Prime lens

Abstract

The prime lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are sequentially arranged from an object plane to an image plane along an optical axis, the first lens has negative focal power, the second lens has positive focal power, the third lens has negative focal power, the fourth lens has positive focal power, the fifth lens has negative focal power, the sixth lens has positive focal power, and the seventh lens has negative focal power. The fifth lens has positive focal power, the sixth lens has negative focal power, and the seventh lens has positive focal power. According to the prime lens provided by the embodiment of the utility model, only seven lenses are adopted, and the focal power of each lens is reasonably distributed, so that the aperture number F of the prime lens reaches 1.28, the image plane size can reach 7.1 mm, the prime lens can be matched with a 1 / 2.7 ''target surface sensor chip at most, the total length can reach 22mm, and the prime lens can support the resolution of more than 5MP; the prime lens with a large aperture, a small size and low cost under a large target surface is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of optics, in particular to a fixed-focus lens. Background Art

[0002] As monitoring facilities become increasingly sophisticated, monitoring equipment has higher and higher requirements for the environment and images it uses. At the same time, the market's requirements for lens costs are becoming more and more stringent.

[0003] In order to make monitoring equipment work better at night and in low-light environments, various large-aperture lenses have emerged. At present, the large-aperture high-definition lenses with larger target areas commonly seen on the market mostly use a structure with a total of 8 to 9 lenses. The production cost is high and the size is large, which limits the wide application of the lens. Utility Model Content

[0004] The utility model provides a fixed-focus lens, which realizes a small fixed-focus lens with low cost, large aperture and large target surface.

[0005] The embodiment of the utility model provides a fixed-focus lens, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence along the optical axis from the object plane to the image plane;

[0006] The first lens has negative optical power, the second lens has positive optical power, the third lens has negative optical power, the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, and the seventh lens has positive optical power;

[0007] The optical power of the fixed focus lens is The optical power of the first lens is The optical power of the second lens is The optical power of the third lens is The optical power of the fourth lens is The optical power of the fifth lens is The optical power of the sixth lens is The optical power of the seventh lens is

[0008]

[0009] Optionally, the object-side surface of the first lens is convex, and the image-side surface is concave;

[0010] The object side surface of the second lens is concave, and the image side surface is convex;

[0011] The object side surface of the third lens is concave, and the image side surface is convex;

[0012] The object-side surface of the fourth lens is convex, and the image-side surface is convex;

[0013] The object-side surface of the fifth lens is convex, and the image-side surface is convex;

[0014] The object-side surface of the sixth lens is concave, and the image-side surface is concave;

[0015] The object-side surface of the seventh lens is convex, and the image-side surface is convex.

[0016] Optionally, a distance between the fifth lens and the sixth lens on the optical axis is less than or equal to 0.1 mm;

[0017] A distance between the sixth lens and the seventh lens on the optical axis is less than or equal to 0.1 mm.

[0018] Optionally, a distance between the fifth lens and the sixth lens on the optical axis is greater than or equal to 0.03 mm;

[0019] A distance between the sixth lens and the seventh lens on the optical axis is greater than or equal to 0.03 mm.

[0020] Optionally, the first lens, the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are all plastic aspheric lenses;

[0021] The fourth lens is a glass spherical lens.

[0022] 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, and the refractive index of the seventh lens is n7;

[0023] 1.49≤n1≤1.62;1.49≤n2≤1.71;1.49≤n3≤1.71;1.39≤n4≤1.64;

[0024] 1.49≤n5≤1.60; 1.59≤n6≤1.70; 1.49≤n7≤1.60.

[0025] Optionally, the image plane diameter of the fixed-focus lens is IC, and the total length of the fixed-focus lens is TTL;

[0026] IC / TTL≥0.3.

[0027] Optionally, the fixed-focus lens further includes a diaphragm;

[0028] The aperture is located in an optical path between the third lens and the fourth lens.

[0029] Optionally, the total length of the fixed-focus lens is TTL, and TTL≤22.3 mm.

[0030] Optionally, the aperture number of the fixed-focus lens is F, F≤1.28.

[0031] The fixed-focus lens provided in the embodiment of the present invention uses only seven lenses. By rationally allocating the optical power of each lens, the aperture number F of the fixed-focus lens reaches 1.28, the image plane size can reach 7.1mm, and it can match a sensor chip with a maximum target surface of 1 / 2.7". The total length can reach 22mm and can support a resolution of 5MP or more. This realizes a fixed-focus lens with a large aperture, small size, and low cost under a large target surface.

[0032] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 A schematic structural diagram of a fixed-focus lens provided in an embodiment of the present utility model;

[0035] Figure 2 A schematic structural diagram of another fixed-focus lens provided in an embodiment of the present utility model;

[0036] Figure 3 A schematic structural diagram of another fixed-focus lens provided in an embodiment of the present utility model;

[0037] Figure 4 This is a spherical aberration curve diagram of the fixed-focus lens provided in Example 1 of the present utility model;

[0038] Figure 5 This is a distortion diagram of the fixed-focus lens provided in Example 1 of the present utility model;

[0039] Figure 6 This is a spherical aberration curve diagram of the fixed-focus lens provided in Example 2 of the present utility model;

[0040] Figure 7 This is a distortion diagram of the fixed-focus lens provided in Example 2 of the present utility model;

[0041] Figure 8 This is a spherical aberration curve diagram of the fixed-focus lens provided in Example 3 of the present utility model;

[0042] Figure 9 This is a distortion diagram of the fixed-focus lens provided in Example 3 of the present utility model. DETAILED DESCRIPTION

[0043] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0045] Figure 1 This is a structural diagram of a fixed-focus lens provided by an embodiment of the present utility model. Figure 2 This is a schematic structural diagram of another fixed-focus lens provided by an embodiment of the present utility model. Figure 3 A structural diagram of another fixed-focus lens provided in an embodiment of the present invention is shown in FIG. Figures 1-3 As shown, the fixed-focus lens provided by the embodiment of the present invention includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7, which are arranged in sequence along the optical axis from the object plane to the image plane. The first lens L1 has a negative focal power, the second lens L2 has a positive focal power, the third lens L3 has a negative focal power, the fourth lens L4 has a positive focal power, the fifth lens L5 has a positive focal power, the sixth lens L6 has a negative focal power, and the seventh lens L7 has a positive focal power. The focal power of the fixed-focus lens is The optical power of the first lens L1 is The optical power of the second lens L2 is The optical power of the third lens L3 is The optical power of the fourth lens L4 is The optical power of the fifth lens L5 is The optical power of the sixth lens L6 is The optical power of the seventh lens L7 is

[0046]

[0047] Specifically, the focal length is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam, and it characterizes the ability of an optical system to deflect light. The larger the absolute value of the focal length, the stronger the ability to bend light, and the smaller the absolute value of the focal length, the weaker the ability to bend light. When the focal length is a positive number, the refraction of light is convergent; when the focal length is a negative number, the refraction of light is divergent. The focal length can be used to characterize a refractive surface of a lens (i.e., a surface of a lens), a single lens, or a system formed by multiple lenses (i.e., a lens group).

[0048] In the fixed-focus lens provided in this embodiment, each lens can be fixed to a lens barrel ( Figure 1 (not shown), but is not limited thereto.

[0049] Specifically, the first lens L1 has a negative optical power, making it a diverging lens, which can expand the beam of incident light, allowing more light to enter the subsequent lens group, thereby facilitating the realization of a larger aperture.

[0050] The second lens L2 has positive refractive power, and the third lens L3 has negative refractive power, which can well complete the transition of the light diverged by the first lens L1.

[0051] The fourth lens L4 has positive refractive power and plays a key role in the light converging process.

[0052] The fifth lens L5 has positive focal power, the sixth lens L6 has negative focal power, and the seventh lens L7 has positive focal power. These three lenses can further converge the light while correcting aberrations well and ensuring that the light is accurately focused on the image sensor, and have good control over the angle of the main light incident on the image sensor.

[0053] Among them, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7 adopt a negative-positive-negative-positive-positive-positive-negative-positive optical focal length combination, which can reasonably distribute the optical focal length of each lens so that light can propagate smoothly in the fixed-focus lens, avoiding excessive bending of light on a certain lens surface, which is conducive to ensuring image quality.

[0054] Furthermore, the focal length of the fixed-focus lens Refractive power of the first lens L1 The refractive power of the second lens L2 The refractive power of the third lens L3 Refractive power of the fourth lens L4 Refractive power of the fifth lens L5 Refractive power of sixth lens L6 And the optical power of the seventh lens L7 satisfy By controlling the optical power of the entire fixed-focus lens to be distributed in a certain proportion, while ensuring the functions of the above-mentioned lenses, it can also ensure the balance of the incident angles of the front and rear lenses, so as to reduce the sensitivity of the lenses, which is beneficial to improving the stability of the fixed-focus lens, and is beneficial to correcting system aberrations and improving image quality.

[0055] The fixed-focus lens provided in the embodiment of the present invention uses only seven lenses. By rationally allocating the optical power of each lens, the aperture number F of the fixed-focus lens reaches 1.28, the image plane size can reach 7.1mm, and it can match a sensor chip with a maximum target surface of 1 / 2.7". The total length can reach 22mm and can support a resolution of 5MP or more. This realizes a fixed-focus lens with a large aperture, small size, and low cost under a large target surface.

[0056] As a feasible implementation method, Figures 1-3 As shown, the object-side surface of the first lens L1 is convex, and the image-side surface is concave; the object-side surface of the second lens L2 is concave, and the image-side surface is convex; the object-side surface of the third lens L3 is concave, and the image-side surface is convex; the object-side surface of the fourth lens L4 is convex, and the image-side surface is convex; the object-side surface of the fifth lens L5 is convex, and the image-side surface is convex; the object-side surface of the sixth lens L6 is concave, and the image-side surface is concave; and the object-side surface of the seventh lens L7 is convex, and the image-side surface is convex.

[0057] Specifically, such as Figures 1-3 As shown, the object-side surface of the first lens L1 is convex, which helps to expand the angle of the incident light; the image-side surface is concave, which helps to control the divergence of the light. The shape of the first lens L1 adopts a convex front and concave back design, which can effectively control the incident angle of the light without increasing the diameter of the lens. This helps to reduce the physical size of the first lens L1, thereby reducing the effective aperture of the front end of the fixed-focus lens, making the entire lens more compact and lightweight.

[0058] Continue to refer Figures 1-3The object-side surfaces of the second lens L2 and the third lens L3 are both concave, and the image-side surfaces are both convex, making the shapes of the second lens L2 and the third lens L3 similar. Combined with the optical power distribution, the transition of the light diverged by the first lens L1 can be well completed, so that the light can smoothly transition to the subsequent lenses, which helps to avoid excessive bending of the light on a certain surface, thereby improving the imaging quality.

[0059] The optical focal length of the fourth lens L4 accounts for a relatively high proportion in the entire fixed-focus lens, which enables it to effectively control the path of light, ensure that the light propagates smoothly in the subsequent lens groups, and avoid excessive bending.

[0060] The object-side surface of the fifth lens L5 is convex, and the image-side surface is convex; the object-side surface of the sixth lens L6 is concave, and the image-side surface is concave; the object-side surface of the seventh lens L7 is convex, and the image-side surface is convex. As a result, the fifth lens L5, the sixth lens L6, and the seventh lens L7 can be regarded as a whole, which can have an effect similar to a triplet lens, while converging light, it can well correct chromatic aberration and other aberrations, and has good control over the angle of the principal light incident on the image sensor, thereby improving image quality.

[0061] It should be noted that the surface shape of the lens affects the direction of light propagation and determines how the light bends when passing through the lens, which in turn affects the maximum aperture and light throughput of the lens, as well as the quality and characteristics of the imaging.

[0062] In this embodiment, by rationally matching the surface shapes of the various lenses, while satisfying the optical power requirements of each lens and achieving the desired optical performance indicators (such as small size and large aperture), it is beneficial to further reduce the total optical length of the entire fixed-focus lens, thereby realizing a miniaturized lens design. In addition, while ensuring a large aperture, the path of light passing through the entire fixed-focus lens is made smoother, reducing unnecessary reflections and absorption, which is beneficial to improving light throughput and imaging quality.

[0063] As a feasible implementation manner, the distance between the fifth lens L5 and the sixth lens L6 on the optical axis is less than or equal to 0.1 mm, and the distance between the sixth lens L6 and the seventh lens L7 on the optical axis is less than or equal to 0.1 mm.

[0064] Specifically, by limiting the distance between the fifth lens L5 and the sixth lens L6 on the optical axis, and by making the distance between the sixth lens L6 and the seventh lens L7 on the optical axis smaller, the fifth lens L5, the sixth lens L6 and the seventh lens L7 can be regarded as a whole, thereby achieving an effect similar to a triplet lens. While converging light, it can effectively correct chromatic aberration and other aberrations, and has good control over the angle of the principal ray incident on the image sensor, thereby improving image quality.

[0065] As a feasible implementation manner, the distance between the fifth lens L5 and the sixth lens L6 on the optical axis is greater than or equal to 0.03 mm, and the distance between the sixth lens L6 and the seventh lens L7 on the optical axis is greater than or equal to 0.03 mm.

[0066] Wherein, a gap is defined between the fifth lens L5 and the sixth lens L6, and between the sixth lens L6 and the seventh lens L7 on the optical axis. Therefore, the fifth lens L5, the sixth lens L6, and the seventh lens L7 are not glued together, which can reduce production costs.

[0067] Furthermore, the fixed-focus lens provided in the embodiment of the present invention does not include a cemented lens, that is, each lens is an independent lens. This reduces production costs while making it easier to adjust and optimize each lens, thereby helping to adapt to different optical design requirements and improve imaging quality.

[0068] As a feasible implementation manner, the first lens L1, the second lens L2, the third lens L3, the fifth lens L5, the sixth lens L6 and the seventh lens L7 are all plastic aspherical lenses, and the fourth lens L4 is a glass spherical lens.

[0069] Specifically, the first lens L1 is a plastic aspherical lens, which is beneficial to reducing the effective aperture of the front end of the fixed-focus lens, making the entire lens more compact and lightweight.

[0070] The optical focal length of the fourth lens L4 accounts for a relatively high proportion in the entire fixed-focus lens. In this embodiment, the fourth lens L4 is set to be a glass lens. Compared with a plastic lens, the refractive index of a glass lens changes less with temperature, which helps to maintain the stability of the focal length of the fourth lens L4 at different temperatures. The glass material and large optical focal length design of the fourth lens L4 can effectively compensate for the aberrations and focal length drift caused by temperature changes of other lenses in the fixed-focus lens, thereby making the fixed-focus lens insensitive to high and low temperatures, and well balancing the effects of high and low temperatures on the entire fixed-focus lens. No obvious aberrations or other optical problems will be caused by temperature changes, ensuring that stable imaging quality can be provided under different environmental conditions.

[0071] Furthermore, the fourth lens L4 is a spherical lens, which is beneficial to reducing costs.

[0072] In addition, the first lens L1, the second lens L2, the third lens L3, the fifth lens L5, the sixth lens L6 and the seventh lens L7 are all aspherical lenses, which can correct the geometric aberrations of the fixed-focus lens, such as spherical aberration, coma and astigmatism, to improve the imaging quality of the entire fixed-focus lens.

[0073] Furthermore, the first lens L1, the second lens L2, the third lens L3, the fifth lens L5, the sixth lens L6 and the seventh lens L7 are all made of plastic lenses, which can reduce the cost and weight of the lenses.

[0074] It should be noted that the large aperture high-definition lenses with larger target surfaces commonly found on the market mostly use more than two glass lenses. The fixed-focus lens provided by the embodiment of the utility model uses only one glass lens, which reduces production costs while ensuring the target surface, aperture, high and low temperature performance.

[0075] As a feasible implementation manner, the refractive index of the first lens L1 is n1, the refractive index of the second lens L2 is n2, the refractive index of the third lens L3 is n3, the refractive index of the fourth lens L4 is n4, the refractive index of the fifth lens L5 is n5, the refractive index of the sixth lens L6 is n6, and the refractive index of the seventh lens L7 is n7, where 1.49≤n1≤1.62; 1.49≤n2≤1.71; 1.49≤n3≤1.71; 1.39≤n4≤1.64; 1.49≤n5≤1.60; 1.59≤n6≤1.70; and 1.49≤n7≤1.60.

[0076] Among them, the refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium. It is mainly used to describe the material's ability to refract light. Different materials have different refractive indices.

[0077] By properly selecting and matching the refractive indices of lens elements L1 through L7, light passes smoothly between the lenses, reducing unnecessary reflections and scattering, achieving high-definition imaging. This also ensures that light of different wavelengths is correctly converged to the same focal point as it passes through the entire fixed-focus lens, achieving confocal alignment of visible and infrared light. This allows the fixed-focus lens to maintain high-quality imaging under both visible light during the day and infrared light at night, enhancing its daytime and nighttime confocal capabilities.

[0078] As a feasible implementation, the image diameter of the fixed-focus lens is IC, the total length of the fixed-focus lens is TTL, and IC / TTL≥0.3.

[0079] The total length TTL of the fixed-focus lens refers to the distance from the optical axis center of the object-side surface of the first lens L1 to the image plane.

[0080] The image plane diameter IC and total length TTL of the fixed-focus lens meet IC / TTL ≥ 0.3, so as to expand the target surface while compressing the volume, so that the fixed-focus lens can cover a larger image sensor (sensor), providing higher resolution and better imaging quality.

[0081] As a feasible implementation method, Figures 1-3As shown, the fixed-focus lens further includes an aperture STO, which is located in the optical path between the third lens L3 and the fourth lens L4.

[0082] Among them, placing the aperture STO in the middle part of the fixed-focus lens is conducive to optimizing the path of light and ensuring that the light can be evenly distributed to the subsequent lens groups after passing through the aperture, thereby improving the imaging quality.

[0083] As a feasible implementation, the total length of the fixed-focus lens is TTL, and TTL is ≤ 22.3 mm.

[0084] The fixed-focus lens provided in this embodiment has a short overall length, a compact structure, and a small size, making it easy to install in various devices, especially in environments with limited space. At the same time, the compact design makes the fixed-focus lens more portable and easy to carry and use.

[0085] As a feasible implementation, the aperture number of the fixed-focus lens is F, and F≤1.28.

[0086] The fixed-focus lens provided in this embodiment has a larger aperture (ie, a smaller f-number), allowing more light to enter, and is suitable for monitoring at night and in low-light environments.

[0087] As a feasible implementation method, Figures 1-3 As shown, the fixed-focus lens may further include a flat glass CG, which is located on the image-side surface of the seventh lens L7. The flat glass CG can protect the image sensor from dust and pollution, thereby ensuring the imaging effect of the fixed-focus lens.

[0088] In some cases, the flat glass CG can also be used to correct specific aberrations or filter out unnecessary light, which is not specifically limited in the embodiments of the present invention.

[0089] Among them, the image sensor is used to convert the light signal collected by the fixed-focus lens into an electrical signal, which can then be used to generate a digital image or video through a series of processing steps.

[0090] In summary, the fixed-focus lens provided in the embodiment of the present invention adopts a glass-plastic hybrid structure of 7 lenses, 1G6P (1 glass lens and 6 plastic lenses), to achieve a low-cost, large aperture, large target surface, and a small, high-definition, athermal glass-plastic hybrid fixed-focus lens that takes infrared into consideration.

[0091] Specific embodiments of fixed-focus lenses applicable to the above-mentioned embodiments will be further described below with reference to the accompanying drawings.

[0092] Example 1

[0093] Continue to refer Figure 1The fixed-focus lens provided in the first embodiment of the present invention includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6 and a seventh lens L7, which are arranged in sequence from the object plane to the image plane along the optical axis.

[0094] The aperture STO is located in the optical path between the third lens L3 and the fourth lens L4.

[0095] The plate glass CG is located on the image-side surface of the seventh lens L7.

[0096] Table 1 details the surface type, curvature radius, thickness, material (refractive index / Abbe number) and semi-diameter of each lens in the fixed-focus lens provided in Example 1 in a feasible implementation manner. The fixed-focus lens in Table 1 corresponds to Figure 1 Prime lens shown.

[0097] Table 1 Design values ​​of optical physical parameters of fixed focus lens

[0098] Surface No. Surface Type Radius of Curvature Thickness Material (nd) Material (vd) Half Diameter S1 Asphere 4.608 0.88 1.535 55.71 4.443 S2 Asphere 1.814 2.35 2.826 S3 Asphere -18.436 1.872 1.64 23.503 2.615 S4 Asphere -6.015 0.682 2.574 S5 Asphere -2.693 2.152 1.535 55.71 2.405 S6 Asphere -4.185 0.85 2.973 STO Sphere PL -0.812 3.241 S8 Sphere 6.205 3.57 1.437 95.1 3.259 S9 Sphere -8.305 0.053 3.098 S10 Asphere 15.516 1.616 1.535 55.71 2.934 S11 Asphere -8.972 0.2 3.026 S12 Asphere -3.446 0.931 1.64 23.503 2.905 S13 Asphere -31.597 0.045 3.08 S14 Asphere 8.181 2.541 1.535 55.71 3.341 S15 Asphere -7.434 4.501±0.5 3.33

[0099] The surface numbers in Table 1 are numbered according to the order of the surfaces of each lens. For example, surface number "S1" represents the object-side surface of the first lens, surface number "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of a fixed-focus lens. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value indicates that the surface is curved toward the object side with the center close to the image plane; a negative value indicates that the surface is curved toward the image side with the center close to the object plane. "PL" indicates that the surface is flat and has an infinite radius of curvature. Thickness represents the axial distance from the center of the current surface to the next surface. Refractive index represents the ability of the material between the current surface and the next surface to refract light. A blank space indicates that the current position is air. Material (nd) is the refractive index, which represents the ability of the material between the current surface and the next surface to refract light. A blank space indicates that the current position is air and has a refractive index of 1. Material (vd) is the Abbe number, which represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air. Semi-diameter represents the half-height of the corresponding light on the surface of each lens.

[0100] In this embodiment, the aspheric cone coefficient of the aspheric lens in the fixed-focus lens can be defined by the following aspheric formula, but is not limited to the following expression method:

[0101]

[0102] Where Z is the sagittal height of the aspheric surface; c is the basic curvature at the vertex; k is the conic constant; r is the radial coordinate perpendicular to the optical axis; a i is the coefficient of the higher-order term, a i r 2iis the high-order term of the aspheric surface.

[0103] For example, Table 2 describes in detail the aspheric conic coefficients of each lens in the first embodiment in a feasible implementation manner.

[0104] Table 2 Design values ​​of aspheric cone coefficients of each lens in fixed-focus lens

[0105]

[0106] The fixed-focus lens of the first embodiment can achieve the following technical indicators:

[0107] Focal length: 3.873mm;

[0108] Aperture: F1.28;

[0109] Field of view: 116.6°

[0110] Total optical length: 22.3mm;

[0111] Image size: φ7.1mm.

[0112] Figure 4 This is a spherical aberration curve diagram for the fixed-focus lens provided in Example 1 of the present invention. The vertical direction in the diagram represents the normalized zero-field-of-view pupil plane, where 0 represents the pupil center and the vertical vertex represents the pupil vertex. The horizontal direction represents the spherical aberration at different wavelengths, measured in millimeters. The different linear curves in the diagram represent different wavelengths imaged by the fixed-focus lens. Figure 4 The medium pupil radius is 1.5128mm, and the axial aberration at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.587μm and 0.656μm) is controlled within the range of (-0.1mm, +0.1mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0113] Figure 5 This is a distortion diagram of the fixed-focus lens provided in Example 1 of the present utility model. The horizontal coordinate in the diagram represents the magnitude of the distortion, and the unit is %, while the vertical coordinate represents the normalized image height, and there is no unit. Figure 5 The maximum field of view is 58.3 degrees, and distortion is well corrected.

[0114] Example 2

[0115] Continue to refer Figure 2 The fixed-focus lens provided in the second embodiment of the present invention includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6 and a seventh lens L7, which are arranged in sequence from the object plane to the image plane along the optical axis.

[0116] The aperture STO is located in the optical path between the third lens L3 and the fourth lens L4.

[0117] The plate glass CG is located on the image-side surface of the seventh lens L7.

[0118] Table 3 details the surface type, curvature radius, thickness, material (refractive index / Abbe number) and semi-diameter of each lens in the fixed-focus lens provided in Example 2 in a feasible implementation manner. The fixed-focus lens in Table 3 corresponds to Figure 2 Prime lens shown.

[0119] Table 3 Design values ​​of optical physical parameters of fixed focus lens

[0120]

[0121] The surface numbers in Table 3 are numbered according to the order of the surfaces of each lens. For example, surface number "S1" represents the object-side surface of the first lens, surface number "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of a fixed-focus lens. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value indicates that the surface is curved toward the object side with the center close to the image plane; a negative value indicates that the surface is curved toward the image side with the center close to the object plane. "PL" indicates that the surface is flat and has an infinite radius of curvature. Thickness represents the axial distance from the center of the current surface to the next surface. Refractive index represents the ability of the material between the current surface and the next surface to refract light. A blank space indicates that the current position is air. Material (nd) is the refractive index, which represents the ability of the material between the current surface and the next surface to refract light. A blank space indicates that the current position is air and has a refractive index of 1. Material (vd) is the Abbe number, which represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air. Semi-diameter represents the half-height of the corresponding light on the surface of each lens.

[0122] In this embodiment, the aspheric cone coefficient of the aspheric lens in the fixed-focus lens can be defined by the following aspheric formula, but is not limited to the following expression method:

[0123]

[0124] Where Z is the sagittal height of the aspheric surface; c is the basic curvature at the vertex; k is the conic constant; r is the radial coordinate perpendicular to the optical axis; a i is the coefficient of the higher-order term, a i r 2i is the high-order term of the aspheric surface.

[0125] For example, Table 4 details the aspheric conic coefficients of each lens in the second embodiment in a feasible implementation manner.

[0126] Table 4 design values of aspheric conic coefficients of each lens in the fixed focus lens

[0127]

[0128] The fixed focus lens of the second embodiment can achieve the following technical indexes:

[0129] Focal length: 3.54mm;

[0130] Aperture: F1.28;

[0131] Field of view: 145°;

[0132] Total optical length: 22.3mm;

[0133] Image size: φ7.1mm.

[0134] Figure 6 The fixed focus lens of the second embodiment provides a spherical aberration curve, wherein the vertical direction in the figure represents the normalization of the 0 field of view pupil surface, 0 represents the pupil center, and the vertical direction top represents the pupil vertex; the horizontal direction is the spherical aberration of different wavelengths, in millimeters (Millimeters); and different linear curves in the figure represent different wavelengths of the fixed focus lens imaging. Figure 6 The middle pupil radius is 1.3828mm, the axial aberration under different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.587μm and 0.656μm) is controlled within the range of (-0.1mm, +0.1mm), and the spherical aberration of the fixed focus lens at each wavelength is well controlled, which can meet the wide spectrum application requirement.

[0135] Figure 7 The fixed focus lens of the second embodiment provides a distortion graph, wherein the horizontal coordinate in the figure represents the size of the distortion, in %; and the vertical coordinate represents the normalized image height, without unit. Figure 7 The maximum field of view is 72.5 degrees, and the distortion is well corrected.

[0136] Embodiment three

[0137] Continuing to refer to Figure 3 , the fixed focus lens provided by the third embodiment of the utility model comprises a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6 and a seventh lens L7 which are arranged in sequence along an optical axis from an object plane to an image plane.

[0138] The diaphragm STO is located in the light path between the third lens L3 and the fourth lens L4.

[0139] The flat glass CG is located on one side of the image side of the seventh lens L7.

[0140] Table 5 details the surface type, radius of curvature, thickness, material (refractive index / Abbe number) and half-diameter of each lens in the fixed-focus lens provided in Example Three in one possible implementation. The fixed-focus lens in Table 5 corresponds to the fixed-focus lens shown in FIG. 1. Figure 3

[0141] Table 5 Design values of optical physical parameters of the fixed-focus lens

[0142]

[0143]

[0144] wherein the surface number in Table 5 is numbered according to the surface order of each lens, for example, the surface number "SI" represents the object side surface of the first lens, the surface number "S2" represents the image side surface of the first lens, and so on; "STO" represents the stop of the fixed-focus lens; the radius of curvature represents the bending degree of the corresponding lens surface, a positive value represents that the surface bends to the object side, and the center is close to the image side; a negative value represents that the surface bends to the image side, and the center is close to the object side, wherein "PL" indicates that the surface is a plane, and the radius of curvature is infinite; the thickness represents the center axial distance from the current surface to the next surface; the refractive index represents the deflection ability of the material between the current surface and the next surface; and the space represents that the current position is air. The material (nd) is the refractive index, which represents the deflection ability of the material between the current surface and the next surface, and the space represents that the current position is air, and the refractive index is 1; the material (vd) is the Abbe number, which represents the dispersion characteristics of the material between the current surface and the next surface, and the space represents that the current position is air; and the half-diameter represents the corresponding light half-height on the surface of each lens.

[0145] In this embodiment, the aspheric conic coefficients of the aspheric lenses in the fixed-focus lens can be defined by the following aspheric formula, but are not limited to the following representation method:

[0146]

[0147] wherein Z is the sag of the aspheric surface; c is the basic curvature at the vertex; k is the conic constant; r is the radial coordinate perpendicular to the optical axis; a i is the high-order term coefficient, a i r 2i is the high-order term of the aspheric surface.

[0148] For example, Table 6 details the aspheric conic coefficients of each lens in this embodiment in one possible implementation.

[0149] Table 6 Design values of aspheric conic coefficients of each lens in the fixed-focus lens

[0150] ​

[0151] The fixed focus lens of the third embodiment can achieve the following technical indexes:

[0152] Focal length: 4.156mm;

[0153] Aperture: F1.28;

[0154] Field of view: 120.0°;

[0155] Total optical length: 22.1mm;

[0156] Image surface size: φ7.1mm.

[0157] Figure 8 The spherical aberration curve of the fixed focus lens provided by the third embodiment of the present application, wherein the vertical direction in the figure represents the normalization of the 0 field of view pupil surface, 0 represents the pupil center, and the vertical direction top represents the pupil vertex; the horizontal direction is the spherical aberration of different wavelengths, in millimeters (Millimeters); and different linear curves in the figure represent different wavelengths of the fixed focus lens imaging. Figure 8 The middle pupil radius is 1.6233mm, the axial aberration under different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.587μm and 0.656μm) is controlled within the range of (-0.1mm, +0.1mm), which indicates that the spherical aberration of the fixed focus lens at each wavelength is well controlled, and the wide spectrum application requirement can be met.

[0158] Figure 9 The distortion graph of the fixed focus lens provided by the third embodiment of the present application, wherein the horizontal coordinate in the figure represents the size of the distortion, in %; and the vertical coordinate represents the normalized image height, without unit. Figure 9 The maximum field of view is 60 degrees, and the distortion is well corrected.

[0159] In order to more clearly illustrate the above embodiments, Table 7 details the specific optical physical parameters of each lens in the fixed focus lens provided by the first to third embodiments of the present application.

[0160] Table 7 Design values of optical physical parameters of the fixed focus lens

[0161]

[0162] The above specific embodiments do not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A fixed-focus lens, characterized in that: comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence along the optical axis from the object plane to the image plane; The first lens has negative optical power, the second lens has positive optical power, the third lens has negative optical power, the fourth lens has positive optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, and the seventh lens has positive optical power; The focal power of the fixed-focus lens is φ, the focal power of the first lens is φ1, the focal power of the second lens is φ2, the focal power of the third lens is φ3, the focal power of the fourth lens is φ4, the focal power of the fifth lens is φ5, the focal power of the sixth lens is φ6, and the focal power of the seventh lens is φ7; -0.631<φ1 / φ<-0.235; 0.18<φ2 / φ<0.419; -0.145<φ3 / φ<-0.015; 0.115<φ4 / φ<0.417; 0.234<φ5 / φ<0.458; -0.686<φ6 / φ<-0.328; 0.371<φ7 / φ<0.

642.

2. The fixed-focus lens according to claim 1, wherein: The object side surface of the first lens is convex, and the image side surface is concave; The object side surface of the second lens is concave, and the image side surface is convex; The object side surface of the third lens is concave, and the image side surface is convex; The object-side surface of the fourth lens is convex, and the image-side surface is convex; The object-side surface of the fifth lens is convex, and the image-side surface is convex; The object-side surface of the sixth lens is concave, and the image-side surface is concave; The object-side surface of the seventh lens is convex, and the image-side surface is convex.

3. The fixed-focus lens according to claim 1, wherein: The distance between the fifth lens and the sixth lens on the optical axis is less than or equal to 0.1 mm; A distance between the sixth lens and the seventh lens on the optical axis is less than or equal to 0.1 mm.

4. The fixed-focus lens according to claim 1, wherein: The distance between the fifth lens and the sixth lens on the optical axis is greater than or equal to 0.03 mm; A distance between the sixth lens and the seventh lens on the optical axis is greater than or equal to 0.03 mm.

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

6. 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, and the refractive index of the seventh lens is n7; 1.49≤n1≤1.62;1.49≤n2≤1.71;1.49≤n3≤1.71;1.39≤n4≤1.64; 1.49≤n5≤1.60;1.59≤n6≤1.70;1.49≤n7≤1.

60.

7. The fixed-focus lens according to claim 1, wherein: The image plane diameter of the fixed-focus lens is IC, and the total length of the fixed-focus lens is TTL; IC / TTL≥0.

3.

8. The fixed-focus lens according to claim 1, wherein: The fixed-focus lens further includes an aperture; The aperture is located in an optical path between the third lens and the fourth lens.

9. The fixed-focus lens according to claim 1, wherein: The total length of the fixed-focus lens is TTL, and TTL is ≤ 22.3 mm.

10. The fixed-focus lens according to claim 1, wherein: The aperture number of the fixed-focus lens is F, F≤1.28.

Images