A fixed-focus lens

Abstract

An embodiment of the present invention provides a fixed-focus lens, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in sequence along the optical axis from the object side to the image side; the first lens, the second lens, the fifth lens, the seventh lens, and the eighth lens all have negative optical powers, and the third lens, the fourth lens, and the sixth lens all have positive optical powers. An embodiment of the present invention provides a fixed-focus lens to implement a 4K high-definition ultra-wide-angle optical lens with a large target surface, a large aperture, and an infrared confocal function. This lens supports a maximum target surface of 1 / 1.8 inch at a relatively low cost, the aperture number satisfies 1.4 < F < 1.8, the field of view angle satisfies the range of 120° to 170°, has infrared confocal, and meets the imaging requirements when used in an environment of -40°C to 80°C.

Description

Technical Field

[0001] The present invention relates to the technology of optical lenses, and particularly to a fixed-focus lens. Background Art

[0002] With the rapid development of technology, people have a higher-level understanding of security, and surveillance lenses have emerged accordingly. With the increasing development of security surveillance systems, the requirements for security lenses are getting higher and higher, mainly reflected in higher image quality, larger field of view, larger aperture, and larger target surface. Currently, existing large-aperture lenses often have a relatively small field of view angle, generally less than 120°, the target surface is generally 1 / 2.7 inches and there is no infrared confocal function. In the field of security surveillance, a larger field of view angle means a wider surveillance range, and a larger target surface means better detail representation. Summary of the Invention

[0003] Embodiments of the present invention provide a fixed-focus lens to achieve a 4K high-definition ultra-wide-angle optical lens with a large target surface, a large aperture, and an infrared confocal function.

[0004] In a first aspect, 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, and an eighth lens arranged in sequence along the optical axis from the object side to the image side direction;

[0005] The first lens, the second lens, the fifth lens, the seventh lens, and the eighth lens all have negative optical power, and the third lens, the fourth lens, and the sixth lens all have positive optical power.

[0006] Optionally, the first lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses;

[0007] The second lens, the third lens, the seventh lens, and the eighth lens are all plastic aspherical lenses.

[0008] Optionally, the fourth lens, the fifth lens, and the sixth lens form a cemented lens group.

[0009] Optionally, it further includes a diaphragm, and the diaphragm is located on the side of the fourth lens away from the image side.

[0010] Optionally, the optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the optical power of the fifth lens is φ5, the optical power of the sixth lens is φ6, the optical power of the seventh lens is φ7, the optical power of the eighth lens is φ8, and the optical power of the fixed-focus lens is φ, satisfying:

[0011] 0.32 ≤ |φ1 / φ| ≤ 1.20;

[0012] 0.01 ≤ |φ2 / φ| ≤ 0.35;

[0013] 0.02 ≤ |φ3 / φ| ≤ 0.67;

[0014] 0.05 ≤ |φ4 / φ| ≤ 0.78;

[0015] 0.00 ≤ |φ5 / φ| ≤ 0.65;

[0016] 0.10 ≤ |φ6 / φ| ≤ 0.70;

[0017] 0.08 ≤ |φ7 / φ| ≤ 0.85;

[0018] 0.06 ≤ |φ8 / φ| ≤ 0.62.

[0019] Optionally, the refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, the refractive index of the fourth lens is n4, the refractive index of the fifth lens is n5, the refractive index of the sixth lens is n6, the refractive index of the seventh lens is n7, and the refractive index of the eighth lens is n8, satisfying:

[0020] 1.43 ≤ n1 ≤ 1.80;

[0021] 1.45 ≤ n2 ≤ 1.78;

[0022] 1.50 ≤ n3 ≤ 1.90;

[0023] 1.52 ≤ n4 ≤ 1.88;

[0024] 1.55 ≤ n5 ≤ 1.92;

[0025] 1.42 ≤ n6 ≤ 1.75;

[0026] 1.45 ≤ n7 ≤ 1.86;

[0027] 1.43 ≤ n8 ≤ 2.01.

[0028] Optionally, the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, the Abbe number of the third lens is v3, the Abbe number of the fourth lens is v4, the Abbe number of the fifth lens is v5, the Abbe number of the sixth lens is v6, the Abbe number of the seventh lens is v7, and the Abbe number of the eighth lens is v8, satisfying:

[0029] 40.0 ≤ v1 ≤ 85.0;

[0030] 20.0 ≤ v2 ≤ 75.0;

[0031] 20.0 ≤ v3 ≤ 55.0;

[0032] 44.0 ≤ v4 ≤ 80.0;

[0033] 23.0 ≤ v5 ≤ 62.0;

[0034] 45.0 ≤ v6 ≤ 87.0;

[0035] 20.0 ≤ v7 ≤ 84.0;

[0036] 20.0 ≤ v8 ≤ 90.0.

[0037] Optionally, the aperture of the fixed-focus lens is F, and the entrance pupil diameter of the fixed-focus lens is EP, satisfying:

[0038] 1.20 ≤ f / EP ≤ 2.20.

[0039] Optionally, the image plane diameter of the fixed-focus lens is IC, and the back focal length of the fixed-focus lens is BFL, satisfying:

[0040] 1.44 ≤ IC / BFL ≤ 2.56.

[0041] Optionally, the field of view angle of the fixed-focus lens is FOV, and the total optical length of the fixed-focus lens is TTL, satisfying:

[0042] 3 ≤ FOV / TTL ≤ 10.

[0043] The fixed-focus lens provided by the embodiment of the present invention adopts 8 lenses. Among them, the first lens, the second lens, the fifth lens, the seventh lens and the eighth lens all have negative optical powers, and the third lens, the fourth lens and the sixth lens all have positive optical powers. The embodiment of the present invention provides a fixed-focus lens to realize a 4K high-definition ultra-wide-angle optical lens with a large target surface, a large aperture and an infrared confocal function. This lens supports a maximum target surface of 1 / 1.8 inches at a relatively low cost, the aperture number satisfies 1.4 < F < 1.8, the field of view angle satisfies the range of 120° to 170°, has infrared confocal, and meets the imaging requirements when used in an environment of -40°C to 80°C. Description of the Drawings

[0044] Figure 1 It is a schematic structural diagram of a fixed-focus lens provided by Embodiment 1 of the present invention;

[0045] Figure 2 It is a spherical aberration curve graph of the fixed-focus lens in Embodiment 1;

[0046] Figures 3 - 8The light fan diagrams of the fixed-focus lens in Embodiment 1 at image planes of 0 mm, 1.9677 mm, 2.7828 mm, 3.4082 mm, 3.9355 mm, and 4.4 mm respectively;

[0047] Figures 9 - 14 The spot diagrams of the fixed-focus lens in Embodiment 1 at image planes of 0 mm, 1.968 mm, 2.783 mm, 3.408 mm, 3.935 mm, and 4.4 mm respectively;

[0048] Figure 15 The field curvature diagram of the fixed-focus lens in this Embodiment 1;

[0049] Figure 16 The distortion diagram of the fixed-focus lens in this Embodiment 1;

[0050] Figure 17 The structural schematic diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0051] Figure 18 The spherical aberration curve diagram of the fixed-focus lens in Embodiment 2;

[0052] Figures 19 - 24 The light fan diagrams of the fixed-focus lens in Embodiment 2 at image planes of 0 mm, 1.9677 mm, 2.7828 mm, 3.4082 mm, 3.9355 mm, and 4.4 mm respectively;

[0053] Figures 25 - 30 The spot diagrams of the fixed-focus lens in Embodiment 2 at image planes of 0 mm, 1.968 mm, 2.783 mm, 3.408 mm, 3.935 mm, and 4.4 mm respectively;

[0054] Figure 31 The field curvature diagram of the fixed-focus lens in this Embodiment 2;

[0055] Figure 32 The distortion diagram of the fixed-focus lens in this Embodiment 2;

[0056] Figure 33 The structural schematic diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0057] Figure 34 The spherical aberration curve diagram of the fixed-focus lens in Embodiment 3;

[0058] Figures 35 - 40 The light fan diagrams of the fixed-focus lens in Embodiment 3 at image planes of 0 mm, 1.9677 mm, 2.7828 mm, 3.4082 mm, 3.9355 mm, and 4.4 mm respectively;

[0059] Figures 41 - 46They are respectively the spot diagrams of the fixed-focus lens in Embodiment 3 at image plane positions of 0 mm, 1.968 mm, 2.783 mm, 3.408 mm, 3.935 mm, and 4.4 mm;

[0060] Figure 47 This is the field curvature diagram of the fixed-focus lens in Embodiment 3;

[0061] Figure 48 This is the distortion diagram of the fixed-focus lens in Embodiment 3. Detailed implementation manners

[0062] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the convenience of description, only the parts related to the present invention rather than all the structures are shown in the drawings.

[0063] Embodiment 1

[0064] Figure 1 This is a schematic structural diagram of a fixed-focus lens provided by Embodiment 1 of the present invention. Referring to Figure 1 , the fixed-focus lens includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, and an eighth lens 8 arranged in sequence along the optical axis from the object side to the image side. The first lens 1, the second lens 2, the fifth lens 5, the seventh lens 7, and the eighth lens 8 all have negative optical powers, and the third lens 3, the fourth lens 4, and the sixth lens 6 all have positive optical powers.

[0065] The fixed-focus lens provided by the embodiment of the present invention uses 8 lenses. Among them, the first lens 1, the second lens 2, the fifth lens 5, the seventh lens 7, and the eighth lens 8 all have negative optical powers, and the third lens 3, the fourth lens 4, and the sixth lens 6 all have positive optical powers. The embodiment of the present invention provides a fixed-focus lens to realize a 4K high-definition ultra-wide-angle optical lens with a large target surface, a large aperture, and an infrared confocal function. This lens supports a maximum target surface of 1 / 1.8 inches at a relatively low cost, the aperture number satisfies 1.4 < F < 1.8, the field of view angle satisfies the range of 120° to 170°, has infrared confocal, and meets the imaging requirements when used in an environment of -40°C to 80°C.

[0066] Optionally, the first lens 1, the fourth lens 4, the fifth lens 5, and the sixth lens 6 are all glass spherical lenses. A glass spherical lens refers to a spherical lens made of glass material. A glass spherical lens has a small deformation at different temperatures. The second lens 2, the third lens 3, the seventh lens 7, and the eighth lens 8 are all plastic aspherical lenses. A plastic aspherical lens refers to an aspherical lens made of plastic material. Compared with a glass spherical lens, a plastic aspherical lens has a lower cost and a smaller weight. In the embodiment of the present invention, the fixed-focus lens adopts a hybrid optical structure formed by 4 glass spherical lenses and 4 plastic aspherical lenses.

[0067] Optionally, the fourth lens 4, the fifth lens 5, and the sixth lens 6 form a cemented lens group. That is to say, the surface of the fourth lens 4 facing the image side is in contact with the surface of the fifth lens 5 facing the object side, and the surface of the fifth lens 5 facing the image side is in contact with the surface of the sixth lens 6 facing the object side.

[0068] Optionally, the fixed-focus lens further includes a diaphragm 9, and the diaphragm 9 is located on the side of the fourth lens 4 away from the image side. When the fourth lens 4, the fifth lens 5, and the sixth lens 6 form a cemented lens group, the diaphragm 9 is located on the side of the fourth lens 4 away from the image side, that is, the diaphragm 9 is on the optical path before the fourth lens 4.

[0069] Exemplarily, the diaphragm 9 is located between the second lens 2 and the third lens 3.

[0070] Optionally, the optical power of the first lens 1 is φ1, the optical power of the second lens 2 is φ2, the optical power of the third lens 3 is φ3, the optical power of the fourth lens 4 is φ4, the optical power of the fifth lens 5 is φ5, the optical power of the sixth lens 6 is φ6, the optical power of the seventh lens 7 is φ7, the optical power of the eighth lens 8 is φ8, the optical power of the fixed-focus lens is φ, and the optical powers of the first lens 1 to the eighth lens 8 and the fixed-focus lens satisfy: 0.32 ≤ |φ1 / φ| ≤ 1.20, 0.01 ≤ |φ2 / φ| ≤ 0.35, 0.02 ≤ |φ3 / φ| ≤ 0.67, 0.05 ≤ |φ4 / φ| ≤ 0.78, 0.00 ≤ |φ5 / φ| ≤ 0.65, 0.10 ≤ |φ6 / φ| ≤ 0.70, 0.08 ≤ |φ7 / φ| ≤ 0.85, 0.06 ≤ |φ8 / φ| ≤ 0.62.

[0071] Optionally, the refractive index of the first lens 1 is n1, the refractive index of the second lens 2 is n2, the refractive index of the third lens 3 is n3, the refractive index of the fourth lens 4 is n4, the refractive index of the fifth lens 5 is n5, the refractive index of the sixth lens 6 is n6, the refractive index of the seventh lens 7 is n7, and the refractive index of the eighth lens 8 is n8. The refractive indices of the first lens 1 to the eighth lens 8 satisfy: 1.43 ≤ n1 ≤ 1.80;, 1.45 ≤ n2 ≤ 1.78, 1.50 ≤ n3 ≤ 1.90, 1.52 ≤ n4 ≤ 1.88, 1.55 ≤ n5 ≤ 1.92, 1.42 ≤ n6 ≤ 1.75, 1.45 ≤ n7 ≤ 1.86, 1.43 ≤ n8 ≤ 2.01.

[0072] Optionally, the Abbe number of the first lens 1 is v1, the Abbe number of the second lens 2 is v2, the Abbe number of the third lens 3 is v3, the Abbe number of the fourth lens 4 is v4, the Abbe number of the fifth lens 5 is v5, the Abbe number of the sixth lens 6 is v6, the Abbe number of the seventh lens 7 is v7, and the Abbe number of the eighth lens 8 is v8. The Abbe numbers of the first lens 1 to the eighth lens 8 satisfy: 40.0 ≤ v1 ≤ 85.0, 20.0 ≤ v2 ≤ 75.0, 20.0 ≤ v3 ≤ 55.0, 44.0 ≤ v4 ≤ 80.0, 23.0 ≤ v5 ≤ 62.0, 45.0 ≤ v6 ≤ 87.0, 20.0 ≤ v7 ≤ 84.0, 20.0 ≤ v8 ≤ 90.0.

[0073] Optionally, the aperture of the fixed-focus lens is F, and the entrance pupil diameter of the fixed-focus lens is EP, satisfying: 1.20 ≤ f / EP ≤ 2.20.

[0074] Optionally, the image plane diameter of the fixed-focus lens is IC, and the back focal length of the fixed-focus lens is BFL, satisfying: 1.44 ≤ IC / BFL ≤ 2.56.

[0075] Optionally, the field of view angle of the fixed-focus lens is FOV, and the total optical length of the fixed-focus lens is TTL, satisfying: 3 ≤ FOV / TTL ≤ 10.

[0076] Table 1 shows a set of design values of the fixed-focus lens in the first embodiment

[0077] Surface number Surface type Radius of curvature (mm) Thickness (mm) Refractive index Dispersion coefficient 1 Spherical surface 40.55 0.77 1.62 60.4 2 Spherical surface 3.70 2.65 3 Aspherical surface -4.76 2.87 1.64 23.9 4 Aspherical surface -6.88 0.59 STOP PL Infinity -0.38 6 Aspherical surface 9.84 1.86 1.66 20.4 7 Aspherical surface 323.25 0.10 8 Spherical surface 6.83 2.75 1.64 60.2 9 Spherical surface -4.14 0.77 1.69 31.2 10 Spherical surface 4.57 3.58 1.59 68.6 11 Spherical surface -5.31 0.10 12 Aspherical surface -9.31 0.80 1.64 23.9 13 Aspherical surface 102.55 0.13 14 Aspherical surface 6.59 1.31 1.64 23.9 15 Aspherical surface 13.40 3.83

[0078] Table 1 shows a set of design values of the fixed-focus lens in the first embodiment. The specific numerical values can be adjusted according to product requirements and do not limit the embodiments of the present invention. The fixed-focus lens shown in Table 1 can be Figure 1As shown. A lens generally includes two surfaces, and each surface is a refractive surface. The surface numbers in Table 1 are numbered according to the surfaces of each lens. Among them, the surface number "1" represents the front surface of the first lens 1, the surface number "2" represents the rear surface of the first lens 1, and so on, which will not be elaborated here. It should be noted that "STOP" in the "Surface Number" column represents the plane where the diaphragm 9 is located. "PL" in the "Surface Type" column represents a plane. The radius of curvature represents the degree of curvature of the lens surface. A positive value of the radius of curvature indicates that the center of curvature is on the image side near the surface, and a negative value of the radius of curvature represents that the center of curvature is on the side away from the image side of the surface. The value in the "Thickness" column represents the axial distance from the current surface to the next surface. The "Refractive Index" column represents the refractive index of the medium between the current surface and the next surface. The space in the "Refractive Index" column is the refractive index of air, and the refractive index of air is 1. The dispersion coefficient represents the dispersion characteristics of the material between the current surface and the next surface to light, and the space represents that the current position is air.

[0079] Optionally, the surface of the aspherical lens satisfies the formula:

[0080]

[0081] Where z is the axial sagittal height of the surface in the Z direction, r is the height of the aspherical surface, that is, when the aspherical surface is at a position with a height of r along the optical axis direction, z is the distance sagittal height from the vertex of the aspherical surface; c is the curvature of the fitted spherical surface, and numerically c is the reciprocal of the radius of curvature, c = 1 / R, and R represents the paraxial radius of curvature of the mirror surface; k is the conic coefficient, and A, B, C, D, E, F, G are aspherical coefficients. Specifically, A, B, C, D, E, F, G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th orders of the aspherical polynomial respectively.

[0082] Table 2 shows a set of design values of the aspherical coefficients of the lenses in the fixed-focus lens in the first embodiment

[0083] Surface number A B C D E F G 3 1.22E-03 1.84E-04 6.24E-06 -2.71E-06 4.50E-07 -3.27E-08 1.10E-09 4 4.43E-03 -4.53E-04 1.93E-05 7.13E-06 -1.21E-06 6.01E-08 -1.06E-10 6 4.36E-03 -4.69E-04 4.19E-05 1.24E-06 -4.22E-07 1.96E-08 2.16E-10 7 1.29E-03 2.39E-04 -1.35E-05 6.72E-07 1.90E-07 -1.06E-08 7.15E-10 12 -2.84E-03 -2.06E-04 -2.77E-06 -3.15E-08 1.28E-08 3.62E-09 -2.66E-10 13 -1.50E-03 -7.04E-05 2.03E-07 3.81E-07 2.83E-08 -2.08E-10 -9.43E-11 14 -5.40E-03 -3.27E-06 8.54E-06 1.68E-07 -2.80E-09 -1.53E-10 -1.85E-11 15 -5.86E-03 8.74E-05 3.97E-06 -2.64E-07 6.50E-10 4.56E-10 -1.89E-11

[0084] Table 2 shows a set of design values of the aspherical coefficients of the lenses in the fixed-focus lens in the first embodiment, and the specific numerical values can be adjusted according to product requirements, which is not a limitation to the embodiments of the present invention. The fixed-focus lens shown in Table 2 can be Figure 1 As shown. The meaning of the "Surface Number" column in Table 2 is the same as that of the "Surface Number" in Table 1. For example, the surface number "1" also represents the front surface of the first lens 1. "E" in each embodiment of the present invention represents the exponent with base 10. For example, the numerical value of 1.22E-03 is 0.00122.

[0085] Figures 3 - 8The light fan diagrams of the fixed-focus lens in Example 1 at image planes of 0 mm, 1.9677 mm, 2.7828 mm, 3.4082 mm, 3.9355 mm, and 4.4 mm respectively, for reference Figures 3 - 8 , and the selected wavelengths are 0.435 μm, 0.486 μm, 0.546 μm, 0.588 μm, 0.656 μm, and 0.850 μm respectively. The maximum scaling ratio is ±30 μm. The smaller the scaling ratio, the smoother the light, indicating better correction of lens aberrations.

[0086] Figures 9 - 14 The spot diagrams of the fixed-focus lens in Example 1 at image planes of 0 mm, 1.968 mm, 2.783 mm, 3.408 mm, 3.935 mm, and 4.4 mm respectively, for reference Figures 9 - 14 , with the unit being μm. The scaling bar (i.e., the scaling ratio) is 40. Both the RMS radius and the GEO radius represent the aberration strength, and the smaller the values of the RMS radius and the GEO radius, the better. The Airy disk radius is 1.109 μm.

[0087] Figure 15 This is the field curvature diagram of the fixed-focus lens in Example 1 Figure 16 This is the distortion diagram of the fixed-focus lens in Example 1, for reference Figure 15 and Figure 16 , and the maximum field of view is 72.51°. The adopted distortion is F-Tan(Theta) distortion.

[0088] Example 2

[0089] Table 3 A set of design values of the fixed-focus lens in Example 2

[0090]

[0091]

[0092] Table 4 A set of design values of the aspherical coefficients of the lenses in the fixed-focus lens in Example 2

[0093] Surface number A B C D E F G 3 1.90E-03 1.51E-04 4.04E-06 -2.53E-06 4.47E-07 -2.91E-08 7.09E-10 4 4.82E-03 -4.60E-04 1.62E-05 7.55E-06 -1.16E-06 4.88E-08 5.46E-10 6 4.09E-03 -4.65E-04 4.39E-05 1.45E-06 -4.09E-07 1.97E-08 3.43E-10 7 7.89E-04 2.60E-04 -1.54E-05 4.70E-07 2.52E-07 -1.72E-09 -8.23E-11 12 -2.00E-03 -1.38E-04 -1.05E-06 1.09E-07 4.87E-09 6.56E-10 -1.78E-10 13 -1.11E-03 -2.71E-05 2.41E-06 3.65E-07 1.84E-08 -2.20E-10 -7.28E-11 14 -4.53E-03 -3.91E-05 5.60E-06 1.58E-07 5.14E-09 1.16E-10 1.41E-12 15 -5.37E-03 7.21E-05 2.50E-06 -2.86E-07 5.35E-10 8.11E-10 -3.41E-11

[0094] The fixed-focus lens shown in Table 3 and Table 4 can be Figure 17 as shown in

[0095] Figures 19 - 24 The light fan diagrams of the fixed-focus lens in Example 2 at image planes of 0 mm, 1.9677 mm, 2.7828 mm, 3.4082 mm, 3.9355 mm, and 4.4 mm respectively, for reference Figures 19 - 24, the selected wavelengths are 0.435μm, 0.486μm, 0.546μm, 0.588μm, 0.656μm and 0.850μm respectively. The maximum scaling ratio is ±30μm. The smaller the scaling ratio, the smoother the light, indicating better correction of lens aberration.

[0096] Figures 25 - 30 They are respectively the spot diagrams of the fixed-focus lens in Example 2 at the image planes of 0mm, 1.968mm, 2.783mm, 3.408mm, 3.935mm and 4.4mm, refer to Figures 25 - 30 , and the unit is μm. The scaling bar (i.e., the scaling ratio) is 40. Both the RMS radius and the GEO radius represent the aberration strength, and the smaller the values of the RMS radius and the GEO radius, the better. The Airy disk radius is 1.106μm.

[0097] Figure 31 This is the field curvature diagram of the fixed-focus lens in Example 2. Figure 32 This is the distortion diagram of the fixed-focus lens in Example 2, refer to Figure 31 and Figure 32 , and the maximum field of view is 72.049°. The adopted distortion is F-Tan(Theta) distortion.

[0098] Example 3

[0099] Table 5 shows a set of design values of the fixed-focus lens in Example 3

[0100] Surface number Surface type Radius of curvature (mm) Thickness (mm) Refractive index Dispersion coefficient 1 Spherical surface 36.25 0.79 1.69 70.0 2 Spherical surface 3.94 2.47 3 Aspherical surface -4.75 2.36 1.68 41.0 4 Aspherical surface -6.44 0.53 STO PL Infinity -0.38 6 Aspherical surface 9.80 2.07 1.68 31.3 7 Aspherical surface 258.21 1.26 1.64 60.2 8 Spherical surface 7.60 2.61 1.67 29.4 9 Spherical surface -5.35 0.79 10 Spherical surface 6.70 2.87 1.59 68.6 11 Spherical surface -5.85 0.11 12 Aspherical surface -8.35 0.84 1.56 59.4 13 Aspherical surface 53.18 0.11 14 Aspherical surface 6.53 0.99 2.0 80.2 15 Aspherical surface 9.80 0.79

[0101] Table 6 shows a set of design values of the aspherical coefficients of the lenses in the fixed-focus lens in Example 3

[0102] Surface number A B C D E F G 3 1.26E-03 2.44E-04 1.38E-06 -2.89E-06 4.49E-07 -2.72E-08 6.85E-10 4 4.57E-03 -4.10E-04 1.80E-05 7.29E-06 -1.19E-06 4.79E-08 8.45E-10 6 4.04E-03 -4.94E-04 4.24E-05 1.38E-06 -4.25E-07 1.70E-08 2.93E-10 7 7.17E-04 2.50E-04 -1.82E-05 1.44E-07 2.34E-07 -7.78E-10 -7.17E-10 12 -1.52E-03 -1.62E-04 -5.91E-06 5.61E-08 1.23E-08 6.95E-10 -1.26E-10 13 -1.58E-03 -5.22E-05 -1.55E-06 2.85E-08 1.95E-09 -3.90E-10 -6.23E-12 14 -4.88E-03 -4.78E-05 5.93E-06 2.04E-07 9.38E-09 2.87E-10 -5.63E-11 15 -5.23E-03 7.32E-05 4.40E-06 -1.05E-07 4.49E-09 5.63E-10 -1.62E-11

[0103] The fixed-focus lens shown in Table 5 and Table 6 can be Figure 33 as shown in

[0104] Figures 35 - 40 They are respectively the ray fan diagrams of the fixed-focus lens in Example 3 at the image planes of 0mm, 1.9677mm, 2.7828mm, 3.4082mm, 3.9355mm and 4.4mm, refer to Figures 35 - 40 , the selected wavelengths are 0.435μm, 0.486μm, 0.546μm, 0.588μm, 0.656μm and 0.850μm respectively. The maximum scaling ratio is ±30μm. The smaller the scaling ratio, the smoother the light, indicating better correction of lens aberration.

[0105] Figures 41 - 46They are respectively the spot diagrams of the fixed-focus lens in Embodiment 3 at the image planes of 0 mm, 1.968 mm, 2.783 mm, 3.408 mm, 3.935 mm and 4.4 mm, referring to Figures 41 - 46 , and the unit is μm. The scale bar (i.e., the scaling ratio) is 40. Both the RMS radius and the GEO radius represent the aberration strength, and the smaller the values of the RMS radius and the GEO radius, the better. The Airy disk radius is 1.028 μm.

[0106] Figure 47 This is the field curvature diagram of the fixed-focus lens in Embodiment 3. Figure 48 This is the distortion diagram of the fixed-focus lens in Embodiment 3, referring to Figure 47 and Figure 48 , and the maximum field of view is 69.146°. The adopted distortion is F-Tan(Theta) distortion.

[0107] Note that the above is only the preferred embodiment of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, 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, It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged in sequence from the object side to the image side along the optical axis; The first lens, the second lens, the fifth lens, the seventh lens, and the eighth lens all have negative optical powers, and the third lens, the fourth lens, and the sixth lens all have positive optical powers; The first lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses; The second lens, the third lens, the seventh lens, and the eighth lens are all plastic aspherical lenses; The fourth lens, the fifth lens, and the sixth lens form a cemented lens group; The optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the optical power of the fifth lens is φ5, the optical power of the sixth lens is φ6, the optical power of the seventh lens is φ7, the optical power of the eighth lens is φ8, and the optical power of the fixed-focus lens is φ, satisfying: 0.32 ≤ |φ1 / φ| ≤ 1.20; 0.01 ≤ |φ2 / φ| ≤ 0.35; 0.02 ≤ |φ3 / φ| ≤ 0.67; 0.05 ≤ |φ4 / φ| ≤ 0.78; 0.00 ≤ |φ5 / φ| ≤ 0.65; 0.10 ≤ |φ6 / φ| ≤ 0.70; 0.08 ≤ |φ + 7 / φ| ≤ 0.85; 0.06 ≤ |φ8 / φ| ≤ 0.

62.

2. The fixed-focus lens according to claim 1, wherein, It further includes a diaphragm, and the diaphragm is located on the side of the fourth lens away from the image side.

3. The fixed-focus lens according to claim 1, wherein The refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, the refractive index of the fourth lens is n4, the refractive index of the fifth lens is n5, the refractive index of the sixth lens is n6, the refractive index of the seventh lens is n7, the refractive index of the eighth lens is n8, satisfying: 1.43≤n1≤1.80； 1.45≤n2≤1.78； 1.50≤n3≤1.90； 1.52≤n4≤1.88； 1.55≤n5≤1.92； 1.42≤n6≤1.75； 1.45≤n7≤1.86； 1.43≤n8≤2.01。 4. The fixed-focus lens according to claim 1, characterized in that, The Abbe number of the first lens is v1, the Abbe number of the second lens is v2, the Abbe number of the third lens is v3, the Abbe number of the fourth lens is v4, the Abbe number of the fifth lens is v5, the Abbe number of the sixth lens is v6, the Abbe number of the seventh lens is v7, the Abbe number of the eighth lens is v8, satisfying: 40.0≤v1≤85.0； 20.0≤v2≤75.0； 20.0≤v3≤55.0； 44.0≤v4≤80.0； 23.0≤v5≤62.0； 45.0≤v6≤87.0； 20.0≤v7≤84.0； 20.0≤v8≤90.0。 5. The fixed-focus lens according to claim 1, wherein, The aperture of the fixed-focus lens is F, and the entrance pupil diameter of the fixed-focus lens is EP, satisfying: 1.20 ≤ f / EP ≤ 2.

20.

6. The fixed-focus lens according to claim 1, wherein, The image plane diameter of the fixed-focus lens is IC, and the optical back focal length of the fixed-focus lens is BFL, satisfying: 1.44 ≤ IC / BFL ≤ 2.

56.

7. The fixed-focus lens according to claim 1, wherein, The field of view angle of the fixed-focus lens is FOV, and the total optical length of the fixed-focus lens is TTL, satisfying: 3 ≤ FOV / TTL ≤ 10.

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