Prime lens

Abstract

The utility model discloses a prime lens comprising a front lens group, a diaphragm and a rear lens group which are arranged from an object plane to an image plane along an optical axis. The front lens group comprises a first lens, a second lens and a third lens which are sequentially arranged from the object plane to the image plane, the focal power of the first lens is negative, the focal power of the second lens is negative, and the focal power of the third lens is positive; the focal power of the rear lens group is positive, and the rear lens group comprises a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from the object plane to the image plane, the focal power of the fourth lens is positive, the focal power of the fifth lens is negative, the focal power of the sixth lens is positive, the focal power of the seventh lens is negative, and the focal power of the eighth lens is positive; the focal power of the front lens group is phi front, the focal power of the rear lens group is phi rear, and the focal power of the prime lens is phi; wherein-0.085 < = phi front / phi < = 0.25, and 0.35 < = phi rear / phi < = 0.48. Through the lens group and the focal power distribution of each lens, the design of a large-aperture and large-target-surface prime lens can be realized.

Description

Technical Field

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

[0002] With the continuous advancement of the security surveillance industry, society has placed increasingly higher demands on security. Ultra-high-definition lens systems with wide field of view, large target area, large aperture, day and night focus, and good environmental adaptability are becoming increasingly popular in the security market.

[0003] The existing lenses that can meet this requirement even use glass aspherical surfaces, which not only increases weight but also increases cost, making it unfavorable for popularization. Utility Model Content

[0004] The utility model provides a fixed-focus lens, which realizes the design of a fixed-focus lens with a larger aperture and a larger target surface by reasonably setting the lens composition method, optical power distribution method and optical power parameters.

[0005] The embodiment of the utility model provides a fixed-focus lens, comprising a front lens group, an aperture, and a rear lens group arranged in sequence along the optical axis from the object plane to the image plane;

[0006] The front lens group includes a first lens, a second lens, and a third lens arranged in sequence from the object plane to the image plane, the first lens has a negative optical power, the second lens has a negative optical power, and the third lens has a positive optical power;

[0007] The rear lens group has positive optical power and includes a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in order from the object plane to the image plane, wherein the fourth lens has positive optical power, the fifth lens has negative optical power, the sixth lens has positive optical power, the seventh lens has negative optical power, and the eighth lens has positive optical power;

[0008] The optical power of the front lens group is The optical power of the rear lens group is The optical power of the fixed focus lens is

[0009] in,

[0010] Optionally, 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 The optical power of the eighth lens is

[0011] in,

[0012]

[0013]

[0014] Optionally, 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 fixed focus lens is

[0015] in,

[0016] Optionally, the refractive index of the third lens is ND3 and the Abbe number is VD3;

[0017] Among them, 1.70≤ND3≤2.01, 21.0≤VD3≤55.50.

[0018] Optionally, the fourth lens and the fifth lens are cemented together to form a cemented lens;

[0019] The optical power of the cemented lens is The optical power of the sixth lens is The optical power of the seventh lens is The optical power of the eighth lens is The optical power of the fixed focus lens is

[0020] in,

[0021] Optionally, the refractive index of the fourth lens is ND4, and the Abbe number is VD4, wherein 1.38≤ND4≤1.65, 64.50≤VD4≤98.50;

[0022] The refractive index ND5 and the Abbe number of the fifth lens are VD5, wherein 1.55≤ND5≤1.85 and 24.50≤VD5≤55.50.

[0023] Optionally, the first lens includes a first object-side surface close to the object plane and a first image-side surface close to the image plane, the first object-side surface is convex, and the first image-side surface is concave;

[0024] The second lens includes a second object-side surface close to the object plane and a second image-side surface close to the image plane, the second object-side surface is concave, and the second image-side surface is convex;

[0025] The third lens comprises a third object-side surface close to the object plane and a third image-side surface close to the image plane, the third object-side surface is convex, and the third image-side surface is concave;

[0026] The fourth lens comprises a fourth object-side surface close to the object plane and a fourth image-side surface close to the image plane, the fourth object-side surface is a convex surface, and the fourth image-side surface is a convex surface;

[0027] The fifth lens comprises a fifth object-side surface close to the object plane and a fifth image-side surface close to the image plane, the fifth object-side surface is concave, and the fifth image-side surface is concave;

[0028] The sixth lens comprises a sixth object-side surface close to the object plane and a sixth image-side surface close to the image plane, the sixth object-side surface is a convex surface, and the second image-side surface is a convex surface;

[0029] The seventh lens element includes a seventh object-side surface close to the object plane and a seventh image-side surface close to the image plane, the seventh object-side surface is concave, and the seventh image-side surface is concave;

[0030] The eighth lens includes an eighth object-side surface close to the object plane and an eighth image-side surface close to the image plane. The eighth object-side surface is a convex surface, and the eighth image-side surface is a convex surface.

[0031] Optionally, the first lens, the third lens, the fourth lens, the fifth lens and the eighth lens are all glass spherical lenses, and the second lens, the sixth lens and the seventh lens are all plastic aspherical lenses.

[0032] Optionally, the fixed-focus lens has a total optical length of TTL, an optical back focus of BFL, and an effective focal length of f;

[0033] Among them, 7.15≤TTL / f≤7.95; 0.42≤BFL / f≤1.55.

[0034] Optionally, the field of view of the fixed-focus lens is FOV;

[0035] Among them, FOV ≥ 160°.

[0036] The fixed-focus lens provided by the embodiment of the utility model comprises a front lens group, an aperture and a rear lens group, wherein the front lens group comprises a first lens with negative optical power, a second lens with negative optical power and a third lens with positive optical power arranged in sequence from the object plane to the image plane, the rear lens group has positive optical power and comprises a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with negative optical power and an eighth lens with positive optical power arranged in sequence from the object plane to the image plane, and the optical power of the front lens group is Optical power of fixed-focus lens Satisfaction between Optical power of the rear lens group Optical power of fixed-focus lens Satisfaction between By reasonably setting the number of lens groups included in the fixed-focus lens and the optical focal length of the lens groups, the number of lenses in each lens group and the optical focal length of each lens, the image plane illumination can be guaranteed while ensuring the imaging quality, and the image plane can be increased as much as possible to achieve the goal of a large target surface.

[0037] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 This is a structural schematic diagram of a fixed-focus lens provided in Example 1 of the present utility model;

[0040] Figure 2 This is a schematic diagram of a spherical aberration curve of a fixed-focus lens provided in Example 1 of the present utility model;

[0041] Figure 3 This is a schematic diagram of a light fan curve of a fixed-focus lens provided in Example 1 of the present utility model;

[0042] Figure 4 This is a schematic diagram of a field curvature distortion curve of a fixed-focus lens provided in Example 1 of the present utility model;

[0043] Figure 5 This is a structural schematic diagram of a fixed-focus lens provided in Example 2 of the present utility model;

[0044] Figure 6 This is a schematic diagram of a spherical aberration curve of a fixed-focus lens provided in Example 2 of the present utility model;

[0045] Figure 7 This is a schematic diagram of a light fan curve of a fixed-focus lens provided in Example 2 of the present utility model;

[0046] Figure 8 This is a schematic diagram of a field curvature distortion curve of a fixed-focus lens provided in Example 2 of the present utility model;

[0047] Figure 9 This is a structural schematic diagram of a fixed-focus lens provided in Example 3 of the present utility model;

[0048] Figure 10 This is a schematic diagram of a spherical aberration curve of a fixed-focus lens provided in Example 3 of the present utility model;

[0049] Figure 11 This is a schematic diagram of a light fan curve of a fixed-focus lens provided in Example 3 of the present utility model;

[0050] Figure 12 This is a schematic diagram of a field curvature distortion curve of a fixed-focus lens provided in Example 3 of the present utility model. DETAILED DESCRIPTION

[0051] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0052] Example 1

[0053] Figure 1 This is a schematic structural diagram of a fixed-focus lens provided in the first embodiment of the present invention. Figure 1As shown, the fixed-focus lens provided by Example 1 of the present invention includes a front lens group S1, an aperture STO and a rear lens group S2 which are arranged in sequence from the object plane to the image plane along the optical axis; the front lens group S1 includes a first lens 101, a second lens 102 and a third lens 103 which are arranged in sequence from the object plane to the image plane, the optical focal power of the first lens 101 is negative, the optical focal power of the second lens 102 is negative, and the optical focal power of the third lens 103 is positive; the optical focal power of the rear lens group S2 is positive, and includes a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107 and an eighth lens 108 which are arranged in sequence from the object plane to the image plane, the optical focal power of the fourth lens 104 is positive, the optical focal power of the fifth lens 105 is negative, the optical focal power of the sixth lens 106 is positive, the optical focal power of the seventh lens 107 is negative, and the optical focal power of the eighth lens 108 is positive; the focal power of the front lens group S1 is The optical power of the rear lens group S2 is The optical power of a fixed-focus lens is in,

[0054] Specifically, the fixed-focus lens provided in the embodiment of the present invention includes two lens groups, namely the front lens group S1 and the rear lens group S2. The front lens group S1 is arranged in the optical path between the object plane and the aperture STO, and the rear lens group S2 is arranged in the optical path between the aperture STO and the image plane, that is, the aperture STO is arranged in the optical path between the front lens group S1 and the rear lens group S2. In this way, on the one hand, the aperture size of the front lens group can be effectively reduced and the weight of the lens can be reduced; on the other hand, it is conducive to reducing the FNO value and achieving a large aperture. In this embodiment, the FNO value of the system can be 1.60.

[0055] For further reference, Figure 1 As shown, the fixed-focus lens provided by the embodiment of the present invention may further include a filter 109, which is arranged in the optical path between the eighth lens 108 and the image plane to filter out stray light and improve the imaging effect. Specifically, the filter 109 may be an infrared filter. Furthermore, the fixed-focus lens provided by the embodiment of the present invention may further include a protective glass and an image acquisition element. The protective glass may be arranged on the image side of the filter, and the image acquisition element may be arranged on the image side of the protective glass. The optical system is protected by the protective glass, and the image is acquired by the image acquisition element, thereby realizing the normal imaging function of the optical system.

[0056] Furthermore, the focal length is equal to the difference between the convergence of the image plane light beam and the convergence of the object plane light beam, and it characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal length, the stronger the ability to bend light, and the smaller the absolute value of the focal length, the weaker the ability to bend light. When the focal length is a positive number, the refraction of light is convergent; when the focal length is a negative number, the refraction of light is divergent. The focal length can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (i.e., a lens group).

[0057] In an embodiment of the present invention, the front lens group S1 includes a first lens 101 with negative optical power, a second lens 102 with negative optical power, and a third lens 103 with positive optical power, arranged sequentially from the object plane to the image plane. The first and second lenses 101 and 102 are the first lens groups in a fixed-focus lens to adjust the incident light. Their negative optical power can effectively deflect light incident at large angles, ensuring that more light enters the optical system, thereby effectively increasing the field of view of the fixed-focus lens. The third lens 103 is a positive optical power lens. This allows the third lens 103 to promptly correct the large aberrations generated by the first and second lenses 101 and 102, particularly significantly correcting the edge aberrations of the fixed-focus lens, thereby improving the imaging resolution of the optical system. In other words, the optical powers of the three lenses in the front lens group S1 are arranged in a negative-negative-positive pattern, which can effectively control the overall aberrations of the front lens group S1. Furthermore, the optical power of the front lens group S1 can be either positive or negative, and the overall optical power of the front lens group S1 can be set according to actual needs.

[0058] Furthermore, the overall optical focal length of the rear lens group S2 is positive, and includes a positive optical power fourth lens 104, a negative optical power fifth lens 105, a positive optical power sixth lens 106, a negative optical power seventh lens 107 and a positive optical power eighth lens 108 arranged in sequence from the object plane to the image plane. That is, the rear lens group S2 adopts five lens elements, and the optical focal length of the five lenses adopts a positive-negative-positive-negative-positive combination. The optical focal length of the rear lens in the optical path is different from that of the previous lens, which is conducive to the correction of aberrations.

[0059] Furthermore, the optical power of the front lens group Optical power of fixed-focus lens Satisfaction between Optical power of the rear lens group Optical power of fixed-focus lens Satisfaction between That is to say, the optical power of the front lens group S1 and the rear lens group S2 of the fixed-focus lens is limited to a reasonable distribution ratio, which is beneficial to controlling the height of the incident light of the front lens group S1, reducing the front aperture, and thus reducing the weight; in addition, the reasonable optical power distribution of the front and rear lens groups can increase the image surface as much as possible while ensuring the illumination of the image surface, thereby achieving the goal of a large target surface.

[0060] In summary, the fixed-focus lens provided by the embodiment of the present invention can ensure the image quality while ensuring the image plane illumination by reasonably setting the number of lens groups, the optical focal length of the lens groups, the optical focal length distribution ratio of the lens groups, the number of lenses included in the lens groups, and the optical focal length of each lens, and can also increase the image plane as much as possible to achieve the goal of a large target surface.

[0061] Based on the above embodiment, the optical power of the first lens 101 is The optical power of the second lens 102 is The optical power of the third lens 103 is The optical power of the fourth lens 104 is The optical power of the fifth lens 105 is The optical power of the sixth lens 106 is The optical power of the seventh lens 107 is The optical power of the eighth lens 108 is in, Reasonable optical power distribution enables the system to have smaller aberrations while meeting the design indicators. At the same time, the system tolerance sensitivity is low, which can reduce the assembly process requirements and make the system more cost-effective.

[0062] Based on the above embodiment, the optical power of the first lens 101 is The optical power of the second lens 102 is The optical power of the third lens 103 is The optical power of a fixed-focus lens is in,

[0063] Specifically, the optical power of the first lens 101 is set to Optical power of fixed-focus lens Satisfaction between This is beneficial for converging incident light, controlling the optical path of the optical system, and reducing the size. Optical power of fixed-focus lens Satisfaction between Refractive power of the third lens 103 Optical power of fixed-focus lens Satisfaction between This is beneficial for balancing the light aberration in front of the aperture STO and improving the imaging quality.

[0064] Based on the above embodiment, the refractive index of the third lens element 103 is ND3, and the Abbe number is VD3; where 1.70≤ND3≤2.01, and 21.0≤VD3≤55.50. By limiting the refractive index and Abbe number of the third lens element 103, aberrations can be balanced, light height can be controlled, and the size of the fixed-focus lens can be reduced.

[0065] Based on the above embodiment, the fourth lens 104 and the fifth lens 105 are cemented together to form a cemented lens; the optical power of the cemented lens is The optical power of the sixth lens 106 is The optical power of the seventh lens 107 is The optical power of the eighth lens 108 is The optical power of a fixed-focus lens is in,

[0066] Specifically, the cemented arrangement of the fourth lens 104 and the fifth lens 105 can be understood as the image-side surface of the fourth lens 104 being bonded to the object-side surface of the fifth lens 105. In other words, the image-side surface of the fourth lens 1041 is bonded to the object-side surface of the fifth lens 105. By cementing the fourth and fifth lenses 104, 105, the air gap between them can be reduced, helping to shorten the overall optical length of the lens. It also reduces sensitivity to tolerances such as tilt and deflection during lens unit assembly, simplifying the assembly process and improving equipment efficiency. Furthermore, the cemented arrangement of the fourth and fifth lenses 104, 105 reduces light loss caused by inter-lens reflections, improving illumination and reducing the risk of ghosting. Furthermore, cemented lenses can minimize or eliminate chromatic aberration. Using cemented lenses in fixed-focus lenses can improve image quality and reduce light energy loss due to reflection, thereby enhancing image quality and clarity. Furthermore, the fourth lens 104 and the fifth lens 105 can be supported by a gasket, or can be glued together by gluing. The embodiments of the present invention do not limit the specific gluing method. Furthermore, by providing a glued lens and reasonably setting its optical focal length, it is beneficial to balance chromatic aberration of the lens system. Moreover, the glued lens is located after the aperture STO, which is beneficial to correcting chromatic aberration and improving the imaging quality of the optical system; at the same time, it can also smoothly transmit light, reduce the tolerance sensitivity of the optical system, and improve the assembly yield of the optical system. At the same time, by reasonably setting the proportional relationship between the optical focal length of the sixth lens 106, the seventh lens 107, and the eighth lens 108 and the optical focal length of the fixed-focus lens, it is possible to control aberrations, reduce tolerance sensitivity, and help improve image quality.

[0067] Based on the above embodiment, the refractive index of the fourth lens element 104 is ND4, and the Abbe number is VD4, where 1.38≤ND4≤1.65 and 64.50≤VD4≤98.50. The refractive index of the fifth lens element 105 is ND5, and the Abbe number is VD5, where 1.55≤ND5≤1.85 and 24.50≤VD5≤55.50. By limiting the refractive index and Abbe number of the fourth lens element 104 and the fifth lens element 105, the light height can be controlled, which facilitates the reduction of the size of the fixed-focus lens, balances aberrations, and improves image quality.

[0068] On the basis of the above embodiment, the first lens 101 includes a first object-side surface close to the object plane and a first image-side surface close to the image plane, the first object-side surface is convex, and the first image-side surface is concave; the second lens 102 includes a second object-side surface close to the object plane and a second image-side surface close to the image plane, the second object-side surface is concave, and the second image-side surface is convex; the third lens 103 includes a third object-side surface close to the object plane and a third image-side surface close to the image plane, the third object-side surface is convex, and the third image-side surface is concave; the fourth lens 104 includes a fourth object-side surface close to the object plane and a fourth image-side surface close to the image plane, the fourth object-side surface is convex, and the fourth image-side surface is concave. The side surfaces are convex; the fifth lens element 105 includes a fifth object-side surface close to the object plane and a fifth image-side surface close to the image plane, the fifth object-side surface is concave, and the fifth image-side surface is concave; the sixth lens element 106 includes a sixth object-side surface close to the object plane and a sixth image-side surface close to the image plane, the sixth object-side surface is convex, and the second image-side surface is convex; the seventh lens element 107 includes a seventh object-side surface close to the object plane and a seventh image-side surface close to the image plane, the seventh object-side surface is concave, and the seventh image-side surface is concave; the eighth lens element 108 includes an eighth object-side surface close to the object plane and an eighth image-side surface close to the image plane, the eighth object-side surface is convex, and the eighth image-side surface is convex.

[0069] Furthermore, the object-side surface of the lens can be understood as the surface of the lens close to the object plane, and the image-side surface of the lens can be understood as the surface of the lens close to the image plane. Specifically, the object-side surface of the first lens 101 is convex, and the image-side surface is concave. This can be understood as the object-side surface of the first lens 101 being convex toward the object plane near the optical axis, and the image-side surface being concave toward the image plane near the optical axis, that is, the first lens 101 is a lens with a convex-concave structure. Furthermore, the first lens 101 can be a meniscus-shaped negative lens, which can focus as much light as possible from a large field of view into the system, thereby improving the field of view of the optical system.

[0070] Furthermore, the fixed-focus lens provided in the embodiment of the present invention has a FOV; wherein, FOV≥160°, that is, the field of view angle of the fixed-focus lens provided in the embodiment of the present invention is not less than 160°, meeting the requirements of large field of view imaging.

[0071] The object-side surface of the second lens element 102 is concave, and the image-side surface is convex. This means that the object-side surface of the second lens element 102 is concave toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the second lens element 102 has a concave-convex structure. The concave-convex negative design of the second lens element 102 effectively controls the trajectory of light, reduces field curvature and spherical aberration of the optical system, and improves image quality.

[0072] The object-side surface of the third lens element 103 is convex, and the image-side surface is concave. This means that the object-side surface of the third lens element 103 is convex toward the object plane near the optical axis, while the image-side surface is concave toward the image plane near the optical axis. In other words, the third lens element 103 has a convex-concave structure. The convex-concave positive meniscus design of the third lens element 103 effectively controls the smooth entry of light into the rear of the optical system, reducing spherical aberration and field curvature of the optical system, and improving the imaging quality of the optical system.

[0073] The fourth lens element 104 has a convex object-side surface and a convex image-side surface. This means that the object-side surface of the fourth lens element 104 is convex toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the fourth lens element 140 has a biconvex structure. The fifth lens element 105 has a concave object-side surface and a concave image-side surface. This means that the object-side surface of the fifth lens element 105 is concave toward the object plane near the optical axis, while the image-side surface is concave toward the image plane near the optical axis. In other words, the fifth lens element 105 has a biconcave structure. The convex image-side surface of the fourth lens element 104 and the concave object-side surface of the fifth lens element 105 are bonded together to form a cemented lens, which can reduce the tolerance sensitivity of the optical system and improve the assembly yield of the optical system.

[0074] The object-side surface and image-side surface of the sixth lens element 106 are convex. This means that the object-side surface of the sixth lens element 106 is convex toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the sixth lens element 106 has a biconvex structure. This biconvex positive sixth lens element effectively controls the trajectory of light, converging it and shortening the overall optical length of the system, making it more compact.

[0075] The object-side surface and image-side surface of the seventh lens element 107 are concave. This means that the object-side surface of the seventh lens element 107 is concave toward the object plane near the optical axis, and the image-side surface is concave toward the image plane near the optical axis. In other words, the seventh lens element 107 has a biconcave structure. The biconcave negative design of the seventh lens element 107 effectively controls the trajectory of light, allowing it to enter the eighth lens element at a smaller deflection angle, effectively reducing system tolerances.

[0076] The object-side surface and image-side surface of the eighth lens element 108 are convex. This means that the object-side surface of the eighth lens element 108 is convex toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. This means that the eighth lens element 108 has a biconvex structure. The biconvex positive design of the eighth lens element 108 effectively controls the trajectory of light, shortening the overall optical length and making the system more compact. Furthermore, it allows light to reach the image plane at a smaller angle, ensuring a reasonable chief ray angle (CRA) for the system, matching the CRA curve requirements of the subsequent chip.

[0077] Based on the above embodiment, the first lens 101 , the third lens 103 , the fourth lens 104 , the fifth lens 105 and the eighth lens 108 are all glass spherical lenses, and the second lens 102 , the sixth lens 106 and the seventh lens 107 are all plastic aspherical lenses.

[0078] Specifically, spherical lenses are characterized by a constant curvature from the center to the periphery, ensuring simple lens configuration. Furthermore, because glass lenses have a low coefficient of thermal expansion and excellent stability, the first lens 101, the third lens 103, the fourth lens 104, the fifth lens 105, and the eighth lens 108 can all be glass spherical lenses. Glass spherical lenses have more stable thermal properties, ensuring good resolution over a wide temperature range when carrying a large optical power. Furthermore, compared to plastic aspherical lenses, glass materials offer a wider range of options, with relatively free choices of refractive index and Abbe constant. This allows for a certain degree of control over high-order aberrations and chromatic aberrations of the lens, meeting the demands of use under complex conditions.

[0079] Aspheric lenses are characterized by a continuously varying curvature from the center to the periphery. Unlike spherical lenses, which have a constant curvature from the center to the periphery, aspheric lenses have a better curvature radius, improving distortion and astigmatism. By configuring the second lens 102, the sixth lens 106, and the seventh lens 107 as aspheric lenses, aberrations that occur during imaging can be minimized, thereby improving the imaging quality of the lens. Furthermore, the aspheric lenses can be made of plastic, which simplifies the manufacturing process and reduces the cost of aspheric lenses.

[0080] In the fixed-focus lens provided in the embodiment of the present invention, a glass spherical lens and a plastic aspherical lens can be mixed and matched, which can effectively control the cost of the fixed-focus lens while ensuring the optical performance of the fixed-focus lens; at the same time, the materials of each lens have a mutual compensation effect, which can ensure that it can still be used normally in high and low temperature environments.

[0081] Based on the above embodiment, the total optical length of the fixed-focus lens is TTL, the optical back focus is BFL, and the effective focal length is f; wherein, 7.15≤TTL / f≤7.95; 0.42≤BFL / f≤1.55.

[0082] Specifically, the optical back focus can be understood as the distance from the image side of the last lens element, that is, the image side of the eighth lens element 108, to the image plane. By properly setting the total optical length TTL of the fixed-focus lens to satisfy 7.15 ≤ TTL / f ≤ 7.95 and the optical back focus BFL to satisfy 0.42 ≤ BFL / f ≤ 1.55, a compact fixed-focus lens can be achieved.

[0083] As a feasible implementation method, the specific parameters of the fixed-focus lens are described below.

[0084] Table 1 Optical design values of the fixed-focus lens in Example 1

[0085]

[0086] Table 2 Design values of optical physical parameters of a fixed-focus lens

[0087] Surface number Surface type Curvature radius (mm) Thickness (mm) (nd) / (vd) Semi-diameter (mm) K value 1 Standard surface 35.853 1.319 1.834 / 37.23 7.97 2 Standard surface 5.161 5.676 4.70 3 even aspherical surface -4.694 3.393 1.545 / 55.99 4.39 -0.223 4 even aspherical surface -8.455 0.115 4.72 -2.671 5 Standard surface 10.602 3.931 1.808 / 22.76 4.52 6 Standard surface 70.497 2.839 4.14 7 STO INF -0.588 3.67 8 Standard surface 8.724 2.910 1.593 / 68.35 3.68 9 Standard surface -7.402 0.541 1.717 / 29.51 3.53 10 Standard surface 8.286 0.073 3.39 11 even aspherical surface 6.857 2.913 1.535 / 55.71 3.42 -0.085 12 even aspherical surface -7.661 0.144 3.49 -2.133 13 even aspherical surface -63.946 0.788 1.587 / 28.72 3.25 24.715 14 even aspherical surface 11.210 1.993 3.47 -25.958 15 Standard surface 9.746 2.585 1.550 / 75.50 4.78 16 Standard surface -126.753 3.400 4.82 17 Standard surface INF 0.600 1.517 / 64.21 4.96 18 Standard surface INF 1.863 4.97 IMA Standard surface INF 5.05

[0088] The surface numbers in Table 2 are numbered according to the order of the surfaces of each lens. "1" represents the object-side surface of the first lens, "2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of the lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface is curved toward the image side, and a negative value represents that the surface is curved toward the object side. "INF" represents that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance from the current surface to the next surface. nd represents the refractive index, which represents the light-reflecting ability of the material between the current surface and the next surface. A blank represents that the current position is air with a refractive index of 1. vd represents the Abbe number, which represents the light-dispersion characteristics of the material between the current surface and the next surface. The K value represents the numerical value of the conic coefficient of the aspheric surface. The semi-aperture represents half of the aperture size of the current surface.

[0089] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0090]

[0091] Wherein, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0092] Table 3 Aspheric coefficients of a fixed-focus lens

[0093]

[0094] Among them, "1.699367E-03" means 1.699367*10 -3 , and the remaining coefficients all use this representation method.

[0095] Based on the above parameter limitations, the optical parameters that can be achieved by the fixed-focus lens in Example 1 of the present invention are as follows:

[0096] Focal length f: 4.50mm;

[0097] F#: 1.60;

[0098] Field of view angle DFOV: 160°;

[0099] Total optical length TTL: 34.50mm.

[0100] Further, Figure 2This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Example 1 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 487nm, 546nm, 587nm, 656nm, and 850nm, respectively). Figure 2 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0101] Figure 3 This is a schematic diagram of the ray fan curve of a fixed-focus lens provided in Example 1 of the present invention. The ray fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 3 It can be seen that the system's wavelengths in each field of view are all well aligned with the horizontal axis, indicating that the vertical axis aberration of each wavelength of the system is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the system's chromatic aberration is also well corrected, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0102] Figure 4 This is a schematic diagram of a field curvature distortion curve of a fixed-focus lens provided in Example 1 of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, in millimeters (mm); the vertical coordinate represents the normalized image height, without a unit; Figure 4 As can be seen from the left figure, the lens provided by this embodiment has a maximum field of view of 80°, and both the tangential and sagittal curvature of field are effectively controlled at various wavelengths (436nm, 487nm, 546nm, 587nm, 656nm, and 850nm). This means that when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the degree of distortion in %, and the vertical coordinate represents the normalized image height, which has no unit. Figure 4 The figure on the right shows the distortion of the lens provided by this embodiment.

[0103] In summary, the fixed-focus lens provided in Example 1 of the present invention utilizes eight glass-plastic hybrid lenses. This optimal number of lenses results in a simple and compact structure. The focal length and placement of each lens are optimized, enabling daytime and night focus, strong environmental adaptability, and high resolution. Furthermore, the large aperture, wide angle, and large image surface design make this lens system highly competitive in the market. This optical lens has an F-number (FNO) of 1.60, a field of view of no less than 160°, an imaging surface compatible with 1 / 1.6-inch chips, and a total optical length of no more than 35mm, meeting the requirements for ultra-high-definition imaging.

[0104] Example 2

[0105] Figure 5 This is a schematic structural diagram of a fixed-focus lens provided in the second embodiment of the present invention. Figure 5 As shown, the fixed-focus lens provided by Example 2 of the present invention includes a front lens group S1, an aperture STO and a rear lens group S2 which are arranged in sequence from the object plane to the image plane along the optical axis; the front lens group S1 includes a first lens 101, a second lens 102 and a third lens 103 which are arranged in sequence from the object plane to the image plane, the optical focal power of the first lens 101 is negative, the optical focal power of the second lens 102 is negative, and the optical focal power of the third lens 103 is positive; the optical focal power of the rear lens group S2 is positive, and includes a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107 and an eighth lens 108 which are arranged in sequence from the object plane to the image plane, the optical focal power of the fourth lens 104 is positive, the optical focal power of the fifth lens 105 is negative, the optical focal power of the sixth lens 106 is positive, the optical focal power of the seventh lens 107 is negative, and the optical focal power of the eighth lens 108 is positive; the focal power of the front lens group S1 is The optical power of the rear lens group S2 is The optical power of a fixed-focus lens is in,

[0106] The configuration of the lens is the same as that in the first embodiment, and will not be described again here.

[0107] As another feasible implementation, specific parameters of the fixed-focus lens are described below.

[0108] Table 4 Optical design values of the fixed-focus lens in Example 2

[0109]

[0110] Table 5 Design values of optical physical parameters of a fixed-focus lens

[0111] Surface number Surface type Curvature radius (mm) Thickness (mm) (nd) / (vd) Semi-diameter (mm) K value 1 Standard surface 27.293 0.811 1.755 / 52.33 7.64 2 Standard surface 5.208 5.355 4.71 3 even aspherical surface -5.169 5.078 1.640 / 23.50 4.20 0.061 4 even aspherical surface -12.160 0.082 4.23 0.879 5 Standard surface 10.035 2.530 1.871 / 40.73 4.00 6 Standard surface 285.292 0.955 3.88 7 STO INF 3.615 3.78 8 Standard surface 8.325 3.200 1.437 / 95.10 3.34 9 Standard surface -5.356 0.827 1.613 / 44.17 3.30 10 Standard surface 11.078 0.091 3.43 11 even aspherical surface 7.928 2.694 1.545 / 55.99 3.52 -3.040 12 even aspherical surface -10.225 0.090 3.71 -8.941 13 even aspherical surface -65.460 0.917 1.640 / 23.50 3.72 -100.999 14 even aspherical surface 10.019 0.089 3.94 -10.603 15 Standard surface 9.173 2.852 1.593 / 68.62 4.25 16 Standard surface -32.564 3.400 4.47 17 Standard surface INF 0.600 1.517 / 64.21 4.89 18 Standard surface INF 1.797 4.94 IMA Standard surface INF 5.14

[0112] The surface numbers in Table 5 are numbered according to the order of the surfaces of each lens. "1" represents the object-side surface of the first lens, "2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of the lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface is curved toward the image side, and a negative value represents that the surface is curved toward the object side. "INF" represents that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance from the current surface to the next surface. nd represents the refractive index, which represents the light-reflecting ability of the material between the current surface and the next surface. A blank represents that the current position is air with a refractive index of 1. vd represents the Abbe number, which represents the dispersion characteristics of the material between the current surface and the next surface. The K value represents the numerical value of the conic coefficient of the aspheric surface. The semi-aperture represents half of the aperture size of the current surface.

[0113] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0114]

[0115] Wherein, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0116] Table 6 Aspheric coefficients of a fixed-focus lens

[0117]

[0118] Among them, "1.356385E-03" means 1.356385*10 -3 , and the remaining coefficients all use this representation method.

[0119] Based on the above parameter limitations, the optical parameters that can be achieved by the fixed-focus lens in the second embodiment of the present invention are as follows:

[0120] Focal length f: 4.52mm;

[0121] F#: 1.60;

[0122] Field of view angle DFOV: 160°;

[0123] Total optical length TTL: 34.98mm.

[0124] Further, Figure 6This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Example 2 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 487nm, 546nm, 587nm, 656nm, and 850nm, respectively). Figure 6 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.06mm, +0.06mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0125] Figure 7 This is a schematic diagram of the ray fan curve of a fixed-focus lens provided in Example 2 of the present invention. The ray fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 7 It can be seen that the system's wavelengths in each field of view are all well aligned with the horizontal axis, indicating that the vertical axis aberration of each wavelength of the system is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the system's chromatic aberration is also well corrected, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0126] Figure 8 This is a schematic diagram of a field curvature distortion curve of a fixed-focus lens provided in Example 2 of the present utility model. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, in millimeters (mm); the vertical coordinate represents the normalized image height, without a unit; Figure 8 As can be seen from the left figure, the lens provided by this embodiment has a maximum field of view of 80°, and both the tangential and sagittal curvature of field are effectively controlled at various wavelengths (436nm, 487nm, 546nm, 587nm, 656nm, and 850nm). This means that when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the degree of distortion in %, and the vertical coordinate represents the normalized image height, which has no unit. Figure 8 The figure on the right shows the distortion of the lens provided by this embodiment.

[0127] In summary, the fixed-focus lens provided in Example 2 of the present invention utilizes eight glass-plastic hybrid lenses. This optimal number of lenses results in a simple and compact structure. The focal length and placement of each lens are optimized, enabling daytime and night focus, strong environmental adaptability, and high resolution. Furthermore, the large aperture, wide angle, and large image surface design make this lens system highly competitive in the market. This optical lens has an F-number (FNO) of 1.60, a field of view of no less than 160°, an imaging surface compatible with 1 / 1.6-inch chips, and a total optical length of no more than 35mm, meeting the requirements for ultra-high-definition imaging.

[0128] Example 3

[0129] Figure 9 This is a schematic structural diagram of a fixed-focus lens provided in the third embodiment of the present invention. Figure 9 As shown, the fixed-focus lens provided by Example 3 of the present invention includes a front lens group S1, an aperture STO and a rear lens group S2 which are arranged in sequence from the object plane to the image plane along the optical axis; the front lens group S1 includes a first lens 101, a second lens 102 and a third lens 103 which are arranged in sequence from the object plane to the image plane, the optical focal power of the first lens 101 is negative, the optical focal power of the second lens 102 is negative, and the optical focal power of the third lens 103 is positive; the optical focal power of the rear lens group S2 is positive, and includes a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107 and an eighth lens 108 which are arranged in sequence from the object plane to the image plane, the optical focal power of the fourth lens 104 is positive, the optical focal power of the fifth lens 105 is negative, the optical focal power of the sixth lens 106 is positive, the optical focal power of the seventh lens 107 is negative, and the optical focal power of the eighth lens 108 is positive; the focal power of the front lens group S1 is The optical power of the rear lens group S2 is The optical power of a fixed-focus lens is in,

[0130]

[0131] The configuration of the lens is the same as that in the first embodiment, and will not be described again here.

[0132] As another feasible implementation, specific parameters of the fixed-focus lens are described below.

[0133] Table 7 Optical design values of the fixed-focus lens in Example 3

[0134]

[0135] Table 8 Design values of optical physical parameters of a fixed-focus lens

[0136] Surface number Surface type Curvature radius (mm) Thickness (mm) (nd) / (vd) Semi-diameter (mm) K value 1 Standard surface 37.872 0.773 1.782 / 37.10 7.34 2 Standard surface 4.989 5.647 4.55 3 even aspherical surface -4.643 3.338 1.535 / 55.71 4.09 -0.249 4 even aspherical surface -8.364 0.100 4.27 -2.737 5 Standard surface 10.941 4.150 1.808 / 22.69 4.00 6 Standard surface 89.090 2.666 3.85 7 STO INF -0.588 3.68 8 Standard surface 8.860 3.054 1.593 / 68.35 3.68 9 Standard surface -7.516 0.754 1.717 / 29.51 3.45 10 Standard surface 8.148 0.095 3.19 11 even aspherical surface 6.792 2.798 1.535 / 55.71 3.21 -0.104 12 even aspherical surface -7.266 0.165 3.22 -1.974 13 even aspherical surface -45.097 0.911 1.587 / 28.72 3.31 33.340 14 even aspherical surface 11.600 1.885 3.51 -26.984 15 Standard surface 10.144 2.765 1.550 / 75.50 4.70 16 Standard surface -80.561 3.400 4.78 17 Standard surface INF 0.600 1.517 / 64.21 4.95 18 Standard surface INF 1.748 4.97 IMA Standard surface INF 5.05

[0137] The surface numbers in Table 8 are numbered according to the order of the surfaces of each lens. "1" represents the object-side surface of the first lens, "2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of the lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface is curved toward the image side, and a negative value represents that the surface is curved toward the object side. "INF" represents that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance from the current surface to the next surface. nd represents the refractive index, which represents the light-reflecting ability of the material between the current surface and the next surface. A blank represents that the current position is air with a refractive index of 1. vd represents the Abbe number, which represents the light-dispersion characteristics of the material between the current surface and the next surface. The k value represents the numerical value of the conic coefficient of the aspheric surface. The semi-aperture represents half of the aperture size of the current surface.

[0138] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0139]

[0140] Wherein, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0141] Table 9 Aspheric coefficients of a fixed-focus lens

[0142]

[0143] Among them, "1.790098E-03" means 1.790098*10 -3 , and the remaining coefficients all use this representation method.

[0144] Based on the above parameter limitations, the optical parameters that can be achieved by the fixed-focus lens in Example 3 of the present invention are as follows:

[0145] Focal length f: 4.52mm;

[0146] F#: 1.60;

[0147] Field of view angle DFOV: 160°;

[0148] Total optical length TTL: 34.26mm.

[0149] Further, Figure 10This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Example 3 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 487nm, 546nm, 587nm, 656nm, and 850nm, respectively). Figure 10 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0150] Figure 11 This is a schematic diagram of the ray fan curve of a fixed-focus lens provided in Example 3 of the present invention. The ray fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. By Figure 11 It can be seen that the system's wavelengths in each field of view are all well aligned with the horizontal axis, indicating that the vertical axis aberration of each wavelength of the system is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the system's chromatic aberration is also well corrected, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0151] Figure 12 This is a schematic diagram of a field curvature distortion curve of a fixed-focus lens provided in Example 3 of the present utility model. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, in millimeters (mm); the vertical coordinate represents the normalized image height, without a unit; Figure 12 As can be seen from the left figure, the lens provided by this embodiment has a maximum field of view of 80°, and both the tangential and sagittal curvature of field are effectively controlled at various wavelengths (436nm, 487nm, 546nm, 587nm, 656nm, and 850nm). This means that when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the degree of distortion in %, and the vertical coordinate represents the normalized image height, which has no unit. Figure 12 The figure on the right shows the distortion of the lens provided by this embodiment.

[0152] In summary, the fixed-focus lens provided in Example 3 of the present invention utilizes eight glass-plastic hybrid lenses. This optimal number of lenses results in a simple and compact structure. The focal length and placement of each lens are optimized, enabling daytime and night focus, strong environmental adaptability, and high resolution. Furthermore, the large aperture, wide angle, and large image surface design make this lens system highly competitive in the market. This optical lens has an F-number (FNO) of 1.60, a field of view of no less than 160°, an imaging surface compatible with 1 / 1.6-inch chips, and a total optical length of no more than 35mm, meeting the requirements for ultra-high-definition imaging.

[0153] The above specific embodiments do not limit the scope of protection of this utility model. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model shall be included within the scope of protection of this utility model.

Claims

1. A fixed-focus lens, characterized in that: It includes a front lens group, an aperture and a rear lens group arranged in sequence from the object plane to the image plane along the optical axis; The front lens group includes a first lens, a second lens, and a third lens arranged in sequence from the object plane to the image plane, the first lens has a negative optical power, the second lens has a negative optical power, and the third lens has a positive optical power; The rear lens group has positive optical power and includes a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in order from the object plane to the image plane, wherein the fourth lens has positive optical power, the fifth lens has negative optical power, the sixth lens has positive optical power, the seventh lens has negative optical power, and the eighth lens has positive optical power; The optical power of the front lens group is φ 前 , the focal length of the rear lens group is φ 后 , the focal power of the fixed-focus lens is φ; Among them, -0.085≤φ 前 / φ≤0.25,0.35≤φ 后 / φ≤0.

48.

2. The fixed-focus lens according to claim 1, wherein: The optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the optical power of the fifth lens is φ5, the optical power of the sixth lens is φ6, the optical power of the seventh lens is φ7, and the optical power of the eighth lens is φ8; Among them,-3.55≤φ1 / φ 前 ≤12.55;-1.85≤φ2 / φ 前 ≤3.25;-6.55≤φ3 / φ 前 ≤2.55; 1.45≤φ4 / φ 后 ≤1.62;-2.55≤φ5 / φ 后 ≤-1.85;1.35≤φ6 / φ 后 ≤1.65; -1.25≤φ7 / φ 后 ≤-0.55;0.55≤φ8 / φ 后 ≤1.25。 3. The fixed-focus lens according to claim 1, wherein: The focal power of the first lens is φ1, the focal power of the second lens is φ2, the focal power of the third lens is φ3, and the focal power of the fixed-focus lens is φ; Among them, -0.85≤φ1 / φ≤-0.45; -0.35≤φ2 / φ≤-0.12; 0.285≤φ3 / φ≤0.

405.

4. The fixed-focus lens according to claim 1, wherein: The refractive index of the third lens is ND3 and the Abbe number is VD3; Among them, 1.70≤ND3≤2.01, 21.0≤VD3≤55.

50.

5. The fixed-focus lens according to claim 1, wherein: The fourth lens and the fifth lens are cemented together to form a cemented lens; The focal power of the cemented lens is φ45, the focal power of the sixth lens is φ6, the focal power of the seventh lens is φ7, the focal power of the eighth lens is φ8, and the focal power of the fixed-focus lens is φ; Among them, -0.15≤φ45 / φ≤-0.05, 0.45≤φ6 / φ≤0.85, -0.55≤φ7 / φ≤-0.15, 0.24≤φ8 / φ≤0.

45.

6. The fixed-focus lens according to claim 5, wherein: The refractive index of the fourth lens is ND4, and the Abbe number is VD4, wherein 1.38≤ND4≤1.65, 64.50≤VD4≤98.50; The refractive index ND5 and the Abbe number of the fifth lens are VD5, wherein 1.55≤ND5≤1.85 and 24.50≤VD5≤55.

50.

7. The fixed-focus lens according to claim 1, wherein: The first lens includes a first object-side surface close to the object plane and a first image-side surface close to the image plane, the first object-side surface is convex, and the first image-side surface is concave; The second lens includes a second object-side surface close to the object plane and a second image-side surface close to the image plane, the second object-side surface is concave, and the second image-side surface is convex; The third lens comprises a third object-side surface close to the object plane and a third image-side surface close to the image plane, the third object-side surface is convex, and the third image-side surface is concave; The fourth lens comprises a fourth object-side surface close to the object plane and a fourth image-side surface close to the image plane, the fourth object-side surface is a convex surface, and the fourth image-side surface is a convex surface; The fifth lens comprises a fifth object-side surface close to the object plane and a fifth image-side surface close to the image plane, the fifth object-side surface is concave, and the fifth image-side surface is concave; The sixth lens comprises a sixth object-side surface close to the object plane and a sixth image-side surface close to the image plane, the sixth object-side surface is a convex surface, and the second image-side surface is a convex surface; The seventh lens element includes a seventh object-side surface close to the object plane and a seventh image-side surface close to the image plane, the seventh object-side surface is concave, and the seventh image-side surface is concave; The eighth lens includes an eighth object-side surface close to the object plane and an eighth image-side surface close to the image plane. The eighth object-side surface is a convex surface, and the eighth image-side surface is a convex surface.

8. The fixed-focus lens according to claim 1, wherein: The first lens, the third lens, the fourth lens, the fifth lens and the eighth lens are all glass spherical lenses, and the second lens, the sixth lens and the seventh lens are all plastic aspherical lenses.

9. The fixed-focus lens according to claim 1, wherein: The fixed-focus lens has a total optical length of TTL, an optical back focus of BFL, and an effective focal length of f; Among them, 7.15≤TTL / f≤7.95; 0.42≤BFL / f≤1.

55.

10. The fixed-focus lens according to claim 1, wherein: The field of view of the fixed-focus lens is FOV; Among them, FOV ≥ 160°.

Images