Low-light-level lens

Abstract

The invention discloses a low-light-level lens, which comprises a first lens group with positive focal power and a second lens group with positive focal power, and is characterized in that the first lens group comprises a first lens with negative focal power, a second lens with negative focal power and a third lens with positive focal power; the second lens group comprises a fourth lens with positive focal power, a fifth lens with negative focal power, a sixth lens with positive focal power, a seventh lens with positive focal power, an eighth lens with negative focal power and a ninth lens with positive focal power; the combined focal power of the fourth lens, the fifth lens and the sixth lens is phi 456, the combined focal power of the seventh lens, the eighth lens and the ninth lens is phi 789, and the focal power of the low-light-level lens is phi; wherein 0.245 < phi 456 / phi < = 0.425, and 0.245 < = phi 789 / phi < = 0.385. According to the technical scheme, the number of the lens groups, the number of the lenses, the focal power matching mode of the lens groups, the focal power matching mode of the lenses and specific values in the low-light-level lens are reasonably set, so that the design of the low-light-level lens with a large aperture can be realized.

Description

Technical Field

[0001] The present invention relates to the field of optical device technology, and in particular to a low-light lens. Background Technology

[0002] With the rapid development of technology, the requirements for optical lenses are becoming increasingly stringent. Currently available lenses can reach a maximum aperture of around Fno1.0, and their imaging performance is adequate for common low-light environments. However, their light transmission capability remains unsatisfactory for scenes with extremely low ambient light. To achieve higher pixel counts and more powerful low-light imaging, research into imaging lenses with larger apertures and higher resolution has become a new hot topic. Currently, a few lenses can reach an aperture of Fno0.85, but their overall length is generally over 60mm, and their applications are typically in the infrared field. For security monitoring, such lenses are not practically useful.

[0003] Currently, some security monitoring lenses on the market have an aperture of Fno0.85, and their focal lengths are generally equivalent to 2.8mm and 4.0mm. Security monitoring lenses with an equivalent focal length of 6.0mm, an aperture of Fno0.85, and a smaller overall length are less common. Summary of the Invention

[0004] This invention provides a low-light lens system that achieves an equivalent focal length of 6.0mm, an aperture of Fno0.85, a total length TTL of less than 51.0mm, and an imaging range that can be matched with a 1 / 1.8-inch chip.

[0005] This invention provides a low-light lens, comprising a first lens group and a second lens group arranged sequentially along the optical axis from the object plane to the image plane; The first lens group has a positive optical power and includes a first lens with negative optical power, a second lens with negative optical power, and a third lens with positive optical power. The second lens group has positive optical power, and the second lens group includes a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, and a ninth lens with positive optical power; the low-light lens has nine lenses with optical power. The combined optical power of the fourth lens, the fifth lens, and the sixth lens is φ456; the combined optical power of the seventh lens, the eighth lens, and the ninth lens is φ789; and the optical power of the low-light lens is φ. Among them, 0.245<φ456 / φ≤0.425, 0.245≤φ789 / φ≤0.385.

[0006] Optionally, the first lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses; The second lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses.

[0007] Optionally, the first lens includes a first object-side surface near the object plane and a first image-side surface near the image plane, wherein the first object-side surface is a plane and the first image-side surface is a concave surface. The second lens includes a second object-side surface near the object plane and a second image-side surface near the image plane. The second object-side surface is concave, and the second image-side surface is convex. The third lens includes a third object-side surface near the object plane and a third image-side surface near the image plane. The third object-side surface is convex, and the third image-side surface is convex. The fourth lens includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane. The fourth object-side surface is convex, and the fourth image-side surface is convex. The fifth lens includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane. The fifth object-side surface is concave, and the fifth image-side surface is concave. The sixth lens includes a sixth object-side surface near the object plane and a sixth image-side surface near the image plane. The sixth object-side surface is convex, and the sixth image-side surface is convex. The seventh lens includes a seventh object-side surface near the object plane and a seventh image-side surface near the image plane. The seventh object-side surface is a hyperboloid and is convex at the paraxial position, and the seventh image-side surface is a hyperboloid and is concave at the paraxial position. The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane. The eighth object-side surface is concave, and the eighth image-side surface is convex. The ninth lens includes a ninth object-side surface near the object plane and a ninth image-side surface near the image plane. The ninth object-side surface is convex, and the ninth image-side surface is concave.

[0008] Optionally, the optical power of the first lens group is φA, the optical power of the second lens group is φB, and the optical power of the low-light lens is φ; Among them, 0.065≤φA / φ≤0.185, 0.435≤φB / φ≤0.525.

[0009] Optionally, the optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the seventh lens is φ7, the optical power of the eighth lens is φ8, the optical power of the ninth lens is φ9, and the optical power of the low-light lens is φ. Among them, -0.645≤φ1 / φ≤0.485, -0.205<φ2 / φ≤-0.125, 0.345≤φ3 / φ≤0.445, 0.005≤φ7 / φ≤0.065, -0.055<φ8 / φ≤-0.005, and 0.205≤φ9 / φ≤0.365.

[0010] Optionally, the fourth lens, the fifth lens, and the sixth lens are cemented together.

[0011] Optionally, the center thickness of the fourth lens, the fifth lens, and the sixth lens is d456; Wherein, 0.455≤φ456 / d456≤0.685.

[0012] Optionally, the distance between the center of the image side of the second lens and the center of the object side of the third lens is d23, the distance between the center of the image side of the third lens and the center of the object side of the fourth lens is d34, and the sum of the center thicknesses of the second lens and the third lens is t23. Among them, 0.385≤(d23+d34) / t23≤0.645.

[0013] Optionally, the total optical length of the low-light lens is TTL, and the effective focal length is F; Wherein, 0.158≤F / TTL≤0.168.

[0014] Optionally, the optical back focal length of the low-light lens is BFL, and the total optical length is TTL; Wherein, 0.085≤BFL / TTL≤0.135.

[0015] The low-light lens provided in this embodiment of the invention includes two lens groups, both of which have positive optical power. The low-light lens further includes nine lenses with optical power, designed in a negative-negative-positive-positive-negative-positive-positive-negative-positive optical power configuration. By setting the optical lens to include two lens groups with optical power and nine lenses with optical power, and by reasonably setting the number of lens groups, the number of lenses, the optical power of the lens groups, and the optical power of the lenses, the overall length of the optical lens can be ensured to be appropriate. This achieves a relatively miniaturized design while maintaining small imaging aberrations and high image quality. Furthermore, by reasonably matching the optical power ratio between the middle and rear lens groups, the aperture of the optical lens can be increased, further improving the imaging resolution.

[0016] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a low-light lens provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of axial aberration of a low-light lens provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the light fan of a low-light lens provided in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of field curvature distortion of a low-light lens provided in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the structure of a low-light lens provided in Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of axial aberration of a low-light lens provided in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the light fan of a low-light lens provided in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of field curvature distortion of a low-light lens provided in Embodiment 2 of the present invention; Figure 9This is a schematic diagram of the structure of a low-light lens provided in Embodiment 3 of the present invention; Figure 10 This is a schematic diagram of axial aberration of a low-light lens provided in Embodiment 3 of the present invention; Figure 11 This is a schematic diagram of the light fan of a low-light lens provided in Embodiment 3 of the present invention; Figure 12 This is a schematic diagram of field curvature distortion of a low-light lens provided in Embodiment 3 of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] Example 1 Figure 1 This is a schematic diagram of the structure of a low-light lens provided in Embodiment 1 of the present invention, as shown below. Figure 1 As shown, the low-light lens provided in this embodiment of the invention includes a first lens group S1 and a second lens group S2 arranged sequentially along the optical axis from the object plane to the image plane. The first lens group S1 has a positive optical power and includes a first lens 101 with negative optical power, a second lens 102 with negative optical power, and a third lens 103 with positive optical power. The second lens group S2 has a positive optical power and includes a fourth lens 104 with positive optical power, a fifth lens 105 with negative optical power, a sixth lens 106 with positive optical power, and a third lens 103 with positive optical power. The lens comprises a seventh lens 107 with negative optical power, an eighth lens 108 with negative optical power, and a ninth lens 109 with positive optical power; the low-light lens has nine lenses with optical power; the combined optical power of the fourth lens 104, the fifth lens 105, and the sixth lens 106 is φ456, the combined optical power of the seventh lens 107, the eighth lens 108, and the ninth lens 109 is φ789, and the optical power of the low-light lens is φ; wherein, 0.245 < φ456 / φ ≤ 0.425, and 0.245 ≤ φ789 / φ ≤ 0.385.

[0021] The low-light lens provided in this application embodiment includes a first lens group S1 and a second lens group S2. Further, the first lens group S1 includes a first lens 101, a second lens 102 and a third lens 103; the second lens group S2 includes a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, an eighth lens 108 and a ninth lens 109. That is, the optical lens has nine lenses with optical power. The arrangement of nine lenses ensures that the number of lenses in the optical system is reasonable. Too many lenses will result in a large lens size, and too few lenses will result in large aberrations due to a single lens bearing a large optical power. This ensures that the optical system is miniaturized while ensuring small imaging aberrations and high imaging quality.

[0022] Furthermore, optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light rays. The larger the absolute value of the optical power, the stronger its ability to bend light rays; the smaller the absolute value, the weaker its ability to bend light rays. When the optical power is positive, the refraction of light rays is converging; when the optical power is negative, the refraction of light rays is diverging.

[0023] In this embodiment of the invention, the first lens 101 and the second lens 102 in the first lens group S1 are both negative power lenses. As the first lenses in the optical lens to adjust the incident light, their negative power ensures that the light has a larger aperture before entering the aperture stop, increasing the aperture of the optical lens and enabling the lens to still produce clear images under dim or dark conditions. The positive power third lens 103 can promptly correct the large aberrations produced by the first lens 101 and the second lens 102, especially significantly correcting edge aberrations of the optical lens, thereby improving the imaging resolution of the optical system. In summary, the first lens group S1 adopts a positive power design and further employs a negative-negative-positive three-lens power design, which can effectively gather the incident light, reduce the angle of incidence, correct spherical aberration, coma, and other on-axis and paraxial aberrations, and also helps to reduce the overall length of the lens.

[0024] Furthermore, such as Figure 1 As shown, the low-light lens in this embodiment may also include an aperture stop STO. By setting the aperture stop STO, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality. Furthermore, the aperture stop STO can be located between the third lens 103 and the fourth lens 104, effectively ensuring that the aperture number of the low-light lens is less than 0.85, thus achieving a low-light lens design with large aperture performance.

[0025] Based on this, the fourth lens 104, the fifth lens 105, and the sixth lens 106, serving as the lenses after the STO aperture and as the lenses in the middle section of the low-light lens, primarily undertake the tasks of power distribution and aberration correction. By setting the power of the fourth lens 104, the fifth lens 105, and the sixth lens 106 in a positive-negative-positive configuration, spherical aberration and coma can be balanced; and light of different wavelengths can be effectively separated and reconverged, reducing axial chromatic aberration, making the low-light image clearer and sharper, and reducing purple or green fringing. Furthermore, by setting the combined power φ456 of the fourth lens 104, the fifth lens 105, and the sixth lens 106 to satisfy 0.245 < φ456 / φ ≤ 0.425 with the power φ of the low-light lens, it can be ensured that light passing through the fourth lens 104, the fifth lens 105, and the sixth lens 106 will not produce excessive spherical aberration, while effectively correcting the coma generated by the preceding lenses. Furthermore, by controlling the optical power to meet the above limitations, the light can pass more smoothly through the fourth lens 104, the fifth lens 105, and the sixth lens 106, avoiding abrupt changes in the angle of light, thereby reducing reflection loss on the lens surface and improving the light utilization rate in low-light environments.

[0026] Furthermore, the seventh lens 107, the eighth lens 108, and the ninth lens 109 are located adjacent to the imaging plane, directly determining how light converges at the edge of the imaging plane. By setting the optical power of the seventh lens 107, the eighth lens 108, and the ninth lens 109 in a positive-negative-positive configuration, it can be ensured that edge light rays are incident on the sensor at a smaller angle (i.e., meeting the CRA, the requirement of the principal ray angle). This is crucial for large-area, high-pixel sensors, significantly improving vignetting and blurring issues at the image edges. Moreover, by setting the combined optical power φ789 of the seventh lens 107, the eighth lens 108, and the ninth lens 109 to satisfy 0.245≤φ789 / φ≤0.385 with the optical power φ of the low-light lens, the optical power can be reasonably distributed across these three lenses, reducing the burden on individual lenses and thus improving the lens yield and assembly tolerance.

[0027] In summary, the combined optical power φ456 of the fourth lens 104, the fifth lens 105, and the sixth lens 106 is limited to satisfying 0.245 < φ456 / φ ≤ 0.425 with respect to the optical power φ of the low-light lens, and the combined optical power φ789 of the seventh lens 107, the eighth lens 108, and the ninth lens 109 is limited to satisfying 0.245 ≤ φ789 / φ ≤ 0.385 with respect to the optical power φ of the low-light lens. By setting a reasonable distribution of optical power in the middle and rear sections of the lens, high imaging quality at the center and edges can be achieved while ensuring the overall length of the lens (miniaturization), and the lens can maintain high contrast and high clarity in low-light environments.

[0028] Furthermore, the low-light lens provided in this embodiment of the invention may also include a filter 110, a protective glass, and an imaging sensor (not shown in the figure). The filter 110 is disposed in the optical path between the ninth lens 109 and the image plane. The protective glass may be disposed on the image-side side of the filter, and the imaging sensor may be disposed on the image-side side of the protective glass. The filter 110 can filter out stray spectra to ensure image quality. The protective glass protects the optical system, and the imaging sensor acquires images to realize the normal imaging function of the optical system.

[0029] In summary, the optical system provided by this invention, by setting the optical lens to include two lens groups with optical power and nine lenses with optical power, and by reasonably setting the number of lens groups, the number of lenses, the optical power of the lens groups, and the optical power of the lenses, can ensure that the total length of the optical lens is appropriate, achieving a relatively miniaturized design while ensuring small imaging aberrations and high image quality. Furthermore, the optical power of the nine lenses is arranged in a negative-negative-positive-positive-negative-positive-positive-negative-positive configuration. By reasonably matching the optical power design of the nine lenses and the ratio of optical power between the middle and rear lens groups, the aperture of the optical lens can be increased, further improving the imaging resolution of the optical lens.

[0030] Based on the above embodiments, the first lens 101, the third lens 1003, the fourth lens 104, the fifth lens 105, and the sixth lens 106 are all glass spherical lenses; the second lens 102, the seventh lens 107, the eighth lens 108, and the ninth lens 109 are all plastic aspherical lenses.

[0031] Specifically, spherical lenses are characterized by a constant curvature from the center to the periphery, ensuring a simple lens setup. Furthermore, due to the low coefficient of thermal expansion and good stability of glass lenses, the first lens 101, third lens 103, fourth lens 104, fifth lens 105, and sixth lens 106 are all glass spherical lenses. The thermal properties of glass spherical lenses are more stable, ensuring good resolving power over a wide temperature range when handling higher optical powers. Moreover, the range of glass materials available is wider, and the refractive index and Abbe number can be chosen more freely, allowing for better control of higher aberrations and chromatic aberration, meeting the needs of use under complex conditions.

[0032] Aspherical lenses are characterized by a continuous change in curvature from the center to the periphery, unlike spherical lenses which have a constant curvature. Aspherical lenses offer superior radius of curvature characteristics, improving both distortion and astigmatism. Furthermore, due to the relatively low price of plastic, using plastic aspherical lenses helps reduce production costs and improve efficiency. Therefore, using plastic aspherical lenses for the second lens 102, seventh lens 107, eighth lens 108, and ninth lens 109 can correct most aberrations in the system, effectively ensuring image quality. Moreover, plastic lenses are lightweight, significantly reducing the overall weight of the lens and facilitating installation and adjustment. Additionally, plastic aspherical lenses are suitable for mass production while maintaining low overall cost.

[0033] Therefore, by rationally combining glass spherical lenses and plastic aspherical lenses, the imaging performance of large-aperture fixed-focus lenses can be improved. Furthermore, the optical architecture of five glass lenses and four plastic lenses balances the high and low temperature performance of fixed-focus lenses, enabling low cost and lightweight design.

[0034] Based on the above embodiments, the first lens 101 includes a first object-side surface near the object plane and a first image-side surface near the image plane, the first object-side surface being planar and the first image-side surface being concave; the second lens 102 includes a second object-side surface near the object plane and a second image-side surface near the image plane, the second object-side surface being concave and the second image-side surface being convex; the third lens 103 includes a third object-side surface near the object plane and a third image-side surface near the image plane, the third object-side surface being convex and the third image-side surface being convex; the fourth lens 104 includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane, the fourth object-side surface being convex and the fourth image-side surface being convex; the fifth lens 105 includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane. The image side surface, the fifth object side surface is concave, and the fifth image side surface is concave; the sixth lens 106 includes a sixth object side surface near the object surface and a sixth image side surface near the image surface, the sixth object side surface is convex, and the sixth image side surface is convex; the seventh lens 107 includes a seventh object side surface near the object surface and a seventh image side surface near the image surface, the seventh object side surface is hyperboloid and convex at the paraxial position, and the seventh image side surface is hyperboloid and concave at the paraxial position; the eighth lens 108 includes an eighth object side surface near the object surface and an eighth image side surface near the image surface, the eighth object side surface is concave, and the eighth image side surface is convex; the ninth lens 109 includes a ninth object side surface near the object surface and a ninth image side surface near the image surface, the ninth object side surface is convex, and the ninth image side surface is concave.

[0035] Specifically, the object-side surface of a lens can be understood as the surface of the lens closest to the object plane, and the image-side surface of a lens can be understood as the surface of the lens closest to the image plane.

[0036] The object-side surface of the first lens 101 is planar, while the image-side surface is concave. This can be understood as the object-side surface of the first lens 101 being planar near the optical axis, and the image-side surface being concave towards the image plane near the optical axis. In other words, the first lens 101 is a plano-concave lens. Combined with the negative optical power setting of the first lens 101, the diverging characteristics of a negative optical power lens are utilized to capture weak light rays from more directions (wide field of view). Simultaneously, the plano-concave shape ensures that the angles of these light rays are smoothly received and focused by the subsequent optical system, ultimately forming a bright and clear wide-angle image on the sensor.

[0037] The object-side surface of the second lens 102 is concave, and the image-side surface is convex. This can be understood as the object-side surface of the second lens 102 being concave towards the object plane near the optical axis, and the image-side surface being convex towards the image plane near the optical axis. In other words, the second lens 102 is a lens with a concave-convex structure. Combined with the negative power setting of the second lens 102, and under the premise of a large field of view and a large aperture, the light is "organized" through precise surface shape control. The second lens 102 allows the light entering the lens to be more orderly and uniform, laying a solid foundation for the subsequent positive power third lens 103 to converge into a high-quality image.

[0038] The object-side surface of the third lens 103 is convex, and the image-side surface is also convex. This can be understood as the object-side surface of the third lens 103 convex towards the object plane near the optical axis, and the image-side surface convex towards the image plane near the optical axis. In other words, the third lens 103 is a biconvex lens. Combined with the positive optical power setting of the third lens 103, it ensures that it can work with the first two negative optical power lenses to form a front-negative, rear-positive optical power distribution. This allows it to undertake the main converging function, correcting spherical aberration, field curvature, and astigmatism generated by the preceding lens group, reducing the light refraction burden on subsequent lens groups, and facilitating the realization of a large-aperture, miniaturized, and high-quality low-light lens structure.

[0039] The fourth lens 104 has a convex object-side surface and a convex image-side surface. This can be understood as the object-side surface of the fourth lens 104 bulging towards the object plane near the optical axis, and the image-side surface bulging towards the image plane near the optical axis; in other words, the fourth lens 104 has a biconvex structure. Combined with the positive optical power setting of the fourth lens 104, and in conjunction with the preceding three negative-negative-positive optical power lenses, it further converges light rays and stabilizes the overall focal length of the lens, corrects residual spherical aberration, astigmatism, and field curvature, and reduces the optical path height to decrease the aperture of subsequent lenses. This facilitates the realization of a large-aperture, miniaturized, and high-quality low-light lens structure.

[0040] The fifth lens 105 has a concave object-side surface and a concave image-side surface. This can be understood as the object-side surface of the fifth lens 105 being concave towards the object plane near the optical axis, and the image-side surface being concave towards the image plane near the optical axis. In other words, the fifth lens 105 is a double-concave lens. Combined with the negative power setting of the fifth lens 105, and in conjunction with the first four negative-negative-positive-positive power lenses, it is used to correct the remaining spherical aberration, astigmatism, field curvature, and chromatic aberration of the system, and to fine-tune the incident angle of the light path, ensuring that each ray of light falls precisely on the designated position of the imaging sensor.

[0041] The object-side surface of the sixth lens 106 is convex, and the image-side surface is also convex. This can be understood as the object-side surface of the sixth lens 106 convex towards the object plane near the optical axis, and the image-side surface convex towards the image plane near the optical axis. In other words, the sixth lens 106 is a biconvex lens. Combined with the positive optical power setting of the sixth lens 106, and in conjunction with the preceding five negative-negative-positive-positive-negative optical power lenses, it achieves final convergence of light rays and stabilizes the lens focal length and backstop, correcting residual spherical aberration, astigmatism, and field curvature. It also narrows the optical path to achieve a compact structure, which is beneficial for obtaining a large aperture, high resolution, and stable low-light lens.

[0042] The object-side surface of the seventh lens 107 is hyperboloidal and convex near the optical axis, while the image-side surface is hyperboloidal and concave near the optical axis. The higher-order coefficients of the hyperboloid can precisely "sculpt" the light path, forcing paraxial and off-axis rays to converge at the same point, thus significantly improving center resolution in low light and making point light sources appear as sharp points rather than light spots. Furthermore, using a hyperboloid reduces the number of lenses or complex curvatures required to correct aberrations, resulting in smoother light transitions. This means that low-light lenses have a higher tolerance for errors during assembly, are easier to mass-produce, and have more stable image quality. Combined with the positive optical power design of the seventh lens 107 and the convex-concave design near the optical axis, it ensures that even with the lens's widest aperture in low light, the center of the image is sharp, and there is no blurring or vignetting at the edges.

[0043] The object-side surface of the eighth lens 108 is concave, and the image-side surface is convex. This can be understood as the object-side surface of the eighth lens 108 being concave towards the object plane near the optical axis, and the image-side surface being convex towards the image plane near the optical axis. In other words, the eighth lens 108 is a lens with a concave-convex structure. Combined with the negative power setting of the eighth lens 108, and working in conjunction with the preceding seven negative-negative-positive-positive-negative-positive-positive lenses, it utilizes its own meniscus-shaped, gentle refractive properties to specifically correct edge lighting without disrupting the optical path balance. This ensures that the low-light lens can achieve full-frame clarity, low astigmatism, and high light transmittance on large-area, high-pixel sensors.

[0044] The object-side surface of the ninth lens 109 is convex, and the image-side surface is concave. This can be understood as the object-side surface of the ninth lens 109 bulging towards the object plane near the optical axis, and the image-side surface concave towards the image plane near the optical axis; in other words, the ninth lens 109 is a lens with a convex-concave structure. Combined with the positive power setting of the ninth lens 109, it utilizes optical principles to perform a final, precise correction of residual aberrations and light angles, ensuring sharp and clear images across the entire low-light frame; it also provides a robust physical defense for the entire lens system through its physical structure. Together with the preceding eight negative-negative-positive-positive-negative-positive-positive-negative power lenses, the entire lens achieves a perfect closed loop from "wide-range light collection" to "refined imaging." Furthermore, by controlling the surface shape, symmetrical layout, and optical power range of the eighth lens 108 and the ninth lens 109, the light transmission becomes smoother, reducing the generation of various aberrations and decreasing the tolerance sensitivity of the fixed-focus lens, thereby improving the assembly yield of the fixed-focus lens; it can also compress the light beam, thereby reducing the divergence angle of the principal ray to adapt to the CRA (principal angle) curve requirements of the image sensor located on the image plane, and improving the matching degree with the image sensor.

[0045] In summary, by rationally setting the surface design of each lens and combining it with the optical power matching method, a low-light lens design that can achieve a large aperture, a large field of view, and good imaging effect can be guaranteed.

[0046] Based on the above embodiment, the optical power of the first lens group S1 is φA, the optical power of the second lens group S2 is φB, and the optical power of the low-light lens is φ; wherein, 0.065≤φA / φ≤0.185, 0.435≤φB / φ≤0.525. The optical power of the first lens group S1 and the second lens group S2 has a reasonable distribution ratio, which allows light to transition between different lens groups with a small deflection angle, effectively controlling the introduction of system aberrations and facilitating the realization of ultra-high-definition imaging effects of the lens system.

[0047] Based on the above embodiments, the optical power of the first lens 101 is φ1, the optical power of the second lens 102 is φ2, the optical power of the third lens 103 is φ3, the optical power of the seventh lens 107 is φ7, the optical power of the eighth lens 108 is φ8, the optical power of the ninth lens 109 is φ9, and the optical power of the low-light lens is φ; wherein, -0.645≤φ1 / φ≤-0.485, -0.205<φ2 / φ≤-0.125, 0.345≤φ3 / φ≤0.445, 0.005≤φ7 / φ≤0.065, -0.055<φ8 / φ≤-0.005, and 0.205≤φ9 / φ≤0.365.

[0048] Specifically, the optical power φ1 of the first lens 101 and the optical power φ of the low-light lens are limited to -0.645 ≤ φ1 / φ ≤ -0.485, prioritizing the design of the low-light lens from a quantitative perspective. This ensures that while the low-light lens has an ultra-wide field of view, it also ensures that object-side light enters the low-light lens at the "just right" angle. This allows large-angle edge light to be smoothly "guided" into the system, avoiding severe refraction or total internal reflection at the surface of subsequent lenses, thereby reducing the generation of advanced aberrations. This results in low-distortion, high-brightness, and sharp-edge imaging effects in low-light environments.

[0049] The optical power φ2 of the second lens 102 is limited to a value satisfying -0.205 < φ2 / φ ≤ -0.125 with the optical power φ of the low-light lens, prioritizing the design of the low-light lens from a quantitative perspective. If the negative optical power of the second lens is too strong, the light will diverge excessively, making it difficult for light from the edge field of view to enter subsequent lenses, resulting in severe vignetting; if the negative optical power is too weak, it cannot effectively correct the positive distortion caused by the first lens. By setting the correspondence between the optical power of the second lens 102 and the optical power of the low-light lens within a specific ratio range, it can be ensured that the system obtains a large field of view while controlling distortion within an acceptable range, avoiding the bending of straight lines at the edge of the image.

[0050] The optical power φ3 of the third lens 103 and the optical power φ of the low-light lens are limited to a ratio of 0.345 ≤ φ3 / φ ≤ 0.445, prioritizing the design of the low-light lens from a quantitative perspective. If the value of φ3 / φ is too large, although it can quickly converge light and shorten the lens length, it will result in an excessively steep light angle, causing severe aberrations and making it prone to optical interference with the front and rear lenses. If the value of φ3 / φ is too small, the light converging speed is slower, requiring a longer optical path for imaging, leading to an increase in the overall length of the lens, which is not conducive to the miniaturization of the device. By setting the correspondence between the optical power of the third lens 103 and the optical power of the low-light lens within a specific ratio range, it is ensured that the low-light lens has a large aperture and high resolution while maintaining a compact structure, minimal aberrations, and stable imaging under different environments (temperature, distance).

[0051] The optical power φ7 of the seventh lens 107 and the optical power φ of the low-light lens are limited to a ratio of 0.005 ≤ φ7 / φ ≤ 0.065, prioritizing the design of the low-light lens from a quantitative perspective. If the value of φ7 / φ is too large, the focusing ability will be too strong, resulting in an excessively large incident angle of the edge light, exceeding the receiving angle of the sensor's microlens, causing a sharp decrease in edge illumination (vignetting). If the value of φ7 / φ is too small, the light focusing speed will be slower, requiring a longer optical path for imaging, leading to an increase in the overall length of the lens, which is detrimental to the miniaturization of the device. By setting a reasonable range for φ7 / φ, it is ensured that the light is projected onto the sensor at a gentle angle, guaranteeing edge image quality and light transmission.

[0052] The optical power φ8 of the eighth lens 108 is limited to -0.055 < φ8 / φ ≤ -0.005 with the optical power φ of the low-light lens, prioritizing the design of the low-light lens from a quantitative perspective. By setting a reasonable range for φ8 / φ, the angle of light entering the ninth lens 109 can be made gentler, thereby reducing the sensitivity of the entire lens to lens eccentricity and tilt, and improving the yield rate in mass production.

[0053] The optical power φ9 of the ninth lens 109 is limited to satisfy 0.205≤φ9 / φ≤0.365 with the optical power φ of the low-light lens, prioritizing the design of the low-light lens from a quantitative perspective. By setting a reasonable range for φ9 / φ, an optical power drift opposite to that of the previous group is generated when the temperature changes, thereby offsetting the overall focus shift and ensuring the stability of imaging under high and low temperature environments.

[0054] In summary, by using the ratios between the optical power of the first lens 101, the second lens 102, the third lens 103, the seventh lens 107, the eighth lens 109, and the ninth lens 109 and the optical power of the low-light lens, it is ensured that the final landing point of each beam of light can be precisely controlled, ensuring that the low-light lens can still achieve top-notch imaging effects with full-frame clarity, no color fringing, and low vignetting on large target surfaces and high-pixel sensors.

[0055] Based on the above embodiments, the fourth lens 104, the fifth lens 105, and the sixth lens 106 are cemented together.

[0056] Specifically, the cementing between lenses can immediately involve bonding the image-side of the preceding lens to the object-side of the following lens. In this embodiment, the fourth lens 104, the fifth lens 105, and the sixth lens 106 are cemented together to form a cemented triplet lens. This can be understood as the image-side of the fourth lens 104 being bonded to the object-side of the fifth lens 105, and the image-side of the fifth lens 105 being bonded to the object-side of the sixth lens 106. By cementing the fourth lens 104, the fifth lens 105, and the sixth lens 106, the air gap between the fourth lens 104 and the fifth lens 105, as well as the air gap between the fifth lens 105 and the sixth lens 106, can be reduced. This helps to reduce the overall optical length of the lens and also reduces tolerance sensitivity issues such as tilting / eccentricity during lens assembly, simplifying the assembly process in lens manufacturing and improving equipment efficiency. Meanwhile, the cemented joint of the fourth lens 104, fifth lens 105, and sixth lens 106 can reduce light loss caused by inter-lens reflection, improve illumination, and reduce the risk of ghosting. Furthermore, cemented lenses can be used to minimize or eliminate chromatic aberration. Using cemented lenses in optical lenses can improve image quality and reduce light energy reflection loss, thereby improving image quality and enhancing the sharpness of the lens image. Further, the fourth lens 104, fifth lens 105, and sixth lens 106 can be supported by gaskets or bonded together with adhesive; this application does not limit the specific bonding method.

[0057] Based on the above embodiments, the center thickness of the fourth lens 104, the fifth lens 105 and the sixth lens 106 is d456; wherein, 0.455≤φ456 / d456≤0.685.

[0058] Specifically, the fourth lens 104, the fifth lens 105, and the sixth lens 106 are disposed in the optical path after the aperture stop STO. By setting the ratio between the optical power of the cemented triplet lens formed by the fourth lens 104, the fifth lens 105, and the sixth lens 106 and the center thickness of the cemented triplet lens, the chromatic aberration and aberration caused by the light entering through the aperture stop STO can be effectively corrected.

[0059] Based on the above embodiment, the center length of the image-side surface of the second lens 102 from the center of the object-side surface of the third lens 103 is d23, the center length of the image-side surface of the third lens 103 from the center of the object-side surface of the fourth lens 104 is d34, and the sum of the center thicknesses of the second lens 102 and the third lens 103 is t23; wherein, 0.385≤(d23+d34) / t23≤0.645. By reasonably setting the relationship between the interval lengths of the second lens 102 and the third lens 103, the interval lengths of the third lens 103 and the fourth lens 104, and the sum of the center thicknesses of the second lens 102 and the third lens 103, it is beneficial to reduce the tolerance sensitivity of the two lenses, the second lens 102 and the third lens 103, and at the same time, the lens structure can be made compact, which is conducive to miniaturization.

[0060] Based on the above embodiments, the total optical length of the low-light lens is TTL, and the effective focal length is F; wherein, 0.158≤F / TTL≤0.168. By reasonably setting the correspondence between the effective focal length and the total optical length, it can be ensured that the low-light lens can still achieve efficient light collection, flat image plane focusing, and excellent environmental adaptability within a limited physical space.

[0061] Based on the above embodiments, the optical back focal length of the low-light lens is BFL, and the total optical length is TTL; wherein, 0.085 ≤ BFL / TTL ≤ 0.135. Properly setting the correspondence between the optical back focal length and the total optical length ensures that the low-light lens has sufficient physical space to accommodate the filter and protective glass, guaranteeing the proper assembly of the low-light lens. Furthermore, properly setting the correspondence between the optical back focal length and the total optical length can also reduce sensitivity and improve the mass production yield of the product.

[0062] As a feasible implementation method, the parameters of each lens in the low-light lens will be explained next.

[0063] Table 1. Optical design values ​​for the low-light lens in Example 1 Table 2 Design values ​​of optical physical parameters for low-light lenses The surface numbers in Table 2 are assigned according to the order of the surfaces of each lens along the optical axis from the object side to the image side. "STO" represents the aperture stop of the lens. The radius of curvature represents the curvature of the corresponding lens surface. A positive value means that the surface bends towards the image plane, and a negative value means that the surface bends towards the object plane. "Infinite" means that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. The refractive index 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 and the refractive index is 1.

[0064] Table 3 below shows the aspheric coefficient values ​​used in the current embodiment; Table 4 shows some specific parameters implemented in this embodiment.

[0065] Table 3 Aspherical coefficients of a low-light lens Where 2.418299E-04 represents 2.418299 × 10 -4 All other parameters can be represented in this way.

[0066] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations: Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AG are the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order coefficients of the aspherical polynomial.

[0067] Table 4 Specific parameters for this embodiment Figure 2 This is a schematic diagram of axial aberration of a low-light lens according to Embodiment 1 of the present invention. The vertical direction in the diagram represents the normalized aperture height (unitless), where 0 indicates it is on the optical axis and 1 indicates the maximum pupil radius. The horizontal direction represents the aberration offset relative to the ideal focal point, in millimeters (mm). Different curves in the diagram represent axial aberrations at different wavelengths. As shown in the diagram, the axial aberrations at different wavelengths are all controlled within the range of (-0.10 mm, +0.10 mm), indicating that the spherical aberration of this low-light lens is well controlled at various wavelengths, meeting the requirements for wide-spectrum applications.

[0068] Figure 3 This is a schematic diagram of the light fan of a low-light lens according to Embodiment 1 of the present invention. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all light rays are focused at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberration of different wavelengths but also represent the magnitude of transverse chromatic aberration. Figure 3 It can be seen that the system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0069] Figure 4 This is a schematic diagram of field curvature distortion of a low-light lens according to Embodiment 1 of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit. Figure 4 As can be seen, the lens provided in this embodiment effectively controls the field curvature from light wavelengths of 436nm to 656nm, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 4 It can be seen that the maximum distortion of the lens provided in this embodiment is 13.6567%.

[0070] In summary, Embodiment 1 of this invention provides a low-light lens system with an equivalent focal length of 6.0mm, an aperture of Fno0.85, a total length TTL of less than 51.0mm, and an imaging range compatible with a 1 / 1.8-inch sensor. This lens system consists of five standard glass spherical lenses and four aspherical plastic lenses, with a reasonable number of lenses and a simple and compact structure. Furthermore, the optical power and position of each lens are optimized, resulting in a large aperture, short total length, and high resolution while maintaining low cost. This lens system is highly competitive in the market. The lens system has a field of view of approximately 65° and a resolution compatible with an 8MP sensor.

[0071] Example 2 Figure 5 This is a schematic diagram of the structure of a low-light lens provided in Embodiment 2 of the present invention, as shown below. Figure 5 As shown, the low-light lens provided in Embodiment 2 of the present invention includes a first lens group S1 and a second lens group S2 arranged sequentially along the optical axis from the object plane to the image plane; the first lens group S1 has a positive optical power and includes a first lens 101 with negative optical power, a second lens 102 with negative optical power, and a third lens 103 with positive optical power; the second lens group S2 has a positive optical power and includes a fourth lens 104 with positive optical power, a fifth lens 105 with negative optical power, a sixth lens 106 with positive optical power, and a third lens 103 with positive optical power. The lens comprises a seventh lens 107 with negative optical power, an eighth lens 108 with negative optical power, and a ninth lens 109 with positive optical power; the low-light lens has nine lenses with optical power; the combined optical power of the fourth lens 104, the fifth lens 105, and the sixth lens 106 is φ456, the combined optical power of the seventh lens 107, the eighth lens 108, and the ninth lens 109 is φ789, and the optical power of the low-light lens is φ; wherein, 0.245 < φ456 / φ ≤ 0.425, and 0.245 ≤ φ789 / φ ≤ 0.385.

[0072] Other parameters are the same as in Example 1, and will not be repeated here.

[0073] As another feasible implementation method, the specific parameters of the low-light lens are explained below.

[0074] Table 5. Optical design values ​​for the low-light lens in Example 2 Table 6 Design values ​​of optical physical parameters for low-light lenses The surface numbers in Table 6 are assigned according to the order of the surfaces of each lens along the optical axis from the object side to the image side. "STO" represents the aperture stop of the lens. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value means that the surface bends towards the image plane, and a negative value means that the surface bends towards the object plane. "Infinite" means that the surface is a plane with an infinite radius of curvature. The thickness represents the central axial distance between the current surface and the next surface. The refractive index 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.

[0075] Table 7 below shows the aspheric coefficient values ​​used in the current embodiment; Table 8 shows some specific parameters implemented in this embodiment.

[0076] Table 7 Aspherical coefficients of a low-light lens Where 1.742128E-02 represents 1.742128 × 10 -4 All other parameters can be represented in this way.

[0077] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations: Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AG are the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order coefficients of the aspherical polynomial.

[0078] Table 8 Specific parameters for this embodiment Figure 6This is a schematic diagram of axial aberration of a low-light lens according to Embodiment 2 of the present invention. The vertical direction in the diagram represents the normalized aperture height (unitless), where 0 indicates it is on the optical axis and 1 indicates the maximum pupil radius. The horizontal direction represents the aberration offset relative to the ideal focal point, in millimeters (mm). Different curves in the diagram represent axial aberrations at different wavelengths. As shown in the diagram, the axial aberrations at different wavelengths are all controlled within the range of (-0.10 mm, +0.10 mm), indicating that the spherical aberration of this low-light lens is well controlled at various wavelengths, meeting the requirements for wide-spectrum applications.

[0079] Figure 7 This is a schematic diagram of the light fan of a low-light lens according to Embodiment 2 of the present invention. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all light rays are focused at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberration of different wavelengths but also represent the magnitude of transverse chromatic aberration. Figure 7 It can be seen that the system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0080] Figure 8 This is a schematic diagram of field curvature distortion of a low-light lens according to Embodiment 2 of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit. Figure 8 As can be seen, the lens provided in this embodiment effectively controls the field curvature from light wavelengths of 436nm to 656nm, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 8 It can be seen that the maximum distortion of the lens provided in this embodiment is 14.2297%.

[0081] In summary, Embodiment 2 of this invention provides a low-light lens system with an equivalent focal length of 6.0mm, an aperture of Fno0.84, a total length TTL of less than 51.0mm, and an imaging range compatible with a 1 / 1.8-inch chip. This lens system consists of five standard glass spherical lenses and four aspherical plastic lenses, with a reasonable number of lenses and a simple and compact structure. Furthermore, the optical power and position of each lens are reasonable, possessing the characteristics of a large aperture, short total length, and high resolution while also being low-cost. This lens system is highly competitive in the market. The field of view of this lens system is approximately 66°, and its resolution is compatible with an 8MP chip.

[0082] Example 3 Figure 9 This is a schematic diagram of the structure of a low-light lens provided in Embodiment 3 of the present invention, as shown below. Figure 9 As shown, the low-light lens provided in Embodiment 3 of the present invention includes a first lens group S1 and a second lens group S2 arranged sequentially along the optical axis from the object plane to the image plane; the first lens group S1 has a positive optical power and includes a first lens 101 with negative optical power, a second lens 102 with negative optical power, and a third lens 103 with positive optical power; the second lens group S2 has a positive optical power and includes a fourth lens 104 with positive optical power, a fifth lens 105 with negative optical power, a sixth lens 106 with positive optical power, and a third lens 103 with positive optical power. The lens comprises a seventh lens 107 with negative optical power, an eighth lens 108 with negative optical power, and a ninth lens 109 with positive optical power; the low-light lens has nine lenses with optical power; the combined optical power of the fourth lens 104, the fifth lens 105, and the sixth lens 106 is φ456, the combined optical power of the seventh lens 107, the eighth lens 108, and the ninth lens 109 is φ789, and the optical power of the low-light lens is φ; wherein, 0.245 < φ456 / φ ≤ 0.425, and 0.245 ≤ φ789 / φ ≤ 0.385.

[0083] Other parameters are the same as in Example 1, and will not be repeated here.

[0084] As another feasible implementation method, the specific parameters of the low-light lens are explained below.

[0085] Table 9. Optical design values ​​for the low-light lens in Example 3 Table 10 Design values ​​of optical physical parameters for low-light lenses The surface numbers in Table 10 are assigned according to the order of the surfaces of each lens along the optical axis from the object side to the image side. "STO" represents the aperture stop of the lens. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value means that the surface bends towards the image plane, and a negative value means that the surface bends towards the object plane. "Infinite" means that the surface is a plane with an infinite radius of curvature. The thickness represents the central axial distance between the current surface and the next surface. The refractive index 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.

[0086] Table 11 below shows the aspheric coefficient values ​​used in the current embodiment; Table 12 shows some specific parameters implemented in this embodiment.

[0087] Table 11 Aspherical coefficients of a low-light lens Where 1.141509E-04 represents 1.141509 × 10 -4 All other parameters can be represented in this way.

[0088] The conicity coefficients of aspherical surfaces can be defined using the following aspherical formulas, but are not limited to the following representations: Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AG are the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order coefficients of the aspherical polynomial.

[0089] Table 12 Specific parameters for this embodiment Figure 10 This is a schematic diagram of axial aberration of a low-light lens provided in Embodiment 3 of the present invention. The vertical direction in the diagram represents the normalized aperture height (unitless), where 0 indicates it is on the optical axis and 1 indicates the maximum pupil radius. The horizontal direction represents the aberration offset relative to the ideal focal point, in millimeters (mm). Different curves in the diagram represent axial aberrations at different wavelengths. As shown in the diagram, the axial aberrations at different wavelengths are all controlled within the range of (-0.10 mm, +0.10 mm), indicating that the spherical aberration of this low-light lens is well controlled at various wavelengths, meeting the requirements for wide-spectrum applications.

[0090] Figure 11 This is a schematic diagram of the light fan of a low-light lens according to Embodiment 3 of the present invention. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all light rays are focused at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberration of different wavelengths but also represent the magnitude of transverse chromatic aberration. Figure 11 It can be seen that the system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0091] Figure 12 This is a schematic diagram of field curvature distortion of a low-light lens according to Embodiment 3 of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature in mm; the vertical coordinate represents the normalized image height, which has no unit. Figure 12As can be seen, the lens provided in this embodiment effectively controls the field curvature from light wavelengths of 436nm to 656nm, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit; from Figure 12 It can be seen that the maximum distortion of the lens provided in this embodiment is 14.9607%.

[0092] In summary, Embodiment 3 of this invention provides a low-light lens system with an equivalent focal length of 6.0mm, an aperture of Fno0.85, a total length TTL of less than 51.0mm, and an imaging range compatible with a 1 / 1.8-inch chip. This lens system consists of five standard glass spherical lenses and four aspherical plastic lenses, with a reasonable number of lenses and a simple and compact structure. Furthermore, the optical power and position of each lens are reasonable, possessing the characteristics of a large aperture, short total length, and high resolution while also being low-cost. This lens system is highly competitive in the market. The field of view of this lens system is approximately 65°, and its resolution is compatible with an 8MP chip.

[0093] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. 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 modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A low-light lens, characterized in that, It includes a first lens group and a second lens group arranged sequentially from the object plane to the image plane along the optical axis; The first lens group has a positive optical power and includes a first lens with negative optical power, a second lens with negative optical power, and a third lens with positive optical power. The second lens group has positive optical power, and the second lens group includes a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, and a ninth lens with positive optical power; the low-light lens has nine lenses with optical power. The combined optical power of the fourth lens, the fifth lens, and the sixth lens is φ456; the combined optical power of the seventh lens, the eighth lens, and the ninth lens is φ789; and the optical power of the low-light lens is φ. Among them, 0.245<φ456 / φ≤0.425, 0.245≤φ789 / φ≤0.

385.

2. The low-light lens according to claim 1, characterized in that, The first lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses; The second lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses.

3. The low-light lens according to claim 1, characterized in that, The first lens includes a first object-side surface near the object plane and a first image-side surface near the image plane. The first object-side surface is a plane, and the first image-side surface is a concave surface. The second lens includes a second object-side surface near the object plane and a second image-side surface near the image plane. The second object-side surface is concave, and the second image-side surface is convex. The third lens includes a third object-side surface near the object plane and a third image-side surface near the image plane. The third object-side surface is convex, and the third image-side surface is convex. The fourth lens includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane. The fourth object-side surface is convex, and the fourth image-side surface is convex. The fifth lens includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane. The fifth object-side surface is concave, and the fifth image-side surface is concave. The sixth lens includes a sixth object-side surface near the object plane and a sixth image-side surface near the image plane. The sixth object-side surface is convex, and the sixth image-side surface is convex. The seventh lens includes a seventh object-side surface near the object plane and a seventh image-side surface near the image plane. The seventh object-side surface is a hyperboloid and is convex at the paraxial position, and the seventh image-side surface is a hyperboloid and is concave at the paraxial position. The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane. The eighth object-side surface is concave, and the eighth image-side surface is convex. The ninth lens includes a ninth object-side surface near the object plane and a ninth image-side surface near the image plane. The ninth object-side surface is convex, and the ninth image-side surface is concave.

4. The low-light lens according to claim 1, characterized in that, The optical power of the first lens group is φA, the optical power of the second lens group is φB, and the optical power of the low-light lens is φ; Among them, 0.065≤φA / φ≤0.185, 0.435≤φB / φ≤0.

525.

5. The low-light lens according to claim 1, characterized in that, The optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the seventh lens is φ7, the optical power of the eighth lens is φ8, the optical power of the ninth lens is φ9, and the optical power of the low-light lens is φ. Among them, -0.645≤φ1 / φ≤-0.485, -0.205<φ2 / φ≤-0.125, 0.345≤φ3 / φ≤0.445, 0.005≤φ7 / φ≤0.065, -0.055<φ8 / φ≤-0.005, and 0.205≤φ9 / φ≤0.

365.

6. The low-light lens according to claim 1, characterized in that, The fourth lens, the fifth lens, and the sixth lens are cemented together.

7. The low-light lens according to claim 4, characterized in that, The center thickness of the fourth lens, the fifth lens, and the sixth lens is d456; Wherein, 0.455≤φ456 / d456≤0.

685.

8. The low-light lens according to claim 1, characterized in that, The distance from the center of the image side of the second lens to the center of the object side of the third lens is d23, the distance from the center of the image side of the third lens to the center of the object side of the fourth lens is d34, and the sum of the center thicknesses of the second lens and the third lens is t23. Among them, 0.385≤(d23+d34) / t23≤0.

645.

9. The low-light lens according to claim 1, characterized in that, The total optical length of the low-light lens is TTL, and the effective focal length is F; Wherein, 0.158≤F / TTL≤0.

168.

10. The low-light lens according to claim 1, characterized in that, The optical back focal length of the low-light lens is BFL, and the total optical length is TTL. Wherein, 0.085≤BFL / TTL≤0.135.

Images