Low-illumination imaging lens and electronic equipment

Abstract

The invention 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 index lens and a group of first balsaming lenses from the object side to the image side, and the first balsaming lenses comprise a positive refractive index lens and a negative refractive index lens; the second lens group is composed of two or less than two lenses and comprises at least one positive refractive index lens; the third lens group is composed of a positive refractive index lens and a negative refractive index lens. The optical lens provided by the invention has the advantages that the light transmission reaches F1.6, the imaging is excellent, the image quality is clear, the large aperture brings excellent low-illumination processing capability and small depth of field, the optical lens can adapt to more shooting environments, the structure of the lens is compact, and the portability is superior to that of the lens in the market.

Description

Technical Field

[0001] The present invention relates to the technical field of low-illuminance imaging lenses, and in particular to a low-illuminance imaging lens and electronic equipment. Background Art

[0002] A low-light imaging lens is a special lens that can produce clear images in low-light environments, such as at night or in a dark room. It has at least one of the following disadvantages:

[0003] 1) The general lens has a small light transmission rate and low energy utilization rate, and cannot meet the ability to distinguish objects in low-light environments;

[0004] 2) The general lens has a small spectral range and a single use environment, which cannot meet the requirements of all-weather use environment;

[0005] 3) General lenses cannot pass the impact, vibration and other reliability test conditions. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a low-light imaging lens and an electronic device. The lens can solve at least one technical disadvantage mentioned in the background technology.

[0007] According to one aspect of the present invention, a low illumination imaging lens is provided, which comprises a first lens group, a second lens group, and a third lens group in order from the object side to the image side;

[0008] The first lens group includes, from the object side to the image side, a positive refractive power lens and a group of first cemented lenses, wherein the first cemented lens is composed of a positive refractive power lens and a negative refractive power lens;

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

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

[0011] In the above technical solution, the first lens group is composed of a positive refractive power lens and a group of first cemented lenses, and the first cemented lens is formed by cementing a positive refractive power lens and a negative refractive power lens. The positive refractive power lens has a converging effect on light, which can make the light converge initially and form a clearer image; the combination of positive and negative refractive power lenses in the cemented lens is mainly used to correct chromatic aberration. The different refractive indices of light of different wavelengths when passing through the lens will cause dispersion phenomenon, so that the image has color spots or color edges. The cemented lens can effectively eliminate this chromatic aberration and improve the imaging quality. The second lens group is composed of two or less than two lenses, including at least one positive refractive power lens. The positive refractive power 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 the loss of light between lenses, improve the transmittance of light, and enhance the imaging ability of the lens in low-light environments. The third lens group is composed of a positive refractive power lens and a negative refractive power lens. The positive refractive index lens continues to play the role of converging light, while the negative refractive index lens appropriately diverges the light. The two work together to further correct aberrations, such as spherical aberration and coma, to make the image more perfect and improve the image quality of the lens. The optical lens has a clear aperture of F1.6. The large aperture allows the lens to receive more light per unit time, so that it can obtain sufficient exposure in low-light environments, making the image clear and bright, and can adapt to more shooting environments, such as night and indoor dark light scenes. Thanks to the reasonable design and combination of the lens group, various aberrations can be effectively corrected and imaging defects can be reduced. At the same time, the small depth of field effect brought by the large aperture can adapt to more shooting environments, and the lens itself has a compact structure and is more portable than similar lenses on the market. The lens wavelength range is 435-940nm, covering visible light and part of the near-infrared band, meeting the application requirements of special scenes, and can achieve clear imaging all day long. Light of different wavelengths has different penetration and reflection characteristics. Lenses with a wide wavelength range can better adapt to these complex environments and obtain richer image information. The lenses in this solution all use ground spherical glass lenses. The processing technology of spherical lenses is relatively mature, the cost is low, and the optical path structure is simple and easy to assemble. The surface accuracy of the ground spherical glass lens is high, which can ensure the good propagation of light in the lens, reduce the scattering and loss of light, and improve the imaging quality. At the same time, the simple optical path structure and the characteristics of easy assembly are also conducive to improving the optical assembly yield and reducing production costs. After testing, the optical lens can withstand vibrations of 10Hz~150Hz~10Hz displacement of 0.15mm, which meets the IEC60068-2-6 standard. After the test, the appearance of the image is normal and there is no dust, which shows that the lens has good stability and reliability in a vibrating environment, and will not cause the lens to shift, loosen or generate dust due to vibration, which affects the imaging quality.In addition, the lens has an impact resistance level of 1200G, a pulse duration of 0.4ms, a half-sine wave, 3 impacts in the Z direction, powered on and with a battery, and after a simulated gun shooting test, the product appearance and imaging are normal, with no dust, indicating that when the lens is subjected to a strong impact, its structure is still firm and can maintain normal operation. It is suitable for use in some occasions that require high impact resistance of the lens, such as military and outdoor adventures.

[0012] In some embodiments, the first lens group includes a first lens, a second lens, and a third lens in order from the object side to the image side; the second lens and the third lens form 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 power, and the object side surface is a concave surface.

[0016] In the above technical solution, the first lens is a biconvex positive power lens. The shape of the biconvex lens enables the light to converge from both sides to the center when passing through the lens, and has a strong ability to converge light. Positive power means that the lens has a converging effect on light, which can make parallel light converge at one point to form a real image. Selecting a biconvex positive power lens as the first lens is conducive to compressing the front aperture of the optical system and helping to achieve the miniaturization of the lens. At the same time, the symmetrical structure of the biconvex lens is also conducive to controlling distortion, reducing image deformation, and facilitating the realization of distortion-free lenses. The second lens has positive refractive power, and the object side is convex. It cooperates with the first lens to further enhance the convergence of light and improve the brightness and clarity of the image. It cooperates 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, and the object side is concave. It is glued with the second lens to form a first glued lens. The interaction of positive and negative refractive powers can effectively correct chromatic aberration, make light of different wavelengths converge at one point again, eliminate dispersion, and make the image clear and the color accurate. The glued design simplifies the optical path structure, reduces light reflection and scattering, improves light transmittance, enhances low-light imaging capabilities, and reduces the size and weight of the lens, making it compact and portable. The glued lens structure is stable and not easily affected by external factors, ensuring stable imaging quality, and is 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] Wherein, 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 above technical solution, the second lens uses a material with a refractive index less than 1.5. This low refractive index material makes the light less deflected when passing through the lens, thereby reducing the propagation loss of the light in the lens and improving the transmittance of the lens. Especially in low-light environments, this design can collect and transmit light more effectively, significantly enhancing the brightness of the image. In addition, the Abbe coefficient of the second lens is greater than 70. The material with a high Abbe coefficient can effectively reduce chromatic aberration, making the image clearer and the color more accurate. At the same time, the relative partial dispersion of the lens is greater than 0.0035. This parameter describes the dispersion characteristics of the material within a specific wavelength range. Materials with high relative partial dispersion help to correct the secondary spectrum, that is, on the basis of eliminating primary chromatic aberration, further reduce the focusing difference of light of different wavelengths, thereby improving the image quality. By selecting materials with high Abbe coefficients and high relative partial dispersion, chromatic aberration can be controlled more accurately, so that light of different wavelengths can be more accurately focused on the same position after passing through the lens, significantly improving the clarity and color accuracy of the image. This is particularly important for low-light imaging lenses, because in low-light environments, high-quality imaging is essential for obtaining clear and accurate images.

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

[0022] Nd3>1.8, Vd3<30

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

[0024] In the above technical solution, lens materials with high refractive index are generally able to focus light more effectively, which means that under the same optical performance requirements, the lens can be designed to be thinner. This design not only helps to reduce the thickness and weight of the lens, but also improves the uniformity of the edge thickness of the lens, thereby improving the overall performance of the optical system. Materials with low Abbe coefficients will produce larger chromatic aberrations when imaging, which will cause blurred imaging and color distortion. However, when a lens with a low Abbe coefficient is used in combination with another lens with a high Abbe coefficient (the second lens), the chromatic aberration can be controlled more accurately by offsetting the positive and negative dispersions.

[0025] In some embodiments, the second lens group is composed of two lenses, including a negative refractive power lens and a positive refractive power lens in order from the object side to the image side; the positive refractive power lens and the negative refractive power lens form a second cemented lens;

[0026] The negative refractive power lens has a concave object side surface and a concave image side surface;

[0027] The positive refractive power lens has a convex object side surface.

[0028] In the above technical solution, chromatic aberration can be effectively corrected by bonding 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 color edges when imaging. This dispersion phenomenon is due to the fact that the propagation speed of light in the medium changes with the wavelength, resulting in different wavelengths of light having different refraction angles in the lens. The bonded lens tightly bonds the positive refractive index lens and the negative refractive index lens together, so that light of different wavelengths can converge at the same point after passing through the lens, thereby eliminating chromatic aberration and significantly improving the imaging quality. In high-precision optical systems, it helps to obtain clear and accurate images.

[0029] In some embodiments, the second lens group is composed of less than two lenses, including a positive refractive power lens; the positive refractive power lens has a concave object side surface and a convex image side surface.

[0030] In the above technical solution, the concave-convex lens design can effectively reduce aberrations, especially spherical aberration and coma aberration, and improve imaging 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 includes a positive refractive power lens and a negative refractive power lens in sequence from the object side to the image side; the object side surface of the positive refractive power lens is convex; and the object side surface of the negative refractive power lens is concave.

[0032] In the above technical solution, the combination of the positive refractive power lens and the negative refractive power lens in the third lens group can effectively correct chromatic aberration. The positive refractive power lens converges light, while the negative refractive power lens diverges light. Through this interaction, the focusing point of light of different wavelengths can be controlled more accurately, thereby reducing chromatic aberration and improving the color accuracy of imaging. Specifically, the positive refractive power lens is mainly responsible for converging the light to a focal point, while the negative refractive power lens corrects the chromatic aberration introduced by the positive refractive power lens through divergence, so that light of different wavelengths can be more accurately focused on the same position. The positive refractive power lens can also reduce spherical aberration, while the negative refractive power lens can reduce field curvature and distortion. By rationally designing the shape and material of the lens, not only can better imaging effects be achieved, but also the compactness and lightness of the lens system can be maintained.

[0033] In some embodiments, the positive refractive power lens of the second lens group satisfies the following conditional formula:

[0034] Nd4>1.9, VD4<20, ΔPg,F>0.0035

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

[0036] In the above technical solution, lens materials with high refractive index are usually able to converge light more effectively, so that the lens can be designed to be thinner under the same optical performance. This design not only helps to reduce the thickness and weight of the lens, but also improves the uniformity of the edge thickness of the lens, thereby improving the overall performance of the optical system. High refractive index materials can effectively control the deflection angle of light in the optical system, reduce the scattering and loss of light, and thus improve the imaging quality. The use of high refractive index and low dispersion materials can effectively control the deflection angle of light and significantly improve the imaging quality. Relative partial dispersion is an important parameter that describes the dispersion characteristics of a material within a specific wavelength range. Together with the Abbe coefficient, chromatic aberration can be controlled more accurately. Materials with high relative partial dispersion help to correct the secondary spectrum, that is, on the basis of eliminating primary chromatic aberration, further reduce the focusing differences of light of different wavelengths, thereby significantly improving the imaging quality.

[0037] In some embodiments, the positive refractive power lens and the negative refractive power lens of the third lens group satisfy the following conditional formula:

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

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

[0040] In the above technical solution, the use of a positive optical lens can effectively control the deflection angle of light, especially when it is placed at the rear end of the lens, it can significantly improve the direction of light, thereby reducing the aperture of the rear end of the lens. In addition, the use of high refractive index and low dispersion materials can further accurately control the deflection angle of light, effectively improve the imaging quality, and help reduce the outer diameter of the rear end 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 combination of optical materials can make the light transition to the imaging surface more evenly, reducing the scattering and loss of light. The uniform light transition not only reduces the sensitivity of the lens to tolerances, but also ensures high standards of imaging quality while maintaining the miniaturization of the lens. This design can significantly improve the imaging quality without increasing the complexity and weight of the system, and is especially suitable for application scenarios requiring high resolution, low chromatic aberration, and low illumination.

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

[0042] The image sensor is configured to receive the image formed by the low illumination imaging lens.

[0043] In the above technical solution, the advantages of the electronic device rely on the low-light imaging lens, which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

[0046] Figure 2 This is the MTF diagram of Example 1 of the low-light imaging lens 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 illumination imaging lens of the present invention;

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

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

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

[0051] Figure 7 This is a point diagram of Example 1 of the low-light imaging lens of the present invention under visible light 435-650nm;

[0052] Figure 8 This is a relative illumination diagram of Example 1 of the low illumination imaging lens of the present invention under visible light 435-650nm;

[0053] Fig. 9 2 is a schematic diagram of the structure of a low-light imaging lens example 2 of the present invention;

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

[0055] Fig.11 This is a near infrared 850nm MTF curve of Example 2 of the low illumination imaging lens of the present invention;

[0056] Fig.12 This is a near infrared 940nm MTF curve of Example 2 of the low illumination imaging lens of the present invention;

[0057] Fig.13 This is a distortion diagram of Example 2 of the low-light imaging lens of the present invention under visible light 435-650nm;

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

[0059] Fig.15 This is a point diagram of Example 2 of the low-light imaging lens of the present invention under visible light 435-650nm;

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

[0061] Fig.17 1 is a schematic diagram of the structure of Example 3 of the low-light imaging lens of the present invention;

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

[0063] Fig.19 This is a near infrared 850nm MTF curve of Example 3 of the low illumination imaging lens of the present invention;

[0064] Fig. 20 This is a near infrared 940nm MTF curve diagram of Example 3 of the low illumination imaging lens of the present invention;

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

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

[0067] Fig.23 This is a point diagram of Example 3 of the low-light imaging lens of the present invention under visible light 435-650nm;

[0068] Fig.24 This is a relative illumination diagram of Example 3 of the low illumination imaging lens of the present invention under visible light 435-650nm;

[0069] Fig.25It is a schematic diagram of the structure of Example 4 of the low-illuminance imaging lens of the present invention. DETAILED DESCRIPTION

[0070] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention. Similarly, the following examples are only partial embodiments of the present invention rather than all embodiments, and all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

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

[0072] Figure 1 , Fig. 9 , Fig.17 They are cross-sectional views of low-illuminance imaging lenses (optical systems) according to Examples 1 to 3, respectively. The low-illuminance imaging lenses according to each example are used for optical devices including imaging devices such as digital cameras, digital still cameras, broadcast cameras, surveillance cameras, and 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 jth lens of the i-th lens group. STO represents an aperture (fixed aperture or visible aperture). IMA represents an image plane, and when the low-illuminance imaging lenses 1 to 3 according to each example are used for the imaging optical system of a digital camera or a 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 imaging plane IMA. .

[0073] The low-light imaging lens according to each example includes, in order from the object side to the image side: a first lens group L1, a second lens group L2, and a third lens group L3; the first lens group L1 includes, from the object side to the image side, a positive refractive power lens and a group of first cemented lenses, the first cemented lens consisting of a positive refractive power lens and a negative refractive power lens; the second lens group L2 consists of two or less than two lenses, including at least one positive refractive power lens; the third lens group L3 consists of a positive refractive power lens and a negative refractive power lens. The first lens group consists of a positive refractive power lens and a group of first cemented lenses, the first cemented lens is formed by cementing a positive refractive power lens and a negative refractive power lens. The positive refractive power lens has a converging effect on light, which can initially converge the light to form a clearer image; the combination of positive and negative refractive power lenses in the cemented lens is mainly used to correct chromatic aberration. Different wavelengths of light have different refractive indices when passing through a lens, which will lead to dispersion, causing the image to have color spots or color edges. The cemented lens can effectively eliminate this chromatic aberration and improve the image quality. The second lens group consists of two or less lenses, including at least one positive refractive power lens. The positive refractive power 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 the loss of light between lenses, improve the transmittance of light, and enhance the imaging ability of the lens in low-light environments. The third lens group consists of a positive refractive power lens and a negative refractive power lens. The positive refractive power lens continues to converge the light, while the negative refractive power lens appropriately diverges the light. The two work together to further correct the aberrations, such as correcting spherical aberration, coma, etc., to make the image more perfect and improve the imaging quality of the lens. The optical lens has a light aperture of F1.6. The large aperture allows the lens to receive more light per unit time, so that it can obtain sufficient exposure in low-light environments, making the image clear and bright, and can adapt to more shooting environments, such as nighttime and indoor dark light scenes. Thanks to the reasonable design and combination of the lens group, various aberrations can be effectively corrected and imaging defects can be reduced. At the same time, the small depth of field effect brought by the large aperture can adapt to more shooting environments, and the lens itself has a compact structure and is more portable than similar lenses on the market. The lens wavelength range is 435-940nm, covering visible light and part of the near-infrared band, meeting the application requirements of special scenes, and can achieve clear imaging all day long. Light of different wavelengths has different penetration and reflection characteristics. Lenses with a wide wavelength range can better adapt to these complex environments and obtain richer image information. The lenses of this solution all use ground spherical glass lenses. The processing technology of spherical lenses is relatively mature, the cost is low, and the optical path structure is simple and easy to assemble. The surface accuracy of the ground spherical glass lens is high, which can ensure the good propagation of light in the lens, reduce the scattering and loss of light, and improve the imaging quality. At the same time, the simple optical path structure and easy assembly characteristics are also conducive to improving the optical assembly yield and reducing production costs.After testing, the optical lens can withstand vibrations of 10Hz~150Hz~10Hz displacement of 0.15mm, which meets the IEC60068-2-6 standard. After the test, the appearance and imaging are normal and dust-free, indicating that the lens has good stability and reliability in a vibration environment, and will not cause lens displacement, looseness or dust due to vibration, which will affect the imaging quality. In addition, the lens has an impact resistance level of 1200G, a pulse duration of 0.4ms, a half-sine wave, and 3 impacts in the Z direction. It is powered on and has a battery. After the simulated gun test, the product appearance and imaging are normal and dust-free, indicating that the lens is still structurally strong and can maintain normal operation when subjected to strong impacts. It is suitable for some occasions that require high impact resistance of the lens, such as military and outdoor adventures.

[0074] Among them, the first lens group L1 includes the first lens L11, the second lens L12, and the third lens L13 in order from the object side to the image side; 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 the object side surface is convex; the third lens L13 has negative refractive power, and the object side surface is concave. The first lens is a biconvex positive power lens. The shape of the biconvex lens allows the light to converge from both sides to the center when passing through the lens, and has a strong ability to converge light. Positive power means that the lens has a converging effect on the light, which can make parallel light converge at one point to form a real image. Selecting a biconvex positive power lens as the first lens is conducive to compressing the front aperture of the optical system and helping to achieve miniaturization of the lens. At the same time, the symmetrical structure of the biconvex lens is also conducive to controlling distortion, reducing image deformation, and facilitating the realization of a distortion-free lens. The second lens has positive refractive power and a convex object side surface. It cooperates with the first lens to further enhance light convergence and improve image brightness and clarity. It cooperates 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. It is glued with the second lens to form the first glued lens. The interaction between positive and negative refractive powers can effectively correct chromatic aberration, so that light of different wavelengths converges to one point again, eliminating dispersion, and making the image clear and the color accurate. The glued 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 glued lens structure is stable and not easily disturbed by external factors, ensuring stable imaging quality. It is 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] Among them, 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 uses a material with a refractive index less than 1.5. This low refractive index material makes the light less deflected when passing through the lens, thereby reducing the propagation loss of light in the lens and improving the transmittance of the lens. Especially in low-light environments, this design can collect and transmit light more effectively, significantly enhancing the brightness of imaging. In addition, the Abbe coefficient of the second lens is greater than 70. Materials with high Abbe coefficients can effectively reduce chromatic aberration, making imaging clearer and more accurate in color. At the same time, the relative partial dispersion of the lens is greater than 0.0035. This parameter describes the dispersion characteristics of the material within a specific wavelength range. Materials with high relative partial dispersion help to correct the secondary spectrum, that is, on the basis of eliminating primary chromatic aberration, further reduce the focusing difference of light of different wavelengths, thereby improving the imaging quality. By selecting materials with high Abbe coefficients and high relative partial dispersion, chromatic aberration can be controlled more accurately, so that light of different wavelengths can be more accurately focused on the same position after passing through the lens, significantly improving the clarity and color accuracy of imaging. This is especially important for low-light imaging lenses, where high-quality imaging is critical to obtaining clear and accurate images in low-light environments.

[0078] Among them, the third lens satisfies the following conditional formula:

[0079] Nd3>1.8, Vd3<30

[0080] Among them, Nd3 is the refractive index of the third lens, and Vd3 is the Abbe coefficient of the third lens. Lens materials with high refractive index are generally able to converge light more effectively, which means that the lens can be designed to be thinner under the same optical performance requirements. This design not only helps to reduce the thickness and weight of the lens, but also improves the edge thickness uniformity of the lens, thereby improving the overall performance of the optical system. Materials with low Abbe coefficients will produce large chromatic aberrations when imaging, which will cause blurred imaging and color distortion. However, when a lens with a low Abbe coefficient is used in combination with another lens with a high Abbe coefficient (the second lens), the chromatic aberration can be controlled more accurately by offsetting the positive and negative dispersion.

[0081] As an optional embodiment (Example 3), the second lens group L2 is composed of two lenses, including a negative refractive power lens L21 and a positive refractive power lens L22 in order from the object side to the image side; the positive refractive power lens L21 and the negative refractive power lens L22 form a second cemented lens G2; the negative refractive power lens L21 has a concave object side surface and a concave image side surface; the positive refractive power lens L22 has a convex object side surface. Through the cemented combination of positive and negative refractive power lenses, chromatic aberration can be effectively corrected. When light of different wavelengths passes through a lens, due to their different refractive indices, dispersion occurs, resulting in color spots or color edges when imaging. This dispersion phenomenon is due to the fact that the propagation speed of light in the medium changes with the wavelength, resulting in different refraction angles of light of different wavelengths in the lens. The cemented lens tightly glues the positive refractive power lens and the negative refractive power lens together, so that light of different wavelengths can converge at the same point again after passing through the lens, thereby eliminating chromatic aberration and significantly improving imaging quality. In high-precision optical systems, it helps to obtain clear and accurate images.

[0082] As another optional embodiment (Example 1 and Example 2), the second lens group L2 is composed of less than two lenses, including a positive refractive power lens L21; the positive refractive power 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 aberration, and improve imaging quality. By optimizing the curvature and shape of the lens, the concave-convex lens can better control the path of light, so that the light is more evenly distributed when passing through the lens, reducing the scattering and loss of light, thereby improving the efficiency of the optical system.

[0083] In this optional embodiment (Example 1 and Example 2), the third lens group L3 is composed of a positive refractive power lens L31 and a negative refractive power lens L32 in order from the object side to the image side; the object side surface of the positive refractive power lens L31 is a convex surface; the object side surface of the negative refractive power lens L32 is a concave surface. The combination of the positive refractive power lens and the negative refractive power lens in the third lens group can effectively correct chromatic aberration. The positive refractive power lens converges light, while the negative refractive power lens diverges light. Through this interaction, the focusing point of light of different wavelengths can be more accurately controlled, thereby reducing chromatic aberration and improving the color accuracy of imaging. Specifically, the positive refractive power lens is mainly responsible for converging the light to a focus, while the negative refractive power lens corrects the chromatic aberration introduced by the positive refractive power lens through divergence, so that light of different wavelengths can be more accurately focused on the same position. The positive refractive power lens can also reduce spherical aberration, while the negative refractive power lens can reduce field curvature and distortion. By rationally designing the shape and material of the lens, not only can better imaging effects be achieved, but the compactness and lightness of the lens system can also be maintained.

[0084] Wherein, the positive refractive power lens of the second lens group satisfies the following conditional formula:

[0085] Nd4>1.9, Vd4<20, ΔPg,F>0.0035

[0086] Wherein, Nd4 is the refractive index of the positive refractive index lens, Vd4 is the Abbe coefficient of the positive refractive index lens, and ΔPg,F is the relative partial dispersion of the positive refractive index lens; lens materials with high refractive index can usually converge light more effectively, so that the lens can be designed to be thinner under the same optical performance. This design not only helps to reduce the thickness and weight of the lens, but also improves the uniformity of the edge thickness of the lens, thereby improving the overall performance of the optical system. High refractive index materials can effectively control the deflection angle of light in the optical system, reduce the scattering and loss of light, and thus improve the imaging quality. The use of high refractive index and low dispersion materials can effectively control the deflection angle of light and significantly improve the imaging quality. Relative partial dispersion is an important parameter that describes the dispersion characteristics of a material within a specific wavelength range. Together with the Abbe coefficient, chromatic aberration can be controlled more accurately. Materials with high relative partial dispersion help to correct the secondary spectrum, that is, on the basis of eliminating primary chromatic aberration, further reduce the focusing difference of light of different wavelengths, thereby significantly improving the imaging quality.

[0087] Wherein, the positive refractive power lens and the negative refractive power lens of the third lens group satisfy the following conditional formula:

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

[0089] Among them, Nd5 is the refractive index of the positive refractive index lens, Vd5 is the Abbe coefficient of the positive refractive index lens, Nd6 is the refractive index of the positive refractive index lens, and Vd6 is the Abbe coefficient of the positive refractive index lens. The use of positive optical lens can effectively control the deflection angle of light, especially when it is placed at the rear end of the lens, it can significantly improve the direction of light, thereby reducing the diameter of the rear end of the lens. In addition, the use of high refractive index and low dispersion materials can further accurately control the deflection angle of light, effectively improve the imaging quality, and help reduce the outer diameter of the rear end 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 can make the light transition to the imaging surface more evenly, reducing the scattering and loss of light. The uniform light transition not only reduces the sensitivity of the lens to tolerances, but also ensures high standards of imaging quality while maintaining the miniaturization of the lens. This design can significantly improve the imaging quality without increasing the complexity and weight of the system, and is particularly suitable for application scenarios 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 the 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 Table 1 and Table 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 of view 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 Table of Example 1

[0094]

[0095]

[0096] Table 2 Parameter Table of Example 1

[0097] Parameter Description parameter Example 1 focal length f 70 Image height H 8.81 Optical back focus BFL 11.30 Total optical length TTL 78.00 H / TTL 0.11 BFL / TTL 0.14 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 of view 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 for near-infrared 850 nm. At a field of view 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 for near-infrared 940 nm. At a field of view 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 5, Example 1's distortion diagram under visible light 435-650nm, the edge field distortion values ​​are all less than ±0.5%, the optical distortion under the full field angle is small, the imaging effect is good, and the imaging restoration degree is high. Please refer to Figure 6 , Example 1's longitudinal chromatic aberration curve (magnification chromatic aberration diagram) under visible light 435-650nm, represents the magnification chromatic aberration of the lens as the field of view changes. The five lines correspond to wavelengths 0.435um 0.51um, 0.55um, 0.61um, 0.65um respectively. The horizontal axis represents the magnification chromatic aberration value, and the vertical axis represents the normalized field of view angle. The longitudinal chromatic aberration (magnification chromatic aberration) of the entire field of view is less than 2um. In such a large target surface and large optical system, the magnification chromatic aberration is negligible, so it can be called "zero chromatic aberration". Please refer to Figure 7 , Example 1's spot diagram under visible light 435-650nm, the full field of view RMS is less than 3um. The more compact the spot diagram, the less aberration there is. Please refer to Figure 8 , the relative illumination diagram of Example 1 under visible light 435-650nm, it can be seen that the relative illumination of the lens is greater than 95% while ensuring the target half-image height of 4.405.

[0099] Example 2

[0100] For the optical structure of Example 2, please refer to Fig. 9 , the specific parameters of Example 2 are shown in Tables 3 and 4. In Example 2, the lens aperture is set on the object side of the second lens. The focal length of the optical system is f = 70mm, the light clearance FNO = 1.8, the field of view FOV = 7.12, the target surface size IMH = 8.81mm, and the total optical length TTL = 77.61mm.

[0101] Table 3 Example 2 Data Table

[0102]

[0103] Table 4 Example 2 Parameters

[0104] Parameter Description parameter Example 2 focal length f 70 Image height H 8.81 Optical back focus BFL 11.12 Total optical length TTL 77.61 H / TTL 0.11 BFL / TTL 0.14 FNO FNO 1.6 Field of view FOV FOV 7.12

[0105] See also Fig.10 , the MTF diagram of Example 2 under visible light 435-650nm, at the field of view angle FOV = 7.12°, the target surface size IMH = 8.81mm, the MTF value is greater than 0.15 at 250lp / mm frequency, and the MTF value is greater than 0.4 at 125lp / mm frequency, indicating that this example has high resolution and good imaging quality, but slightly weaker than Example 1. Please refer to Fig.11, the near-infrared 850nm MTF curve of Example 2, at the field of view angle FOV = 7.12°, the target surface size IMH = 8.81mm, the MTF value is greater than 0.28 at 250lp / mm frequency, and the MTF value is greater than 0.55 at 125lp / mm frequency, indicating that this example has high resolution, good imaging quality, high mid-frequency and high-frequency, and the degree of MTF convergence in each field of view is weaker than that of Example 1. Please refer to Fig.12 , the near infrared 940nm MTF curve of Example 2, at the field of view angle FOV = 7.12°, the target surface size IMH = 8.81mm, the MTF value is greater than 0.25 at 250lp / mm frequency, and the MTF value is greater than 0.5 at 125lp / mm frequency, indicating that this example has high resolution, good imaging quality, and high mid-frequency and high-frequency. Please refer to Fig.13 , the distortion diagram of Example 2 under visible light 435-650nm, the edge field distortion values ​​are all less than ±0.5%, the optical distortion under the full field angle is small, the imaging effect is good, and the imaging restoration degree is high. Please refer to Fig.14 , Example 2 shows the longitudinal chromatic aberration curve (magnification chromatic aberration diagram) under visible light 435-650nm, which indicates the magnification chromatic aberration of the lens as the field of view changes. The five lines correspond to wavelengths 0.435um, 0.51um, 0.55um, 0.61um, and 0.65um, respectively. The horizontal axis represents the magnification chromatic aberration value, and the vertical axis represents the normalized field of view angle. The longitudinal chromatic aberration (magnification chromatic aberration) of the entire field of view is less than 2um. In such a large target surface and large optical system, the magnification chromatic aberration is negligible, so it can be called "zero chromatic aberration". Please refer to Fig.15 , Example 2's spot diagram under visible light 435-650nm, the full field RMS is less than 3.65um. The more compact the spot diagram, the less aberration there is. Fig.16 , the relative illumination diagram of Example 2 under visible light 435-650nm, it can be seen that the relative illumination of the lens is greater than 95% while ensuring the target half-image height of 4.405.

[0106] Example 3

[0107] For the optical structure of Example 3, please refer to Fig.17 ,The specific parameters of Example 3 are shown in Table 5 and Table 6. In Example 3, the lens aperture is set on the object side of the first lens. ,The focal length of the optical system is f=70mm, the light clearance FNO=1.8, the field of view angle FOV=7.14°, the target surface size IMH=8.81mm, and the total optical length TTL=78mm.

[0108] Table 5 Example 3 data table

[0109]

[0110]

[0111] Table 6 Example 3 Parameters

[0112] Parameter Description parameter Example 3 focal length f 70 Image height H 8.81 Optical back focus BFL 14.42 Total optical length TTL 78.00 H / TTL 0.11 BFL / TTL 0.18 FNO FNO 1.6 Field of view FOV FOV 7.14

[0113] See also Fig.18 The MTF diagram of Example 3 under visible light 435-650nm, with field of view angle FOV = 7.14° and target surface size IMH = 8.81mm, has an MTF value greater than 0.2 at 250lp / mm frequency and a MTF value greater than 0.5 at 125lp / mm frequency, indicating that this example has high resolution, good imaging quality, and high mid-frequency and high-frequency. Fig.19 , the near infrared 850nm MTF curve of Example 3, at the field of view angle FOV = 7.14°, the target surface size IMH = 8.81mm, the MTF value is greater than 0.4 at 250lp / mm frequency, and the MTF value is greater than 0.7 at 125lp / mm frequency, indicating that this example has high resolution, good imaging quality, and high mid-frequency and high-frequency. Please refer to Fig. 20 , the near infrared 940nm MTF curve of Example 3, at the field of view angle FOV = 7.14°, the target surface size IMH = 8.81mm, the MTF value is greater than 0.38 at 250lp / mm frequency, and the MTF value is greater than 0.6 at 125lp / mm frequency, indicating that this example has high resolution, good imaging quality, and high mid-frequency and high-frequency. Please refer to Fig.21 , the distortion diagram of Example 3 under visible light 435-650nm, the edge field distortion values ​​are all less than ±1.5%, the optical distortion under the full field angle is small, the imaging effect is good, and the imaging restoration degree is high. Please refer to Fig. 22 , Example 3 shows the longitudinal chromatic aberration curve (magnification chromatic aberration diagram) under visible light 435-650nm, which shows the magnification chromatic aberration of the lens as the field of view changes. The five lines correspond to wavelengths 0.435um, 0.51um, 0.55um, 0.61um, and 0.65um. The horizontal axis represents the magnification chromatic aberration value, and the vertical axis represents the normalized field of view angle. The longitudinal chromatic aberration (magnification chromatic aberration) of the entire field of view is less than 2.5um. In such a large target surface and large optical system, the magnification chromatic aberration is negligible, so it can be called "zero chromatic aberration". Please refer to Fig.23 The spot diagram of Example 3 under visible light 435-650nm has a full field RMS of less than 5.5um. The spot diagram is larger than that of Example 1 and Example 2, indicating that the aberration of Example 3 is large under visible light. Fig.24 , the relative illumination diagram of Example 3 under visible light 435-650nm, it can be seen that the relative illumination of the lens is greater than 95% while ensuring the target half-image height of 4.405.

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

[0115] 1. The optical lens of the present invention has a light transmission of F1.6, excellent imaging, clear image quality, and excellent low-light processing ability and small depth of field brought by the large aperture, which can adapt to more shooting environments. The lens itself has a compact structure and is more portable than the lenses on the market.

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

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

[0118] 4. The lens of the present invention uses 6 pieces of ground spherical lenses. Relatively cheap optical materials are selected in the lens design stage to achieve the purpose of cost control, which greatly improves the production profit of the lens. At the same time, using fewer lenses can reduce the difficulty of optical assembly and simplify the manufacturing process.

[0119] 5. We put a lot of effort into the selection of lens materials and lens shapes to meet the high requirements and high standards of reliability testing for civilian rifle scopes, civilian sights, and even military rifle scopes, reduce the difficulty of optical assembly, and simplify the manufacturing process.

[0120] 6. The optical lens of the present invention can withstand vibrations of 10Hz~150Hz~10Hz 0.15mm IEC600068-2-6. After the test, the appearance and imaging are normal and dust-free.

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

[0122] Example 4

[0123] Reference Fig.25 , a description will be given of an electronic device A according to Example 4 of the present invention. Fig.25 is a schematic diagram of an electronic device using any of the low illumination imaging lenses according to Examples 1 to 3 for an imaging optical system.

[0124] exist Fig.25 , reference numeral A2 denotes an electronic device body, and reference numeral A1 denotes an imaging optical system (interchangeable lens) including any one of the low-illuminance imaging lenses according to Examples 1 to 3. Reference numeral A3 denotes 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 (optical image formed by the imaging optical system A1) from the imaging optical system A1 and performs photoelectric conversion.

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

[0126] Various examples may provide electronic devices having high optical performance.

[0127] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass 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, they are the first lens group, the second lens group, and the third lens group; The first lens group includes, from the object side to the image side, a positive refractive power lens and a group of first cemented lenses, wherein the first cemented lens is composed of a positive refractive power lens and a negative refractive power lens; The second lens group consists of two or less than two lenses, including at least one positive refractive power lens; The third lens group consists of a positive refractive power lens and a negative refractive power lens.

2. The low-light imaging lens according to claim 1, characterized in that: The first lens group includes a first lens, a second lens, and a third lens in order 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 power, and the object side surface is a concave surface.

3. The low-light imaging lens according to claim 2, characterized in that: The lens satisfies the following conditional formula: Nd2<1.5, Vd2>70, ΔPg, F>0.0035 Wherein, Nd2 is the refractive index of the second lens, Vd2 is the Abbe coefficient of the second lens, ΔPg, and F are relative partial dispersion.

4. The low-light imaging lens according to claim 3, characterized in that: The lens satisfies the following conditional formula: Nd3>1.8,Vd3<30 Wherein, Nd3 is the refractive index of the third lens, and Vd3 is the Abbe coefficient of the third lens.

5. The low-light imaging lens according to claim 1, characterized in that: The second lens group is composed of two lenses, which include a negative refractive power lens and a positive refractive power lens in order from the object side to the image side; the positive refractive power lens and the negative refractive power lens form a second cemented lens; The negative refractive power lens has a concave object side surface and a concave image side surface; The positive refractive power lens has a convex object side surface.

6. The low-light imaging lens according to claim 1, characterized in that: The second lens group is composed of less than two lenses, including a positive refractive power lens; the positive refractive power lens has a concave object side surface and a convex image side surface.

7. The low illumination imaging lens according to claim 6, characterized in that: The third lens group includes a positive refractive power lens and a negative refractive power lens in order from the object side to the image side; the object side surface of the positive refractive power lens is a convex surface; and the object side surface of the negative refractive power lens is a concave surface.

8. The low illumination imaging lens according to claim 7, characterized in that: The positive refractive power lens of the second lens group satisfies the following conditional formula: Nd4>1.9, Vd4<20, ΔPg, F>0.0035 Wherein, Nd4 is the refractive index of the positive refractive index lens, Vd4 is the Abbe coefficient of the positive refractive index lens, and ΔPg, F is the relative partial dispersion of the positive refractive index lens.

9. A low illumination imaging lens as claimed in claim 7 or 8, characterized in that: The positive refractive power lens and the negative refractive power lens of the third lens group satisfy the following conditional formula: Nd5<1.7, Vd5>55, Nd6>1.72, Vd6<30 Among them, Nd5 is the refractive index of the positive refractive index lens, Vd5 is the Abbe coefficient of the positive refractive index lens, Nd6 is the refractive index of the positive refractive index lens, and Vd6 is the Abbe coefficient of the positive refractive index lens.

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

Images