Fixed-focus optical system and vehicle-mounted lens
By rationally designing the combination of lenses and using glass spherical lenses and filters, the problems of low pixels and insufficient imaging clarity of the on-board lenses are solved, and a fixed-focus optical system with large aperture, high resolution and high temperature adaptability is achieved, which is suitable for on-board lenses.
Patent Information
- Application Number
- CN202510613756.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-13
- Publication Date
- 2025-07-22
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing automotive lenses have problems such as low pixels, small aperture and low imaging clarity, which is difficult to meet consumers' needs for high resolution and high temperature adaptability.
A fixed-focus optical system is designed, and the lens combination method is: the first lens has a positive power, the second lens has a negative power, the third lens has a positive power, the fourth lens has a positive power, the fifth lens has a negative power, the sixth lens has a positive power, the seventh lens has a negative power, and the eighth lens has a negative power. By reasonably distributing the power and refractive index, combined with the glass spherical lens and filter design, a large aperture and high pixels are achieved.
It achieves large aperture, large field of view, low cost, high resolution and high temperature adaptability, better imaging effect, small chromatic aberration and distortion, and adapts to the imaging needs of different application scenarios.
Smart Images
Figure CN120353005A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of optical technology, and particularly to a fixed-focus optical system and a vehicle-mounted lens. Background Art
[0002] With the improvement of living standards and the enhancement of people's safety awareness, consumers have put forward higher and higher requirements for vehicle-mounted lenses, expecting products to have advantages such as high temperature adaptability, low distortion, and high pixel count.
[0003] The existing lenses on the market generally have defects such as low pixel count, small aperture, and low imaging clarity, and such lens designs are difficult to meet the gradually increasing usage requirements of consumers. Summary of the Invention
[0004] The main object of the present invention is to propose a fixed-focus optical system and a vehicle-mounted lens, aiming to improve the resolution, achieve a large aperture and a large target surface, and have a better imaging effect.
[0005] To achieve the above object, the fixed-focus optical system proposed by the present invention has an object side and an image side that are oppositely arranged along the optical axis direction. The fixed-focus optical system is composed of a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and an image plane arranged in sequence from the object side to the image side;
[0006] Among them, the optical power of the first lens is positive;
[0007] The optical power of the second lens is negative;
[0008] The optical power of the third lens is positive;
[0009] The optical power of the fourth lens is positive;
[0010] The optical power of the fifth lens is negative;
[0011] The optical power of the sixth lens is positive;
[0012] The optical power of the seventh lens is positive;
[0013] The optical power of the eighth lens is negative.
[0014] In an embodiment, the object side surface of the first lens is convex, the image side surface is concave, the object side surface of the second lens is concave, the image side surface is concave, the object side surface of the third lens is convex, the image side surface is convex, the object side surface of the fourth lens is convex, the image side surface is flat, the object side surface of the fifth lens is concave, the image side surface is concave, the object side surface of the sixth lens is convex, the image side surface is convex, the object side surface of the seventh lens is convex, the image side surface is concave, and the object side surface of the eighth lens is concave, and the image side surface is concave; or,
[0015] The object side surface of the first lens is convex, and the image side surface is concave. The object side surface of the second lens is concave, and the image side surface is also concave. The object side surface of the third lens is concave, and the image side surface is convex. The object side surface of the fourth lens is convex, and the image side surface is also convex. The object side surface of the fifth lens is concave, and the image side surface is also concave. The object side surface of the sixth lens is convex, and the image side surface is also convex. The object side surface of the seventh lens is convex, and the image side surface is concave. The object side surface of the eighth lens is concave, and the image side surface is convex.
[0016] In one embodiment, the focal length of the fixed-focus optical system is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the eighth lens is f8. The focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens and the fixed-focus optical system satisfy the following relationship:
[0017] 2.5 ≤ f1 / f ≤ 3.3, -1.0 ≤ f2 / f ≤ -0.3, 0.8 ≤ f3 / f ≤ 1.6, 0.8 ≤ f4 / f ≤ 1.6, -2.5 ≤ f5 / f ≤ -1.5, 2.0 ≤ f6 / f ≤ 3.0, 1.0 ≤ f7 / f ≤ 2.0, -1.2 ≤ f8 / f ≤ -0.4.
[0018] In one embodiment, the refractive index of the first lens is Nd1, the refractive index of the second lens is Nd2, the refractive index of the third lens is Nd3, the refractive index of the fourth lens is Nd4, the refractive index of the fifth lens is Nd5, the refractive index of the sixth lens is Nd6, the refractive index of the seventh lens is Nd7, and the refractive index of the eighth lens is Nd8. The Abbe number of the first lens is Vd1, the Abbe number of the second lens is Vd2, the Abbe number of the third lens is Vd3, the Abbe number of the fourth lens is Vd4, the Abbe number of the fifth lens is Vd5, the Abbe number of the sixth lens is Vd6, the Abbe number of the seventh lens is Vd7, and the Abbe number of the eighth lens is Vd8. The refractive indices and Abbe numbers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens satisfy the following relationship:
[0019] Nd1 ≥ 1.8, Vd1 ≤ 50;
[0020] Nd2 ≤ 1.7, Vd2 ≤ 40;
[0021] Nd3 ≥ 1.6, Vd3 ≤ 60;
[0022] Nd4 ≤ 1.7, Vd4 ≤ 70;
[0023] Nd5 ≥ 1.5, Vd5 ≤ 60;
[0024] Nd6 ≤ 1.5, Vd6 ≥ 80;
[0025] Nd7 ≥ 1.8, Vd7 ≤ 50;
[0026] Nd8 ≤ 1.7, Vd8 ≤ 40.
[0027] In an embodiment, the fixed-focus optical system satisfies the following condition: BFL / TTL > 0.1;
[0028] Wherein, BFL is the distance from the center of the image side surface of the eighth lens of the fixed-focus optical system to the imaging surface of the fixed-focus optical system on the optical axis; and TTL is the distance from the center of the object side surface of the first lens to the imaging surface of the fixed-focus optical system on the optical axis.
[0029] In an embodiment, the fixed-focus optical system satisfies the following condition: 55 ≤ (FOV × f) / h ≤ 60;
[0030] Wherein, FOV is the maximum field of view angle of the fixed-focus optical system, f is the focal length of the fixed-focus optical system, and h is the image height corresponding to the maximum field of view angle.
[0031] In an embodiment, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are glass spherical lenses; and / or,
[0032] The fifth lens and the sixth lens are cemented.
[0033] In an embodiment, the aperture value of the fixed-focus optical system is F, wherein, F ≤ 1.6.
[0034] In an embodiment, the fixed-focus optical system further includes a filter, and the filter is plated on the image side surface of the fourth lens in front; and / or,
[0035] The fixed-focus optical system further includes a protective glass, and the protective glass is disposed between the eighth lens and the imaging surface.
[0036] The present invention also provides a vehicle-mounted lens, including a fixed-focus optical system. The fixed-focus optical system has an object side and an image side that are oppositely arranged along the optical axis direction. The fixed-focus optical system is composed of a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and an image plane that are arranged in sequence from the object side to the image side;
[0037] Among them, the optical power of the first lens is positive;
[0038] The optical power of the second lens is negative;
[0039] The optical power of the third lens is positive;
[0040] The optical power of the fourth lens is positive;
[0041] The optical power of the fifth lens is negative;
[0042] The optical power of the sixth lens is positive;
[0043] The optical power of the seventh lens is positive;
[0044] The optical power of the eighth lens is negative.
[0045] The technical solution of the present invention is beneficial to the control and collection of light entering the entire optical system by setting the object side surface of the first lens as a convex surface, which can effectively increase the field of view range; by setting the third lens with positive optical power, it undertakes a large optical power of the system and changes the propagation direction of the light beam, which is more conducive to the imaging of the light beam on the image plane; in addition, the adjacent first lens is set with positive optical power and the second lens is set with negative optical power. By using the thermal expansion difference between the positive and negative lenses, the overall focal length change is balanced, the overall focal length is maintained stable, thermal compensation is achieved, and the temperature adaptability is high. By comprehensively setting the optical powers of each lens, the lens can well control the light trend, correct the structural aberration better while introducing more light, and has the advantages of a large aperture, lower cost, 8M pixels, etc. through the mutual combination of different lenses and the reasonable distribution of optical power, enhancing competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS
[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.
[0047] Figure 1 It is a schematic structural diagram of an embodiment of the fixed-focus optical system provided by the present invention;
[0048] Figure 2 is Figure 1 a schematic structural diagram of another embodiment of a fixed-focus optical system;
[0049] Figure 3 is Figure 1 a spot diagram of an embodiment of a fixed-focus optical system;
[0050] Figure 4 is Figure 1 a schematic diagram of a ray aberration curve of an embodiment of a fixed-focus optical system;
[0051] Figure 5 is Figure 2 a spot diagram of another embodiment of a fixed-focus optical system;
[0052] Figure 6 is Figure 2 a schematic diagram of a ray aberration curve of another embodiment of a fixed-focus optical system.
[0053] Explanation of the reference numerals in the drawings:
[0054] L1, the first lens; L2, the second lens; L3, the third lens; L4, the fourth lens; L5, the fifth lens; L6, the sixth lens; L7, the seventh lens; L8, the eighth lens; L9, the image plane; L10, the aperture stop; L11, the protective glass.
[0055] The realization of the object of the present invention, its functional features and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Detailed implementation manners
[0056] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0057] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, such directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If this specific posture changes, then the directional indications will also change accordingly.
[0058] In addition, if the descriptions such as "first", "second", etc. are involved in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second" may explicitly or implicitly include at least one such feature. In addition, if "and / or" or "and / or" appears throughout the text, its meaning includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.
[0059] The present invention provides a fixed-focus optical system.
[0060] First of all, it should be understood that the optical power is equal to the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, and it characterizes the ability of the optical system to deflect light rays. The larger the absolute value of the optical power, the stronger the bending ability of the light rays; the smaller the absolute value of the optical power, the weaker the bending ability of the light rays. When the optical power is positive, the refraction of the light rays is convergent; when the optical power is negative, the refraction of the light rays is divergent. The optical power can be applied to characterize a certain refracting surface of a lens, can be applied to characterize a certain lens, or can be applied to characterize a system formed by multiple lenses together.
[0061] Please refer to Figure 1 , in an embodiment of the present invention, the fixed-focus optical system has an object side and an image side that are relatively arranged along the optical axis direction. The fixed-focus optical system is composed of a first lens L1, a second lens L2, a third lens L3, a diaphragm L10, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, a protective glass L11, and an image plane L9 arranged in sequence from the object side to the image side; wherein, the first lens L1 has a positive optical power; the second lens L2 has a negative optical power; the third lens L3 has a positive optical power; the fourth lens L4 has a positive optical power; the fifth lens L5 has a negative optical power; the sixth lens L6 has a positive optical power; the seventh lens L7 has a positive optical power; the eighth lens L8 has a negative optical power.
[0062] The object side of the first lens L1 is convex, and the image side is concave, which can introduce more light, facilitate the collection of light in the optical system, and effectively increase the field of view. The aperture stop L10 is arranged between the third lens L3 and the fourth lens L4, which can adjust the field of view size, block off-axis light, avoid the influence of off-axis light on the imaging quality, improve the image quality, and enable the lens to have a large light throughput. In addition, it is ensured that the optical power of the second lens L2 is negative and the optical power of the third lens L3 is positive, which controls the light trend and improves the resolution.
[0063] The technical solution of the present invention is that by setting the object side of the first lens L1 to be convex, it is beneficial to control and collect the light entering the entire optical system, and can effectively increase the field of view. By setting the third lens L3 with positive optical power, it undertakes a large optical power of the system, changes the propagation direction of the light beam, and is more conducive to the light beam imaging on the image plane L9. By comprehensively setting the optical powers of each lens, the lens can well control the light trend, correct the structural aberration better while introducing more light, and has the advantages of a large aperture, lower cost, high pixels, etc. through the mutual combination of different lenses and the reasonable distribution of optical powers, enhancing the competitiveness.
[0064] Please refer to Figure 1-2 , to ensure that the optical power of the first lens L1 is positive; the optical power of the second lens L2 is negative; the optical power of the third lens L3 is positive; the optical power of the fourth lens L4 is positive; the optical power of the fifth lens L5 is negative; the optical power of the sixth lens L6 is positive; the optical power of the seventh lens L7 is positive; the optical power of the eighth lens L8 is negative. In an embodiment of the present invention, the object side of the first lens L1 is convex, and the image side is concave; the object side of the second lens L2 is concave, and the image side is concave; the object side of the third lens L3 is convex, and the image side is convex; the object side of the fourth lens L4 is convex, and the image side is convex; the object side of the fifth lens L5 is concave, and the image side is concave; the object side of the sixth lens L6 is convex, and the image side is convex; the object side of the seventh lens L7 is convex, and the image side is convex; the object side of the eighth lens L8 is concave, and the image side is convex.
[0065] In another embodiment of the present invention, the object side of the first lens L1 is convex, and the image side is concave. The object side of the second lens L2 is concave, and the image side is also concave. The object side of the third lens L3 is concave, and the image side is convex. The object side of the fourth lens L4 is convex, and the image side is also convex. The object side of the fifth lens L5 is concave, and the image side is also concave. The object side of the sixth lens L6 is convex, and the image side is also convex. The object side of the seventh lens L7 is convex, and the image side is concave. The object side of the eighth lens L8 is concave, and the image side is convex.
[0066] It should be understood that the focal length refers to the distance from the image-side (or object-side) principal plane to the image-side (or object-side) focus in an optical system. The focal length determines the magnification and viewing angle of the image. The optical power is the reciprocal of the focal length. The focal length of the fixed-focus optical system is f, the focal length of the first lens L1 is f1, the focal length of the second lens L2 is f2, the focal length of the third lens L3 is f3, the focal length of the fourth lens L4 is f4, the focal length of the fifth lens L5 is f5, the focal length of the sixth lens L6 is f6, the focal length of the seventh lens L7 is f7, and the focal length of the eighth lens L8 is f8. The focal lengths of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8 and the fixed-focus optical system satisfy the following relationships: 2.5 ≤ f1 / f ≤ 3.3, -1.0 ≤ f2 / f ≤ -0.3, 0.8 ≤ f3 / f ≤ 1.6, 0.8 ≤ f4 / f ≤ 1.6, -2.5 ≤ f5 / f ≤ -1.5, 2.0 ≤ f6 / f ≤ 3.0, 1.0 ≤ f7 / f ≤ 2.0, -1.2 ≤ f8 / f ≤ -0.4. In addition, by reasonably setting the focal length range, the resolution of the fixed-focus optical system is improved.
[0067] In an embodiment of the present invention, the refractive index of the first lens L1 is Nd1, the refractive index of the second lens L2 is Nd2, the refractive index of the third lens L3 is Nd3, the refractive index of the fourth lens L4 is Nd4, the refractive index of the fifth lens L5 is Nd5, the refractive index of the sixth lens L6 is Nd6, the refractive index of the seventh lens L7 is Nd7, and the refractive index of the eighth lens L8 is Nd8. The Abbe number of the first lens L1 is Vd1, the Abbe number of the second lens L2 is Vd2, the Abbe number of the third lens L3 is Vd3, the Abbe number of the fourth lens L4 is Vd4, the Abbe number of the fifth lens L5 is Vd5, the Abbe number of the sixth lens L6 is Vd6, the Abbe number of the seventh lens L7 is Vd7, and the Abbe number of the eighth lens L8 is Vd8. The refractive indices and Abbe numbers of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 satisfy the following relationships: Nd1≥1.8, Vd1≤50; Nd2≤1.7, Vd2≤40; Nd3≥1.6, Vd3≤60; Nd4≤1.7, Vd4≤70; Nd5≥1.5, Vd5≤60; Nd6≤1.5, Vd6≥80; Nd7≥1.8, Vd7≤50; Nd8≤1.7, Vd8≤40; By controlling the limitations on the refractive indices and Abbe numbers of the respective lenses, the refraction angle and path of light can be controlled more precisely, thereby ensuring that the light converges to the correct position. At the same time, the corresponding Abbe number can effectively balance the refractive index differences of light of various wavelengths, reduce chromatic aberration, make the image edges clearer, and the color transition natural, forming a clear and distortion-free image.
[0068] In an embodiment of the present invention, the fixed-focus optical system satisfies the following condition: BFL / TTL>0.1;
[0069] Wherein, BFL is the distance from the center of the image side of the eighth lens L8 of the fixed-focus optical system to the image plane L9 of the fixed-focus optical system on the optical axis; and TTL is the distance from the center of the object side of the first lens L1 to the image plane L9 of the fixed-focus optical system on the optical axis; By restricting the overall optical length, the volume of the fixed-focus lens can be further reduced, which is beneficial to the miniaturization of the fixed-focus lens.
[0070] In an embodiment of the present invention, the fixed-focus optical system satisfies the following condition: 55 ≤ (FOV × f) / h ≤ 60; where FOV is the maximum field of view angle of the fixed-focus optical system, f is the fixed-focus optical system, and h is the image height corresponding to the maximum field of view angle. In this way, it helps to ensure that the optical system can obtain clear and uniform imaging effects within a specific field of view range, meet the requirements of different application scenarios for the imaging range and imaging quality, and ensure that the captured images have both a sufficient field of view and a certain degree of clarity.
[0071] Please refer to Figure 1-2 , in an embodiment of the present invention, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the eighth lens L8 are glass spherical lenses.
[0072] By using glass spherical lenses, they have a very high surface finish, thereby reducing light scattering and reflection, reducing various optical aberrations while effectively suppressing the chromatic aberration of the system, improving the imaging effect. Glass is less sensitive to temperature changes, and its shape and optical performance remain stable under temperature changes and are not easily deformed. Therefore, glass lenses can well resist the problem of lens thermal deformation, maintain high precision of the lens for a long time, and thus improve the stability of the fixed-focus optical system.
[0073] In addition, by adopting an all-glass spherical structure, it fully utilizes the spherical lenses to reduce the manufacturing difficulty of the process, corrects chromatic aberration by bonding lenses, meets the requirements of the field of view angle, distortion, chromatic aberration, and high and low temperature working performance, and has advantages such as a large aperture, lower cost, and 8M pixels, enhancing competitiveness.
[0074] Furthermore, in an embodiment of the present invention, the fifth lens L5 and the sixth lens L6 are cemented. By adding the fifth and sixth doublet lenses, the chromatic aberration of the lens is better corrected, and at the same time, it can increase the ray height of the off-axis field of view, enabling the system to have a larger target surface.
[0075] Specifically, in an embodiment of the present invention, the parameters of the fixed-focus optical system are shown in Table 1 below.
[0076] Table 1
[0077]
[0078] Figure 3 The spot diagram provided by an embodiment of the present invention is shown as follows, Figure 4 is a schematic diagram of the ray aberration curve of an embodiment of the present invention;
[0079] In another embodiment of the present invention, the parameters of the fixed-focus optical system are shown in Table 2 below.
[0080] Table 2
[0081]
[0082] Figure 5 The dot diagram provided for another embodiment of the present invention Figure 6 The schematic diagram of the ray aberration curve for another embodiment of the present invention;
[0083] It can be seen from Figure 2-6 that the two embodiments provided by the present invention have good imaging capabilities.
[0084] In one embodiment of the present invention, the aperture value of the fixed-focus optical system is F, where F ≤ 1.6; when the aperture value F of the fixed-focus optical system is within this range, the resolution and contrast of the lens perform optimally, and the lens has a large light transmission amount, high picture brightness, and better imaging effects.
[0085] In one embodiment of the present invention, the fixed-focus optical system further includes a filter, and the filter is pre-coated on the image side of the fourth lens;
[0086] It should be noted that the core of the filter pre-coating process is to directly deposit multiple functional thin films on the lens surface, replacing the physical installation of traditional independent filters, to achieve the integrated design of spectral selectivity function and optical lenses. It is a key technology for the evolution of optical design towards functional integration, structural lightness and thinness, and performance customization.
[0087] By pre-coating the filter on the image side of the fourth lens, stray light can be filtered out, preventing the stray light from reaching the fourth lens L4 and interfering with the normal visible light imaging, thereby improving the imaging quality.
[0088] In addition, in one embodiment of the present invention, the fixed-focus optical system further includes a protective glass L11, and the protective glass is disposed between the eighth lens L8 and the image plane L9 and is disposed close to the image plane L9.
[0089] It can be understood that the light carrying the information of the object to be photographed can sequentially pass through the first lens L1, the second lens L2, the third lens L3, the diaphragm L10, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the protective glass L11 and finally form an image on the image plane L9.
[0090] The present invention also proposes a vehicle-mounted lens, which includes a fixed-focus optical system. The specific structure of the fixed-focus optical system refers to the above embodiments. Since this vehicle-mounted lens adopts all the technical solutions of the above all embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one.
[0091] The above are only exemplary embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.
Claims
1. A fixed-focus optical system, characterized in that, The fixed-focus optical system has an object side and an image side that are oppositely arranged along the optical axis direction. The fixed-focus optical system is composed of a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and an image plane arranged in sequence from the object side to the image side; Among them, the optical power of the first lens is positive, the object side surface of the first lens is convex, and the image side surface is concave; The optical power of the second lens is negative; The optical power of the third lens is positive; The optical power of the fourth lens is positive; The optical power of the fifth lens is negative; The optical power of the sixth lens is positive; The optical power of the seventh lens is positive; The optical power of the eighth lens is negative.
2. The fixed-focus optical system according to claim 1, characterized in that, The object side surface of the second lens is concave, and the image side surface is concave. The object side surface of the third lens is convex, and the image side surface is convex. The object side surface of the fourth lens is convex, and the image side surface is flat. The object side surface of the fifth lens is concave, and the image side surface is concave. The object side surface of the sixth lens is convex, and the image side surface is convex. The object side surface of the seventh lens is convex, and the image side surface is concave. The object side surface of the eighth lens is concave, and the image side surface is concave; or, The object side surface of the second lens is concave, and the image side surface is also concave. The object side surface of the third lens is concave, and the image side surface is convex. The object side surface of the fourth lens is convex, and the image side surface is also convex. The object side surface of the fifth lens is concave, and the image side surface is also concave. The object side surface of the sixth lens is convex, and the image side surface is also convex. The object side surface of the seventh lens is convex, and the image side surface is concave. The object side surface of the eighth lens is concave, and the image side surface is convex.
3. The fixed-focus optical system according to claim 1, wherein The focal length of the fixed-focus optical system is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the eighth lens is f8. The focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens and the focal length of the fixed-focus optical system satisfy the following relationships: 2.5 ≤ f1 / f ≤ 3.3, -1.0 ≤ f2 / f ≤ -0.3, 0.8 ≤ f3 / f ≤ 1.6, 0.8 ≤ f4 / f ≤ 1.6, -2.5 ≤ f5 / f ≤ -1.5, 2.0 ≤ f6 / f ≤ 3.0, 1.0 ≤ f7 / f ≤ 2.0, -1.2 ≤ f8 / f ≤ -0.
4.
4. The fixed-focus optical system according to claim 1, wherein, The refractive index of the first lens is Nd1, the refractive index of the second lens is Nd2, the refractive index of the third lens is Nd3, the refractive index of the fourth lens is Nd4, the refractive index of the fifth lens is Nd5, the refractive index of the sixth lens is Nd6, the refractive index of the seventh lens is Nd7, the refractive index of the eighth lens is Nd8, the Abbe number of the first lens is Vd1, the Abbe number of the second lens is Vd2, the Abbe number of the third lens is Vd3, the Abbe number of the fourth lens is Vd4, the Abbe number of the fifth lens is Vd5, the Abbe number of the sixth lens is Vd6, the Abbe number of the seventh lens is Vd7, the Abbe number of the eighth lens is Vd8. The refractive indices and Abbe numbers of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens satisfy the following relationships: Nd1≥1.8, Vd1≤50; Nd2≤1.7, Vd2≤40; Nd3≥1.6, Vd3≤60; Nd4≤1.7, Vd4≤70; Nd5≥1.5, Vd5≤60; Nd6≤1.5, Vd6≥80; Nd7≥1.8, Vd7≤50; Nd8≤1.7, Vd8≤40.
5. The fixed-focus optical system according to claim 1, characterized in that, The fixed-focus optical system satisfies the following condition: BFL / TTL>0.1; wherein, BFL is the distance from the center of the image side surface of the eighth lens of the fixed-focus optical system to the imaging surface of the fixed-focus optical system on the optical axis; and TTL is the distance from the center of the object side surface of the first lens to the imaging surface of the fixed-focus optical system on the optical axis.
6. The fixed-focus optical system according to claim 1, wherein The fixed-focus optical system satisfies the following condition: 55≤(FOV×f) / h≤60; wherein, FOV is the maximum field of view angle of the fixed-focus optical system, f is the focal length of the fixed-focus optical system, and h is the image height corresponding to the maximum field of view angle.
7. The fixed-focus optical system according to claim 1, wherein The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are glass spherical lenses; and / or, The fifth lens and the sixth lens are cemented.
8. The fixed-focus optical system according to claim 1, wherein The aperture value of the fixed-focus optical system is F, wherein, F≤1.
6.
9. The fixed-focus optical system according to claim 1, wherein, The fixed-focus optical system further includes a filter, and the filter is coated on the image side surface of the fourth lens in front; and / or, The fixed-focus optical system further includes a protective glass, and the protective glass is disposed between the eighth lens and the imaging surface.
10. A vehicle-mounted lens, characterized in that, Comprising the fixed-focus optical system according to any one of claims 1-9.