighth lens satisfy: |vd7-vd8|>40. By matching lenses with a high Abbe number and a low Abbe number (a cemented pairing mode can be adopted), the chromatic aberration of the system can be effectively eliminated, so that imaging is clearer.

[0053] Specifically, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are all arranged as glass spherical lenses, and all are glass spherical lenses. The glass material has excellent thermal stability, chemical stability and optical uniformity, enabling the lens to work stably in a wide temperature range. Compared with aspheric lenses, spherical lenses have the advantages of low processing cost, convenient detection and good batch consistency.

[0054] Example 1: Table 1: Optical parameter table of Example 1:

[0055] In this embodiment, the first lens L1 uses H-ZLAF55C glass (nd1=1.83, vd1=42.71) with a focal length of -6.366mm. The object side convexes, while the image side is concave towards the optical axis. The second lens L2 uses H-ZLAF89L glass (nd2=1.95, vd2=32.31) with a focal length of -8.259mm. The third lens L3 uses H-ZLA69A glass (nd3=1.82, vd3=46.56) with a focal length of -6.657mm. The power distribution of the first three negative lenses is reasonable, ensuring smooth reception of light rays across a wide field of view.

[0056] The fourth lens, L4, uses H-ZLAF90 glass (nd4=2.00, vd4=25.43), with a focal length of 4.806mm. It is a biconvex lens and is used for the main light-convex function. The fifth lens, L5, uses H-ZPK5 glass (nd5=1.59, vd5=68.34, with a focal length of -9.185mm). L5 is a biconvex lens used to further converge light. The sixth lens, L6, uses H-ZF88 glass (nd6=1.95, vd6=17.94), with a focal length of 7.874mm. It has a concave object side and a convex image side, forming a meniscus shape. The seventh lens, L7, uses H-ZPK5 glass (nd7=1.59, vd7=68.34), with a focal length of 78.352mm, and is also biconvex. The eighth lens, L8, uses H-ZLAF90 glass (nd8=2.00, vd8=25.43), has a focal length of -6.883mm, and is biconcave in shape.

[0057] Regarding aberration correction, in this embodiment, the difference between vd5 (68.34) and vd6 (17.94) is |vd5-vd6|=50.4>40, and the difference between vd7 (68.34) and vd8 (25.43) is |vd7-vd8|=42.91>40, which satisfies the chromatic aberration elimination condition of alternating high Abbe number and low Abbe number materials.

[0058] like Figures 2 to 5 As shown, at a spatial frequency of 83 lp / mm, the MTF within a 0.8 field of view is >0.65, and the MTF across the entire field of view is >0.45, indicating high image clarity. The Rayfan curve shows that light at each wavelength converges and is well controlled in terms of aberrations. The F-Theta distortion is less than 1%, and the geometric deformation is minimal. The relative illumination at the maximum field of view is greater than 0.55, with good uniformity of edge illumination and no obvious vignetting at the edges.

[0059] Example 2: Table 2. Optical parameters of Example 2:

[0060] In this embodiment, the first lens L1 uses H-ZLAF68N glass (nd1=1.88, vd1=39.22) with a focal length of -6.055mm. The second lens L2 uses H-ZLAF92 glass (nd2=2.00, vd2=28.32) with a focal length of -10.222mm. The third lens L3 uses H-ZLAF69A glass (nd3=1.82, vd3=46.56) with a focal length of -5.993mm. The fourth lens L4 uses H-ZLAF90 glass (nd4=2.00, vd4=25.43) with a focal length of 4.979mm. The fifth lens L5 uses H-ZPK7 glass (nd5=1.57, vd5=71.30) with a focal length of -10.395mm. The sixth lens, L6, uses H-ZF72A glass (nd6=1.92, vd6=18.90) and has a focal length of 8.044mm. The seventh lens, L7, uses H-ZPK3 glass (nd7=1.59, vd7=67.29) and has a focal length of 64.102mm. The eighth lens, L8, uses H-ZLAF90 glass (nd8=2.00, vd8=25.43) and has a focal length of -6.528mm.

[0061] Example 2 differs from Example 1 in lens material and surface parameters, but both satisfy the design constraints of this invention. For example... Figures 7 to 10 As shown, Example 2 also exhibits excellent performance in terms of MTF, ray fan, field curvature / distortion, and relative illumination: high MTF value at 83 lp / mm, concentrated light convergence, F-Theta distortion within 1%, and edge relative illumination greater than 0.55, resulting in excellent image quality.

[0062] Example 3: Table 3. Optical parameters of Example 3:

[0063] In this embodiment, the first lens L1 uses H-LAF50B glass (nd1=1.77, vd1=49.60) with a focal length of -7.020mm. The second lens L2 uses H-ZLAF89L glass (nd2=1.95, vd2=32.31) with a focal length of -9.440mm. The third lens L3 uses H-LAK53B glass (nd3=1.76, vd3=52.32) with a focal length of -5.619mm. The fourth lens L4 uses H-ZLAF92 glass (nd4=2.00, vd4=28.32) with a focal length of 4.865mm. The fifth lens L5 uses H-ZPK5 glass (nd5=1.59, vd5=68.34) with a focal length of -9.433mm. The sixth lens, L6, uses H-ZF88 glass (nd6=1.95, vd6=17.94) and has a focal length of 7.737mm. The seventh lens, L7, uses H-ZPK5 glass (nd7=1.59, vd7=68.34) and has a focal length of 55.303mm. The eighth lens, L8, uses H-ZLAF92 glass (nd8=2.00, vd8=28.32) and has a focal length of -6.394mm.

[0064] like Figures 12 to 15 As shown, Example 3 also demonstrates excellent performance in terms of MTF, ray fan, field curvature / distortion, and relative illumination. In particular, the aperture size of each lens is slightly different in Example 3, but the overall miniaturization requirements of TTL < 21 mm and effective diameter of each lens < φ12 mm are still met.

[0065] Based on the performance data of the three embodiments above, the fisheye lens of the present invention achieves: TTL < 21mm, effective diameter of each lens < φ12mm, achieving a high degree of miniaturization; MTF greater than 0.6 within a 0.8 field of view at a frequency of 83lp / mm, and greater than 0.45 across the entire field of view, resulting in high imaging clarity; target height > 4.6mm, compatible with 1 / 2.4-inch image sensors; relative illumination greater than 55% at the maximum field of view, with good edge illumination uniformity; F-Theta distortion < 1%, with minimal geometric deformation, far superior to traditional fisheye lenses. The present invention possesses technical advantages in balancing large target area, high illumination, low distortion, miniaturization, and high-definition imaging.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A fisheye lens, characterized in that, It sequentially comprises, from the object side to the image side along the optical axis: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a protective glass, wherein a stop is arranged between the fourth lens and the fifth lens; The first lens has negative refractive power, the object side surface thereof is a convex surface, and the image side surface thereof is a concave surface; The second lens has negative refractive power, the object side surface thereof is a convex surface, and the image side surface thereof is a concave surface; The third lens has negative refractive power, the object side surface thereof is a convex surface, and the image side surface thereof is a concave surface; The fourth lens has positive refractive power, the object side surface thereof is a convex surface, and the image side surface thereof is a convex surface; The fifth lens has positive refractive power, the object side surface thereof is a convex surface, and the image side surface thereof is a convex surface; The sixth lens has negative refractive power, the object side surface thereof is a concave surface, and the image side surface thereof is a convex surface; The seventh lens has positive refractive power, the object side surface thereof is a convex surface, and the image side surface thereof is a convex surface; The eighth lens has negative refractive power, the object side surface thereof is a concave surface, and the image side surface thereof is a concave surface.

2. The fisheye lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are all glass spherical lenses.

3. The fisheye lens according to claim 1, characterized in that, The refractive index of the first lens is set as nd1, and nd1>1.

75.

4. The fisheye lens according to claim 1, characterized in that, The refractive index of the first lens is set as nd1, and 1.7<nd1<1.9, the Abbe number thereof is set as vd1, and 35<vd1<50; The refractive index of the second lens is set as nd2, and 1.9<nd2<2.1, the Abbe number thereof is set as vd2, and 20<vd2<40; The refractive index of the third lens is set as nd3, and 1.7<nd3<1.9, the Abbe number thereof is set as vd3, and 40<vd3<60; The refractive index of the fourth lens is set as nd4, and 1.95<nd4<2.05, the Abbe number thereof is set as vd4, and 20<vd4<30; The refractive index of the fifth lens is set as nd5, and 1.5<nd5<1.6, the Abbe number thereof is set as vd5, and 60<vd5<80; The refractive index of the sixth lens is set as nd6, and 1.9<nd6<2.0, the Abbe number thereof is set as vd6, and 15<vd6<25; The refractive index of the seventh lens is set as nd7, and 1.5<nd7<1.6, the Abbe number thereof is set as vd7, and 60<vd7<80; The refractive index of the eighth lens is set as nd8, and 1.95<nd8<2.05, the Abbe number thereof is set as vd8, and 20<vd8<30.

5. The fisheye lens according to claim 4, characterized in that, The Abbe number vd5 of the fifth lens and the Abbe number vd6 of the sixth lens satisfy: |vd5-vd6|>40; the Abbe number vd7 of the seventh lens and the Abbe number vd8 of the eighth lens satisfy: |vd7-vd8|>40.

6. The fisheye lens according to claim 1, characterized in that, The total length TTL of the optical system of the lens and the focal length F of the optical system satisfy: 12<TTL / F<16.

7. The fisheye lens according to claim 1, characterized in that, The total length TTL of the optical system of the lens and the f-number FNO satisfy: 10<TTL / FNO<12.

8. The fisheye lens according to claim 1, characterized in that, The total optical length (TTL) of the lens is less than 21 mm, and the effective aperture of the first to eighth lenses is less than φ12 mm.

9. The fisheye lens according to claim 1, characterized in that, The lens has an MTF greater than 0.6 within a 0.8 field of view and greater than 0.45 across the entire field of view at a spatial frequency of 83 lp / mm; the lens has a target surface height greater than 4.6 mm; the lens has an F-Theta distortion of less than 1%; and the lens has a relative illumination greater than 55% at the maximum field of view.

10. The fisheye lens according to any one of claims 1 to 9, characterized in that, The lens is compatible with 1 / 2.4-inch image sensors.

Images