A fisheye lens

Abstract

The utility model discloses a fish eye lens, this fish eye lens includes: first lens group, plane reflector and second lens group are arranged in proper order from object side to image side, first lens group has negative refractive power, first lens group includes the first lens, second lens and third lens along the first optical axis arrangement from object side to image side, second lens group has positive refractive power, second lens group includes the fourth lens, fifth lens, sixth lens, seventh lens and eighth lens along the second optical axis arrangement from object side to image side, wherein, the first optical axis with second optical axis intersection. The fish eye lens of the utility model can have the characteristics of big aperture, big imaging target surface, small volume and low cost.

Description

Technical Field

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

[0002] A fisheye lens optical system is an optical system with a large field of view and a large aperture. Because it can obtain all optical information within a hemispherical or even super-hemispherical spatial field of view without rotating the fisheye lens, it is widely used in fields such as security monitoring, automotive driving, unmanned equipment, and sports photography.

[0003] However, existing fisheye lenses still have many shortcomings. For example, when fisheye lenses can meet the requirements of large aperture and large imaging target surface, they are usually large in size, which makes it impossible to use fisheye lenses in small devices and limits the application scenarios of fisheye lenses. Utility Model Content

[0004] This invention provides a fisheye lens that, while having a large imaging target surface and aperture, ensures a small size, thus enabling the fisheye lens to be applicable to more scenarios.

[0005] This utility model provides a fisheye lens, which includes: a first lens group, a plane mirror, and a second lens group arranged sequentially from the object side to the image side;

[0006] The first lens group has negative optical power; the first lens group includes a first lens, a second lens, and a third lens arranged along a first optical axis from the object side to the image side;

[0007] The second lens group has positive optical power; the second lens group includes a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged along the second optical axis from the object side to the image side;

[0008] The first optical axis intersects with the second optical axis.

[0009] Optionally, the angle between the first optical axis and the second optical axis is 90°.

[0010] Optionally, the angle between the reflecting surface of the plane mirror and the first optical axis is θ1; the angle between the reflecting surface of the plane mirror and the second optical axis is θ2; wherein, θ1 = θ2.

[0011] Optionally, the fifth lens and the sixth lens constitute a cemented doublet lens.

[0012] Optionally, the fifth lens and the sixth lens are glass spherical lenses.

[0013] Optionally, the Abbe number V5 of the fifth lens and the Abbe number V6 of the sixth lens satisfy: 30≤|v5-v6|≤40;

[0014] The refractive index Nd5 of the fifth lens satisfies: 1.55≤Nd5≤1.80;

[0015] The refractive index Nd6 of the sixth lens satisfies: 1.45≤Nd6≤1.65.

[0016] Optionally, the combined focal length of the fifth lens and the sixth lens is F56, and the focal length of the fisheye lens is F;

[0017] Among them, 3.5≤F56 / F≤5.

[0018] Optionally, the first lens, the second lens, the third lens, the fourth lens, the seventh lens, and the eighth lens are all aspherical lenses.

[0019] Optionally, the seventh lens is a plastic aspherical lens.

[0020] Optionally, the first lens, the second lens, the third lens, the fourth lens, and the eighth lens are all glass aspherical lenses.

[0021] Optionally, the first lens has negative optical power, the second lens has negative optical power, the seventh lens has negative optical power, and the eighth lens has positive optical power.

[0022] Optionally, the optical power of the first lens group is Z1, and the combined optical power of the first lens and the second lens is φ12;

[0023] Wherein, 0.85≤φ12 / Z1≤1.00.

[0024] Optionally, the optical power of the first lens group is Z1, the optical power of the first lens is φ1, and the optical power of the second lens is φ2;

[0025] Among them, 2.70≤φ1 / Z1≤3.40; 1.65≤φ2 / Z1≤2.00.

[0026] Optionally, the optical power of the first lens is φ1, the optical power of the third lens is φ3, and the focal length of the fisheye lens is F;

[0027] Among them, -10.3≤φ1 / F≤-9.0; -61.0≤φ3 / F≤-45.5.

[0028] Optionally, the optical power of the second lens group is Z2, the optical power of the seventh lens is φ7, and the optical power of the eighth lens is φ8;

[0029] Among them, -0.75≤φ7 / Z2≤-0.60; 0.9≤φ8 / Z2≤1.1.

[0030] Optionally, the optical power of the fourth lens is φ4, the optical power of the seventh lens is φ7, the optical power of the eighth lens is φ8, and the focal length of the fisheye lens is F;

[0031] Among them, 5.65≤φ4 / F≤6.25; -3.0≤φ7 / F≤-2.4; -10.3≤φ8 / F≤4.

[0032] Optionally, the refractive index Nd1 of the first lens satisfies: 1.65≤Nd1≤1.80.

[0033] Optionally, the refractive index Nd5 of the fifth lens satisfies: 1.55≤Nd5≤1.80.

[0034] Optionally, the length of the object-side surface of the first lens to the image-side surface of the third lens on the first optical axis is TG1, and the effective optical aperture of the object-side surface of the first lens is D1.

[0035] Among them, 1.65≤TG1 / D1≤1.72.

[0036] Optionally, the length from the object-side surface of the first lens to the image-side surface of the third lens on the first optical axis is TG1, and the length from the object-side surface of the fourth lens to the image-side surface of the eighth lens on the first optical axis is TG2.

[0037] Wherein, -0.70≤TG2 / TG1≤-0.65.

[0038] Optionally, the image plane diameter of the fisheye lens is ID1, and the length of the object-side surface of the fourth lens to the image-side surface of the eighth lens on the first optical axis is TG2.

[0039] Where -0.57≤ID1 / TG2≤-0.54.

[0040] The technical solution of this utility model, by setting a first lens group, a plane mirror, and a second lens group arranged sequentially from the object side to the image side, and making the first lens group a negative optical power lens group composed of three lenses with optical power, and the second lens group a positive optical power lens group composed of five lenses with optical power, ensures that the fisheye lens has a large aperture and a large imaging target surface; at the same time, by setting a plane mirror in the optical path between the first lens group and the second lens group, the plane mirror reflects the light rays that are incident on the object side and pass through the first lens group before entering the second lens group, and the light rays... The image is formed by passing through the second lens group to the imaging plane, thus ensuring the imaging effect of the fisheye lens. In addition, the lenses in the first lens group G1 are arranged along the first optical axis, and the lenses in the second lens group G2 are arranged along the second optical axis, and the first and second optical axes intersect. Compared with the case where all lenses in a fisheye lens are arranged along the first or second optical axis, the size of the fisheye lens along the first optical axis and the size along the second optical axis can be effectively reduced, which is beneficial to the small size of the fisheye lens, making it suitable for more application scenarios. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of a fisheye lens provided in an embodiment of the present invention;

[0042] Figure 2 yes Figure 1 The diagram shows the chromatic aberration along the vertical axis of the fisheye lens;

[0043] Figure 3 yes Figure 1 The diagram shows the beam pattern of the fisheye lens.

[0044] Figure 4 yes Figure 1 The diagram shows the field curvature distortion curve of the fisheye lens.

[0045] Figure 5 yes Figure 1 The diagram shows the MTF curve of the fisheye lens;

[0046] Figure 6 This is a schematic diagram of another fisheye lens provided in an embodiment of the present invention;

[0047] Figure 7 yes Figure 6 The diagram shows the chromatic aberration along the vertical axis of the fisheye lens;

[0048] Figure 8 yes Figure 6 The diagram shows the beam pattern of the fisheye lens.

[0049] Figure 9 yes Figure 6The diagram shows the field curvature distortion curve of the fisheye lens.

[0050] Figure 10 yes Figure 6 The diagram shows the MTF curve of the fisheye lens;

[0051] Figure 11 This is a schematic diagram of another fisheye lens provided in this embodiment of the present invention;

[0052] Figure 12 yes Figure 11 The diagram shows the chromatic aberration along the vertical axis of the fisheye lens;

[0053] Figure 13 yes Figure 11 The diagram shows the beam pattern of the fisheye lens.

[0054] Figure 14 yes Figure 11 The diagram shows the field curvature distortion curve of the fisheye lens.

[0055] Figure 15 yes Figure 11 The diagram shows the MTF curve of the fisheye lens. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be fully described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Various modifications and variations can be made to this utility model without departing from its spirit or scope, which is obvious to those skilled in the art. Therefore, this utility model is intended to cover modifications and variations of this utility model that fall within the scope of the corresponding claims (the claimed technical solutions) and their equivalents.

[0057] Furthermore, the terms "first," "second," and similar terms used in the embodiments of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, terms such as "an," "one," or "the" do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "including" or "comprising" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described object changes. In addition, descriptions of "same" or "equal" in the embodiments of this disclosure do not mean that two objects are completely equal in size or shape; they are allowed to be approximately the same or approximately equal within a certain error range.

[0058] It should be noted that the implementation methods provided in this utility model embodiment can be combined with each other without contradiction.

[0059] Figure 1 This is a structural schematic diagram of a fisheye lens provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the fisheye lens includes: a first lens group G1, a plane mirror G3, and a second lens group G2 arranged sequentially from the object side to the image side; the first lens group G1 has negative optical power; the first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3 arranged along a first optical axis from the object side to the image side; the second lens group G2 has positive optical power; the second lens group G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 arranged along a second optical axis from the object side to the image side; wherein, the first optical axis intersects the second optical axis.

[0060] As can be understood, optical power equals the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. When optical power is positive, the refraction of light is converging; when optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group).

[0061] In this embodiment, by setting the first lens group G1 to have negative optical power and the second lens group G2 to have positive optical power, that is, the optical power of the first lens group G1 and the second lens group G2 on both sides of the plane mirror G3 are opposite, and the first lens group G1 consists of three lenses with optical power: a first lens, a second lens, and a third lens, and the second lens group G2 consists of five lenses with optical power: a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens. The lenses in the first lens group and the lenses in the second lens group cooperate with each other, so that the fisheye lens can have a large aperture and a large imaging target surface.

[0062] Furthermore, the first optical axis of the first lens group G1 intersects the second optical axis of the second lens group G2, so that light rays incident from the object side pass through the first lens group G1 and are reflected by the reflecting surface of the plane mirror G3, causing the optical axis of the light rays to be adjusted from the first optical axis to the second optical axis and then incident on the second lens group G2; after being refracted and transmitted by each lens in the second lens group G2, they reach the imaging surface to form an image. Thus, by setting a plane mirror G3 to change the optical axis during light propagation, it is ensured that light can enter the first lens group G1 and the second lens group G2 sequentially from the object side and reach the imaging surface for imaging. At the same time, by arranging the lenses in the first lens group G1 along the first optical axis and the lenses in the second lens group G2 along the second optical axis, and with the first and second optical axes intersecting, in an optional embodiment, the angle between the first and second optical axes is 90°, that is, the first and second optical axes are perpendicular to each other. Compared with the case where all lenses in a fisheye lens are arranged along the first or second optical axis, the size of the fisheye lens along the first optical axis and the size along the second optical axis can be effectively reduced while ensuring the imaging effect of the fisheye lens. For example, the thickness of the fisheye lens can be controlled within 20mm, which is beneficial to the small size of the fisheye lens, making it suitable for more application scenarios.

[0063] Based on the above embodiments, optionally, the angle between the reflecting surface of the plane mirror G3 and the first optical axis is θ1; the angle between the reflecting surface of the plane mirror G3 and the second optical axis is θ2; where θ1 = θ2. Thus, when the angle between the first and second optical axes is 90°, the angle between the reflecting surface of the plane mirror G3 and both the first and second optical axes can be 45°. This allows light rays passing through the first lens group G1 to enter the reflecting surface of the plane mirror G3 at an incident angle of 45°, and then exit from the reflecting surface of the plane mirror G3 at an exit angle of 45° before entering the second lens group G2. This ensures an adequate amount of light entering the second lens group G2, thereby improving the relative illumination of the fisheye lens and ultimately enhancing its imaging quality.

[0064] This embodiment employs a first lens group, a plane mirror, and a second lens group arranged sequentially from the object side to the image side. The first lens group consists of three lenses with optical power, forming a negative optical power lens group, while the second lens group consists of five lenses with optical power, forming a positive optical power lens group. This ensures the fisheye lens has a large aperture and a large imaging target surface. Simultaneously, a plane mirror is placed in the optical path between the first and second lens groups. The plane mirror reflects light incident from the object side and passing through the first lens group before it enters the second lens group. Furthermore, the light passing through the first lens group... The two lens groups reach the imaging plane to form an image, thus ensuring the imaging effect of the fisheye lens. In addition, the lenses in the first lens group G1 are arranged along the first optical axis, and the lenses in the second lens group G2 are arranged along the second optical axis, and the first and second optical axes intersect. Compared with the case where all lenses in a fisheye lens are arranged along the first or second optical axis, this can effectively reduce the size of the fisheye lens along the first optical axis and the second optical axis, which is beneficial to the small size of the fisheye lens, making it suitable for more application scenarios.

[0065] Based on the above embodiments, optionally, the object-side surface of the first lens L1 is convex and the image-side surface is concave; the object-side surface of the second lens L2 is convex and the image-side surface is concave; the object-side surface of the third lens L3 is concave and the image-side surface is convex; the object-side surface of the fourth lens L4 is convex and the image-side surface is concave; the object-side surface of the fifth lens L5 is convex and the image-side surface is concave; the object-side surface of the sixth lens L6 is convex and the image-side surface is convex; the object-side surface of the seventh lens L7 is concave and the image-side surface is concave; and the object-side surface of the eighth lens L8 is convex and the image-side surface is convex.

[0066] In this context, the object-side surface of a lens can be understood as the surface of the lens closest to the object plane, and the image-side surface can be understood as the surface of the lens closest to the image plane. A concave object-side surface means that the object-side surface of the lens is recessed towards the object plane near the optical axis, and a convex object-side surface means that the object-side surface of the lens is convex towards the object plane near the optical axis. Similarly, a concave image-side surface means that the image-side surface of the lens is recessed towards the image plane near the optical axis, and a convex image-side surface means that the image-side surface of the lens is convex towards the image plane near the optical axis.

[0067] In this embodiment, by rationally setting the surface shape of each lens, the structure becomes more compact, which is beneficial for the small size of the fisheye lens. At the same time, it can ensure a smoother light path, thereby improving the imaging quality of the fisheye lens while ensuring a large aperture and a large imaging target surface.

[0068] Optionally, the fifth lens L5 and the sixth lens L6 can form a cemented doublet.

[0069] In this embodiment, the cemented configuration of the fifth lens L5 and the sixth lens L6 can be understood as the image-side surface of the fifth lens L5 being bonded to the object-side surface of the sixth lens L6. By forming a cemented doublet lens, the air gap between the fifth lens L5 and the sixth lens L6 is reduced, which helps to reduce the overall optical length of the fisheye lens. It also reduces tolerance sensitivity issues such as tilting / eccentricity during lens assembly, simplifies the assembly process in fisheye lens manufacturing, and improves equipment efficiency. Simultaneously, the cemented configuration of the fifth lens L5 and the sixth lens L6 reduces light loss caused by inter-lens reflection, increases illumination, and reduces the risk of ghosting. Furthermore, cemented lenses can be used to minimize or eliminate chromatic aberration, thereby improving image quality, reducing light energy reflection loss, and enhancing the sharpness of the lens image. In an optional embodiment, the fifth lens L5 and the sixth lens L6 can be supported by a gasket or bonded with adhesive; this embodiment does not limit the specific bonding method.

[0070] In an optional embodiment, the fifth lens L5 and the sixth lens L6 are glass spherical lenses.

[0071] Among them, spherical lenses are characterized by a constant curvature from the center to the periphery, ensuring a simple lens setup. Because glass lenses have a low coefficient of thermal expansion, they offer good stability and can balance high and low temperatures. By setting both the fifth lens L5 and the sixth lens L6 as glass spherical lenses, the focal length of the fisheye lens remains stable even when the ambient temperature varies significantly.

[0072] Optionally, the Abbe number V5 of the fifth lens L5 and the Abbe number V6 of the sixth lens L6 satisfy: 30≤|v5-v6|≤40; the refractive index Nd5 of the fifth lens L5 satisfies: 1.55≤Nd5≤1.80; and the refractive index Nd6 of the sixth lens L6 satisfies: 1.45≤Nd6≤1.65.

[0073] This configuration, by ensuring that the Abbe number V5 of the fifth lens L5 and the Abbe number V6 of the sixth lens L6 meet the aforementioned value range, results in a large difference in Abbe number between the fifth lens L5 and the sixth lens L6. This allows the dispersion generated when light propagates through the fifth lens L5 and the sixth lens L6 to compensate for each other. Simultaneously, by ensuring that the refractive indices Nd5 of the fifth lens L5 and Nd6 of the sixth lens L6 meet the aforementioned value range, it is guaranteed that both the fifth lens L5 and the sixth lens L6 have large refractive indices, ensuring effective convergence or divergence of light, thereby improving image quality.

[0074] Based on the above embodiments, optionally, the combined focal length of the fifth lens L5 and the sixth lens L6 is F56, and the focal length of the fisheye lens is F; wherein, 3.5≤F56 / F≤5.

[0075] The combined focal length F56 of the fifth lens L5 and the sixth lens L6 can be understood as the total focal length of the cemented doublet lens formed by the fifth lens L5 and the sixth lens L6. Furthermore, since focal length is the reciprocal of optical power, the value of optical power can be indirectly determined by limiting the value of the focal length. Thus, by setting the combined focal length F56 of the fifth lens L5 and the sixth lens L6 to satisfy the above conditions, the surface chromatic aberrations of the fifth lens L5 and the sixth lens L6 can compensate for each other, thereby reducing chromatic aberration. Simultaneously, the remaining chromatic aberration is used to balance the chromatic aberration caused by other components of the fisheye lens, improving imaging performance.

[0076] Optionally, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the seventh lens L7, and the eighth lens L8 are all aspherical lenses.

[0077] The continuous curvature of an aspherical lens from its center to its periphery allows it to correct for focusing deviations in edge light rays caused by a fixed curvature, ensuring image sharpness. Simultaneously, optimized surface design helps reduce aberrations (such as distortion and chromatic aberration), increasing the aperture of the fisheye lens while maintaining high resolution. Furthermore, a single aspherical lens can replace multiple spherical lenses, reducing system complexity, weight, and size, thus facilitating the miniaturization of fisheye lenses.

[0078] Optionally, the seventh lens L7 is a plastic aspherical lens.

[0079] Optionally, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the eighth lens L8 are all glass aspherical lenses.

[0080] Glass lenses, with their low coefficient of thermal expansion and good stability, can balance high and low temperatures, helping to maintain focal length stability when the ambient temperature of the fisheye lens varies significantly. Plastic lenses, manufactured using injection molding, allow for mass production. While mold development costs are higher, the cost per unit is significantly reduced. Furthermore, plastic has a lower density, resulting in a weight that is only 1 / 4 to 1 / 5 that of a glass lens after processing, making it much lighter. Through a reasonable combination of plastic and glass lenses, the weight and cost of the fisheye lens are greatly reduced. The compensation from different materials also helps to balance the resolution of the fisheye lens under different ambient temperatures.

[0081] Optionally, the first lens L1 has negative optical power, the second lens L2 has negative optical power, the seventh lens L7 has negative optical power, and the eighth lens L8 has positive optical power.

[0082] Thus, by setting the optical power of the first lens L1 and the second lens L2 to negative values, it is beneficial to the large field of view of the fisheye lens; by setting the seventh lens L7 to have negative optical power and the eighth lens L8 to have positive optical power, the imaging quality can be improved while meeting the requirements of a large imaging target area.

[0083] Optionally, the optical power of the first lens group G1 is Z1, and the combined optical power of the first lens L1 and the second lens L2 is φ12; wherein, 0.85≤φ12 / Z1≤1.00.

[0084] Wherein, the optical power of the first lens group G1 is the overall optical power of the lens group consisting of the first lens L1, the second lens L2, and the third lens L3, and the combined optical power of the first lens L1 and the second lens L2 is the overall optical power of the first lens L1 and the second lens L2. By setting the combined optical power φ12 of the first lens L1 and the second lens L2 to satisfy the above conditions, it can be seen that the negative optical power of the first lens group G1 is contributed by the first lens L1 and the second lens L2, so that the light rays in the off-axis field of view can be incident on the third lens L3 at a smaller angle, which is beneficial to the large field of view of the fisheye lens, for example, the field of view is greater than 190°.

[0085] Based on the above embodiments, optionally, the optical power of the first lens group G1 is Z1, the optical power of the first lens L1 is φ1, and the optical power of the second lens L2 is φ2; wherein, 2.70≤φ1 / Z1≤3.40; 1.65≤φ2 / Z1≤2.00.

[0086] Among them, the optical power of the first lens L1 and the second lens L2 and the first lens group G1 satisfy the above conditions. It can be seen that the optical power of the first lens L1 and the second lens L2 are both negative values, and the optical power of the third lens L3 can be positive values. This allows the first lens L1 and the second lens L2 to cover the negative optical power of the first lens group G1, thereby ensuring that the light rays in the off-axis field of view can be incident on the third lens L3 at a smaller angle, which is beneficial to increasing the field of view of the fisheye lens.

[0087] Optionally, the optical power of the first lens L1 is φ1, the optical power of the third lens L3 is φ3, and the focal length of the fisheye lens is F; wherein, -10.3≤φ1 / F≤-9.0; -61.0≤φ3 / F≤-45.5.

[0088] Since optical power and focal length are reciprocals, φ1 / F can be equal to the product of the optical power φ1 of the first lens L1 and the overall optical power of the fisheye lens's optical system, and φ3 / F can be equal to the product of the optical power φ1 of the third lens L3 and the overall optical power of the fisheye lens's optical system. By ensuring that the optical powers of the first lens L1 and the third lens L3 satisfy the above conditions, it is possible to ensure that the light entering the third lens L3 has a small angle, guaranteeing that the light enters the third lens L3 smoothly.

[0089] Optionally, the optical power of the second lens group G2 is Z2, the optical power of the seventh lens L7 is φ7, and the optical power of the eighth lens L8 is φ8; wherein, -0.75≤φ7 / Z2≤-0.60; 0.9≤φ8 / Z2≤1.1.

[0090] Optionally, the optical power of the fourth lens L4 is φ4, the optical power of the seventh lens L7 is φ7, the optical power of the eighth lens L8 is φ8, and the focal length of the fisheye lens is F; where 5.65≤φ4 / F≤6.25; -3.0≤φ7 / F≤-2.4; -10.3≤φ8 / F≤4.

[0091] This embodiment, by rationally allocating the optical power of each lens in the second lens group G2, enables light to propagate smoothly in the second lens group G2, preventing the light from being more deflected at a certain plane grating and introducing greater aberrations, thereby improving the imaging sharpness of the fisheye lens.

[0092] Optionally, the refractive index Nd1 of the first lens L1 satisfies: 1.65 ≤ Nd1 ≤ 1.80. By appropriately setting the refractive index of the first lens L1, the fisheye lens can achieve a reasonable focal length. Furthermore, setting the refractive index of the first lens L1 also helps to reduce aberrations and improve image quality.

[0093] Optionally, the refractive index Nd5 of the fifth lens L5 satisfies: 1.55 ≤ Nd5 ≤ 1.80. By appropriately setting the refractive index of the fifth lens L5, the fisheye lens can achieve a reasonable focal length. Furthermore, setting the refractive index of the fifth lens L5 also helps to reduce aberrations and improve image quality.

[0094] Furthermore, based on the above embodiments, optionally, the fisheye lens may also include an aperture stop L9, which is disposed in the optical path between the fourth lens L4 and the fifth lens L5. By properly setting the position of the aperture stop L9, the coma generated by the entire optical system of the fisheye lens can be significantly reduced. At the same time, by properly setting the refractive index of the fifth lens L5, the aberrations generated by light passing through the aperture stop L9 can be reduced.

[0095] Optionally, the length from the object-side surface of the first lens L1 to the image-side surface of the third lens L3 on the first optical axis is TG1, and the effective optical aperture of the object-side surface of the first lens is D1; ​​wherein, 1.65≤TG1 / D1≤1.72. This configuration allows the shape and size of the first lens L1 to meet the characteristics of a fisheye lens, which is beneficial for achieving a large field of view in a fisheye lens.

[0096] Optionally, the length of the object-side surface of the first lens L1 to the image-side surface of the third lens L3 on the first optical axis is TG1, and the length of the object-side surface of the fourth lens L4 to the image-side surface of the eighth lens L8 on the first optical axis is TG2; wherein, -0.70≤TG2 / TG1≤-0.65.

[0097] In this context, the length TG1 from the object-side surface of the first lens L1 to the image-side surface of the third lens L3 on the first optical axis can be understood as the length of the first lens group G1 on the first optical axis; similarly, the length TG2 from the object-side surface of the fourth lens L4 to the image-side surface of the eighth lens L8 on the first optical axis can be understood as the length of the second lens group G2 on the first optical axis. Since the fourth lens L4 to the eighth lens L8 are arranged sequentially along the second optical axis, and the first and second optical axes intersect, the thickness of all four lenses on the first optical axis is negative, meaning the length TG2 from the object-side surface of the fourth lens L4 to the image-side surface of the eighth lens L8 on the first optical axis is negative. By limiting the ratio of the lengths of the first lens group G1 to the second lens group G2 on the first optical axis to meet the above conditions, the fisheye lens structure can be made more compact, and a reasonable installation space is provided for the plane mirror between the third lens L3 and the fourth lens L4, facilitating the assembly of each lens and mirror and reducing assembly costs.

[0098] Optionally, the image plane diameter of the fisheye lens is ID1, and the length from the object-side surface of the fourth lens L4 to the image-side surface of the eighth lens L8 on the first optical axis is TG2; where -0.57≤ID1 / TG2≤-0.54. This setting ensures that the fisheye lens is small in size while accommodating a larger imaging field, achieving the goal of small size while adapting to large target surface chips.

[0099] Based on the above embodiments, the fisheye lens also includes a filter glass L10 located on the image side of the eighth lens L8. This filter glass L10 can reduce the interference of external light on the image by reflecting or absorbing light of specific wavelengths, eliminating problems such as halos and color shifts, and ensuring image clarity. At the same time, the filter glass can also serve as a physical protective layer on the surface of the fisheye lens, preventing dust, water stains, and other foreign objects from directly contacting the lenses in the fisheye lens, reducing the risk of scratches and coating damage.

[0100] In summary, this embodiment of the utility model uses a fisheye lens structure composed of eight lenses with optical power. By rationally setting the arrangement, material, surface shape, and optical power of each lens, the fisheye lens has a large imaging target surface, meeting the requirements of a large aperture. At the same time, it has the advantages of compact structure and small size, making the fisheye lens suitable for more application scenarios.

[0101] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the fisheye lens applicable to the above-described embodiments.

[0102] In one feasible embodiment, Table 1 details a feasible implementation method. Figure 1 The specific optical physical parameters of the fisheye lens are shown.

[0103] Table 1. Design of optical physical parameters for a fisheye lens.

[0104]

[0105] Table 2 shows the design parameters of each lens in a fisheye lens, including surface type, radius of curvature, thickness, and material, corresponding to those in Table 1.

[0106] Table 2. One parameter design for each lens in a fisheye lens.

[0107]

[0108] The fisheye lens of this embodiment includes a first lens group G1, a plane mirror G3, and a second lens group G2 arranged sequentially along the optical axis from the object side to the image side. The first lens group G1 includes a first lens group G2 arranged sequentially along the first optical axis.

[0109] The first lens L1, the second lens L2, and the third lens L3, and the second lens group G2 includes the fourth lens L4, the aperture L9, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the filter glass L10 arranged sequentially along the second optical axis. The surface numbers are assigned according to the order of the lenses' surfaces. "S1" represents the object-side surface of the first lens L1, "S2" represents the image-side surface of the first lens L1, and so on. "S8" represents the reflecting surface of the plane mirror, "OBJ" represents the object surface of the fisheye lens, "STO" represents the aperture stop, and "IMG" represents the imaging surface of the fisheye lens. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image surface, and a negative value indicates that the surface bends towards the object surface. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the axial distance between the current surface and the next surface. The refractive index represents the ability of the material between the current surface and the next surface to deflect light; a blank space indicates 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; a blank space indicates that the current position is air. In this embodiment, the fisheye lens has a focal length f of 1.337 mm, an aperture number F# of 1.541, a field of view of 200°, and an image diameter of 4.6 mm.

[0110] Based on the above embodiments, the fourth lens L4, the seventh lens L7, and the eighth lens L8 are all aspherical lenses. In this case, the aspherical surface shape equation Z of the fourth lens L4, the seventh lens L7, and the eighth lens L8 satisfies:

[0111]

[0112] Where Z is the aspherical elevation, c is the fundamental curvature at the vertex, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and a i a is the coefficient of the higher-order term. i r 2i For the higher-order term of the aspherical surface, the value of i is 2, 3, 4, 5, 6, 7, 8.

[0113] Table 3 Aspheric coefficients in fisheye lenses

[0114]

[0115] Where -3.825425E-04 indicates that the coefficient a2 of surface number S10 is -3.825425 × 10 -4 And so on.

[0116] Furthermore, Figure 2 yes Figure 1 The diagram showing the vertical chromatic aberration of the fisheye lens is as follows: Figure 2As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 555.00 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 2 It can be seen that the chromatic aberration of the vertical axis at different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm) is controlled within a reasonable range, indicating that the chromatic aberration of the fisheye lens is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0117] Figure 3 yes Figure 1 The diagram shown illustrates the ray fan of a fisheye lens. Ray fan diagrams are one of the most commonly used evaluation methods in modern optical design. For example... Figure 3 As shown, the horizontal axis of the ray fan plot represents the normalized pupil aperture, and the vertical axis represents the distance of the corresponding ray from the principal ray on the image plane. It's important to note that the principal ray passes through the center of the entrance pupil. Ideally, all curves perfectly coincide with the horizontal axis, meaning all rays in that field of view converge at the same point on the image plane. Figure 3 As shown, the light fan plots of all fields of view at different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm) are all close to the horizontal axis, and the curves of each color have a high degree of concentration. This indicates that the aberrations of each field of view of the fisheye lens are well corrected, which can ensure that the fisheye lens can form clear images in a wide spectral range.

[0118] Figure 4 yes Figure 1 The diagram shown illustrates the field curvature distortion of a fisheye lens, as follows: Figure 4 As shown, there are two coordinate systems. In the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit. Here, T represents the meridion and S represents the sagitta. Figure 4 As can be seen from the left coordinate system, the field curvature of the fisheye lens in this embodiment is effectively controlled for different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm), ensuring that the difference between the central and peripheral image quality is small during imaging. In the right coordinate system, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 4 As can be seen from the coordinate system on the right, the distortion of the fisheye lens in this embodiment has been effectively controlled.

[0119] Figure 5 yes Figure 1 The diagram shows the MTF curve of a fisheye lens. The MTF curve is one of the most commonly used and authoritative evaluation methods in modern optical design. For example... Figure 5As shown, the horizontal axis represents the spatial frequency distribution of line pairs in object space imaged onto the image plane by the optical system, in periods / mm, and the vertical axis represents the magnitude of the optical transfer function. The graph shows the trend of the optical transfer function along the meridional and sagittal (TS) directions corresponding to different fields of view (0.00°, 29.24°, 48.92°, 58.89°, 68.98°, 79.23°, 89.60°, and 100.00° as shown in the figure), with increasing spatial frequency. The ideal curve is a straight line coinciding with the system's diffraction limit, indicating that the geometric aberrations of the light rays at all positions are less than the wave phase difference caused by the physical limitations of the system itself, and can be ignored. Figure 5 It can be seen that in the MTF curves of the fisheye lens at different focal lengths in the visible light band of 436nm to 660nm, when the spatial frequency reaches 250lp / mm, the MTF of the entire field of view is greater than 0.3, indicating good imaging quality.

[0120] In another feasible embodiment, Figure 6 This is a schematic diagram of another fisheye lens provided by this utility model at the optimal object distance. Table 4 details another feasible implementation method. Figure 6 The specific optical physical parameters of the fisheye lens are shown.

[0121] Table 4. Another design of optical physical parameters for fisheye lenses.

[0122]

[0123] Table 5 shows the design parameters of each lens in another type of fisheye lens, corresponding to Table 4, including surface type, radius of curvature, thickness, and material.

[0124] Table 5. Another parameter design for each lens in a fisheye lens.

[0125]

[0126] The fisheye lens of this embodiment includes a first lens group G1, a plane mirror G3, and a second lens group G2 arranged sequentially along the optical axis from the object side to the image side. The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3 arranged sequentially along the first optical axis. The second lens group G2 includes a fourth lens L4, an aperture L9, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter glass L10 arranged sequentially along the second optical axis. The surface numbering is based on the order of the lenses' surfaces. "S1" represents the object-side surface of the first lens L1, "S2" represents the image-side surface of the first lens L1, and so on. "S8" represents the reflecting surface of the plane mirror, "OBJ" represents the object surface of the fisheye lens, "STO" represents the aperture stop, and "IMG" represents the imaging surface of the fisheye lens. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates the surface bends towards the image surface, and a negative value indicates the surface bends towards the object surface. "Infinite" indicates the surface is flat with an infinite radius of curvature. The thickness represents the axial distance between the current surface and the next surface. The refractive index represents the ability of the material between the current and next surfaces to deflect light; a blank space indicates the current location is air with a refractive index of 1. The Abbe number represents the dispersion characteristics of the material between the current and next surfaces; a blank space indicates the current location is air. In this embodiment, the fisheye lens has a focal length f of 1.397mm, an aperture number F# of 1.548, a field of view of 200°, and an image diameter of 4.6mm.

[0127] Based on the above embodiments, the fourth lens L4, the seventh lens L7, and the eighth lens L8 are all aspherical lenses. In this case, the aspherical surface shape equation Z of the fourth lens L4, the seventh lens L7, and the eighth lens L8 satisfies:

[0128]

[0129] Where Z is the aspherical elevation, c is the fundamental curvature at the vertex, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and a i a is the coefficient of the higher-order term. i r 2i For the higher-order term of the aspherical surface, the value of i is 2, 3, 4, 5, 6, 7, 8.

[0130] Table 6 Aspheric coefficients in fisheye lenses

[0131]

[0132] Where -4.878253E-04 indicates that the coefficient a2 of surface number S10 is -4.878253 × 10 -4 And so on.

[0133] Furthermore, Figure 7 yes Figure 6 The diagram showing the vertical chromatic aberration of the fisheye lens is as follows: Figure 7 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 555.00 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 7 It can be seen that the chromatic aberration of the vertical axis at different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm) is controlled within a reasonable range, indicating that the chromatic aberration of the fisheye lens is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0134] Figure 8 yes Figure 6 The diagram shown illustrates the ray fan of a fisheye lens. Ray fan diagrams are one of the most commonly used evaluation methods in modern optical design. For example... Figure 8 As shown, the horizontal axis of the ray fan plot represents the normalized pupil aperture, and the vertical axis represents the distance of the corresponding ray from the principal ray on the image plane. It's important to note that the principal ray passes through the center of the entrance pupil. Ideally, all curves perfectly coincide with the horizontal axis, meaning all rays in that field of view converge at the same point on the image plane. Figure 8 As shown, the light fan plots of all fields of view at different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm) are all close to the horizontal axis, and the curves of each color have a high degree of concentration. This indicates that the aberrations of each field of view of the fisheye lens are well corrected, which can ensure that the fisheye lens can form clear images in a wide spectral range.

[0135] Figure 9 yes Figure 6 The diagram shown illustrates the field curvature distortion of a fisheye lens, as follows: Figure 9 As shown, there are two coordinate systems. In the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit. Here, T represents the meridion and S represents the sagitta. Figure 9 As can be seen from the left coordinate system, the field curvature of the fisheye lens in this embodiment is effectively controlled for different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm), ensuring that the difference between the central and peripheral image quality is small during imaging. In the right coordinate system, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 9 As can be seen from the coordinate system on the right, the distortion of the fisheye lens in this embodiment has been effectively controlled.

[0136] Figure 10 yes Figure 6The diagram shows the MTF curve of a fisheye lens. The MTF curve is one of the most commonly used and authoritative evaluation methods in modern optical design. For example... Figure 10 As shown, the horizontal axis represents the spatial frequency distribution of line pairs in object space imaged onto the image plane by the optical system, in periods / mm, and the vertical axis represents the magnitude of the optical transfer function. The graph shows the trend of the optical transfer function along the meridional and sagittal (TS) directions corresponding to different fields of view (0.00°, 29.24°, 48.92°, 58.89°, 68.98°, 79.23°, 89.60°, and 100.00° as shown in the figure), with increasing spatial frequency. The ideal curve is a straight line coinciding with the system's diffraction limit, indicating that the geometric aberrations of the light rays at all positions are less than the wave phase difference caused by the physical limitations of the system itself, and can be ignored. Figure 10 It can be seen that in the MTF curves of the fisheye lens at different focal lengths in the visible light band of 436nm to 660nm, when the spatial frequency reaches 250lp / mm, the MTF of the entire field of view is greater than 0.3, indicating good imaging quality.

[0137] In yet another feasible embodiment, Figure 11 This is a schematic diagram of another fisheye lens provided by this utility model at the optimal object distance. Table 7 details another feasible implementation method. Figure 11 The specific optical physical parameters of the fisheye lens are shown.

[0138] Table 7. Another type of optical physical parameter design for fisheye lenses.

[0139]

[0140] Table 8 shows the design parameters for the surface type, radius of curvature, thickness, and material of each lens in another type of fisheye lens, corresponding to Table 7.

[0141] Table 8. Another parameter design for each lens in a fisheye lens.

[0142]

[0143] The fisheye lens of this embodiment includes a first lens group G1, a plane mirror G3, and a second lens group G2 arranged sequentially along the optical axis from the object side to the image side. The first lens group G1 includes a first lens L1, a second lens L2, and a third lens L3 arranged sequentially along the first optical axis. The second lens group G2 includes a fourth lens L4, an aperture L9, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter glass L10 arranged sequentially along the second optical axis. The surface numbering is based on the order of the lenses' surfaces. "S1" represents the object-side surface of the first lens L1, "S2" represents the image-side surface of the first lens L1, and so on. "S8" represents the reflecting surface of the plane mirror, "OBJ" represents the object surface of the fisheye lens, "STO" represents the aperture stop, and "IMG" represents the imaging surface of the fisheye lens. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates the surface bends towards the image surface, and a negative value indicates the surface bends towards the object surface. "Infinite" indicates the surface is flat with an infinite radius of curvature. The thickness represents the axial distance between the current surface and the next surface. The refractive index represents the ability of the material between the current and next surfaces to deflect light; a blank space indicates the current location is air with a refractive index of 1. The Abbe number represents the dispersion characteristics of the material between the current and next surfaces; a blank space indicates the current location is air. In this embodiment, the fisheye lens has a focal length f of 1.397mm, an aperture number F# of 1.548, a field of view of 200°, and an image diameter of 4.6mm.

[0144] Based on the above embodiments, the fourth lens L4, the seventh lens L7, and the eighth lens L8 are all aspherical lenses. In this case, the aspherical surface shape equation Z of the fourth lens L4, the seventh lens L7, and the eighth lens L8 satisfies:

[0145]

[0146] Where Z is the aspherical elevation, c is the fundamental curvature at the vertex, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and a i a is the coefficient of the higher-order term. i r 2i For the higher-order term of the aspherical surface, the value of i is 2, 3, 4, 5, 6, 7, 8.

[0147] Table 9 Aspheric coefficients in fisheye lenses

[0148]

[0149] Where -3.618369E-04 indicates that the coefficient a2 of surface number S10 is -3.618369 × 10 -4 And so on.

[0150] Furthermore, Figure 12 yes Figure 11 The diagram showing the vertical chromatic aberration of the fisheye lens is as follows: Figure 12 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 555.00 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 12 It can be seen that the chromatic aberration of the vertical axis at different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm) is controlled within a reasonable range, indicating that the chromatic aberration of the fisheye lens is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0151] Figure 13 yes Figure 11 The diagram shown illustrates the ray fan of a fisheye lens. Ray fan diagrams are one of the most commonly used evaluation methods in modern optical design. For example... Figure 13 As shown, the horizontal axis of the ray fan plot represents the normalized pupil aperture, and the vertical axis represents the distance of the corresponding ray from the principal ray on the image plane. It's important to note that the principal ray passes through the center of the entrance pupil. Ideally, all curves perfectly coincide with the horizontal axis, meaning all rays in that field of view converge at the same point on the image plane. Figure 13 As shown, the light fan plots of all fields of view at different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm) are all close to the horizontal axis, and the curves of each color have a high degree of concentration. This indicates that the aberrations of each field of view of the fisheye lens are well corrected, which can ensure that the fisheye lens can form clear images in a wide spectral range.

[0152] Figure 14 yes Figure 11 The diagram shown illustrates the field curvature distortion of a fisheye lens, as follows: Figure 14 As shown, there are two coordinate systems. In the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit. Here, T represents the meridion and S represents the sagitta. Figure 14 As can be seen from the left coordinate system, the field curvature of the fisheye lens in this embodiment is effectively controlled for different wavelengths (436nm, 470nm, 510nm, 550nm, 610nm, 650nm), ensuring that the difference between the central and peripheral image quality is small during imaging. In the right coordinate system, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 14 As can be seen from the coordinate system on the right, the distortion of the fisheye lens in this embodiment has been effectively controlled.

[0153] Figure 15 yes Figure 11The diagram shows the MTF curve of a fisheye lens. The MTF curve is one of the most commonly used and authoritative evaluation methods in modern optical design. For example... Figure 15 As shown, the horizontal axis represents the spatial frequency distribution of line pairs in object space imaged onto the image plane by the optical system, in periods / mm, and the vertical axis represents the magnitude of the optical transfer function. The graph shows the trend of the optical transfer function along the meridional and sagittal (TS) directions corresponding to different fields of view (0.00°, 29.24°, 48.92°, 58.89°, 68.98°, 79.23°, 89.60°, and 100.00° as shown in the figure), with increasing spatial frequency. The ideal curve is a straight line coinciding with the system's diffraction limit, indicating that the geometric aberrations of the light rays at all positions are less than the wave phase difference caused by the physical limitations of the system itself, and can be ignored. Figure 15 It can be seen that in the MTF curves of the fisheye lens at different focal lengths in the visible light band of 436nm to 660nm, when the spatial frequency reaches 250lp / mm, the MTF of the entire field of view is greater than 0.3, indicating good imaging quality.

[0154] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fisheye lens, characterized in that, include: The first lens group, the plane mirror, and the second lens group are arranged sequentially from the object side to the image side; The first lens group has negative optical power; the first lens group includes a first lens, a second lens, and a third lens arranged along a first optical axis from the object side to the image side; The second lens group has positive optical power; the second lens group includes a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged along the second optical axis from the object side to the image side; The first optical axis intersects with the second optical axis.

2. The fisheye lens according to claim 1, characterized in that, The angle between the first optical axis and the second optical axis is 90°.

3. The fisheye lens according to claim 1, characterized in that, The angle between the reflecting surface of the plane mirror and the first optical axis is θ1; the angle between the reflecting surface of the plane mirror and the second optical axis is θ2; where θ1 = θ2.

4. The fisheye lens according to claim 1, characterized in that, The fifth lens and the sixth lens constitute a cemented doublet lens.

5. The fisheye lens according to claim 1, characterized in that, The fifth lens and the sixth lens are glass spherical lenses.

6. The fisheye lens according to claim 1, characterized in that, The Abbe number V5 of the fifth lens and the Abbe number V6 of the sixth lens satisfy: 30≤|v5-v6|≤40; The refractive index Nd5 of the fifth lens satisfies: 1.55≤Nd5≤1.80; The refractive index Nd6 of the sixth lens satisfies: 1.45≤Nd6≤1.

65.

7. The fisheye lens according to claim 1, characterized in that, The combined focal length of the fifth lens and the sixth lens is F56, and the focal length of the fisheye lens is F; Among them, 3.5≤F56 / F≤5.

8. The fisheye lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, the fourth lens, the seventh lens, and the eighth lens are all aspherical lenses.

9. The fisheye lens according to claim 7, characterized in that, The seventh lens is a plastic aspherical lens.

10. The fisheye lens according to claim 7, characterized in that, The first lens, the second lens, the third lens, the fourth lens, and the eighth lens are all glass aspherical lenses.

11. The fisheye lens according to claim 1, characterized in that, The first lens has negative optical power, the second lens has negative optical power, the seventh lens has negative optical power, and the eighth lens has positive optical power.

12. The fisheye lens according to claim 1, characterized in that, The optical power of the first lens group is Z1, and the combined optical power of the first lens and the second lens is φ12. Wherein, 0.85≤φ12 / Z1≤1.

00.

13. The fisheye lens according to claim 1, characterized in that, The optical power of the first lens group is Z1, the optical power of the first lens is φ1, and the optical power of the second lens is φ2; Among them, 2.70≤φ1 / Z1≤3.40; 1.65≤φ2 / Z1≤2.

00.

14. The fisheye lens according to claim 1, characterized in that, The first lens has an optical power of φ1, the third lens has an optical power of φ3, and the fisheye lens has a focal length of F. Among them, -10.3≤φ1 / F≤-9.0; -61.0≤φ3 / F≤-45.

5.

15. The fisheye lens according to claim 1, characterized in that, The optical power of the second lens group is Z2, the optical power of the seventh lens is φ7, and the optical power of the eighth lens is φ8; Among them, -0.75≤φ7 / Z2≤-0.60; 0.9≤φ8 / Z2≤1.

1.

16. The fisheye lens according to claim 1, characterized in that, The fourth lens has an optical power of φ4, the seventh lens has an optical power of φ7, the eighth lens has an optical power of φ8, and the fisheye lens has a focal length of F. Among them, 5.65≤φ4 / F≤6.25; -3.0≤φ7 / F≤-2.4; -10.3≤φ8 / F≤4.

17. The fisheye lens according to claim 1, characterized in that, The refractive index Nd1 of the first lens satisfies: 1.65≤Nd1≤1.

80.

18. The fisheye lens according to claim 1, characterized in that, The refractive index Nd5 of the fifth lens satisfies: 1.55≤Nd5≤1.

80.

19. The fisheye lens according to claim 1, characterized in that, The length of the object-side surface of the first lens to the image-side surface of the third lens on the first optical axis is TG1, and the effective optical aperture of the object-side surface of the first lens is D1. Among them, 1.65≤TG1 / D1≤1.

72.

20. The fisheye lens according to claim 1, characterized in that, The length of the object-side surface of the first lens to the image-side surface of the third lens on the first optical axis is TG1, and the length of the object-side surface of the fourth lens to the image-side surface of the eighth lens on the first optical axis is TG2. Wherein, -0.70≤TG2 / TG1≤-0.

65.

21. The fisheye lens according to claim 1, characterized in that, The image plane diameter of the fisheye lens is ID1, and the length of the object-side surface of the fourth lens to the image-side surface of the eighth lens on the first optical axis is TG2. Where -0.57≤ID1 / TG2≤-0.54.

Images