Day and night confocal security lens

Abstract

The invention relates to the technical field of security and protection lenses, in particular to a day and night confocal security and protection lens, which is sequentially arranged from an object side to an image side along an optical axis of the lens: an aspherical plastic lens with negative focal power; the aspherical plastic lens has positive focal power; the aspherical plastic lens has positive focal power; the spherical glass lens has positive focal power; the spherical glass lens has negative focal power; the spherical glass lens has positive focal power; an aspheric plastic lens with negative focal power; the aspherical plastic lens has positive focal power; according to the invention, the three spherical glass lenses and the five aspheric plastic lenses are adopted, and the focal power of each lens and the shape of each lens surface are reasonably configured, so that the optical system has good distortion correction, and meanwhile, the advantages of large aperture, day and night confocal, large target surface, high cost performance and the like are realized.

Description

Technical Field

[0001] This invention relates to the field of security lens technology, and in particular to a day and night confocal security lens. Background Technology

[0002] In the field of security monitoring, the lens is a key component, and its performance plays a decisive role in the effectiveness of security monitoring. Traditional security lenses have significant shortcomings when dealing with complex environments. At night or in low light conditions, the amount of light entering the lens is limited, resulting in dark images, high noise, and loss of detail. Furthermore, when switching between day and night lighting conditions, most lenses cannot achieve day-night confocal focusing; the focal length for clear imaging during the day shifts at night, leading to a decrease in image resolution. In addition, some existing lenses with day-night confocal focusing capabilities have small apertures, which cannot simultaneously meet the high-resolution imaging requirements under different day and night conditions. Therefore, developing a large-aperture day-night confocal security lens has significant practical implications. Summary of the Invention

[0003] Based on this, the purpose of the present invention is to provide a day and night confocal security lens. By reasonably configuring the optical power of each lens and the shape of each mirror surface, the optical system can be guaranteed to have good distortion correction, while also achieving advantages such as large aperture, day and night confocal focus, large target surface, and high cost performance.

[0004] The present invention adopts the following technical solution:

[0005] A day / night confocal security lens, arranged sequentially from the object side to the image side along the lens optical axis:

[0006] The first lens is an aspherical plastic lens with negative optical power;

[0007] The second lens is an aspherical plastic lens with positive optical power;

[0008] The third lens is an aspherical plastic lens with positive optical power;

[0009] The fourth lens is a spherical glass lens with positive optical power;

[0010] The fifth lens is a spherical glass lens with negative optical power;

[0011] The sixth lens is a spherical glass lens with positive optical power;

[0012] The seventh lens is an aspherical plastic lens with negative optical power;

[0013] The eighth lens is an aspherical plastic lens with positive optical power;

[0014] The lens satisfies the following relationship:

[0015] f≥7.5mm,

[0016] TTL≤30mm,

[0017] IC / TTL≥0.30,

[0018] TTL / f≤3.90,

[0019] OBFL / TTL≥0.17

[0020] In the formula, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focal length of the lens, IC is the full image height of the chip paired with the lens system, and the chip is a 1 / 1.8-inch target chip.

[0021] A further improvement to the above technical solution is that the focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens, respectively, range from -15.8 to -14.9, +45.8 to +90.7, +58.7 to +122.2, +8.3 to +8.7, -5.14 to -5.12, +6.2 to +6.5, -24.6 to -21.8, and +21.6 to +22.1; wherein, a "+" sign indicates that the focal length of the lens is positive, and a "-" sign indicates that the focal length of the lens is negative, and the unit of focal length is mm.

[0022] A further improvement to the above technical solution is that the refractive index ranges corresponding to the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens are respectively 1.50~1.55, 1.50~1.55, 1.63~1.67, 1.55~1.60, 1.60~1.65, 1.55~1.60, 1.63~1.67, and 1.50~1.55.

[0023] A further improvement to the above technical solution is that the ranges of the object-side surface curvature radii for the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens are +4.9 to +5.5, -5.1 to -4.3, +11.7 to +12.6, +8.7 to +9.3, -9.3 to -8.7, +4.9 to +5.1, -4.3 to -4.1, and +4.7 to +5.0, respectively; where "+" indicates that the surface bends toward the image plane, and "-" indicates that the surface bends toward the object plane, and the unit of the object-side surface curvature radius is mm.

[0024] A further improvement to the above technical solution is that the ranges of the image-side surface curvature radii for the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens are +2.8 to +3.0, -4.9 to -4.7, +12.7 to +17.6, -9.3 to -8.7, +4.9 to +5.1, -11.2 to -9.5, -6.7 to -6.0, and +6.9 to +7.4, respectively; where "+" indicates that the surface bends toward the image plane, and "-" indicates that the surface bends toward the object plane, and the unit of the image-side surface curvature radius is mm.

[0025] A further improvement to the above technical solution is that the lens also satisfies the following relationship:

[0026] -2.1≤f1 / f≤-1.9

[0027] 6.1≤f² / f≤12.1,

[0028] 7.8≤f³ / f≤16.3

[0029] 1.1≤f4 / f≤1.2,

[0030] -0.7≤f5 / f≤-0.6,

[0031] 0.8≤f6 / f≤0.9

[0032] -3.3≤f7 / f≤-2.9,

[0033] 2.8 ≤ f8 / f ≤ 3.0

[0034] In the formula, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens.

[0035] A further improvement to the above technical solution is that the aperture of the lens is F#, satisfying F#≥1.0.

[0036] A further improvement to the above technical solution is that the object-side surface of the first lens is convex, and its image-side surface may be concave; the object-side surface of the second lens is concave, and its image-side surface is convex; the object-side surface of the third lens is convex, and its image-side surface is concave; the object-side surface of the fourth lens is convex, and its image-side surface is convex; the object-side surface of the fifth lens is concave, and its image-side surface is concave; the object-side surface of the sixth lens is convex, and its image-side surface is convex; the object-side surface of the seventh lens is concave, and its image-side surface is convex; and the object-side surface of the eighth lens is convex, and its image-side surface is concave.

[0037] A further improvement to the above technical solution is that the fourth lens, the fifth lens, and the sixth lens form a three-layer cemented lens.

[0038] A further improvement to the above technical solution is that an aperture stop, a protective glass, and an image acquisition element are also provided along the optical axis of the lens from the object side to the image side; the aperture stop is located between the second lens and the third lens; the protective glass is integrated on the image acquisition element, and the protective glass is H-K9L glass; the image acquisition element is located on the image side of the protective glass.

[0039] The beneficial effects of this invention are as follows:

[0040] This invention employs eight lenses with specific optical power, and through specific surface shape combinations and reasonable optical power distribution, makes the lens structure more compact. Compared with existing lenses on the market, it has a focal length f≥7.5mm and an aperture F#≥1.0, ensuring a large amount of light intake; it has the advantages of a total length ≤30mm, meeting day and night co-focus requirements, and easy integration; it can be matched with a 1 / 1.8-inch target surface chip, and can be matched with chips with higher pixel counts; thus meeting the requirements of a large aperture, day and night co-focus lens.

[0041] In terms of manufacturing feasibility, this invention uses three spherical glass lenses and four aspherical plastic lenses, which are stable in terms of temperature drift. The thickness of each lens is uniform and reasonable and not sensitive, making it easy to manufacture and with a high yield. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the optical structure of Embodiment 1 of the day and night confocal security lens of the present invention;

[0043] Figure 2 for Figure 1 A schematic diagram of the Spot Diagram for Example 1;

[0044] Figure 3 for Figure 1 The Modulus of the OTF curve at 125 lp / mm in visible light in Example 1;

[0045] Figure 4 for Figure 1 The Modulus of the OTF curve at 125 lp / mm under infrared light in Example 1;

[0046] Figure 5 This is a schematic diagram of the optical structure of Embodiment 2 of the day and night confocal security lens of the present invention;

[0047] Figure 6 for Figure 5A schematic diagram of the Spot Diagram for Example 2;

[0048] Figure 7 for Figure 5 The Modulus of the OTF curve at 125 lp / mm in visible light in Example 2;

[0049] Figure 8 for Figure 5 The Modulus of the OTF curve under infrared light at 125 lp / mm in Example 2.

[0050] The numbers on the map are:

[0051] 1-First lens, 2-Second lens, 3-Third lens, 4-Fourth lens, 5-Fifth lens, 6-Sixth lens, 7-Seventh lens, 8-Eighth lens, 9-Protective glass, 10-Image acquisition element, 11-Aperture. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. In this specification, the expressions "first," "second," "third," etc., are only used to distinguish one feature from another, and do not indicate any limitation on the features. The shape of a spherical or aspherical surface is not limited to the spherical or aspherical shapes shown in the drawings. The drawings are for illustrative purposes only and are not strictly drawn to scale.

[0053] In this invention, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region; if the lens surface is not defined as convex, concave, or flat, it means that the lens surface can be convex, concave, or flat. The surface of each lens closest to the object being photographed is called the object-side surface of the lens, and the surface of each lens closest to the imaging plane is called the image-side surface of the lens.

[0054] Unless otherwise specified, all terms used in this invention (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the same meaning as they have in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense unless expressly so defined in this invention.

[0055] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. For better understanding and implementation, the invention will be described in detail below with reference to the accompanying drawings.

[0056] This invention provides a large-aperture, day-night confocal lens. The surface of the lens adjacent to the object plane is the object-side surface, and the surface of the lens adjacent to the image plane is the image-side surface. Along the lens optical axis from the object side to the image side, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a protective glass 9, an image acquisition element 10, and an aperture stop 11 are arranged sequentially. The aperture stop is located between the second lens 2 and the third lens 3. The protective glass 9 is disposed on the image-side surface of the eighth lens 8 and is made of H-K9L glass. The image acquisition element 10 is disposed on the image-side surface of the protective glass 9, and the protective glass 9 is integrated onto the image acquisition element 10.

[0057] In this invention, to achieve better performance of the optical system, we need to rationally select lens materials, rationally allocate the focal length of each lens, and rationally optimize the optical system during the design process. Ultimately, we aim to optimize the performance of the optical system. The presence of aberrations in the optical system usually affects the imaging quality. Correcting aberrations is the key to optimizing the optical system. There are many methods for correcting aberrations. For example, using lenses with different refractive indices and significantly different Abbe numbers can eliminate chromatic aberration and spherical aberration to a certain extent. Rationally allocating and optimizing the focal length and shape of each lens can also correct the aberrations of the system.

[0058] In this invention, the focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, the focal length of the fifth lens 5 is f5, the focal length of the sixth lens 6 is f6, the focal length of the seventh lens 7 is f7, the focal length of the eighth lens 8 is f8, and the total focal length of the entire lens is f. The ratio of the focal length of each lens to the total focal length of the lens satisfies the following condition:

[0059] -2.1≤f1 / f≤-1.9

[0060] 6.1≤f² / f≤12.1,

[0061] 7.8≤f³ / f≤16.3

[0062] 1.1≤f4 / f≤1.2,

[0063] -0.7≤f5 / f≤-0.6,

[0064] 0.8≤f6 / f≤0.9

[0065] -3.3≤f7 / f≤-2.9,

[0066] 2.8 ≤ f8 / f ≤ 3.0

[0067] In this invention, the focal length, refractive index, and radius of curvature of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens respectively satisfy the following conditions:

[0068]

[0069]

[0070] Wherein, f1 is the focal length of the first lens, ND1 is the refractive index of the first lens, R11 is the object-side radius of curvature of the first lens, and R12 is the image-side radius of curvature of the first lens; f2 is the focal length of the second lens, ND2 is the refractive index of the second lens, R21 is the object-side radius of curvature of the second lens, and R22 is the image-side radius of curvature of the second lens; f3 is the focal length of the third lens, ND3 is the refractive index of the third lens, R31 is the object-side radius of curvature of the third lens, and R32 is the image-side radius of curvature of the third lens; f4 is the focal length of the fourth lens, ND4 is the refractive index of the fourth lens, R41 is the object-side radius of curvature of the fourth lens, and R42 is the image-side radius of curvature of the fourth lens; f5 is the focal length of the fifth lens, ND5 is the refractive index of the fifth lens, R11 is the object-side radius of curvature of the fifth lens, and R12 is the image-side radius of curvature of the fifth ... The refractive index of the lens is given by R51, the object-side radius of curvature of the fifth lens is given by R52, and the image-side radius of curvature of the fifth lens is given by R52. The focal length of the sixth lens is given by f6, ND6 is given by ND6, R61 is given by ND61, and R62 is given by R62. The focal length of the seventh lens is given by f7, ND7 is given by ND7, R71 is given by ND71, and R72 is given by R72. The focal length of the eighth lens is given by f8, ND8 is given by ND8, R81 is given by ND81, and R82 is given by R82. A "+" sign for the radius of curvature indicates that the surface bends towards the image plane, while a "-" sign indicates that the surface bends towards the object plane.

[0071] In this invention, f is the total focal length of the lens; TTL is the total optical length of the lens; OBFL is the optical back focal length of the lens, which is defined as the distance from the point on the image side of the eighth lens closest to the image plane to the image plane; IC is the full image height of the 1 / 1.8-inch chip used with the lens system; they satisfy the following conditions:

[0072] f≥7.5mm,

[0073] TTL≤30mm,

[0074] IC / TTL≥0.30,

[0075] TTL / f≤3.90,

[0076] OBFL / TTL≥0.17

[0077] In this invention, the aperture of the lens is F#, which satisfies F#≥1.0 to ensure a large amount of light intake; the lens angle is FOV, which satisfies FOV≤66°.

[0078] Example 1

[0079] refer to Figure 1 , Figure 2 As shown, these are schematic diagrams of the optical structure and optical path structure of Embodiment 1, respectively.

[0080] In this embodiment, the field of view (FOV) is 66°, the focal length (f) is ≤7.7mm, and the principal ray angle (CRA) of the lens is defined as CRA = 14.19°. By rationally selecting lens materials and rationally allocating the focal length and optical power of each lens, the optical system is optimized to achieve uniform and insensitive thickness of each lens, making it easy to mass-produce.

[0081] In this embodiment, the lenses are arranged sequentially from the object side to the image side along the lens optical axis:

[0082] The first lens is an aspherical plastic lens with negative optical power. The object side of the first lens is convex, and its image side can be concave.

[0083] The second lens is an aspherical plastic lens with positive optical power. The object side of the second lens is concave, and its image side is convex.

[0084] An aperture stop is disposed on the image side of the second lens;

[0085] The third lens is an aspherical plastic lens with positive optical power. The object side of the third lens is convex, and its image side is concave.

[0086] The fourth lens is a spherical glass lens with positive optical power, wherein the object side of the fourth lens is convex and the image side is convex.

[0087] The fifth lens is a spherical glass lens with negative optical power, wherein the object side of the fifth lens is concave and the image side is concave.

[0088] The sixth lens is a spherical glass lens with positive optical power, and the object side and the image side of the sixth lens are both convex.

[0089] The seventh lens is an aspherical plastic lens with negative optical power, wherein the object side of the seventh lens is concave and the image side is convex.

[0090] The eighth lens is an aspherical plastic lens with positive optical power, wherein the object side of the eighth lens is convex and the image side is concave.

[0091] A filter, the filter being disposed on the object side of the eighth lens;

[0092] A protective glass and an image acquisition element, wherein the protective glass is integrated on the image acquisition element, and the image acquisition element is disposed on the image side of the filter.

[0093] In this embodiment, the first lens 1 is an aspherical plastic lens with negative optical power, its object side is convex and its image side is concave, forming a meniscus lens with negative optical power, which facilitates rapid light convergence; the second lens 2 is an aspherical plastic lens with positive optical power, used to guide light amplification, increase the aperture, and ensure sufficient light intake; the third lens 3 is a high-refractive-index plastic aspherical lens with a refractive index greater than 1.60 and an Abbe number less than 24, its main function is to correct the resolution, making it compatible with higher pixel chips; the fourth lens 4, the fifth lens 5, and the sixth lens 6 form a cemented triplet lens, its main function is to correct chromatic aberration and balance temperature drift; the seventh lens 7 has a concave object side and a convex image side, its main function is to guide light amplification, making it easier to achieve a larger target surface; the eighth lens 8 has a convex object side and a convex image side, used to control CRA and improve resolution.

[0094] Table 1 provides the radius of curvature R (in mm), center thickness d (in mm), refractive index (ND), Abbe constant (VD), and aspherical K value (Conic) for each lens.

[0095] Table 1

[0096]

[0097]

[0098] In Table 1, the radius of curvature R represents the curvature of the lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "INFINITY" indicates that the surface is flat. The center thickness D represents the central axial distance from the current surface to the next surface. The refractive index ND represents the ability of the current lens material to deflect light. The Abbe number VD represents the dispersion characteristics of the current lens material. The k value represents the value of the best-fit conic coefficient of the aspherical surface. 11 represents the object-side surface of the first lens 1, 12 represents the image-side surface of the first lens 1, and so on. 91 is the object-side surface of the protective lens 9, and 92 is the image-side surface of the protective lens 9.

[0099] In this embodiment, the aspherical surfaces of the first lens 1, the second lens 2, the third lens 3, the seventh lens 7, and the eighth lens 8 can all be defined by the following equation for even-order aspherical surfaces:

[0100]

[0101] In the formula, Z is the sag of the lens along the optical axis, k is the surface conic coefficient, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, and G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial.

[0102] Table 2 gives the coefficients of the aspherical surfaces of each optical surface of the first lens 1, the second lens 2, the third lens 3, the seventh lens 7, and the eighth lens 8.

[0103] Table 2

[0104] Face number A B C D E F G 11 -1.89E-03 8.75E-02 3.91E-06 -1.55E-07 2.45E-09 -2.38E-12 -2.31E-13 12 -4.48E-03 2.78E-05 -1.95E-06 7.60E-07 -7.02E-08 2.67E-09 -3.94E-11 21 -6.15E-04 7.36E-05 -2.93E-06 1.53E-07 -8.18E-09 2.86E-10 -5.24E-12 22 2.19E-03 -1.33E-04 8.86E-06 -4.09E-07 1.03E-08 -1.18E-10 -1.74E-13 31 2.22E-04 3.01E-05 -2.65E-07 -1.61E-08 7.97E-10 -1.37E-11 9.50E-14 32 -2.38E-04 5.40E-05 -1.50E-06 6.03E-08 -1.58E-09 3.02E-11 -2.31E-13 71 -5.34E-04 9.67E-05 -4.99E-06 -1.36E-07 2.23E-08 -8.70E-10 1.18E-11 72 3.97E-04 5.44E-05 -6.26E-06 1.39E-07 3.89E-09 -2.94E-10 5.13E-12 81 1.91E-04 -3.46E-04 3.03E-05 -1.97E-06 6.32E-08 -8.11E-10 3.57E-12 82 -3.91E-03 2.17E-04 -2.03E-05 1.27E-06 -5.18E-08 1.30E-09 -1.46E-11

[0105] refer to Figure 2 The image shows the visible light spot diagram of the lens in this embodiment, where OBJ and IMA represent different fields of view; from Figure 2 As can be seen from the data, the Airy disk radius is 0.7065 μm, and the light spots are concentrated in the meridional and sagittal directions on the image plane, indicating that the lens has good aberration correction.

[0106] refer to Figure 3 As shown, this is the Modulus of the OTF curve for the lens in this embodiment at a frequency of 125 lp / mm in the visible light range of 0.435-0.656 μm. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. Figure 3 As can be seen from the data, except for the maximum field of view, the visible light resolution of this lens in the 0.435-0.656μm range is greater than 0.4 at 125mm / lp, indicating that the lens can guarantee high resolution.

[0107] refer to Figure 4As shown, this is the Modulus of the OTF curve for the lens in this embodiment at an infrared light frequency of 125 lp / mm in the 0.83-0.85 μm range. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. Figure 4 As can be seen from the data, except for the maximum field of view, the visible light resolution of the lens in the 0.83-0.85μm range is greater than 0.6 at 125mm / lp, indicating that the lens can maintain high resolution in night vision environments.

[0108] Depend on Figure 3 , 4 As can be seen, the MTF of the lens can be well corrected in this embodiment.

[0109] In this embodiment 1, the total focal length of the lens system is f = 7.7mm, the aperture value is F# = 1.06, the total length of the lens (TTL) is 30mm, the optical back focal length (OBFL) is 5.06mm, and the field of view (DFOV) of the lens matched with the 1 / 1.8-inch sensor is 66°.

[0110] Example 2

[0111] refer to Figure 5 , Figure 6 As shown, these are schematic diagrams of the optical structure and optical path structure of Embodiment 2, respectively.

[0112] In this embodiment, the field of view (FOV) is 66°, the focal length (f) is ≤7.7mm, and the principal ray angle (CRA) of the lens is defined as CRA = 15°. By rationally selecting lens materials and rationally allocating the focal length and optical power of each lens, the optical system is optimized to achieve uniform and insensitive thickness of each lens, making it easy to mass-produce.

[0113] In this embodiment, the lenses are arranged sequentially from the object side to the image side along the lens optical axis:

[0114] The first lens is an aspherical plastic lens with negative optical power. The object side of the first lens is convex, and its image side can be concave.

[0115] The second lens is an aspherical plastic lens with positive optical power. The object side of the second lens is concave, and its image side is convex.

[0116] An aperture stop is disposed on the image side of the second lens;

[0117] The third lens is an aspherical plastic lens with positive optical power. The object side of the third lens is convex, and its image side is concave.

[0118] The fourth lens is a spherical glass lens with positive optical power, wherein the object side of the fourth lens is convex and the image side is convex.

[0119] The fifth lens is a spherical glass lens with negative optical power, wherein the object side of the fifth lens is concave and the image side is concave.

[0120] The sixth lens is a spherical glass lens with positive optical power, and the object side and the image side of the sixth lens are both convex.

[0121] The seventh lens is an aspherical plastic lens with negative optical power, wherein the object side of the seventh lens is concave and the image side is convex.

[0122] The eighth lens is an aspherical plastic lens with positive optical power, wherein the object side of the eighth lens is convex and the image side is concave.

[0123] A filter, the filter being disposed on the object side of the eighth lens;

[0124] A protective glass and an image acquisition element, wherein the protective glass is integrated on the image acquisition element, and the image acquisition element is disposed on the image side of the filter.

[0125] In this embodiment, the first lens 1 is an aspherical plastic lens with negative optical power, its object side is convex and its image side is concave, forming a meniscus lens with negative optical power, which facilitates rapid light convergence; the second lens 2 is an aspherical plastic lens with positive optical power, used to guide light amplification, increase the aperture, and ensure the amount of light entering; the third lens 3 is a high-refractive-index plastic aspherical lens with a refractive index greater than 1.60 and an Abbe number less than 24, its main function is to correct the resolution, making it compatible with higher pixel chips; the fourth lens 4, the fifth lens 5, and the sixth lens 6 form a cemented triplet lens, its main function is to correct chromatic aberration and balance temperature drift; the seventh lens 7 has a concave object side and a convex image side, its main function is to guide light amplification, making it easier to achieve a larger target surface; the eighth lens 8 has a convex object side and a convex image side, used to control CRA and improve resolution.

[0126] Table 3 provides the radius of curvature R (in mm), center thickness d (in mm), refractive index (ND), Abbe constant (VD), and aspherical K value (Conic) for each lens.

[0127] Table 3

[0128]

[0129]

[0130] In Table 3, the radius of curvature R represents the curvature of the lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "INFINITY" indicates that the surface is planar. The center thickness D represents the central axial distance from the current surface to the next surface. The refractive index ND represents the ability of the current lens material to deflect light. The Abbe number VD represents the dispersion characteristics of the current lens material. The k value represents the value of the best-fit conic coefficient of the aspherical surface. 11 represents the object-side surface of the first lens 1, 12 represents the image-side surface of the first lens 1, and so on. 91 is the object-side surface of the protective lens 9, and 92 is the image-side surface of the protective lens 9.

[0131] In this embodiment, the aspherical surfaces of the first lens 1, the second lens 2, the third lens 3, the seventh lens 7, and the eighth lens 8 can all be defined by the following equation for even-order aspherical surfaces:

[0132]

[0133] In the formula, Z is the sag of the lens along the optical axis, k is the surface conic coefficient, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, and G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial.

[0134] Table 4 gives the coefficients of the aspherical surfaces of each optical surface of the first lens 1, the second lens 2, the third lens 3, the seventh lens 7, and the eighth lens 8.

[0135] Table 4

[0136]

[0137]

[0138] refer to Figure 6 The image shows the visible light spot diagram of the lens in this embodiment, where OBJ and IMA represent different fields of view; from Figure 2 As can be seen from the data, the Airy disk radius is 0.7065 μm, and the light spots are concentrated in the meridional and sagittal directions on the image plane, indicating that the lens has good aberration correction.

[0139] refer to Figure 7 As shown, this is the Modulus of the OTF curve for the lens in this embodiment at a frequency of 125 lp / mm in the visible light range of 0.435-0.656 μm. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. Figure 7As can be seen from the data, except for the maximum field of view, the visible light range of 0.435-0.656μm of this lens has a resolution greater than 0.5 at 125mm / lp, indicating that the lens can guarantee high resolution.

[0140] refer to Figure 8 As shown, this is the Modulus of the OTF curve for the lens in this embodiment at an infrared light frequency of 125 lp / mm in the 0.83-0.85 μm range. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. Figure 8 As can be seen from the data, except for the maximum field of view, the infrared light resolution of the lens in the 0.83-0.85μm range is greater than 0.6 at 125mm / lp, indicating that the lens can maintain high resolution in night vision environments.

[0141] Depend on Figure 7 , 8 As can be seen, the MTF of the lens can be well corrected in this embodiment.

[0142] In this embodiment 2, the total focal length of the lens system is f = 7.55mm, the aperture value is F# = 1.06, the total length of the lens (TTL) is 30mm, the optical back focal length (OBFL) is 5.262mm, and the field of view (DFOV) of the lens matched with the 1 / 1.8-inch sensor is 66°.

[0143] As can be seen from the F-Tan(θ) distortion curves, field curvature curves, and MTF curves of the above embodiments, the optical lens provided by the present invention has the advantages of small size, high imaging quality and high pixel count with a large target surface, large depth of focus to accommodate a larger depth of field range, and good manufacturability and yield.

[0144] The above description merely illustrates preferred technical solutions of the present invention, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. A day / night confocal security lens, characterized in that, Set sequentially from the object side to the image side along the lens optical axis: The first lens is an aspherical plastic lens with negative optical power; The second lens is an aspherical plastic lens with positive optical power; The third lens is an aspherical plastic lens with positive optical power; The fourth lens is a spherical glass lens with positive optical power; The fifth lens is a spherical glass lens with negative optical power; The sixth lens is a spherical glass lens with positive optical power; The seventh lens is an aspherical plastic lens with negative optical power; The eighth lens is an aspherical plastic lens with positive optical power; The lens satisfies the following relationship: f≥7.5mm, TTL≤30mm, IC / TTL≥0.30, TTL / f≤3.90, OBFL / TTL≥0.17 In the formula, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focal length of the lens, IC is the full image height of the chip paired with the lens system, and the chip is a 1 / 1.8-inch target chip.

2. The day / night confocal security lens according to claim 1, characterized in that, The focal lengths of the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens, respectively, range from -15.8 to -14.9, +45.8 to +90.7, +58.7 to +122.2, +8.3 to +8.7, -5.14 to -5.12, +6.2 to +6.5, -24.6 to -21.8, and +21.6 to +22.

1. A "+" sign indicates a positive focal length, and a "-" sign indicates a negative focal length. The unit of focal length is mm.

3. The day / night confocal security lens according to claim 1, characterized in that, The refractive index ranges corresponding to the first lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens, and eighth lens are respectively; 1.50～1.55、1.50～1.55、1.63～1.67、1.55～1.60、1.60～1.65、1.55～1.60、1.63～1.67、1.50～1.55。 4. The day / night confocal security lens according to claim 1, characterized in that, The object-side surface curvature radii for the first, second, third, fourth, fifth, sixth, seventh, and eighth lenses are respectively +4.9 to +5.5, -5.1 to -4.3, +11.7 to +12.6, +8.7 to +9.3, -9.3 to -8.7, +4.9 to +5.1, -4.3 to -4.1, and +4.7 to +5.

0. A "+" sign indicates that the surface bends towards the image plane, and a "-" sign indicates that the surface bends towards the object plane. The unit for the object-side surface curvature radius is mm.

5. The day / night confocal security lens according to claim 1, characterized in that, The image-side surface curvature radii of the first, second, third, fourth, fifth, sixth, seventh, and eighth lenses, respectively, range from +2.8 to +3.0, -4.9 to -4.7, +12.7 to +17.6, -9.3 to -8.7, +4.9 to +5.1, -11.2 to -9.5, -6.7 to -6.0, and +6.9 to +7.

4. A "+" sign indicates that the surface bends towards the image plane, and a "-" sign indicates that the surface bends towards the object plane. The unit for the image-side surface curvature radius is mm.

6. The day / night confocal security lens according to claim 1, characterized in that, The lens also satisfies the following relationship: -2.1≤f1 / f≤-1.9 6.1≤f² / f≤12.1 7.8≤f³ / f≤16.3 1.1≤f4 / f≤1.2, -0.7≤f5 / f≤-0.6, 0.8≤f6 / f≤0.9 -3.3≤f7 / f≤-2.9, 2.8 ≤ f8 / f ≤ 3.0 In the formula, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens.

7. The day / night confocal security lens according to claim 1, characterized in that, The aperture of the lens is F#, which satisfies F#≥1.

0.

8. The day and night confocal security lens according to claim 1, characterized in that, The object-side surface of the first lens is convex, and its image-side surface may be concave; the object-side surface of the second lens is concave, and its image-side surface is convex; the object-side surface of the third lens is convex, and its image-side surface is concave; the object-side surface of the fourth lens is convex, and its image-side surface is convex; the object-side surface of the fifth lens is concave, and its image-side surface is concave; the object-side surface of the sixth lens is convex, and its image-side surface is convex; the object-side surface of the seventh lens is concave, and its image-side surface is convex; the object-side surface of the eighth lens is convex, and its image-side surface is concave.

9. The day / night confocal security lens according to claim 1, characterized in that, The fourth, fifth, and sixth lenses together form a three-layer composite lens.

10. The day and night confocal security lens according to claim 1, characterized in that, Along the optical axis of the lens from the object side to the image side, there are also an aperture stop, a protective glass and an image acquisition element; the aperture stop is located between the second lens and the third lens; the protective glass is integrated on the image acquisition element, and the protective glass is H-K9L glass; the image acquisition element is located on the image side of the protective glass.

Images