Day and night confocal optical lens
By designing a six-lens day and night confocal optical lens, combining glass spherical and plastic aspherical lenses, the problem of poor imaging quality in the night is solved in the existing technology, and high-definition imaging and low distortion under different lights are achieved, which meets the Balanced monitoring needs day and night.
Patent Information
- Application Number
- CN202421056820.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-15
- Publication Date
- 2025-01-17
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing optical lenses are difficult to achieve high-definition and low-distortion imaging in poor night light environments, and cannot meet the surveillance needs of day and night.
Design a day and night confocal optical lens composed of six lenses, one of which is a glass spherical lens and five are plastic aspherical lenses. By rationally designing the power and surface shape, combining glass spherical lenses and plastic aspherical lenses. Achieve high-definition imaging and small distortion of the lens under different lights.
When switching between day and night, the lens has good imaging quality and low distortion, reducing the difficulty of correcting the distortion in the later stage, while meeting the needs of high definition.
Smart Images
Figure CN222365139U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of optical lenses, in particular to a day-and-night confocal optical lens. Background Art
[0002] In a fast-paced society, people go out early and come back late, and are away from home for a long time, so they cannot know the situation of people or pets at home in time. With the development of society, people can monitor pets or other daily situations at home through smart home cameras to obtain real-time information at home in time. However, in poor light conditions such as at night, the lens is difficult to image clearly and cannot meet the use needs. Therefore, there is an urgent need for an imaging optical lens that can image high-definition and low-distortion in different light conditions to meet people's daily needs. Utility Model Content
[0003] In view of the above-mentioned shortcomings and deficiencies of the prior art, the utility model provides a day-night confocal optical lens, which is mainly composed of six lenses, one of which is a glass spherical lens, five are plastic aspherical lenses, and the glass spherical lens is the third or fourth lens. Through the reasonable design of the optical power and surface shape of the first lens to the sixth lens, the lens achieves day-night confocality while having the advantages of high definition and small distortion, and has high imaging quality.
[0004] In order to achieve the above-mentioned purpose, the main technical solutions adopted by the utility model include:
[0005] A day-night confocal optical lens, which is composed of the following components in order from the object side to the image side along the optical axis:
[0006] A first lens having negative optical power, wherein the object side surface of the first lens at a near optical axis is concave, and the image side surface of the first lens is concave;
[0007] a second lens having positive refractive power, wherein the object-side surface of the second lens at the near optical axis is convex, and the image-side surface of the second lens is convex;
[0008] a third lens element having positive refractive power, wherein the image-side surface of the third lens element at the near optical axis is convex;
[0009] a fourth lens element having negative or positive refractive power, wherein the object-side surface of the fourth lens element at a near optical axis is convex;
[0010] a fifth lens element having positive refractive power, wherein the object side surface of the fifth lens element at a near optical axis is convex;
[0011] The sixth lens element has positive refractive power, and the object-side surface of the sixth lens element near the optical axis is convex.
[0012] The first lens, the second lens, the fifth lens and the sixth lens are all plastic aspheric lenses, and the third lens and the fourth lens are glass spherical lenses or plastic aspheric lenses;
[0013] The lens satisfies the following conditional formula:
[0014] 5.2 <TTL / Fno<8.8
[0015] 7.68 <TTL / F<8.6
[0016] Wherein, TTL is the distance from the object side of the first lens to the image plane, Fno is the aperture value of the lens, and F is the effective focal length of the lens.
[0017] By limiting the ratio of the distance from the object side of the first lens to the image plane to the aperture value, a suitable size and a corresponding aperture range of the diaphragm can be selected to ensure the brightness range of the lens while meeting the structural size.
[0018] By limiting the ratio of the distance from the object side of the first lens to the image plane to the effective focal length, the corresponding optical lens can be selected according to the structural size and the focusing image plane position required by the finished device.
[0019] Through the design of combining glass spherical lens and plastic aspherical lens, the glass lens can be selectively placed in the third or fourth lens position to improve the performance of the overall optical lens. At the same time, each lens is designed accordingly to make the lens meet DFOV≥99°, TTL≤17. The lens has the advantages of high definition and small distortion, which reduces the difficulty of later correction of distortion; and the lens has the function of day and night parfocality, so that the lens has good imaging quality when switching between day and night.
[0020] Furthermore, the lens satisfies the following conditional formula:
[0021] 19.82 <DFOV / ImgH<28.7
[0022] Wherein, DFOV is the diagonal imaging angle of the lens, and ImgH is the diagonal imaging diameter of the lens.
[0023] By satisfying the above conditional formula and selecting the appropriate target surface size for different field of view angles, the difficulty of later matching of the lens chip and structure can be effectively reduced.
[0024] Furthermore, the lens satisfies the following conditional formula:
[0025] 1.8≤ET1 / CT1≤2.4
[0026] Wherein, ET1 is the edge thickness of the first lens, and CT1 is the center thickness of the first lens.
[0027] By satisfying the above conditional expression and adjusting the center thickness and edge thickness of the first lens, lenses with different field angles can be obtained, which can cope with use in different environments.
[0028] Furthermore, the lens satisfies the following conditional formula:
[0029] 1.69≤|F1 / F|≤1.87
[0030] Wherein, F1 is the focal length of the first lens.
[0031] By satisfying the above conditional expression, the absolute value of the ratio of the focal length of the lens to the focal length of the first lens is limited, thereby reducing the difficulty of processing the first lens.
[0032] Furthermore, the lens satisfies the following conditional formula:
[0033] 3.5≤FG≤5.7
[0034] Among them, FG is the focal length of the glass spherical lens in the lens.
[0035] By satisfying the above conditional formula, changing the focal length of the glass spherical lens in the lens can adjust the performance of the lens working in the infrared state;
[0036] Furthermore, the lens satisfies the following conditional formula:
[0037] 0.65≤CTG / F≤0.83
[0038] Among them, CTG is the center thickness of the glass spherical lens in the lens.
[0039] By satisfying the above conditional formula and adjusting the center thickness of the glass spherical lens in the lens and the focal length of the lens, the difficulty of the glass spherical lens in the processing process can be reduced.
[0040] Furthermore, the lens satisfies the following conditional formula:
[0041] 2.23≤CT1+CTG≤2.95
[0042] Among them, CT1 is the center thickness of the first lens, and CTG is the center thickness of the glass spherical lens in the lens.
[0043] By satisfying the above conditional formula, the sum of the center thickness of the first lens and the center thickness of the glass spherical lens in the lens can be adjusted, and the performance in the infrared state can be adjusted;
[0044] Furthermore, the lens satisfies the following conditional formula:
[0045] 3.34≤ET1+ETG≤4.04
[0046] Among them, ETG is the edge thickness of the glass spherical lens in the lens.
[0047] By satisfying the above conditional formula, the sum of the edge thickness of the first lens and the edge thickness of the glass spherical lens in the lens is adjusted, so that the edge light of the lens can be combed to ensure that the size of the field of view is suitable and meets the requirements of the lens use environment.
[0048] The beneficial effects of the utility model are:
[0049] The utility model provides a day-night confocal optical lens, which is mainly composed of six lenses, one of which is a glass spherical lens, and five are plastic aspherical lenses. Through the design of combining the glass spherical lens and the plastic aspherical lens, the glass lens can be selectively placed at the position of the third or fourth lens to improve the performance of the overall optical lens. At the same time, each lens is designed accordingly, so that the overall lens has high definition and small distortion, reducing the difficulty of later correction of distortion; and the lens has the function of day-night confocal, so that the lens has good imaging quality when switching between day and night. BRIEF DESCRIPTION OF THE DRAWINGS
[0050] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present utility model;
[0051] Figure 2 This is a defocus curve diagram (60lp / mm) of Example 1 of the utility model under visible light 435-650nm;
[0052] Figure 3 This is the defocus curve diagram (60lp / mm) of Example 1 of the utility model under infrared light 850nm;
[0053] Figure 4 This is a spot diagram of Example 1 of the utility model under visible light 435-650nm;
[0054] Figure 5 This is a field curvature curve diagram of Example 1 of the utility model;
[0055] Figure 6 This is a distortion curve diagram of Example 1 of the utility model;
[0056] Figure 7 This is a schematic diagram of the structure of Embodiment 2 of the present utility model;
[0057] Figure 8 This is a defocus curve diagram (60lp / mm) of Example 2 of the utility model under visible light 435-650nm;
[0058] Fig. 9This is a defocus curve diagram (60lp / mm) of Example 2 of the utility model under infrared light 850nm;
[0059] Fig.10 This is a spot diagram of Example 2 of the utility model under visible light 435-650nm;
[0060] Fig.11 This is a field curvature curve diagram of Example 2 of the present utility model;
[0061] Fig.12 This is a distortion curve diagram of Example 2 of the utility model;
[0062] Fig.13 This is a schematic diagram of the structure of Embodiment 3 of the present utility model;
[0063] Fig.14 This is a defocus curve diagram (60lp / mm) of Example 3 of the utility model under visible light 435-650nm;
[0064] Fig.15 This is a defocus curve diagram (60lp / mm) of Example 3 of the utility model under infrared light 850nm;
[0065] Fig.16 This is a spot diagram of Example 3 of the present utility model under visible light 435-650nm;
[0066] Fig.17 This is a field curvature curve diagram of Example 3 of the present utility model;
[0067] Fig.18 This is a distortion curve diagram of Example 3 of the present utility model.
[0068] In the figure: 1, first lens; 2, second lens; 3, third lens; 4, fourth lens; 5, fifth lens; 6, sixth lens; 7, aperture; 8, filter. DETAILED DESCRIPTION
[0069] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.
[0070] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn strictly to scale.
[0071] In this document, the surface of each lens closest to the object is called the object-side surface, and the surface of each lens closest to the imaging plane is called the image-side surface.
[0072] The present invention provides a day-night confocal optical lens, which is composed of the following components in sequence from the object side to the image side along the optical axis:
[0073] A first lens 1 having negative optical power, wherein the object side surface of the first lens 1 at the near optical axis is concave, and the image side surface is concave;
[0074] a second lens 2 having positive refractive power, wherein the object-side surface of the second lens 2 at the near optical axis is convex, and the image-side surface of the second lens 2 is convex;
[0075] a third lens element 3 having positive refractive power, wherein the image side surface of the third lens element 3 at the near optical axis is a convex surface;
[0076] a fourth lens element 4 having negative or positive refractive power, wherein the object side surface of the fourth lens element 4 at the near optical axis is convex;
[0077] a fifth lens element 5 having positive refractive power, wherein the object side surface of the fifth lens element 5 at a near optical axis is a convex surface;
[0078] The sixth lens element 6 has positive refractive power, and the object-side surface of the sixth lens element 6 near the optical axis is convex.
[0079] The first lens 1, the second lens 2, the fifth lens 5 and the sixth lens 6 are all plastic aspherical lenses, and the third lens 3 and the fourth lens 4 are glass spherical lenses or plastic aspherical lenses;
[0080] The lens satisfies the following conditional formula:
[0081] 5.2 <TTL / Fno<8.8
[0082] 7.68 <TTL / F<8.6
[0083] Wherein, TTL is the distance from the object side of the first lens 1 to the image plane, Fno is the aperture value of the lens, and F is the effective focal length of the lens.
[0084] By limiting the ratio of the distance from the object side to the image plane of the first lens 1 of the lens to the aperture value, a suitable size and a corresponding aperture range of the diaphragm can be selected to ensure the brightness range of the lens while meeting the structural size.
[0085] By limiting the ratio of the distance from the object side of the first lens 1 to the image plane to the effective focal length, a corresponding optical lens can be selected according to the structural size and the focus image plane position required by the finished device.
[0086] Through the design of combining glass spherical lens and plastic aspherical lens, the glass lens can be selectively placed in the position of the third lens 3 or the fourth lens 4 to improve the performance of the overall optical lens. At the same time, each lens is designed accordingly, so that the lens meets DFOV≥99°, TTL≤17, and the lens has the advantages of high definition and small distortion, which reduces the difficulty of later correction of distortion; and the lens has the function of day and night parfocality, so that the lens has good imaging quality when switching between day and night.
[0087] Specifically, the lens satisfies the following conditional formula:
[0088] 19.82 <DFOV / ImgH<28.7
[0089] Wherein, DFOV is the diagonal imaging angle of the lens, and ImgH is the diagonal imaging diameter of the lens.
[0090] By satisfying the above conditional formula and selecting the appropriate target surface size for different field of view angles, the difficulty of later matching of the lens chip and structure can be effectively reduced.
[0091] Specifically, the lens satisfies the following conditional formula:
[0092] 1.8≤ET1 / CT1≤2.4
[0093] Wherein, ET1 is the edge thickness of the first lens 1 , and CT1 is the center thickness of the first lens 1 .
[0094] By satisfying the above conditional expression and adjusting the center thickness and edge thickness of the first lens 1, lenses with different field angles can be obtained, which can cope with the use in different environments.
[0095] Specifically, the lens satisfies the following conditional formula:
[0096] 1.69≤|F1 / F|≤1.87
[0097] Wherein, F1 is the focal length of the first lens 1 .
[0098] By satisfying the above conditional expression, the absolute value of the ratio of the focal length of the lens to the focal length of the first lens 1 is limited, thereby reducing the difficulty of processing the first lens 1 .
[0099] Specifically, the lens satisfies the following conditional formula:
[0100] 3.5≤FG≤5.7
[0101] Among them, FG is the focal length of the glass spherical lens in the lens.
[0102] By satisfying the above conditional formula, changing the focal length of the glass spherical lens in the lens can adjust the performance of the lens working in the infrared state;
[0103] Specifically, the lens satisfies the following conditional formula:
[0104] 0.65≤CTG / F≤0.83
[0105] Among them, CTG is the center thickness of the glass spherical lens in the lens.
[0106] By satisfying the above conditional formula and adjusting the center thickness of the glass spherical lens in the lens and the focal length of the lens, the difficulty of the glass spherical lens in the processing process can be reduced.
[0107] Specifically, the lens satisfies the following conditional formula:
[0108] 2.23≤CT1+CTG≤2.95
[0109] Wherein, CT1 is the center thickness of the first lens 1, and CTG is the center thickness of the glass spherical lens in the lens.
[0110] By satisfying the above conditional formula, the sum of the center thickness of the first lens 1 and the center thickness of the glass spherical lens in the lens can be adjusted, and the performance in the infrared state can be adjusted;
[0111] Specifically, the lens satisfies the following conditional formula:
[0112] 3.34≤ET1+ETG≤4.04
[0113] Among them, ETG is the edge thickness of the glass spherical lens in the lens.
[0114] By satisfying the above conditional formula, the sum of the edge thickness of the first lens 1 and the edge thickness of the glass spherical lens in the lens is adjusted, so that the edge light of the lens can be combed to ensure that the field of view angle is suitable and meets the requirements of the lens use environment.
[0115] The above-mentioned lens may further include a filter 8 for correcting color deviation and / or a protective glass for protecting the photosensitive element located on the imaging surface according to the specific needs of the embodiment. In the absence of specific requirements, the filter 8 or the protective glass may not be used.
[0116] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.
[0117] Example 1
[0118] The present embodiment provides a day-night confocal optical lens, which is composed of a first lens 1, a second lens 2, an aperture 7, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6 and a filter 8 in sequence from the object side to the image side along the optical axis. Incident light passes through the above components in sequence and is finally imaged on the image plane. The first lens 1 has negative optical power, and its object side surface is concave at the near optical axis, and the image side surface is concave at the near optical axis. The second lens 2 has positive optical power, its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The third lens 3 has positive optical power, its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The fourth lens 4 has negative optical power, its object side surface is convex at the near optical axis, and the image side surface is concave at the near optical axis. The fifth lens 5 has positive optical power, its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The sixth lens 6 has positive optical power, its object side surface is convex at the near optical axis, and the image side surface is concave at the near optical axis. The filter is arranged between the sixth lens 6 and the image plane.
[0119] The first lens, the second lens, the fourth lens, the fifth lens and the sixth lens are plastic aspherical lenses, and the third lens is a glass spherical lens.
[0120] Table 1 shows the surface type, radius of curvature, thickness and material properties of each lens in Example 1. The units of the radius of curvature and thickness are both millimeters (mm).
[0121] Table 1 is a table of lens parameters of the lens of Example 1.
[0122]
[0123] In this embodiment, the surface shape x of each aspheric lens can be defined by, but not limited to, the following aspheric surface formula:
[0124]
[0125] Wherein, x is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c=1 / R (i.e., the paraxial curvature c is the reciprocal of the curvature radius R in Table 1 above); k is the cone coefficient; Ai The following Table 2 shows the high-order coefficients A4, A6, A8, A10, A12, A14, and A16 of the aspheric mirror surfaces that can be used in Example 1.
[0126] Table 2 is a table of high-order coefficients of various aspherical mirror surfaces in Example 1.
[0127]
[0128] Please refer to Table 7 for the numerical values of the conditional expressions in this embodiment.
[0129] The specific lens structure of this embodiment is as follows Figure 1 For details of the defocus curve, see Figure 2 , 3 It can be seen that under the condition of 60lp / mm, the switching between visible light and infrared light is not easy to lose focus, and the imaging quality remains almost unchanged; see the spot diagram for details Figure 4 , it can be seen that the aberration is small and the imaging quality is good; for details of the field curvature and distortion curves, see Figure 5 , 6 , it can be seen that the distortion correction is better, which reduces the difficulty of later distortion correction.
[0130] Example 2
[0131] The present embodiment provides a day-night confocal optical lens, which is composed of a first lens 1, a second lens 2, an aperture 7, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6 and a filter 8 in sequence from the object side to the image side along the optical axis. Incident light passes through the above components in sequence and is finally imaged on the image plane. The first lens 1 has negative optical power, and its object side surface is concave at the near optical axis, and the image side surface is concave at the near optical axis. The second lens 2 has positive optical power, its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The third lens 3 has positive optical power, its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The fourth lens 4 has negative optical power, its object side surface is convex at the near optical axis, and the image side surface is concave at the near optical axis. The fifth lens 5 has positive optical power, its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The sixth lens 6 has positive optical power, its object side surface is convex at the near optical axis, and the image side surface is concave at the near optical axis. The filter is arranged between the sixth lens 6 and the image plane.
[0132] The first lens, the second lens, the fourth lens, the fifth lens and the sixth lens are plastic aspherical lenses, and the third lens is a glass spherical lens.
[0133] Table 3 shows the surface type, radius of curvature, thickness and material properties of each lens in Example 2. The units of the radius of curvature and thickness are both millimeters (mm).
[0134] Table 3 is a table of lens parameters of Example 2.
[0135]
[0136] In this embodiment, each aspheric surface shape can be defined by the formula (1) in the above embodiment 1. Table 4 below shows the high-order coefficients A4, A6, A8, A10, A12, A14, and A16 of each aspheric mirror surface that can be used in embodiment 1.
[0137] Table 4 is a table of high-order coefficients of each aspherical mirror surface in Example 2.
[0138]
[0139] Please refer to Table 7 for the numerical values of the conditional expressions in this embodiment.
[0140] The specific lens structure of this embodiment is as follows Figure 7 For details of the defocus curve, see Figure 8 , 9 It can be seen that under the condition of 60lp / mm, the switching between visible light and infrared light is not easy to lose focus, and the imaging quality remains almost unchanged; see the spot diagram for details Fig.10 , it can be seen that the aberration is small and the imaging quality is good; for details of the field curvature and distortion curves, see Fig.11 , 12 , it can be seen that the distortion correction is better, which reduces the difficulty of later distortion correction.
[0141] Example 3
[0142] The present embodiment provides a day-night confocal optical lens, which is composed of a first lens 1, a second lens 2, a third lens 3, an aperture 7, a fourth lens 4, a fifth lens 5, a sixth lens 6 and a filter 8 in sequence from the object side to the image side along the optical axis. Incident light passes through the above components in sequence and is finally imaged on the image plane. The first lens 1 has negative optical power, and its object side surface is concave at the near optical axis, and the image side surface is concave at the near optical axis. The second lens 2 has positive optical power, and its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The third lens 3 has positive optical power, and its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The fourth lens 4 has positive optical power, and its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The fifth lens 5 has positive optical power, and its object side surface is convex at the near optical axis, and the image side surface is concave at the near optical axis. The sixth lens 6 has positive optical power, and its object side surface is convex at the near optical axis, and the image side surface is convex at the near optical axis. The filter is arranged between the sixth lens 6 and the image plane.
[0143] The first lens, the second lens, the third lens, the fifth lens and the sixth lens are plastic aspherical lenses, and the fourth lens is a glass spherical lens.
[0144] Table 5 shows the surface type, radius of curvature, thickness and material properties of each lens in Example 3. The units of the radius of curvature and thickness are both millimeters (mm).
[0145] Table 5 is a table of lens parameters of Example 3.
[0146]
[0147] In this embodiment, each aspheric surface shape can be defined by the formula (1) in the above embodiment 1. Table 6 below shows the high-order coefficients A4, A6, A8, A10, A12, A14, and A16 of each aspheric mirror surface that can be used in embodiment 1.
[0148] Table 6 is a table of high-order coefficients of each aspherical mirror surface in Example 3.
[0149]
[0150] Please refer to Table 7 for the numerical values of the conditional expressions in this embodiment.
[0151] The specific lens structure of this embodiment is as follows Fig.13 For details of the defocus curve, see Fig.14 , 15 It can be seen that under the condition of 60lp / mm, the switching between visible light and infrared light is not easy to lose focus, and the imaging quality remains almost unchanged; see the spot diagram for details Fig.16 , it can be seen that the aberration is small and the imaging quality is good; for details of the field curvature and distortion curves, see Fig.17 , 18 , it can be seen that the distortion correction is better, which reduces the difficulty of later distortion correction.
[0152] Table 7 is a numerical table of conditional formulas related to Examples 1-3.
[0153] Embodiment 1 Embodiment 2 Embodiment 3 TTL 16.7 11.53 14.74 Fno 1.9 2.2 2 Dfov 99.6 108.2 106.2 Ih 5.02 3.81 4.78 ET1 2.98 2.54 3.19 CT1 1.5 1.12 1.36 ETG 0.91 0.81 0.84 CTG 1.44 1.12 1.2 F1 -4.02 -2.36 -2.99 FG 5.67 3.58 4.72 F 2.17 1.37 1.78
[0154] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are illustrative and cannot be understood as limitations of the present invention. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present invention.
Claims
1. A day-night confocal optical lens, characterized in that: Along the optical axis from the object side to the image side, it is composed of: A first lens having negative optical power, wherein the object side surface of the first lens at a near optical axis is concave, and the image side surface of the first lens is concave; a second lens having positive refractive power, wherein the object-side surface of the second lens at the near optical axis is convex, and the image-side surface of the second lens is convex; a third lens element having positive refractive power, wherein the image-side surface of the third lens element at the near optical axis is convex; a fourth lens element having negative or positive refractive power, wherein the object-side surface of the fourth lens element at a near optical axis is convex; a fifth lens element having positive refractive power, wherein the object side surface of the fifth lens element at a near optical axis is convex; a sixth lens having positive refractive power, wherein the object side surface of the sixth lens at a position close to the optical axis is convex; The first lens, the second lens, the fifth lens and the sixth lens are all plastic aspheric lenses, and the third lens and the fourth lens are glass spherical lenses or plastic aspheric lenses; The lens satisfies the following conditional formula: 5.2 <TTL / Fno<8.8 7.68 <TTL / F<8.6 Wherein, TTL is the distance from the object side of the first lens to the image plane, Fno is the aperture value of the lens, and F is the effective focal length of the lens.
2. The day-night confocal optical lens according to claim 1, characterized in that: The lens satisfies the following conditional formula: 19.82 <DFOV / ImgH<28.7 Wherein, DFOV is the diagonal imaging angle of the lens, and ImgH is the diagonal imaging diameter of the lens.
3. The day-night confocal optical lens according to claim 1, characterized in that: The lens satisfies the following conditional formula: 1.8≤ET1 / CT1≤2.4 Wherein, ET1 is the edge thickness of the first lens, and CT1 is the center thickness of the first lens.
4. The day-night confocal optical lens according to claim 1, characterized in that: The lens satisfies the following conditional formula: 1.69≤|F1 / F|≤1.87 Wherein, F1 is the focal length of the first lens.
5. The day-night confocal optical lens according to claim 1, characterized in that: The lens satisfies the following conditional formula: 3.5≤FG≤5.7 Among them, FG is the focal length of the glass spherical lens in the lens.
6. The day-night confocal optical lens according to claim 1, characterized in that: The lens satisfies the following conditional formula: 0.65≤CTG / F≤0.83 Among them, CTG is the center thickness of the glass spherical lens in the lens.
7. The day-night confocal optical lens according to claim 1, characterized in that: The lens satisfies the following conditional formula: 2.23≤CT1+CTG≤2.95 Among them, CT1 is the center thickness of the first lens, and CTG is the center thickness of the glass spherical lens in the lens.
8. The day-night confocal optical lens according to claim 1, characterized in that: The lens satisfies the following conditional formula: 3.34≤ET1+ETG≤4.04 Among them, ETG is the edge thickness of the glass spherical lens in the lens.