Prime lens

Abstract

The utility model relates to a prime lens, which sequentially comprises a first lens with negative focal power, a second lens with positive focal power, a third lens with negative focal power, a fourth lens with positive focal power, a fifth lens with positive focal power and a sixth lens with negative focal power along an optical axis from an object side to an image side, totally six lenses, the image side surface of the first lens is a concave surface; the second lens is a convex lens; the third lens is a concave-convex lens; the image side surface of the fourth lens is a convex surface; the fifth lens is a convex-convex lens; the sixth lens is a concave-convex lens; the effective focal length F1 of the first lens and the effective focal length F of the prime lens meet the following relation: F1 / F is more than or equal to-1.58 and less than or equal to-1.40; the effective focal length F3 of the third lens and the effective focal length F of the prime lens meet the following relation:-7.36 < = F3 / F < =-5.14. The prime lens of the utility model has at least one of the characteristics of high resolution, low cost, small volume, day and night use and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of imaging lenses, in particular to a fixed-focus lens with high resolution, low cost, small size and dual-purpose for day and night. Background Art

[0002] With the increasing popularity of security monitoring facilities, monitoring equipment has higher and higher requirements for monitoring environment and images, and monitoring equipment needs to provide all-weather monitoring images. No defocus in high and low temperature environments ensures that the lens still has high imaging quality under harsh weather conditions; infrared confocal can ensure that monitoring equipment can be used day and night.

[0003] However, the current security fixed-focus lenses still have the following disadvantages:

[0004] 1. The lens configuration of the fixed-focus lens in the prior art is difficult to make good correction for system aberrations, and the imaging quality is poor;

[0005] 2. The fixed-focus lens in the prior art is too long and too large in size, which makes the overall cost and weight of the lens too high;

[0006] 3. It is difficult to optimize the design of the infrared part of the fixed-focus lens in the prior art while achieving high and low temperature without defocusing.

[0007] Therefore, the current market needs a fixed-focus lens that meets at least one of the following characteristics: high resolution, low cost, small size, and day and night use. Utility Model Content

[0008] In order to solve the above problems in the prior art, the purpose of the present invention is to provide a fixed-focus lens having at least one of the characteristics of high resolution, low cost, small size, and day and night use.

[0009] 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 negative optical power, a fourth lens with positive optical power, a fifth lens with positive optical power and a sixth lens with negative optical power, a total of six lenses,

[0010] The image side surface of the first lens is a concave surface;

[0011] The second lens is a convex-convex lens;

[0012] The third lens is a meniscus lens;

[0013] The image side surface of the fourth lens is a convex surface;

[0014] The fifth lens is a convex-convex lens;

[0015] The sixth lens is a meniscus lens;

[0016] The effective focal length F1 of the first lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: -1.58≤F1 / F≤-1.40;

[0017] The effective focal length F3 of the third lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: -7.36≤F3 / F≤-5.14.

[0018] According to one aspect of the utility model, the fifth lens and the sixth lens form a doublet lens.

[0019] According to one aspect of the present invention, the effective focal length F2 of the second lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: 2.34≤F2 / F≤3.14.

[0020] According to one aspect of the present invention, the object side curvature radius R21 and the image side curvature radius R22 of the second lens and the effective focal length F of the fixed focus lens satisfy the following relationship: -2.43 mm -1 ≤R21 / R22 / F≤-0.18mm -1 .

[0021] According to one aspect of the utility model, the object side curvature radius R31, the image side curvature radius R32 of the third lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: -4.77≤(R31+R32) / F≤-3.88.

[0022] According to one aspect of the present invention, the effective focal length F6 of the sixth lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: -2.42≤F6 / F≤-1.66.

[0023] According to one aspect of the present invention, the effective focal length F5 of the fifth lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: 1.20≤F5 / F≤1.36.

[0024] According to one aspect of the present invention, the Abbe number vd5 of the fifth lens, the Abbe number vd6 of the sixth lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: 8.88 mm -1 ≤(V5-V6) / F≤9.19mm -1 .

[0025] According to one aspect of the present invention, the total optical length TLL of the fixed-focus lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: 5.39≤TTL / F≤5.83.

[0026] According to one aspect of the present invention, the back focal length BFL of the fixed-focus lens and the total optical length TLL of the fixed-focus lens satisfy the following relationship: 0.30≤BFL / TTL≤0.33.

[0027] According to one aspect of the present invention, the effective focal length F2 of the second lens, the effective focal length F3 of the third lens and the effective focal length F1 of the first lens satisfy the following relationship: 1.86≤(F2+F3) / F1≤2.70.

[0028] According to one aspect of the present invention, the total optical length TLL of the fixed-focus lens and the total image height H of the fixed-focus lens satisfy the following relationship: 3.15≤TTL / H≤3.36.

[0029] According to one aspect of the present invention, the effective focal length F of the fixed-focus lens and the full image height H of the fixed-focus lens satisfy the following relationship: 0.56≤F / H≤0.59.

[0030] According to one aspect of the present invention, the combined focal length F123 of the first lens, the second lens and the third lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: -1.23≤F123 / F4≤-0.91.

[0031] According to one aspect of the present invention, the effective focal length F4 of the fourth lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: 2.81≤F4 / F≤3.13.

[0032] According to the scheme of the utility model, by setting the fixed-focus lens to include six lenses, and setting the optical focal lengths of the first lens to the sixth lens to be negative focal length, positive focal length, negative focal length, positive focal length, positive focal length and negative focal length respectively, and reasonably configuring the effective focal lengths of the first lens and the third lens, it is beneficial to improve the imaging quality of the optical system, ensure that the fixed-focus lens has a good imaging effect, and make the fixed-focus lens have infrared performance and the characteristics of day and night use. At the same time, it also has at least one of the characteristics of large wide angle, small size, high resolution, and no out-of-focus in an environment of -40℃ to 80℃, so as to meet the imaging needs of security lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 It is a structural schematic diagram of a fixed-focus lens according to Embodiment 1 of the present utility model;

[0035] Figure 2 This is a schematic structural diagram of a fixed-focus lens according to Embodiment 2 of the present utility model;

[0036] Figure 3 This is a schematic structural diagram of a fixed-focus lens according to Embodiment 3 of the present utility model;

[0037] Figure 4 It is a schematic structural diagram of a fixed-focus lens according to Embodiment 4 of the present utility model. DETAILED DESCRIPTION

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] like Figures 1 to 4 As shown, an embodiment of the utility model provides a fixed-focus lens, which includes, in sequence along the direction from the object side to the image side of the optical axis: a first lens L1, a second lens L2, a third lens L3, an aperture STOP, a fourth lens L4, a fifth lens L5, a sixth lens L6 and a protective flat glass CG, wherein the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are all spherical lenses.

[0043] The image side surface of the first lens L1 is concave and has negative optical power, which can focus incident light with a large field of view as much as possible into the optical system, effectively expanding the field of view angle to achieve a field of view angle FOV ≥ 116°;

[0044] The second lens L2 is a convex-convex lens with positive refractive power, which can effectively control the incident light trend of the optical system and reduce the system aberration, thereby improving the image quality;

[0045] The third lens L3 is a meniscus lens with positive power, which can allow light to smoothly enter the rear of the optical system, reduce the generation of spherical aberration, balance the field curvature of the system, and is conducive to improving the imaging quality.

[0046] The image-side surface of the fourth lens L4 is convex and has positive optical power, which can effectively control the trend of light, converge light, and correct chromatic aberration, thereby facilitating improvement of imaging quality.

[0047] The fifth lens L5 is a convex-convex lens with positive power, and the sixth lens L6 is a concave-convex lens with negative power. The fifth lens L5 and the sixth lens L6 form a doublet lens, which can effectively control the trend of light and converge light, and shorten the overall length of the fixed-focus lens, making the optical system more compact.

[0048] In the embodiment of the utility model, the aperture STOP is located between the third lens L3 and the fourth lens L4, which can effectively converge the amount of light entering the optical system, shorten the total length of the optical system, and reduce the maximum aperture of the front and rear lens groups. It should be noted that the position of the aperture STO disclosed here is only an example and is not a limitation on the aperture STOP; in other alternative embodiments, the aperture STOP can also be set at other positions according to actual needs.

[0049] 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: -1.58≤F1 / F≤-1.40. Reasonable configuration of the effective focal length of the first lens L1 is conducive to converging large-angle light into the optical system, thereby expanding the field of view of the optical system, so that the field of view FOV ≥ 116°

[0050] In some embodiments of the present invention, the effective focal length F3 of the third lens L3 and the effective focal length F of the fixed-focus lens satisfy the following relationship: -7.36≤F3 / F≤-5.14. Reasonable configuration of the effective focal length of the third lens L3 can better correct the field curvature of the system, which is conducive to achieving high resolution and making the overall resolution of the fixed-focus lens more uniform.

[0051] In some embodiments of the present invention, the effective focal length F2 of the second lens L2 and the effective focal length F of the fixed-focus lens satisfy the following relationship: 2.34≤F2 / F≤3.14. Reasonable configuration of the effective focal length of the second lens L2 can better correct the field curvature of the system, which is conducive to achieving high resolution and making the overall resolution of the fixed-focus lens more uniform.

[0052] In some embodiments of the present invention, the object side curvature radius R21, the image side curvature radius R22 of the second lens L2 and the effective focal length F of the fixed focus lens satisfy the following relationship: -2.43 mm -1 ≤R21 / R22 / F≤-0.18mm -1 Reasonable control of the curvature radii of the object side and image side of the second lens L2 helps to converge light from different fields of view, effectively ensures the maximum amount of light passing, improves the imaging brightness behind the optical system, and is also beneficial to reduce the generation of aberrations and balance the spherical aberration, thereby improving the imaging quality.

[0053] In some embodiments of the present invention, the object side curvature radius R31, the image side curvature radius R32 of the third lens L3 and the effective focal length F of the fixed-focus lens satisfy the following relationship: -4.77≤(R31+R32) / F≤-3.88. Reasonable control of the curvature radii of the object side and the image side of the third lens can well receive the front group of light beams, compensate for the spherical aberration introduced by the first two lenses, and further correct the aberration caused by the front lens group.

[0054] 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: -2.42≤F6 / F≤-1.66;

[0055] 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: 1.20≤F5 / F≤1.36.

[0056] By properly configuring the optical power, effective focal length F5 of the fifth lens element L5 and the optical power, effective focal length F6 of the sixth lens element L6, it helps to balance various aberrations and improve imaging quality.

[0057] In some embodiments of the present invention, the Abbe number vd5 of the fifth lens L5, the Abbe number vd6 of the sixth lens L6 and the effective focal length F of the fixed-focus lens satisfy the following relationship: 8.88 mm -1 ≤(V5-V6) / F≤9.19mm -1 By rationally configuring the ratio of the difference in Abbe numbers of the fifth lens element L5 and the sixth lens element L6 to the total effective focal length of the optical system, it helps to balance chromatic aberration, improve imaging quality, and achieve infrared confocality.

[0058] In some embodiments of the present invention, the total optical length TLL of the fixed-focus lens and the effective focal length F of the fixed-focus lens satisfy the following relationship: 5.39≤TTL / F≤5.83. When the effective focal length F is constant, by reasonably setting the total optical length of the fixed-focus lens, it is beneficial to achieve miniaturization of the lens and realize TTL≤23mm.

[0059] In some embodiments of the present invention, the back focal length BFL of the fixed-focus lens and the total optical length TLL of the fixed-focus lens satisfy the following relationship: 0.30≤BFL / TTL≤0.33, which is conducive to making the fixed-focus lens have a longer back focal length while achieving miniaturization, helps to reserve space for the installation of optical components, facilitates the assembly of optical lenses, and avoids interference.

[0060] In some embodiments of the present invention, the effective focal length F2 of the second lens L2, the effective focal length F3 of the third lens L3, and the effective focal length F1 of the first lens L1 satisfy the following relationship: 1.86≤(F2+F3) / F1≤2.70. By reasonably controlling the focal length of the lens before the aperture, the trend of light can be effectively controlled, and at the same time, the overall aperture of the system light can be reduced, thereby realizing the longitudinal miniaturization of the fixed-focus lens.

[0061] In some embodiments of the present invention, the total optical length TLL of the fixed-focus lens and the total image height H of the fixed-focus lens satisfy the following relationship: 3.15≤TTL / H≤3.36. When the image height is constant, the total optical length of the fixed-focus lens can be reasonably set to facilitate further miniaturization.

[0062] In some embodiments of the present invention, the effective focal length F of the fixed-focus lens and the total image height H of the fixed-focus lens satisfy the following relationship: 0.56≤F / H≤0.59. Reasonable configuration of the total effective focal length and image height of the optical system helps to reduce the distortion of the optical system.

[0063] In some embodiments of the present invention, the combined focal length F123 of the first lens L1, the second lens L2 and the third lens L3 and the effective focal length F of the fixed-focus lens satisfy the following relationship: -1.23≤F123 / F4≤-0.91. Reasonable configuration of the combined effective focal lengths of the first lens L1 to the third lens L3 and the effective focal length of the fourth lens can reduce the variation of the focal length of the lens at different temperatures, which is conducive to achieving athermalization of the lens.

[0064] In some embodiments of the present invention, the effective focal length F4 of the fourth lens L4 and the effective focal length F of the fixed-focus lens satisfy the following relationship: 2.81≤F4 / F≤3.13. By controlling the ratio of the effective focal length value of the fourth lens L4 to the effective focal length F of the fixed-focus lens, it is beneficial to achieve a smooth transition of light, correct chromatic aberration and various aberrations, and enhance the resolution capability of the optical lens; at the same time, the tolerance sensitivity of the system is reduced, which is beneficial to improve the lens assembly yield.

[0065] In some embodiments of the utility model, the lens materials of the six lenses are all glass materials. The glass material parameters change little with temperature, which is beneficial to balancing the high and low temperature performance of the fixed-focus lens, achieving no out-of-focus in the range of -40°C to +80°C 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.

[0066] Four groups of specific implementations are given below based on the above-mentioned configuration of the utility model to specifically illustrate the fixed-focus lens according to the utility model. The fixed-focus lens according to the utility model has a total of six lenses, each cemented surface of the cemented lens is recorded as a surface, plus the aperture STO, the protective glass CG and the image surface IMG, a total of 15 surfaces. Among them, the aperture STO is set between the third lens L3 and the fourth lens L4. For the convenience of description, each lens surface, the aperture STO and the protective glass CG are numbered S1, S2 to S15.

[0067] Four sets of example data are shown in Table 1 below:

[0068] Conditional expression Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 -1.58≤F1 / F≤-1.40 -1.500 -1.432 -1.494 -1.551 -7.36≤F3 / F≤-5.14 -5.514 -6.001 -6.500 -6.992 2.34≤F2 / F≤3.14 2.502 2.477 2.694 3.015 <![CDATA[-2.43≤R21 / R22 / F≤-0.18(mm -1 )]]> -0.181 -0.262 -0.426 -1.420 -4.77≤(R31+R32) / F≤-3.88 -4.730 -4.729 -4.673 -4.575 -2.42≤F6 / F≤-1.66 -1.784 -1.965 -2.128 -2.292 1.20≤F5 / F≤1.36 1.227 1.245 1.304 1.335 <![CDATA[8.88≤(V5-V6) / F≤9.19(mm -1 )]]> 9.069 8.964 8.931 9.134 5.39≤TTL / F≤5.83 5.716 5.464 5.629 5.756 0.30≤BFL / TTL≤0.33 0.311 0.321 0.318 0.318 1.86≤(F2+F3) / F1≤2.70 2.007 2.461 2.547 2.564 3.15≤TTL / H≤3.36 3.326 3.186 3.290 3.281 0.56≤F / H≤0.59 0.582 0.583 0.584 0.570 -1.23≤F123 / F4≤-0.91 -1.179 -1.140 -1.047 -0.965 2.81≤F4 / F≤3.13 2.869 2.901 3.082 3.026

[0069] Embodiment 1

[0070] Figure 1 The figure is a schematic structural diagram of a fixed-focus lens according to the first embodiment of the present invention.

[0071] In Embodiment 1, the first lens L1 is a meniscus lens with negative power, the second lens L2 is a convex-convex lens with positive power, the third lens L3 is a meniscus lens with negative power, the fourth lens L4 is a convex-convex lens with positive power, the fifth lens L5 is a convex-convex lens with positive power, and the sixth lens L6 is a meniscus lens with negative power.

[0072] The above six lenses are all spherical lenses.

[0073] 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.

[0074]

[0075]

[0076] Table 2

[0077] In the first embodiment, the aperture number FNO of the fixed-focus lens is 2.082, the field of view FOV is 116°, the effective focal length F is 4.02, and the total optical length TTL is 22.95 mm.

[0078] Combination Figure 1 As shown in Table 1 and Table 2 above, the first embodiment of the present invention is a fixed-focus lens having at least one of the characteristics of wide angle, small size, high resolution, no out-of-focus in an environment of -40°C to 80°C, infrared performance, and day and night use.

[0079] Embodiment 2

[0080] Figure 2 It is a structural schematic diagram of a fixed-focus lens according to Embodiment 2 of the present utility model.

[0081] In the second embodiment, the first lens L1 is a meniscus lens with negative power, the second lens L2 is a convex-convex lens with positive power, the third lens L3 is a meniscus lens with negative power, the fourth lens L4 is a convex-convex lens with positive power, the fifth lens L5 is a convex-convex lens with positive power, and the sixth lens L6 is a meniscus lens with negative power.

[0082] The above six lenses are all spherical lenses.

[0083] Table 3 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.

[0084]

[0085]

[0086] Table 3

[0087] In the second embodiment, the aperture number FNO of the fixed-focus lens is 2.080, the field of view FOV is 116°, the effective focal length F is 4.06, and the total optical length TTL is 22.20 mm.

[0088] Combination Figure 2 As shown in Table 1 and Table 3 above, the second embodiment of the present invention is a fixed-focus lens having at least one of the characteristics of wide angle, small size, high resolution, no out-of-focus in an environment of -40°C to 80°C, infrared performance, and day and night use.

[0089] Embodiment 3

[0090] Figure 3 It is a schematic structural diagram of a fixed-focus lens according to Embodiment 3 of the present invention.

[0091] In the third embodiment, the first lens L1 is a meniscus lens with negative power, the second lens L2 is a convex-convex lens with positive power, the third lens L3 is a meniscus lens with negative power, the fourth lens L4 is a meniscus lens with positive power, the fifth lens L5 is a convex-convex lens with positive power, and the sixth lens L6 is a meniscus lens with negative power.

[0092] The above six lenses are all spherical lenses.

[0093] 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.

[0094]

[0095]

[0096] Table 4

[0097] In the third embodiment, the aperture number FNO of the fixed-focus lens is 2.083, the field of view FOV is 116°, the effective focal length F is 4.08, and the total optical length TTL is 22.95 mm.

[0098] Combination Figure 3 As shown in Table 1 and Table 4 above, the third embodiment of the present invention is a fixed-focus lens having at least one of the characteristics of wide angle, small size, high resolution, no out-of-focus in an environment of -40°C to 80°C, infrared performance, and day and night use.

[0099] Embodiment 4

[0100] Figure 4 It is a schematic structural diagram of a fixed-focus lens according to Embodiment 4 of the present utility model.

[0101] In embodiment 4, the first lens L1 is a convex-concave lens with negative power, the second lens L2 is a convex-convex lens with positive power, the third lens L3 is a convex-convex lens with negative power, the fourth lens L4 is a convex-convex lens with positive power, the fifth lens L5 is a convex-convex lens with positive power, and the sixth lens L6 is a convex-convex lens with negative power.

[0102] The above six lenses are all spherical lenses.

[0103] Table 5 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.

[0104] Surface serial number Surface type Curvature radius R Thickness d Refractive index Nd Abbe number Vd S1 Spherical 101.089 0.67 1.52 64.21 S2 Spherical 3.103 2.54 S3 Spherical 67.967 1.28 1.85 23.79 S4 Spherical -12.006 0.21 S5 Spherical -6.378 3.97 1.70 41.14 S6 Spherical -11.865 1.64 S7(STOP) Spherical Infinity 0.06 S8 Spherical 114.388 1.23 1.50 81.59 S9 Spherical -6.326 0.06 S10 Spherical 11.470 2.24 1.64 60.21 S11 Spherical -4.498 1.77 1.85 23.79 S12 Spherical -12.516 6.30 S13 Spherical Infinity 0.80 1.52 64.21 S14 Spherical Infinity 0.20 S15(IMA) Spherical Infinity 0.00

[0105] Table 5

[0106] In the fourth embodiment, the aperture number FNO of the fixed-focus lens is 2.084, the field of view FOV is 116°, the effective focal length F is 3.99, and the total optical length TTL is 22.95 mm.

[0107] Combination Figure 4 As shown in Table 1 and Table 5 above, the fourth embodiment of the present invention is a fixed-focus lens having at least one of the characteristics of wide angle, small size, high resolution, no out-of-focus in an environment of -40°C to 80°C, infrared performance, and day and night use.

[0108] 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 optical power, a second lens (L2) with positive optical power, a third lens (L3) with negative optical power, a fourth lens (L4) with positive optical power, a fifth lens (L5) with positive optical power and a sixth lens (L6) with negative optical power, a total of six lenses, characterized in that: The image side surface of the first lens (L1) is a concave surface; The second lens (L2) is a convex-convex lens; The third lens (L3) is a meniscus lens; The image side surface of the fourth lens (L4) is a convex surface; The fifth lens (L5) is a convex-convex lens; The sixth lens (L6) is a meniscus 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: -1.58≤F1 / F≤-1.40; The effective focal length F3 of the third lens (L3) and the effective focal length F of the fixed-focus lens satisfy the following relationship: -7.36≤F3 / F≤-5.

14.

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

3. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length F2 of the second lens (L2) and the effective focal length F of the fixed-focus lens satisfy the following relationship: 2.34≤F2 / F≤3.

14.

4. The fixed-focus lens according to claim 1 or 2, characterized in that: The effective focal length F4 of the fourth lens (L4) and the effective focal length F of the fixed-focus lens satisfy the following relationship: 2.81≤F4 / F≤3.

13.

5. The fixed-focus lens according to claim 1 or 2, characterized in that: The fixed-focus lens satisfies one of the following conditional expressions: -2.43mm -1 ≤R21 / R22 / F≤-0.18mm -1 -4.77≤(R31+R32) / F≤-3.88; Wherein, R21 is the curvature radius of the object side surface of the second lens (L2), R22 is the curvature radius of the image side surface of the second lens (L2), F is the effective focal length of the fixed-focus lens, R31 is the curvature radius of the object side surface of the third lens (L3), and R32 is the curvature radius of the image side surface of the third lens (L3).

6. The fixed-focus lens according to claim 1 or 2, characterized in that: The fixed-focus lens satisfies one of the following conditional expressions: -2.42≤F6 / F≤-1.66 1.20≤F5 / F≤1.36; Among them, F6 is the effective focal length of the sixth lens (L6), F is the effective focal length of the fixed-focus lens, and F5 is the effective focal length of the fifth lens (L5).

7. The fixed-focus lens according to claim 1 or 2, characterized in that: The Abbe number vd5 of the fifth lens (L5), the Abbe number vd6 of the sixth lens (L6) and the effective focal length F of the fixed-focus lens satisfy the following relationship: 8.88 mm -1 ≤(V5-V6) / F≤9.19mm -1 .

8. The fixed-focus lens according to claim 1 or 2, characterized in that: The fixed-focus lens satisfies one of the following conditional expressions: 5.39≤TTL / F≤5.83 0.30≤BFL / TTL≤0.33; Wherein, TLL is the total optical length of the fixed-focus lens, F is the effective focal length of the fixed-focus lens, and BFL is the back focal length of the fixed-focus lens.

9. The fixed-focus lens according to claim 1 or 2, characterized in that: The fixed-focus lens satisfies one of the following conditional expressions: 1.86≤(F2+F3) / F1≤2.70 -1.23≤F123 / F4≤-0.91; Wherein, F2 is the effective focal length of the second lens (L2), F3 is the effective focal length of the third lens (L3), F1 is the effective focal length of the first lens (L1), F123 is the combined focal length F123 of the first lens (L1), the second lens (L2) and the third lens (L3), and F is the effective focal length of the fixed-focus lens.

10. The fixed-focus lens according to claim 1 or 2, characterized in that: The fixed-focus lens satisfies one of the following conditional expressions: 3.15≤TTL / H≤3.36 0.56≤F / H≤0.59; Wherein, TLL is the total optical length of the fixed-focus lens, H is the full image height of the fixed-focus lens, and F is the effective focal length of the fixed-focus lens.

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