A fisheye lens

Abstract

The embodiment of the present invention discloses a fisheye lens. The fisheye lens comprises a first lens, a second lens, an aperture, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in sequence from the object side to the image side along the optical axis; the first lens, the fourth lens and the sixth lens have negative focal lengths; the second lens, the third lens and the fifth lens have positive focal lengths; the focal length of the fisheye lens is f, the focal length of the first lens is f1, and the focal lengths of the first lens and the fisheye lens satisfy the relationship: 0.8<|f1 / f|<2.0. The embodiment of the present invention can achieve high-quality imaging quality while achieving large field angles, large target surfaces and miniaturization requirements by reasonably allocating the focal length ratio and setting the focal length range of the first lens. It can also meet the characteristics of short system length and large effective image surface, have day and night confocal function, and ensure that the resolution meets the imaging requirements when used in an environment of ‑40℃~80℃.

Description

Technical Field

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

[0002] Ultra-wide-angle lenses have been widely used in security, vehicle-mounted, access control and other fields in recent years because they can achieve all-round shooting without blind spots. As the market application puts forward new requirements for lenses, the effective image surface demand is getting larger and larger, the distortion of the lens is required to be smaller and smaller, and the lens volume is required to be smaller and smaller. With the development of the security industry, the application of monitoring equipment is becoming more and more extensive, and the shooting range requirements of the optical system are also increasing. The existing optical structure is difficult to meet the growing demand. Summary of the invention

[0003] The invention provides a fisheye lens to meet the requirements of a large viewing angle, a large target surface and a miniaturized lens.

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

[0005] The first lens, the fourth lens and the sixth lens have negative optical power; the second lens, the third lens and the fifth lens have positive optical power;

[0006] The focal length of the fisheye lens is f, the focal length of the first lens is f1, and the focal lengths of the first lens and the fisheye lens satisfy the relationship: 0.8<|f1 / f|<2.0.

[0007] Optionally, the focal length of the second lens is f2, and the focal lengths of the second lens and the fisheye lens satisfy the relationship: |f2 / f|>2.5;

[0008] The focal length of the third lens is f3, and the focal lengths of the third lens and the fisheye lens satisfy the relationship: 1.0<|f3 / f|<2.5;

[0009] The focal length of the fourth lens is f4, and the focal lengths of the fourth lens and the fisheye lens satisfy the relationship: 1.0<|f4 / f|<3.2;

[0010] The focal length of the fifth lens is f5, and the focal lengths of the fifth lens and the fisheye lens satisfy the relationship: 0.8<|f5 / f|<2.0;

[0011] The focal length of the sixth lens is f6, and the focal lengths of the sixth lens and the fisheye lens satisfy the relationship: |f6 / f|>2.3.

[0012] Optionally, the refractive index of the first lens nd1 satisfies nd1>1.7.

[0013] Optionally, the first lens is a glass lens, the third lens is a glass lens; the second lens, the fourth lens, the fifth lens and the sixth lens are plastic lenses.

[0014] Optionally, the Abbe number Vd3 of the third lens satisfies Vd3>60, and the Abbe number Vd5 of the fifth lens satisfies Vd5>40.

[0015] Optionally, the first lens is a spherical lens, the second lens, the fourth lens, the fifth lens and the sixth lens are aspherical lenses, and the third lens is a spherical lens or an aspherical lens.

[0016] Optionally, the surface of the lens adjacent to the object plane is the object side surface, and the surface of the lens adjacent to the image plane is the image side surface; the object side surface of the first lens is convex, and the image side surface is concave; the object side surface of the second lens is concave, and the image side surface is convex; the object side surface of the third lens is convex, and the image side surface is convex; the object side surface of the fourth lens is convex, and the image side surface is concave; the object side surface of the fifth lens is convex, and the image side surface is convex; the object side surface of the sixth lens is concave, and the image side surface is convex.

[0017] Optionally, a ratio of an effective image plane IC of the fisheye lens to a total optical length TTL of the fisheye lens satisfies: IC / TTL>0.5.

[0018] Optionally, the object-side field of view of the fisheye lens is greater than 160° and less than 220°.

[0019] The fisheye lens provided by the embodiment of the present invention can greatly affect the wide-angle characteristics of the fisheye lens by reasonably allocating the focal ratio and utilizing the focal power of the first lens. The focal length f1 and the focal length f of the fisheye lens are set to meet 0.8<|f1 / f|<2.0, so as to obtain an ultra-large field of view, and obtain high-quality imaging quality while achieving a large image surface. On this basis, the fisheye lens provided by the embodiment of the present invention can meet the numerical requirements of IC / TTL>0.5, 160°<FOV<220°, and achieve the requirements of large field of view, large target surface, and miniaturization; at the same time, it can also have a day and night confocal function, and can be used in an environment of -40℃~80℃ to ensure that the resolution meets the imaging requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a structural schematic diagram of a fisheye lens provided by an embodiment of the present invention;

[0021] Figure 2 yes Figure 1The MTF diagram of the fisheye lens shown is at room temperature 20°C and visible light;

[0022] Figure 3 yes Figure 1 F-theta distortion diagram of the fisheye lens shown;

[0023] Figure 4 is a schematic structural diagram of another fisheye lens provided by an embodiment of the present invention;

[0024] Figure 5 yes Figure 4 The MTF diagram of the fisheye lens shown is at room temperature 20°C and visible light;

[0025] Figure 6 yes Figure 4 F-theta distortion plot of the fisheye lens shown. DETAILED DESCRIPTION

[0026] 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.

[0027] Figure 1 is a schematic diagram of the structure of a fisheye lens provided by an embodiment of the present invention, with reference to Figure 1 The fisheye lens comprises a first lens 11, a second lens 12, an aperture 20, a third lens 13, a fourth lens 14, a fifth lens 15 and a sixth lens 16 which are arranged in sequence from the object side to the image side along the optical axis;

[0028] The first lens 11, the fourth lens 14 and the sixth lens 16 have negative optical power; the second lens 12, the third lens 13 and the fifth lens 15 have positive optical power;

[0029] The focal length of the fisheye lens is f, the focal length of the first lens 11 is f1, and the focal lengths of the first lens 11 and the fisheye lens satisfy the relationship: 0.8<|f1 / f|<2.0.

[0030] Among them, the optical power of the optical system is equal to the difference between the convergence of the image-side light beam of the lens and the convergence of the object-side light beam, which characterizes the ability of the optical system to deflect light. The larger the absolute value of the optical power, the stronger the ability to bend light, and the smaller the absolute value of the optical power, the weaker the ability to bend light. When the optical power is a positive number, the refraction of light is convergent; when the optical power is a negative number, the refraction of light is divergent. The optical power can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can also 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 this embodiment, each lens can be fixed to a lens barrel ( Figure 1 (not shown in the figure), by reasonably allocating the optical power of the lens, the imaging effect of the large aperture fixed focus lens is better, where the optical power is the reciprocal of the focal length.

[0031] As described above, the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15 and the sixth lens 16 can reasonably allocate the focal length ratio, and can use the first lens 11 to increase the field of view, and use other lenses to converge and diverge the light, while correcting the on-axis aberration and off-axis aberration, so as to achieve the miniaturization of the entire fisheye lens, improve the imaging quality, and realize a lens with a large target surface and a large field of view. It should be noted that the focal length of the first lens 11 is the main element for collecting light in the entire fisheye lens, and the ratio of its focal length to the focal length of the entire fisheye lens will greatly affect the wide-angle characteristics of the fisheye lens. Setting the focal length f1 and the focal length f of the fisheye lens to meet 0.8<|f1 / f|<2.0 can obtain an ultra-large field of view, and through the cooperation of other lenses, it is possible to achieve a large image surface while obtaining high-quality imaging quality. On this basis, the fisheye lens provided in the embodiment of the present invention can meet the numerical requirements of IC / TTL>0.5, 160°<FOV<220°, and achieve the requirements of ultra-large field of view, large target surface, and miniaturization; at the same time, it can also have day and night confocal functions, and can be used in an environment of -40℃~80℃ to ensure that the resolution meets the imaging requirements.

[0032] For other lenses in the fisheye lens, the embodiment of the present invention also provides a specific implementation method. Figure 1 Specifically, the focal length of the second lens 12 is f2, and the focal lengths of the second lens 12 and the fisheye lens satisfy the relationship: |f2 / f|>2.5;

[0033] The focal length of the third lens 13 is f3, and the focal lengths of the third lens 12 and the fisheye lens satisfy the relationship: 1.0<|f3 / f|<2.5;

[0034] The focal length of the fourth lens 14 is f4, and the focal lengths of the fourth lens 14 and the fisheye lens satisfy the relationship: 1.0<|f4 / f|<3.2;

[0035] The focal length of the fifth lens 15 is f5, and the focal lengths of the fifth lens 15 and the fisheye lens satisfy the relationship: 0.8<|f5 / f|<2.0;

[0036] The focal length of the sixth lens 16 is f6, and the focal lengths of the sixth lens 16 and the fisheye lens satisfy the relationship: |f6 / f|>2.3.

[0037] Among them, the focal length f2 of the second lens is set to satisfy |f2 / f|>2.5, and its main function is to correct off-axis aberrations such as field curvature and astigmatism; the focal length f3 of the third lens is set to satisfy 1.0<|f3 / f|<2.5, and its main function is to correct chromatic aberration; the focal length f4 of the fourth lens is set to satisfy 1.0<|f4 / f|<3.2, and its main function is to correct on-axis aberrations, such as spherical aberration; the focal length f6 of the sixth lens is set to satisfy |f6 / f|>2.3, and its main function is to correct field curvature, astigmatism and residual aberration. As above, on the basis of using the focal length range of the first lens to achieve a large field of view, and then using the focal lengths of each other lens for targeted design, the light collected by the first lens can be reasonably and effectively corrected, so that the aberration of the entire fisheye lens can be better balanced.

[0038] Further optionally, the refractive index nd1 of the first lens may be set to satisfy nd1>1.7. The refractive index of the first lens 11 also determines the light convergence capability of the first lens 11. On the basis of the above embodiment, the refractive index nd1 of the first lens is set to satisfy nd1>1.7, which can better collect light, thereby further improving the field of view of the fisheye lens and meeting the requirements of the ultra-wide-angle lens.

[0039] In the fisheye lens as described above, the first lens 11 can also be set as a glass lens, the third lens 12 can be set as a glass lens; the second lens 12, the fourth lens 14, the fifth lens 15 and the sixth lens 16 can be plastic lenses. Among them, the first lens 11 is a lens exposed on the outside of the entire fisheye lens. The use of a glass lens can not only achieve a waterproof effect, but also ensure wear resistance compared to other materials, which is beneficial to the performance stability of the entire fisheye lens. The function of the third lens 13 is mainly to correct the chromatic aberration of the edge field of view. By setting the third lens 13 to use a glass lens, the temperature stability of the glass lens can be used to ensure the performance stability of the fisheye lens in high and low temperature environments. In order to increase the field of view while controlling the production cost and production difficulty, it is preferred that other lenses use plastic lenses. Compared with glass lenses, the preparation difficulty and preparation cost of plastic lenses are lower, which is conducive to mass production.

[0040] It can be understood that the third lens and the fifth lens are mainly used for correcting chromatic aberration in the entire fisheye lens, and therefore, the Abbe number Vd3 of the third lens can be set to satisfy Vd3>60, and the Abbe number Vd5 of the fifth lens can be set to satisfy 40. Wherein, in the case of setting the lower limit values ​​of the Abbe number of the third lens and the Abbe number of the fifth lens, it can be ensured that the third lens and the fifth lens are low-dispersion lenses, and the use of lenses with lower dispersion for chromatic aberration correction can improve the chromatic aberration correction capability to a certain extent, thereby improving the imaging quality of the fisheye lens.

[0041] Considering the preparation process and mass production requirements of the fisheye lens, in the embodiment of the present invention, optionally, the first lens is a spherical lens, the second lens, the fourth lens, the fifth lens and the sixth lens are aspherical lenses, and the third lens is a spherical lens or an aspherical lens. Among them, on the basis of using a glass lens for the first lens, setting it as a spherical lens is more convenient for preparation and mass production.

[0042] Specifically, optionally, the surface of the lens adjacent to the object plane is the object side surface, and the surface of the lens adjacent to the image plane is the image side surface; the object side surface of the first lens 11 is convex, and the image side surface is concave; the object side surface of the second lens 12 is concave, and the image side surface is convex; the object side surface of the third lens 13 is convex, and the image side surface is convex; the object side surface of the fourth lens 14 is convex, and the image side surface is concave; the object side surface of the fifth lens 15 is convex, and the image side surface is convex; the object side surface of the sixth lens 16 is concave, and the image side surface is convex.

[0043] Optionally, when designing the fisheye lens, the relevant parameters of each lens can be adjusted according to actual needs, so as to set the ratio of the effective image plane IC of the fisheye lens to the total optical length TTL of the fisheye lens so that IC / TTL satisfies: IC / TTL>0.5. Similarly, the object field angle of the fisheye lens can be set to be greater than 160° and less than 220°.

[0044] The above-mentioned fisheye lens is described below with two specific embodiments. Figure 1 As shown, the fisheye lens includes a first lens 11, a second lens 12, an aperture 20, a third lens 13, a fourth lens 14, a fifth lens 15 and a sixth lens 16 which are arranged in sequence from the object side to the image side along the optical axis;

[0045] The first lens 11, the fourth lens 14 and the sixth lens 16 have negative optical power; the second lens 12, the third lens 13 and the fifth lens 15 have positive optical power;

[0046] The focal length of the fisheye lens is f, the focal length of the first lens 11 is f1, and the focal lengths of the first lens 11 and the fisheye lens satisfy the relationship: 0.8<|f1 / f|<2.0;

[0047] The surface of the lens adjacent to the object plane is the object side surface, and the surface of the lens adjacent to the image plane is the image side surface; the object side surface of the first lens 11 is convex, and the image side surface is concave; the object side surface of the second lens 12 is concave, and the image side surface is convex; the object side surface of the third lens 13 is convex, and the image side surface is convex; the object side surface of the fourth lens 14 is convex, and the image side surface is concave; the object side surface of the fifth lens 15 is convex, and the image side surface is convex; the object side surface of the sixth lens 16 is concave, and the image side surface is convex. Among them, the first lens 11 is a spherical lens, and the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15 and the sixth lens 16 are aspherical lenses.

[0048] In this embodiment, the design values ​​of the first lens 11 to the sixth lens 16 are shown in Table 1 below.

[0049] Table 1 shows a design value of the fisheye lens (f=1 mm; aperture F1.8):

[0050] Surface number Face type Curvature radius (mm) Thickness(mm) Refractive Index Abbe number K Value S1 Standard surface 4.09 0.23 1.83 42.73 0.00 S2 Standard surface 0.79 0.79 0.00 S3 Aspheric -1.87 0.63 1.66 20.38 5.55 S4 Aspheric -1.24 0.15 -10.66 Aperture PL Infinity 0.09 0.00 S6 Aspheric 2.60 0.67 1.50 81.56 -64.55 S7 Aspheric -1.03 0.02 -19.52 S8 Aspheric 10.18 0.23 1.64 23.50 -46.05 S9 Aspheric 0.76 0.09 -6.15 S10 Aspheric 1.06 1.13 1.54 55.99 0.28 S11 Aspheric -1.18 0.05 -0.38 S12 Aspheric -0.81 0.25 1.64 23.50 -0.43 S13 Aspheric -1.22 1.43 -5.22

[0051] The surface numbers in Table 1 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; the radius of curvature represents the degree of 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, where "PL" represents that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, and a blank space represents that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to light, and a blank space represents that the current position is air; the K value represents the numerical value of the best fitting cone coefficient of the aspheric surface.

[0052] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following representation:

[0053]

[0054] Among them, z is the axial vector height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0055] The aspheric surface parameters in this embodiment are shown in Table 2:

[0056] Table 2 is a design value of the aspheric coefficient in the fisheye lens

[0057] Surface number A B C D E F G S3 -0.13 0.20 -0.51 0.20 10.92 -29.74 29.12 S4 -0.91 2.78 -8.54 20.62 -34.65 37.96 -20.47 S6 0.01 -0.17 0.57 -0.85 -0.42 0.24 -0.69 S7 -1.57 5.21 -11.45 13.23 -6.54 -0.10 0.11 S8 -0.56 1.70 -1.87 -2.61 0.87 13.64 -13.42 S9 0.01 -0.38 6.21 -23.79 39.30 -29.77 8.34 S10 -1.07 2.99 -9.55 26.82 -50.52 50.02 -19.76 S11 -0.17 0.31 -0.32 -0.12 1.08 -1.75 0.96 S12 0.44 -0.32 0.48 -0.55 -0.41 1.13 -0.36 S13 0.16 -0.56 1.96 -4.28 4.94 -2.84 0.65

[0058] Furthermore, the first lens to the sixth lens satisfy the following conditions:

[0059] f1=-1.2mm f2=3.9mm f3=1.6mm f4=-1.3mm f5=1.3mm f6=-5.0mm TTL=5.77mm IC / TTL=0.52

[0060] Among them, f1 to f6 represent the focal lengths of the first lens to the sixth lens respectively; n1 to n6 represent the refractive indices of the first lens to the sixth lens respectively; R1, R3, R5, R7, R9, R11 represent the curvature radii of the center of the surface of the first lens to the sixth lens facing the object side respectively, R2, R4, R6, R8, R10, R12 represent the curvature radii of the center of the surface of the first lens to the sixth lens facing the image side respectively, and "-" represents the negative direction.

[0061] Figure 2 yes Figure 1 The MTF diagram of the fisheye lens shown in the figure is at room temperature 20℃ and visible light. Figure 2 It can be seen that the transfer function of the central field of view of the fisheye lens is about 0.8 when the spatial frequency is 120 line pairs / mm, and the transfer function of the edge field of view is greater than 0.4 when the spatial frequency is 120 line pairs / mm. The fisheye lens provided in this embodiment can obtain good resolution capabilities in both the central field of view and the edge field of view, and can meet the resolution requirements of a large field of view and a large target surface. Figure 3 yes Figure 1 The F-theta distortion diagram of the fisheye lens shown is given by Figure 3 It can be seen that the fisheye lens can better correct the distortion of the optical system, that is, the fisheye lens provided by the embodiment of the present invention has a good imaging effect.

[0062] Figure 4 is a schematic diagram of the structure of another fisheye lens provided by an embodiment of the present invention, referring to Figure 4 The fisheye lens comprises a first lens 11, a second lens 12, an aperture 20, a third lens 13, a fourth lens 14, a fifth lens 15 and a sixth lens 16 which are arranged in sequence from the object side to the image side along the optical axis;

[0063] The first lens 11, the fourth lens 14 and the sixth lens 16 have negative optical power; the second lens 12, the third lens 13 and the fifth lens 15 have positive optical power;

[0064] The focal length of the fisheye lens is f, the focal length of the first lens 11 is f1, and the focal lengths of the first lens 11 and the fisheye lens satisfy the relationship: 0.8<|f1 / f|<2.0;

[0065] The surface of the lens adjacent to the object plane is the object side surface, and the surface of the lens adjacent to the image plane is the image side surface; the object side surface of the first lens 11 is convex, and the image side surface is concave; the object side surface of the second lens 12 is concave, and the image side surface is convex; the object side surface of the third lens 13 is convex, and the image side surface is convex; the object side surface of the fourth lens 14 is convex, and the image side surface is concave; the object side surface of the fifth lens 15 is convex, and the image side surface is convex; the object side surface of the sixth lens 16 is concave, and the image side surface is convex. The first lens 11 and the third lens 13 are spherical lenses, and the second lens 12, the fourth lens 14, the fifth lens 15 and the sixth lens 16 are aspherical lenses.

[0066] In this embodiment, the design values ​​of the first lens 11 to the sixth lens 16 are shown in Table 3 below.

[0067] Table 3 shows a design value of the fisheye lens (f=1.5mm; aperture F2.0):

[0068] Surface number Face type Curvature radius (mm) Thickness(mm) Refractive Index Abbe number K Value S1 Standard surface 8.84 0.36 1.55 75.5 0.00 S2 Standard surface 1.19 1.01 0.00 S3 Aspheric -2.02 1.01 1.64 23.5 -1.38 S4 Aspheric -2.34 0.07 -25.59 Aperture PL Infinity 0.59 0.00 S6 Standard surface 3.14 1.2 1.55 71.7 0.00 S7 Standard surface -2.17 0.07 0.00 S8 Aspheric 3.11 0.33 1.64 23.50 -63.09 S9 Aspheric 1.41 0.17 -13.13 S10 Aspheric 2.42 1.02 1.54 55.99 0.87 S11 Aspheric -1.33 0.06 -0.78 S12 Aspheric -0.81 0.33 1.64 23.50 -0.81 S13 Aspheric -1.42 2.00 -3.77

[0069] The aspheric surface parameters in this embodiment are shown in Table 4:

[0070] Table 4 shows a design value of the aspheric coefficient in the fisheye lens

[0071] Surface number A B C D E F G S3 -0.02 -0.03 0.13 -0.24 0.24 -0.11 0.02 S4 -0.24 0.41 -0.48 0.52 -0.71 0.76 -0.33 S8 0.05 -0.11 -0.11 0.48 -0.71 0.46 -0.11 S9 0.24 -0.65 1.15 -1.22 0.72 -0.22 0.03 S10 -0.18 0.26 -0.58 0.97 -0.85 0.36 -0.06 S11 0.22 -0.24 0.04 0.21 -0.21 0.09 -0.02 S12 0.73 -0.75 0.62 -0.27 0.05 0.00 0.00 S13 0.25 -0.20 0.15 -0.07 0.02 0.00 0.00

[0072] Furthermore, the first lens to the sixth lens satisfy the following conditions:

[0073] f1=-2.53mm f2=86.5mm f3=2.5mm f4=-4.4mm f5=1.7mm f6=-3.6mm TTL=8.26mm IC / TTL=0.51

[0074] Figure 5 yes Figure 4 The MTF diagram of the fisheye lens shown in the figure is at room temperature 20℃ and visible light. Figure 5 It can be seen that the transfer function of the central field of view of the fisheye lens is about 0.8 when the spatial frequency is 80 line pairs / mm, and the transfer function of the edge field of view is about 0.4 when the spatial frequency is 80 line pairs / mm. The fisheye lens provided in this embodiment can obtain good resolution capabilities in both the central field of view and the edge field of view, and can meet the resolution requirements of a large field of view and a large target surface. Figure 6 yes Figure 4 The F-theta distortion diagram of the fisheye lens shown is given by Figure 6 It can be seen that the fisheye lens can better correct the distortion of the optical system, that is, the fisheye lens provided by the embodiment of the present invention has a good imaging effect.

[0075] 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, combinations 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, an aperture, a third lens, a fourth lens, a fifth lens and a sixth lens which are arranged in sequence from the object side to the image side along the optical axis; The first lens, the fourth lens and the sixth lens have negative optical power; the second lens, the third lens and the fifth lens have positive optical power; The focal length of the fisheye lens is f, the focal length of the first lens is f1, and the focal lengths of the first lens and the fisheye lens satisfy the relationship: 0.8<|f1 / f|<2.0; The surface of the lens adjacent to the object side is the object side, and the surface of the lens adjacent to the image side is the image side; the object side surface of the first lens is convex, and the image side surface is concave; the object side surface of the second lens is concave, and the image side surface is convex; the object side surface of the third lens is convex, and the image side surface is convex; the object side surface of the fourth lens is convex, and the image side surface is concave; the object side surface of the fifth lens is convex, and the image side surface is convex; the object side surface of the sixth lens is concave, and the image side surface is convex; The ratio of the effective image plane IC of the fisheye lens to the total optical length TTL of the fisheye lens satisfies: IC / TTL>0.

5.

2. The fisheye lens according to claim 1, characterized in that: The focal length of the second lens is f2, and the focal lengths of the second lens and the fisheye lens satisfy the relationship: |f2 / f|>2.5; The focal length of the third lens is f3, and the focal lengths of the third lens and the fisheye lens satisfy the relationship: 1.0<|f3 / f|<2.5; The focal length of the fourth lens is f4, and the focal lengths of the fourth lens and the fisheye lens satisfy the relationship: 1.0<|f4 / f|<3.2; The focal length of the fifth lens is f5, and the focal lengths of the fifth lens and the fisheye lens satisfy the relationship: 0.8<|f5 / f|<2.0; The focal length of the sixth lens is f6, and the focal lengths of the sixth lens and the fisheye lens satisfy the relationship: |f6 / f|>2.

3.

3. The fisheye lens according to claim 1, characterized in that: Therefore, the refractive index of the first lens nd1 satisfies nd1>1.

7.

4. The fisheye lens according to claim 2, characterized in that: The first lens is a glass lens, the third lens is a glass lens; the second lens, the fourth lens, the fifth lens and the sixth lens are plastic lenses.

5. The fisheye lens according to claim 1, characterized in that: The Abbe number Vd3 of the third lens satisfies Vd3>60, and the Abbe number Vd5 of the fifth lens satisfies Vd5>40.

6. The fisheye lens according to claim 1, characterized in that: The first lens is a spherical lens, the second lens, the fourth lens, the fifth lens and the sixth lens are aspherical lenses, and the third lens is a spherical lens or an aspherical lens.

7. The fisheye lens according to claim 1, characterized in that: The object side field of view FOV of the fisheye lens is greater than 160° and less than 220°.

Images