Low-illumination imaging lens and electronic device

Abstract

The application discloses a low-illumination imaging lens and electronic equipment. The lens sequentially comprises a first lens group, a second lens group and a third lens group from an object side to an image side; the first lens group sequentially comprises a positive refractive power lens and a first cemented lens group from the object side to the image side, and the first cemented lens group comprises a positive refractive power lens and a negative refractive power lens; the second lens group comprises two or less than two lenses and comprises at least one positive refractive power lens; and the third lens group comprises a positive refractive power lens and a negative refractive power lens. The optical lens disclosed by the application has an F1.6 light transmittance, excellent imaging, clear image quality, excellent low-illumination processing capability and small depth of field brought by a large aperture, can adapt to more shooting environments, and has compact lens structure and better portability than lenses on the market.

Description

Technical Field

[0001] This invention relates to the field of low-light imaging lens technology, and more particularly to a low-light imaging lens and electronic device. Background Technology

[0002] Low-light imaging lenses are special lenses that can still produce clear images in low-light environments, such as at night or in dimly lit indoor spaces. However, they have at least one of the following drawbacks:

[0003] 1) Generally, lenses have low light transmission and low energy utilization, which cannot meet the requirements for distinguishing objects in low-light environments.

[0004] 2) Generally, lenses have a small spectral range and are used in a limited range of environments, which cannot meet the requirements of all-weather use.

[0005] 3) Lenses generally fail reliability tests such as impact and vibration resistance. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a low-light imaging lens and electronic device. This lens can at least solve one of the technical disadvantages mentioned in the background art.

[0007] According to one aspect of the present invention, a low-light imaging lens is provided, comprising a first lens group, a second lens group, and a third lens group in sequence from the object side to the image side;

[0008] The first lens group consists of a positive refractive index lens and a set of first cemented lenses in sequence from the object side to the image side. The first cemented lenses are composed of a positive refractive index lens and a negative refractive index lens.

[0009] The second lens group consists of two or fewer lenses, including at least one positive refractive index lens;

[0010] The third lens group consists of a positive refractive index lens and a negative refractive index lens.

[0011] In the above technical solution, the first lens group consists of a positive refractive index lens and a set of first cemented lenses. The first cemented lenses are formed by cementing a positive refractive index lens and a negative refractive index lens together. The positive refractive index lens has a converging effect on light, allowing the light to initially converge and form a relatively clear image. The combination of positive and negative refractive index lenses in the cemented lenses is mainly used to correct chromatic aberration. Different wavelengths of light have different refractive indices when passing through a lens, which can lead to dispersion, causing the image to have color spots or colored edges. Cemented lenses can effectively eliminate this chromatic aberration and improve image quality. The second lens group consists of two or fewer lenses, including at least one positive refractive index lens. The positive refractive index lens continues to converge the light, further reducing the size of the image and making the image clearer. At the same time, a smaller number of lenses helps to simplify the optical path structure, reduce light loss between lenses, increase light transmittance, and enhance the lens's imaging capability in low-light environments. The third lens group consists of a positive refractive index lens and a negative refractive index lens. Positive refractive index lenses continue to converge light, while negative refractive index lenses appropriately diverge it. Working together, they further correct aberrations, such as spherical and coma, resulting in more perfect images and improved lens image quality. The optical lens has an aperture of F1.6, allowing it to receive more light per unit time, thus achieving sufficient exposure even in low-light conditions, resulting in clear and bright images. This adapts to a wider range of shooting environments, such as nighttime and low-light indoor scenes. Thanks to the rational design and combination of the lens group, various aberrations are effectively corrected, reducing imaging defects. Simultaneously, the large aperture provides a shallow depth of field, adapting to more shooting environments, and the lens itself has a compact structure, making it more portable than similar lenses on the market. The lens has a wavelength range of 435-940nm, covering visible light and part of the near-infrared band, meeting the application needs of special scenarios and enabling clear imaging in all weather conditions. Different wavelengths of light have different penetration and reflection characteristics; a lens with a wide wavelength range can better adapt to these complex environments and acquire richer image information. All lenses in this solution use ground spherical glass lenses. The manufacturing process for spherical lenses is relatively mature and cost-effective, and their simple optical path structure facilitates assembly. The high surface precision of ground spherical glass lenses ensures good light propagation within the lens, reducing scattering and loss, and improving image quality. Simultaneously, the simple optical path structure and ease of assembly also contribute to higher assembly yield and lower production costs. Testing showed that the optical lens can withstand vibrations of 10Hz to 150Hz with a displacement of 0.15mm at 10Hz, conforming to the IEC60068-2-6 standard. After testing, the image appeared normal and free of dust, indicating that the lens has good stability and reliability under vibration conditions and will not cause lens displacement, loosening, or dust accumulation that would affect image quality.In addition, the lens has an impact resistance of 1200G, a pulse duration of 0.4ms, a half-sine wave, and three impacts in the Z direction. After being powered on and equipped with a battery, and simulating a gunshot test, the product's appearance and imaging were normal, and there was no dust. This indicates that the lens remains structurally robust and can maintain normal operation even when subjected to strong impacts. It is suitable for some occasions with high requirements for lens impact resistance, such as military and outdoor adventure.

[0012] In some embodiments, the first lens group includes a first lens, a second lens, and a third lens sequentially from the object side to the image side; the second lens and the third lens constitute a first cemented lens.

[0013] The first lens is a biconvex positive power lens;

[0014] The second lens has positive refractive power and its object-side surface is convex.

[0015] The third lens has a negative refractive index and its object-side surface is concave.

[0016] In the above technical solution, the first lens is a biconvex positive power lens. The shape of a biconvex lens allows light rays to converge from both sides towards the center when passing through the lens, exhibiting a strong ability to converge light. Positive power indicates that the lens has a converging effect on light rays, enabling parallel light rays to converge at a point to form a real image. Choosing a biconvex positive power lens as the first lens is beneficial for compressing the front aperture of the optical system, contributing to lens miniaturization. Simultaneously, the symmetrical structure of the biconvex lens is also beneficial for controlling distortion, reducing image deformation, and facilitating the realization of distortion-free lenses. The second lens has positive refractive power and a convex object-side surface. Working in conjunction with the first lens, it further enhances light convergence, improving image brightness and sharpness. It works in conjunction with the negative refractive index of the third lens, laying the foundation for subsequent chromatic aberration correction. The third lens is a negative refractive index lens with a concave object-side surface, cemented together with the second lens to form a first cemented lens. The interaction of positive and negative refractive indices effectively corrects chromatic aberration, causing light rays of different wavelengths to converge at a point again, eliminating dispersion, and resulting in clear imaging and accurate colors. The cemented design simplifies the optical path structure, reduces light reflection and scattering, improves light transmittance, enhances low-light imaging capabilities, and also reduces the size and weight of the lens, making it compact and portable. The cemented lens structure is stable and not easily affected by external factors, ensuring stable image quality and making it suitable for long-term stable shooting or use in complex environments.

[0017] In some embodiments, the lens satisfies the following condition:

[0018] Nd2<1.5, Vd2>70, ΔPg,F>0.0035

[0019] Where Nd2 is the refractive index of the second lens, Vd2 is the Abbe coefficient of the second lens, and ΔPg,F is the relative partial dispersion.

[0020] In the aforementioned technical solution, the second lens uses a material with a refractive index less than 1.5. This low-refractive-index material results in less refraction of light as it passes through the lens, thereby reducing light propagation loss and improving the lens's transmittance. Especially in low-light environments, this design can more effectively collect and transmit light, significantly enhancing image brightness. Furthermore, the second lens has an Abbe number greater than 70. Materials with a high Abbe number effectively reduce chromatic aberration, resulting in clearer images and more accurate colors. Simultaneously, the lens has a relative partial dispersion greater than 0.0035, a parameter describing the material's dispersion characteristics within a specific wavelength range. Materials with high relative partial dispersion help correct the second-order spectrum, further reducing focusing differences between different wavelengths of light after eliminating primary chromatic aberration, thus improving image quality. By selecting materials with high Abbe numbers and high relative partial dispersion, chromatic aberration can be controlled more precisely, allowing light of different wavelengths to be focused more accurately at the same position after passing through the lens, significantly improving image sharpness and color accuracy. This is particularly important for low-light imaging lenses, as high-quality imaging is crucial for obtaining clear and accurate images in low-light environments.

[0021] In some embodiments, the lens satisfies the following condition:

[0022] Nd3>1.8, Vd3<30

[0023] Where Nd3 is the refractive index of the third lens and Vd3 is the Abbe coefficient of the third lens.

[0024] In the aforementioned technical solutions, high-refractive-index lens materials are generally more effective at converging light, meaning that lenses can be designed to be thinner while maintaining the same optical performance requirements. This design not only helps reduce the thickness and weight of the lens but also improves the edge thickness uniformity, thereby enhancing the overall performance of the optical system. Materials with low Abbe coefficients produce significant chromatic aberration during imaging, leading to image blurring and color distortion. However, when a low Abbe coefficient lens is combined with another high Abbe coefficient lens (a second lens), chromatic aberration can be more precisely controlled through the mutual cancellation of positive and negative dispersion.

[0025] In some embodiments, the second lens group consists of two lenses, which sequentially include a negative refractive index lens and a positive refractive index lens from the object side to the image side; the positive refractive index lens and the negative refractive index lens constitute a second cemented lens;

[0026] This negative refractive index lens has a concave object side and a concave image side.

[0027] This positive refractive lens has a convex side.

[0028] In the above technical solution, chromatic aberration can be effectively corrected by cementing together positive and negative refractive index lenses. When light of different wavelengths passes through a lens, dispersion occurs due to their different refractive indices, resulting in color spots or colored edges in the image. This dispersion is caused by the variation in the speed of light in the medium with wavelength, causing different wavelengths of light to refract at different angles within the lens. Cemented lenses, by tightly cementing positive and negative refractive index lenses together, allow light of different wavelengths to refocus at the same point after passing through the lens, thereby eliminating chromatic aberration and significantly improving image quality. In high-precision optical systems, this contributes to obtaining clear and accurate images.

[0029] In some embodiments, the second lens group consists of fewer than two lenses, including a positive refractive index lens; the positive refractive index lens has a concave object side and a convex image side.

[0030] In the above technical solutions, the concave-convex lens design can effectively reduce aberrations, especially spherical aberration and coma, and improve image quality. By optimizing the curvature and shape of the lens, the concave-convex lens can better control the path of light, making the light more evenly distributed when passing through the lens, reducing light scattering and loss, thereby improving the efficiency of the optical system.

[0031] In some embodiments, the third lens group consists of a positive refractive index lens and a negative refractive index lens in sequence from the object side to the image side; the object side of the positive refractive index lens is convex; and the object side of the negative refractive index lens is concave.

[0032] In the above technical solution, the combination of positive and negative refractive index lenses in the third lens group can effectively correct chromatic aberration. Positive refractive index lenses converge light, while negative refractive index lenses diverge light. Through this interaction, the focusing point of different wavelengths of light can be more precisely controlled, thereby reducing chromatic aberration and improving the color accuracy of the image. Specifically, the positive refractive index lens is mainly responsible for converging light to a single focal point, while the negative refractive index lens corrects the chromatic aberration introduced by the positive refractive index lens through its diverging effect, allowing light of different wavelengths to be focused more accurately at the same position. The positive refractive index lens can also reduce spherical aberration, while the negative refractive index lens can reduce field curvature and distortion. By rationally designing the shape and materials of the lenses, not only can better imaging effects be achieved, but the compactness and lightweight of the lens system can also be maintained.

[0033] In some embodiments, the positive refractive index lens of the second lens group satisfies the following condition:

[0034] Nd4>1.9, VD4<20, ΔPg,F>0.0035

[0035] Wherein, Nd4 is the refractive index of the positive refractive lens, Vd4 is the Abbe coefficient of the positive refractive lens, and ΔPg,F is the relative partial dispersion of the positive refractive lens.

[0036] In the aforementioned technical solutions, high-refractive-index lens materials can generally converge light more effectively, allowing lenses to be designed to be thinner while maintaining the same optical performance. This design not only helps reduce the thickness and weight of the lens but also improves the edge thickness uniformity, thereby enhancing the overall performance of the optical system. High-refractive-index materials in optical systems can effectively control the refraction angle of light, reducing light scattering and loss, thus improving image quality. Using high-refractive-index, low-dispersion materials can effectively control the refraction angle of light, significantly improving image quality. Relative partial dispersion is an important parameter describing the dispersive characteristics of a material within a specific wavelength range. Together with the Abbe coefficient, it allows for more precise control of chromatic aberration. Materials with high relative partial dispersion help correct second-order spectra, that is, after eliminating primary chromatic aberration, further reducing the focusing differences of light at different wavelengths, thereby significantly improving image quality.

[0037] In some embodiments, the positive and negative refractive index lenses of the third lens group satisfy the following condition:

[0038] Nd5<1.7, Vd5>55, Nd6>1.72, Vd6<30

[0039] Wherein, Nd5 is the refractive index of the positive refractive lens, Vd5 is the Abbe coefficient of the positive refractive lens, Nd6 is the refractive index of the positive refractive lens, and Vd6 is the Abbe coefficient of the positive refractive lens.

[0040] In the aforementioned technical solution, using positive power optical lenses can effectively control the refraction angle of light, especially when placed at the rear of the lens, significantly improving the light path and thus reducing the aperture at the rear of the lens. Furthermore, employing high-refractive-index, low-dispersion materials can further precisely control the refraction angle of light, effectively improving image quality and contributing to a reduction in the outer diameter of the lens's rear end. The materials of the last three lenses are, in order, heavy flint glass, lanthanum crown glass, and heavy flint glass. This high-low-high optical material combination allows light to transition more evenly to the imaging surface, reducing light scattering and loss. This uniform light transition not only reduces the lens's sensitivity to tolerances but also ensures high image quality while maintaining lens miniaturization. This design significantly improves image quality without increasing system complexity and weight, making it particularly suitable for applications requiring high resolution, low chromatic aberration, and low illumination.

[0041] According to another aspect of the present invention, an electronic device is provided, comprising the low-light imaging lens described above; and

[0042] An image sensor is configured to receive an image formed by the low-light imaging lens.

[0043] In the above technical solution, the advantage of this electronic device relies on the low-light imaging lens, which will not be elaborated here. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0045] Figure 1 This is a schematic diagram of the structure of Example 1 of the low-light imaging lens of the present invention;

[0046] Figure 2 This is the MTF diagram of the low-light imaging lens example 1 of the present invention under visible light 435-650nm;

[0047] Figure 3 This is a near-infrared 850nm MTF curve of Example 1 of the low-light imaging lens of the present invention;

[0048] Figure 4 This is a near-infrared 940nm MTF curve of Example 1 of the low-light imaging lens of the present invention;

[0049] Figure 5 This is a distortion image of the low-light imaging lens example 1 of the present invention under visible light 435-650nm;

[0050] Figure 6 This is a longitudinal chromatic aberration curve (magnification chromatic aberration diagram) of the visible light 435-650nm in Example 1 of the low-light imaging lens of the present invention;

[0051] Figure 7 This is a dot plot of the low-light imaging lens example 1 of the present invention in the visible light 435-650nm range;

[0052] Figure 8 This is a relative illumination diagram of the low-light imaging lens of the present invention at visible light 435-650nm, as shown in Example 1.

[0053] Figure 9 This is a schematic diagram of the structure of Example 2 of the low-light imaging lens of the present invention;

[0054] Figure 10 This is the MTF diagram of the low-light imaging lens example 2 of the present invention under visible light 435-650nm;

[0055] Figure 11 This is a near-infrared 850nm MTF curve of Example 2 of the low-light imaging lens of the present invention;

[0056] Figure 12 This is a near-infrared 940nm MTF curve of Example 2 of the low-light imaging lens of the present invention;

[0057] Figure 13 This is a distortion image of the low-light imaging lens of the present invention in the visible light 435-650nm range, as shown in Example 2.

[0058] Figure 14 This is a longitudinal chromatic aberration curve (magnification chromatic aberration diagram) of the visible light 435-650nm in Example 2 of the low-light imaging lens of the present invention;

[0059] Figure 15 This is a dot plot of the low-light imaging lens example 2 of the present invention in the visible light 435-650nm range;

[0060] Figure 16 This is a relative illumination diagram of the low-light imaging lens of the present invention at visible light 435-650nm, Example 2;

[0061] Figure 17 This is a schematic diagram of the structure of Example 3 of the low-light imaging lens of the present invention;

[0062] Figure 18 This is the MTF diagram of the low-light imaging lens of the present invention at visible light 435-650nm in Example 3;

[0063] Figure 19 This is an example 3 of the low-light imaging lens of the present invention, showing the near-infrared 850nm MTF curve;

[0064] Figure 20 This is a near-infrared 940nm MTF curve of Example 3 of the low-light imaging lens of the present invention;

[0065] Figure 21 This is a distortion image of the low-light imaging lens of the present invention under visible light 435-650nm in Example 3;

[0066] Figure 22 This is a longitudinal chromatic aberration curve (magnification chromatic aberration diagram) of the visible light 435-650nm in Example 3 of the low-light imaging lens of the present invention;

[0067] Figure 23 This is a dot plot of the low-light imaging lens example 3 of the present invention in the visible light 435-650nm range;

[0068] Figure 24 This is a relative illumination diagram of the low-light imaging lens of the present invention at visible light 435-650nm, as shown in Example 3.

[0069] Figure 25This is a schematic diagram of the structure of Example 4 of the low-light imaging lens of the present invention. Detailed Implementation

[0070] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] The object of this invention is to provide a low-light imaging lens and electronic device with high optical performance. Embodiments according to the invention will now be described in detail with reference to the accompanying drawings.

[0072] Figure 1 , Figure 9 , Figure 17 These are cross-sectional views of low-light imaging lenses (optical systems) according to Examples 1 to 3. The low-light imaging lenses according to each example are used in imaging devices including digital video cameras, digital still cameras, broadcast cameras, surveillance cameras, etc., and in optical devices with interchangeable lenses. In each cross-sectional view, the left side is the object-side OBJ and the right side is the image-side IMA. In each cross-sectional view, Lij represents the j-th lens of the i-th lens group. STO represents the aperture stop (fixed aperture stop or visible aperture stop). IMA represents the image plane, and when the low-light imaging lenses 1 to 3 according to each example are used in the imaging optical system of a digital video camera or digital still camera, a solid-state imaging element (photoelectric conversion element), such as a CMOS image sensor or a CCD image sensor, is arranged on the image plane IMA.

[0073] The low-light imaging lenses of various examples, in order from the object side to the image side, include: a first lens group L1, a second lens group L2, and a third lens group L3. The first lens group L1, from the object side to the image side, consists of a positive refractive index lens and a set of first cemented lenses, which are composed of a positive refractive index lens and a negative refractive index lens. The second lens group L2 consists of two or fewer lenses, including at least one positive refractive index lens. The third lens group L3 consists of a positive refractive index lens and a negative refractive index lens. The first lens group, consisting of a positive refractive index lens and a set of first cemented lenses, is formed by cementing a positive refractive index lens and a negative refractive index lens together. The positive refractive index lens has a converging effect on light, allowing light to initially converge and form a relatively clear image. The combination of positive and negative refractive index lenses in the cemented lenses is mainly used to correct chromatic aberration. Different wavelengths of light have different refractive indices when passing through a lens, causing chromatic aberration and resulting in colored spots or edges in the image. Cemented lenses can effectively eliminate this chromatic aberration and improve image quality. The second lens group consists of two or fewer lenses, including at least one positive refractive index lens. The positive refractive index lens continues to converge the light, further reducing the image size and making the image sharper. At the same time, a smaller number of lenses helps simplify the optical path structure, reduce light loss between lenses, increase light transmittance, and enhance the lens's imaging capabilities in low-light environments. The third lens group consists of one positive refractive index lens and one negative refractive index lens. The positive refractive index lens continues to converge the light, while the negative refractive index lens appropriately diverges the light. Together, they can further correct aberrations, such as spherical aberration and coma, resulting in a more perfect image and improving the lens's image quality. The optical lens boasts an F1.6 aperture, allowing it to capture more light per unit time. This ensures sufficient exposure even in low-light conditions, resulting in clear and bright images, adapting to a wider range of shooting environments, such as nighttime and low-light indoor scenes. Thanks to the well-designed and combined lens group, various aberrations are effectively corrected, reducing imaging defects. Simultaneously, the large aperture provides a shallow depth of field, accommodating a wider range of shooting environments, and the lens itself has a compact structure, offering superior portability compared to similar lenses on the market. The lens's wavelength range is 435-940nm, covering visible light and part of the near-infrared band, meeting the application needs of special scenarios and enabling clear imaging in all weather conditions. Different wavelengths of light have different penetration and reflection characteristics; a wide wavelength range lens can better adapt to these complex environments, acquiring richer image information. All lenses in this solution utilize ground spherical glass lenses. The manufacturing process of spherical lenses is relatively mature and cost-effective, and the optical path structure is simple, facilitating assembly. The high surface precision of ground spherical glass lenses ensures good light propagation within the lens, reducing light scattering and loss, and improving image quality. At the same time, the simple optical path structure and easy assembly characteristics also help to improve the yield of optical assembly and reduce production costs.Testing revealed that the optical lens can withstand vibrations ranging from 10Hz to 150Hz, with a displacement of 0.15mm at 10Hz, conforming to the IEC60068-2-6 standard. After the test, the lens exhibited normal appearance and no dust, demonstrating its excellent stability and reliability under vibration conditions. It will not cause lens displacement, loosening, or dust accumulation that could affect image quality. Furthermore, the lens withstands an impact of 1200G, a pulse duration of 0.4ms, a half-sine wave, three impacts in the Z-direction, powered on with a battery, and a simulated gunshot test. The product's appearance and image remained normal, with no dust, indicating that the lens maintains its structural integrity and normal operation even under strong impact. This makes it suitable for applications requiring high impact resistance, such as military and outdoor adventure applications.

[0074] The first lens group L1, from the object side to the image side, includes a first lens L11, a second lens L12, and a third lens L13 in sequence. The second lens L12 and the third lens L13 form a first cemented lens G1. The first lens L11 is a biconvex positive power lens. The second lens L12 has positive refractive power and a convex surface on the object side. The third lens L13 has negative refractive power and a concave surface on the object side. The first lens is a biconvex positive power lens. The shape of a biconvex lens allows light rays to converge from both sides towards the center when passing through the lens, exhibiting a strong ability to converge light rays. Positive power indicates that the lens has a converging effect on light rays, enabling parallel light rays to converge at a point to form a real image. Choosing a biconvex positive power lens as the first lens is beneficial for compressing the front aperture of the optical system, which helps to achieve lens miniaturization. At the same time, the symmetrical structure of the biconvex lens is also beneficial for controlling distortion, reducing image deformation, and facilitating the realization of distortion-free lenses. The second lens has positive refractive power and a convex object-side surface. Working in conjunction with the first lens, it further enhances light convergence, improving image brightness and sharpness. It works in conjunction with the negative refractive power of the third lens to lay the foundation for subsequent chromatic aberration correction. The third lens is a negative refractive power lens with a concave object-side surface, cemented together with the second lens to form the first cemented lens. The interaction of positive and negative refractive powers effectively corrects chromatic aberration, causing light of different wavelengths to converge at a single point, eliminating dispersion, and resulting in clear images and accurate colors. The cemented design simplifies the optical path structure, reduces light reflection and scattering, increases light transmittance, enhances low-light imaging capabilities, and reduces the lens's size and weight, making it compact and portable. The cemented lens structure is stable and less susceptible to external interference, ensuring stable image quality, making it suitable for long-term stable shooting or use in complex environments.

[0075] The second lens satisfies the following condition:

[0076] Nd2<1.5, Vd2>70, ΔPg,F>0.0035

[0077] Where Nd2 is the refractive index of the second lens, Vd2 is the Abbe coefficient of the second lens, and ΔPg,F is the relative partial dispersion. The second lens is made of a material with a refractive index less than 1.5. This low refractive index material results in less deflection of light when passing through the lens, thereby reducing light propagation loss and improving the lens's transmittance. Especially in low-light environments, this design can more effectively collect and transmit light, significantly enhancing the brightness of the image. Furthermore, the second lens has an Abbe coefficient greater than 70. A material with a high Abbe coefficient effectively reduces chromatic aberration, resulting in clearer images and more accurate colors. Simultaneously, the lens has a relative partial dispersion greater than 0.0035, a parameter describing the material's dispersion characteristics within a specific wavelength range. Materials with high relative partial dispersion help correct the second-order spectrum, that is, further reducing the focusing differences of different wavelengths of light after eliminating primary chromatic aberration, thereby improving image quality. By selecting materials with high Abbe coefficients and high relative partial dispersion, chromatic aberration can be controlled more precisely, allowing light of different wavelengths to be focused more accurately at the same position after passing through the lens, significantly improving image clarity and color accuracy. This is especially important for low-light imaging lenses, because high-quality imaging is crucial for obtaining clear and accurate images in low-light environments.

[0078] The third lens satisfies the following condition:

[0079] Nd3>1.8, Vd3<30

[0080] Where Nd3 is the refractive index of the third lens, and Vd3 is the Abbe coefficient of the third lens. High-refractive-index lens materials are generally more effective at converging light, meaning that lenses can be designed to be thinner while maintaining the same optical performance. This design not only helps reduce the thickness and weight of the lens but also improves the uniformity of thickness at the lens edges, thereby enhancing the overall performance of the optical system. Low-Abbe coefficient materials produce greater chromatic aberration during imaging, leading to blurring and color distortion. However, when a low-Abbe coefficient lens is combined with another high-Abbe coefficient lens (the second lens), chromatic aberration can be more precisely controlled through the mutual cancellation of positive and negative dispersion.

[0081] As an optional embodiment (Example 3), the second lens group L2 consists of two lenses, sequentially including a negative refractive index lens L21 and a positive refractive index lens L22 from the object side to the image side; the positive refractive index lens L21 and the negative refractive index lens L22 form a second cemented lens G2; the negative refractive index lens L21 has a concave object side and a concave image side; the positive refractive index lens L22 has a convex object side. By cementing the positive and negative refractive index lenses together, chromatic aberration can be effectively corrected. When light of different wavelengths passes through a lens, dispersion occurs due to their different refractive indices, resulting in color spots or colored edges in the image. This dispersion phenomenon is due to the change in the speed of light propagation in the medium with wavelength, causing different wavelengths of light to refract at different angles in the lens. By cementing the positive and negative refractive index lenses together tightly, light of different wavelengths can reconverge at the same point after passing through the lens, thereby eliminating chromatic aberration and significantly improving image quality. In high-precision optical systems, it helps to obtain clear and accurate images.

[0082] As another alternative embodiment (Example 1 and Example 2), the second lens group L2 consists of fewer than two lenses, including a positive refractive index lens L21; this positive refractive index lens L21 has a concave object-side surface and a convex image-side surface. The concave-convex lens design can effectively reduce aberrations, especially spherical aberration and coma, improving image quality. By optimizing the curvature and shape of the lens, the concave-convex lens can better control the path of light, making the light more evenly distributed as it passes through the lens, reducing light scattering and loss, thereby improving the efficiency of the optical system.

[0083] In this optional embodiment (Example 1 and Example 2), the third lens group L3 consists of a positive refractive index lens L31 and a negative refractive index lens L32, sequentially arranged from the object side to the image side; the object side of the positive refractive index lens L31 is convex, and the object side of the negative refractive index lens L32 is concave. The combination of the positive and negative refractive index lenses in the third lens group can effectively correct chromatic aberration. The positive refractive index lens converges light rays, while the negative refractive index lens diverges light rays. Through this interaction, the focusing point of light rays of different wavelengths can be controlled more precisely, thereby reducing chromatic aberration and improving the color accuracy of the image. Specifically, the positive refractive index lens is mainly responsible for converging light rays to a single focal point, while the negative refractive index lens corrects the chromatic aberration introduced by the positive refractive index lens through its diverging effect, allowing light rays of different wavelengths to be focused more accurately at the same position. The positive refractive index lens can also reduce spherical aberration, while the negative refractive index lens can reduce field curvature and distortion. By rationally designing the shape and materials of the lens, not only can better imaging results be achieved, but the compactness and lightness of the lens system can also be maintained.

[0084] Among them, the positive refractive index lenses of the second lens group satisfy the following condition:

[0085] Nd4>1.9, Vd4<20, ΔPg,F>0.0035

[0086] Where Nd₄ is the refractive index of the positive refractive lens, Vd₄ is the Abbe coefficient of the positive refractive lens, and ΔPg,F is the relative partial dispersion of the positive refractive lens. High refractive index lens materials can generally converge light more effectively, allowing lenses to be designed to be thinner while maintaining the same optical performance. This design not only helps reduce the thickness and weight of the lens but also improves the edge thickness uniformity of the lens, thereby enhancing the overall performance of the optical system. High refractive index materials in optical systems can effectively control the refraction angle of light, reduce light scattering and loss, and thus improve image quality. Using high refractive index, low dispersion materials can effectively control the refraction angle of light, significantly improving image quality. Relative partial dispersion is an important parameter describing the dispersive characteristics of a material within a specific wavelength range. Together with the Abbe coefficient, it allows for more precise control of chromatic aberration. Materials with high relative partial dispersion help correct the second-order spectrum, that is, after eliminating primary chromatic aberration, further reducing the focusing differences of light at different wavelengths, thereby significantly improving image quality.

[0087] The positive and negative refractive index lenses of the third lens group satisfy the following condition:

[0088] Nd5<1.7, Vd5>55, Nd6>1.72, Vd6<30

[0089] Wherein, Nd5 is the refractive index of the positive refractive index lens, Vd5 is the Abbe coefficient of the positive refractive index lens, and Nd6 is the refractive index of the positive refractive index lens, and Vd6 is the Abbe coefficient of the positive refractive index lens. Using a positive power optical lens can effectively control the refraction angle of light, especially when placed at the rear of the lens, significantly improving the direction of light and thus reducing the aperture at the rear of the lens. Furthermore, using high-refractive-index, low-dispersion materials can further precisely control the refraction angle of light, effectively improving image quality and helping to reduce the outer diameter at the rear of the lens. The materials of the last three lenses are heavy flint glass, lanthanum crown glass, and heavy flint glass, respectively. This high-low-high optical material combination allows light to transition more evenly to the imaging surface, reducing light scattering and loss. Uniform light transition not only reduces the lens's sensitivity to tolerances but also ensures high image quality while maintaining lens miniaturization. This design can significantly improve image quality without increasing system complexity and weight, and is particularly suitable for applications requiring high resolution, low chromatic aberration, and low illumination.

[0090] A detailed description of the lens according to each example will now be given. In the following three examples, the ratio of image height to optical back length satisfies 0.2 < H / TTL < 0.3, which is beneficial for the optical lens to balance miniaturization design and improve imaging quality. Further, in the following three examples, the ratio of optical back focal length to optical back length satisfies 0.2 < BFL / TTL < 0.3 to balance the improvement of relative illumination of the system and miniaturization design.

[0091] Example 1

[0092] For the optical structure of Example 1, please refer to Figure 1 , and the specific parameters of this Example 1 are shown in Tables 1 and 2 below. In this Example 1, the lens aperture is set on the object side of the second lens. The focal length f of this optical system is 70 mm, the aperture FNO is 1.8, the field angle FOV is 7.18°, the target size IMH is 8.81 mm, and the total optical length TTL is 78 mm.

[0093] Table 1 Data Sheet of Example 1

[0094]

[0095]

[0096] Table 2 Parameter Table of Example 1

[0097] Parameter Description parameter Example 1 focal length f 70 Like Gao H 8.81 Optical back focal length BFL 11.30 Overall optical length TTL 78.00 H / TTL 0.11 BFL / TTL 0.14 Tongguang FNO FNO 1.6 Field of view (FOV) FOV 7.18

[0098] Please refer to Figure 2 , the MTF graph of Example 1 under visible light of 435 - 650 nm. At a field angle FOV = 7.18° and a target size IMH = 8.81 mm, the MTF value is greater than 0.15 at a frequency of 250 lp / mm and greater than 0.5 at a frequency of 125 lp / mm, indicating that this example has high resolution, good imaging quality, and high mid - frequency and high - frequency. Please refer to Figure 3 , the MTF curve graph of Example 1 at near - infrared 850 nm. At a field angle FOV = 7.18° and a target size IMH = 8.81 mm, the MTF value is greater than 0.35 at a frequency of 250 lp / mm and greater than 0.6 at a frequency of 125 lp / mm, indicating that this example has high resolution, good imaging quality, and high mid - frequency and high - frequency. Please refer to Figure 4 , the MTF curve graph of Example 1 at near - infrared 940 nm. At a field angle FOV = 7.18° and a target size IMH = 8.81 mm, the MTF value is greater than 0.3 at a frequency of 250 lp / mm and greater than 0.55 at a frequency of 125 lp / mm, indicating that this example has high resolution, good imaging quality, and high mid - frequency and high - frequency. Please refer to Figure 5Example 1 shows the distortion map for visible light (435-650nm). The edge field-of-view distortion values ​​are all less than ±0.5%, and the optical distortion across the entire field of view is small, resulting in excellent imaging quality and high image fidelity. Please refer to... Figure 6 Example 1 shows the longitudinal chromatic aberration curve (magnification chromatic aberration diagram) for visible light (435-650nm), representing the chromatic aberration of the lens as the field of view changes. The five lines correspond to wavelengths of 0.435µm, 0.51µm, 0.55µm, 0.61µm, and 0.65µm, respectively. The horizontal axis represents the chromatic aberration value, and the vertical axis represents the normalized field of view angle. The longitudinal chromatic aberration (magnification chromatic aberration) across the entire field of view is less than 2µm. In such a large target surface and high-throughput optical system, the chromatic aberration is negligible and can therefore be termed "zero chromatic aberration." Please refer to [link to relevant documentation]. Figure 7 Example 1 shows a dot plot in the visible light 435-650nm range. The RMS value across the entire field of view is less than 3µm. The more compact the dot plot, the fewer the aberrations present. Please refer to... Figure 8 The relative illumination diagram of visible light 435-650nm in Example 1 shows that the lens maintains a relative illumination greater than 95% while ensuring a target half-image height of 4.405.

[0099] Example 2

[0100] Please refer to the optical structure of Example 2. Figure 9 The specific parameters of Example 2 are shown in Tables 3 and 4 below. In Example 2, the lens stop is located on the side of the second lens. The optical system has a focal length f = 70 mm, a light transmission FNO = 1.8, a field of view FOV = 7.12, a target surface size IMH = 8.81 mm, and a total optical length TTL = 77.61 mm.

[0101] Table 3 Example 2 Data Table

[0102]

[0103] Table 4 Example 2 Parameter Table

[0104] Parameter Description parameter Example 2 focal length f 70 Like Gao H 8.81 Optical back focal length BFL 11.12 Overall optical length TTL 77.61 H / TTL 0.11 BFL / TTL 0.14 Tongguang FNO FNO 1.6 Field of view (FOV) FOV 7.12

[0105] Please see Figure 10 Example 2, with its visible light MTF plot at 435-650 nm, shows an MTF value greater than 0.15 at 250 lp / mm and greater than 0.4 at 125 lp / mm, with a field of view (FOV) of 7.12° and a target size (IMH) of 8.81 mm. This indicates high resolution and good imaging quality, though slightly inferior to Example 1. Please refer to... Figure 11Example 2's near-infrared 850nm MTF curve, with a field of view (FOV) of 7.12° and a target size (IMH) of 8.81 mm, shows an MTF value greater than 0.28 at 250 lp / mm and a MTF value greater than 0.55 at 125 lp / mm. This indicates that this example has high resolution, good imaging quality, and high mid- and high-frequency performance, but the MTF convergence across all fields of view is weaker than in Example 1. Please refer to... Figure 12 Example 2's near-infrared 940nm MTF curve, with a field of view (FOV) of 7.12° and a target size (IMH) of 8.81mm, shows an MTF value greater than 0.25 at 250 lp / mm and a MTF value greater than 0.5 at 125 lp / mm. This indicates that this example has high resolution, good imaging quality, and high performance at both the mid- and high-frequency ranges. Please refer to [link / reference]. Figure 13 Example 2 shows the distortion map for visible light (435-650nm). The edge field-of-view distortion values ​​are all less than ±0.5%, and the optical distortion across the entire field of view is small, resulting in excellent imaging quality and high image fidelity. Please refer to... Figure 14 Example 2 shows the longitudinal chromatic aberration curve (magnification chromatic aberration diagram) for visible light (435-650nm), representing the chromatic aberration of the lens as the field of view changes. The five lines correspond to wavelengths of 0.435µm, 0.51µm, 0.55µm, 0.61µm, and 0.65µm, respectively. The horizontal axis represents the chromatic aberration value, and the vertical axis represents the normalized field of view angle. The longitudinal chromatic aberration (magnification chromatic aberration) across the entire field of view is less than 2µm. In such a large target surface and high-throughput optical system, the chromatic aberration is negligible and can therefore be termed "zero chromatic aberration." Please refer to [link / reference]. Figure 15 Example 2 shows the dot plots in the visible light 435-650nm range. The RMS across the entire field of view is less than 3.65µm. The more compact the dot plot, the fewer the aberrations. Please refer to... Figure 16 The relative illumination diagram of visible light 435-650nm in Example 2 shows that the lens maintains a relative illumination greater than 95% while ensuring a target half-image height of 4.405.

[0106] Example 3

[0107] Please refer to the optical structure of Example 3. Figure 17 The specific parameters of Example 3 are shown in Tables 5 and 6 below. In Example 3, the lens stop is located on the side of the first lens. The optical system has a focal length f = 70 mm, a light transmission FNO = 1.8, a field of view FOV = 7.14°, a target surface size IMH = 8.81 mm, and a total optical length TTL = 78 mm.

[0108] Table 5 Example 3 Data Table

[0109]

[0110]

[0111] Table 6 Example 3 Parameter Table

[0112] Parameter Description parameter Example 3 focal length f 70 Like Gao H 8.81 Optical back focal length BFL 14.42 Overall optical length TTL 78.00 H / TTL 0.11 BFL / TTL 0.18 Tongguang FNO FNO 1.6 Field of view (FOV) FOV 7.14

[0113] Please see Figure 18 Example 3 shows the MTF (Mean Transmission Format) plot in the visible light range of 435-650 nm. With a field of view (FOV) of 7.14° and a target size (IMH) of 8.81 mm, the MTF value is greater than 0.2 at 250 lp / mm and greater than 0.5 at 125 lp / mm. This indicates that this example has high resolution, good imaging quality, and high performance at both the mid- and high-frequency ranges. Please refer to [link / reference]. Figure 19 Example 3 shows the near-infrared 850nm MTF curve. At a field of view (FOV) of 7.14° and a target size (IMH) of 8.81 mm, the MTF value is greater than 0.4 at 250 lp / mm and greater than 0.7 at 125 lp / mm. This indicates that this example has high resolution, good imaging quality, and high performance at both the mid- and high-frequency ranges. Please refer to [link / reference]. Figure 20 Example 3's near-infrared 940nm MTF curve, with a field of view (FOV) of 7.14° and a target size (IMH) of 8.81mm, shows an MTF value greater than 0.38 at 250 lp / mm and a MTF value greater than 0.6 at 125 lp / mm. This indicates that this example has high resolution, good imaging quality, and high performance at both the mid- and high-frequency ranges. Please refer to... Figure 21 Example 3 shows the distortion map for visible light (435-650nm). The edge field-of-view distortion values ​​are all less than ±1.5%, and the optical distortion across the entire field of view is small, resulting in excellent imaging effect and high image fidelity. Please refer to... Figure 22 Example 3 shows the longitudinal chromatic aberration curve (magnification chromatic aberration diagram) for visible light (435-650nm), representing the chromatic aberration of the lens as the field of view changes. The five lines correspond to wavelengths of 0.435µm, 0.51µm, 0.55µm, 0.61µm, and 0.65µm, respectively. The horizontal axis represents the chromatic aberration value, and the vertical axis represents the normalized field of view angle. The longitudinal chromatic aberration (magnification chromatic aberration) across the entire field of view is less than 2.5µm. In such a large target surface and high-throughput optical system, the chromatic aberration is negligible and can therefore be termed "zero chromatic aberration." Please refer to [link / reference]. Figure 23 The dot plot of Example 3 in the visible light 435-650nm range shows an RMS value of less than 5.5µm across the entire field of view. This dot plot is larger than those in Examples 1 and 2, indicating that Example 3 exhibits greater aberrations in the visible light range. Please refer to... Figure 24 The relative illumination diagram of visible light 435-650nm in Example 3 shows that the lens maintains a relative illumination greater than 95% while ensuring a target half-image height of 4.405.

[0114] Based on Examples 1 to 3, this case has the following advantages:

[0115] 1. The optical lens of this invention achieves a light transmission of F1.6, resulting in excellent imaging and clear image quality. Furthermore, the large aperture provides superior low-light performance and a shallow depth of field, making it adaptable to a wider range of shooting environments. The lens itself also boasts a compact structure, offering superior portability compared to other lenses on the market.

[0116] 2. The lens wavelength range of this solution is 435-940 nm; it meets the application requirements of special scenarios and covers the need for clear imaging in all weather conditions.

[0117] 3. The lens in this solution uses 7 pieces of ground spherical glass and mostly uses cemented lenses, resulting in a simple optical path structure, which is easy to assemble and has a high optical assembly yield.

[0118] 4. The lens of this invention uses six ground spherical lenses. The selection of relatively inexpensive optical materials during the lens design stage significantly increases production profits by controlling costs. Furthermore, using fewer lenses reduces optical assembly complexity and simplifies the manufacturing process.

[0119] 5. By carefully selecting the combination of lens materials and lens shapes, we aim to meet the high requirements and standards of reliability testing for civilian rifle sights, civilian observation sights, and even military rifle sights, thereby reducing the difficulty of optical assembly and simplifying the manufacturing process.

[0120] 6. The optical lens of this invention can withstand vibrations of 10Hz to 150Hz to 10Hz. After the IEC600068-2-6 test, its appearance and imaging are normal, and there is no dust.

[0121] 7. The optical lens of this invention has an impact resistance of 1200G pulse duration of 0.4ms, half-sine wave, 3 times in the Z direction, powered on, with battery. Simulated shooting test; the product is powered on, impact acceleration: 1200G, 100 times in the optical axis direction, after the test, the appearance and imaging are normal, no dust.

[0122] Example 4

[0123] For reference Figure 25 A description of an electronic device A according to Example 4 of the present invention will be given. Figure 25 This is a schematic diagram of an electronic device used in a camera optical system for any of the low-light imaging lenses according to Examples 1 to 3.

[0124] exist Figure 25 In the figures, reference numeral A2 indicates the main body of the electronic device, and reference numeral A1 indicates any of the camera optical systems (interchangeable lenses) including the low-light imaging lenses according to Examples 1 to 3. Reference numeral A3 indicates an image sensor (photoelectric conversion element) such as a CMOS image sensor or a CCD image sensor, which is built into the camera body A2 and receives light (the optical image formed by the camera optical system A1) from the camera optical system A1 and performs photoelectric conversion.

[0125] By using the low-light imaging lens according to any one of Examples 1 to 3 in an electronic device such as a digital still camera, an electronic device with a low-light imaging lens having high optical performance can be obtained.

[0126] Each example can provide electronic devices with high optical performance.

[0127] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims will be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A low-light imaging lens, characterized in that, From the object side to the image side, the lenses are arranged in the order of the first lens group, the second lens group, and the third lens group. The first lens group consists of a positive refractive index lens and a set of first cemented lenses in sequence from the object side to the image side. The first cemented lenses are composed of a positive refractive index lens and a negative refractive index lens. The second lens group consists of two or fewer lenses, including at least one positive refractive index lens; The third lens group consists of a positive refractive index lens and a negative refractive index lens; The lens is composed of six or seven lenses with optical power; wherein, The six lenses with optical power are arranged from the object side to the image side as follows: The first lens has positive refractive power, and the object-side surface is convex, as is the image-side surface; The second lens has positive refractive power, and the object side is convex, as is the image side; The third lens has negative refractive power, and both the object-side and image-side surfaces are concave. The fourth lens has positive refractive power, with a concave object side and a convex image side; The fifth lens has positive refractive power, with a convex object-side surface and a concave image-side surface; The sixth lens has negative refractive power and its object-side surface is concave. The second lens and the third lens are cemented together; The seven lenses with optical power are arranged from the object side to the image side as follows: The first lens has positive refractive power, and the object-side surface is convex, as is the image-side surface; The second lens has positive refractive power, and the object side is convex, as is the image side; The third lens has negative refractive power, and both the object-side and image-side surfaces are concave. The fourth lens has negative refractive power, and both the object-side and image-side surfaces are concave. The fifth lens has positive refractive power, with a convex object-side surface and a flat image-side surface; The sixth lens has negative refractive power, with a convex object-side surface and a concave image-side surface; The seventh lens has positive refractive power, with a convex object-side surface and a flat image-side surface; The second lens and the third lens are cemented together, and the fourth lens and the fifth lens are cemented together.

2. The low-light imaging lens as described in claim 1, characterized in that, The first lens group includes a first lens, a second lens, and a third lens in sequence from the object side to the image side; the second lens and the third lens form a first cemented lens. The first lens is a biconvex positive power lens; The second lens has positive refractive power and its object-side surface is convex. The third lens has a negative refractive index and its object-side surface is concave.

3. A low-light imaging lens as described in claim 2, characterized in that, The lens satisfies the following condition: in, Let be the refractive index of the second lens. The Abbe coefficient of the second lens. Relative partial dispersion.

4. A low-light imaging lens as described in claim 3, characterized in that, The lens satisfies the following condition: in, Let be the refractive index of the third lens. is the Abbe coefficient of the third lens.

5. A low-light imaging lens as described in claim 1, characterized in that, The second lens group consists of two lenses, which, from the object side to the image side, include a negative refractive index lens and a positive refractive index lens in sequence; the positive refractive index lens and the negative refractive index lens together form the second cemented lens; This negative refractive index lens has a concave object side and a concave image side. This positive refractive lens has a convex side.

6. A low-light imaging lens as described in claim 1, characterized in that, The second lens group consists of fewer than two lenses, including a positive refractive index lens; the positive refractive index lens has a concave object side and a convex image side.

7. A low-light imaging lens as described in claim 6, characterized in that, The third lens group consists of a positive refractive index lens and a negative refractive index lens in sequence from the object side to the image side; the object side of the positive refractive index lens is convex, and the object side of the negative refractive index lens is concave.

8. A low-light imaging lens as described in claim 7, characterized in that, The positive refractive index lenses of the second lens group satisfy the following condition: in, Let be the refractive index of the positive refractive lens. This is the Abbe coefficient of the positive refractive index lens. This refers to the relative partial dispersion of the positive refractive index lens.

9. A low-light imaging lens as described in claim 7 or 8, characterized in that, The positive and negative refractive index lenses of the third lens group satisfy the following condition: in, Let be the refractive index of the positive refractive lens. This is the Abbe coefficient of the positive refractive index lens. Let be the refractive index of the positive refractive lens. Let be the Abbe coefficient of the positive refractive index lens.

10. An electronic device, characterized in that, A low-light imaging lens according to any one of claims 1-9; and An image sensor is configured to receive an image formed by the low-light imaging lens.

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