Fixed-focus lens

Abstract

The present invention relates to a fixed-focus lens, which comprises, arranged in sequence from the object side to the image side along the optical axis: a first lens (L1) with a negative optical power, a second lens (L2) with a positive optical power, a third lens (L3) with a positive optical power, a fourth lens (L4) with a negative optical power, and a fifth lens (L5) with a positive optical power. The fixed-focus lens of the present invention has better imaging performance, and has a simple and reasonable structure, low cost, and can achieve visible-infrared confocal and athermalization.

Description

Technical Field

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

[0002] In the prior art, the chief ray angle (CRA) of a small-sized fixed-focus lens is relatively large, and the design with all-glass lenses is more common. This not only goes against miniaturization but also leads to an increase in cost. Plastic lenses can reduce the manufacturing cost to a certain extent. At the same time, plastic aspherical lenses also improve the resolution of the lens, thereby enhancing the competitiveness of the lens. However, plastic materials themselves have the side effect of a large coefficient of thermal expansion. Therefore, lenses using plastic lenses will also have defects such as defocus at high and low temperatures. Summary of the Invention

[0003] The purpose of the present invention is to provide a fixed-focus lens with better imaging performance.

[0004] To achieve the above-mentioned invention purpose, the present invention provides a fixed-focus lens, including, arranged in sequence from the object side to the image side along 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 negative optical power, and a fifth lens with positive optical power.

[0005] According to one aspect of the present invention, it further includes a diaphragm located between the first lens and the second lens or between the second lens and the third lens.

[0006] According to one aspect of the present invention, the first lens is a convex-concave lens, the second lens is a concave-convex lens, the third lens is a biconvex lens, the fourth lens is a biconcave lens, and the fifth lens is a biconvex lens.

[0007] According to one aspect of the present invention, the first lens, the fourth lens, and the fifth lens are plastic aspherical lenses, the third lens is a glass lens, and the second lens is a plastic aspherical lens or a glass lens.

[0008] According to one aspect of the present invention, the following relationships are respectively satisfied between the sagittal height SAG11 of the maximum optical effective diameter of the object side surface of the first lens and its radius of curvature R1, and the sagittal height SAG12 of the maximum optical effective diameter of the image side surface of the first lens and its radius of curvature R2:

[0009] 1.0 ≤ R1 / SAG11 ≤ 1.5;

[0010] 0.5 ≤ R2 / SAG12 ≤ 1.0.

[0011] According to one aspect of the present invention, the radius of curvature R21 of the object side surface of the second lens and the radius of curvature R12 of the image side surface of the first lens satisfy the following relational expression:

[0012] -2.5 ≤ R21 / R12 ≤ -1.5.

[0013] According to one aspect of the present invention, the chief ray angle CRA of the maximum field of view of the fixed-focus lens satisfies the following condition: CRA ≤ 12°.

[0014] According to one aspect of the present invention, the optical power φ3 of the third lens and the optical power φII of the lens group located on the image side of the diaphragm satisfy the following relational expression:

[0015] 0.7 ≤ φ3 / φII ≤ 1.3.

[0016] According to one aspect of the present invention, the distance M1 between the center on the object side surface of the first lens and the diaphragm, the distance M2 between the center on the image side surface of the fifth lens and the diaphragm, and the total optical length TTL of the fixed-focus lens respectively satisfy the following relational expressions:

[0017] 0.15 ≤ M1 / TTL ≤ 0.32;

[0018] 0.33 ≤ M2 / TTL ≤ 0.51.

[0019] According to one aspect of the present invention, the focal length f1 of the first lens, the focal length f2 of the second lens, the focal length f3 of the third lens, the focal length f4 of the fourth lens, the focal length f5 of the fifth lens and the effective focal length f of the fixed-focus lens respectively satisfy the following relational expressions:

[0020] -4.2 ≤ f1 / f ≤ -2.5;

[0021] 2 ≤ f2 / f ≤ 12;

[0022] 1 ≤ f3 / f ≤ 1.5;

[0023] -0.9 ≤ f4 / f ≤ -0.5;

[0024] 0.5 ≤ f5 / f ≤ 0.9.

[0025] According to one aspect of the present invention, the lens group located on the image side of the diaphragm includes at least one glass lens made of a low-dispersion coefficient material with an Abbe number Vd > 75.

[0026] According to one aspect of the present invention, the focal length f4 of the fourth lens and the focal length f5 of the fifth lens satisfy the following relational expression:

[0027] -1.1 ≤ f4 / f5 ≤ -0.6.

[0028] According to one aspect of the present invention, the total optical length TTL and the aperture FNO of the fixed-focus lens satisfy the following conditions: TTL ≤ 22.5 mm, FNO ≤ 1.6.

[0029] According to one aspect of the present invention, the total optical length TTL and the effective focal length f of the fixed-focus lens satisfy the following relational formula:

[0030] TTL / f ≤ 3.0.

[0031] According to the solution of the present invention, by using the combination of the glass-plastic hybrid material, the concavity-convexity, and the positive and negative optical powers of each lens in the fixed-focus lens, the imaging performance of the fixed-focus lens is better, and the structure is simple and reasonable, the cost is relatively low, and visible infrared confocal and athermalization can be achieved. The present invention optimizes aberrations such as astigmatism, field curvature, and coma of the lens by reasonably setting the position of the aperture.

[0032] According to one solution of the present invention, the sagittal height SAG11 of the maximum optical effective diameter on the object side of the first lens and its radius of curvature R1, and the sagittal height SAG12 of the maximum optical effective diameter on the image side of the first lens and its radius of curvature R2 respectively satisfy the following relational formulas: 1.0 ≤ R1 / SAG11 ≤ 1.5; 0.5 ≤ R2 / SAG12 ≤ 1.0. This relationship between the radius of curvature and the sagittal height can effectively control the aperture size of the first lens, thereby reducing the incident height when the chief ray enters the optical system, which is beneficial to reducing distortion and correcting aberrations in the off-axis field of view, and at the same time reducing the number of lenses.

[0033] According to one solution of the present invention, the radius of curvature R21 of the object side of the second lens and the radius of curvature R12 of the image side of the first lens satisfy the following relational formula: -2.5 ≤ R21 / R12 ≤ -1.5. This matching relationship between the radii of curvature can improve the efficiency of the lens in converging light, which is beneficial to reducing the volume of the front-end lens of the lens.

[0034] According to one solution of the present invention, the chief ray angle CRA of the maximum field of view of the fixed-focus lens satisfies the following condition: CRA ≤ 12°. Thereby reducing the reflected light and increasing the intensity of the light transmitted through the lens to the sensor for imaging, thereby improving the imaging quality.

[0035] According to one solution of the present invention, the optical power φ3 of the third lens and the optical power φII of the lens group on the image side of the aperture STO satisfy the following relational formula: 0.7 ≤ φ3 / φII ≤ 1.3. This distribution method of the optical powers can improve the light transmittance, reduce the volume of the lens, and achieve a reduction in production cost.

[0036] According to one embodiment of the present invention, the distance M1 between the center on the object side of the first lens and the aperture, the distance M2 between the center on the image side of the fifth lens and the aperture STO, and the overall optical length TTL of the fixed-focus lens respectively satisfy the following relational expressions: 0.15 ≤ M1 / TTL ≤ 0.32; 0.33 ≤ M2 / TTL ≤ 0.51. This positional relationship between the groups makes the overall lens more compact and realizes miniaturization of the volume.

[0037] According to one embodiment of the present invention, the focal length f1 of the first lens, the focal length f2 of the second lens, the focal length f3 of the third lens, the focal length f4 of the fourth lens, the focal length f5 of the fifth lens and the effective focal length f of the fixed-focus lens respectively satisfy the following relational expressions: -4.2 ≤ f1 / f ≤ -2.5; 2 ≤ f2 / f ≤ 12; 1 ≤ f3 / f ≤ 1.5; -0.9 ≤ f4 / f ≤ -0.5; 0.5 ≤ f5 / f ≤ 0.9. This reasonable distribution of positive and negative lens optical powers corrects the aberrations of the optical system and ensures clear imaging of the lens.

[0038] According to one embodiment of the present invention, the lens group on the image side of the aperture includes at least one glass lens made of a low-dispersion coefficient material with Abbe number Vd > 75. This material with a low-dispersion coefficient can correct the chromatic aberration of the lens, enabling the lens to clearly image both the visible and near-infrared spectra, and can balance the resolution at high and low temperatures.

[0039] According to one embodiment of the present invention, the focal length f4 of the fourth lens and the focal length f5 of the fifth lens satisfy the following relational expression: -1.1 ≤ f4 / f5 ≤ -0.6. This combination relationship of positive and negative optical powers can improve the image quality and further control the focus drift of the lens within a reasonable range at high and low temperatures.

[0040] According to one embodiment of the present invention, the overall optical length TTL of the fixed-focus lens and the aperture FNO satisfy the following conditions: TTL ≤ 22.5 mm, FNO ≤ 1.6. Achieving the largest possible aperture under the condition of a certain overall length enables clear imaging without focusing adjustment even in darkroom conditions such as at night.

[0041] According to one embodiment of the present invention, the overall optical length TTL of the fixed-focus lens and the effective focal length f satisfy the following relational expression: TTL / f ≤ 3.0. This proportional relationship between the overall optical length and the focal length of the lens reflects the characteristic of the lens being compact in volume. Description of the Drawings

[0042] Figure 1 Schematic structural diagram of the fixed-focus lens showing the first embodiment of the present invention;

[0043] Figure 2 Schematic RayFan diagram of the fixed-focus lens showing the first embodiment of the present invention;

[0044] Figure 3 Schematically represents the field curvature - distortion diagram of the fixed - focus lens of the first embodiment of the present invention;

[0045] Figure 4 Schematically represents the structural diagram of the fixed - focus lens of the second embodiment of the present invention;

[0046] Figure 5 Schematically represents the RayFan diagram of the fixed - focus lens of the second embodiment of the present invention;

[0047] Figure 6 Schematically represents the field curvature - distortion diagram of the fixed - focus lens of the second embodiment of the present invention;

[0048] Figure 7 Schematically represents the structural diagram of the fixed - focus lens of the third embodiment of the present invention;

[0049] Figure 8 Schematically represents the RayFan diagram of the fixed - focus lens of the third embodiment of the present invention;

[0050] Figure 9 Schematically represents the field curvature - distortion diagram of the fixed - focus lens of the third embodiment of the present invention;

[0051] Figure 10 Schematically represents the structural diagram of the fixed - focus lens of the fourth embodiment of the present invention;

[0052] Figure 11 Schematically represents the RayFan diagram of the fixed - focus lens of the fourth embodiment of the present invention;

[0053] Figure 12 Schematically represents the field curvature - distortion diagram of the fixed - focus lens of the fourth embodiment of the present invention. Detailed implementation manners

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0055] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" is based on the orientation or positional relationship shown in the relevant drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0056] The present invention will be described in detail below with reference to the drawings and specific embodiments. The embodiments cannot be enumerated one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0057] See Figure 1 , the fixed-focus lens of the present invention includes, arranged in sequence from the object side to the image side along the optical axis: a first lens L1 with a negative optical power, a second lens L2 with a positive optical power, a third lens L3 with a positive optical power, a fourth lens L4 with a negative optical power, and a fifth lens L5 with a positive optical power. Of course, it also includes a diaphragm STO, which can be located between the first lens L1 and the second lens L2 or between the second lens L2 and the third lens L3. In the present invention, the first lens L1 is a convex-concave lens, the second lens L2 is a concave-convex lens, the third lens L3 is a biconvex lens, the fourth lens L4 is a biconcave lens, and the fifth lens L5 is a biconvex lens. The first lens L1, the fourth lens L4, and the fifth lens L5 are plastic aspherical lenses, the third lens L3 is a glass lens, and the second lens L2 is a plastic aspherical lens or a glass lens. In this way, in the fixed-focus lens of the present invention, the above form of combining glass and plastic lenses and the optimization of the combination of positive and negative optical powers correct the aberration and solve the thermal drift problem of the lens in the high and low temperature states of 80°C and -40°C, increasing the range of use occasions and environmental conditions of the lens.

[0058] In the present invention, the following relational expressions are respectively satisfied between the sag SAG11 of the maximum optical effective diameter of the object side surface (near the object side) of the first lens L1 and its curvature radius R1, and the sag SAG12 of the maximum optical effective diameter of the image side surface (near the image side) of the first lens L1 and its curvature radius R2: 1.0 ≤ R1 / SAG11 ≤ 1.5; 0.5 ≤ R2 / SAG12 ≤ 1.0. In this way, this relationship between the curvature radius and the sag can effectively control the aperture size of the first lens L1, thereby reducing the incident height when the chief ray enters the optical system, reducing the distortion and correcting the aberration of the off-axis field. At the same time, this setting method also reduces the number of lenses required.

[0059] In the present invention, the curvature radius R21 of the object side surface of the second lens L2 and the curvature radius R12 of the image side surface of the first lens L1 satisfy the following relational expression: -2.5 ≤ R21 / R12 ≤ -1.5. Such a matching relationship between the curvature radii can improve the light-gathering efficiency of the lens and is beneficial to reducing the volume of the lens at the front end of the lens. The chief ray angle CRA of the maximum field of view of the fixed-focus lens satisfies the following condition: CRA ≤ 12°. Such a setting can reduce the generation of reflected light, increase the intensity of the light transmitted through the lens to the sensor for imaging, and thus improve the imaging quality. The optical power φ3 of the third lens L3 and the optical power φII of the lens group on the image side of the stop STO satisfy the following relational expression: 0.7 ≤ φ3 / φII ≤ 1.3. Such an optical power distribution method can improve the light transmissibility in the lens, thereby reducing the volume of the lens and realizing the reduction of production costs. The distance M1 between the center on the object side surface of the first lens L1 and the stop STO, the distance M2 between the center on the image side surface of the fifth lens L5 and the stop STO, and the overall optical length TTL of the fixed-focus lens respectively satisfy the following relational expressions: 0.15 ≤ M1 / TTL ≤ 0.32; 0.33 ≤ M2 / TTL ≤ 0.51. The above settings ensure that the positional relationship between the object and image side groups of the stop can make the overall lens more compact and realize the miniaturization of the lens volume.

[0060] In the present invention, the focal length f1 of the first lens L1, the focal length f2 of the second lens L2, the focal length f3 of the third lens L3, the focal length f4 of the fourth lens L4, the focal length f5 of the fifth lens L5, and the effective focal length f of the fixed-focus lens respectively satisfy the following relational expressions: -4.2 ≤ f1 / f ≤ -2.5; 2 ≤ f2 / f ≤ 12; 1 ≤ f3 / f ≤ 1.5; -0.9 ≤ f4 / f ≤ -0.5; 0.5 ≤ f5 / f ≤ 0.9. According to the above positive and negative optical power distribution methods for each lens, the aberration of the fixed-focus lens is corrected to ensure clear imaging of the lens.

[0061] In the present invention, the lens group on the image side of the aperture STO includes at least one glass lens made of a low-dispersion coefficient material with an Abbe number Vd > 75. This low-dispersion coefficient material can correct the chromatic aberration of the lens, enabling the lens to clearly image both the visible and near-infrared spectra, and can balance the resolution at high and low temperatures. The focal length f4 of the fourth lens L4 and the focal length f5 of the fifth lens L5 satisfy the following relational expression: -1.1 ≤ f4 / f5 ≤ -0.6. In this way, the positive and negative optical power matching of the fourth and fifth lenses L4 and L5 can improve the image quality and further control the focus drift of the lens within a reasonable range at high and low temperatures. The optical total length TTL of the fixed-focus lens and the aperture FNO satisfy the following conditions: TTL ≤ 22.5 mm, FNO ≤ 1.6. In this way, under the condition of a certain total length, the largest possible aperture is achieved, enabling clear imaging without focusing adjustment in darkroom conditions such as at night. The optical total length TTL of the fixed-focus lens and the effective focal length f satisfy the following relational expression: TTL / f ≤ 3.0. This proportional relationship between the optical total length and the focal length of the lens realizes the advantage of a compact lens volume.

[0062] In summary, the fixed-focus lens of the present invention has a total of five lenses, and the maximum number of plastic aspherical lenses can reach four, which can improve the performance of the fixed-focus lens and greatly reduce the cost of the lens to enhance product competitiveness. Moreover, by matching the lens materials and optical powers, the aberration can be corrected, and the thermal drift problem of the lens at high and low temperatures of 80°C and -40°C can be solved, thereby increasing the range of usage occasions and environmental conditions of the lens. The setting of at least one lens made of a low-dispersion material can also balance the purple fringing and high-quality imaging of near-infrared light, thereby further correcting the chromatic aberration of the lens, achieving visible-infrared confocal, and further enhancing the market competitiveness of the lens.

[0063] The following uses four sets of embodiments to specifically illustrate the fixed-focus lens of the present invention. In the following embodiments, 1, 2,..., N are used to represent the surfaces of each lens, and the aperture can also be denoted as STO. The image plane on the image side of the entire fixed-focus lens is not shown in the figure. The aspherical lens surfaces of all the following embodiments satisfy the following formula:

[0064] Z = cy 2 / {1 + [1 - (1 + k)c 2 y 2 1 / 2}+a4y 4 +a6y 6 +a8y 8 +a 10 y 10 +a 12 y 12 +a 14 y 14 ;

[0065] ​Among them, Z is the axial distance from the vertex to the surface at a position with a height h perpendicular to the optical axis along the optical axis direction; c represents the curvature at the vertex of the aspherical surface; y is the radial coordinate of the aspherical lens; k is the conic coefficient; a4, a6, a8, a 10 、a 12 、a 14 respectively represent the aspherical coefficients of the fourth, sixth, eighth, tenth, twelfth, and fourteenth orders.

[0066] The parameter settings of the following embodiments satisfy Table 1 below:

[0067]

[0068]

[0069] Table 1

[0070] The first embodiment:

[0071] Referring to Figure 1 , in this embodiment, the aperture STO is located between the first lens L1 and the second lens L2, and the first lens L1, the second lens L2, the fourth lens L4, and the fifth lens L5 are aspherical lenses. Among them, the focal length is 8.06 mm, the FNO is 1.45, and the total length is 22.5 mm.

[0072] The relevant parameters of each lens in this embodiment, including the surface type, radius of curvature, k value, thickness, refractive index, and Abbe number, are shown in Table 2:

[0073] Surface Serial Number Surface Type Radius of Curvature Thickness Refractive Index Abbe Number 1 Aspherical Surface 2.545 1.111 1.49 55.76 2 Aspherical Surface 1.876 3.713 3(STO) Spherical Surface Infinity 1.317 4 Aspherical Surface -3.869 1.764 1.62 27.78 5 Aspherical Surface -3.378 0.116 6 Spherical Surface 7.985 3.149 1.429 95.18 7 Spherical Surface -8.226 0.115 8 Aspherical Surface -29.928 0.378 1.64 23.53 9 Aspherical Surface 3.316 0.155 10 Aspherical Surface 5.097 3.692 1.60 39.9 11 Aspherical Surface -7.427 5.99 12 Spherical Surface Infinity 0.80 1.517 64.2 13 Spherical Surface Infinity 0.20 Image Plane Spherical Surface Infinity -

[0074] Table 2

[0075] The K value and aspherical coefficients of this embodiment are shown in Tables 3 and 4 below:

[0076]

[0077]

[0078] Table 3

[0079] Surface Serial Number <![CDATA[a 12 > <![CDATA[a 14 > 1 -2.76786E-008 -2.72369E-010 2 -4.77275E-007 -8.22742E-009 4 -9.55635E-008 -3.68024E-009 5 -1.68827E-008 6.44913E-010 8 1.61221E-009 1.56433E-008 9 -7.54917E-007 2.71181E-008 10 2.47917E-007 -6.52647E-009 11 -7.46027E-008 7.14736E-010

[0080] Table 4

[0081] Combined with Figure 2 and Figure 3 It can be known that the fixed-focus lens of this embodiment combines Figure 2 It can be known that the fixed-focus lens of this embodiment has better aberration correction within the spectral bandwidth, and the resolving power is greatly improved, so that the clarity of the actual shooting picture of the lens can be increased; Figure 3It shows that the field curvature and distortion can be corrected to an appropriate range, so that the meridional resolving power can be close to the sagittal resolving power, and the best imaging plane can be located in the vertical plane of the chip photosensitive surface, making the resolving power of the lens picture uniform.

[0082] The second implementation mode:

[0083] Refer to Figure 4 , in this implementation mode, the aperture STO is located between the second lens L2 and the third lens L3, and the first lens L1, the second lens L2, the fourth lens L4, and the fifth lens L5 are aspherical lenses. Among them, the focal length is 7.7 mm, the FNO is 1.5, and the total length is 22.028 mm.

[0084] The relevant parameters of each lens in this implementation mode, including the surface type, radius of curvature, k value, thickness, refractive index, and Abbe number, are shown in Table 5:

[0085] Surface Serial Number Surface Type Radius of Curvature Thickness Refractive Index Abbe Number 1 Aspherical Surface 2.702 1.107 1.533 59.8 2 Aspherical Surface 1.921 3.611 3 Aspherical Surface -3.807 1.723 1.69 32.95 4 Aspherical Surface -3.424 0.203 5(STO) Spherical Surface Infinity 0.618 6 Spherical Surface 8.847 1.996 1.49 78.2 7 Spherical Surface -7.934 0.462 8 Aspherical Surface -29.421 0.644 1.644 26.18 9 Aspherical Surface 3.832 1.533 10 Aspherical Surface 6.229 3.151 1.527 67.37 11 Aspherical Surface -6.845 5.98 12 Spherical Surface Infinity 0.8 1.517 64.2 13 Spherical Surface Infinity 0.2 Image Plane Spherical Surface Infinity -

[0086] Table 5 The K values and aspherical coefficients of this implementation mode are shown in Table 6 and Table 7 as follows:

[0087]

[0088]

[0089] Table 6

[0090] Surface Serial Number <![CDATA[a 12 > <![CDATA[a 14 > 1 -1.91588E-008 -7.25001E-010 2 -5.13927E-007 3.66901E-011 3 3.86707E-008 -2.76602E-010 4 9.42359E-008 8.51741E-011 8 -1.46809E-009 1.30402E-009 9 -5.20514E-007 2.85403E-009 10 1.8910E-007 -2.93021E-010 11 6.21331E-008 4.10703E-010

[0091] Table 7

[0092] Combined with Figure 5 and Figure 6 It can be known that the fixed-focus lens of this implementation mode combines Figure 5 It can be known that the fixed-focus lens of this implementation mode corrects the aberration well within the spectral bandwidth, which can increase the clarity of the actual shooting picture of the lens; Figure 6 It shows that the field curvature and distortion can be corrected to an appropriate range, so that the meridional resolving power can be close to the sagittal resolving power, making the resolving power of the lens picture uniform.

[0093] The third implementation mode:

[0094] Refer to Figure 7 , in this implementation mode, the aperture STO is located between the first lens L1 and the second lens L2, and the first lens L1, the fourth lens L4, and the fifth lens L5 are aspherical lenses. Among them, the focal length is 7.8 mm, the FNO is 1.53, and the total length is 22.5 mm.

[0095] The relevant parameters of each lens in this embodiment, including surface type, radius of curvature, k value, thickness, refractive index, and Abbe number, are shown in Table 8:

[0096] Surface Serial Number Surface Type Radius of Curvature Thickness Refractive Index Abbe Number 1 Aspherical Surface 2.627 1.145 1.597 68.4 2 Aspherical Surface 1.871 2.94 3(STO) Spherical Surface Infinity 1.369 4 Spherical Surface -3.751 1.581 1.597 31.04 5 Spherical Surface -4.055 0.265 6 Spherical Surface 7.307 3.132 1.474 89.94 7 Spherical Surface -8.164 0.121 8 Aspherical Surface -36.137 1.347 1.607 35.83 9 Aspherical Surface 3.771 0.294 10 Aspherical Surface 4.290 3.239 1.545 57.85 11 Aspherical Surface -8.049 6.067 12 Spherical Surface Infinity 0.80 1.517 64.21 13 Spherical Surface Infinity 0.2 Image Plane Spherical Surface Infinity -

[0097] Table 8

[0098] The K value and aspheric coefficient of this embodiment are shown in Tables 9 and 10 as follows:

[0099]

[0100] Table 9

[0101]

[0102]

[0103] Table 10

[0104] Combined with Figure 8 and Figure 9 it can be known that the fixed-focus lens of this embodiment combined with Figure 8 it can be known that the fixed-focus lens of this embodiment has better aberration correction within the spectral bandwidth, which can increase the clarity of the actual shooting picture of the lens; Figure 9 It shows that the field curvature and distortion can be corrected to an appropriate range, so that the meridional resolving power can be similar to the sagittal resolving power, making the resolving power of the lens picture uniform.

[0105] The fourth embodiment:

[0106] Referring to Figure 10 , the aperture STO in this embodiment is located between the first lens L1 and the second lens L2, and the first lens L1, the second lens L2, the fourth lens L4, and the fifth lens L5 are aspherical lenses. Among them, the focal length is 7.78 mm, the FNO is 1.57, and the total length is 22.5 mm.

[0107] The relevant parameters of each lens in this embodiment, including surface type, radius of curvature, k value, thickness, refractive index, and Abbe number, are shown in Table 11:

[0108] Surface Serial Number Surface Type Radius of Curvature Thickness Refractive Index Abbe Number 1 Aspherical Surface 2.568 1.115 1.547 54.32 2 Aspherical Surface 1.791 3.264 3(STO) Spherical Surface Infinity 1.323 4 Aspherical Surface -4.041 1.681 1.637 25.17 5 Aspherical Surface -3.450 0.243 6 Spherical Surface 8.310 3.078 1.485 82.97 7 Spherical Surface -8.069 0.14 8 Aspherical Surface -33.662 0.597 1.640 22.878 9 Aspherical Surface 3.532 0.686 10 Aspherical Surface 5.089 3.351 1.538 48.22 11 Aspherical Surface -7.894 6.022 12 Spherical Surface Infinity 0.80 1.517 64.2 13 Spherical Surface Infinity 0.20 Image Plane Spherical Surface Infinity -

[0109] The K value and aspheric coefficient of this embodiment are shown in Tables 12 and 13 as follows:

[0110]

[0111] Table 12

[0112] Surface Serial Number <![CDATA[a 12 > <![CDATA[a 14 > 1 -2.08811E-008 -6.75443E-011 2 -4.55921E-007 4.30398E-009 4 -1.07433E-007 -4.59649E-009 5 -2.47149E-008 -3.75587E-010 8 -6.59045E-009 1.28133E-008 9 -7.19470E-007 2.75872E-008 10 2.77715E-007 -2.99212E-009 11 -5.16489E-008 4.30589E-009

[0113] Table 13

[0114] Combined with Figure 11 and Figure 12 It can be seen that the fixed-focus lens of this embodiment combines Figure 11 It can be seen that the fixed-focus lens of this embodiment has better aberration correction within the spectral bandwidth, which can increase the clarity of the actual shooting picture of the lens; Figure 12 It shows that the field curvature and distortion can be corrected to an appropriate range, so that the meridional resolving power can be close to the sagittal resolving power, making the resolving power of the lens picture uniform.

[0115] The above is only one embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fixed-focus lens, characterized in that, Including, arranged in sequence 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 positive optical power, a fourth lens (L4) with negative optical power, and a fifth lens (L5) with positive optical power, with a total of five lenses having optical power; The following relationships are respectively satisfied between the sag SAG11 of the maximum optical effective diameter of the object side surface of the first lens (L1) and its curvature radius R1, and the sag SAG12 of the maximum optical effective diameter of the image side surface of the first lens (L1) and its curvature radius R2: 1.0 ≤ R1 / SAG11 ≤ 1.5; 0.5 ≤ R2 / SAG12 ≤ 1.

0.

2. The fixed-focus lens according to claim 1, wherein, It further includes a stop (STO) located between the first lens (L1) and the second lens (L2) or between the second lens (L2) and the third lens (L3).

3. The fixed-focus lens according to claim 1, wherein The first lens (L1) is a convex-concave lens, the second lens (L2) is a concave-convex lens, the third lens (L3) is a biconvex lens, the fourth lens (L4) is a biconcave lens, and the fifth lens (L5) is a biconvex lens.

4. The fixed-focus lens according to claim 1, wherein The first lens (L1), the fourth lens (L4), and the fifth lens (L5) are plastic aspherical lenses, the third lens (L3) is a glass lens, and the second lens (L2) is a plastic aspherical lens or a glass lens.

5. The fixed-focus lens according to any one of claims 1-4, characterized in that The following relationship is satisfied between the curvature radius R21 of the object side surface of the second lens (L2) and the curvature radius R12 of the image side surface of the first lens (L1): -2.5 ≤ R21 / R12 ≤ -1.

5.

6. The fixed-focus lens according to any one of claims 1-4, characterized in that, The chief ray angle CRA of the maximum field of view of the fixed-focus lens satisfies the following condition: CRA ≤ 12°.

7. The fixed-focus lens according to claim 2, wherein, The following relationship is satisfied between the optical power φ3 of the third lens (L3) and the optical power φII of the lens group on the image side of the stop (STO): 0.7 ≤ φ3 / φII ≤ 1.

3.

8. The fixed-focus lens according to claim 2, characterized in that, The following relationships are respectively satisfied between the distance M1 from the center on the object side surface of the first lens (L1) to the stop (STO), the distance M2 from the center on the image side surface of the fifth lens (L5) to the stop (STO), and the overall optical length TTL of the fixed-focus lens: 0.15 ≤ M1 / TTL ≤ 0.32; 0.33 ≤ M2 / TTL ≤ 0.

51.

9. The fixed-focus lens according to any one of claims 1-4, characterized in that, The following relationships are respectively satisfied between the focal length f1 of the first lens (L1), the focal length f2 of the second lens (L2), the focal length f3 of the third lens (L3), the focal length f4 of the fourth lens (L4), the focal length f5 of the fifth lens (L5), and the effective focal length f of the fixed-focus lens: -4.2 ≤ f1 / f ≤ -2.5; 2 ≤ f2 / f ≤ 12; 1 ≤ f3 / f ≤ 1.5; -0.9 ≤ f4 / f ≤ -0.5; 0.5 ≤ f5 / f ≤ 0.

9.

10. The fixed-focus lens according to claim 2, characterized in that, The lens group on the image side of the stop (STO) includes at least one glass lens made of a low-dispersion coefficient material with an Abbe number Vd > 75.

11. The fixed-focus lens according to any one of claims 1-4, characterized in that, The focal length f4 of the fourth lens (L4) and the focal length f5 of the fifth lens (L5) satisfy the following relational expression: -1.1 ≤ f4 / f5 ≤ -0.

6.

12. The fixed-focus lens according to any one of claims 1-4, characterized in that, The overall optical length TTL of the fixed-focus lens and the aperture FNO satisfy the following conditions: 22.028 ≤ TTL ≤ 22.5 mm, 1.45 ≤ FNO ≤ 1.

6.

13. The fixed-focus lens according to any one of claims 1-4, characterized in that, The overall optical length TTL of the fixed-focus lens and the effective focal length f satisfy the following relational expression: 2.79 ≤ TTL / f ≤ 3.0.

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