A fixed-focus lens

Abstract

The present invention discloses a fixed-focus lens comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence along the optical axis from the object plane to the image plane; the first lens, the second lens, and the sixth lens are all negative-power lenses, and the third lens, the fourth lens, and the seventh lens are all positive-power lenses; the focal length of the fixed-focus lens is f, and the entrance pupil diameter of the fixed-focus lens is d; wherein 1.3 ≤ f / d ≤ 1.7. This lens addresses the common issues of small field of view (<180°), small aperture, and long overall length of most automotive lenses on the market. While ensuring high-quality image output under various lighting conditions, both during the day and at night, it also achieves the performance requirements of a small optical lens with a large aperture and ultra-wide angle.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of optical devices, and in particular to a fixed-focus lens. Background Art

[0002] With the development of the vehicle industry, the technical requirements for automotive driving assistance cameras such as forward view, side view, automatic cruise, rear view camera, and dash cam are getting higher and higher, posing higher requirements for vehicle-mounted lenses. In particular, lenses used for vehicle forward view and surround view not only need to have a large aperture to ensure high-quality image output under different lighting conditions during the day and at night, but also need to have an ultra-wide-angle view to clearly record all-round target and road information in front of and on the side of the vehicle. At the same time, miniaturization also needs to be satisfied.

[0003] However, most of the existing vehicle-mounted lenses in the market generally have problems such as a small field of view (<180°), a small aperture, and a relatively long overall length. Summary of the Invention

[0004] The present invention provides a fixed-focus lens to solve the problems generally existing in most vehicle-mounted lenses in the market, such as a small field of view (<180°), a small aperture, and a relatively long overall length, and to meet the performance requirements of a small optical lens with a large aperture and an ultra-wide angle while ensuring high-quality image output under different lighting conditions during the day and at night.

[0005] The embodiments of the present invention provide a fixed-focus lens, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence along the optical axis from the object plane to the image plane;

[0006] The first lens, the second lens, and the sixth lens are all negative-power lenses, and the third lens, the fourth lens, and the seventh lens are all positive-power lenses.

[0007] The focal length of the fixed-focus lens is f, and the entrance pupil diameter of the fixed-focus lens is d; wherein, 1.3 ≤ f / d ≤ 1.7.

[0008] Optionally, the fifth lens is a positive-power lens.

[0009] Optionally, the fifth lens is a negative-power lens.

[0010] Optionally, the first lens and the fourth lens are both glass spherical lenses, the second lens, the third lens, and the seventh lens are all plastic aspherical lenses, the fifth lens is a glass spherical lens or a plastic aspherical lens, and the sixth lens is a glass spherical lens or a plastic aspherical lens.

[0011] Optionally, the surface of the lens closer to the object surface is the object side surface, and the surface of the lens closer to the image surface is the image side surface;

[0012] The object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;

[0013] The object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface;

[0014] The object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface;

[0015] The object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface;

[0016] The object side surface of the fifth lens is a concave surface, and the image side surface of the fifth lens is a convex surface;

[0017] Or, the object side surface of the fifth lens is a convex surface, and the image side surface of the first lens is a convex surface;

[0018] The object side surface of the sixth lens is a concave surface, and the image side surface of the sixth lens is a concave surface;

[0019] The object side surface of the seventh lens is a convex surface, and the image side surface of the seventh lens is a convex surface.

[0020] Optionally, the optical power of the fixed-focus lens is The optical power of the first lens is The optical power of the second lens is The optical power of the third lens is The optical power of the fourth lens is The optical power of the fifth lens is The optical power of the sixth lens is The optical power of the seventh lens is

[0021] Wherein,

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] Optionally, the fifth lens and the sixth lens form a cemented lens.

[0029] Optionally, the optical power of the cemented lens is The optical power of the sixth lens is where

[0030] Optionally, the refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, the refractive index of the fourth lens is n4, the refractive index of the fifth lens is n5, the refractive index of the sixth lens is n6, and the refractive index of the seventh lens is n7;

[0031] The Abbe number of the first lens is v1, the Abbe number of the second lens is v2, the Abbe number of the third lens is v3, the Abbe number of the fourth lens is v4, the Abbe number of the fifth lens is v5, the Abbe number of the sixth lens is v6, and the Abbe number of the seventh lens is v7;

[0032] where 1.70 ≤ n1 ≤ 2.05; 22.3 ≤ v1 ≤ 56.6;

[0033] 1.44 ≤ n2 ≤ 1.80; 36.5 ≤ v2 ≤ 70.0;

[0034] 1.49 ≤ n3 ≤ 1.78; 10.0 ≤ v3 ≤ 31.2;

[0035] 1.65 ≤ n4 ≤ 1.95; 20.1 ≤ v4 ≤ 62.3;

[0036] 1.54 ≤ n5 ≤ 1.80; 47.2 ≤ v5 ≤ 70.0;

[0037] 1.60 ≤ n6 ≤ 2.10; 10.0 ≤ v6 ≤ 30.0;

[0038] 1.44 ≤ n7 ≤ 1.78; 43.5 ≤ v7 ≤ 70.0.

[0039] Optionally, the focal length of the fixed-focus lens is f, the image plane diameter of the fixed-focus lens is IC, the total length of the fixed-focus lens is TTL, and the entrance pupil diameter of the fixed-focus lens is d;

[0040] where 0.15 ≤ f / IC ≤ 0.33, 0.25 ≤ IC / TTL ≤ 0.45, 5.0 ≤ IC / d ≤ 8.0;

[0041] The surface of the lens closer to the image plane side is the image side surface, and the distance from the optical axis center of the image side surface of the seventh lens to the image plane is BFL; BFL / TTL ≥ 0.1.

[0042] The fixed-focus lens provided by the embodiment of the present invention adopts a combination of seven lenses, namely, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens, which are arranged in sequence along the optical axis from the object plane to the image plane. By setting that the first lens, the second lens, and the sixth lens are all negative-power lenses, and the third lens, the fourth lens, and the seventh lens are all positive-power lenses, the focal length of the fixed-focus lens is f, and the entrance pupil diameter of the fixed-focus lens is d, where 1.3 ≤ f / d ≤ 1.7. This setting can meet the performance requirements of high-definition imaging of a small-sized optical lens with a large aperture and an ultra-wide angle on the premise of low cost. Description of the Drawings

[0043] Figure 1 It is a schematic structural diagram of a fixed-focus lens provided by Embodiment 1 of the present invention;

[0044] Figure 2 It is a spherical aberration curve diagram of a fixed-focus lens provided by Embodiment 1 of the present invention;

[0045] Figure 3 It is a ray fan diagram of a fixed-focus lens provided by Embodiment 1 of the present invention;

[0046] Figure 4 It is an OPD fan diagram of a fixed-focus lens provided by Embodiment 1 of the present invention;

[0047] Figure 5 It is a schematic structural diagram of another fixed-focus lens provided by Embodiment 2 of the present invention;

[0048] Figure 6 It is a spherical aberration curve diagram of a fixed-focus lens provided by Embodiment 2 of the present invention;

[0049] Figure 7 It is a ray fan diagram of a fixed-focus lens provided by Embodiment 2 of the present invention;

[0050] Figure 8 It is an OPD fan diagram of a fixed-focus lens provided by Embodiment 2 of the present invention;

[0051] Figure 9 It is a schematic structural diagram of another fixed-focus lens provided by Embodiment 3 of the present invention;

[0052] Figure 10 It is a spherical aberration curve diagram of a fixed-focus lens provided by Embodiment 3 of the present invention;

[0053] Figure 11 It is a ray fan diagram of a fixed-focus lens provided by Embodiment 3 of the present invention;

[0054] Figure 12 It is an OPD fan diagram of a fixed-focus lens provided by Embodiment 3 of the present invention;

[0055] Figure 13 Structural diagram of another fixed-focus lens provided in Embodiment 4 of the present invention;

[0056] Figure 14 Spherical aberration curve graph of a fixed-focus lens provided in Embodiment 4 of the present invention;

[0057] Figure 15 Ray fan diagram of a fixed-focus lens provided in Embodiment 4 of the present invention;

[0058] Figure 16 OPD fan diagram of a fixed-focus lens provided in Embodiment 4 of the present invention. Detailed implementation manners

[0059] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention are shown in the drawings instead of all structures.

[0060] Figure 1 Structural diagram of a fixed-focus lens provided in an embodiment of the present invention. As Figure 1 shown, the fixed-focus lens 100 provided in the embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 110, the second lens 120, and the sixth lens 160 are all negative focal length lenses, and the third lens 130, the fourth lens 140, and the seventh lens 170 are all positive focal length lenses; the focal length of the fixed-focus lens 100 is f, and the entrance pupil diameter of the fixed-focus lens 100 is d; wherein, 1.3 ≤ f / d ≤ 1.7.

[0061] Exemplarily, the focal power is equal to the difference between the converging degree of the image plane light beam and the converging degree of the image plane light beam, and it characterizes the ability of the optical system to deflect light rays. The larger the absolute value of the focal power, the stronger the bending ability of the light rays, and the smaller the absolute value of the focal power, the weaker the bending ability of the light rays. When the focal power is positive, the refraction of the light rays is convergent; when the focal power is negative, the refraction of the light rays is divergent. The focal power can be applicable to characterize a certain refracting surface of a lens (i.e., a surface of the lens), can be applicable to characterize a certain lens, and can also be applicable to characterize a system formed by multiple lenses together (i.e., a lens group).

[0062] Specifically, each lens can be fixed to a lens barrel ( Figure 1Inside (not shown in the figure), the first lens 110 is set as a negative focal length lens, which is used to control the incident angle of light rays in the optical system and play a role in compressing the incident aperture of light rays; the second lens 120 is a negative focal length lens, which is used to correct field curvature, make the light ray trend more smoothly transition, is beneficial to shortening the total optical length of the optical lens, and realizes miniaturization; the third lens 130 is a positive focal length lens, which is used to balance the spherical aberration and axial chromatic aberration caused by the first lens 110 and the second lens 120, and is also beneficial to reducing the total length of the optical system; the fourth lens 140 is a positive focal length lens, which is used to correct spherical aberration and axial chromatic aberration, can make the light rays enter the rear optical system smoothly, can make the light rays converge and compress, and make the light ray trend smoothly pass; the fifth lens 150 can be a positive focal length lens or a negative focal length lens, and the sixth lens 160 is a negative focal length lens. Through the combination of the fifth lens 150 and the sixth lens 160, it can play the role of self-achromatism and improve the imaging quality; the seventh lens 170 is a positive focal length lens, which can make the light rays effectively and smoothly converge to the image plane, play the role of correcting off-axis aberrations such as coma and field curvature, is not easy to defocus in the change of environmental temperature, and has the advantages of small temperature drift, low chromatic aberration and high resolution.

[0063] Through the combination of 7 lenses, the focal power of each lens is reasonably distributed. The focal length of the fixed-focus lens 100 is set as f and the entrance pupil diameter is set as d, satisfying 1.3 ≤ f / d ≤ 1.7, indicating that the fixed-focus lens 100 has the characteristic of a large aperture. Its aperture number F satisfies 1.3 ≤ F ≤ 1.7, and it can still have excellent imaging effects in a low-illumination environment and can meet the imaging requirements of bright and dark environments. Through the optical system composed of the above lenses, the total optical path length is short, thus ensuring that the overall volume of the lens is small. It has the advantages of small temperature drift, low chromatic aberration and high resolution, and can realize a small-sized optical lens with a large aperture and an ultra-wide angle.

[0064] In summary, the fixed-focus lens provided by the embodiment of the present invention adopts a combination of 7 lenses. The first lens, the second lens and the sixth lens are all set as negative focal length lenses, and the third lens, the fourth lens and the seventh lens are all set as positive focal length lenses. The focal length of the fixed-focus lens is f, and the entrance pupil diameter of the fixed-focus lens is d; wherein, 1.3 ≤ f / d ≤ 1.7, so as to achieve the performance requirements of high-definition imaging of a small-sized optical lens with a large aperture and an ultra-wide angle, and has the advantages of small temperature drift, low chromatic aberration and high resolution, and can meet the application requirements of vehicle-mounted lenses.

[0065] Optionally, the fixed-focus lens further includes a diaphragm (not shown in the figure); the diaphragm is arranged in the optical path between the third lens 130 and the fourth lens 140.

[0066] Specifically, by disposing the diaphragm in the optical path between the third lens 130 and the fourth lens 140, the propagation direction of the light beam can be adjusted, and the incident angle of the light can be adjusted, which is beneficial to improving the imaging quality.

[0067] A feasible implementation manner. Continuing to refer to Figure 1 , optionally, the fifth lens 150 is a positive focal length lens. By combining the positive focal length fifth lens 150 and the negative focal length sixth lens 160, it can achieve achromatism by itself and improve the imaging quality.

[0068] A feasible implementation manner. Continuing to refer to Figure 1 , optionally, the fifth lens 150 is a negative focal length lens. By combining the negative focal length fifth lens 150 and the negative focal length sixth lens 160, it can also achieve achromatism by itself and improve the imaging quality.

[0069] Based on the above embodiments, continuing to refer to Figure 1 , both the first lens 110 and the fourth lens 140 are glass spherical lenses, the second lens 120, the third lens 130, and the seventh lens 170 are all plastic aspherical lenses, the fifth lens 150 is a glass spherical lens or a plastic aspherical lens, and the sixth lens 160 is a glass spherical lens or a plastic aspherical lens. Among them, the material of the plastic aspherical lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens is various types of glass known to those skilled in the art. The embodiments of the present invention do not elaborate or limit this.

[0070] Since the cost of a lens made of plastic material is much lower than that of a lens made of glass material, and the aspherical lens can correct all high-order aberrations. In the fixed-focus lens provided by the embodiments of the present invention, a mixed combination of glass lenses and plastic lenses is adopted. Among them, the fifth lens 150 and the sixth lens 160 are important elements for eliminating chromatic aberration in the entire lens. Considering both the cost and the imaging quality, the fifth lens 150 can be a glass spherical lens or a plastic aspherical lens, and the sixth lens 160 can be a glass spherical lens or a plastic aspherical lens. By reasonably matching the lens materials, the cost of the fixed-focus lens can be effectively controlled while ensuring the optical performance of the fixed-focus lens.

[0071] , optionally, the fifth lens 150 and the sixth lens 160 form a cemented lens. Setting the fourth lens 140 and the fifth lens 150 as a cemented lens can reduce the air gap between the fourth lens 140 and the fifth lens 150, thereby reducing the overall length of the lens. At the same time, it can eliminate its own chromatic aberration, improve the imaging quality, and can also reduce the tolerance sensitivity and improve the actual processability of the optical system. Optionally, the fifth lens 150 and the sixth lens 160 can also be not cemented, and the fixed-focus lens formed by combining with other lenses also has a high imaging quality.

[0072] Optionally, the optical power of the cemented lens is The optical power of the sixth lens is wherein, Set the optical power of the cemented lens formed by cementing the fifth lens and the sixth lens and the optical power of the sixth lens satisfy which is beneficial to the mutual correction of aberrations and also beneficial to the correction of chromatic aberration, thereby obtaining higher resolution.

[0073] In the fixed-focus lens provided by the embodiment of the present invention, by setting a combination of 5 plastic aspherical lenses, 1 glass aspherical lens and 2 glass spherical lenses, it has the advantages of high image quality and low cost. And because the two types of materials have a mutual compensation effect, the fixed-focus lens can still ensure that the resolution meets the imaging requirements in the environment of -40 to 80 °C and can still be used normally.

[0074] It should be noted that the materials of the above plastic aspherical lenses can be various plastics known to those skilled in the art, and the materials of the glass spherical lenses are various types of glass known to those skilled in the art. The embodiments of the present invention will not elaborate or limit this.

[0075] Optionally, continue to refer to Figure 1 , the surface of the lens close to the image plane side is the object side surface, the surface of the lens close to the image plane side is the image side surface, the object side surface of the first lens 110 is convex, and the image side surface of the first lens 110 is concave; the object side surface of the second lens 120 is convex, and the image side surface of the second lens 120 is concave; the object side surface of the third lens 130 is convex, and the image side surface of the third lens 130 is convex; the object side surface of the fourth lens 140 is convex, and the image side surface of the fourth lens 140 is convex; the object side surface of the fifth lens 150 is concave, and the image side surface of the fifth lens 150 is convex; or, the object side surface of the fifth lens 150 is convex, and the image side surface of the fifth lens is convex; the object side surface of the sixth lens 160 is concave, and the image side surface of the sixth lens 160 is concave; the object side surface of the seventh lens 170 is convex, and the image side surface of the seventh lens 170 is convex.

[0076] Exemplarily, by setting the shape characteristics of the object side and the image side of the first lens 110 to the seventh lens 170, the first lens 110 is a glass spherical lens with a convex-concave negative optical power, the second lens 120 is a plastic aspherical lens with a convex-concave negative optical power, the third lens 130 is a plastic aspherical lens with a concave-convex positive optical power, the fourth lens 140 is a glass spherical lens with a convex positive optical power, the sixth lens 160 is a glass spherical lens with a double-concave negative optical power or a plastic aspherical lens with a double-concave negative optical power, and the seventh lens 170 is a plastic aspherical lens with a double-convex positive optical power. Among them, the fifth lens 150 can be any one of a concave-convex positive focal length glass spherical lens, a concave-convex negative focal length glass spherical lens, a concave-convex positive focal length plastic aspherical lens, a concave-convex negative focal length plastic aspherical lens, a convex-convex positive focal length glass spherical lens, a convex-convex negative focal length glass spherical lens, a convex-convex positive focal length plastic aspherical lens, and a convex-convex negative focal length plastic aspherical lens. By reasonably setting the surface types of each lens, while ensuring that the optical powers of each lens meet the optical power requirements in the above embodiments, it is also possible to ensure that the entire fixed-focus lens has a compact structure and improve the lens integration.

[0077] Furthermore, by reasonably setting the optical power, radius of curvature, central thickness, focal length, refractive index, Abbe number, etc. of the lens, it is miniaturized to meet the performance of a super-large light transmission amount and is suitable for the monitoring requirements under low illumination conditions. At the same time, it can ensure clear color imaging under low illumination conditions and also have clear imaging under extremely low illumination conditions through the form of infrared supplementary lighting.

[0078] By reasonably setting the optical power, focal length, refractive index, Abbe constant, etc. of the lens, it is miniaturized to realize a small-sized optical lens with a large aperture and an ultra-wide angle, which is suitable for the high-quality imaging requirements of vehicle-mounted lenses.

[0079] As a feasible implementation manner, continue to refer to Figure 1 , the optical power of the fixed-focus lens 100 provided by the embodiment of the present invention is The optical power of the first lens 110 is The optical power of the second lens 120 is The optical power of the third lens 130 is The optical power of the fourth lens 140 is The optical power of the fifth lens 150 is The optical power of the sixth lens 160 is The optical power of the seventh lens 170 is

[0080] Among them,

[0081]

[0082] Specifically, the optical power of the first lens 110 is Satisfying to better compress the light entrance; the optical power of the second lens 120 is Satisfying to better correct the field curvature; the optical power of the third lens 130 is Satisfying to better correct the spherical aberration; the optical power of the fourth lens 140 is Satisfying to better correct the spherical aberration and axial chromatic aberration; the optical power of the fifth lens 150 is Satisfying The optical power of the sixth lens 160 is Satisfying Through the combination of the optical powers of the fifth lens and the sixth lens, it can better achieve its own achromatism and improve the imaging quality; the optical power of the seventh lens 170 is Satisfying to better converge light rays, correct off-axis aberrations such as coma and field curvature, and achieve the advantages of not being prone to defocusing during environmental temperature changes, having small temperature drift, low chromatic aberration and high resolution.

[0083] Among them, by reasonably distributing the focal lengths of each lens, while the spherical aberration and field curvature of the imaging system are small, the image quality of the on-axis and off-axis fields of view is improved.

[0084] As a feasible implementation method, continue to refer to Figure 1 , the refractive index of the first lens 110 is n1, the refractive index of the second lens 120 is n2, the refractive index of the third lens 130 is n3, the refractive index of the fourth lens 140 is n4, the refractive index of the fifth lens 150 is n5, the refractive index of the sixth lens 160 is n6, and the refractive index of the seventh lens 170 is n7; the Abbe number of the first lens 110 is v1, the Abbe number of the second lens 120 is v2, the Abbe number of the third lens 130 is v3, the Abbe number of the fourth lens 140 is v4, the Abbe number of the fifth lens 150 is v5, the Abbe number of the sixth lens 160 is v6, and the Abbe number of the seventh lens 170 is v7;

[0085] Among them, 1.70 ≤ n1 ≤ 2.05; 22.3 ≤ v1 ≤ 56.6; 1.44 ≤ n2 ≤ 1.80; 36.5 ≤ v2 ≤ 70.0;

[0086] 1.49 ≤ n3 ≤ 1.78; 10.0 ≤ v3 ≤ 31.2; 1.65 ≤ n4 ≤ 1.95; 20.1 ≤ v4 ≤ 62.3;

[0087] 1.54 ≤ n5 ≤ 1.80; 47.2 ≤ v5 ≤ 70.0; 1.60 ≤ n6 ≤ 2.10; 10.0 ≤ v6 ≤ 30.0;

[0088] 1.44 ≤ n7 ≤ 1.78; 43.5 ≤ v7 ≤ 70.0.

[0089] Among them, the refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium, mainly used to describe the refractive ability of the material to light. Different materials have different refractive indices. The Abbe number is an index used to represent the dispersion ability of a transparent medium. The more serious the medium dispersion, the smaller the Abbe number; conversely, the lighter the medium dispersion, the larger the Abbe number.

[0090] Thus, by setting the refractive index and Abbe number of each lens in the fixed-focus lens in combination, the balance of the incident angle sizes of the front and rear groups of lenses is ensured to reduce the sensitivity of the lens, which is beneficial to realizing the miniaturized design of the fixed-focus lens and is beneficial to achieving a higher pixel resolution and a larger aperture.

[0091] Based on the above embodiments, the focal length of the fixed-focus lens provided by the embodiments of the present invention is f, the image plane diameter of the fixed-focus lens is IC, the total length of the fixed-focus lens is TTL, and the entrance pupil diameter of the fixed-focus lens is d;

[0092] Among them, 0.15 ≤ f / IC ≤ 0.33, 0.25 ≤ IC / TTL ≤ 0.45, 5.0 ≤ IC / d ≤ 8.0;

[0093] The surface of the lens close to the image plane side is the image side surface. The distance from the optical axis center of the image side surface of the seventh lens to the image plane is BFL; BFL / TTL ≥ 0.1.

[0094] Specifically, when the image plane diameter IC and the focal length f of the fixed-focus lens provided by the embodiments of the present invention satisfy the condition of 0.15 ≤ f / IC ≤ 0.33, it indicates that the lens has an ultra-wide-angle performance, the field of view angle is greater than 210°, which can ensure the shooting range of the optical system and make the system have a larger imaging field of view.

[0095] The image plane diameter IC and the total length TTL of the fixed-focus lens provided by the embodiments of the present invention satisfy

[0096] When the condition of 0.25 ≤ IC / TTL ≤ 0.45 is satisfied, it indicates that the lens has a larger target surface and a smaller volume, can ensure that the optical system has better imaging quality and a clearer picture, and has a smaller volume. The total length TTL satisfies 13 mm ≤ TTL ≤ 17 mm.

[0097] When the image plane diameter IC of the fixed-focus lens provided by the embodiment of the present invention and the entrance pupil diameter d satisfy the condition of 5.0 ≤ IC / d ≤ 8.0, it indicates that while the optical system satisfies large image plane and high-quality imaging, by controlling the entrance pupil diameter of the optical system, it can ensure sufficient light in the marginal field of view of the large image plane and ultra-wide-angle imaging system, improve the image plane brightness, and is suitable for use in low-illumination environments.

[0098] The back focal length BFL of the fixed-focus lens provided by the embodiment of the present invention and the total length TTL satisfy

[0099] When BFL / TTL ≥ 0.1, it can ensure that there is enough installation space for the imaging sensor and the flat filter, and can ensure that the entire fixed-focus lens has a compact structure, high integration of the fixed-focus lens, is convenient for installation and use, meets the miniaturization requirements, and is suitable for the application requirements of vehicle-mounted lenses.

[0100] The fixed-focus lens provided by the embodiment of the present invention adopts a method of mixing glass spherical lenses and plastic aspherical lenses. By reasonably distributing the optical power, surface shape, Abbe number, etc. of each lens, while ensuring the performance of the optical system, it also ensures low lens cost and easy processing. The fixed-focus lens has an aperture number satisfying 1.3 at a relatively low cost, a field of view angle greater than 210°, and the total length satisfies 13 mm ≤ TTL ≤ 17 mm, and has the advantages of small temperature drift, low chromatic aberration, and high resolution.

[0101] The following lists 4 groups of embodiments of fixed-focus lenses. Refer to the attached Figure 1 - Figure 16 Further describe the specific embodiments of the fixed-focus lens applicable to the above embodiments, and further illustrate that the fixed-focus lens provided by the embodiment of the present invention has the advantages of large aperture, ultra-wide angle, miniaturization, small temperature drift, low chromatic aberration, and high resolution. Among them, Table 1 shows the optical physical parameters of the fixed-focus lenses corresponding to Embodiment 1, Embodiment 2, Embodiment 3, and Embodiment 4.

[0102] Table 1 Optical Physical Parameters of Fixed-Focus Lenses

[0103]

[0104] Embodiment 1

[0105] Continue to refer to Figure 1 , the fixed-focus lens 100 provided by the embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 110, the second lens 120, and the sixth lens 160 are all negative optical power lenses, and the third lens 130, the fourth lens 140, the fifth lens 150, and the seventh lens 170 are all positive optical power lenses; the focal length of the fixed-focus lens 100 is f, and the entrance pupil diameter of the fixed-focus lens 100 is d; among them, 1.3 ≤ f / d ≤ 1.7.

[0106] Table 2 shows the optical physical parameters of the surface type, radius of curvature, thickness, and material of each lens in the fixed-focus lens provided in the first embodiment.

[0107] Optical Physical Parameters of the Fixed-Focus Lens in Table 2

[0108] Surface Serial Number Surface Type Radius of Curvature Thickness Material (nd) Material (vd) Semi - diameter 1 Spherical Surface 12.590 1.300 1.80 46.6 7.77 2 Spherical Surface 4.784 2.446 4.28 3 Aspherical Surface -25.174 0.761 1.67 60.0 3.50 4 Aspherical Surface 2.741 1.755 1.96 5 Aspherical Surface -7.271 2.166 1.68 21.2 1.84 6 Aspherical Surface -4.134 0.567 1.79 Diaphragm Plane Infinity -0.100 1.60 8 Spherical Surface 12.278 1.341 1.75 52.3 1.60 9 Spherical Surface -3.737 0.237 1.76 10 Aspherical Surface 26.806 1.237 1.64 60.0 1.75 11 Aspherical Surface -3.934 0.085 1.90 12 Aspherical Surface -1.988 0.699 1.70 20.0 1.88 13 Aspherical Surface 6.574 0.103 2.08 14 Aspherical Surface 2.989 2.159 1.68 53.5 2.24 15 Aspherical Surface -4.830 0.551 2.36 16 Plane Infinity 0.700 1.52 64.2 2.47 17 Plane Infinity 0.892 2.52 18 Image Plane Infinity 2.62

[0109] In Table 2, the surface numbers are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side and the image side of the first lens 110, respectively, and the surfaces with surface numbers S3 and S4 are the object side and the image side of the second lens 120, respectively, and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image side, and a negative value indicates that the surface bends towards the object side; the thickness represents the central axial distance from the current surface to the next surface. The units of both the radius of curvature and the thickness are millimeters (mm).

[0110] The fixed-focus lens provided in the first embodiment of the present invention further includes a diaphragm (not shown in the figure); the diaphragm is disposed in the optical path between the third lens 130 and the fourth lens 140. By adding the diaphragm, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality.

[0111] The aspherical surface shape equation Z of the second lens 120, the third lens 130, the fifth lens 150, the sixth lens 160, and the seventh lens 170 satisfies:

[0112]

[0113] In the formula, Z is the sagitta of the distance from the vertex of the aspherical lens to the position at height y along the optical axis direction; k is the conic constant; r is the radial coordinate in the direction perpendicular to the optical axis; α2, α3, α4, α5, α6, α7, α8 are the high-order term coefficients, a i r 2i is the high-order term of the aspherical surface, i = 2, 3, 4, 5, 6, 7, 8, where the units of both Z and r are mm.

[0114] Exemplarily, Table 3 details the aspherical coefficients of each lens in the first embodiment in a feasible implementation manner.

[0115] Aspherical Coefficients in the Fixed-Focus Lens in Table 3

[0116]

[0117] Among them, 1.622996E-02 indicates that the coefficient a2 of the surface with surface number 3 is 1.62*10 -2 , and so on.

[0118] The fixed-focus lens of the first embodiment has achieved the following technical specifications:

[0119] Aperture number: F = 1.4; Focal length: f = 1.4 mm; Image plane diameter: Φ5.2 mm; Diagonal field of view angle: 220°; Total length TTL: 16.9 mm.

[0120] Figure 2 It is the spherical aberration curve graph of a fixed-focus lens provided by the first embodiment of the present invention. As Figure 2 shown, the wavelength of 0.436 μm is shown as label 1 in the figure, the wavelength of 0.486 μm is shown as label 2 in the figure, the wavelength of 0.548 μm is shown as label 3 in the figure, the wavelength of 0.588 μm is shown as label 4 in the figure, and the wavelength of 0.656 μm is shown as label 5 in the figure. The spherical aberration of this fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm, and 0.656 μm) is within 0.02 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of this fixed-focus lens is very small. Thus, it can be known that the fixed-focus lens provided by the first embodiment of the present invention can correct aberration better.

[0121] Figure 3 It is the ray fan diagram of a fixed-focus lens provided by the first embodiment of the present invention; Figure 4 It is the OPD fan diagram of a fixed-focus lens provided by the first embodiment of the present invention. Combining Figure 3 and Figure 4 shown, the imaging ranges of different wavelength rays (0.436 μm, 0.486 μm, 0.548 μm, 0.588 μm, and 0.656 μm) at different field of view angles of this fixed-focus lens are all within 50 μm and the curves are very concentrated, ensuring that the aberration and field curvature in different field of view regions are small. That is to say, this fixed-focus lens corrects the aberration of the optical system better, that is, when imaging, the image quality difference between the center and the periphery is small; the image quality is high, meeting the characteristics of a large field of view angle with a large through-light amount and a small volume.

[0122] In summary, the fixed-focus lens provided by the first embodiment of the present invention adopts a combination of 7 lenses of glass spherical mirrors and plastic aspherical surfaces. By reasonably setting the number of lenses in the fixed-focus lens, the optical power of each lens, and the relative relationship between the focal lengths of each lens, on the premise of low cost, it meets the aperture number F = 1.4, the diagonal field of view angle is 220°, the total length of the lens TTL is 16.9 mm, and has the advantages of small temperature drift, low chromatic aberration, and high resolution, achieving the requirements of high-definition imaging performance with low cost, easy processing, and miniaturization.

[0123] Embodiment Two

[0124] Figure 5 It is the structural schematic diagram of another fixed-focus lens provided by the second embodiment of the present invention. AsFigure 5 As shown in Figure 5 , the fixed-focus lens 200 provided by an embodiment of the present invention includes a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, a sixth lens 260, and a seventh lens 270 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 210, the second lens 220, and the sixth lens 260 are all negative-power lenses, and the third lens 230, the fourth lens 240, the fifth lens 250, and the seventh lens 270 are all positive-power lenses; the focal length of the fixed-focus lens 200 is f, and the entrance pupil diameter of the fixed-focus lens 200 is d; wherein, 1.3 ≤ f / d ≤ 1.7.

[0125] Table 4 shows the optical physical parameters such as the surface type, curvature radius, thickness, and material of each lens in the fixed-focus lens provided by the second embodiment.

[0126] Table 4 Optical Physical Parameters of the Fixed-Focus Lens

[0127] Surface Serial Number Surface Type Radius of Curvature Thickness Material (nd) Material (vd) Semi - diameter 1 Spherical Surface 13.200 1.300 1.80 46.6 7.39 2 Spherical Surface 4.140 2.407 3.90 3 Aspherical Surface -25.883 0.719 1.70 60.0 3.30 4 Aspherical Surface 3.413 1.667 2.13 5 Aspherical Surface -12.823 2.735 1.59 22.0 1.98 6 Aspherical Surface -4.449 0.447 1.76 Diaphragm Plane Infinity 0.000 1.76 8 Spherical Surface 11.039 1.423 1.75 52.3 1.47 9 Spherical Surface -3.711 0.146 1.77 10 Aspherical Surface 12.666 1.133 1.70 60.0 1.67 11 Aspherical Surface -4.222 0.754 1.71 20.0 1.82 12 Aspherical Surface 2.729 0.532 1.94 13 Aspherical Surface 6.643 1.727 1.61 60.0 2.04 14 Aspherical Surface -3.745 0.551 2.32 15 Plane Infinity 0.700 1.52 64.2 2.49 16 Plane Infinity 0.760 2.55 17 Image Plane Infinity 2.55

[0128] In Table 4, the surface numbers are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side surface and the image side surface of the first lens 210 respectively, the surfaces with surface numbers S3 and S4 are the object side surface and the image side surface of the second lens 220 respectively, and so on. The curvature radius represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the image plane side, and a negative value represents that the surface bends towards the object plane side; the thickness represents the central axial distance from the current surface to the next surface. The units of both the curvature radius and the thickness are millimeters (mm).

[0129] The fixed-focus lens provided by the second embodiment of the present invention further includes a diaphragm (not shown in the figure); the diaphragm is arranged in the optical path between the third lens 230 and the fourth lens 240. By adding the diaphragm, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality.

[0130] The aspherical surface shape equation Z of the second lens 220, the third lens 230, the fifth lens 250, the sixth lens 260, and the seventh lens 270 satisfies:

[0131]

[0132] In the formula, Z is the sagitta of the distance from the vertex of the aspherical lens to the position at a height of y along the optical axis direction; k is the conic constant; r is the radial coordinate in the direction perpendicular to the optical axis; α2, α3, α4, α5, α6, α7, α8 are the high-order term coefficients, a i r 2i is the high-order term of the aspherical surface, i = 2, 3, 4, 5, 6, 7, 8, wherein the units of both Z and r are mm.

[0133] Exemplarily, Table 5 details the aspherical coefficients of each lens in the second embodiment in a feasible implementation manner.

[0134] Aspherical Coefficients in the Fixed-Focus Lens

[0135]

[0136] Among them, 1.472920E-02 indicates that the coefficient a2 of the surface serial number 3 is 1.47×10 -2 , and so on.

[0137] The fixed-focus lens of the second embodiment reaches the following technical indicators:

[0138] Aperture number: F = 1.4; Focal length: f = 1.4 mm; Image plane diameter: Φ5.2 mm; Diagonal field of view angle: 210°; Total length TTL: 17 mm.

[0139] Figure 6 It is a spherical aberration curve graph of a fixed-focus lens provided by the second embodiment of the present invention. As Figure 6 shown, the wavelength 0.436 μm is shown as label 1 in the figure, the wavelength 0.486 μm is shown as label 2 in the figure, the wavelength 0.548 μm is shown as label 3 in the figure, the wavelength 0.588 μm is shown as label 4 in the figure, and the wavelength 0.656 μm is shown as label 5 in the figure. The spherical aberration of this fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm, and 0.656 μm) is within 0.02 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of this fixed-focus lens is very small. Thus, it can be known that the fixed-focus lens provided by the embodiment of the present invention can correct aberration well.

[0140] Figure 7 It is a ray fan diagram of a fixed-focus lens provided by the second embodiment of the present invention; Figure 8 It is an OPD fan diagram of a fixed-focus lens provided by the second embodiment of the present invention. Combining Figure 7 and Figure 8 shown, the imaging ranges of light rays with different wavelengths (0.436 μm, 0.486 μm, 0.548 μm, 0.588 μm, and 0.656 μm) at different field of view angles of this fixed-focus lens are all within 50 μm and the curves are very concentrated, ensuring that the aberration and field curvature in different field of view regions are small, that is, it shows that this fixed-focus lens corrects the aberration of the optical system well, that is, when imaging, the image quality difference between the center and the periphery is small; the image quality is high, meeting the characteristics of a large field of view angle with a large light throughput and a small volume.

[0141] In summary, the fixed-focus lens provided in the second embodiment of the present invention adopts a combination of 7 lenses with a glass spherical lens and a plastic aspherical lens. By reasonably setting the number of lenses in the fixed-focus lens, the optical power of each lens, and the relative relationship between the focal lengths of each lens, on the premise of low cost, it meets the requirements of an aperture number F = 1.4, a diagonal field of view of 210°, and a total lens length TTL of 17 mm. It has the advantages of small temperature drift, low chromatic aberration, and high resolution, and realizes the requirements of high-definition imaging performance with low cost, easy processing, and miniaturization.

[0142] Embodiment 3

[0143] Figure 9 FIG. is a schematic structural diagram of another fixed-focus lens provided in Embodiment 3 of the present invention. As Figure 9 shown, the fixed-focus lens 300 provided in the embodiment of the present invention includes a first lens 310, a second lens 320, a third lens 330, a fourth lens 340, a fifth lens 350, a sixth lens 360, and a seventh lens 370 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 310, the second lens 320, the fifth lens 350, and the sixth lens 360 are all negative optical power lenses, and the third lens 330, the fourth lens 340, and the seventh lens 370 are all positive optical power lenses; the focal length of the fixed-focus lens 300 is f, and the entrance pupil diameter of the fixed-focus lens 300 is d; wherein, 1.3 ≤ f / d ≤ 1.7.

[0144] Table 6 shows the optical physical parameters such as the surface type, curvature radius, thickness, and material of each lens in the fixed-focus lens provided in Embodiment 3.

[0145] Table 6 Optical Physical Parameters of the Fixed-Focus Lens

[0146] Surface Serial Number Surface Type Radius of Curvature Thickness Material (nd) Material (vd) Semi - diameter 1 Spherical Surface 10.000 1.100 1.95 32.3 5.51 2 Spherical Surface 3.472 1.589 3.03 3 Aspherical Surface 25.161 0.789 1.54 60.0 2.40 4 Aspherical Surface 1.872 1.154 1.34 5 Aspherical Surface -2.150 0.760 1.66 20.0 1.13 6 Aspherical Surface -2.145 0.022 0.98 Diaphragm Plane Infinity 0.200 0.91 8 Spherical Surface -101.489 1.223 1.85 30.1 1.07 9 Spherical Surface -2.068 0.185 1.36 10 Aspherical Surface -21.710 1.326 1.65 59.5 1.40 11 Aspherical Surface -2.034 0.595 1.99 16.1 1.49 12 Aspherical Surface 12.664 0.089 1.83 13 Aspherical Surface 10.960 2.051 1.54 60.0 1.92 14 Aspherical Surface -1.413 0.745 2.14 15 Plane Infinity 0.700 1.52 64.2 2.48 16 Plane Infinity 0.588 2.56 17 Image Plane Infinity 2.66

[0147] In Table 6, the surface numbers are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side and the image side of the first lens 310 respectively, and the surfaces with surface numbers S3 and S4 are the object side and the image side of the second lens 320 respectively, and so on. The curvature radius represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the image plane side, and a negative value represents that the surface bends towards the object plane side; the thickness represents the central axial distance from the current surface to the next surface. The units of the curvature radius and the thickness are both millimeters (mm).

[0148] The fixed-focus lens provided in Embodiment 3 of the present invention further includes a diaphragm (not shown in the figure); the diaphragm is arranged in the optical path between the third lens 330 and the fourth lens 340. By adding a diaphragm, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality.

[0149] The aspherical surface shape equation Z of the second lens 320, the third lens 330, the fifth lens 350, the sixth lens 360, and the seventh lens 370 satisfies:

[0150]

[0151] where Z is the sagitta, the distance from the vertex of the aspherical lens to the position at height y along the optical axis direction; k is the conic constant; r is the radial coordinate in the direction perpendicular to the optical axis; α2, α3, α4, α5, α6, α7, α8 are the coefficients of the high-order terms, a i r 2i is the high-order term of the aspherical surface, i = 2, 3, 4, 5, 6, 7, 8, where the units of both Z and r are mm.

[0152] Exemplarily, Table 7 details the aspherical coefficients of each lens in Embodiment 3 of the present invention in a feasible implementation manner.

[0153] Table 7 Aspherical Coefficients in the Fixed-Focus Lens

[0154]

[0155] Among them, 3.016084E-02 means that the coefficient a2 of the surface number 3 is 3.01×10 -2 , and so on.

[0156] The fixed-focus lens of Embodiment 2 of the present invention reaches the following technical indicators:

[0157] Aperture number: F = 1.5; Focal length: f = 1.1 mm; Image plane diameter: Φ5.3 mm; Diagonal field of view angle: 230°; Total length TTL: 13 mm.

[0158] Figure 10 is the spherical aberration curve graph of a fixed-focus lens provided by Embodiment 3 of the present invention. As Figure 10 shown, the wavelength 0.436 μm is shown as label 1 in the figure, the wavelength 0.486 μm is shown as label 2 in the figure, the wavelength 0.548 μm is shown as label 3 in the figure, the wavelength 0.588 μm is shown as label 4 in the figure, and the wavelength 0.656 μm is shown as label 5 in the figure. The spherical aberration of this fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm, and 0.656 μm) is within 0.02 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of this fixed-focus lens is very small. Thus, it can be known that the fixed-focus lens provided by the embodiment of the present invention can correct aberration well.

[0159] Figure 11 is the ray fan diagram of a fixed-focus lens provided by Embodiment 3 of the present invention; Figure 12The OPD light fan diagram of a fixed-focus lens provided in Embodiment 3 of the present invention. Combining Figure 11 and Figure 12 As shown, the imaging ranges of light rays with different wavelengths (0.436 μm, 0.486 μm, 0.548 μm, 0.588 μm, and 0.656 μm) at different field angles of the fixed-focus lens are all within 50 μm and the curves are very concentrated, ensuring that the aberration in different field regions is small and the field curvature is small. That is to say, the fixed-focus lens corrects the aberration of the optical system well, that is, when imaging, the image quality difference between the center and the periphery is small; the image quality is high, meeting the characteristics of a large field angle with a super large light transmission amount and a small volume.

[0160] In summary, the fixed-focus lens provided in Embodiment 3 of the present invention adopts a combination of 7 lenses with a glass spherical mirror and a plastic aspherical mirror. By reasonably setting the number of lenses in the fixed-focus lens, the optical power of each lens, and the relative relationship between the focal lengths of each lens, on the premise of low cost, it meets the requirements of an aperture number F = 1.5, a diagonal field angle of 230°, and a total lens length TTL of 13 mm, having the advantages of small temperature drift, low chromatic aberration, and high resolution, and achieving the high-definition imaging performance requirements of low cost, easy processing, and miniaturization.

[0161] Embodiment 4

[0162] Figure 13 The structural schematic diagram of another fixed-focus lens provided in Embodiment 4 of the present invention. As Figure 13 shown, the fixed-focus lens 400 provided in the embodiment of the present invention includes a first lens 410, a second lens 420, a third lens 430, a fourth lens 440, a fifth lens 450, a sixth lens 460, and a seventh lens 470 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 410, the second lens 420, and the sixth lens 460 are all negative optical power lenses, and the third lens 430, the fourth lens 440, the fifth lens 450, and the seventh lens 470 are all positive optical power lenses; the focal length of the fixed-focus lens 400 is f, and the entrance pupil diameter of the fixed-focus lens 400 is d; wherein, 1.3 ≤ f / d ≤ 1.7.

[0163] Table 8 shows the optical physical parameters such as the surface type, radius of curvature, thickness, and material of each lens in the fixed-focus lens provided in Embodiment 4.

[0164] Table 8 Optical Physical Parameters of the Fixed-Focus Lens

[0165] Surface Serial Number Surface Type Radius of Curvature Thickness Material (nd) Material (vd) Semi - diameter 1 Spherical Surface 10.553 1.071 1.80 46.6 5.06 2 Spherical Surface 3.526 1.136 2.82 3 Aspherical Surface -21.330 0.575 1.69 46.5 2.81 4 Aspherical Surface 2.956 1.335 1.71 5 Aspherical Surface -10.726 2.167 1.59 22.0 1.61 6 Aspherical Surface -3.666 0.357 1.40 Diaphragm Plane Infinity 0.000 1.24 8 Spherical Surface 9.068 1.173 1.75 52.3 1.30 9 Spherical Surface -3.054 0.119 1.48 10 Aspherical Surface 10.355 0.931 1.70 57.2 1.50 11 Aspherical Surface -3.674 0.604 1.71 20.0 1.54 12 Aspherical Surface 2.250 0.461 1.66 13 Aspherical Surface 5.840 1.522 1.57 53.8 1.69 14 Aspherical Surface -2.843 0.454 2.00 15 Plane Infinity 0.577 1.52 64.2 2.37 16 Plane Infinity 0.650 2.48 17 Image Plane Infinity 2.67

[0166] In Table 8, the surface numbers are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side surface and the image side surface of the first lens 410 respectively, the surfaces with surface numbers S3 and S4 are the object side surface and the image side surface of the second lens 420 respectively, and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the image side, and a negative value represents that the surface bends towards the object side; the thickness represents the central axial distance from the current surface to the next surface. The units of both the radius of curvature and the thickness are millimeters (mm).

[0167] The fixed-focus lens provided in the fourth embodiment of the present invention further includes a diaphragm (not shown in the figure); the diaphragm is arranged in the optical path between the third lens 430 and the fourth lens 440. By adding the diaphragm, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality.

[0168] The aspherical surface shape equation Z of the second lens 420, the third lens 430, the fifth lens 450, the sixth lens 460, and the seventh lens 470 satisfies:

[0169]

[0170] In the formula, Z is the sagitta of the distance from the vertex of the aspherical surface to the position at height y along the optical axis direction of the aspherical lens; k is the conic constant; r is the radial coordinate in the direction perpendicular to the optical axis; α2, α3, α4, α5, α6, α7, α8 are the coefficients of the high-order terms, a i r 2i is the high-order term of the aspherical surface, i = 2, 3, 4, 5, 6, 7, 8, where the units of both Z and r are mm.

[0171] Exemplarily, Table 9 details the aspherical coefficients of each lens in the fourth embodiment in a feasible implementation manner.

[0172] Table 9 Aspherical Coefficients in the Fixed-Focus Lens

[0173]

[0174] Among them, 2.635401E-02 means that the coefficient a2 of the surface with surface number 3 is 2.63×10 -2 , and so on.

[0175] The fixed-focus lens of the fourth embodiment has reached the following technical indicators:

[0176] Aperture number: F = 1.6; Focal length: f = 1.4 mm; Image plane diameter: Φ5.1 mm; Diagonal field of view angle: 220°; Total length TTL: 13 mm.

[0177] Figure 14 is the spherical aberration curve graph of a fixed-focus lens provided in the fourth embodiment of the present invention. AsFigure 10 As shown, the wavelength of 0.436 μm is shown as label 1 in the figure, the wavelength of 0.486 μm is shown as label 2 in the figure, the wavelength of 0.548 μm is shown as label 3 in the figure, the wavelength of 0.588 μm is shown as label 4 in the figure, and the wavelength of 0.656 μm is shown as label 5 in the figure. The spherical aberration of this fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm, and 0.656 μm) is within 0.02 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of this fixed-focus lens is very small. Thus, it can be known that the fixed-focus lens provided by the embodiment of the present invention can correct aberration well.

[0178] Figure 15 This is the light fan diagram of a fixed-focus lens provided by the fourth embodiment of the present invention; Figure 16 This is the OPD light fan diagram of a fixed-focus lens provided by the fourth embodiment of the present invention. Combining Figure 15 and Figure 16 As shown, the imaging ranges of light rays with different wavelengths (0.436 μm, 0.486 μm, 0.548 μm, 0.588 μm, and 0.656 μm) at different field angles of this fixed-focus lens are all within 50 μm and the curves are very concentrated, ensuring that the aberration and field curvature in different field regions are small, that is, it shows that this fixed-focus lens corrects the aberration of the optical system well. That is, when imaging, the image quality difference between the center and the periphery is small; the image quality is high, meeting the characteristics of a large field angle with a super large light transmission amount and a small volume.

[0179] In summary, the fixed-focus lens provided by the fourth embodiment of the present invention adopts a combination of 7 lenses of a glass spherical mirror and a plastic aspherical mirror. By reasonably setting the number of lenses in the fixed-focus lens, the optical power of each lens, and the relative relationship between the focal lengths of each lens, on the premise of low cost, it meets the aperture number F = 1.6, the diagonal field angle is 220°, the total lens length TTL is 13 mm, and has the advantages of small temperature drift, low chromatic aberration, and high resolution, achieving the requirements of high-definition imaging performance with low cost, easy processing, and miniaturization.

[0180] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, and various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, it can also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fixed-focus lens, characterized in that, It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence along the optical axis from the object plane to the image plane; The first lens, the second lens, and the sixth lens are all negative focal length lenses, and the third lens, the fourth lens, and the seventh lens are all positive focal length lenses; The focal length of the fixed-focus lens is f, and the entrance pupil diameter of the fixed-focus lens is d; where, 1.3 ≤ f / d ≤ 1.

7.

2. The fixed-focus lens according to claim 1, wherein The fifth lens is a positive focal length lens.

3. The fixed-focus lens according to claim 1, characterized in that, The fifth lens is a negative focal length lens.

4. The fixed-focus lens according to claim 1, wherein The first lens and the fourth lens are both glass spherical lenses, the second lens, the third lens, and the seventh lens are all plastic aspherical lenses, the fifth lens is a glass spherical lens or a plastic aspherical lens, and the sixth lens is a glass spherical lens or a plastic aspherical lens.

5. The fixed-focus lens according to claim 1, wherein The surface of the lens on the side close to the object plane is the object side surface, and the surface of the lens on the side close to the image plane is the image side surface; The object side surface of the first lens is convex, and the image side surface of the first lens is concave; The object side surface of the second lens is convex, and the image side surface of the second lens is concave; The object side surface of the third lens is concave, and the image side surface of the third lens is convex; The object side surface of the fourth lens is convex, and the image side surface of the fourth lens is convex; The object side surface of the fifth lens is concave, and the image side surface of the first lens is convex; Or, the object side surface of the fifth lens is convex, and the image side surface of the fifth lens is convex; The object side surface of the sixth lens is concave, and the image side surface of the sixth lens is concave; The object side surface of the seventh lens is convex, and the image side surface of the sixth lens is convex.

6. The fixed-focus lens according to claim 1, characterized in that The optical power of the fixed-focus lens is The optical power of the first lens is The optical power of the second lens is The optical power of the third lens is The optical power of the fourth lens is The optical power of the fifth lens is The optical power of the sixth lens is The optical power of the seventh lens is Among them, 7. The fixed-focus lens according to claim 1, characterized in that, The fifth lens and the sixth lens form a cemented lens.

8. The fixed-focus lens according to claim 7, wherein, The optical power of the cemented lens is The optical power of the sixth lens is Wherein, 9. The fixed-focus lens according to claim 1, wherein, The refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, the refractive index of the fourth lens is n4, the refractive index of the fifth lens is n5, the refractive index of the sixth lens is n6, and the refractive index of the seventh lens is n7; The Abbe number of the first lens is v1, the Abbe number of the second lens is v2, the Abbe number of the third lens is v3, the Abbe number of the fourth lens is v4, the Abbe number of the fifth lens is v5, the Abbe number of the sixth lens is v6, and the Abbe number of the seventh lens is v7; Wherein, 1.70 ≤ n1 ≤ 2.05; 22.3 ≤ v1 ≤ 56.6; 1.44 ≤ n2 ≤ 1.80; 36.5 ≤ v2 ≤ 70.0; 1.49 ≤ n3 ≤ 1.78; 10.0 ≤ v3 ≤ 31.2; 1.65 ≤ n4 ≤ 1.95; 20.1 ≤ v4 ≤ 62.3; 1.54 ≤ n5 ≤ 1.80; 47.2 ≤ v5 ≤ 70.0; 1.60 ≤ n6 ≤ 2.10; 10.0 ≤ v6 ≤ 30.0; 1.44 ≤ n7 ≤ 1.78; 43.5 ≤ v7 ≤ 70.

0.

10. The fixed-focus lens according to claim 1, wherein, The image plane diameter of the fixed-focus lens is IC, and the total length of the fixed-focus lens is TTL; Wherein, 0.15 ≤ f / IC ≤ 0.33, 0.25 ≤ IC / TTL ≤ 0.45, 5.0 ≤ IC / d ≤ 8.0; The surface of the lens closer to the image plane side is the image side surface, and the distance from the optical axis center of the image side surface of the seventh lens to the image plane is BFL; BFL / TTL ≥ 0.1.

Images