Prime lens

Abstract

The utility model discloses a prime lens comprising 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 which are arranged from an object plane to an image plane along an optical axis. The first lens is a negative focal power lens, the second lens is a negative focal power lens, the third lens is a positive focal power lens, the fourth lens is a positive focal power lens, the fifth lens is a negative focal power lens, the sixth lens is a positive focal power lens, and the seventh lens is a negative focal power lens. The eighth lens is a positive focal power lens; and the third lens or the fourth lens is a glass aspheric lens. According to the technical scheme, the number of the lenses, the focal power matching mode and the surface type matching mode are reasonably set, and the design of the fixed-focus lens which is large in aperture, small in size and capable of being confocal day and night can be achieved.

Description

Technical Field

[0001] The embodiments of the utility model relate to the technical field of optical devices, and in particular to a fixed-focus lens. Background Art

[0002] To improve urban security, the security market is increasingly demanding lenses for use in key traffic arteries and public squares. Conventional lenses often suffer from small apertures, large size, and difficulty in installation, as well as poor nighttime shooting quality. To address these shortcomings of existing technology, a fixed-focus lens with a large aperture, compact size, and consistent focus, both day and night, is needed. Utility Model Content

[0003] The utility model provides a fixed-focus lens. By reasonably setting the number of lenses, the optical power matching method and the material surface shape, a fixed-focus lens design with a small volume, a large aperture and day and night confocality can be achieved.

[0004] 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, a seventh lens, and an eighth lens arranged in sequence along the optical axis from the object plane to the image plane;

[0005] The first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens, the fifth lens is a negative power lens, the sixth lens is a positive power lens, the seventh lens is a negative power lens, and the eighth lens is a positive power lens; and the third lens or the fourth lens is a glass aspherical lens.

[0006] Optionally, the third lens is a glass spherical lens, and the fourth lens is a glass aspherical lens;

[0007] Alternatively, the third lens is a glass aspherical lens, and the fourth lens is a glass spherical lens.

[0008] Optionally, the first lens includes a glass spherical lens, the second lens includes a plastic aspherical lens, the fifth lens includes a glass spherical lens, the sixth lens includes a glass spherical lens, the seventh lens includes a plastic aspherical lens, and the eighth lens includes a plastic aspherical lens.

[0009] Optionally, 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 The optical power of the eighth lens is The optical power of the fixed focus lens is

[0010] in,

[0011] Optionally, the object-side surface of the first lens is convex, and the image-side surface is concave;

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

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

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

[0015] The object-side surface of the fifth lens is concave, and the image-side surface is concave;

[0016] The object-side surface of the sixth lens is convex, and the image-side surface is convex;

[0017] The object-side surface of the seventh lens is concave, and the image-side surface is convex;

[0018] The object-side surface of the eighth lens is convex, and the image-side surface is concave.

[0019] Optionally, the fifth lens and the sixth lens are glued together;

[0020] Alternatively, the fourth lens and the fifth lens are cemented together;

[0021] Alternatively, the fourth lens, the fifth lens and the sixth lens are cemented together.

[0022] Optionally, the refractive index of the first lens is Nd1; the refractive index of the fourth lens is Nd4, and the Abbe number of the fourth lens is Vd4; the refractive index of the fifth lens is Nd5, and the Abbe number of the fifth lens is Vd5; the refractive index of the sixth lens is Nd6, and the Abbe number of the sixth lens is Vd6;

[0023] Among them, 1.73≤Nd1≤2.00; 1.43≤Nd4≤1.69; 1.80≤Nd5≤2.00; 1.43≤Nd6≤1.68; 32.21≤Vd4-Vd5≤62.05; 21.20≤Vd6-Vd5≤68.50.

[0024] Optionally, the total optical length of the fixed-focus lens is TTL;

[0025] Among them, TTL≤22.3mm.

[0026] Optionally, the aperture number of the fixed focus lens is F#;

[0027] Among them, 1.03≤F#≤1.07.

[0028] Optionally, the fixed-focus lens further includes an aperture and a filter;

[0029] The aperture is arranged in the optical path between the second lens and the third lens;

[0030] The filter is arranged in the optical path between the eighth lens and the image plane.

[0031] The fixed-focus lens provided by the embodiment of the present invention includes eight lenses with optical focal lengths, and the eight lenses are arranged in a negative-negative-positive-positive-negative-positive-negative-positive optical focal length arrangement, which is conducive to achieving a miniaturized and large-aperture fixed-focus lens arrangement. In addition, the third lens and the fourth lens are lenses in the middle part of the optical system, and the glass aspherical design of one of them can more directly affect light with a large incident angle and can more effectively correct the resulting aberrations. In addition, the glass lens has a smaller thermal expansion coefficient, making the imaging less affected by temperature changes, and 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, without causing significant aberrations or other optical problems due to temperature changes, ensuring stable imaging quality under different environmental conditions.

[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 This is a structural schematic diagram of a fixed-focus lens provided in Example 1 of the present utility model;

[0035] Figure 2 This is a schematic diagram of a spherical aberration curve of a fixed-focus lens provided in Example 1 of the present utility model;

[0036] Figure 3 This is a structural schematic diagram of a fixed-focus lens provided in Example 2 of the present utility model;

[0037] Figure 4 This is a schematic diagram of a spherical aberration curve of a fixed-focus lens provided in Example 2 of the present utility model;

[0038] Figure 5 This is a structural schematic diagram of a fixed-focus lens provided in Example 3 of the present utility model;

[0039] Figure 6 This is a schematic diagram of a spherical aberration curve of a fixed-focus lens provided in Example 3 of the present utility model;

[0040] Figure 7 This is a structural schematic diagram of a fixed-focus lens provided in Example 4 of the present utility model;

[0041] Figure 8 This is a schematic diagram of a spherical aberration curve of a fixed-focus lens provided in Example 4 of the present utility model. DETAILED DESCRIPTION

[0042] 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.

[0043] Example 1

[0044] Figure 1 This is a schematic structural diagram of a fixed-focus lens provided in the first embodiment of the present invention. Figure 1 As shown, the fixed-focus lens provided in Example 1 of the present invention includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, and an eighth lens 108, which are arranged in sequence along the optical axis from the object plane to the image plane; the first lens 101 is a negative power lens, the second lens 102 is a negative power lens, the third lens 103 is a positive power lens, the fourth lens 104 is a positive power lens, the fifth lens 105 is a negative power lens, the sixth lens 106 is a positive power lens, the seventh lens 107 is a negative power lens, and the eighth lens 108 is a positive power lens; and the third lens 103 or the fourth lens 104 is a glass aspherical lens.

[0045] Specifically, the fixed focus lens provided in the embodiment of the utility model includes eight lenses with refractive power, i.e., a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107 and an eighth lens 108, the setting mode of the eight lenses ensures that the number of lenses in the optical system is set reasonably, the number of lenses is not too large to cause the lens volume to be large, and the number of lenses is not too small to cause a single lens to bear a large refractive power and cause a large aberration, the miniaturization of the optical system is ensured, and the imaging aberration is small, and the imaging quality is high.

[0046] Further, the refractive power is equal to the difference between the converging degree of the image surface light beam and the converging degree of the object surface light beam, and it represents the ability of the optical system to deflect light. The larger the absolute value of the refractive power is, the stronger the bending ability of the light is, and the smaller the absolute value of the refractive power is, the weaker the bending ability of the light is. When the refractive power is positive, the refraction of the light is convergent; when the refractive power is negative, the refraction of the light is divergent. The refractive power can be used to represent a certain refractive surface of a lens (i.e., a surface of the lens), a certain lens, or a system (i.e., a lens group) formed by multiple lenses.

[0047] In the embodiment of the utility model, the first lens 101 and the second lens 102 are both negative refractive power lenses, the first lens 101 and the second lens 102 are used as the lenses that first adjust the incident light in the fixed focus lens, and the setting of the negative refractive power can ensure that the light has a larger aperture before entering the diaphragm, increase the aperture of the fixed focus lens, and enable the lens to still clearly image under dark or dark conditions. The third lens 103 and the fourth lens 104 are positive refractive power lenses, so that the third lens 103 and the fourth lens 104 can correct the large aberration generated by the first lens 101 and the second lens 102 in time, especially can obviously correct the edge aberration of the fixed focus lens, thereby improving the imaging resolution of the optical system. Further, the fifth lens 105 is a negative refractive power lens, the sixth lens 106 is a positive refractive power lens, the seventh lens 107 is a negative refractive power lens, and the eighth lens 108 is a positive refractive power lens, the fifth lens 105 to the eighth lens 108 adopt the negative-positive-negative-positive matching mode, the refractive power of the latter lens in the light path is different from that of the former lens, which is conducive to the correction of aberration.

[0048] Further, the third lens 103 and the fourth lens 104 are lenses as intermediate parts of the optical system, one of which is designed as a glass aspheric surface, which can more directly affect the light rays of the incident angle and can more effectively correct the aberration generated thereby; and the lens of the glass material has a smaller thermal expansion coefficient, so that the imaging is less affected by the temperature change, and the aberration and focal length drift generated by the temperature change of other lenses in the fixed focus lens can be effectively compensated, so that the fixed focus lens is not sensitive to high and low temperatures, and the influence of high and low temperatures on the entire fixed focus lens is well balanced, so that no obvious aberration or other optical problems are generated due to the temperature change, and stable imaging quality can be provided under different environmental conditions.

[0049] In summary, the fixed focus lens provided in the embodiments of the present application can realize the design of a fixed focus lens with a large aperture, a small size and day and night co-focusing by reasonably setting the number of lenses, the lens power matching mode and the material surface shape of part of the lenses.

[0050] On the basis of the above-mentioned embodiments, with reference to Figure 1 The fixed focus lens provided in the embodiments of the present application can further include a diaphragm STO and a filter 109; the diaphragm STO is arranged in the optical path between the second lens 102 and the third lens 103; and the filter 109 is arranged in the optical path between the eighth lens 108 and the image plane.

[0051] Specifically, the diaphragm STO can adjust the propagation direction of the light beam, which is beneficial to improve the imaging quality. Moreover, the diaphragm STO is arranged in the optical path between the second lens 102 and the third lens 103 in the fixed focus lens, that is, the diaphragm 104 is arranged in the optical system, which is beneficial to reduce the aperture value and realize a large aperture, and the aperture value of the system in the embodiment is F#; wherein 1.03≤F#≤1.07. The imaging requirement of the large aperture is met.

[0052] Further, the filter 109 is arranged in the optical path between the eighth lens 108 and the image plane, which is used for filtering stray light and improving the imaging effect.

[0053] Further, the fixed focus lens provided in the embodiments of the present application can further include a protective glass and an image acquisition element, the protective glass can be arranged on the image side of the filter, and the image acquisition element can be arranged on the image side of the protective glass. The optical system is protected by the protective glass, and the image acquisition element is used to acquire images, so that the normal imaging function of the optical system is realized.

[0054] On the basis of the above-mentioned embodiments, the third lens 103 can be a glass spherical lens, and the fourth lens 104 can be a glass aspheric lens; or the third lens 103 can be a glass aspheric lens, and the fourth lens 104 can be a glass spherical lens.

[0055] Specifically, spherical lenses are characterized by a constant curvature from the center to the periphery, ensuring simple lens configuration. Aspherical lenses are characterized by a continuously changing curvature from the center to the periphery. Unlike spherical lenses, which have a constant curvature from the center to the periphery, aspherical lenses have a better curvature radius, improving distortion and astigmatism. Furthermore, because glass lenses have a low coefficient of thermal expansion and excellent stability, glass spherical lenses are ideal for use in lens configurations. Glass spherical lenses offer greater thermal stability, ensuring good resolution over a wide temperature range when handling a wide range of optical powers. Furthermore, using glass aspherical lenses as third lens 103 or fourth lens 104 minimizes aberrations that occur during imaging, thereby improving image quality. Furthermore, compared to plastic aspherical lenses, glass materials offer a wider range of material options, with relatively flexible choices of refractive index and Abbe number. This allows for a certain degree of control over higher-order aberrations and chromatic aberrations, meeting the demands of complex conditions.

[0056] Based on the above embodiment, the first lens 101 includes a glass spherical lens, the second lens 102 includes a plastic aspherical lens, the fifth lens 105 includes a glass spherical lens, the sixth lens 106 includes a glass spherical lens, the seventh lens 107 includes a plastic aspherical lens, and the eighth lens 108 includes a plastic aspherical lens.

[0057] Specifically, the provision of the plastic aspheric lens is conducive to reducing the processing technology of the aspheric lens, and the cost of the aspheric lens is low, which can reduce the cost of the optical system.

[0058] Therefore, in the fixed-focus lens provided by the embodiment of the present invention, a mixed combination of glass spherical lenses, glass aspherical lenses, and plastic aspherical lenses can be used, which can effectively control the cost of the fixed-focus lens while ensuring the optical performance of the fixed-focus lens; at the same time, the materials of each lens have a mutual compensation effect, which can ensure that it can still be used normally in high and low temperature environments.

[0059] Based on the above embodiment, the optical power of the first lens 101 is The optical power of the second lens 102 is The optical power of the third lens 103 is The optical power of the fourth lens 104 is The optical power of the fifth lens 105 is The optical power of the sixth lens 106 is The optical power of the seventh lens 107 is The optical power of the eighth lens 108 is The optical power of a fixed-focus lens is in,

[0060] Specifically, the optical power of the first lens 101 is set to satisfy This helps more light enter the optical system, ensuring that the lens has a larger field of view.

[0061] Setting the optical power of the second lens 102 and the power of the third lens 103 satisfy It not only effectively shrinks light, but also helps correct system aberrations, thereby promoting the improvement of image quality; at the same time, it can reduce the total length of the system, which is conducive to the realization of miniaturized lens design.

[0062] Setting the optical power of the fourth lens 104 Refractive power of the fifth lens 105 and the refractive power of the sixth lens 106 satisfy It can correct off-axis aberrations and improve the imaging quality of the edge field of view.

[0063] Setting the optical power of the seventh lens 107 and the optical power of the eighth lens 108 satisfy It can correct off-axis aberrations, optimize the main ray angle, distortion and other performance.

[0064] Therefore, by reasonably setting the optical focal length of each lens, it is beneficial to optimize the imaging performance of the lens and improve the imaging effect.

[0065] Based on the above embodiment, the object-side surface of the first lens 101 is convex, and the image-side surface is concave; the object-side surface of the second lens 102 is concave, and the image-side surface is convex; the object-side surface of the third lens 103 is convex, and the image-side surface is convex; the object-side surface of the fourth lens 104 is convex, and the image-side surface is convex; the object-side surface of the fifth lens 105 is concave, and the image-side surface is concave; the object-side surface of the sixth lens 106 is convex, and the image-side surface is convex; the object-side surface of the seventh lens 107 is concave, and the image-side surface is convex; and the object-side surface of the eighth lens 108 is convex, and the image-side surface is concave.

[0066] Specifically, the object-side surface of the lens can be understood as the surface of the lens close to the object plane, and the image-side surface of the lens can be understood as the surface of the lens close to the image plane. The object-side surface of the first lens 101 is convex, and the image-side surface is concave. This can be understood as the object-side surface of the first lens 101 being convex toward the object plane at a position near the optical axis, and the image-side surface being concave toward the image plane at a position near the optical axis, that is, the first lens 101 is a lens with a convex-concave structure. Furthermore, the first lens 101 can be a meniscus-shaped negative lens. The surface configuration of the first lens 101, combined with the optical power parameters of the first lens 101, can focus as much light of a large field of view as possible into the system, which is beneficial to improving the field of view angle of the optical system.

[0067] The object-side surface of the second lens element 102 is concave, and the image-side surface is convex. This means that the object-side surface of the second lens element 102 is concave toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the second lens element 102 has a concave-convex structure. The concave-convex negative design of the second lens element 102 effectively controls the trajectory of light, reduces field curvature and spherical aberration of the optical system, and improves image quality.

[0068] The object-side surface and image-side surface of the third lens 103 are convex, which can be understood as the object-side surface of the third lens 103 convex toward the object plane at a position near the optical axis, and the image-side surface convex toward the image plane at a position near the optical axis, that is, the third lens 103 is a lens with a biconvex structure. The object-side surface and image-side surface of the fourth lens 104 are convex, which can be understood as the object-side surface and image-side surface of the fourth lens 104 convex toward the object plane at a position near the optical axis, and the image-side surface convex toward the image plane at a position near the optical axis, that is, the fourth lens 140 is a lens with a biconvex structure. Both the third lens 103 and the fourth lens 104 have biconvex structures. Combined with the optical power parameters of the third lens 103 and the fourth lens 104 and their placement in the optical system, they can effectively narrow light, reduce the overall length of the optical system, and facilitate miniaturized lens design.

[0069] The object-side surface and image-side surface of the fifth lens element 105 are concave, which can be understood as the object-side surface of the fifth lens element 105 being concave toward the object plane near the optical axis, and the image-side surface being concave toward the image plane near the optical axis, that is, the fifth lens element 105 is a lens with a biconcave structure. The object-side surface and image-side surface of the sixth lens element 106 are convex, which can be understood as the object-side surface of the sixth lens element 106 being convex toward the object plane near the optical axis, and the image-side surface being convex toward the image plane near the optical axis, that is, the sixth lens element 106 is a lens with a biconvex structure. The configuration of the surface of the fifth and sixth lenses 105, 106, combined with the optical power parameters of the fifth and sixth lenses 105, 106, can further correct off-axis aberrations and improve imaging quality in the peripheral field of view.

[0070] The object-side surface of the seventh lens element 107 is concave, and the image-side surface is convex. This means that the object-side surface of the seventh lens element 107 is concave toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the seventh lens element 107 has a concave-convex structure. The object-side surface of the eighth lens element 108 is convex, and the image-side surface is concave. This means that the object-side surface of the eighth lens element 108 is convex toward the object plane near the optical axis, while the image-side surface is concave toward the image plane near the optical axis. In other words, the eighth lens element 108 has a concave-convex structure. This distribution of the shapes of the seventh and eighth lenses 107 and 108 is beneficial for correcting field curvature of the system.

[0071] In summary, by reasonably setting the concave and convex surface shapes of each lens, it is beneficial to correct spherical aberration, aberration and field curvature, and improve the imaging effect.

[0072] Based on the above embodiment, the fifth lens 105 and the sixth lens 106 are cemented together; or the fourth lens 104 and the fifth lens 105 are cemented together; or the fourth lens 104, the fifth lens 105 and the sixth lens 106 are cemented together.

[0073] The cemented arrangement of the fifth lens 105 and the sixth lens 106 can be understood as the image-side surface of the fifth lens 105 being bonded to the object-side surface of the sixth lens 106. In other words, the image-side surface of the fifth lens 105 is bonded to the object-side surface of the sixth lens 106. By cementing the fifth and sixth lenses 105, 106, the air gap between them can be reduced, helping to shorten the overall optical length of the lens. It also reduces sensitivity to tolerances such as tilt and deflection during lens unit assembly, simplifying the assembly process and improving equipment efficiency. Furthermore, cementing the fifth and sixth lenses 105, 106 reduces light loss caused by inter-lens reflections, improving illumination and reducing the risk of ghosting. Cemented lenses can also minimize or eliminate chromatic aberration. Using cemented lenses in fixed-focus lenses can improve image quality and reduce light energy loss due to reflection, thereby enhancing image quality and clarity. Furthermore, the fifth lens 105 and the sixth lens 106 may be supported by a spacer, or may be bonded together by glue. The embodiment of the present utility model does not limit the specific bonding method.

[0074] Similarly, the cemented arrangement of the fourth lens 104 and the fifth lens 105 can be understood as the image-side surface of the fourth lens 104 being bonded to the object-side surface of the fifth lens 105, that is, the image-side surface of the fourth lens 104 is bonded to the object-side surface of the fifth lens 105. By cementing the fourth and fifth lenses 104, 105, the air gap between them can be reduced, helping to shorten the overall optical length of the lens. It also reduces sensitivity to tolerances such as tilt and deflection during lens unit assembly, simplifying the assembly process and improving equipment efficiency. Furthermore, cementing the fourth and fifth lenses 104, 105 reduces light loss caused by inter-lens reflections, improving illumination and reducing the risk of ghosting. Cemented lenses can also minimize or eliminate chromatic aberration. Using cemented lenses in fixed-focus lenses can improve image quality and reduce light energy loss due to reflection, thereby enhancing image quality and clarity. Furthermore, the fourth lens 104 and the fifth lens 105 may be supported by a spacer, or may be bonded together by glue. The embodiment of the present utility model does not limit the specific bonding method.

[0075] Similarly, the cemented arrangement of the fourth lens 104, the fifth lens 105, and the sixth lens 106 is understood to mean that the image-side surface of the fourth lens 104 is bonded to the object-side surface of the fifth lens 105, and the image-side surface of the fifth lens 105 is bonded to the object-side surface of the sixth lens 106. In other words, the image-side surface of the fourth lens 104 is bonded to the object-side surface of the fifth lens 105, and the image-side surface of the fifth lens 105 is bonded to the object-side surface of the sixth lens 106. By cementing the fourth, fifth, and sixth lenses 104, 105, and 106 to form a cemented triplet, the air gap between the fourth and fifth lenses 104, 105, and the air gap between the fifth and sixth lenses 105, 106 can be reduced, thereby reducing the overall optical length of the lens. It can also reduce tolerance sensitivity issues such as tilt and deflection that arise during lens unit assembly, simplify the assembly process during lens manufacturing, and improve equipment efficiency. The cemented arrangement of the fourth lens element 104, the fifth lens element 105, and the sixth lens element 106 can also reduce light loss caused by reflection between the lenses, improving illumination and reducing the risk of ghosting. Furthermore, cemented lenses can be used to minimize or eliminate chromatic aberration. Using cemented lenses in fixed-focus lenses can improve image quality and reduce light energy loss due to reflection, thereby improving image quality and enhancing lens image clarity. Furthermore, the fourth lens element 104, the fifth lens element 105, and the sixth lens element 106 can be supported by spacers or bonded together using glue. The present invention does not limit the specific bonding method.

[0076] It should be noted that Figure 1 In the structure of the fixed-focus lens shown, the fifth lens 105 and the sixth lens 106 are cemented together. In subsequent embodiments, the cemented arrangement of the fourth lens 104 and the fifth lens 105, as well as the cemented arrangement of the fourth lens 104, the fifth lens 105 and the sixth lens 106 will be described.

[0077] Based on the above embodiment, the refractive index of the first lens 101 is Nd1; the refractive index of the fourth lens 104 is Nd4, and the Abbe number of the fourth lens 104 is Vd4; the refractive index of the fifth lens 105 is Nd5, and the Abbe number of the fifth lens 105 is Vd5; the refractive index of the sixth lens 106 is Nd6, and the Abbe number of the sixth lens 106 is Vd6. Among them, 1.73≤Nd1≤2.00; 1.43≤Nd4≤1.69; 1.80≤Nd5≤2.00; 1.43≤Nd6≤1.68; 32.21≤Vd4-Vd5≤62.05; and 21.20≤Vd6-Vd5≤68.50.

[0078] Specifically, the first lens 101 is made of a high-refractive-index material satisfying 1.73≤Nd1≤2.00. This effectively deflects light, ensuring more light enters the optical system and a wider field of view. The fourth, fifth, and sixth lenses 104, 105, and 106 utilize a combination of materials with different dispersion coefficients and refractive indices. The refractive indices and Abbe numbers of these three lenses satisfy 1.43≤Nd4≤1.69; 1.80≤Nd5≤2.00; 1.43≤Nd6≤1.68; 32.21≤Vd4-Vd5≤62.05; and 21.20≤Vd6-Vd5≤68.50. This allows for dispersion compensation to achieve achromatic aberration, improving the imaging performance of the optical system and achieving day-and-night confocality.

[0079] Furthermore, the total optical length of the fixed-focus lens is TTL; wherein TTL≤22.3mm, meeting the design requirement of a shorter total optical length.

[0080] As a feasible implementation method, the specific parameters of the fixed-focus lens are described below.

[0081] Table 1 Optical design values ​​of the fixed-focus lens in Example 1

[0082]

[0083]

[0084] Table 2 Design values ​​of optical physical parameters of a fixed-focus lens

[0085]

[0086] The surface numbers in Table 2 are numbered according to the order of the surfaces of each lens. "S1" represents the object-side surface of the first lens, "S2" represents the image-side surface of the first lens, "STO" represents the aperture of the fixed-focus lens, and "IMA" represents the image surface of the fixed-focus lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved toward the image side, and a negative value indicates that the surface is curved toward the object side. "Infinity" indicates that the surface is flat, the radius of curvature is infinite, and the distance is infinite. The thickness represents the central axial distance from the current surface to the next surface. The refractive index Nd represents the light deflection ability of the material between the current surface and the next surface. A blank space represents the current position is air with a refractive index of 1. The Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface. A blank space represents the current position is air. The semi-diameter represents the effective diameter of the lens light. The k value represents the numerical value of the conic coefficient of the aspheric surface.

[0087] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0088]

[0089] Where z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the reciprocal of the radius of curvature; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0090] Table 3 Aspheric coefficients of a fixed-focus lens

[0091]

[0092] Among them, "5.382239E-03" means 5.382239*10 -3 , and the remaining coefficients all use this representation method.

[0093] Based on the above parameter limitations, the optical parameters that can be achieved by the fixed-focus lens in Example 1 of the present invention are as follows:

[0094] Focal length F#: 1.04.

[0095] Ф7.6mm corresponds to an angle of 152.3°.

[0096] Figure 2This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Example 1 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 2 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), 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.

[0097] In summary, the fixed-focus lens provided in Example 1 of the present invention includes eight lenses with optical power. By rationally setting the optical power distribution method, optical power parameters, material surface shape, concave-convex condition, bonding condition, as well as parameters such as refractive index and Abbe number, a fixed-focus lens with a large aperture, small size, and day and night confocality is designed.

[0098] Example 2

[0099] Figure 3 This is a schematic structural diagram of a fixed-focus lens provided in the second embodiment of the present invention. Figure 3 As shown, the fixed-focus lens provided in Example 2 of the present invention includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, and an eighth lens 108, which are arranged in sequence along the optical axis from the object plane to the image plane; the first lens 101 is a negative power lens, the second lens 102 is a negative power lens, the third lens 103 is a positive power lens, the fourth lens 104 is a positive power lens, the fifth lens 105 is a negative power lens, the sixth lens 106 is a positive power lens, the seventh lens 107 is a negative power lens, and the eighth lens 108 is a positive power lens; and the third lens 103 or the fourth lens 104 is a glass aspherical lens.

[0100] The configuration of the lens is the same as that in the first embodiment, and will not be described again here.

[0101] The difference from the first embodiment is that in the solution of the second embodiment, each lens is independently provided and there is no gluing.

[0102] As another feasible implementation, specific parameters of the fixed-focus lens are described below.

[0103] Table 4 Optical design values ​​of the fixed-focus lens in Example 2

[0104]

[0105] Table 5: Design values of optical physical parameters of a fixed focus lens

[0106]

[0107]

[0108] The surface number in Table 5 is numbered according to the surface order of each lens, "S1" represents the object side surface of the first lens, "S2" represents the image side surface of the first lens, "STO" represents the diaphragm of the fixed focus lens; "IMA" represents the image surface of the fixed focus lens; the radius of curvature represents the bending degree of the lens surface, the positive value represents that the surface is bent to the image side, and the negative value represents that the surface is bent to the object side; wherein "Infinity" represents that the surface is a plane, the radius of curvature is infinite, and the distance is infinite; the thickness represents the center axis distance from the current surface to the next surface; the refractive index Nd represents the deflection ability of the material between the current surface and the next surface to the light, and the space represents that the current position is air, and the refractive index is 1. The Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface to the light, and the space represents that the current position is air; the semi-diameter represents the effective diameter of the light of the lens; the k value represents the numerical size of the conic coefficient of the aspheric surface.

[0109] The aspheric conic coefficient can be defined by the following aspheric formula, but is not limited to the following representation method:

[0110]

[0111] Wherein, z is the axial height of the aspheric Z direction; r is the height of the aspheric surface; c is the curvature of the fitting sphere, which is the reciprocal of the radius of curvature in value; k is the fitting conic coefficient; A-G are 4th order, 6th order, 8th order, 10th order, 12th order, 14th order and 16th order term coefficients of the aspheric polynomial.

[0112] Table 6: Aspheric surface coefficients of a fixed focus lens

[0113]

[0114] Wherein, "5.884696E-03" represents 5.884696*10 -3 The remaining coefficients are represented in this manner.

[0115] Based on the above parameter definition, the optical parameters that can be realized by the fixed focus lens in the second embodiment of the utility model are as follows:

[0116] Focal length F#: 1.07.

[0117] Corresponding angle of φ7.6mm: 152.8°.

[0118] Figure 4 This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Example 2 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 4 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), 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.

[0119] In summary, the fixed-focus lens provided in Example 2 of the present invention includes eight lenses with optical power. By rationally setting the optical power distribution method, optical power parameters, material surface shape, concave-convex condition, bonding condition, as well as parameters such as refractive index and Abbe number, a fixed-focus lens with a large aperture, small size, and day and night confocality is designed.

[0120] Example 3

[0121] Figure 5 This is a schematic structural diagram of a fixed-focus lens provided in the third embodiment of the present invention. Figure 5 As shown, the fixed-focus lens provided in Example 3 of the present invention includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, and an eighth lens 108, which are arranged in sequence along the optical axis from the object plane to the image plane; the first lens 101 is a negative power lens, the second lens 102 is a negative power lens, the third lens 103 is a positive power lens, the fourth lens 104 is a positive power lens, the fifth lens 105 is a negative power lens, the sixth lens 106 is a positive power lens, the seventh lens 107 is a negative power lens, and the eighth lens 108 is a positive power lens; and the third lens 103 or the fourth lens 104 is a glass aspherical lens.

[0122] The configuration of the lens is the same as that in the first embodiment, and will not be described again here.

[0123] The difference from the above is that, in the solution of the third embodiment, the fourth lens 104 and the fifth lens 105 are glued together.

[0124] As another feasible implementation, specific parameters of the fixed-focus lens are described below.

[0125] Table 7 Optical design values ​​of the fixed-focus lens in Example 3

[0126]

[0127]

[0128] Table 8 Design values ​​of optical physical parameters of a fixed-focus lens

[0129]

[0130] The surface numbers in Table 8 are numbered according to the order of the surfaces of each lens. "S1" represents the object surface of the first lens, "S2" represents the image surface of the first lens, and "STO" represents the fixed focus lens.

[0131] The aperture of the lens; "IMA" represents the image plane of the fixed-focus lens; the radius of curvature represents the degree of curvature of the lens surface, with a positive value indicating that the surface is curved toward the image plane and a negative value indicating that the surface is curved toward the object plane; "Infinity" represents that the surface is flat, the radius of curvature is infinite, and the distance is infinite; the thickness represents the central axial distance from the current surface to the next surface; the refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light, and a blank space represents that the current position is air with a refractive index of 1. The Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface, and a blank space represents that the current position is air; the semi-diameter represents the effective diameter of the lens light; the k value represents the numerical value of the conic coefficient of the aspheric surface.

[0132] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0133]

[0134] Wherein, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0135] Table 9 Aspheric coefficients of a fixed-focus lens

[0136]

[0137]

[0138] Among them, "5.440741E-03" means 5.440741*10 -3 , and the remaining coefficients all use this representation method.

[0139] Based on the above parameter limitations, the optical parameters that can be achieved by the fixed-focus lens in Example 3 of the present invention are as follows:

[0140] Focal length F#: 1.05.

[0141] Ф7.6mm corresponds to an angle of 152.3°.

[0142] Figure 6 This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided in Example 3 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 6 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), 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.

[0143] In summary, the fixed-focus lens provided in Example 3 of the present invention includes eight lenses with optical power. By reasonably setting the optical power distribution method, optical power parameters, material surface shape, concave-convex condition, bonding condition, as well as parameters such as refractive index and Abbe number, the design of a fixed-focus lens with a large aperture, small size, and day and night confocality is achieved.

[0144] Example 4

[0145] Figure 7 This is a structural diagram of a fixed-focus lens provided by the fourth embodiment of the present invention. Figure 7 As shown, the fixed-focus lens provided in Example 4 of the present invention includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107 and an eighth lens 108, which are arranged in sequence along the optical axis from the object plane to the image plane; the first lens 101 is a negative power lens, the second lens 102 is a negative power lens, the third lens 103 is a positive power lens, the fourth lens 104 is a positive power lens, the fifth lens 105 is a negative power lens, the sixth lens 106 is a positive power lens, the seventh lens 107 is a negative power lens, and the eighth lens 108 is a positive power lens; and the third lens 103 or the fourth lens 104 is a glass aspherical lens.

[0146] The configuration of the lens is the same as that in the first embodiment, and will not be described again here.

[0147] The difference from the above is that, in the solution of the fourth embodiment, the fourth lens 104, the fifth lens 105 and the sixth lens 106 are cemented together.

[0148] As another feasible implementation, specific parameters of the fixed-focus lens are described below.

[0149] Table 10: Optical design values ​​of the fixed-focus lens in Example 4

[0150]

[0151] Table 11 Design values ​​of optical physical parameters of a fixed-focus lens

[0152]

[0153]

[0154] The surface numbers in Table 11 are numbered according to the order of the surfaces of each lens. "S1" represents the object-side surface of the first lens, "S2" represents the image-side surface of the first lens, "STO" represents the aperture of the fixed-focus lens, and "IMA" represents the image surface of the fixed-focus lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface is curved toward the image side, and a negative value represents that the surface is curved toward the object side. "Infinity" represents that the surface is flat, the radius of curvature is infinite, and the distance is infinite. The thickness represents the central axial distance from the current surface to the next surface. The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. A blank space represents that the current position is air with a refractive index of 1. The Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface. A blank space represents that the current position is air. The semi-diameter represents the effective diameter of the lens light. The k value represents the numerical value of the conic coefficient of the aspheric surface.

[0155] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0156]

[0157] Wherein, z is the axial sagittal height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0158] Table 12 Aspheric coefficients of a fixed-focus lens

[0159]

[0160] Among them, "4.437042E-03" means 4.437042*10 -3 , and the remaining coefficients all use this representation method.

[0161] Based on the above parameter limitations, the optical parameters that can be achieved by the fixed-focus lens in the fourth embodiment of the present invention are as follows:

[0162] Focal length F#: 1.03.

[0163] Ф7.6mm corresponds to an angle of 152.5°.

[0164] Figure 8 This is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided by Example 4 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 8 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), 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.

[0165] In summary, the fixed-focus lens provided in Example 4 of the present invention includes eight lenses with optical power. By reasonably setting the optical power distribution method, optical power parameters, material surface shape, concave-convex condition, bonding condition, as well as parameters such as refractive index and Abbe number, the design of a fixed-focus lens with a large aperture, small size, and day and night confocality is achieved.

[0166] The above specific embodiments do not limit the scope of protection of this utility model. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model shall be included within the scope of protection of this utility model.

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, a seventh lens and an eighth lens arranged in sequence along the optical axis from the object plane to the image plane; The first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens, the fifth lens is a negative power lens, the sixth lens is a positive power lens, the seventh lens is a negative power lens, and the eighth lens is a positive power lens; and the third lens or the fourth lens is a glass aspherical lens.

2. The fixed-focus lens according to claim 1, wherein: The third lens is a glass spherical lens, and the fourth lens is a glass aspherical lens; Alternatively, the third lens is a glass aspherical lens, and the fourth lens is a glass spherical lens.

3. The fixed-focus lens according to claim 2, wherein: The first lens includes a glass spherical lens, the second lens includes a plastic aspherical lens, the fifth lens includes a glass spherical lens, the sixth lens includes a glass spherical lens, the seventh lens includes a plastic aspherical lens, and the eighth lens includes a plastic aspherical lens.

4. The fixed-focus lens according to claim 1, wherein: 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 The optical power of the eighth lens is The optical power of the fixed focus lens is in, 5. 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 convex, 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 concave, and the image-side surface is concave; The object-side surface of the sixth lens is convex, and the image-side surface is convex; The object-side surface of the seventh lens is concave, and the image-side surface is convex; The object-side surface of the eighth lens is convex, and the image-side surface is concave.

6. The fixed-focus lens according to claim 5, wherein: The fifth lens and the sixth lens are glued together; Alternatively, the fourth lens and the fifth lens are cemented together; Alternatively, the fourth lens, the fifth lens and the sixth lens are cemented together.

7. The fixed-focus lens according to claim 1, wherein: The refractive index of the first lens is Nd1; the refractive index of the fourth lens is Nd4, and the Abbe number of the fourth lens is Vd4; the refractive index of the fifth lens is Nd5, and the Abbe number of the fifth lens is Vd5; the refractive index of the sixth lens is Nd6, and the Abbe number of the sixth lens is Vd6; Among them, 1.73≤Nd1≤2.00; 1.43≤Nd4≤1.69; 1.80≤Nd5≤2.00; 1.43≤Nd6≤1.68; 32.21≤Vd4-Vd5≤62.05; 21.20≤Vd6-Vd5≤68.

50.

8. The fixed-focus lens according to claim 1, wherein: The total optical length of the fixed-focus lens is TTL; Among them, TTL≤22.3mm.

9. The fixed-focus lens according to claim 1, wherein: The aperture number of the fixed focus lens is F#; Among them, 1.03≤F#≤1.

07.

10. The fixed-focus lens according to claim 1, wherein: The fixed-focus lens further includes an aperture and a filter; The aperture is arranged in the optical path between the second lens and the third lens; The filter is arranged in the optical path between the eighth lens and the image plane.

Images