A fixed-focus lens

Abstract

An embodiment of the present invention discloses a fixed-focus lens, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged in sequence along the optical axis from the object plane to the image plane; the first lens, the second lens, the sixth lens, and the eighth lens are all negative-power lenses, and the fourth lens, the fifth lens, the seventh lens, and the ninth lens are all positive-power lenses; the optical power of the fixed-focus lens is Ф, the optical power of the first lens is Ф1, the optical power of the second lens is Ф2, the optical power of the third lens is Ф3, the optical power of the fourth lens is Ф4, the optical power of the fifth lens is Ф5, the optical power of the sixth lens is Ф6, the optical power of the seventh lens is Ф7, the optical power of the eighth lens is Ф8, and the optical power of the ninth lens is Ф9, -0.554 < Ф1 / Ф < -0.391; -0.675 < Ф2 / Ф < -0.355; -0.176 < Ф3 / Ф < 0.362; 0.366 < Ф4 / Ф < 0.61; 0.208 < Ф5 / Ф < 0.464; -0.535 < Ф6 / Ф < -0.209; 0.288 < Ф7 / Ф < 0.55; -0.476 < Ф8 / Ф < -0.18; 0.34 < Ф9 / Ф < 0.532. It realizes meeting the requirements of a super-large light transmission amount, improving the imaging quality, and meeting the monitoring requirements under low illumination conditions.

Description

Technical Field

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

[0002] At present, in the field of security monitoring, under night and low-light conditions, infrared supplementary lighting is usually adopted to achieve the imaging purpose. However, the imaging range of infrared supplementary lighting is small, and the color distortion is serious. In order to achieve a better night imaging effect, the demand for low-light cameras is increasing. At present, most of the common high-image-quality large-aperture lenses on the market are F1.4, few lenses reach the large aperture of F1.2, and they are usually paired with a 1 / 2.7 sensor, with a small target surface. There are few high-image-quality lenses with an ultra-large aperture of F1.0 and a large target surface. Based on the above market situation, it is necessary to develop a large-target-surface ultra-large-aperture 4K lens to have a better imaging effect at night. Summary of the Invention

[0003] The purpose of the embodiments of the present invention is to provide a fixed-focus lens, which meets the ultra-large light transmission amount, improves the imaging quality, and realizes the monitoring requirements under low illuminance conditions.

[0004] To achieve the above purpose, the embodiments of the present invention provide a fixed-focus lens, including: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged in sequence from the object surface to the image surface along the optical axis;

[0005] The first lens, the second lens, the sixth lens, and the eighth lens are all negative-power lenses, and the fourth lens, the fifth lens, the seventh lens, and the ninth lens are all positive-power lenses;

[0006] The optical power of the fixed-focus lens is Ф, the optical power of the first lens is Ф1, the optical power of the second lens is Ф2, the optical power of the third lens is Ф3, the optical power of the fourth lens is Ф4, the optical power of the fifth lens is Ф5, the optical power of the sixth lens is Ф6, the optical power of the seventh lens is Ф7, the optical power of the eighth lens is Ф8, and the optical power of the ninth lens is Ф9,

[0007] -0.554 < Ф1 / Ф < -0.391; -0.675 < Ф2 / Ф < -0.355; -0.176 < Ф3 / Ф < 0.362; 0.366 < Ф4 / Ф < 0.61; 0.208 < Ф5 / Ф < 0.464; -0.535 < Ф6 / Ф < -0.209; 0.288 < Ф7 / Ф < 0.55; -0.476 < Ф8 / Ф < -0.18; 0.34 < Ф9 / Ф < 0.532.

[0008] Optionally, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses, and the fourth lens is a glass spherical lens.

[0009] Optionally, the surface of the lens adjacent to the object side is the object-side surface, and the surface of the lens adjacent to the image side is the image-side surface;

[0010] The object-side surface of the first lens bulges toward the object surface, and the image-side surface of the first lens bulges toward the object surface; the object-side surface of the second lens bulges toward the image surface, and the image-side surface of the second lens bulges toward the object surface; the object-side surface of the third lens bulges toward the object surface, and the image-side surface of the third lens bulges toward the object surface; the object-side surface of the fourth lens bulges toward the object surface, and the image-side surface of the fourth lens bulges toward the image surface; the object-side surface of the sixth lens bulges toward the image surface, and the image-side surface of the sixth lens bulges toward the object surface; the object-side surface of the seventh lens bulges toward the object surface, and the image-side surface of the seventh lens bulges toward the image surface; the object-side surface of the eighth lens bulges toward the image surface, and the image-side surface of the eighth lens bulges toward the image surface.

[0011] Optionally, the refractive index of the first lens is n1 and the Abbe number is v1; the refractive index of the second lens is n2 and the Abbe number is v2; the refractive index of the third lens is n3 and the Abbe number is v3; the refractive index of the fourth lens is n4 and the Abbe number is v4; the refractive index of the fifth lens is n5 and the Abbe number is v5; the refractive index of the sixth lens is n6 and the Abbe number is v6; the refractive index of the seventh lens is n7 and the Abbe number is v7; the refractive index of the eighth lens is n8 and the Abbe number is v8; the refractive index of the ninth lens is n9 and the Abbe number is v9;

[0012] 1.47 < n1 < 1.96, 38 < v1 < 69; 1.47 < n2 < 1.55, 49 < v2 < 57.1; 1.60 < n3 < 1.68, 19.1 < v3 < 30.4; 1.55 < n4 < 2.005, 20 < v4 < 75; 1.47 < n5 < 1.55, 50 < v5 < 61; 1.60 < n6 < 1.68, 19.1 < v6 < 30.4; 1.47 < n7 < 1.55, 49 < v7 < 57.1; 1.60 < n8 < 1.68, 18.9 < v8 < 30.4; 1.47 < n9 < 1.55, 50.1 < v9 < 61.

[0013] Optionally, the distance from the optical axis center of the image side surface of the ninth lens to the image plane is BFL, and the distance from the optical axis center of the object side surface of the first lens to the image plane is TTL, where: TTL / BFL < 8.

[0014] Optionally, the second lens and the third lens, the sixth lens and the seventh lens, and the seventh lens and the eighth lens are abutted by spacer rings or bonded by glue.

[0015] Optionally, the f-number F of the fixed-focus lens satisfies F ≤ 1.0.

[0016] Optionally, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses, and the aspherical surface shape equation Z satisfies:

[0017]

[0018] In the formula, Z is the sagitta of the distance from the vertex of the aspherical surface at the position with a height of y along the optical axis direction; c = 1 / R, where R represents the paraxial curvature radius of the mirror surface; k is the conic coefficient; A, B, C, D, and E are high-order aspherical coefficients, and F is a high-order aspherical coefficient. Among them, the units of Z, R, and y are all mm.

[0019] The fixed-focus lens provided by the embodiment of the present invention ensures the balance of the incident angle sizes of the front and rear groups of lens elements in the fixed-focus lens by reasonably setting the number of lens elements in the fixed-focus lens and the relative relationship between the optical powers of the respective lens elements, reduces the sensitivity of the lens, improves the manufacturability, ensures that the fixed-focus lens has a high resolution, meets the requirement of a large light transmission amount, improves the imaging quality, and meets the monitoring requirements under low illuminance conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments read with reference to the accompanying drawings:

[0021] Figure 1 is a schematic structural diagram of a fixed-focus lens provided by Embodiment 1 of the present invention;

[0022] Figure 2 is a spherical aberration curve diagram of a fixed-focus lens provided by Embodiment 1 of the present invention;

[0023] Figure 3 is a field curvature and distortion diagram of a fixed-focus lens provided by Embodiment 1 of the present invention;

[0024] Figure 4 is a schematic structural diagram of a fixed-focus lens provided by Embodiment 2 of the present invention;

[0025] Figure 5 The spherical aberration curve diagram of a fixed-focus lens provided in the second embodiment of the present invention;

[0026] Figure 6 The field curvature distortion diagram of a fixed-focus lens provided in the second embodiment of the present invention;

[0027] Figure 7 The structural schematic diagram of a fixed-focus lens provided in the third embodiment of the present invention;

[0028] Figure 8 The spherical aberration curve diagram of a fixed-focus lens provided in the third embodiment of the present invention;

[0029] Figure 9 The field curvature distortion diagram of a fixed-focus lens provided in the third embodiment of the present invention;

[0030] Figure 10 The structural schematic diagram of a fixed-focus lens provided in the fourth embodiment of the present invention;

[0031] Figure 11 The spherical aberration curve diagram of a fixed-focus lens provided in the fourth embodiment of the present invention;

[0032] Figure 12 The field curvature distortion diagram of a fixed-focus lens provided in the fourth embodiment of the present invention. Detailed implementation manners

[0033] To further elaborate on the technical means and effects adopted by the embodiments of the present invention to achieve the predetermined invention purpose, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and preferred embodiments.

[0034] Secondly, the present invention is described in detail with reference to the schematic diagrams. When elaborating on the embodiments of the present invention, for the convenience of explanation, the schematic diagrams showing the structures of the device components are not enlarged locally according to the general scale, and the schematic diagrams are only examples and should not limit the protection scope of the present invention herein. In addition, the three-dimensional spatial dimensions of length, width, and height should be included in actual production.

[0035] Embodiment 1

[0036] Figure 1 The structural schematic diagram of a fixed-focus lens provided in the first embodiment of the present invention. As Figure 1As shown, the fixed-focus lens includes: a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, an eighth lens 108, and a ninth lens 109 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 101, the second lens 102, the sixth lens 106, and the eighth lens 108 are all negative-power lenses, and the fourth lens 104, the fifth lens 105, the seventh lens 107, and the ninth lens 109 are all positive-power lenses; the optical power of the fixed-focus lens is Ф, the optical power of the first lens 101 is Ф1, the optical power of the second lens 102 is Ф2, the optical power of the third lens 103 is Ф3, the optical power of the fourth lens 104 is Ф4, the optical power of the fifth lens 105 is Ф5, the optical power of the sixth lens 106 is Ф6, the optical power of the seventh lens 107 is Ф7, the optical power of the eighth lens 108 is Ф8, and the optical power of the ninth lens 109 is Ф9, -0.554 < Ф1 / Ф < -0.391; -0.675 < Ф2 / Ф < -0.355; -0.176 < Ф3 / Ф < 0.362; 0.366 < Ф4 / Ф < 0.61; 0.208 < Ф5 / Ф < 0.464; -0.535 < Ф6 / Ф < -0.209; 0.288 < Ф7 / Ф < 0.55; -0.476 < Ф8 / Ф < -0.18; 0.34 < Ф9 / Ф < 0.532.

[0037] Exemplarily, the optical power is equal to the difference between the image-side beam convergence and the object-side beam convergence, and it characterizes the ability of the optical system to deflect light rays. The greater the absolute value of the optical power, the stronger the bending ability of the light rays, and 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 used to characterize a certain refracting surface of a lens (i.e., a surface of the lens), can be used to characterize a certain lens, or can be used to characterize a system formed by multiple lenses together (i.e., a lens group). In the fixed-focus lens provided in this embodiment, each lens can be fixed to a lens barrel ( Figure 1Inside (not shown in the figure), the first lens 101, the second lens 102, the sixth lens 106, and the eighth lens 108 are all negative focal length lenses, and the fourth lens 104, the fifth lens 105, the seventh lens 107, and the ninth lens 109 are all positive focal length lenses. The first lens 101 and the second lens 102 are set as negative focal length lenses to control the incident angle of the optical system, which is beneficial for a large field of view and correcting field curvature. The third lens 103 can be a negative focal length lens, also used to control the incident angle of the optical system, or it can be a positive focal length lens for focusing the previous beam. The fourth lens 104 and the fifth lens 105 are positive focal length lenses, also used to focus the previous beam. The fifth lens 105 is a positive focal length lens, the sixth lens 106 is a negative focal length lens, the seventh lens 107 is a positive focal length lens, the eighth lens 108 is a negative focal length lens, and the ninth lens 109 is a positive focal length lens. The fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108, and the ninth lens 109 are used to correct off-axis aberrations, including field curvature, coma, astigmatism and other aberrations. The entire lens ensures that the optical power of the optical system is approximately proportionally distributed, ensuring the balance of the incident angle sizes of the front and rear lens groups, reducing the sensitivity of the lens, increasing the possibility of production, and ensuring no focus shift at high and low temperatures.

[0038] Furthermore, the optical power of the fixed-focus lens is Ф, the optical power of the first lens 101 is Ф1, the optical power of the second lens 102 is Ф2, the optical power of the third lens 103 is Ф3, the optical power of the fourth lens 104 is Ф4, the optical power of the fifth lens 105 is Ф5, the optical power of the sixth lens 106 is Ф6, the optical power of the seventh lens 107 is Ф7, the optical power of the eighth lens 108 is Ф8, and the optical power of the ninth lens 109 is Ф9. -0.554 < Ф1 / Ф < -0.391; -0.675 < Ф2 / Ф < -0.355; -0.176 < Ф3 / Ф < 0.362; 0.366 < Ф4 / Ф < 0.61; 0.208 < Ф5 / Ф < 0.464; -0.535 < Ф6 / Ф < -0.209; 0.288 < Ф7 / Ф < 0.55; -0.476 < Ф8 / Ф < -0.18; 0.34 < Ф9 / Ф < 0.532. Reasonably setting the optical powers between the various lenses in the fixed-focus lens ensures the adjustment of light rays and thus ensures the imaging effect.

[0039] The fixed-focus lens provided by the embodiment of the present invention, by reasonably setting the number of lenses in the fixed-focus lens and the relative relationship between the optical powers of the various lenses, ensures the balance of the incident angle sizes of the front and rear lens groups of the fixed-focus lens, reduces the sensitivity of the lens, increases the possibility of production, ensures that the fixed-focus lens has a high resolution, improves the imaging quality, and meets the monitoring requirements under low illumination conditions.

[0040] As a feasible implementation manner, the first lens 101, the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108, and the ninth lens 109 are all plastic aspherical lenses, and the fourth lens 104 is a glass spherical lens.

[0041] As another feasible implementation manner, the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108, and the ninth lens 109 are all plastic aspherical lenses, and the first lens 101 and the fourth lens 104 are glass spherical lenses.

[0042] Among them, the aspherical lens plays a role in correcting all high-order aberrations. The material of the plastic aspherical lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens can be various types of glass known to those skilled in the art. The embodiments of the present invention will not elaborate or limit this. Since the cost of the lens made of plastic material is much lower than that of the lens made of glass material, in the fixed-focus lens provided by the embodiments of the present invention, a hybrid combination of glass lenses and plastic lenses is adopted, which can effectively control the cost of the fixed-focus lens while ensuring the optical performance of the fixed-focus lens. And because the two types of materials have a mutual compensation effect, it can ensure that the fixed-focus lens can still be used normally in high and low temperature environments.

[0043] Optionally, the surface of the lens adjacent to the object surface side is the object-side surface, and the surface of the lens adjacent to the image surface side is the image-side surface; the object-side surface of the first lens 101 protrudes toward the object surface, and the image-side surface of the first lens 101 protrudes toward the object surface; the object-side surface of the second lens 102 protrudes toward the image surface, and the image-side surface of the second lens 102 protrudes toward the object surface; the object-side surface of the third lens 103 protrudes toward the object surface, and the image-side surface of the third lens 103 protrudes toward the object surface; the object-side surface of the fourth lens 104 protrudes toward the object surface, and the image-side surface of the fourth lens 104 protrudes toward the image surface; the object-side surface of the sixth lens 106 protrudes toward the image surface, and the image-side surface of the sixth lens 106 protrudes toward the object surface; the object-side surface of the seventh lens 107 protrudes toward the object surface, and the image-side surface of the seventh lens 107 protrudes toward the image surface; the object-side surface of the eighth lens 108 protrudes toward the image surface, and the image-side surface of the eighth lens 108 protrudes toward the image surface.

[0044] Exemplarily, such as Figure 1As shown in the figure, the object-side surface of the fifth lens 105 bulges towards the object plane, and the image-side surface of the fifth lens 105 bulges towards the image plane; the object-side surface of the ninth lens 109 bulges towards the object plane, and the image-side surface of the ninth lens 109 bulges towards the image plane. The ninth lens 109 can also be such that its object-side surface bulges towards the object plane and its image-side surface bulges towards the object plane, being a meniscus lens. By reasonably setting the surface shapes of the respective lenses, while ensuring that the optical powers of the respective lenses meet the optical power requirements in the above embodiments, it is also possible to ensure that the structure of the fixed-focus lens is compact and the integration degree of the fixed-focus lens is high.

[0045] Optionally, the refractive index of the first lens 101 is n1 and the Abbe number is v1; the refractive index of the second lens 102 is n2 and the Abbe number is v2; the refractive index of the third lens 103 is n3 and the Abbe number is v3; the refractive index of the fourth lens 104 is n4 and the Abbe number is v4; the refractive index of the fifth lens 105 is n5 and the Abbe number is v5; the refractive index of the sixth lens 106 is n6 and the Abbe number is v6; the refractive index of the seventh lens 107 is n7 and the Abbe number is v7; the refractive index of the eighth lens 108 is n8 and the Abbe number is v8; the refractive index of the ninth lens 109 is n9 and the Abbe number is v9; 1.47 < n1 < 1.96, 38 < v1 < 69; 1.47 < n2 < 1.55, 49 < v2 < 57.1; 1.60 < n3 < 1.68, 19.1 < v3 < 30.4; 1.55 < n4 < 2.005, 20 < v4 < 75; 1.47 < n5 < 1.55, 50 < v5 < 61; 1.60 < n6 < 1.68, 19.1 < v6 < 30.4; 1.47 < n7 < 1.55, 49 < v7 < 57.1; 1.60 < n8 < 1.68, 18.9 < v8 < 30.4; 1.47 < n9 < 1.55, 50.1 < v9 < 61.

[0046] Among them, the refractive index is the ratio of the propagation speed of light in a vacuum to the propagation speed of light in this medium, mainly used to describe the refractive ability of the material to light, and the refractive indices of different materials are different. 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 milder the dispersion of the medium, the larger the Abbe number. Thus, by matching and setting the refractive indices and Abbe numbers of the respective lenses in the fixed-focus lens, it is beneficial to realize the miniaturized design of the fixed-focus lens; at the same time, it is beneficial to achieve a higher pixel resolution and a larger aperture. Furthermore, it ensures the balance of the incident angle sizes of the front and rear groups of lens elements, so as to reduce the sensitivity of the lens and improve the production feasibility.

[0047] As a feasible implementation manner, the distance from the optical axis center of the image-side surface of the ninth lens 109 to the image plane is BFL, and the distance from the optical axis center of the object-side surface of the first lens 101 to the image plane is TTL, where: TTL / BFL < 8.

[0048] Exemplarily, the distance from the optical axis center of the image-side surface of the ninth lens 109 to the image plane can be understood as the back focus of the fixed-focus lens. By reasonably setting the relationship between the back focus of the fixed-focus lens and the total length of the fixed-focus lens, the overall structure of the fixed-focus lens can be ensured to be compact and the integration degree of the fixed-focus lens can be high.

[0049] Optionally, the second lens 102 and the third lens 103, the sixth lens 106 and the seventh lens 107, and the seventh lens 107 and the eighth lens 108 are abutted by a spacer ring or bonded by glue.

[0050] Among them, the second lens 102 and the third lens 103 can be abutted by a spacer ring or bonded by glue; the sixth lens 106 and the seventh lens 107 can also be abutted by a spacer ring or bonded by glue; the seventh lens 107 and the eighth lens 108 can also be abutted by a spacer ring or bonded by glue. The cemented lens can be used to minimize or eliminate chromatic aberration, so that various aberrations of the fixed-focus lens can be fully corrected. On the premise of a compact structure, the resolution can be improved, and the optical performance such as distortion and CRA can be optimized; and the light loss caused by reflection between lenses can be reduced, the illuminance can be improved, thereby improving the image quality and enhancing the clarity of the lens imaging. In addition, the use of the cemented lens can also reduce the assembly components between two lenses, simplify the assembly procedure in the lens manufacturing process, reduce costs, and reduce the tolerance sensitivity problems such as tilt / eccentricity generated during the assembly process of the lens unit.

[0051] Optionally, the aperture number F of the fixed-focus lens satisfies F≤1.0.

[0052] The fixed-focus lens provided by the embodiment of the present invention can meet a large light throughput, so as to meet the monitoring requirements under low illuminance conditions.

[0053] Continue to refer to Figure 1 , optionally, the fixed-focus lens further includes a diaphragm;

[0054] The diaphragm is located in the optical path between the fourth lens 104 and the fifth lens 105.

[0055] Among them, by setting the diaphragm in the optical path between the fourth lens 104 and the fifth lens 105, the propagation direction of the light beam can be adjusted, and the incident angle of the light can be adjusted, which is beneficial to further improving the imaging quality.

[0056] As a feasible implementation manner, the curvature radius, thickness, material, and semi-aperture of each lens surface in the fixed-focus lens will be described below.

[0057] Table 1 Design values of the optical parameters of the fixed-focus lens

[0058] Surface Serial Number Surface Type Radius of Curvature Thickness Nd Vd Semi-Diameter OBJ Spherical Surface Infinity Infinity 1 Spherical Surface 78.9768 0.900 1.61 60 2 Spherical Surface 5.0072 3.389 3 Aspherical Surface -10.4570 1.550 1.535 52.8 3.9 4 Aspherical Surface 7.3031 2.108 1.67 27.2 3.9 5 Aspherical Surface 15.1414 0.144 3.9 6 Spherical Surface 14.4274 5.188 1.807 45.935 6.2 STO Spherical Surface -8.3828 0.324 6.2 8 Aspherical Surface 9.2304 1.709 1.54 60 9 Aspherical Surface 10000 0.414 10 Aspherical Surface -29.5539 1.286 1.64 22.8 11 Aspherical Surface 6.9993 3.650 1.53 50 12 Aspherical Surface -12.1314 0.467 4.05 13 Aspherical Surface -2.7588 0.888 1.66 26.36 14 Aspherical Surface -4.4948 0.098 15 Aspherical Surface 4.2928 1.867 1.54 60 3.8 16 Aspherical Surface 34.1502 3.300 3.8 17 Spherical Surface Infinity 0.700 1.52 64.2 18 Spherical Surface Infinity 0.601

[0059] Continue to refer to Figure 1 As provided by the embodiments of the present invention, the fixed-focus lens includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, an eighth lens 108, and a ninth lens 109 arranged in sequence along the optical axis from the object surface to the image surface. Table 1 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the fixed-focus lens provided by the embodiment. Among them, the surface numbers are numbered according to the surface order of each lens. For example, "1" represents the object surface of the first lens 101, "2" represents the image surface of the first lens 101, "8" represents the object surface of the fifth lens 105, "9" represents the image surface of the fifth lens 105, and so on; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface bends towards the image surface side, and a negative value represents that the surface bends towards the object surface side; the thickness represents the central axial distance from the current surface to the next surface, and the units of the radius of curvature and thickness are both millimeters (mm).

[0060] On the basis of the above implementation, optionally, the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108, and the ninth lens 109 are all plastic aspherical lenses, and the first lens 101 and the fourth lens 104 are glass spherical lenses. The fixed-focus lens provided by the embodiments of the present invention further includes a diaphragm (STO). By adding a diaphragm, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality. The diaphragm can be located in the optical path between the fifth lens 105 and the sixth lens 106, but the specific setting position of the diaphragm in the embodiments of the present invention is not limited. By setting the diaphragm at a suitable position, it helps to improve the relative illuminance and reduce the CRA.

[0061] The aspherical surface shape equation Z of the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108, and the ninth lens 109 satisfies:

[0062]

[0063] In the formula, Z is the sagitta distance from the vertex of the aspherical surface at the position where the height is y along the optical axis direction; c = 1 / R, where R represents the paraxial radius of curvature of the mirror surface; k is the conic coefficient; A, B, C, D, and E are high-order aspherical coefficients. Among them, the units of Z, R, and y are all mm.

[0064] Exemplarily, Table 2 details the aspherical coefficients of each lens in this embodiment in a feasible implementation manner.

[0065] Table 2 Aspherical Coefficients of the Fixed-Focus Lens

[0066]

[0067] Among them, -2.194551E-03 means that the coefficient A of face number 3 is -2.194551*10 -3 .

[0068] The fixed-focus lens of the first embodiment achieves the following technical indicators:

[0069] F number: F=1.0.

[0070] Further, Figure 2 This is a spherical aberration curve diagram of a fixed-focus lens provided in Example 1 of the present invention, such as Figure 2 As shown, the spherical aberration of the fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm, and 0.656 μm) is within 0.05 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of the fixed-focus lens is very small. Therefore, it can be seen that the fixed-focus lens provided in Example 1 of the present invention can well correct aberrations.

[0071] Figure 3 This is a field curvature distortion diagram of a fixed-focus lens provided in Example 1 of the present invention, such as Figure 3 As shown in the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature, the unit is mm; the vertical coordinate represents the normalized image height, no unit; T represents the meridian, S represents the sagittal; Figure 3 It can be seen that the fixed-focus lens provided in the first embodiment effectively controls field curvature from light with a wavelength of 436 nm to light with a wavelength of 656 nm. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the magnitude of the distortion, in %, and the vertical coordinate represents the normalized image height, without a unit.

[0072] Embodiment 2

[0073] Figure 4 This is a structural diagram of a fixed-focus lens provided in Example 2 of the present invention, such as Figure 4As shown in the figure, the fixed-focus lens includes: a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, a fifth lens 205, a sixth lens 206, a seventh lens 207, an eighth lens 208, and a ninth lens 209 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 201, the second lens 202, the sixth lens 206, and the eighth lens 208 are all negative-power lenses, and the fourth lens 204, the fifth lens 205, the seventh lens 207, and the ninth lens 209 are all positive-power lenses; the optical power of the fixed-focus lens is Ф, the optical power of the first lens 201 is Ф1, the optical power of the second lens 202 is Ф2, the optical power of the third lens 203 is Ф3, the optical power of the fourth lens 204 is Ф4, the optical power of the fifth lens 205 is Ф5, the optical power of the sixth lens 206 is Ф6, the optical power of the seventh lens 207 is Ф7, the optical power of the eighth lens 208 is Ф8, and the optical power of the ninth lens 209 is Ф9, -0.554 < Ф1 / Ф < -0.391; -0.675 < Ф2 / Ф < -0.355; -0.176 < Ф3 / Ф < 0.362; 0.366 < Ф4 / Ф < 0.61; 0.208 < Ф5 / Ф < 0.464; -0.535 < Ф6 / Ф < -0.209; 0.288 < Ф7 / Ф < 0.55; -0.476 < Ф8 / Ф < -0.18; 0.34 < Ф9 / Ф < 0.532.

[0074] By reasonably setting the relative relationship between the number of lenses in the fixed-focus lens and the optical powers of each lens, it is ensured that the fixed-focus lens can meet the requirement of a large light transmission amount under the premise of a small aperture number, realizing the monitoring requirements under low illuminance conditions; at the same time, it is ensured that the resolving power of the fixed-focus lens meets the imaging requirements when used in high and low temperature environments, and the imaging ability of the lens in the night environment is ensured.

[0075] As a feasible implementation manner, the second lens 202, the third lens 203, the fifth lens 105, the sixth lens 206, the seventh lens 207, the eighth lens 208, and the ninth lens 209 are all plastic aspherical lenses, and the first lens 201 and the fourth lens 204 are glass spherical lenses. Among them, the material of the plastic aspherical lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens is various types of glass known to those skilled in the art. This embodiment of the present invention will not elaborate or limit this. Since the cost of a lens made of plastic material is much lower than that of a lens made of glass material, in the fixed-focus lens provided in this embodiment of the present invention, a mixed combination of glass lenses and plastic lenses is adopted, which can effectively control the cost of the fixed-focus lens while ensuring the optical performance of the fixed-focus lens.

[0076] Among them, the ranges of the optical power, refractive index, and Abbe number of each lens are the same as those in Embodiment 1, and will not be elaborated here.

[0077] Exemplarily, Table 3 details the specific setting parameters of each lens in the fixed-focus lens provided in the second embodiment of the present invention in a feasible implementation manner.

[0078] Table 3 Design values of the optical parameters of the fixed-focus lens

[0079] Surface Serial Number Surface Type Radius of Curvature Thickness Nd Vd Semi-Diameter OBJ Spherical Surface Infinity Infinity 1 Spherical Surface 80.7201 1.380 1.61 59.2 2 Spherical Surface 5.0508 3.750 3 Aspherical Surface -9.6306 1.485 1.54 50 4 4 Aspherical Surface 6.0798 1.778 1.66 19.7 4 5 Aspherical Surface 14.1425 0.118 4 6 Spherical Surface 13.1213 4.658 1.806 45 6.2 STO Spherical Surface -10.1691 0.349 6.2 8 Aspherical Surface 9.6688 2.027 1.535 51.8 9 Aspherical Surface -16.0419 1.416 1.64 22.9 10 Aspherical Surface 10.1589 3.581 1.535 55.33 11 Aspherical Surface -12.7295 0.525 12 Aspherical Surface -2.9183 1.018 1.66 19 13 Aspherical Surface -4.7459 0.099 3.76 14 Aspherical Surface 4.4031 1.847 1.54 51.4 3.8 15 Aspherical Surface 31.4068 3.300 3.8 16 Spherical Surface Infinity 0.700 1.52 64.2 17 Spherical Surface Infinity 1.186

[0080] Continuing to refer to Figure 4 , the fixed-focus lens provided in the embodiment of the present invention includes a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, a fifth lens 205, a sixth lens 206, a seventh lens 207, an eighth lens 208, and a ninth lens 209 arranged in sequence along the optical axis from the object plane to the image plane. Table 3 shows the optical physical parameters such as the curvature radius, thickness, and material of each lens in the fixed-focus lens provided in the embodiment. Among them, the surface number is numbered according to the surface order of each lens. For example, "1" represents the object surface of the first lens 201, "2" represents the image surface of the first lens 201, "8" represents the object surface of the fifth lens 205, "9" represents the image surface of the fifth lens 205, and so on; the curvature radius represents the degree of curvature of the lens surface, a positive value represents that the surface bends towards the image plane side, and a negative value represents that the surface bends towards the object plane side; the thickness represents the central axial distance from the current surface to the next surface, and the units of the curvature radius and thickness are both millimeters (mm).

[0081] On the basis of the above implementation, optionally, the second lens 202, the third lens 203, the fifth lens 205, the sixth lens 206, the seventh lens 207, the eighth lens 208, and the ninth lens 209 are all plastic aspherical lenses, and the first lens 201 and the fourth lens 204 are glass spherical lenses. The fixed-focus lens provided in the embodiment of the present invention further includes a diaphragm (STO). By adding a diaphragm, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality. The diaphragm can be located in the optical path between the fifth lens 205 and the sixth lens 206, but the specific setting position of the diaphragm in the embodiment of the present invention is not limited. By setting the diaphragm at a suitable position, it helps to improve the relative illuminance and reduce the CRA.

[0082] The aspherical surface shape equation Z of the second lens 202, the third lens 203, the fifth lens 205, the sixth lens 206, the seventh lens 207, the eighth lens 208, and the ninth lens 209 satisfies:

[0083]

[0084] Wherein, Z is the sagitta, which is the distance from the vertex of the aspheric surface to the aspheric surface along the optical axis at the position with height y; c = 1 / R, where R represents the paraxial curvature radius of the mirror surface; k is the conic coefficient; A, B, C, D, and E are the aspheric coefficients of higher order. Herein, the units of Z, R, and y are all mm.

[0085] Exemplarily, Table 4 details the aspheric coefficients of each lens in this embodiment in a feasible implementation manner.

[0086] Table 4 Aspheric Coefficients in the Fixed-Focus Lens

[0087]

[0088] Among them, -2.273994E-03 indicates that the coefficient A of the surface number 3 is -2.273994×10 -3 . The fixed-focus lens of the second embodiment has achieved the following technical indicators: F-number: F = 1.0.

[0089] Furthermore, Figure 5 is the spherical aberration curve diagram of a fixed-focus lens provided by the second embodiment of the present invention. As Figure 2 shown, the spherical aberration of this fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm, 0.656 μm, and 0.850 μm) is within 0.05 mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of this fixed-focus lens is very small. Thus, it can be known that the fixed-focus lens provided by the second embodiment of the present invention can correct aberration well.

[0090] Figure 6 is the field curvature and distortion diagram of a fixed-focus lens provided by the second embodiment of the present invention. As Figure 6 shown, in the left coordinate system, the horizontal coordinate represents the magnitude of the field curvature, with the unit of mm; the vertical coordinate represents the normalized image height, without a unit; where T represents the meridian and S represents the sagittal; from Figure 6 it can be seen that the field curvature of the fixed-focus lens provided by the second embodiment is effectively controlled from the light with a wavelength of 436 nm to the light with a wavelength of 850 nm, that is, during imaging, the image quality at the center and the image quality at the periphery have a small difference; in the right coordinate system, the horizontal coordinate represents the magnitude of the distortion, with the unit of %; the vertical coordinate represents the normalized image height, without a unit.

[0091] Embodiment Three

[0092] Figure 7 is the structural schematic diagram of a fixed-focus lens provided by the third embodiment of the present invention. As Figure 7As shown in the figure, the fixed-focus lens includes: a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, a sixth lens 306, a seventh lens 307, an eighth lens 308, and a ninth lens 309 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 301, the second lens 302, the sixth lens 306, and the eighth lens 308 are all negative-power lenses, and the fourth lens 304, the fifth lens 305, the seventh lens 307, and the ninth lens 309 are all positive-power lenses; the optical power of the fixed-focus lens is Ф, the optical power of the first lens 301 is Ф1, the optical power of the second lens 302 is Ф2, the optical power of the third lens 303 is Ф3, the optical power of the fourth lens 304 is Ф4, the optical power of the fifth lens 305 is Ф5, the optical power of the sixth lens 306 is Ф6, the optical power of the seventh lens 307 is Ф7, the optical power of the eighth lens 308 is Ф8, and the optical power of the ninth lens 309 is Ф9, -0.554 < Ф1 / Ф < -0.391; -0.675 < Ф2 / Ф < -0.355; -0.176 < Ф3 / Ф < 0.362; 0.366 < Ф4 / Ф < 0.61; 0.208 < Ф5 / Ф < 0.464; -0.535 < Ф6 / Ф < -0.209; 0.288 < Ф7 / Ф < 0.55; -0.476 < Ф8 / Ф < -0.18; 0.34 < Ф9 / Ф < 0.532.

[0093] By reasonably setting the relative relationship between the number of lenses in the fixed-focus lens and the optical power of each lens, it is ensured that the fixed-focus lens can meet the requirement of a super-large light transmission amount under the premise of a small aperture number, and realize the monitoring requirements under low illumination conditions; at the same time, it is ensured that the resolution of the fixed-focus lens meets the imaging requirements when used in high and low temperature environments, and the imaging ability of the lens in the night environment is ensured.

[0094] As a feasible implementation manner, the first lens 301, the second lens 302, the third lens 303, the fifth lens 305, the sixth lens 306, the seventh lens 307, the eighth lens 308, and the ninth lens 309 are all plastic aspherical lenses, and the fourth lens 304 is a glass spherical lens. Among them, the material of the plastic aspherical lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens is various types of glass known to those skilled in the art. The embodiments of the present invention do not elaborate or limit this. Since the cost of a lens made of plastic material is much lower than that of a lens made of glass material, in the fixed-focus lens provided by the embodiments of the present invention, a hybrid combination of glass lenses and plastic lenses is adopted, which can effectively control the cost of the fixed-focus lens while ensuring the optical performance of the fixed-focus lens.

[0095] Among them, the optical power, refractive index, and Abbe number ranges of each lens are the same as those in Embodiment 1, and will not be elaborated here.

[0096] Exemplarily, Table 5 details the specific setting parameters of each lens in the fixed-focus lens provided in the third embodiment of the present invention in a feasible implementation manner.

[0097] Table 5 Design values of the optical parameters of the fixed-focus lens

[0098] Surface Serial Number Surface Type Radius of Curvature Thickness Nd Vd Semi-Diameter OBJ Spherical Surface Infinity Infinity 1 Aspherical Surface 90.8753 0.877 1.535 53 2 Aspherical Surface 5.1083 3.985 3 Aspherical Surface -11.3289 0.965 1.535 52.77 4.2 4 Aspherical Surface 11.4494 0.100 4.2 5 Aspherical Surface 13.0219 1.989 1.64 23.24 4.2 6 Aspherical Surface 8.2737 0.175 4.02 7 Spherical Surface 11.4055 4.477 2 25.53 6.2 STO Spherical Surface -16.3407 0.333 6.2 9 Aspherical Surface 8.1952 2.063 1.535 56.84 10 Aspherical Surface -41.7244 0.196 11 Aspherical Surface -19.1171 1.319 1.66 20.3 12 Aspherical Surface 8.3005 0.100 13 Aspherical Surface 6.2967 4.039 1.535 56 14 Aspherical Surface -11.2569 0.450 15 Aspherical Surface -2.7376 0.930 1.64 22.92 4.2 16 Aspherical Surface -4.4027 0.098 17 Aspherical Surface 4.6358 2.284 1.535 57.8 3.8 18 Aspherical Surface -224.6197 3.300 3.8 19 Spherical Surface Infinity 0.700 1.52 64.2 20 Spherical Surface Infinity 1.440

[0099] Continuing to refer to Figure 7 , the fixed-focus lens provided in the embodiment of the present invention includes a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, a sixth lens 306, a seventh lens 307, an eighth lens 308, and a ninth lens 309 arranged in sequence along the optical axis from the object plane to the image plane. Table 5 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the fixed-focus lens provided in the embodiment. Among them, the surface number is numbered according to the surface order of each lens. For example, "1" represents the object surface of the first lens 301, "2" represents the image surface of the first lens 301, "9" represents the object surface of the fifth lens 305, "10" represents the image surface of the fifth lens 305, and so on; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface bends towards the image plane side, and a negative value represents that the surface bends towards the object plane side; the thickness represents the central axial distance from the current surface to the next surface, and the units of the radius of curvature and the thickness are both millimeters (mm).

[0100] On the basis of the above implementation, optionally, the first lens 301, the second lens 302, the third lens 303, the fifth lens 305, the sixth lens 306, the seventh lens 307, the eighth lens 308, and the ninth lens 309 are all plastic aspherical lenses, and the fourth lens 304 is a glass spherical lens. The fixed-focus lens provided in the embodiment of the present invention further includes a diaphragm (STO). By adding a diaphragm, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality. The diaphragm can be located in the optical path between the fifth lens 305 and the sixth lens 306, but the specific setting position of the diaphragm in the embodiment of the present invention is not limited. By setting the diaphragm at a suitable position, it helps to improve the relative illuminance and reduce the CRA.

[0101] The aspherical surface shape equation Z of the second lens 302, the third lens 303, the fifth lens 305, the sixth lens 306, the seventh lens 307, the eighth lens 308, and the ninth lens 309 satisfies:

[0102]

[0103] In the formula, Z is the sagitta, which is the distance from the vertex of the aspheric surface to the aspheric surface along the optical axis at the position with height y; c = 1 / R, where R represents the paraxial curvature radius of the mirror surface; k is the conic coefficient; A, B, C, D, and E are the high-order aspheric coefficients. Here, the units of Z, R, and y are all mm.

[0104] Exemplarily, Table 6 details the aspheric coefficients of each lens in this embodiment in a feasible implementation manner.

[0105] Table 6 Aspheric Coefficients in the Fixed-Focus Lens

[0106]

[0107] Among them, -2.811354E-05 means that the coefficient A of the surface number 1 is -2.811354×10 -5 .

[0108] The fixed-focus lens of the third embodiment has reached the following technical indicators:

[0109] F number: F = 1.0.

[0110] Furthermore, Figure 8 This is the spherical aberration curve diagram of a fixed-focus lens provided by the third embodiment of the present invention. As Figure 8 shown, the spherical aberration of this fixed-focus lens at different wavelengths (0.436μm, 0.486μm, 0.588μm, and 0.656μm) is within 0.05mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of this fixed-focus lens is very small. Thus, it can be known that the fixed-focus lens provided by the third embodiment of the present invention can correct aberrations well.

[0111] Figure 9 This is the field curvature and distortion diagram of a fixed-focus lens provided by the third embodiment of the present invention. As Figure 9 shown, in the left coordinate system, the horizontal coordinate represents the magnitude of field curvature, with the unit of mm; the vertical coordinate represents the normalized image height, without a unit; where T represents the meridian and S represents the sagittal; it can be seen from Figure 9 that for the fixed-focus lens provided by the third embodiment, from the light with a wavelength of 436nm to the light with a wavelength of 656nm, the field curvature is effectively controlled, that is, when imaging, the image quality at the center and the image quality at the periphery have a small difference; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion, with the unit of %; the vertical coordinate represents the normalized image height, without a unit.

[0112] Embodiment 4

[0113] Figure 10 This is the structural schematic diagram of a fixed-focus lens provided by the fourth embodiment of the present invention. As Figure 10As shown in the figure, the fixed-focus lens includes: a first lens 401, a second lens 402, a third lens 403, a fourth lens 404, a fifth lens 405, a sixth lens 406, a seventh lens 407, an eighth lens 408, and a ninth lens 409 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 401, the second lens 402, the sixth lens 406, and the eighth lens 408 are all negative-power lenses, and the fourth lens 404, the fifth lens 405, the seventh lens 407, and the ninth lens 409 are all positive-power lenses; the optical power of the fixed-focus lens is Ф, the optical power of the first lens 401 is Ф1, the optical power of the second lens 402 is Ф2, the optical power of the third lens 403 is Ф3, the optical power of the fourth lens 404 is Ф4, the optical power of the fifth lens 405 is Ф5, the optical power of the sixth lens 406 is Ф6, the optical power of the seventh lens 407 is Ф7, the optical power of the eighth lens 408 is Ф8, and the optical power of the ninth lens 409 is Ф9, -0.554 < Ф1 / Ф < -0.391; -0.675 < Ф2 / Ф < -0.355; -0.176 < Ф3 / Ф < 0.362; 0.366 < Ф4 / Ф < 0.61; 0.208 < Ф5 / Ф < 0.464; -0.535 < Ф6 / Ф < -0.209; 0.288 < Ф7 / Ф < 0.55; -0.476 < Ф8 / Ф < -0.18; 0.34 < Ф9 / Ф < 0.532.

[0114] By reasonably setting the relative relationship between the number of lenses in the fixed-focus lens and the optical power of each lens, it is ensured that the fixed-focus lens can meet the requirement of a large light transmission amount under the premise of a small aperture number, and realize the monitoring requirements under low illuminance conditions; at the same time, it is ensured that the resolution of the fixed-focus lens meets the imaging requirements when used in high and low temperature environments, and the imaging ability of the lens in the night environment is ensured.

[0115] As a feasible implementation manner, the second lens 402, the third lens 403, the fifth lens 405, the sixth lens 406, the seventh lens 407, the eighth lens 408, and the ninth lens 409 are all plastic aspherical lenses, and the first lens 401 and the fourth lens 404 are glass spherical lenses. Among them, the material of the plastic aspherical lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens is various types of glass known to those skilled in the art. The embodiments of the present invention do not elaborate or limit this. Since the cost of a lens made of plastic material is much lower than that of a lens made of glass material, in the fixed-focus lens provided by the embodiments of the present invention, a mixed combination of glass lenses and plastic lenses is adopted, which can effectively control the cost of the fixed-focus lens while ensuring the optical performance of the fixed-focus lens.

[0116] Among them, the optical power, refractive index, and Abbe number ranges of each lens are the same as those in Embodiment 1, and will not be elaborated here.

[0117] Exemplarily, Table 7 details the specific setting parameters of each lens in the fixed-focus lens provided in the fourth embodiment of the present invention in a feasible implementation manner.

[0118] Table 7 Design values of the optical parameters of the fixed-focus lens

[0119] Surface Serial Number Surface Type Radius of Curvature Thickness Nd Vd Semi-Diameter OBJ Spherical Surface Infinity Infinity 1 Spherical Surface 40.1814 1.499 1.82 48.1 2 Spherical Surface 5.4168 2.964 3 Aspherical Surface -9.8208 1.526 1.535 53 4 4 Aspherical Surface 6.2305 0.097 4.2 5 Aspherical Surface 5.9632 2.072 1.66 21.5 4.2 6 Aspherical Surface 13.6693 0.222 4.2 7 Spherical Surface 13.3159 4.526 1.648 70 6.2 STO Spherical Surface -11.5901 0.594 6.2 9 Aspherical Surface 7.6845 3.427 1.535 56.4 10 Aspherical Surface -13.3480 0.534 11 Aspherical Surface -37.4255 0.882 1.64 23.4 12 Aspherical Surface 14.4222 3.169 1.535 56.09 13 Aspherical Surface -11.8680 0.853 14 Aspherical Surface -2.1710 0.953 1.66 20.1 15 Aspherical Surface -3.9463 0.113 4.171 16 Aspherical Surface 4.2404 1.775 1.535 57.4 3.8 17 Aspherical Surface 895.9781 3.300 3.8 18 Spherical Surface Infinity 0.700 1.52 64.2 19 Spherical Surface Infinity 0.603

[0120] Continuing to refer to Figure 10 , the fixed-focus lens provided in the embodiment of the present invention includes a first lens 401, a second lens 402, a third lens 403, a fourth lens 404, a fifth lens 405, a sixth lens 406, a seventh lens 407, an eighth lens 408, and a ninth lens 409 arranged in sequence along the optical axis from the object plane to the image plane. Table 7 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the fixed-focus lens provided in the embodiment. Among them, the surface numbers are numbered according to the surface order of each lens. For example, "1" represents the object surface of the first lens 401, "2" represents the image surface of the first lens 401, "9" represents the object surface of the fifth lens 405, "10" represents the image surface of the fifth lens 405, and so on; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface bends towards the image plane side, and a negative value represents that the surface bends towards the object plane side; the thickness represents the central axial distance from the current surface to the next surface, and the units of the radius of curvature and the thickness are both millimeters (mm).

[0121] On the basis of the above implementation, optionally, the second lens 402, the third lens 403, the fifth lens 405, the sixth lens 406, the seventh lens 407, the eighth lens 408, and the ninth lens 409 are all plastic aspherical lenses, and the first lens 401 and the fourth lens 404 are glass spherical lenses. The fixed-focus lens provided in the embodiment of the present invention further includes a stop (STO). By adding a stop, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality. The stop can be located in the optical path between the fifth lens 405 and the sixth lens 406, but the specific setting position of the stop in the embodiment of the present invention is not limited. By setting the stop at a suitable position, it helps to improve the relative illumination and reduce the CRA.

[0122] The aspherical surface shape equation Z of the second lens 402, the third lens 403, the fifth lens 405, the sixth lens 406, the seventh lens 407, the eighth lens 408, and the ninth lens 409 satisfies:

[0123]

[0124] In the formula, Z is the sagitta, which is the distance from the vertex of the aspheric surface to the aspheric surface along the optical axis at the position with height y; c = 1 / R, where R represents the paraxial curvature radius of the mirror surface; k is the conic coefficient; A, B, C, D, and E are aspheric coefficients of higher order. Here, the units of Z, R, and y are all mm.

[0125] Exemplarily, Table 8 details the aspheric coefficients of each lens in this embodiment in a feasible implementation manner.

[0126] Table 8 Aspheric Coefficients in the Fixed-Focus Lens

[0127]

[0128] Among them, -2.796474E-03 indicates that the coefficient A of the surface number 3 is -2.796474×10 -3 .

[0129] The fixed-focus lens of Embodiment 4 has reached the following technical indicators:

[0130] F number: F = 1.0.

[0131] Furthermore, Figure 11 is the spherical aberration curve diagram of a fixed-focus lens provided in Embodiment 4 of the present invention. As Figure 11 shown, the spherical aberration of this fixed-focus lens at different wavelengths (0.436μm, 0.486μm, 0.588μm, and 0.656μm) is within 0.05mm, and the curves at different wavelengths are relatively concentrated, indicating that the axial aberration of this fixed-focus lens is very small. Therefore, it can be known that the fixed-focus lens provided in Embodiment 4 of the present invention can correct aberration well.

[0132] Figure 12 is the field curvature and distortion diagram of a fixed-focus lens provided in Embodiment 4 of the present invention. As Figure 12 shown, in the left coordinate system, the horizontal coordinate represents the magnitude of field curvature, with the unit of mm; the vertical coordinate represents the normalized image height, without a unit; where T represents the meridian and S represents the sagittal; from Figure 12 it can be seen that the field curvature of the fixed-focus lens provided in Embodiment 4 is effectively controlled from the light with a wavelength of 436nm to the light with a wavelength of 656nm, that is, when imaging, the image quality at the center and the image quality at the periphery have a small difference; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion, with the unit of %; the vertical coordinate represents the normalized image height, without a unit.

[0133] Table 9 is a summary of the parameters of the above embodiments. As shown in Table 9, it details the optical power, refractive index, and Abbe number of each lens in the above embodiments.

[0134] Table 9 Summary of Parameters of the Above Embodiments

[0135] Example 1 Example 2 Example 3 Example 4 Scope of Protection Ф1 / Ф -0.475 -0.473 -0.414 -0.531 -0.554～-0.391 Ф2 / Ф -0.536 -0.630 -0.401 -0.599 -0.675～-0.355 Ф3 / Ф 0.220 0.283 -0.099 0.285 -0.176～0.362 Ф4 / Ф 0.572 0.539 0.575 0.401 0.366～0.61 Ф5 / Ф 0.244 0.363 0.324 0.427 0.208～0.464 Ф6 / Ф -0.479 -0.442 -0.489 -0.256 -0.535～-0.209 Ф7 / Ф 0.466 0.376 0.512 0.325 0.288～0.55 Ф8 / Ф -0.308 -0.285 -0.291 -0.444 -0.476～-0.18 Ф9 / Ф 0.470 0.454 0.493 0.519 0.34～0.532 n1 1.61 1.61 1.535 1.82 1.47～1.96 n2 1.535 1.54 1.535 1.535 1.47～1.55 n3 1.67 1.66 1.64 1.66 1.6～1.68 n4 1.807 1.806 2 1.648 1.55～2.005 n5 1.54 1.535 1.535 1.535 1.47～1.55 n6 1.64 1.64 1.66 1.64 1.6～1.68 n7 1.53 1.535 1.535 1.535 1.47～1.55 n8 1.66 1.66 1.64 1.66 1.6～1.68 n9 1.54 1.54 1.535 1.535 1.47～1.55 v1 60 59.2 53 48.1 38～69 v2 52.8 50 52.77 53 49～57.1 v3 27.2 19.7 23.24 21.5 19.1～30.4 v4 45.935 45 25.53 70 20～75 v5 60 51.8 56.84 56.4 50～61 v6 22.8 22.9 20.3 23.4 19.1～30.4 v7 50 55.33 56 56.09 49～57.1 v8 26.36 19 22.92 20.1 18.9～30.4 v9 60 51.4 57.8 57.4 50.1～61 TTL / BFL 6.2 5.63 5.48 6.476 <8

[0136] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, re-adjustments, combinations with each other and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fixed-focus lens, characterized in that, Comprising: A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged in sequence along the optical axis from the object surface to the image surface; The first lens, the second lens, the sixth lens, and the eighth lens are all negative focal length lenses, and the fourth lens, the fifth lens, the seventh lens, and the ninth lens are all positive focal length lenses; The focal length of the fixed-focus lens is Ф, the focal length of the first lens is Ф1, the focal length of the second lens is Ф2, the focal length of the third lens is Ф3, the focal length of the fourth lens is Ф4, the focal length of the fifth lens is Ф5, the focal length of the sixth lens is Ф6, the focal length of the seventh lens is Ф7, the focal length of the eighth lens is Ф8, and the focal length of the ninth lens is Ф9, -0.554 < Ф1 / Ф < -0.391; -0.675 < Ф2 / Ф < -0.355; -0.176 < Ф3 / Ф < 0.362; 0.366 < Ф4 / Ф < 0.61; 0.208 < Ф5 / Ф < 0.464; -0.535 < Ф6 / Ф < -0.209; 0.288 < Ф7 / Ф < 0.55; -0.476 < Ф8 / Ф < -0.18; 0.34 < Ф9 / Ф < 0.532; The fixed-focus lens further includes a diaphragm; the diaphragm is located in the optical path between the fourth lens and the fifth lens.

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

3. The fixed-focus lens according to claim 1, wherein The surface of the lens adjacent to the object surface side is the object-side surface, and the surface of the lens adjacent to the image surface side is the image-side surface; The object-side surface of the first lens bulges towards the object surface, and the image-side surface of the first lens bulges towards the object surface; The object-side surface of the second lens bulges towards the image surface, and the image-side surface of the second lens bulges towards the object surface; The object-side surface of the third lens bulges towards the object surface, and the image-side surface of the third lens bulges towards the object surface; The object-side surface of the fourth lens bulges towards the object surface, and the image-side surface of the fourth lens bulges towards the image surface; The object-side surface of the sixth lens bulges towards the image surface, and the image-side surface of the sixth lens bulges towards the object surface; The object-side surface of the seventh lens bulges towards the object surface, and the image-side surface of the seventh lens bulges towards the image surface; The object-side surface of the eighth lens bulges towards the image surface, and the image-side surface of the eighth lens bulges towards the image surface.

4. The fixed-focus lens according to claim 1, characterized in that, The refractive index of the first lens is n1, and the Abbe number is v1; the refractive index of the second lens is n2, and the Abbe number is v2; the refractive index of the third lens is n3, and the Abbe number is v3; the refractive index of the fourth lens is n4, and the Abbe number is v4; the refractive index of the fifth lens is n5, and the Abbe number is v5; the refractive index of the sixth lens is n6, and the Abbe number is v6; the refractive index of the seventh lens is n7, and the Abbe number is v7; the refractive index of the eighth lens is n8, and the Abbe number is v8; the refractive index of the ninth lens is n9, and the Abbe number is v9; 1.47 < n1 < 1.96, 38 < v1 < 69; 1.47 < n2 < 1.55, 49 < v2 < 57.1; 1.60 < n3 < 1.68, 19.1 < v3 < 30.4; 1.55 < n4 < 2.005, 20 < v4 < 75; 1.47 < n5 < 1.55, 50 < v5 < 61; 1.60 < n6 < 1.68, 19.1 < v6 < 30.4; 1.47 < n7 < 1.55, 49 < v7 < 57.1; 1.60 < n8 < 1.68, 18.9 < v8 < 30.4; 1.47 < n9 < 1.55, 50.1 < v9 < 61.

5. The fixed-focus lens according to claim 1, wherein, The distance from the optical axis center of the image side surface of the ninth lens to the image plane is BFL, and the distance from the optical axis center of the object side surface of the first lens to the image plane is TTL, where: TTL / BFL < 8.

6. The fixed-focus lens according to claim 1, characterized in that, Between the second lens and the third lens, the sixth lens and the seventh lens, and the seventh lens and the eighth lens, they are supported by spacer rings or bonded with glue.

7. The fixed-focus lens according to claim 1, characterized in that, The aperture number F of the fixed-focus lens satisfies F ≤ 1.

0.

8. The fixed-focus lens according to claim 2, characterized in that, The second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses, and the aspherical surface shape equation Z satisfies: In the formula, Z is the sagitta of the distance from the vertex of the aspherical surface at the position with a height of y along the optical axis direction; c = 1 / R, where R represents the paraxial curvature radius of the mirror surface; k is the conic coefficient; A, B, C, D, and E are high-order aspherical coefficients. Among them, the units of Z, R, and y are all mm.

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