A large field of view, large relative aperture micro-light night vision lens and a design method thereof

Abstract

This invention relates to a large field-of-view, large relative aperture low-light night vision lens and its design method, belonging to the field of optoelectronic technology, and solves the problem that it is difficult to simultaneously achieve a large field of view and a large relative aperture in existing technologies. The low-light night vision lens is constructed using a reverse telephoto objective lens structure, consisting of a negative front group and a positive rear group; the negative front group is implemented using a single meniscus lens; the positive rear group is implemented using a double Gaussian deformable objective lens. The focal length, field of view, and relative aperture are determined; based on the chromatic aberration equation of the system chromatic aberration C with angular magnification A and the distance d between the front and rear groups, C is determined after determining the angular magnification A and the distance d between the front and rear groups; the focal length, F-number of the front group, the focal length, the F-number of the rear group, and the total system length are obtained based on the angular magnification and the distance between the front and rear groups, and used as initial structural parameters; the initial structure and parameters are optimized using optical design software to obtain the final low-light night vision lens. This achieves a low-light night vision lens with a large field of view, a large relative aperture, and low distortion.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and in particular to a large field of view, large relative aperture low-light night vision lens and its design method. Background Technology

[0002] Low-light night vision technology refers to the use of natural light reflected from targets, such as starlight, moonlight, and atmospheric glow, in low-light conditions at night. By using a low-light night vision detector to enhance the signal strength of targets in low-light environments, it enables the detection and identification of small targets. Low-light night vision technology is one of the advanced optoelectronic technologies. It applies the photoelectric effect principle and optoelectronic imaging methods, offering advantages such as small size, light weight, clear images, good concealment, and strong imaging depth. It extends the visual capabilities of the human eye to a certain extent and has wide applications in both military and civilian fields. For example, equipping low-light night vision devices on armed helicopters and armored vehicles enables nighttime targeting of dynamic targets at a distance of 300-400 meters, effective reconnaissance of terrain and features, and navigation. Modern warfare demands high-resolution imaging systems with all-weather operational capabilities. Furthermore, the objective lens, as a key component in a low-light night vision system, directly affects the system's detection performance; therefore, research on low-light night vision imaging systems is of great significance.

[0003] Low-light night vision lenses are widely used in nighttime security monitoring, but existing double Gaussian deformable lenses have difficulty achieving a large field of view, large relative aperture, and small distortion. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a large field of view, large relative aperture low-light night vision lens and its design method, in order to solve the problem that existing double Gaussian deformable lenses are difficult to achieve a large field of view under large relative aperture conditions.

[0005] On one hand, embodiments of the present invention provide a low-light night vision lens with a large field of view and a large relative aperture, which consists of a negative front group and a positive rear group;

[0006] The negative front group is achieved using a single meniscus lens; the positive rear group is achieved using a double Gaussian deformable objective lens.

[0007] The rear-mounted lens group includes a second lens, a third lens, a first cemented lens, a second cemented lens, and eighth to tenth lenses arranged sequentially from the object side to the image side.

[0008] The second lens has negative optical power, and its object side is convex while its image side is concave.

[0009] The third lens has negative optical power, and both its object-side and image-side surfaces are concave.

[0010] The first cemented lens has positive optical power, and both its object-side and image-side surfaces are convex.

[0011] The aperture stop is located on the image side of the first cemented lens;

[0012] The second cemented lens has negative optical power, and both its object-side and image-side surfaces are concave.

[0013] The eighth lens has positive optical power, with a concave object side and a convex image side.

[0014] The ninth lens has positive optical power, and both its object-side and image-side surfaces are convex.

[0015] The tenth lens has positive optical power, with its object side being convex and its image side being concave.

[0016] Furthermore, the first cemented lens is composed of a fourth lens and a fifth lens cemented together; the second cemented lens is composed of a sixth lens and a seventh lens cemented together.

[0017] The fourth lens in the first cemented lens has positive optical power, and its object side is convex and its image side is concave.

[0018] The fifth lens in the first cemented lens has positive optical power, and both its object side and image side are convex.

[0019] The sixth lens in the second cemented lens has negative optical power, and its object side is concave while its image side is convex.

[0020] The seventh lens in the second cemented lens has negative optical power, and both its object side and image side are concave.

[0021] Furthermore, all lenses used in the negative front group and the positive rear group are spherical lenses.

[0022] Furthermore, the low-light night vision lens has an F-number of 1.4, a full field of view of 67°, a focal length of f' of 20mm, a total length of 111.5mm, and is applicable to a wavelength range of 0.4-0.95μm.

[0023] Furthermore, the entrance pupil diameter ENPD of the low-light night vision lens and the total system length TTL satisfy the following condition: ENPD / TTL≥0.10.

[0024] Furthermore, the maximum field of view 2ω of the low-light night vision lens, the focal length f' of the entire lens, and the image height H corresponding to the maximum field of view satisfy the following relationship: (2ω×f') / H≥53°.

[0025] On the other hand, embodiments of the present invention provide a design method for a large field of view and large relative aperture low-light night vision lens, the method comprising:

[0026] Determine the focal length of low-light night vision lenses according to the Johnson criterion;

[0027] Determine the required field of view and relative aperture for low-light night vision lenses;

[0028] The lens is constructed using a reverse telephoto objective, which consists of a negative front group and a positive rear group. Based on the chromatic aberration formula, optical power formula, and focal length formula, the chromatic aberration equation is obtained, which expresses the system chromatic aberration C as a function of angular magnification A and the distance between the front and rear groups, d. The angular magnification A and the distance between the front and rear groups, d, are determined based on the angular magnification A and the distance between the front and rear groups, respectively. The focal length, F-number, and total system length of the front and rear groups are then obtained based on these parameters, and are used as initial structural parameters. A single meniscus lens is selected to represent the front group based on its F-number. A double Gaussian deformable objective with nine lenses is selected as the initial structure of the rear group, based on the rear group's F-number and the lens's field of view. The initial structure and parameters are optimized using optical design software to obtain the final low-light night vision lens.

[0029] Furthermore, the color difference equation is:

[0030]

[0031] Where v1 and v2 are the dispersion coefficients of the front and rear groups, respectively, h1 is the incident height of the front group, h2 is the incident height of the rear group, and f' is the focal length of the entire lens.

[0032] Furthermore, based on the angular magnification A and the distance between the front and rear groups d, the focal length of the front group, the F-number of the front group, the focal length of the rear group, the F-number of the rear group, and the total system length are obtained, including:

[0033] Front focal length:

[0034] Front group F number:

[0035] Rear focal length:

[0036] The equivalent F-number of the latter group:

[0037] Total system length: TTL = d + Af';

[0038] In the formula, F is the F-number of the entire lens, and f' is the focal length of the entire lens.

[0039] Furthermore, the initial structure and initial structural parameters are optimized based on optical design software, including: after determining the initial structural parameters, inputting the initial structural parameters into the optical design software and setting variables and constraints, the variables including the radius, thickness and material of each lens, and the constraints including size constraints and aberration constraints; adjusting the lens parameters using the optimization theory in the optical design software until a lens structure that meets the conditions is obtained.

[0040] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0041] 1. The optical lens provided by this invention has reasonable settings for the optical power of each lens and the position of the aperture stop. On the one hand, it achieves a large field of view, with a diagonal full field of view of 67°, which meets the requirements of the detection range. On the other hand, the lens has a large relative aperture, is miniaturized, and has high imaging quality, which better balances the design requirements of the field of view and aperture.

[0042] 2. It uses 10 spherical lenses with specific optical power, and through specific surface shape matching, the lens distortion is less than 3.5%, and the production cost is low, which meets the requirements of mass production and has high-quality imaging.

[0043] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0044] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0045] Figure 1 This is a schematic diagram of an ideal optical system model of a large field-of-view, large relative aperture low-light night vision lens and its design method according to the present invention.

[0046] Figure 2 This is a schematic diagram of the chromatic aberration curve of a large field of view, large relative aperture low-light night vision lens and its design method according to the present invention.

[0047] Figure 3 This is a schematic diagram of the synthesis system to be optimized for a large field of view, large relative aperture low-light night vision lens and its design method according to the present invention.

[0048] Figure 4 These are schematic diagrams of the optical structure and optical path of embodiments one to three of the present invention, which describe a large field of view, large relative aperture low-light night vision lens and its design method.

[0049] Figure 5 This is a field curvature-distortion curve diagram of an embodiment of the present invention, which describes a large field of view, large relative aperture low-light night vision lens and its design method.

[0050] Figure 6 This is an MTF curve of an embodiment of the present invention, which describes a large field of view, large relative aperture low-light night vision lens and its design method.

[0051] Figure 7 This is a field curvature-distortion curve diagram of a second embodiment of the present invention, which describes a large field of view, large relative aperture low-light night vision lens and its design method.

[0052] Figure 8 This is an MTF curve of a second embodiment of the present invention, which describes a large field-of-view, large relative aperture low-light night vision lens and its design method.

[0053] Figure 9 This is a field curvature-distortion curve diagram of Embodiment 3 of the present invention, which describes a large field of view, large relative aperture low-light night vision lens and its design method.

[0054] Figure 10 This is an MTF curve of Embodiment 3 of the present invention, which describes a large field-of-view, large relative aperture low-light night vision lens and its design method.

[0055] Figure 11 This is a standard dot diagram illustrating the large field-of-view, large relative aperture low-light night vision lens and its design method according to the present invention. Detailed Implementation

[0056] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0057] A specific embodiment of the present invention discloses a large field of view, large relative aperture low-light night vision lens, such as... Figure 4 As shown.

[0058] This low-light night vision lens consists of a negative front group and a positive rear group;

[0059] The negative front group is achieved using a single meniscus lens; the positive rear group is achieved using a double Gaussian deformable objective lens.

[0060] The rear-mounted lens group includes a second lens, a third lens, a first cemented lens, a second cemented lens, and eighth to tenth lenses arranged sequentially from the object side to the image side.

[0061] The second lens has negative optical power, and its object side is convex while its image side is concave.

[0062] The third lens has negative optical power, and both its object-side and image-side surfaces are concave.

[0063] The first cemented lens has positive optical power, and both its object-side and image-side surfaces are convex.

[0064] The aperture stop is located on the image side of the first cemented lens;

[0065] The second cemented lens has negative optical power, and both its object-side and image-side surfaces are concave.

[0066] The eighth lens has positive optical power, with a concave object side and a convex image side.

[0067] The ninth lens has positive optical power, and both its object-side and image-side surfaces are convex.

[0068] The tenth lens has positive optical power, with its object side being convex and its image side being concave.

[0069] The first cemented lens is composed of a fourth lens and a fifth lens cemented together; the second cemented lens is composed of a sixth lens and a seventh lens cemented together.

[0070] The fourth lens in the first cemented lens has positive optical power, and its object side is convex and its image side is concave.

[0071] The fifth lens in the first cemented lens has positive optical power, and both its object side and image side are convex.

[0072] The sixth lens in the second cemented lens has negative optical power, and its object side is concave while its image side is convex.

[0073] The seventh lens in the second cemented lens has negative optical power, and both its object side and image side are concave.

[0074] All lenses used in the negative front group and the positive rear group are spherical lenses.

[0075] The low-light night vision lens has an F-number of 1.4, a full field of view of 67°, a focal length of f' of 20mm, a total length of 111.5mm, and is applicable to a wavelength range of 0.4-0.95μm.

[0076] The entrance pupil diameter ENPD of the low-light night vision lens and the total system length TTL satisfy the following condition: ENPD / TTL≥0.10.

[0077] The maximum field of view 2ω of the low-light night vision lens, the focal length f' of the entire lens, and the image height H corresponding to the maximum field of view satisfy the following condition: (2ω×f') / H≥53°.

[0078] The design parameters of each lens in the optical lens of the present invention, provided in a specific embodiment of the low-light night vision lens, are shown in Table 1.

[0079] Table 1

[0080]

[0081]

[0082] In this embodiment, the optical lens field curvature-distortion curve and MTF curve are respectively as follows: Figure 5 , Figure 6 As shown.

[0083] The design parameters of each lens in the optical lens two provided in the specific embodiment two of the low-light night vision lens of the present invention are shown in Table 2.

[0084] Table 2

[0085]

[0086]

[0087] In this embodiment, the field curvature-distortion curve and the MTF curve are respectively as follows: Figure 7 , Figure 8 As shown.

[0088] The design parameters of each lens in the optical lens three provided in the specific embodiment three of the low-light night vision lens of the present invention are shown in Table 3.

[0089] Table 3

[0090]

[0091] In this embodiment, the field curvature-distortion curve and MTF curve of optical lens three are respectively as follows: Figure 9 and Figure 10 As shown.

[0092] Figure 5 , Figure 7 , Figure 9 The field curvature-distortion curves of the lenses are shown. The distortion is 3.3% at a diagonal half field of view of 33.45°, and the field curvature is less than 0.12mm, which does not affect the image quality. This indicates that the field curvature and distortion correction of optical lenses one, two, and three are good.

[0093] Figure 6 , Figure 8 , Figure 10 The modulation transfer function (MTF) curves of the lens across the entire field of view are shown. As can be seen from the figure, the MTF curve of the center field of view is greater than 0.4 at the cutoff frequency, and the MTF curves of the other fields of view are greater than 0.3 at the cutoff frequency, indicating good image quality that meets the usage requirements.

[0094] Figure 11A standard dot plot of the low-light night vision objective is presented. It can be seen that the RMS blur radius of each field of view is below 12μm, indicating that the energy concentration of the system is good.

[0095] A specific embodiment of the method of the present invention discloses a design method for a low-light night vision lens with a large field of view and a large relative aperture, the specific steps of which include S1-S6.

[0096] Step S1: Determine the focal length of the low-light night vision lens according to the Johnson criterion; determine the required field of view and relative aperture of the low-light night vision lens.

[0097] Specifically, according to the Johnson criterion, the focal length of the low-light night vision lens is calculated from the recognition distance, target size, and the imaging size corresponding to the number of 4-line-pair strip cycles, including:

[0098]

[0099] In the formula, l is the recognition distance, a is the imaging size corresponding to the number of cycles of 4 line pairs, f' is the focal length of the low-light night vision lens, and h is the target size.

[0100] In a specific embodiment of the method of this invention, the ability to identify a 3m × 3m target at a distance of 600m is required. According to the Johnson criterion, the critical size of the target contains 4 line pairs. This invention selects a detector with a pixel size of 12μm × 12μm, resulting in a corresponding focal length f' of 19.2mm for the low-light night vision camera objective. Therefore, this invention selects f' = 20mm as the system focal length.

[0101] Determine the required field of view and relative aperture for low-light night vision lenses, specifically including:

[0102] The required field of view for the low-light night vision lens is determined according to design requirements. In one specific embodiment of the present invention, a field of view angle of 67° is selected.

[0103] The relative aperture of the system can be estimated using the following formula:

[0104]

[0105] Where E represents the target illumination on the image plane; D / f' represents the relative aperture of the objective lens; L represents the target brightness; and τ represents the system transmission factor.

[0106] As shown in equation (1), the illuminance of the target on the image plane is proportional to the square of the relative aperture. The larger the relative aperture, the greater the illuminance of the target on the image plane. A larger relative aperture indicates a stronger light-gathering ability of the system and better detection performance at night. However, for systems with a large field of view and a large relative aperture, off-axis wide beams often produce large aberrations, and the edge rays of off-axis wide beams produce large dispersion. Taking into account aberration correction, size and cost factors, a specific embodiment of the present invention selects a relative aperture of 1:1.4 for the objective lens.

[0107] Step S2: Construct the lens using a reverse telephoto objective lens structure, which consists of a negative front group and a positive rear group.

[0108] The ideal optical system model simplified from the structure of the telephoto lens is as follows: Figure 1 As shown.

[0109] The introduction of the negative front group magnifies the half field of view ω of the principal ray by a factor of A, raises the incident height h1 by a factor of A to h2, and thus makes the back intercept l' a factor of A of the focal length.

[0110] Specifically,

[0111] Where ω is the half field of view of the principal ray of the maximum field of view, and the front negative lens converts it into ω'.

[0112] The back intercept l' can be expressed as:

[0113]

[0114] Where u' is the image-side aperture angle of the rear group.

[0115] Step S3: Based on the color difference formula, optical power formula, and focal length formula, obtain the color difference equation of the system color difference C as a function of angular magnification A and front-to-back group spacing d; determine the angular magnification A and front-to-back group spacing d based on the color difference equation.

[0116] When the spatial refractive index n' = 1

[0117] Where C1 is the color difference of the first group, v d The dispersion coefficient of the front group of glass is... The optical power of the front group;

[0118] for Figure 1 The chromatic aberration formula for the separated double lens shown satisfies...

[0119]

[0120] From the optical power formula:

[0121] but

[0122] Wherein, the height of the principal ray in the first lens is h. p .

[0123] From the trigonometric function relations, we can derive:

[0124] Will and Substitution

[0125] The optical power of the front group can be obtained as follows:

[0126] The focal length of the front element is:

[0127] The focal length of the rear element is:

[0128] From equations (3)-(6), the color difference equation can be derived as follows:

[0129]

[0130] Where C represents the chromatic aberration of the low-light night vision lens, C1 represents the chromatic aberration of the front group, C2 represents the chromatic aberration of the rear group, v1 and v2 are the dispersion coefficients of the front and rear groups respectively, h1 is the incident height of the front group, h2 is the incident height of the rear group, f1' is the focal length of the front group, f2' is the focal length of the rear group, f' is the focal length of the entire lens, and d is the distance between the front and rear groups. For the front group optical power, This refers to the optical power of the rear group.

[0131] In a specific embodiment of the method of the present invention, two commonly used glass materials, H-K9L and H-ZF1, are selected as the front and rear groups, respectively. The color difference of the system is numerically simulated and calculated. The color difference curve of the system as a function of the initial structural parameter angular magnification A and the distance d between the front and rear groups is obtained by equation (7), as follows: Figure 2 As shown. Because the double Gaussian objectives have a relatively large thickness when used as the rear group, the angular magnification A is selected between 1.5 and 2. As the angular magnification increases, the chromatic aberration decreases. Figure 2 The six curves from top to bottom represent A = 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0, respectively; as the spacing d increases, the chromatic difference decreases. Considering the overall system length, if the angular magnification A is too large, a single front element cannot achieve the corresponding compression ratio, leading to an increase in system length. Therefore, A = 1.75 and d = 70 mm were ultimately selected.

[0132] Step S4: Based on the angular magnification A and the distance between the front and rear groups d, obtain the focal length of the front group, the F-number of the front group, the focal length of the rear group, the F-number of the rear group, and the total length of the system. Use the focal length of the front group, the F-number of the front group, the focal length of the rear group, the F-number of the rear group, and the total length of the system as the initial structural parameters.

[0133] From equations (4) and (5), the focal length of the front group can be obtained:

[0134]

[0135] Front group F number:

[0136] Rear focal length:

[0137] The equivalent F-number of the latter group:

[0138] Total system length: TTL = d + Af'(12)

[0139] Where F is the F-number for the entire shot.

[0140] Specifically, the front group F-number is obtained from the definition of the F-number and the front group focal length f1'.

[0141] From the definition of the F-number, we get:

[0142]

[0143] Substituting equations (8) and (14) into (13), we get:

[0144]

[0145] From the formula for the focal length of a split lens, we can obtain:

[0146]

[0147] The focal length of the rear element can be obtained:

[0148]

[0149] Substituting equation (8) into equation (17) yields the rear focal length as shown in equation (10).

[0150] The equivalent F-number of the second lens is obtained by applying the modified deflection formula. When the object distance is finite, the equivalent F-number of the lens with finite conjugate distance is defined as the equivalent F-number of the rear lens, as shown in equation (11).

[0151] Under the ideal model, the total length of the system is as shown in equation (12).

[0152] In a specific embodiment of the present invention, when A = 1.75 and d = 70 mm, the primary design parameters of the front and rear groups are shown in Table 4.

[0153] Table 4

[0154]

[0155] Step S5: Select a single meniscus lens to realize the front group according to the F-number of the front group; select a double Gaussian deformable objective lens with a total of 9 lenses as the initial structure of the rear group according to the F-number of the rear group and the field of view of the lens.

[0156] The front group has an F-number of 7.46 and is achieved using a single meniscus lens, with both spherical surfaces curved towards the aperture stop. Since the double Gaussian objective and its morphing design are suitable for medium to large apertures and / or medium to large fields of view, from a physical perspective, lenses with approximately symmetrical structures exhibit smaller asymmetric aberrations, such as coma, distortion, and chromatic aberration. Furthermore, on-axis point aberrations are easier to correct. Considering parameters such as the rear group's F-number and field of view, a double Gaussian morphing objective with a centrally located aperture stop and a total of 9 lenses was chosen as the initial structure for the rear group.

[0157] Insert the front group in front of the rear group to form a composite optical system. Figure 3 As shown, when the spacing is 70mm, the system focal length is 19.98mm. Figure 3 It can be seen that the front and rear group spacing calculated from the main surface is 69.99 mm and the back intercept is 34.54 mm, both of which are consistent with the ideal optical model.

[0158] Step S6: Optimize the initial structure and initial structural parameters based on optical design software to obtain the final low-light night vision lens.

[0159] The initial structure and initial structural parameters are optimized using optical design software, including: after determining the initial structural parameters, inputting the initial structural parameters into the optical design software and setting variables and constraints, the variables including the radius, thickness and material of each lens, and the constraints including size constraints and aberration constraints; and adjusting the lens parameters using the optimization theory in the optical design software until a lens structure that meets the conditions is obtained.

[0160] The initial structural parameters include the front group focal length, front group F-number, rear group focal length, rear group F-number, and total system length. The back intercept of the optical system and the diagonal image plane length are also included.

[0161] After optimization, the parameters of the low-light night vision lens are shown in Tables 1-3 of Examples 1 to 3.

[0162] This invention, based on an ideal optical model of a telephoto lens and the theory of eliminating primary chromatic aberration with a dual-lens split lens, designs a low-light night vision lens with a large field of view and a large relative aperture. A negative power lens is added as the front group of the optical system to the dual Gaussian deformable lens, achieving a large field of view, a large relative aperture, and relatively low distortion. Design results show that the optical system has a compact structure, good imaging quality, and a full-field modulation transfer function higher than 0.35 at a spatial frequency of 41.6 lp / mm, with distortion less than 3.80%. The system designed in this invention uses ordinary glass grades, allowing for relatively loose processing and assembly tolerances, meeting the needs of actual mass production, and can be widely used in day / night observation and aiming scopes.

[0163] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0164] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-light night vision lens with a large field of view and a large relative aperture, characterized in that, This low-light night vision lens consists of a negative front group and a positive rear group; The negative front group is achieved using a single meniscus lens; the positive rear group is achieved using a double Gaussian deformable objective lens. The rear-mounted lens group includes a second lens, a third lens, a first cemented lens, a second cemented lens, and eighth to tenth lenses arranged sequentially from the object side to the image side. The second lens has negative optical power, and its object side is convex while its image side is concave. The third lens has negative optical power, and both its object-side and image-side surfaces are concave. The first cemented lens has positive optical power, and both its object side and image side are convex. The first cemented lens is composed of a fourth lens and a fifth lens cemented together. The fourth lens in the first cemented lens has positive optical power, and its object side is convex and its image side is concave. The fifth lens in the first cemented lens has positive optical power, and both its object side and image side are convex. The aperture stop is located on the image side of the first cemented lens; The second cemented lens has negative optical power, and both its object-side and image-side surfaces are concave. The second cemented lens is composed of a sixth lens and a seventh lens cemented together; the sixth lens in the second cemented lens has negative optical power, its object side is concave, and its image side is convex; the seventh lens in the second cemented lens has negative optical power, and both its object side and image side are concave. The eighth lens has positive optical power, with a concave object side and a convex image side. The ninth lens has positive optical power, and both its object-side and image-side surfaces are convex. The tenth lens has positive optical power, with its object side being convex and its image side being concave.

2. The low-light night vision lens according to claim 1, characterized in that, All lenses used in the negative front group and the positive rear group are spherical lenses.

3. The low-light night vision lens according to claim 1, characterized in that, The low-light night vision lens has an F-number of 1.4, a full field of view of 67°, and a focal length of... It measures 20mm in diameter and has a total length of 111.5mm, with an applicable wavelength range of 0.4-0.95μm.

4. The low-light night vision lens according to claim 1, characterized in that, The entrance pupil diameter ENPD of the low-light night vision lens and the total system length TTL satisfy the following condition: ENPD / TTL≥0.

10.

5. The low-light night vision lens according to claim 1, characterized in that, The maximum field of view of the low-light night vision lens is 2ω, and the focal length of the entire lens is... The image height H corresponding to the maximum field of view angle satisfies: (2ω× ) / H≥53°.

6. A design method for the low-light night vision lens as described in claim 1, characterized in that, The method includes: Determine the focal length of low-light night vision lenses according to the Johnson criterion; Determine the required field of view and relative aperture for low-light night vision lenses; The lens is constructed using a reverse telephoto objective lens, which consists of a negative front group and a positive rear group. Based on the chromatic aberration formula, optical power formula, and focal length formula, the chromatic aberration equations of the system chromatic aberration C as a function of angular magnification A and the distance d between the front and rear groups are obtained. The angular magnification A and the spacing d between the front and rear groups are determined based on the color difference equation. Based on the angular magnification A and the front-to-back group spacing d, the focal length of the front group, the F-number of the front group, the focal length of the rear group, the F-number of the rear group, and the total system length are obtained, and the focal length of the front group, the F-number of the front group, the focal length of the rear group, the F-number of the rear group, and the total system length are used as initial structural parameters. The front group is constructed by selecting a single meniscus lens based on the F-number of the front group; a double Gaussian deformable objective lens with a total of 9 lenses is selected as the initial structure of the rear group based on the F-number of the rear group and the field of view of the lens; the final low-light night vision lens is obtained by optimizing the above initial structure and initial structure parameters based on optical design software.

7. The design method of the low-light night vision lens according to claim 6, characterized in that, The color difference equation is: in, and , h1 and h2 are the dispersion coefficients of the front and rear groups, respectively, where h1 is the incident height of the front group and h2 is the incident height of the rear group. This refers to the focal length of the entire lens.

8. The design method of the low-light night vision lens according to claim 6, characterized in that, Based on the angular magnification A and the distance between the front and rear groups d, the focal length of the front group, the F-number of the front group, the focal length of the rear group, the F-number of the rear group, and the total system length are obtained, including: Front focal length: = ; Previous group F number: ; Rear focal length: ; The equivalent F-number of the latter group: ; Total system length: TTL= ; Wherein, F is the F-number for the entire shot. This refers to the focal length of the entire lens.

9. The design method of the low-light night vision lens according to claim 6, characterized in that, The initial structure and initial structural parameters are optimized using optical design software, including: after determining the initial structural parameters, inputting the initial structural parameters into the optical design software and setting variables and constraints, the variables including the radius, thickness and material of each lens, and the constraints including size constraints and aberration constraints; and adjusting the lens parameters using the optimization theory in the optical design software until a lens structure that meets the conditions is obtained.

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