Prime lens

Abstract

The utility model relates to a prime lens, which is arranged along an optical axis in a direction from an object side to an image side. The utility model discloses a multi-lens zoom lens, which sequentially comprises eight lenses in total, namely a first lens with negative focal power, a second lens with positive focal power, a third lens with positive focal power, a fourth lens with positive focal power, a fifth lens with negative focal power, a sixth lens with positive focal power, a seventh lens with negative focal power and an eighth lens with positive focal power, the first lens is a convex-concave lens; the second lens is a concave-convex lens; the third lens is a concave-convex lens; the fourth lens is a convex-convex lens; the fifth lens is a concave lens; the sixth lens is a convex-convex lens; the seventh lens is a concave-convex lens; the eighth lens is a convex-concave lens. The prime lens provided by the utility model at least has one of the characteristics of ultra-large aperture, long focal length, 4K high resolution, low cost, simple structure, small volume, no virtual focus in a temperature range of-40 DEG C to 80 DEG C and the like, and is especially suitable for a day and night dual-purpose security lens with infrared performance.

Description

Technical Field

[0001] The utility model relates to the technical field of imaging lenses, and in particular to a fixed-focus lens having the characteristics of low cost, large aperture, long focal length, small size, infrared confocality, and the like. Background Art

[0002] In recent years, with the technological innovation and breakthroughs in data transmission technology, data storage technology, image processing technology and high-definition television display technology, it has become possible to achieve ultra-high-definition video surveillance with 4K resolution, and it will definitely become a future development trend. This requires the lens (lens system) to have a higher resolution.

[0003] At the same time, with the popularization of work in the security and public safety fields, the demand for surveillance fixed-focus lenses is increasing. Large aperture lenses have higher light transmittance and higher image quality. While ensuring the large aperture and low cost of the lens, the market's requirements for its infrared performance are also getting higher and higher.

[0004] The large aperture fixed focus surveillance lenses on the market today still have the following shortcomings:

[0005] 1. The existing lens configuration makes it difficult to make good corrections for system aberrations, resulting in poor imaging quality;

[0006] 2. Existing lenses have the problem of being too long and too large in size, which makes the overall cost and weight of the lens too high;

[0007] 3. The existing lens has a small relative aperture, poor light transmission performance, and low relative illumination at the edge;

[0008] 4. Existing lenses have difficulty in making good corrections for system chromatic aberration at large apertures, and their infrared performance is poor;

[0009] Therefore, designing a fixed-focus lens with one of the characteristics of low cost, large aperture, long focal length, small size, and infrared confocality has become a market development trend. Utility Model Content

[0010] In order to solve the problems existing in the above-mentioned prior art, the purpose of the utility model is to provide a fixed-focus lens with one of the characteristics of ultra-large aperture FNO≤1.11, long focal length f≥7.2mm, 4K high resolution, low cost, simple structure, small size, and no out-of-focus in the temperature range of -40℃~80℃.

[0011] To achieve the above-mentioned purpose of the utility model, the utility model provides a fixed-focus lens, which includes, in order from the object side to the image side of the optical axis: a first lens with negative optical power, a second lens with positive optical power, a third lens with positive optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with negative optical power and an eighth lens with positive optical power, a total of eight lenses,

[0012] The first lens is a convex-concave lens;

[0013] The second lens is a concave-convex lens;

[0014] The third lens is a meniscus lens;

[0015] The fourth lens is a convex-convex lens;

[0016] The fifth lens is a concave-concave lens;

[0017] The sixth lens is a convex-convex lens;

[0018] The seventh lens is a meniscus lens;

[0019] The eighth lens is a convex-concave lens;

[0020] The effective focal length f1 of the first lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: -3.62≤f1 / f≤-2.85.

[0021] According to a technical solution of the utility model, the fourth lens, the fifth lens and the sixth lens form a triplet lens.

[0022] According to a technical solution of the present utility model, the effective focal length f1 of the first lens and the effective focal length f3 of the third lens satisfy the following relationship: -1.33≤f1 / f3≤-0.88.

[0023] According to a technical solution of the present utility model, the curvature radius R11 of the object side surface of the first lens, the curvature radius R12 of the image side surface and the combined effective focal length f123 of the first lens to the third lens satisfy the following relationship: 20.6≤|R12 / R11|*f123≤27.58.

[0024] According to a technical solution of the present utility model, the effective focal length f1 of the first lens, the effective focal length f4 of the fourth lens, the effective focal length f5 of the fifth lens, the effective focal length f6 of the sixth lens and the combined effective focal length f456 of the fourth lens to the sixth lens satisfy the following relationship: 0.03≤|(f4+f5+f6) / (f1*f456)|≤0.04.

[0025] According to a technical solution of the present invention, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens and the combined effective focal length f123 of the first lens to the third lens satisfy the following relationship: |f1*f2 / f123|≥55.6.

[0026] According to a technical solution of the present utility model, the effective focal length f4 of the fourth lens and its refractive index Nd4, the effective focal length f5 of the fifth lens and its refractive index Nd5, and the effective focal length f6 of the sixth lens and its refractive index Nd6 satisfy the following relationship: 15.35≤Nd4*f4+Nd5*f5+Nd6*f6≤17.9.

[0027] According to a technical solution of the present utility model, the Abbe number Vd1 of the first lens, the Abbe number Vd2 of the second lens and the Abbe number Vd3 of the third lens and the effective focal length f2 of the second lens and the effective focal length f3 of the third lens satisfy the following relationship: 0.2≤(Vd1+Vd2+Vd3) / (f2+f3)≤0.96.

[0028] According to a technical solution of the present utility model, the combined focal length f78 of the seventh lens and the eighth lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 6.6≤f78 / f≤9.8.

[0029] According to a technical solution of the present utility model, the combined focal length f23 of the second lens and the third lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 2.1≤f23 / f≤2.6.

[0030] According to a technical solution of the present utility model, the combined focal length f234 of the second lens to the fourth lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 0.64≤f234 / f≤0.74.

[0031] According to a technical solution of the present utility model, the effective focal length f5 of the fifth lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: -0.7≤f5 / f≤-0.56.

[0032] According to a technical solution of the present utility model, the effective focal length f6 of the sixth lens and the effective focal length f of the fixed-focus lens satisfy the following relationship: 0.84≤f6 / f≤1.0.

[0033] According to a technical solution of the present utility model, the effective focal length f7 and the core thickness D7 of the seventh lens, the effective focal length f8 and the core thickness D8 of the eighth lens, and the combined focal length f678 of the sixth lens to the eighth lens satisfy the following relationship: -4.5≤(f7+f8)*(D7+D8) / f678≤-2.

[0034] According to a technical solution of the present utility model, the total optical length TTL of the fixed-focus lens and the aperture number FNO of the fixed-focus lens satisfy the following relationship: TTL / FNO≥20.

[0035] According to the solution of the utility model, by setting the fixed-focus lens to include eight lenses, and setting the optical focal lengths of the first lens to the eighth lens to be negative focal length, positive focal length, positive focal length, positive focal length, negative focal length, positive focal length, negative focal length and positive focal length respectively, the fixed-focus lens has at least one of the characteristics of ultra-large aperture FNO≤1.11, long focal length f≥7.2mm, 4K high resolution, low cost, simple structure, small size, and no out-of-focus in the temperature range of -40℃~80℃, and is particularly suitable for day and night dual-purpose security lenses with infrared performance.

[0036] By rationally configuring the ratio of the effective focal length f1 of the first lens L1 to the effective focal length f of the fixed-focus lens, it is beneficial for light of a larger angle to converge into the optical system, lengthen the focal length, and make the total effective focal length f of the optical system ≥ 7.2 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the implementation of the utility model or the technical solution in the prior art, the drawings required for the implementation are briefly introduced below. Obviously, the drawings described below are only some implementations of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 It is a structural schematic diagram of a fixed-focus lens according to Embodiment 1 of the present utility model;

[0039] Figure 2 This is a schematic structural diagram of a fixed-focus lens according to Embodiment 2 of the present utility model;

[0040] Figure 3 This is a schematic structural diagram of a fixed-focus lens according to Embodiment 3 of the present utility model;

[0041] Figure 4 It is a schematic structural diagram of a fixed-focus lens according to Embodiment 4 of the present utility model. DETAILED DESCRIPTION

[0042] In order to more clearly illustrate the implementation of the utility model or the technical solution in the prior art, the drawings required for the implementation are briefly introduced below. Obviously, the drawings described below are only some implementations of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0044] In this document, the surface of each lens closest to the subject is called the object-side surface of the lens, and the surface of each lens closest to the imaging side is called the image-side surface of the lens.

[0045] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. The implementation methods cannot be described one by one here, but the implementation methods of the present invention are not therefore limited to the following implementation methods.

[0046] like Figures 1 to 4 As shown, an embodiment of the utility model provides a fixed-focus lens, which includes, in order from the object side to the image side of the optical axis: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a protective flat glass CG, wherein the first lens L1, the second lens L2, the third lens L3, the seventh lens L7 and the eighth lens L8 are all aspherical lenses, and the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all spherical lenses.

[0047] The material of each lens is a glass-plastic mixture, which is beneficial to reducing the cost of the optical system and balancing the high and low temperature performance of the optical lens, achieving no defocus in the range of -40℃ to +80℃ while maintaining high imaging quality; at the same time, the use of glass lenses is beneficial to correcting the chromatic aberration of the optical system, improving the color saturation of the lens, and ensuring the confocality of visible light and infrared.

[0048] The first lens L1 is a convex-concave lens with negative optical power and is in a meniscus shape with the convex surface facing the object side, which is conducive to focusing incident light with a large field of view into the optical system, effectively expanding the field of view angle.

[0049] The second lens L2 is a concave-convex lens with positive optical power, which can effectively control the trend of incident light of the optical system, reduce the spherical aberration of the system, and help improve the image quality.

[0050] The third lens L3 is a meniscus lens with positive refractive power, which can effectively control the light to smoothly enter the rear of the optical system, reduce the generation of aberrations, and help improve the imaging quality.

[0051] The fourth lens L4 is a convex-convex lens with positive optical power, which is beneficial to correcting chromatic aberration, improving imaging quality, and can also make the transmission of light smoother, reduce the outer diameter of the fourth lens, and is beneficial to improving the lens assembly yield.

[0052] The fifth lens L5 is a concave-concave lens with negative power, which can be paired with the fourth lens L4 with positive power and convex-convex shape to form a cemented lens, effectively controlling the trend of light and converging light, which can not only increase the aperture of the lens, but also shorten the overall length of the lens, making the optical system more compact.

[0053] The sixth lens L6 is a convex-convex lens with positive power, which can be paired with the fifth lens L5 with negative power and concave-concave lens shape and the fourth lens L4 with positive power and convex-convex lens shape to form a triplet lens group, which can effectively control the trend of light, make the light transition smoothly, and converge the light, which helps to reduce the tolerance sensitivity of the system and improve the lens yield; it helps to achieve an ultra-large aperture, and is also beneficial for correcting chromatic aberration and balancing the impact of temperature changes on lens performance, thereby improving the imaging quality of the lens.

[0054] Furthermore, the triplet lens consisting of the fourth lens L4, the fifth lens L5 and the sixth lens L6 can effectively control the trend of light and make the light transition smoothly, which helps to reduce the tolerance sensitivity of the system and improve the lens yield.

[0055] The seventh lens L7 is a concave-convex lens with negative optical power, which can effectively control the trend of light and converge light, which is beneficial to improving the assembly yield. At the same time, it can also correct chromatic aberration, which is beneficial to improving the imaging quality.

[0056] The eighth lens L8 is a convex-concave lens with positive refractive power, which is combined with the seventh lens L7 with negative refractive power and a concave-convex lens shape to help balance various chromatic aberrations and astigmatism generated after light passes through the aperture, thereby improving the resolution of the peripheral field of view.

[0057] In some embodiments of the present invention, the aperture STO is located between the second lens L2 and the third lens L3, preferably on the image side of the second lens L2. It should be noted that the position of the aperture STO disclosed herein is only an example and is not a limitation on the aperture STOP; in other alternative embodiments, the aperture STOP may also be set at other positions according to actual needs.

[0058] In some embodiments of the present invention, the effective focal length f1 of the first lens L1 and the effective focal length f of the fixed-focus lens satisfy the following relationship: -3.62≤f1 / f≤-2.85; by reasonably configuring the effective focal length value of the first lens L1, it is beneficial for larger angles of light to converge into the optical system, lengthen the focal length, and make the total effective focal length f of the optical system ≥7.2 mm.

[0059] In some embodiments of the present invention, the effective focal length f1 of the first lens L1 and the effective focal length f3 of the third lens L3 satisfy the following relationship: -1.33≤f1 / f3≤-0.88; by reasonably controlling the ratio of the effective focal length of the first lens L1 to the effective focal length of the third lens L3, it is helpful to converge light from different fields of view, maximize the amount of light transmitted, improve the imaging brightness of the rear of the optical system, and at the same time help to reduce aberrations and improve imaging quality.

[0060] In some embodiments of the present invention, the curvature radius R11 of the object side surface of the first lens L1, the curvature radius R12 of the image side surface, and the combined effective focal length f123 of the first lens L1 to the third lens L3 satisfy the following relationship: 20.6≤|R12 / R11|*f123≤27.58; when the above relationship is satisfied, the light beam of the front group (the first lens L1 and the second lens L2) can be better received, which is beneficial to the balance of spherical aberration and astigmatism.

[0061] In some embodiments of the present invention, the effective focal length f1 of the first lens L1, the effective focal length f4 of the fourth lens L4, the effective focal length f5 of the fifth lens L5, the effective focal length f6 of the sixth lens L6 and the combined effective focal length f456 of the fourth lens L4 to the sixth lens L6 satisfy the following relationship: 0.03≤|(f4+f5+f6) / (f1*f456)|≤0.04; when the above relationship is satisfied, it is beneficial to control the height of the incident light of the fourth lens L4, compress and converge the light, and is beneficial to reduce the aberration of the optical system. At the same time, the outer diameter of the fourth lens L4 can be reduced, the longitudinal size of the lens can be controlled, and miniaturization can be achieved.

[0062] In some embodiments of the present invention, the effective focal length f1 of the first lens L1, the effective focal length f2 of the second lens L2, and the combined effective focal length f123 of the first lens L1 to the third lens L3 satisfy the following relationship: |f1*f2 / f123|≥55.6; by adjusting the absolute value of the ratio of the product of the effective focal length of the first lens L1 and the effective focal length of the second lens L2 to the combined effective focal length of the first lens L1 to the third lens L3, the field curvature generated by the lens group located in front of the aperture can be effectively corrected, thereby improving the imaging quality.

[0063] In some embodiments of the present invention, the effective focal length f4 of the fourth lens L4 and its refractive index Nd4, the effective focal length f5 of the fifth lens L5 and its refractive index Nd5, and the effective focal length f6 of the sixth lens L6 and its refractive index Nd6 satisfy the following relationship: 15.35≤Nd4*f4+Nd5*f5+Nd6*f6≤17.9, which is helpful to correct chromatic aberration, improve the imaging quality of the infrared configuration while maintaining a high imaging quality of the visible configuration, and at the same time can better correct the aberrations caused by the large aperture, improve high-order spherical aberration and coma, which is conducive to achieving 4K high resolution and making the overall resolution uniform.

[0064] In some embodiments of the present invention, the Abbe number Vd1 of the first lens L1, the Abbe number Vd2 of the second lens L2, and the Abbe number Vd3 of the third lens L3 satisfy the following relationship with the effective focal length f2 of the second lens L2 and the effective focal length f3 of the third lens L3: 0.2≤(Vd1+Vd2+Vd3) / (f2+f3)≤0.96, which helps to balance aberrations and achieve a large aperture, so that the aperture FNO≤1.10.

[0065] In some embodiments of the present invention, the combined focal length f78 of the seventh lens L7 and the eighth lens L8 and the effective focal length f of the fixed-focus lens satisfy the following relationship: 6.6≤f78 / f≤9.8, which helps to balance various chromatic aberrations and astigmatism generated after the light passes through the aperture, and improve the resolution of the peripheral field of view.

[0066] In some embodiments of the present invention, the combined focal length f23 of the second lens L2 and the third lens L3 and the effective focal length f of the fixed-focus lens satisfy the following relationship: 2.1≤f23 / f≤2.6, which helps to balance various chromatic aberrations generated when light passes through the aperture and improve imaging quality.

[0067] In some embodiments of the present invention, the combined focal length f234 of the second lens L2 to the fourth lens L4 and the effective focal length f of the fixed-focus lens satisfy the following relationship: 0.64≤f234 / f≤0.74, which helps to control the highest point of the light while balancing various chromatic aberrations and field curvatures generated when the light passes through the aperture, thereby improving imaging quality.

[0068] In some embodiments of the present invention, the effective focal length f5 of the fifth lens L5 and the effective focal length f of the fixed-focus lens satisfy the following relationship: -0.7≤f5 / f≤-0.56, which is conducive to smooth transition of light, correction of chromatic aberration and various aberrations, and reduction of the change in focal length of the lens at different temperatures, thereby achieving athermalization of the lens while improving the resolution of the optical lens.

[0069] In some embodiments of the present invention, the effective focal length f6 of the sixth lens L6 and the effective focal length f of the fixed-focus lens satisfy the following relationship: 0.84≤f6 / f≤1.0, which is conducive to smooth transition of light, correction of chromatic aberration and various aberrations, and reduction of the change in focal length of the lens at different temperatures, thereby achieving athermalization of the lens and improving the resolution capability of the optical lens.

[0070] In some embodiments of the present invention, the effective focal length f7 and the core thickness D7 of the seventh lens L7, the effective focal length f8 and the core thickness D8 of the eighth lens L8, and the combined focal length f678 of the sixth lens L6 to the eighth lens L8 satisfy the following relationship: -4.5≤(f7+f8)*(D7+D8) / f678≤-2, which is beneficial to reducing the tolerance sensitivity of the system and improving the lens assembly yield.

[0071] In some embodiments of the present invention, the total optical length TTL of the fixed-focus lens and the aperture number FNO of the fixed-focus lens satisfy the following relationship: TTL / FNO≥20. When the aperture is constant, the total length of the lens optical system can be reasonably set to facilitate miniaturization of the lens, so that TTL≤22.47mm.

[0072] Five groups of specific implementation methods are given below according to the above-mentioned settings of the utility model to specifically illustrate the fixed-focus lens according to the utility model. According to the fixed-focus lens of the utility model, there are seven lenses in total, and each cemented surface of the cemented lens is recorded as a surface, plus the aperture STO, the protective glass CG and the image surface, as well as the virtual surface that exists based on performance improvement, a total of 17 or 18 surfaces. Among them, the aperture STO is set between the fourth lens L4 and the fifth lens L5. For the convenience of description, each lens surface, the aperture STO and the protective glass CG are numbered S1, S2 to S18. And the aspheric surface satisfies the following formula:

[0073]

[0074] In the above formula, z is the axial distance from the surface to the vertex at a height y perpendicular to the optical axis along the optical axis; c represents the curvature at the vertex of the aspheric surface; k is the cone coefficient; A4, A6, A8, A 10 , A 12 , A 14 , A 16 ···represent the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, sixteenth-order···aspheric coefficients respectively.

[0075] The data of five groups of embodiments are shown in Table 1 below:

[0076] Conditional expression Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 -3.62≤f1 / f≤-2.85 -3.49 -3.41 -2.99 -2.98 -1.33≤f1 / f3≤-0.88 -1.16 -1.27 -1.08 -1.05 20.6≤|R12 / R11|*f123≤27.58 26.19 22.62 20.63 22.22 |f1*f2 / f123|≥55.6 124.00 251.28 74.29 72.09 0.03≤|(f4+f5+f6) / (f1*f456)|≤0.04 -0.03 -0.03 -0.04 -0.04 2.1≤f23 / f≤2.6 2.48 2.30 2.15 2.23 0.2≤(v1+v2+v3) / (f2+f3)≤0.96 0.50 0.29 0.83 0.79 0.64≤f234 / f≤0.74 0.67 0.68 0.72 0.65 15.35≤n4*f4+n5*f5+n6*f6≤17.9 16.10 16.31 17.47 15.78 6.6≤f78 / f≤9.8 8.02 9.27 7.12 8.74 -0.7≤f5 / f≤-0.56 -0.68 -0.63 -0.68 -0.59 0.84≤f6 / f≤1.0 0.97 0.87 0.92 0.87 -4.5≤(f7+f8)*(D7+D8) / f678≤-2 -2.42 -3.31 -4.06 -2.46 TTL / FNO≥20 20.71 20.30 20.31 20.25

[0077] Embodiment 1

[0078] Figure 1 The figure is a schematic structural diagram of a fixed-focus lens according to the first embodiment of the present invention.

[0079] In Embodiment 1, the first lens L1 is a convex-concave lens with negative power, the second lens L2 is a convex-concave lens with positive power, the third lens L3 is a convex-concave lens with positive power, the fourth lens L4 is a convex-convex lens with positive power, the fifth lens L5 is a convex-concave lens with negative power, the sixth lens L6 is a convex-convex lens with positive power, the seventh lens L7 is a convex-convex lens with negative power, and the eighth lens L8 is a convex-concave lens with positive power.

[0080] The first lens L1, the second lens L2, the third lens L3, the seventh lens L7 and the eighth lens L8 are all aspherical lenses; the stop STO is located between the second lens L2 and the third lens L3; the fourth lens L4, the fifth lens L5 and the sixth lens L6 form a triplet lens.

[0081] Table 2 lists the relevant parameters of each lens in the fixed-focus lens of this embodiment, including: surface type, curvature radius, thickness, refractive index and Abbe number of the material.

[0082] Surface serial number Surface type Curvature radius R Thickness d Refractive index Nd Abbe number Vd S1 Aspheric 4.136 1.139 1.54 55.71 S2 Aspheric 2.868 3.272 S3 Aspheric -3.682 1.015 1.64 23.53 S4 Aspheric -3.958 -0.700 S5(Aperture) Spherical Infinity 0.800 S6 Aspheric -33.370 2.362 1.64 23.53 S7 Aspheric -10.195 0.214 S8 Spherical 10.854 2.906 1.80 46.77 S9 Spherical -10.854 0.739 1.78 25.72 S10 Spherical 6.245 3.425 1.70 56.20 S11 Spherical -18.155 0.600 S12 Aspheric -2.544 1.003 1.64 23.53 S13 Aspheric -3.392 0.080 S14 Aspheric 3.660 1.122 1.54 55.71 S15 Aspheric 4.786 3.490 S16 Spherical Infinity 0.80 1.52 64.21 S17 Spherical Infinity 0.20 S18 (image plane) Spherical Infinity 0.00

[0083] Table 2

[0084] Table 3 lists the aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment, including: the quadratic surface constant K, the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12 , 14th-order aspheric coefficient A 14 and the sixteenth-order aspheric coefficient A 16 .

[0085]

[0086]

[0087] Table 3

[0088] In the first embodiment, the aperture number FNO of the fixed-focus lens is 1.08, the effective focal length f is 7.26, and the total optical length TTL is 22.47 mm.

[0089] Combination Figure 1 As shown in Tables 1 to 3 above, the first embodiment of the present invention is a fixed-focus lens having at least one of the following characteristics: ultra-large aperture FNO≤1.11, long focal length f≥7.2mm, 4K high resolution, low cost, simple structure, small size, and no out-of-focus in the temperature range of -40°C to 80°C. The lens is particularly suitable for day and night dual-purpose security lenses with infrared performance.

[0090] Embodiment 2

[0091] Figure 2 It is a structural schematic diagram of a fixed-focus lens according to Embodiment 2 of the present utility model.

[0092] In the second embodiment, the first lens L1 is a convex-concave lens with negative power, the second lens L2 is a convex-concave lens with positive power, the third lens L3 is a convex-concave lens with positive power, the fourth lens L4 is a convex-convex lens with positive power, the fifth lens L5 is a convex-concave lens with negative power, the sixth lens L6 is a convex-convex lens with positive power, the seventh lens L7 is a convex-convex lens with negative power, and the eighth lens L8 is a convex-concave lens with positive power.

[0093] The first lens L1, the second lens L2, the third lens L3, the seventh lens L7 and the eighth lens L8 are all aspherical lenses; the stop STO is located between the second lens L2 and the third lens L3; the fourth lens L4, the fifth lens L5 and the sixth lens L6 form a triplet lens.

[0094] Table 4 lists the relevant parameters of each lens in the fixed-focus lens of this embodiment, including: surface type, radius of curvature, thickness, refractive index and Abbe number of the material.

[0095]

[0096]

[0097] Table 4

[0098] Table 5 lists the aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment, including: the quadratic surface constant K, the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12 , Fourteenth-order aspheric coefficient A 14 and the sixteenth-order aspheric coefficient A 16 .

[0099] Surface number K <![CDATA[A4]]> <![CDATA[A6]]> <![CDATA[A8]]> <![CDATA[A 10 ]]> <![CDATA[A 12 ]]> <![CDATA[A 14 ]]> <![CDATA[A 16 ]]> S1 -0.35 -2.13E-03 -7.93E-05 -3.94E-07 -1.30E-08 0.00E+00 0.00E+00 0.00E+00 S2 -0.66 -2.24E-03 -1.08E-04 -4.78E-06 -7.29E-09 2.86E-08 -2.59E-09 0.00E+00 S3 -0.76 1.56E-03 4.51E-04 -2.04E-05 -6.31E-07 4.05E-08 -3.60E-10 0.00E+00 S4 -1.35 2.62E-03 1.88E-04 4.04E-06 -7.85E-07 -2.59E-08 2.43E-09 0.00E+00 S6 -8.31 8.41E-04 -1.52E-05 3.28E-07 -3.41E-08 -7.58E-10 -3.01E-11 0.00E+00 S7 3.09 -1.09E-03 6.85E-05 -1.73E-06 -2.35E-08 4.53E-09 -1.34E-10 0.00E+00 S12 -5.07 3.57E-03 -1.62E-04 7.06E-06 -2.35E-07 3.26E-09 0.00E+00 0.00E+00 S13 -5.75 2.34E-03 -5.27E-05 -4.66E-06 4.64E-07 -2.05E-08 3.50E-10 0.00E+00 S14 -7.55 6.22E-05 -3.26E-04 1.69E-05 -1.95E-06 1.15E-07 -2.04E-09 0.00E+00 S15 -15.95 1.19E-03 -2.24E-04 -1.27E-06 4.46E-07 4.25E-09 -4.56E-10 0.00E+00

[0100] Table 5

[0101] In the second embodiment, the aperture number FNO of the fixed-focus lens is 1.11, the effective focal length f is 7.31, and the total optical length TTL is 22.47 mm.

[0102] Combination Figure 2 As shown in Tables 1, 4 and 5 above, the second embodiment is a fixed-focus lens having at least one of the following characteristics: ultra-large aperture FNO≤1.11, long focal length f≥7.2mm, 4K high resolution, low cost, simple structure, small size, and no out-of-focus in the temperature range of -40°C to 80°C. The lens is particularly suitable for day and night dual-purpose security lenses with infrared performance.

[0103] Embodiment 3

[0104] Figure 3 It is a structural schematic diagram of a fixed-focus lens in Embodiment 3 of the present utility model.

[0105] In embodiment 3, the first lens L1 is a convex-concave lens with negative power, the second lens L2 is a convex-concave lens with positive power, the third lens L3 is a convex-concave lens with positive power, the fourth lens L4 is a convex-convex lens with positive power, the fifth lens L5 is a convex-concave lens with negative power, the sixth lens L6 is a convex-convex lens with positive power, the seventh lens L7 is a convex-convex lens with negative power, and the eighth lens L8 is a convex-concave lens with positive power.

[0106] The first lens L1, the second lens L2, the third lens L3, the seventh lens L7 and the eighth lens L8 are all aspherical lenses; the stop STO is located between the second lens L2 and the third lens L3; the fourth lens L4, the fifth lens L5 and the sixth lens L6 form a triplet lens.

[0107] Table 6 lists the relevant parameters of each lens in the fixed-focus lens of this embodiment, including: surface type, radius of curvature, thickness, refractive index and Abbe number of the material.

[0108] Surface serial number Surface type Curvature radius R Thickness d Refractive index Nd Abbe number Vd S1 Aspheric 4.195 0.925 1.53 56.07 S2 Aspheric 2.848 3.113 S3 Aspheric -3.806 1.093 1.64 23.97 S4 Aspheric -4.005 -0.700 S5(Aperture) Spherical Infinity 0.793 S6 Aspheric -43.470 2.446 1.64 23.09 S7 Aspheric -10.163 0.064 S8 Spherical 10.315 2.958 1.82 46.57 S9 Spherical -18.273 0.600 1.85 23.79 S10 Spherical 5.545 3.786 1.68 55.56 S11 Spherical -18.467 0.510 S12 Aspheric -2.613 0.979 1.66 20.38 S13 Aspheric -3.405 0.060 S14 Aspheric 3.638 1.348 1.54 55.98 S15 Aspheric 4.572 3.494 S16 Spherical Infinity 0.80 1.52 64.21 S17 Spherical Infinity 0.20 S18 (image plane) Spherical Infinity 0.00

[0109] Table 6

[0110] Table 7 lists the aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment, including: the quadratic surface constant K, the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12 , 14th-order aspheric coefficient A 14 and the sixteenth-order aspheric coefficient A 16 .

[0111]

[0112]

[0113] Table 7

[0114] In the third embodiment, the aperture number FNO of the fixed-focus lens is 1.11, the effective focal length f is 7.25, and the total optical length TTL is 22.47 mm.

[0115] Combination Figure 3 As shown in Tables 1, 6 and 7 above, the third embodiment of the present invention is a fixed-focus lens having at least one of the following characteristics: ultra-large aperture FNO≤1.11, long focal length f≥7.2mm, 4K high resolution, low cost, simple structure, small size, and no out-of-focus in the temperature range of -40°C to 80°C. The lens is particularly suitable for day and night dual-purpose security lenses with infrared performance.

[0116] Embodiment 4

[0117] Figure 4 It is a schematic structural diagram of a fixed-focus lens according to Embodiment 4 of the present utility model.

[0118] In embodiment 4, the first lens L1 is a convex-concave lens with negative power, the second lens L2 is a convex-concave lens with positive power, the third lens L3 is a convex-concave lens with positive power, the fourth lens L4 is a convex-convex lens with positive power, the fifth lens L5 is a convex-concave lens with negative power, the sixth lens L6 is a convex-convex lens with positive power, the seventh lens L7 is a convex-convex lens with negative power, and the eighth lens L8 is a convex-concave lens with positive power.

[0119] The first lens L1, the second lens L2, the third lens L3, the seventh lens L7 and the eighth lens L8 are all aspherical lenses; the stop STO is located between the second lens L2 and the third lens L3; the fourth lens L4, the fifth lens L5 and the sixth lens L6 form a triplet lens.

[0120] Table 8 lists the relevant parameters of each lens in the fixed-focus lens of this embodiment, including: surface type, curvature radius, thickness, refractive index and Abbe number of the material.

[0121]

[0122]

[0123] Table 8

[0124] Table 9 lists the aspheric coefficients of the aspheric lenses of the fixed focus lens of this embodiment, including: the quadratic surface constant K, the fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth-order aspheric coefficient A8, the tenth-order aspheric coefficient A 10 , 12th-order aspheric coefficient A 12 , 14th-order aspheric coefficient A 14 and the sixteenth-order aspheric coefficient A 16 .

[0125] Surface number K <![CDATA[A4]]> <![CDATA[A6]]> <![CDATA[A8]]> <![CDATA[A 10 ]]> <![CDATA[A 12 ]]> <![CDATA[A 14 ]]> <![CDATA[A 16 ]]> S1 -0.43 -3.29E-03 -6.25E-05 9.38E-07 0.00E+00 0.00E+00 0.00E+00 0.00E+00 S2 -0.71 -3.52E-03 -7.76E-05 -2.95E-06 -2.66E-08 2.81E-08 -2.40E-09 0.00E+00 S3 -0.78 1.61E-03 4.62E-04 -2.07E-05 -6.53E-07 4.16E-08 -5.90E-10 0.00E+00 S4 -1.36 2.65E-03 1.99E-04 4.62E-06 -7.52E-07 -2.58E-08 2.24E-09 0.00E+00 S6 43.12 9.38E-04 -1.37E-05 5.56E-07 -2.40E-08 -5.82E-10 -2.80E-11 0.00E+00 S7 3.12 -1.17E-03 7.23E-05 -1.83E-06 -2.36E-08 4.56E-09 -1.17E-10 0.00E+00 S12 -5.43 3.70E-03 -1.48E-04 7.17E-06 -2.41E-07 4.22E-09 -3.29E-12 0.00E+00 S13 -5.94 2.53E-03 -4.93E-05 -4.19E-06 4.94E-07 -2.14E-08 3.56E-10 0.00E+00 S14 -7.13 -1.75E-04 -3.58E-04 1.61E-05 -1.79E-06 1.20E-07 -2.48E-09 0.00E+00 S15 -14.63 9.13E-04 -2.80E-04 2.56E-06 6.05E-07 -1.33E-08 -1.11E-10 0.00E+00

[0126] Table 9

[0127] In the fourth embodiment, the aperture number FNO of the fixed-focus lens is 1.11, the effective focal length f is 7.21, and the total optical length TTL is 22.38 mm.

[0128] Combination Figure 4 As shown in Tables 1, 8 and 9 above, the fourth embodiment of the present invention is a fixed-focus lens having at least one of the following characteristics: ultra-large aperture FNO≤1.11, long focal length f≥7.2mm, 4K high resolution, low cost, simple structure, small size, and no out-of-focus in the temperature range of -40°C to 80°C. The lens is particularly suitable for day and night dual-purpose security lenses with infrared performance.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fixed-focus lens, comprising, in order from the object side to the image side along the optical axis: A first lens (L1) with negative focal power, a second lens (L2) with positive focal power, a third lens (L3) with positive focal power, a fourth lens (L4) with positive focal power, a fifth lens (L5) with negative focal power, a sixth lens (L6) with positive focal power, a seventh lens (L7) with negative focal power and an eighth lens (L8) with positive focal power, a total of eight lenses, characterized in that: The first lens (L1) is a convex-concave lens; The second lens (L2) is a meniscus lens; The third lens (L3) is a meniscus lens; The fourth lens (L4) is a convex-convex lens; The fifth lens (L5) is a concave-concave lens; The sixth lens (L6) is a convex-convex lens; The seventh lens (L7) is a meniscus lens; The eighth lens (L8) is a convex-concave lens; The effective focal length f1 of the first lens (L1) and the effective focal length f of the fixed-focus lens satisfy the following relationship: -3.62≤f1 / f≤-2.

85.

2. The fixed-focus lens according to claim 1, characterized in that: The fourth lens (L4), the fifth lens (L5) and the sixth lens (L6) form a triplet lens.

3. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length f1 of the first lens (L1) and the effective focal length f3 of the third lens (L3) satisfy the following relationship: -1.33≤f1 / f3≤-0.

88.

4. The fixed-focus lens according to claim 1 or 2, characterized in that: The curvature radius R11 of the object side surface and the curvature radius R12 of the image side surface of the first lens (L1) and the combined effective focal length f123 of the first lens (L1) to the third lens (L3) satisfy the following relationship: 20.6≤|R12 / R11|*f123≤27.

58.

5. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length f1 of the first lens (L1), the effective focal length f4 of the fourth lens (L4), the effective focal length f5 of the fifth lens (L5), the effective focal length f6 of the sixth lens (L6), and the combined effective focal length f456 of the fourth lens (L4) to the sixth lens (L6) satisfy the following relationship: 0.03≤|(f4+f5+f6) / (f1*f456)|≤0.

04.

6. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length f1 of the first lens (L1), the effective focal length f2 of the second lens (L2), and the combined effective focal length f123 of the first lens (L1) to the third lens (L3) satisfy the following relationship: |f1*f2 / f123|≥55.

6.

7. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length f4 of the fourth lens (L4) and its refractive index Nd4, the effective focal length f5 of the fifth lens (L5) and its refractive index Nd5, and the effective focal length f6 of the sixth lens (L6) and its refractive index Nd6 satisfy the following relationship: 15.35≤Nd4*f4+Nd5*f5+Nd6*f6≤17.

9.

8. The fixed-focus lens according to claim 1 or 2, characterized in that: The Abbe number Vd1 of the first lens (L1), the Abbe number Vd2 of the second lens (L2), and the Abbe number Vd3 of the third lens (L3) and the effective focal length f2 of the second lens (L2), and the effective focal length f3 of the third lens (L3) satisfy the following relationship: 0.2≤(Vd1+Vd2+Vd3) / (f2+f3)≤0.

96.

9. The fixed-focus lens according to claim 1 or 2, characterized in that: The combined focal length f78 of the seventh lens (L7) and the eighth lens (L8) and the effective focal length f of the fixed-focus lens satisfy the following relationship: 6.6≤f78 / f≤9.

8.

10. The fixed-focus lens according to claim 1 or 2, characterized in that: The combined focal length f23 of the second lens (L2) and the third lens (L3) and the effective focal length f of the fixed-focus lens satisfy the following relationship: 2.1≤f23 / f≤2.

6.

11. The fixed-focus lens according to claim 1 or 2, characterized in that: The combined focal length f234 of the second lens (L2) to the fourth lens (L4) and the effective focal length f of the fixed-focus lens satisfy the following relationship: 0.64≤f234 / f≤0.

74.

12. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length f5 of the fifth lens (L5) and the effective focal length f of the fixed-focus lens satisfy the following relationship: -0.7≤f5 / f≤-0.

56.

13. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length f6 of the sixth lens (L6) and the effective focal length f of the fixed-focus lens satisfy the following relationship: 0.84≤f6 / f≤1.

0.

14. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length f7 and the core thickness D7 of the seventh lens (L7), the effective focal length f8 and the core thickness D8 of the eighth lens (L8), and the combined focal length f678 of the sixth lens (L6) to the eighth lens (L8) satisfy the following relationship: -4.5≤(f7+f8)*(D7+D8) / f678≤-2.

15. The fixed-focus lens according to claim 1 or 2, characterized in that: The total optical length TTL of the fixed-focus lens and the aperture number FNO of the fixed-focus lens satisfy the following relationship: TTL / FNO≥20.

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