Fisheye lens

Abstract

The invention discloses a fisheye lens. The fisheye lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from an object side to an image side, the first lens has negative focal power, the second lens has negative focal power, the third lens has focal power, the fourth lens has positive focal power, the fifth lens has positive focal power, the sixth lens has negative focal power, the seventh lens has positive focal power, and the eighth lens has negative focal power. The maximum field angle of the fisheye lens is DFOV, the image height under the maximum field angle of the fisheye lens is H, and the total focal length of the fisheye lens is f; wherein DFOV / H / f is more than or equal to 14.027 and less than or equal to 19.708. The fisheye lens has the advantages of being large in field angle, large in aperture, large in imaging target surface and small in size.

Description

Technical Field

[0001] The present invention 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, fisheye lenses have large distortion and cannot meet the dual requirements of a large field of view and a large imaging target surface, which makes fisheye lenses unsuitable for more types of chips and limits their application scenarios. Summary of the Invention

[0004] This invention provides a fisheye lens that, while having a large imaging target surface and a wide field of view, ensures that the fisheye lens has a small size, thus enabling the fisheye lens to be used in more scenarios.

[0005] The present invention provides a fisheye lens, which includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially from the object side to the image side;

[0006] The first lens has negative optical power, the second lens has negative optical power, the third lens has optical power, the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, the seventh lens has positive optical power, and the eighth lens has negative optical power.

[0007] The maximum field of view of the fisheye lens is DFOV, the image height below the maximum field of view of the fisheye lens is H, and the total focal length of the fisheye lens is f; wherein, 14.027≤DFOV / H / f≤19.708.

[0008] Optionally, the first lens and the second lens are spherical lenses; the third lens to the eighth lens are aspherical lenses.

[0009] Optionally, the first and second lenses are glass lenses; the third to eighth lenses are plastic lenses.

[0010] Optionally, the object-side surface of the first lens is convex, and the image-side surface is concave.

[0011] The object-side surface of the second lens is convex, and the image-side surface is concave.

[0012] The object-side surface of the third lens is concave, and the image-side surface is convex.

[0013] Both the object-side and image-side surfaces of the fourth lens are convex.

[0014] Both the object-side and image-side surfaces of the fifth lens are convex.

[0015] Both the object-side and image-side surfaces of the sixth lens are concave.

[0016] The object-side and image-side surfaces of the seventh lens are both convex.

[0017] Optionally, the optical power φ1 of the first lens, the optical power φ2 of the second lens, and the total optical power φ of the fisheye lens satisfy the following:

[0018] -6.53≤φ1 / φ≤-4.807;

[0019] -3.43≤φ2 / φ≤-2.516.

[0020] Optionally, the optical power φ5 of the fifth lens, the optical power φ6 of the sixth lens, and the total optical power φ of the fisheye lens satisfy the following:

[0021] -0.281≤(φ5+φ6) / φ≤-0.249.

[0022] Optionally, the Abbe number Vd2 and refractive index Nd2 of the second lens satisfy:

[0023] 55.9 <Vd2<80.5;

[0024] 1.54 <Nd2<1.7。

[0025] Optionally, the object-side curvature R21 and image-side curvature R22 of the second lens satisfy:

[0026] 4.966 <R21 / R22<7.53。

[0027] Optionally, the distance TTL from the object-side surface of the first lens to the image plane of the fisheye lens, the maximum effective radius D1 of the object-side surface of the first lens, and the image height Hmax of the fisheye lens at the maximum field of view satisfy:

[0028] 0.143 <TTL / (D1*Hmax)<0.192。

[0029] Optionally, the center thickness CT5 of the fifth lens, the center thickness CT6 of the sixth lens, the center thickness CT7 of the seventh lens, and the center thickness CT8 of the eighth lens satisfy the following:

[0030] 3mm<(CT5+CT6+CT7+CT8)<5mm.

[0031] Optionally, the fisheye lens further includes an aperture stop located in the optical path between the fourth lens and the fifth lens.

[0032] Optionally, the maximum effective radius D1 of the object-side surface of the first lens, the effective radius ST of the aperture, and the maximum effective radius D8 of the object-side surface of the eighth lens satisfy the following:

[0033] 3.39 < (D1 / ST) / (D8 / ST) < 3.469.

[0034] The technical solution of this invention employs a fisheye lens composed of eight lenses with optical power. By rationally setting the optical power of each lens, and simultaneously setting the maximum field of view (DFOV), the image height (H) at the maximum field of view, and the total focal length (f) of the fisheye lens to satisfy 14.027 ≤ DFOV / H / f ≤ 19.708, the fisheye lens can meet the requirements of low distortion and a large imaging target area while having a large field of view. This results in the fisheye lens having high imaging quality and being applicable to more types of chips, making it suitable for a wider range of application scenarios. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a fisheye lens provided in an embodiment of the present invention;

[0036] Figure 2 yes Figure 1 The diagram shows the beam pattern of the fisheye lens.

[0037] Figure 3 yes Figure 1 A schematic diagram of the spherical aberration curve of a fisheye lens is shown.

[0038] Figure 4 yes Figure 1 The diagram shows the chromatic aberration curve of a fisheye lens;

[0039] Figure 5 This is a schematic diagram of another fisheye lens provided in an embodiment of the present invention;

[0040] Figure 6 yes Figure 5 The diagram shows the beam pattern of the fisheye lens.

[0041] Figure 7 yes Figure 5 A schematic diagram of the spherical aberration curve of a fisheye lens is shown.

[0042] Figure 8 yes Figure 5 The diagram shows the chromatic aberration curve of a fisheye lens;

[0043] Figure 9 This is a schematic diagram of another fisheye lens provided in an embodiment of the present invention;

[0044] Figure 10 yes Figure 9 The diagram shows the beam pattern of the fisheye lens.

[0045] Figure 11 yes Figure 9 A schematic diagram of the spherical aberration curve of a fisheye lens is shown.

[0046] Figure 12 yes Figure 9 The diagram shows the chromatic aberration curve of a fisheye lens. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be fully described below with reference to the accompanying drawings of the embodiments of this invention through specific implementation methods. Obviously, the described embodiments are only some, not all, embodiments of this invention. Various modifications and variations can be made to this invention without departing from the spirit or scope of this invention, which will be obvious to those skilled in the art. Therefore, this invention is intended to cover modifications and variations of this invention that fall within the scope of the corresponding claims (the claimed technical solutions) and their equivalents.

[0048] 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.

[0049] It should be noted that the implementation methods provided in the embodiments of the present invention can be combined with each other without contradiction.

[0050] Figure 1 This is a schematic diagram of the structure 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 L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 arranged sequentially from the object side to the image side. The first lens L1 has negative optical power, the second lens L2 has negative optical power, the third lens L3 has positive optical power, the fourth lens L4 has positive optical power, the fifth lens L5 has positive optical power, the sixth lens L6 has negative optical power, the seventh lens L7 has positive optical power, and the eighth lens L8 has negative optical power. The maximum field of view of the fisheye lens is DFOV, the image height at the maximum field of view is H, and the total focal length is f. Wherein, 14.027 ≤ DFOV / H / f ≤ 19.708.

[0051] 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).

[0052] In this embodiment, the fisheye lens consists of eight lenses, from the first lens L1 to the eighth lens L8, each with optical power. By setting both the first lens L1 and the second lens L2 to have negative optical power, light rays with a large incident angle can enter the fisheye lens and propagate smoothly to the third lens L3, thereby giving the fisheye lens a large field of view. Simultaneously, by setting the third lens L3 to have positive optical power, the fourth lens L4 to have positive optical power, the fifth lens L5 to have positive optical power, the sixth lens L6 to have negative optical power, the seventh lens L7 to have positive optical power, and the eighth lens L8 to have negative optical power, the lenses work together to ensure that the fisheye lens meets the requirements of low distortion, low chromatic aberration, and high resolution.

[0053] Meanwhile, by setting the maximum field of view (DFOV) of the fisheye lens, the image height below the maximum field of view (H) of the fisheye lens, and the total focal length (f) of the fisheye lens to satisfy 14.027≤DFOV / H / f≤19.708, the fisheye lens can meet the requirements of a large imaging target surface while having a large field of view. This allows the fisheye lens to be used with more types of chips, and thus to be applicable to more application scenarios.

[0054] Optionally, the first lens L1 and the second lens L2 are spherical lenses; the third lens L3 to the eighth lens L8 are aspherical lenses.

[0055] Spherical lenses are characterized by a constant curvature from the center to the periphery, ensuring a simple lens setup. Aspherical lenses, on the other hand, exhibit a continuous change in curvature from the center to the periphery, allowing them to correct for edge light focusing deviations caused by a fixed curvature, thus ensuring image sharpness. Furthermore, optimized surface design helps reduce aberrations (such as distortion and chromatic aberration), increasing the aperture of the fisheye lens while maintaining high resolution. In addition, a single aspherical lens can replace multiple spherical lenses, reducing system complexity. Therefore, by setting the first lens L1 and the second lens L2 as spherical lenses, and the third to eighth lenses L8 as aspherical lenses, the weight and size of the fisheye lens can be reduced while simplifying the structure and miniaturizing chromatic aberration, thus facilitating its miniaturization.

[0056] Optionally, the first lens L1 and the second lens L2 are glass lenses; the third lens L3 to the eighth lens L8 are plastic lenses.

[0057] Among these, glass lenses have a low coefficient of thermal expansion and good stability, allowing them to balance high and low temperatures. Plastic lenses are significantly less expensive than glass lenses. By using glass lenses for the first lens L1 and the second lens L2, and plastic lenses for the third to eighth lenses L8, the two materials compensate for each other, balancing high and low temperatures. This gives the fisheye lens stable performance at both high and low temperatures, improving its environmental adaptability and reducing its cost.

[0058] 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; both the object-side and image-side surfaces of the fourth lens L4 are convex; both the object-side and image-side surfaces of the fifth lens L5 are convex; both the object-side and image-side surfaces of the sixth lens L6 are concave; and both the object-side and image-side surfaces of the seventh lens L7 are convex.

[0059] 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.

[0060] 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 field of view and a large imaging target surface.

[0061] Optionally, the optical power φ1 of the first lens L1, the optical power φ2 of the second lens L2, and the total optical power φ of the fisheye lens satisfy the following conditions: -6.53 ≤ φ1 / φ ≤ -4.807; -3.43 ≤ φ2 / φ ≤ -2.516. With this configuration, ensuring that both the first lens L1 and the second lens L2 have negative optical powers, the fisheye lens achieves a reverse telephoto objective lens structure by appropriately setting the optical powers of the first lens L1 and the second lens L2, thus satisfying the wide-angle characteristics of the fisheye lens.

[0062] Optionally, the optical power φ5 of the fifth lens L5, the optical power φ6 of the sixth lens L6, and the total optical power φ of the fisheye lens satisfy: -0.281≤(φ5+φ6) / φ≤-0.249.

[0063] Among them, the fifth lens L5 has positive optical power and the sixth lens L6 has negative optical power. The combination of positive and negative lenses of the fifth lens L5 and the sixth lens L6 can compensate for the chromatic aberration introduced at the front end, so that the fisheye lens has a better achromatic aberration effect.

[0064] Optionally, the Abbe number Vd2 and refractive index Nd2 of the second lens L2 satisfy: 55.9 <Vd2<80.5;1.54<Nd2<1.7。

[0065] Specifically, by ensuring that the second lens L2 meets the aforementioned range of Abbe number Vd2 and refractive index Nd2, the second lens L2 has a high Abbe number and a high refractive index, thereby enabling the second lens L2 to receive incident light at large angles, and thus greatly playing the role of achromatic correction and field curvature correction.

[0066] Optionally, the object-side curvature R21 and the image-side curvature R22 of the second lens L2 satisfy: 4.966 < R21 / R22 < 7.53. With such a setting, it is beneficial to eliminate the system chromatic aberration of the optical system in the fish-eye lens, correct the field curvature, and improve the imaging quality of the fish-eye lens.

[0067] Optionally, the distance TTL from the object side surface of the first lens L1 to the image surface of the fish-eye lens, the maximum effective radius D1 of the object side surface of the first lens L1, and the image height Hmax of the fish-eye lens at the maximum field angle satisfy: 0.143 < TTL / (D1*Hmax) < 0.192.

[0068] Among them, the distance TTL from the object side surface of the first lens L1 to the image surface of the fish-eye lens can be understood as the size of the optical system of the fish-eye lens. By limiting that the size TTL of the optical system of the fish-eye lens, the maximum effective radius D1 of the object side surface of the first lens L1, and the image height Hmax of the fish-eye lens at the maximum field angle satisfy the above relationship, it is ensured that the optical system of the fish-eye lens meets the requirements of miniaturization, the structure of the fish-eye lens is compact, which is convenient for processing and installation, thereby improving the imaging effect of the device equipped with the optical system of the fish-eye lens.

[0069] Optionally, the central thickness CT5 of the fifth lens L5, the central thickness CT6 of the sixth lens L6, the central thickness CT7 of the seventh lens L7, and the central thickness CT8 of the eighth lens L8 satisfy: 3mm < (CT5 + CT6 + CT7 + CT8) < 5mm.

[0070] Among them, by limiting the value range of the sum of the central thicknesses of the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8, it is ensured that the fish-eye lens has a small size, so as to ensure the miniaturization of the fish-eye lens.

[0071] Optionally, the fish-eye lens further includes: an aperture STO located in the optical path between the fourth lens L4 and the fifth lens L5.

[0072] Among them, by setting the aperture STO between the fourth lens L4 and the fifth lens L5 and setting the aperture STO at the central position of each lens, on the premise of being able to adjust the propagation direction of the light beam, it is beneficial to balance the distortion of the fish-eye lens at a large field angle and is beneficial to improving the imaging quality.

[0073] Optionally, the maximum effective radius D1 of the object side of the first lens L1, the effective radius ST of the aperture STO, and the maximum effective radius D8 of the object side of the eighth lens L8 satisfy: 3.39 < (D1 / ST) / (D8 / ST) < 3.469. By setting the maximum effective radius D1 of the object side of the first lens L1, the effective radius ST of the aperture STO, and the maximum effective radius D8 of the image side of the eighth lens L8 to satisfy the above conditions, the structural surface shape of each lens in the fisheye lens can be controlled, which is beneficial to the stability of the fisheye lens.

[0074] In summary, the embodiments of the present invention, by using eight lenses with optical power to form a fisheye lens structure, and by rationally setting the optical power, material, surface shape, etc. of each lens, enable the fisheye lens to have a large field of view, a large imaging target surface, and low distortion. At the same time, it has the advantages of compact structure and small volume, making the fisheye lens suitable for more application scenarios.

[0075] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the fisheye lens applicable to the above-described embodiments.

[0076] In one feasible embodiment, Table 1 details a feasible implementation method. Figure 1 The specific optical physical parameters of the fisheye lens are shown.

[0077] Table 1. Design of optical physical parameters for a fisheye lens

[0078]

[0079] 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.

[0080] Table 2. Parameter design of each lens in a fisheye lens

[0081]

[0082] The fisheye lens of this embodiment includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture stop STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter glass L9 arranged sequentially along the optical axis from the object side to the image side. 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 1.76 mm, an aperture number F# of 1.9, and a field of view of 200°.

[0083] Based on the above embodiments, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 are aspherical lenses. In this case, the aspherical surface shape equation Z of the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 satisfies:

[0084] ;

[0085] Where Z is the sag of the aspherical surface. Let be the fundamental curvature at the vertex. For conic section constants, The radial coordinate is perpendicular to the optical axis. For higher-order terms, Let i be a higher-order term of the aspherical surface, where i is a positive integer from 2 to 15.

[0086] Table 3 Aspheric coefficients in fisheye lenses

[0087]

[0088] Where -1.34E-02 indicates that the coefficient a4 of surface number S5 is -1.34 × 10⁻⁶. -2 And so on.

[0089] Furthermore, Figure 2 yes Figure 1The diagram shown illustrates the beam pattern of a fisheye lens, as follows: Figure 2 As shown, the fan diagram is one of the most commonly used evaluation methods in modern optical design. Figure 2 As shown, the horizontal axis of a single ray fan plot represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, at which point all rays in the field of view focus at the same point on the image plane. The vertical axis in a single image can also represent the maximum diffusion range of the beam on the ideal image plane. Ray fan plots can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 2 As shown, Figure 1 The optical system of the fisheye lens shows that the ray fan plots for each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) at various fields of view closely match the horizontal axis, indicating that the transverse aberrations at each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) are well corrected. Furthermore, the curves for each color at each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) do not exhibit significant dispersion, indicating that the optical system of this fisheye lens also provides good correction for chromatic aberration, ensuring the imaging requirement of sharp images across the entire spectral range.

[0090] Figure 3 yes Figure 1 The schematic diagram of the spherical aberration curve of the fisheye lens is shown below. Figure 3 As shown, the vertical direction represents the normalized 0-field pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex; the horizontal direction represents the spherical aberration at different wavelengths (436nm, 470nm, 510nm, 555nm, 610nm, 650nm), in micrometers (μm). Figure 3 It can be seen that the curves for different wavelengths (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) are relatively concentrated, indicating that the spherical aberration of the fisheye lens is very small.

[0091] Figure 4 yes Figure 1 The diagram showing the chromatic aberration curve of the fisheye lens is as follows: Figure 4 As shown, the vertical direction represents the normalized field of view, with 0 indicating the optical axis, and the vertical vertex representing the maximum field radius; the horizontal direction represents the offset within the 0.555μm meridional range, in micrometers (μm). The numbers on the curves (0.4360, 0.470, 0.510, 0.5550, 0.6100, 0.6500) represent the wavelengths depicted by the curves, in micrometers (μm). Figure 4It can be seen that the vertical color difference can be controlled within the range of (-2.5μm, 2.5μm).

[0092] In another feasible embodiment, Figure 5 This is a schematic diagram of another fisheye lens provided in an embodiment of the present invention. Table 4 describes in detail another feasible implementation. Figure 5 The specific optical physical parameters of the fisheye lens are shown.

[0093] Table 4. Another optical physical parameter design for fisheye lenses

[0094]

[0095] 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.

[0096] Table 5. Another parameter design for each lens in a fisheye lens

[0097]

[0098] The fisheye lens of this embodiment includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture stop STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter glass L9 arranged sequentially along the optical axis from the object side to the image side. 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 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 2.24 mm, an aperture number F# of 1.9, and a field of view of 200°.

[0099] Based on the above embodiments, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 are aspherical lenses. In this case, the aspherical surface shape equation Z of the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 satisfies:

[0100] ;

[0101] Where Z is the sag of the aspherical surface. Let be the fundamental curvature at the vertex. For conic section constants, The radial coordinate is perpendicular to the optical axis. For higher-order terms, Let i be a higher-order term of the aspherical surface, where i is a positive integer from 2 to 15.

[0102] Table 6 Aspherical coefficients in fisheye lenses

[0103]

[0104] Where -1.52E-02 indicates that the coefficient a4 of surface number S5 is -1.52 × 10⁻⁶. -2 And so on.

[0105] Furthermore, Figure 6 yes Figure 5 The diagram shown illustrates the beam pattern of a fisheye lens, as follows: Figure 6 As shown, the fan diagram is one of the most commonly used evaluation methods in modern optical design. Figure 6 As shown, the horizontal axis of a single ray fan plot represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, at which point all rays in the field of view focus at the same point on the image plane. The vertical axis in a single image can also represent the maximum diffusion range of the beam on the ideal image plane. Ray fan plots can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 6 As shown, Figure 5 The optical system of the fisheye lens shows that the ray fan plots for each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) at various fields of view closely match the horizontal axis, indicating that the transverse aberrations at each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) are well corrected. Furthermore, the curves for each color at each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) do not exhibit significant dispersion, indicating that the optical system of this fisheye lens also provides good correction for chromatic aberration, ensuring the imaging requirement of sharp images across the entire spectral range.

[0106] Figure 7 yes Figure 5 The schematic diagram of the spherical aberration curve of the fisheye lens is shown below. Figure 7As shown, the vertical direction represents the normalized 0-field pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex; the horizontal direction represents the spherical aberration at different wavelengths (436nm, 470nm, 510nm, 555nm, 610nm, 650nm), in micrometers (μm). Figure 7 It can be seen that the curves for different wavelengths (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) are relatively concentrated, indicating that the spherical aberration of the fisheye lens is very small.

[0107] Figure 8 yes Figure 5 The diagram showing the chromatic aberration curve of the fisheye lens is as follows: Figure 8 As shown, the vertical direction represents the normalized field of view, with 0 indicating the optical axis, and the vertical vertex representing the maximum field radius; the horizontal direction represents the offset within the 0.555μm meridional range, in micrometers (μm). The numbers on the curves (0.4360, 0.470, 0.510, 0.5550, 0.6100, 0.6500) represent the wavelengths depicted by the curves, in micrometers (μm). Figure 8 It can be seen that the vertical color difference can be controlled within the range of (-2μm, 2μm).

[0108] In yet another feasible embodiment, Figure 9 This is a schematic diagram of another fisheye lens provided in the embodiments of the present invention. Table 7 describes in detail another feasible implementation. Figure 9 The specific optical physical parameters of the fisheye lens are shown.

[0109] Table 7 Another optical physical parameter design for fisheye lenses

[0110]

[0111] 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.

[0112] Table 8 Another parameter design for each lens in a fisheye lens

[0113]

[0114] The fisheye lens of this embodiment includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture stop STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter glass L9 arranged sequentially along the optical axis from the object side to the image side. 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 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 2.01 mm, an aperture number F# of 1.9, and a field of view of 200°.

[0115] Based on the above embodiments, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 are aspherical lenses. In this case, the aspherical surface shape equation Z of the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 satisfies:

[0116] ;

[0117] Where Z is the sag of the aspherical surface. Let be the fundamental curvature at the vertex. For conic section constants, The radial coordinate is perpendicular to the optical axis. For higher-order terms, Let i be a higher-order term of the aspherical surface, where i is a positive integer from 2 to 15.

[0118] Table 9 Aspheric coefficients in fisheye lenses

[0119]

[0120] Where -1.28E-02 indicates that the coefficient a4 of surface number S5 is -1.28 × 10⁻⁶. -2 And so on.

[0121] Furthermore, Figure 10 yes Figure 9The diagram shown illustrates the beam pattern of a fisheye lens, as follows: Figure 10 As shown, the fan diagram is one of the most commonly used evaluation methods in modern optical design. Figure 10 As shown, the horizontal axis of a single ray fan plot represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, at which point all rays in the field of view focus at the same point on the image plane. The vertical axis in a single image can also represent the maximum diffusion range of the beam on the ideal image plane. Ray fan plots can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 10 As shown, Figure 9 The optical system of the fisheye lens shows that the ray fan plots for each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) at various fields of view closely match the horizontal axis, indicating that the transverse aberrations at each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) are well corrected. Furthermore, the curves for each color at each wavelength (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) do not exhibit significant dispersion, indicating that the optical system of this fisheye lens also provides good correction for chromatic aberration, ensuring the imaging requirement of sharp images across the entire spectral range.

[0122] Figure 11 yes Figure 9 The schematic diagram of the spherical aberration curve of the fisheye lens is shown below. Figure 11 As shown, the vertical direction represents the normalized 0-field pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex; the horizontal direction represents the spherical aberration at different wavelengths (436nm, 470nm, 510nm, 555nm, 610nm, 650nm), in micrometers (μm). Figure 11 It can be seen that the curves for different wavelengths (436nm, 470nm, 510nm, 555nm, 610nm, 650nm) are relatively concentrated, indicating that the spherical aberration of the fisheye lens is very small.

[0123] Figure 12 yes Figure 9 The diagram showing the chromatic aberration curve of the fisheye lens is as follows: Figure 12 As shown, the vertical direction represents the normalized field of view, with 0 indicating the optical axis, and the vertical vertex representing the maximum field radius; the horizontal direction represents the offset within the 0.555μm meridional range, in micrometers (μm). The numbers on the curves (0.4360, 0.470, 0.510, 0.5550, 0.6100, 0.6500) represent the wavelengths depicted by the curves, in micrometers (μm). Figure 12It can be seen that the vertical color difference can be controlled within the range of (-3μm, 3μm).

[0124] 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 which is determined by the scope of the appended claims.

Claims

1. A fisheye lens, characterized in that, include: The first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens are arranged sequentially from the object side to the image side; The first lens has negative optical power, the second lens has negative optical power, the third lens has optical power, the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, the seventh lens has positive optical power, and the eighth lens has negative optical power. The maximum field of view of the fisheye lens is DFOV, the image height below the maximum field of view of the fisheye lens is H, and the total focal length of the fisheye lens is f; wherein, 14.027≤DFOV / H / f≤19.

708.

2. The fisheye lens according to claim 1, characterized in that, The first lens and the second lens are spherical lenses; the third lens to the eighth lens are aspherical lenses.

3. The fisheye lens according to claim 1, characterized in that, The first and second lenses are glass lenses; the third to eighth lenses are plastic lenses.

4. The fisheye lens according to claim 1, characterized in that, 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 convex, and the image-side surface is concave. The object-side surface of the third lens is concave, and the image-side surface is convex. Both the object-side and image-side surfaces of the fourth lens are convex. Both the object-side and image-side surfaces of the fifth lens are convex. Both the object-side and image-side surfaces of the sixth lens are concave. The object-side and image-side surfaces of the seventh lens are both convex.

5. The fisheye lens according to claim 1, characterized in that, The optical power φ1 of the first lens, the optical power φ2 of the second lens, and the total optical power φ of the fisheye lens satisfy the following: -6.53≤φ1 / φ≤-4.807; -3.43≤φ2 / φ≤-2.

516.

6. The fisheye lens according to claim 1, characterized in that, The optical power φ5 of the fifth lens, the optical power φ6 of the sixth lens, and the total optical power φ of the fisheye lens satisfy the following: -0.281≤(φ5+φ6) / φ≤-0.

249.

7. The fisheye lens according to claim 1, characterized in that, The Abbe number Vd2 and refractive index Nd2 of the second lens satisfy: 55.9 <Vd2<80.5; 1.54 <Nd2<1.7。 8. The fisheye lens according to claim 1, characterized in that, The object curvature R21 and image curvature R22 of the second lens satisfy: 4.966 <R21 / R22<7.53。 9. The fisheye lens according to claim 1, characterized in that, The distance TTL from the object-side surface of the first lens to the image plane of the fisheye lens, the maximum effective radius D1 of the object-side surface of the first lens, and the image height Hmax of the fisheye lens at the maximum field of view satisfy the following: 0.143 <TTL / (D1*Hmax)<0.192。 10. The fisheye lens according to claim 1, characterized in that, The center thickness CT5 of the fifth lens, the center thickness CT6 of the sixth lens, the center thickness CT7 of the seventh lens, and the center thickness CT8 of the eighth lens satisfy the following: 3mm<(CT5+CT6+CT7+CT8)<5mm.

11. The fisheye lens according to claim 1, characterized in that, Also includes: An aperture stop located in the optical path between the fourth lens and the fifth lens.

12. The fisheye lens according to claim 11, characterized in that, The maximum effective radius D1 of the object-side surface of the first lens, the effective radius ST of the aperture, and the maximum effective radius D8 of the object-side surface of the eighth lens satisfy the following: 3.39<(D1 / ST) / (D8 / ST)<3.469。

Images