Prime lens

Abstract

The utility model discloses a prime lens. The prime lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are sequentially arranged along an optical axis from an object side to an image side, the first lens has negative focal power; the second lens has positive focal power; the third lens has positive focal power; the fourth lens has positive focal power; the fifth lens has negative focal power; the sixth lens has positive focal power; the seventh lens has positive focal power; wherein the total length TTL of an optical system of the prime lens and the entrance pupil diameter ENPD meet the condition that TTL / ENPD is smaller than or equal to 13. By adopting the technical scheme, the prime lens has the characteristics of small volume and large aperture on the premise of ensuring that the prime lens has higher imaging resolution.

Description

Technical Field

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

[0002] With the advancement of technology, optical lenses are widely used in various fields, and the performance requirements for optical lenses are becoming increasingly stringent. For example, when optical lenses are applied in the field of driver assistance, in order to ensure driving safety and stability, driver assistance systems need to be equipped with high-resolution optical lenses to capture high-definition images as the basis for driver assistance.

[0003] However, existing high-resolution optical lenses cannot meet the requirements of large aperture and small size, thus limiting their application scenarios. Therefore, how to enable optical lenses to achieve high resolution while meeting the demands for large aperture and miniaturization has become an urgent technical problem to be solved. Utility Model Content

[0004] This invention provides a fixed-focus lens that meets the requirements of large aperture and small size while ensuring high resolution.

[0005] This utility model provides a fixed-focus lens, which includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object side to the image side;

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

[0007] The total optical system length (TTL) of the fixed-focus lens and the entrance pupil diameter (EPD) satisfy the following condition: TTL / EPD≤13.

[0008] Optionally, the total optical system length TTL of the fixed-focus lens and the effective focal length f of the fixed-focus lens satisfy: 7.2 < TTL / f < 8.3.

[0009] Optionally, the entrance pupil diameter EPD of the fixed-focus lens and the image height IH of the fixed-focus lens at the maximum field of view satisfy the following condition: 3.5 < IH / EPD < 4.

[0010] Optionally, the effective focal length f of the fixed-focus lens, the maximum field of view (FOV) of the fixed-focus lens, and the image height IH of the fixed-focus lens at the maximum field of view satisfy: (IH / 2) / (f×tan(FOV / 2)<0.6).

[0011] Optionally, the optical power of the third lens and the fourth lens satisfies:

[0012] 0.4≤Φ3 / Φ4≤0.8;

[0013] Wherein, Φ3 is the optical power of the third lens, and Φ4 is the optical power of the fourth lens.

[0014] Optionally, the optical power of the fifth lens and the sixth lens satisfies:

[0015] -1.6≤Φ5 / Φ6≤-1;

[0016] Wherein, Φ5 is the optical power of the fifth lens, and Φ6 is the optical power of the sixth lens.

[0017] Optionally, the optical power of the first lens to the seventh lens satisfies:

[0018] -0.7≤Φ1 / Φ≤-0.3;

[0019] 0≤Φ2 / Φ≤0.2;

[0020] 0≤Φ3 / Φ≤0.4;

[0021] 0.2≤Φ4 / Φ≤0.6;

[0022] -0.9≤Φ5 / Φ≤-0.5;

[0023] 0.4≤Φ6 / Φ≤0.8;

[0024] 0≤Φ7 / Φ≤0.2;

[0025] Wherein, Φ1 is the optical power of the first lens, Φ2 is the optical power of the second lens, Φ3 is the optical power of the third lens, Φ4 is the optical power of the fourth lens, Φ5 is the optical power of the fifth lens, Φ6 is the optical power of the sixth lens, Φ7 is the optical power of the seventh lens, and Φ is the optical power of the fixed-focus lens.

[0026] Optionally, the focal lengths of the first lens to the seventh lens satisfy:

[0027] -3 < f1 / f < -1.5;

[0028] 40 < f² / f < 60;

[0029] 3.5 < f3 / f < 4.85;

[0030] 2.1 < f4 / f < 3.1;

[0031] -1.4 < f5 / f < -1.15;

[0032] 1.46 < f6 / f < 1.86;

[0033] f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, and f is the effective focal length of the fixed-focus lens.

[0034] Optionally, the refractive index and Abbe number of the first lens to the seventh lens satisfy:

[0035] 1.72≤n1≤1.94, 21≤v1≤51;

[0036] 1.63≤n²≤1.88, 45≤v²≤60;

[0037] 1.81≤n3≤2.02,19≤v3≤36;

[0038] 1.52≤n4≤1.72, 55≤v4≤69;

[0039] 1.75≤n5≤1.95, 18≤v5≤29;

[0040] 1.40≤n6≤1.60, 80≤v6≤86;

[0041] 1.58≤n7≤1.78, 26≤v7≤36;

[0042] Wherein, n1 is the refractive index of the first lens, v1 is the Abbe number of the first lens, n2 is the refractive index of the second lens, v2 is the Abbe number of the second lens, n3 is the refractive index of the third lens, v3 is the Abbe number of the third lens, n4 is the refractive index of the fourth lens, v4 is the Abbe number of the fourth lens, n5 is the refractive index of the fifth lens, v5 is the Abbe number of the fifth lens, n6 is the refractive index of the sixth lens, v6 is the Abbe number of the sixth lens, n7 is the refractive index of the seventh lens, v7 is the Abbe number of the seventh lens.

[0043] Optionally, the radius of curvature and center thickness of the second lens satisfy:

[0044] 0.6≤RS3 / (RS4+d2)≤1.0;

[0045] Where RS3 is the radius of curvature of the object side of the second lens, RS4 is the radius of curvature of the image side of the second lens, and d2 is the center thickness of the second lens.

[0046] Optionally, the radius of curvature of the fifth lens satisfies:

[0047] -0.1≤RS11 / RS10≤0.2;

[0048] Wherein, RS10 is the radius of curvature of the object side of the fifth lens, and RS11 is the radius of curvature of the image side of the fifth lens.

[0049] Optionally, the object-side optical aperture D of the first lens and the image height ImgH corresponding to the maximum field of view of the fixed-focus lens satisfy the following:

[0050] 1.37≤D / ImgH≤1.62.

[0051] Optionally, the optical back focal length (BFL) of the fixed-focus lens and the lens group length (TL) satisfy the following:

[0052] 0≤BFL / TL≤0.2.

[0053] The technical solution of this utility model uses a fixed-focus lens composed of seven lenses with optical power, and reasonably allocates the optical power of each lens. The total optical system length (TTL) and entrance pupil diameter (ENPD) of the fixed-focus lens are set to satisfy TTL / ENPD≤13, so that the fixed-focus lens can have high imaging resolution while meeting the requirements of small size and large aperture, thereby broadening the application field of fixed-focus lenses. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided by this utility model;

[0055] Figure 2 yes Figure 1 The diagram shows the field curvature distortion curve of a fixed-focus lens;

[0056] Figure 3 yes Figure 1 The diagram shows the axial aberration curve of a fixed-focus lens.

[0057] Figure 4 yes Figure 1 The diagram shows the light fan of a fixed-focus lens;

[0058] Figure 5 This utility model provides a schematic diagram of the structure of another fixed-focus lens;

[0059] Figure 6 yes Figure 5 The diagram shows the field curvature distortion curve of a fixed-focus lens;

[0060] Figure 7 yes Figure 5 The diagram shows the axial aberration curve of a fixed-focus lens.

[0061] Figure 8 yes Figure 5 The diagram shows the light fan of a fixed-focus lens;

[0062] Figure 9 This utility model provides a structural schematic diagram of another fixed-focus lens;

[0063] Figure 10 yes Figure 9 The diagram shows the field curvature distortion curve of a fixed-focus lens;

[0064] Figure 11 yes Figure 9 The diagram shows the axial aberration curve of a fixed-focus lens.

[0065] Figure 12 yes Figure 9 The diagram shows the light fan of a fixed-focus lens. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be fully described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Various modifications and variations can be made to this utility model without departing from its spirit or scope, which is obvious to those skilled in the art. Therefore, this utility model is intended to cover modifications and variations of this utility model that fall within the scope of the corresponding claims (the claimed technical solutions) and their equivalents.

[0067] Furthermore, the terms "first," "second," and similar terms used in the embodiments of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, terms such as "an," "one," or "the" do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "including" or "comprising" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described object changes. In addition, descriptions of "same" or "equal" in the embodiments of this disclosure do not mean that two objects are completely equal in size or shape; they are allowed to be approximately the same or approximately equal within a certain error range.

[0068] It should be noted that the implementation methods provided in this utility model embodiment can be combined with each other without contradiction.

[0069] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in an embodiment of this utility model, as shown below. Figure 1 As shown, the fixed-focus lens includes: a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, a sixth lens 60, and a seventh lens 70 arranged sequentially along the optical axis from the object side to the image side; the first lens 10 has negative optical power; the second lens 20 has positive optical power; the third lens 30 has positive optical power; the fourth lens 40 has positive optical power; the fifth lens 50 has negative optical power; the sixth lens 60 has positive optical power; and the seventh lens 70 has positive optical power.

[0070] As can be understood, optical power equals the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. When optical power is positive, the refraction of light is converging; when optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group).

[0071] In this embodiment, each of the lenses from the first lens 10 to the seventh lens 70 can be fixed in one lens barrel. Figure 1Within the structure (not shown), by setting the first lens 10 to have negative optical power, the fixed-focus lens has a large field of view; setting the second lens 20 to have positive optical power, it can correct spherical aberration and coma of the light passing through the first lens, improving image sharpness and resolution; setting the third lens 30 to have positive optical power, it facilitates smoother light passing through the system, making it easier to correct field curvature and astigmatism, improving image sharpness and quality; setting the fourth lens 40 to have positive optical power and the fifth lens 50 to have negative optical power, it facilitates smoother light passing through the optical system of the fixed-focus lens, while increasing the imaging area of ​​the fixed-focus lens, improving image sharpness and quality; setting the sixth lens 60 to have positive optical power, it helps to balance various aberrations generated by the fifth lens 50, improving the imaging quality of the fixed-focus lens optical system; setting the seventh lens 70 to have positive optical power helps to collect light, ensure light transmission, improve relative illumination, and further balance various aberrations introduced by the preceding lenses, improving the optical performance of the entire fixed-focus lens optical system. In this way, by rationally allocating the optical power of each lens, the fixed-focus lens can achieve high imaging resolution while also having the characteristics of large aperture and small volume, and it is conducive to achieving good temperature characteristics, ensuring that the fixed-focus lens can still maintain good resolution under high and low temperature conditions.

[0072] In an optional embodiment, the optical power of the first lens 10 to the seventh lens 70 satisfies: -0.7≤Φ1 / Φ≤-0.3; 0≤Φ2 / Φ≤0.2; 0≤Φ3 / Φ≤0.4; 0.2≤Φ4 / Φ≤0.6; -0.9≤Φ5 / Φ≤-0.5; 0.4≤Φ6 / Φ≤0.8; 0≤Φ7 / Φ≤0.2; where Φ1 is the optical power of the first lens 10, Φ2 is the optical power of the second lens 20, Φ3 is the optical power of the third lens 30, Φ4 is the optical power of the fourth lens 40, Φ5 is the optical power of the fifth lens 50, Φ6 is the optical power of the sixth lens 60, Φ7 is the optical power of the seventh lens 70, and Φ is the optical power of the fixed-focus lens.

[0073] Specifically, setting the optical power Φ1 of the first lens 10 to a range of -0.7 ≤ Φ1 / Φ ≤ -0.3 helps to expand the field of view of the fixed-focus lens; setting the optical power Φ2 of the second lens 20 to a range of 0 ≤ Φ2 / Φ ≤ 0.2 helps to correct spherical aberration and coma introduced by the previous lens, improving image sharpness and quality; setting the optical power Φ3 of the third lens 30 to a range of 0 ≤ Φ3 / Φ ≤ 0.4 facilitates smoother light transmission through the fixed-focus lens's optical system, making it easier to correct field curvature and astigmatism, and improving image sharpness and quality; setting the optical power Φ4 of the fourth lens 40 to a range of 0.2 ≤ Φ4 / Φ ≤ 0.6, in conjunction with the optical power ranges of the other lenses, enables the fixed-focus lens to have good temperature characteristics, ensuring the lens's stability. The fixed-focus lens maintains good resolution even under high and low temperature conditions. By setting the optical power Φ5 of the fifth lens 50 to a range of -0.9≤Φ5 / Φ≤-0.5, light passes through the optical system of the fixed-focus lens more smoothly, while increasing the imaging area of ​​the fixed-focus lens and improving image sharpness and quality. By setting the optical power Φ6 of the sixth lens 60 to a range of 0.4≤Φ6 / Φ≤0.8, various aberrations generated by the fifth lens 50 are balanced, improving the imaging quality of the optical system. By setting the optical power Φ7 of the seventh lens 70 to a range of 0≤Φ7 / Φ≤0.2, the optical system of the fixed-focus lens can better collect light, ensure the light transmission of the fixed-focus lens, improve relative illumination, and further balance various aberrations introduced by the preceding lenses, thus improving the optical performance of the entire optical system.

[0074] In an optional embodiment of this utility model, the optical power of the third lens 30 and the fourth lens 40 can satisfy: 0.4≤Φ3 / Φ4≤0.8; where Φ3 is the optical power of the third lens 30 and Φ4 is the optical power of the fourth lens 40.

[0075] In this embodiment, by setting the ratio of the optical power Φ3 of the third lens 30 to the optical power Φ4 of the fourth lens 40 to a range of 0.4≤Φ3 / Φ4≤0.8, the light path between the third lens 30 and the fourth lens 40 can be adjusted, the generation of aberrations can be suppressed, and the clarity and quality of the image can be improved. At the same time, the assembly sensitivity can also be reduced.

[0076] Optionally, the optical power of the fifth lens 50 and the sixth lens 60 shall satisfy: -1.6≤Φ5 / Φ6≤-1; where Φ5 is the optical power of the fifth lens 50 and Φ6 is the optical power of the sixth lens 60.

[0077] In this embodiment, by setting the ratio of the optical power Φ5 of the fifth lens 50 to the optical power Φ6 of the sixth lens 60 to a range of -1.6≤Φ5 / Φ6≤-1, the light path between the fifth lens 50 and the sixth lens 60 can be controlled, which helps to reduce aberrations caused by large angles and also helps to reduce the overall size of the fixed-focus lens, thus contributing to the miniaturization of the fixed-focus lens.

[0078] In another optional embodiment, the focal lengths of the first lens 10 to the seventh lens 70 satisfy: -3 < f1 / f < -1.5; 40 < f2 / f < 60; 3.5 < f3 / f < 4.85; 2.1 < f4 / f < 3.1; -1.4 < f5 / f < -1.15; 1.46 < f6 / f < 1.86; f1 is the focal length of the first lens 10, f2 is the focal length of the second lens 20, f3 is the focal length of the third lens 30, f4 is the focal length of the fourth lens 40, f5 is the focal length of the fifth lens 50, f6 is the focal length of the sixth lens 60, and f is the effective focal length of the fixed-focus lens.

[0079] Specifically, by setting the focal length f1 of the first lens 10 to a negative value, and ensuring that the focal length f1 of the first lens 10 satisfies -3 < f1 / f < -1.5 with the effective focal length f of the fixed-focus lens, it is beneficial to expand the field of view of the fixed-focus lens; by setting the focal length f2 of the second lens 20 to a positive value, and ensuring that the focal length f2 of the second lens 20 satisfies 40 < f2 / f < 60 with the effective focal length f of the fixed-focus lens, it is beneficial to correct the spherical aberration and coma introduced by the previous lens, thereby improving the sharpness and quality of the image; by setting the focal length f3 of the third lens 30 to a positive value, and ensuring that the focal length f3 of the third lens 30 satisfies 3.5 < f3 / f < 4.85 with the effective focal length f of the fixed-focus lens, it is beneficial to allow light to pass through the system more smoothly, making it easier to correct field curvature and astigmatism, thereby improving the sharpness and quality of the image; by setting the focal length f5 of the fifth lens 50 to a negative value, and ensuring that the focal length f1 of the fifth lens 50 satisfies -3 < f1 / f < -1.5 with the effective focal length f of the fixed-focus lens, it is beneficial to expand the field of view of the fixed-focus lens; by setting the focal length f5 of the fifth lens 50 to a negative value, and ensuring that the focal length f2 of the second lens 20 satisfies 40 < f2 / f < 60 with the effective focal length f of the fixed-focus lens, it is beneficial to correct the spherical aberration and coma introduced by the previous lens, thereby improving the sharpness and quality of the image; by setting the focal length f5 of the fifth lens 50 to a negative value, and ensuring that the focal length f2 of the second lens 50 satisfies 40 < f2 / f < 60 with the effective The focal length f5 of the 50mm lens satisfies -1.4 < f5 / f < -1.15 with the effective focal length f of the fixed-focus lens, which facilitates smoother light transmission through the system and increases the imaging area of ​​the optical lens, improving image sharpness and quality. By setting the focal length f6 of the sixth lens 60 to a positive value and ensuring that the focal length f6 of the sixth lens 60 satisfies 1.46 < f6 / f < 1.86 with the effective focal length f of the fixed-focus lens, it helps to balance various aberrations generated by the fifth lens and improve the imaging quality of the optical system. In addition, by setting the focal length f4 of the fourth lens 40 to a positive value and ensuring that the focal length f4 of the fourth lens 40 satisfies 2.1 < f4 / f < 3.1 with the effective focal length f of the fixed-focus lens, the focal length of the entire optical system of the fixed-focus lens can be reasonably allocated, which helps to achieve good temperature characteristics and ensures that the fixed-focus lens can maintain good resolution under high and low temperature conditions.

[0080] In an alternative embodiment, the fifth lens 50 and the sixth lens 60 may form a cemented lens.

[0081] By using a cemented lens to combine the fifth lens 50 and the sixth lens 60, the air gap between them can be reduced, thus helping to decrease the overall length of the fixed-focus lens. Simultaneously, the cemented lens can minimize or eliminate chromatic aberration, allowing for sufficient correction of various aberrations in the fixed-focus lens. This improves resolution and optimizes optical performance such as distortion while maintaining a compact structure. It also reduces light loss caused by reflections between lens elements, increasing illumination and thus improving image quality and sharpness. Furthermore, the use of a cemented lens reduces the number of assembly components between the two lenses, simplifying the assembly process in fixed-focus lens manufacturing, reducing costs, and minimizing tolerance sensitivity issues such as tilting / eccentricity of lens units during assembly.

[0082] Optionally, the total optical system length (TTL) of a fixed-focus lens and the entrance pupil diameter (EPD) must satisfy the following relationship: TTL / EPD≤13.

[0083] In this embodiment, by setting the ratio of the total optical system length (TTL) to the entrance pupil diameter (EPD) of the fixed-focus lens to less than 13, the fixed-focus lens can meet the characteristics of a smaller total optical system length (TTL) and a larger entrance pupil diameter (EPD). This allows the fixed-focus lens to achieve a smaller relative aperture (FNO), which is beneficial for the fixed-focus lens to achieve large aperture characteristics and provide more incident light to the fixed-focus lens.

[0084] Optionally, the optical aperture D of the object side of the first lens 10 and the image height ImgH corresponding to the maximum field of view of the fixed-focus lens satisfy: 1.37≤D / ImgH≤1.62.

[0085] In this embodiment, by setting the image height ImgH corresponding to the object-side optical aperture D of the first lens 10 and the maximum field of view of the fixed-focus lens to 1.37≤D / ImgH≤1.62, it is beneficial to the miniaturization design of the fixed-focus lens optical system. At the same time, it is also beneficial to the fixed-focus lens light system to have the characteristics of high pixel and high resolution, thereby enabling the fixed-focus lens to meet the requirements of high imaging quality.

[0086] Optionally, the optical back focal length (BFL) of a fixed-focus lens and the lens group length (TL) satisfy the following condition: 0 ≤ BFL / TL ≤ 0.2.

[0087] In this embodiment, by setting the ratio between the optical back focal length (BFL) and the lens group length (TL) of the fixed focal length lens to a range of 0 ≤ BFL / TL ≤ 0.2, it is possible to achieve a longer back focal length for the fixed focal length lens while miniaturizing it. This is beneficial for the assembly of the lenses and modules of the fixed focal length lens, thereby improving production efficiency and reducing the production cost of the fixed focal length lens.

[0088] Optionally, the total optical system length (TTL) of a fixed-focus lens and the effective focal length (f) of the fixed-focus lens satisfy the following condition: 7.2 < TTL / f < 8.3.

[0089] By limiting the relationship between the total optical length and the effective focal length of a fixed-focus lens, it is possible to control the total length of the optical system of the fixed-focus lens while satisfying the field of view range, thus enabling the fixed-focus lens to meet the characteristics of miniaturization.

[0090] Optionally, the entrance pupil diameter EPD of the fixed-focus lens and the image height IH of the fixed-focus lens at the maximum field of view satisfy the following condition: 3.5 < IH / EPD < 4.

[0091] Optionally, the effective focal length f of the fixed focal length lens, the maximum field of view (FOV) of the fixed focal length lens, and the image height IH of the fixed focal length lens at the maximum field of view satisfy: (IH / 2) / (f×tan(FOV / 2)<0.6).

[0092] This setting allows for a smaller relative aperture (FNO), which is beneficial for achieving large aperture characteristics and providing more incident light for fixed-focus lenses.

[0093] Optionally, the object-side surface of the first lens 10 is convex, and the image-side surface is concave; the object-side surface of the second lens 20 is concave, and the image-side surface is convex; the object-side surface of the third lens 30 is convex, and the image-side surface is concave or flat; the object-side surface of the fourth lens 40 is convex, and the image-side surface is convex; the object-side surface of the fifth lens 50 is concave or convex, and the image-side surface is concave; the object-side surface of the sixth lens 60 is convex, and the image-side surface is convex; and the object-side surface of the seventh lens 70 is convex, and the image-side surface is concave.

[0094] In this embodiment, the object-side surface of the lens can be understood as the surface of the lens closest to the object plane, and the image-side surface of the lens can be understood as the surface of the lens closest to the image plane. By rationally setting the shape of each lens, the miniaturization and large aperture requirements of the fixed-focus lens are met while ensuring clear image quality, allowing the fixed-focus lens to be applied in a wider range of scenarios.

[0095] Optionally, the refractive index and Abbe number of the first lens 10 to the seventh lens 70 satisfy the following: 1.72≤n1≤1.94, 21≤v1≤51; 1.63≤n2≤1.88, 45≤v2≤60; 1.81≤n3≤2.02, 19≤v3≤36; 1.52≤n4≤1.72, 55≤v4≤69; 1.75≤n5≤1.95, 18≤v5≤29; 1.40≤n6≤1.60, 80≤v6≤86; 1.58≤n7≤1.78, 26≤v7≤36; where n1 is the refractive index of the first lens 10 to the seventh lens 70. The refractive index of lens 10, v1 is the Abbe number of the first lens 10, n2 is the refractive index of the second lens 20, v2 is the Abbe number of the second lens 20, n3 is the refractive index of the third lens 30, v3 is the Abbe number of the third lens 30, n4 is the refractive index of the fourth lens 40, v4 is the Abbe number of the fourth lens 40, n5 is the refractive index of the fifth lens 50, v5 is the Abbe number of the fifth lens 50, n6 is the refractive index of the sixth lens 60, v6 is the Abbe number of the sixth lens 60, n7 is the refractive index of the seventh lens 70, v7 is the Abbe number of the seventh lens 70.

[0096] As we can understand, the refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium. It is mainly used to describe a material's ability to refract light. Different materials have different refractive indices, and the higher the refractive index of a material, the stronger its ability to refract incident light. The Abbe number is an index used to represent the dispersion ability of a transparent medium. The more severe the dispersion of the medium, the smaller the Abbe number; conversely, the less severe the dispersion of the medium, the larger the Abbe number.

[0097] In this embodiment, by adjusting the refractive index and Abbe number of the lens, it is beneficial to correct the positional chromatic aberration and magnification chromatic aberration of the optical system of the fixed-focus lens, improve the resolution of the fixed-focus lens, and at the same time reduce the sensitivity of the optical system of the fixed-focus lens, improve the yield, and thus reduce the production cost.

[0098] Optionally, the radius of curvature and center thickness of the second lens 20 satisfy: 0.6≤RS3 / (RS4+d2)≤1.0; where RS3 is the radius of curvature of the object side of the second lens 20, RS4 is the radius of curvature of the image side of the second lens 20, and d2 is the center thickness of the second lens 20.

[0099] In this embodiment, by limiting the relationship between the radius of curvature and the center thickness of the second lens 20 within the above-mentioned range, the shape of the second lens 20 can be made close to a concentric circle, so that there is an optical path difference between the peripheral light and the central light, and the central light is diverged and enters the rear optical system. This helps to reduce the front port diameter and volume of the fixed-focus lens, which is conducive to the miniaturization and low cost of the fixed-focus lens.

[0100] Optionally, the radius of curvature of the fifth lens 50 satisfies: -0.1≤RS11 / RS10≤0.2; where RS10 is the radius of curvature of the object side of the fifth lens 50, and RS11 is the radius of curvature of the image side of the fifth lens 50.

[0101] In this embodiment, by differentiating the curvature radii of the image side and the object side of the fifth lens 50, and ensuring that the ratio of the curvature radius RS11 of the image side to the curvature radius RS10 of the object side satisfies the above relationship, it is beneficial to reduce the optical axis eccentricity sensitivity and also beneficial to expand the width of the incident beam, thereby increasing the image plane height and enabling the system to have high pixel characteristics.

[0102] Based on the above embodiments, the fixed-focus lens may further include an aperture stop 80 and a filter 90; the aperture stop 80 is disposed in the optical path between the third lens 30 and the fourth lens 40; the filter 90 is disposed in the optical path between the seventh lens 70 and the image plane.

[0103] Specifically, the aperture 80 can adjust the propagation direction of the light beam, which is beneficial to improving image quality. Furthermore, in this fixed-focus lens, the aperture 80 is located in the optical path between the third lens 30 and the fourth lens 40. Positioning the aperture 80 in the middle of the fixed-focus lens ensures that the front and rear apertures of the lens are minimized. The filter 90 is disposed in the optical path between the seventh lens 70 and the image plane to filter out stray light and improve imaging performance. In an exemplary embodiment, the filter 90 can be an infrared filter.

[0104] In summary, this utility model embodiment uses seven lenses with optical power to form a fixed-focus lens. By rationally allocating the optical power of each lens and rationally selecting materials and designing the shape of each lens, the fixed-focus lens can simultaneously meet the requirements of small size, large aperture, high resolution, and high resolution, thereby broadening the application field of fixed-focus lenses.

[0105] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of a fixed-focus lens applicable to the above-described embodiments.

[0106] In one feasible embodiment, Table 1 details a feasible implementation method. Figure 1 The specific optical and physical parameters of the fixed-focus lens are shown.

[0107] Table 1. Design of optical physical parameters for a fixed-focus lens.

[0108] Example 1 lower limit upper limit Φ1 / Φ -0.533 -0.7 -0.3 Φ2 / Φ 0.015 0.0 0.2 Φ3 / Φ 0.236 0.0 0.4 Φ4 / Φ 0.372 0.2 0.6 Φ5 / Φ -0.729 -0.9 -0.5 Φ6 / Φ 0.596 0.4 0.8 Φ7 / Φ 0.012 0.0 0.2 Φ3 / Φ4 0.635 0.4 0.8 Φ5 / Φ6 -1.223 -1.6 -1.0 n1 1.800 1.72 1.94 n2 1.730 1.63 1.88 n3 1.900 1.81 2.02 n4 1.620 1.52 1.72 n5 1.850 1.75 1.95 n6 1.500 1.40 1.60 n7 1.680 1.58 1.78 v1 46.600 21 51 v2 54.700 45 60 v3 31.300 19 36 v4 63.900 55 69 v5 23.800 18 29 v6 81.600 80 86 v7 31.400 26 36 RS3 / (RS4+d2) 0.797 0.6 1.0 RS11 / RS10 0.069 -0.1 0.2 TTL / ENPD 12.520 13 D / ImgH 1.518 1.37 1.62 BEL / TL 0.126 0 0.2 f2 / f 65.3089 41 72 RS1 / RS2 4.1709 3.75 4.82 (f1+f2+f3) / f 67.6633 75 43 (RS6+RS8+RS9) / BFL +∞ 51 +∞

[0109] Table 2 shows the design parameters of each lens in a fixed-focus lens, including surface type, radius of curvature, thickness, and material, which correspond to those in Table 1.

[0110] Table 2. Parameter design of each lens in a fixed-focus lens.

[0111] Face number Face type radius of curvature / mm Thickness / mm Refractive index Abbe number OBJ surface Infinity Infinity S1 spherical 18.3635 1.0293 1.800 46.600 S2 spherical 4.4028 4.7991 S3 spherical -7.5997 5.7267 1.730 54.700 S4 spherical -9.6371 0.1000 S5 spherical 15.2318 3.1613 1.900 31.300 S6 spherical Infinity 0.2115 S7 Aperture Infinity 0.7812 S8 even aspherical surface 8.9342 3.9153 1.620 63.900 S9 even aspherical surface -21.4878 0.0999 S10 spherical 63.1149 0.9521 1.850 23.800 S11 spherical 4.3246 3.9008 1.500 81.600 S12 spherical -10.2909 0.0994 S13 even aspherical surface 13.1060 2.4815 1.680 31.400 S14 even aspherical surface 12.8319 0.8998 S15 spherical Infinity 0.8000 1.520 64.200 S16 spherical Infinity 1.7325 IMA spherical Infinity 0.0000

[0112] The fixed-focus lens of this embodiment includes a first lens 10, a second lens 20, a third lens 30, an aperture stop 80, a fourth lens 40, a fifth lens 50, a sixth lens 60, a seventh lens 70, and a filter glass 90 arranged sequentially along the optical axis from the object side to the image side. The surface numbers are assigned according to the surface order of each lens, where "S1" represents the object side of the first lens, "S2" represents the image side of the first lens, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Infinity" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the axial distance between the central surfaces of the current and next surfaces. The refractive index represents the ability of the material between the current and next surfaces to deflect light. The Abbe number represents the dispersion characteristics of the material between the current and next surfaces.

[0113] The aspherical surface shape of the fixed-focus lens in this embodiment can be defined by the following aspherical formula, but is not limited to the following representation:

[0114]

[0115] Where Z is the axial sagitta of the aspherical surface, c is the fundamental curvature at the vertex of the aspherical surface, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and A, B, C, D, E, F, and G correspond to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order terms of the aspherical polynomial, respectively.

[0116] Table 3 Aspherical coefficients of a fixed-focus lens

[0117] S8 S9 S13 S14 k 7.93E-01 -4.18E+00 1.44E+00 3.25E-01 A -3.75E-04 2.44E-05 -1.42E-03 -1.62E-03 B -1.04E-05 -5.44E-05 -1.28E-05 -3.41E-05 C 1.32E-06 1.33E-05 7.40E-07 2.56E-06 D -1.96E-07 -1.62E-06 -7.41E-08 -8.21E-08 E 7.51E-09 7.02E-08 5.49E-09 6.12E-11 F 1.77E-15 -2.16E-13 -2.88E-11 1.05E-10 G 6.52E-16 -1.55E-13 -1.08E-12 -1.67E-12

[0118] Where -3.75E-04 indicates that the coefficient A of surface number S8 is -3.75 × 10⁻⁴. -4 .

[0119] Figure 2 yes Figure 1 The diagram shown illustrates the field curvature distortion curve of a fixed-focus lens, as follows: Figure 2 As shown in the figure, the curves of different colors represent different wavelengths (656nm, 588nm, 546nm, 486nm, 436nm) for system imaging. Figure 2 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.03mm to 0.03mm, indicating that the fixed-focus lens can correct the field curvature well.

[0120] Figure 3 yes Figure 1 The schematic diagram of the axial aberration curve of the fixed-focus lens shown is as follows: Figure 3 As shown in the figure, the curves of different colors represent different wavelengths (656nm, 588nm, 546nm, 486nm, 436nm) for system imaging. Figure 3 As can be seen, the axial aberration offset is controlled within ±0.02mm, indicating that the fixed-focus lens can correct axial aberration well.

[0121] Figure 4 yes Figure 1 The diagram shown illustrates the light fan of a fixed-focus lens, as follows: Figure 4 As shown, the diagrams illustrate the ray fan at different field of view angles (0.00°, 10.00°, 20.00°, 30.00°, 40.00°, 50.00°, 60.00°, and 70.00°). In each field of view angle, different colored curves represent different wavelengths of the system's imaging (656nm, 588nm, 546nm, 486nm, and 436nm). Figure 4 As can be seen, the deviation of the light rays from the principal ray coordinates is controlled within ±25um, indicating that the fixed-focus lens can control aberrations well.

[0122] In another feasible embodiment, Figure 5 This is a schematic diagram of another fixed-focus lens provided in this embodiment of the present invention. Table 4 describes in detail another feasible implementation method. Figure 5 The specific optical and physical parameters of the fixed-focus lens are shown.

[0123] Table 4. Another optical physical parameter design for fixed-focus lenses

[0124] Example 2 lower limit upper limit Φ1 / Φ -0.551 -0.7 -0.3 Φ2 / Φ 0.017 0.0 0.2 Φ3 / Φ 0.247 0.0 0.4 Φ4 / Φ 0.378 0.2 0.6 Φ5 / Φ -0.829 -0.9 -0.5 Φ6 / Φ 0.607 0.4 0.8 Φ7 / Φ 0.062 0.0 0.2 Φ3 / Φ4 0.654 0.4 0.8 Φ5 / Φ6 -1.365 -1.6 -1.0 n1 1.835 1.72 1.94 n2 1.775 1.63 1.88 n3 1.916 1.81 2.02 n4 1.617 1.52 1.72 n5 1.856 1.75 1.95 n6 1.495 1.40 1.60 n7 1.683 1.58 1.78 v1 36.185 21 51 v2 55.101 45 60 v3 23.998 19 36 v4 63.862 55 69 v5 21.995 18 29 v6 81.381 80 86 v7 31.440 26 36 RS3 / (RS4+d2) 0.794 0.6 1.0 RS11 / RS10 -0.007 -0.1 0.2 TTL / ENPD 12.483 13 D / ImgH 1.468 1.37 1.62 BEL / TL 0.156 0 0.2 f2 / f 58.6357 41 72 RS1 / RS2 4.3420 3.75 4.82 (f1+f2+f3) / f 60.8669 75 43 (RS6+RS8+RS9) / BFL 83.2664 51 +∞

[0125] Table 5 shows the design parameters of each lens in another fixed-focus lens corresponding to Table 4, including surface type, radius of curvature, thickness, and material.

[0126] Table 5. Another parameter design for each lens in a fixed-focus lens.

[0127] Face number Face type radius of curvature / mm Thickness / mm Refractive index Abbe number OBJ surface Infinity Infinity S1 spherical 19.9724 0.9000 1.835 36.185 S2 spherical 4.5998 5.1959 S3 spherical -7.4941 5.8007 1.775 55.101 S4 spherical -9.6401 0.2014 S5 spherical 14.4997 2.2291 1.916 23.998 S6 spherical 358.5201 0.0800 S7 Aperture Infinity 1.1402 S8 even aspherical surface 9.1338 3.8605 1.617 63.862 S9 even aspherical surface -19.9485 0.1019 S10 spherical -607.6665 0.9549 1.856 21.995 S11 spherical 4.2307 3.9941 1.495 81.381 S12 spherical -10.1463 0.0974 S13 even aspherical surface 13.8881 2.2788 1.683 31.440 S14 even aspherical surface 18.7843 0.9000 S15 spherical Infinity 0.8000 1.517 64.199 S16 spherical Infinity 2.4758 IMA spherical Infinity 0.0000

[0128] The fixed-focus lens of this embodiment includes a first lens 10, a second lens 20, a third lens 30, an aperture stop 80, a fourth lens 40, a fifth lens 50, a sixth lens 60, a seventh lens 70, and a filter glass 90 arranged sequentially along the optical axis from the object side to the image side. The surface numbers are assigned according to the surface order of each lens, where "S1" represents the object side of the first lens, "S2" represents the image side of the first lens, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Infinity" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the axial distance between the central surfaces of the current and next surfaces. The refractive index represents the ability of the material between the current and next surfaces to deflect light. The Abbe number represents the dispersion characteristics of the material between the current and next surfaces.

[0129] The aspherical surface shape of the fixed-focus lens in this embodiment can be defined by the following aspherical formula, but is not limited to the following representation:

[0130]

[0131] Where Z is the axial sagitta of the aspherical surface, c is the fundamental curvature at the vertex of the aspherical surface, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and A, B, C, D, E, F, and G correspond to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order terms of the aspherical polynomial, respectively.

[0132] Table 6 Aspherical coefficients of another type of fixed-focus lens

[0133] S8 S9 S13 S14 k 6.14E-01 5.30E+00 1.15E+00 6.97E-01 A -4.08E-04 -1.38E-04 -1.45E-03 -1.61E-03 B -1.42E-05 -5.36E-05 -1.14E-05 -2.18E-05 C 1.03E-06 1.27E-05 1.02E-06 2.96E-06 D -1.85E-07 -1.81E-06 -6.24E-08 -1.84E-07 E 9.03E-09 1.06E-07 9.73E-10 1.81E-09 F 1.78E-10 8.15E-10 3.47E-10 3.95E-10 G -2.56E-11 -2.66E-10 -1.14E-11 -1.25E-11

[0134] Where -4.08E-04 indicates that the coefficient A of surface number S8 is -4.08 × 10⁻⁴. -4 .

[0135] Figure 6 yes Figure 5 The diagram shown illustrates the field curvature distortion curve of a fixed-focus lens, as follows: Figure 6 As shown in the figure, the curves of different colors represent different wavelengths (656nm, 588nm, 546nm, 486nm, 436nm) for system imaging. Figure 6 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.03mm to 0.04mm, indicating that the fixed-focus lens can correct the field curvature well.

[0136] Figure 7 yes Figure 5 The schematic diagram of the axial aberration curve of the fixed-focus lens shown is as follows: Figure 7As shown in the figure, the curves of different colors represent different wavelengths (656nm, 588nm, 546nm, 486nm, 436nm) for system imaging. Figure 7 As can be seen, the axial aberration offset is controlled within ±0.02mm, indicating that the fixed-focus lens can correct axial aberration well.

[0137] Figure 8 yes Figure 5 The diagram shown illustrates the light fan of a fixed-focus lens, as follows: Figure 8 As shown, the diagrams illustrate the ray fan at different field of view angles (0.00°, 10.00°, 20.00°, 30.00°, 40.00°, 50.00°, 60.00°, and 70.00°). In each field of view angle, different colored curves represent different wavelengths of the system's imaging (656nm, 588nm, 546nm, 486nm, and 436nm). Figure 8 As can be seen, the deviation of the light rays from the principal ray coordinates is controlled within ±25um, indicating that the fixed-focus lens can control aberrations well.

[0138] In yet another feasible embodiment, Figure 9 This is a schematic diagram of another fixed-focus lens provided in this embodiment of the present invention. Table 7 describes in detail another feasible implementation method. Figure 9 The specific optical and physical parameters of the fixed-focus lens are shown.

[0139] Table 7. Another optical physical parameter design for fixed-focus lenses.

[0140] Example 3 lower limit upper limit Φ1 / Φ -0.542 -0.7 -0.3 Φ2 / Φ 0.022 0.0 0.2 Φ3 / Φ 0.222 0.0 0.4 Φ4 / Φ 0.382 0.2 0.6 Φ5 / Φ -0.733 -0.9 -0.5 Φ6 / Φ 0.580 0.4 0.8 Φ7 / Φ 0.029 0.0 0.2 Φ3 / Φ4 0.580 0.4 0.8 Φ5 / Φ6 -1.263 -1.6 -1.0 n1 1.816 1.72 1.94 n2 1.729 1.63 1.88 n3 1.906 1.81 2.02 n4 1.616 1.52 1.72 n5 1.847 1.75 1.95 n6 1.495 1.40 1.60 n7 1.683 1.58 1.78 v1 39.373 21 51 v2 50.000 45 60 v3 26.370 19 36 v4 60.276 55 69 v5 22.344 18 29 v6 84.963 80 86 v7 31.440 26 36 RS3 / (RS4+d2) 0.802 0.6 1.0 RS11 / RS10 0.065 -0.1 0.2 TTL / ENPD 12.477 13 D / ImgH 1.501 1.37 1.62 BEL / TL 0.135 0 0.2 f2 / f 45.9005 41 72 RS1 / RS2 4.3226 3.75 4.82 (f1+f2+f3) / f 48.5670 75 43 (RS6+RS8+RS9) / BFL 56.6585 51 +∞

[0141] Table 8 shows the design parameters of the surface type, radius of curvature, thickness, and material of each lens in another type of fixed-focus lens, corresponding to Table 7.

[0142] Table 8. Another parameter design for each lens in a fixed-focus lens.

[0143] Face number Face type radius of curvature / mm Thickness / mm Refractive index Abbe number OBJ surface Infinity Infinity S1 spherical 19.6206 0.9638 1.816 39.373 S2 spherical 4.5390 4.9321 S3 spherical -7.5893 5.8715 1.729 50.000 S4 spherical -9.5354 0.0670 S5 spherical 15.4657 2.2000 1.906 26.370 S6 spherical 219.3440 0.3976 S7 Aperture Infinity 1.0954 S8 even aspherical surface 8.9714 3.8913 1.616 60.276 S9 even aspherical surface -19.6043 0.0999 S10 spherical 66.6363 0.9521 1.847 22.344 S11 spherical 4.3504 4.2650 1.495 84.963 S12 spherical -10.9812 0.0636 S13 even aspherical surface 13.5599 2.4273 1.683 31.440 S14 even aspherical surface 14.6344 0.7823 S15 spherical Infinity 0.8000 1.519 64.199 S16 spherical Infinity 2.1014 IMA spherical Infinity 0.0000

[0144] The fixed-focus lens of this embodiment includes a first lens 10, a second lens 20, a third lens 30, an aperture stop 80, a fourth lens 40, a fifth lens 50, a sixth lens 60, a seventh lens 70, and a filter glass 90 arranged sequentially along the optical axis from the object side to the image side. The surface numbers are assigned according to the surface order of each lens, where "S1" represents the object side of the first lens, "S2" represents the image side of the first lens, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Infinity" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the axial distance between the central surfaces of the current and next surfaces. The refractive index represents the ability of the material between the current and next surfaces to deflect light. The Abbe number represents the dispersion characteristics of the material between the current and next surfaces.

[0145] The aspherical surface shape of the fixed-focus lens in this embodiment can be defined by the following aspherical formula, but is not limited to the following representation:

[0146]

[0147] Where Z is the axial sagitta of the aspherical surface, c is the fundamental curvature at the vertex of the aspherical surface, k is the conic section constant, r is the radial coordinate perpendicular to the optical axis, and A, B, C, D, E, F, and G correspond to the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order terms of the aspherical polynomial, respectively.

[0148] Table 9 shows the aspherical coefficient of another type of fixed-focus lens.

[0149] S8 S9 S13 S14 k 5.74E-01 4.21E+00 5.15E-01 -4.72E-01 A -4.15E-04 -1.12E-04 -1.47E-03 -1.69E-03 B -1.31E-05 -4.31E-05 -5.97E-06 -1.51E-05 C 1.07E-06 1.24E-05 -8.22E-07 9.44E-07 D -1.84E-07 -1.88E-06 6.98E-08 -1.74E-08 E 8.91E-09 9.12E-08 -1.69E-09 -1.02E-09 F 1.87E-10 5.32E-09 -8.98E-11 5.95E-11 G -2.58E-11 -5.17E-10 1.01E-11 4.28E-13

[0150] Where -4.15E-04 indicates that the coefficient A of surface number S8 is -4.15 × 10⁻⁴. -4 .

[0151] Figure 10 yes Figure 9 The diagram shown illustrates the field curvature distortion curve of a fixed-focus lens, as follows: Figure 10 As shown in the figure, the curves of different colors represent different wavelengths (656nm, 588nm, 546nm, 486nm, 436nm) for system imaging. Figure 10 As can be seen, the field curvature of the meridional and sagittal image planes is controlled within -0.03mm to 0.04mm, indicating that the fixed-focus lens can correct the field curvature well.

[0152] Figure 11 yes Figure 9 The schematic diagram of the axial aberration curve of the fixed-focus lens shown is as follows: Figure 11As shown in the figure, the curves of different colors represent different wavelengths (656nm, 588nm, 546nm, 486nm, 436nm) for system imaging. Figure 11 As can be seen, the axial aberration offset is controlled within ±0.02mm, indicating that the fixed-focus lens can correct axial aberration well.

[0153] Figure 12 yes Figure 9 The diagram shown illustrates the light fan of a fixed-focus lens, as follows: Figure 12 As shown, the diagrams illustrate the ray fan at different field of view angles (0.00°, 10.00°, 20.00°, 30.00°, 40.00°, 50.00°, 60.00°, and 70.00°). In each field of view angle, different colored curves represent different wavelengths of the system's imaging (656nm, 588nm, 546nm, 486nm, and 436nm). Figure 12 As can be seen, the deviation of the light rays from the principal ray coordinates is controlled within ±25um, indicating that the fixed-focus lens can control aberrations well.

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

Claims

1. A fixed-focus lens, characterized in that, include: The first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, and seventh lens are arranged sequentially along the optical axis from the object side to the image side. The first lens has negative optical power; the second lens has positive optical power; the third lens has positive optical power; the fourth lens has positive optical power; the fifth lens has negative optical power; the sixth lens has positive optical power; and the seventh lens has positive optical power. The total optical system length (TTL) of the fixed-focus lens satisfies the following relationship with the entrance pupil diameter (EPD): TTL / EPD≤13.

2. The fixed-focus lens according to claim 1, characterized in that, The total optical system length TTL of the fixed-focus lens and the effective focal length f of the fixed-focus lens satisfy the following condition: 7.2 < TTL / f < 8.

3.

3. The fixed-focus lens according to claim 1, characterized in that, The entrance pupil diameter EPD of the fixed-focus lens and the image height IH of the fixed-focus lens at the maximum field of view satisfy the following condition: 3.5 < IH / EPD < 4.

4. The fixed-focus lens according to claim 1, characterized in that, The effective focal length f of the fixed-focus lens, the maximum field of view (FOV) of the fixed-focus lens, and the image height IH of the fixed-focus lens at the maximum field of view satisfy: (IH / 2) / (f×tan(FOV / 2)<0.6).

5. The fixed-focus lens according to claim 1, characterized in that, The optical power of the third lens and the fourth lens satisfies: 0.4≤Φ3 / Φ4≤0.8; Wherein, Φ3 is the optical power of the third lens, and Φ4 is the optical power of the fourth lens.

6. The fixed-focus lens according to claim 1, characterized in that, The optical power of the fifth lens and the sixth lens satisfies: -1.6≤Φ5 / Φ6≤-1; Wherein, Φ5 is the optical power of the fifth lens, and Φ6 is the optical power of the sixth lens.

7. The fixed-focus lens according to claim 1, characterized in that, The optical power of the first lens to the seventh lens satisfies: -0.7≤Φ1 / Φ≤-0.3; 0≤Φ2 / Φ≤0.2; 0≤Φ3 / Φ≤0.4; 0.2≤Φ4 / Φ≤0.6; -0.9≤Φ5 / Φ≤-0.5; 0.4≤Φ6 / Φ≤0.8; 0≤Φ7 / Φ≤0.2; Φ1 is the optical power of the first lens, Φ2 is the optical power of the second lens, Φ3 is the optical power of the third lens, Φ4 is the optical power of the fourth lens, Φ5 is the optical power of the fifth lens, Φ6 is the optical power of the sixth lens, Φ7 is the optical power of the seventh lens, and Φ is the optical power of the fixed-focus lens.

8. The fixed-focus lens according to claim 1, characterized in that, The focal lengths of the first lens to the seventh lens satisfy the following: -3 < f1 / f < -1.5; 40 < f² / f < 60; 3.5 < f3 / f < 4.85; 2.1 < f4 / f < 3.1; -1.4 < f5 / f < -1.15; 1.46 < f6 / f < 1.86; f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, and f is the effective focal length of the fixed-focus lens.

9. The fixed-focus lens according to claim 1, characterized in that, The refractive indices and Abbe numbers of the first to the seventh lenses satisfy: 1.72≤n1≤1.94, 21≤v1≤51; 1.63≤n²≤1.88, 45≤v²≤60; 1.81≤n3≤2.02,19≤v3≤36; 1.52≤n4≤1.72, 55≤v4≤69; 1.75≤n5≤1.95, 18≤v5≤29; 1.40≤n6≤1.60, 80≤v6≤86; 1.58≤n7≤1.78, 26≤v7≤36; Wherein, n1 is the refractive index of the first lens, v1 is the Abbe number of the first lens, n2 is the refractive index of the second lens, v2 is the Abbe number of the second lens, n3 is the refractive index of the third lens, v3 is the Abbe number of the third lens, n4 is the refractive index of the fourth lens, v4 is the Abbe number of the fourth lens, n5 is the refractive index of the fifth lens, v5 is the Abbe number of the fifth lens, n6 is the refractive index of the sixth lens, v6 is the Abbe number of the sixth lens, n7 is the refractive index of the seventh lens, v7 is the Abbe number of the seventh lens.

10. The fixed-focus lens according to claim 1, characterized in that, The radius of curvature and center thickness of the second lens satisfy: 0.6≤RS3 / (RS4+d2)≤1.0; Where RS3 is the radius of curvature of the object side of the second lens, RS4 is the radius of curvature of the image side of the second lens, and d2 is the center thickness of the second lens.

11. The fixed-focus lens according to claim 1, characterized in that, The radius of curvature of the fifth lens satisfies: -0.1≤RS11 / RS10≤0.2; Wherein, RS10 is the radius of curvature of the object side of the fifth lens, and RS11 is the radius of curvature of the image side of the fifth lens.

12. The fixed-focus lens according to claim 1, characterized in that, The object-side optical aperture D of the first lens and the image height ImgH corresponding to the maximum field of view of the fixed-focus lens satisfy the following: 1.37≤D / ImgH≤1.

62.

13. The fixed-focus lens according to claim 1, characterized in that, The optical back focal length (BFL) of the fixed-focus lens and the lens group length (TL) satisfy the following: 0≤BFL / TL≤0.2.

Images