Visible-to-near-infrared light and long-wave infrared light coaxial optical lens

Abstract

The invention discloses a visible-to-near-infrared light and long-wave infrared light coaxial optical system, which comprises a visible-to-near-infrared light optical system and a long-wave infrared light optical system which are coaxially arranged, the visible light-to-near infrared light optical system comprises a common dome cover QZ, a first lens L1, a second balsaming lens L2 and a third lens L3 which are sequentially arranged from an object side to an image side; wherein the first lens L1 is a concave-convex lens with negative diopter; the second balsaming lens L2 is a positive diopter convex lens; the third lens L3 is a plane reflection lens with the diopter being zero. The long-wave infrared light optical system comprises a shared spherical cover QZ, a first lens K1, a second lens K2 and a third lens K3 which are sequentially arranged from the object space to the image space. Wherein the first lens K1 is a convex-concave lens with positive diopter; the second lens K2 is a concave lens with negative diopter; the third lens K3 is a convex-plane lens with positive diopter; and the shared ball cover QZ is a convex-concave lens with negative diopter. The system has the characteristics of good imaging effect, small size, light weight and the like.

Description

Technical Field

[0001] This invention relates to a novel coaxial optical lens that can transmit near-infrared and long-wave infrared light, belonging to the field of infrared surveillance technology. Background Technology

[0002] As a medium for converting optical signals into electrical signals, the seeker head has long played a crucial role in tracking and monitoring. However, when tracking targets, the single bands of visible light and long-wave infrared light are easily misled by interference substances released by the target, leading to target loss. Fusion of visible-to-near-infrared and long-wave infrared light can effectively avoid interference images. However, traditional fusion methods use ZnS and fluorides as front-end objectives, followed by a mirror assembly to split the visible-to-near-infrared and long-wave infrared light, and then a post-compensation assembly for focusing. This method is not only very expensive, but the large number of mirrors also leads to a significant decrease in transmittance, and greatly increases weight and assembly difficulty. This invention employs a mechanical coaxial approach, achieving high transmittance and high-resolution detection without the need for a cooling mechanism, resulting in a high response rate. It achieves the same coaxial effect as traditional beam-splitting optics at a very low cost, and is small in size and lightweight, making it suitable for deployment on airborne aircraft. Summary of the Invention

[0003] This invention provides a novel coaxial optical lens for visible near-infrared and long-wave infrared light, suitable for visible near-infrared and long-wave infrared light seeker applications.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A visible-to-near-infrared and long-wave infrared coaxial optical system includes a visible-to-near-infrared optical system and a long-wave infrared optical system arranged coaxially.

[0006] The visible light to near-infrared optical system includes, from the object side to the image side, a common spherical dome QZ, a first lens L1, a second cemented lens L2, and a third lens L3; wherein, the first lens L1 is a concave-convex lens with negative refractive power; the second cemented lens L2 is a convex-convex lens with positive refractive power; and the third lens L3 is a plane reflecting lens with zero refractive power.

[0007] The long-wave infrared optical system includes, from the object side to the image side, a common spherical dome QZ, a first lens K1, a second lens K2, and a third lens K3; wherein, the first lens K1 is a convex-concave lens with positive refractive power; the second lens K2 is a concave-concave lens with negative refractive power; and the third lens K3 is a convex-planar lens with positive refractive power.

[0008] The shared spherical cover QZ is shared by the visible to near-infrared optical system and the long-wave infrared optical system; the shared spherical cover QZ is a convex-concave lens with negative refractive power;

[0009] The first lens M1 has a mounting hole at its center. The first lens L1 and the second cemented lens L2 are mounted in the mounting hole. The third lens L3 is located between the first lens M1 and the second lens M2.

[0010] The aforementioned optical system is suitable for coaxial guidance and tracking systems that operate day and night, and as the front objective lens for tracking and detection equipment for fixed or moving targets. The visible-to-near-infrared lens has a focal length of 26.4 mm, a total system length of 41.28 mm, a numerical aperture of 4.0, and is compatible with a 1280*1024-2.7 μm detector. The long-wave infrared optical system has a focal length of 50 mm, a total system length of 56.7 mm, a numerical aperture of 1.0, and is compatible with a 640*512-12 μm detector. The visible-to-near-infrared and infrared lenses share a front-end multispectral zinc sulfide dome for protection of the guidance system.

[0011] To ensure image conjugation, cost-effectiveness, size and weight considerations, and ease of post-processing assembly, this application employs a separate fusion design, significantly reducing the optical aperture of the aforementioned lens suitable for long-distance guidance and tracking. The combined focal length f' of the visible to near-infrared optical system is 26.4mm, the system F-number is 4.0, the diagonal imaging plane is 4.43mm, the horizontal field of view is 7.5°, and the response band is 420-1100nm; the combined focal length f' of the long-wave infrared optical system is 50mm, the system F-number is 1.0, the diagonal imaging plane is 9.84mm, the horizontal field of view is 8.68°, and the response band is 8-12um.

[0012] The aforementioned visible to near-infrared optical system is suitable for visible to near-infrared optical modules with a size of 1280*1024-2.7um; the long-wave infrared optical system is suitable for uncooled lenses with a long-wave detector module of 640*512-12um.

[0013] In the aforementioned visible to near-infrared optical system, except for the shared dome QZ, the first lens L1, the second cemented lens L2, and the third lens L3 are all made of glass. To effectively protect the internal optical lens group, the shared dome QZ is made of multispectral zinc sulfide. The shared dome QZ, the first lens L1, and the second cemented lens L2 are all spherical mirrors, meaning that the visible to near-infrared optical system uses aspherical surfaces for aberration optimization.

[0014] To further ensure imaging quality, the radius of curvature of the side of the shared dome is 45±0.005mm, and the radius of curvature of the side of the image is 42±0.005mm.

[0015] The radius of curvature of the object side of the first lens L1 is -6.446±0.005mm, and the radius of curvature of the image side of the first lens L1 is -7.4±0.005mm.

[0016] The second cemented lens L2 is formed by cementing a lens A, a lens B, and a lens C together from the object side to the image side. The radius of curvature of the object side of the cemented lens A is 12.8±0.005mm, and the radius of curvature of the image side of the cemented lens A is 44.34±0.005mm. The radius of curvature of the object side of the cemented lens B is 44.34±0.005mm, and the radius of curvature of the image side of the cemented lens B is 7.37±0.005mm. The radius of curvature of the object side of the cemented lens C is 7.37±0.005mm, and the radius of curvature of the image side of the cemented lens C is -28.43±0.005mm.

[0017] The object side and image side of the third lens L3 are both planes with infinite radii of curvature.

[0018] To further ensure image quality, the center-to-center distance between the shared dome QZ and the first lens L1 is 4.67±0.005mm, the center-to-center distance between the first lens L1 and the second cemented lens L2 is 0.406±0.005mm, the center-to-center distance between the second cemented lens L2 and the third lens L3 is 7.44±0.005mm, and the center-to-center distance from the third lens L3 to the image plane is 18.326±0.005mm.

[0019] To further ensure imaging stability and quality, the center thickness of the shared dome QZ is 3.00±0.02mm; the center thickness of the first lens L1 is 1.9±0.02mm; the center thickness of the second cemented lens L2 is 6.25±0.02mm, of which the center thickness of cemented lens A is 2.50±0.02mm, the center thickness of cemented lens B is 1.25±0.02mm, and the center thickness of cemented lens C is 2.50±0.02mm; and the center thickness of the third lens L3 is 1.000±0.05mm. The third lens L3 is a single-sided reflecting mirror, and its thickness does not affect the reflected optical path.

[0020] To balance image quality and lens size, the outer diameter of the common dome QZ is 66~70mm, the outer diameter of the first lens L1 is 7~8.5mm, the outer diameter of the second cemented lens L2 is 8.5±0.1mm, and the outer diameter of the third lens L3 is 9mm-12mm.

[0021] The optical element shared by the aforementioned visible to near-infrared optical system and long-wave infrared optical system is only the shared spherical cover QZ.

[0022] The aforementioned long-wave infrared lenses, except for sharing a dome, are made of different crystal materials.

[0023] In the long-wave infrared optical system, the shared dome QZ and the first lens K1 are both spherical mirrors; the object side of the second lens K2 is a binary surface type, and the image side of the second lens K2 is a spherical surface type; the object side of the third lens K3 is an aspherical surface type, and the image side of the third lens K3 is a planar surface type.

[0024] The first lens K1 is made of chalcogenide glass 206, the second lens K2 is made of ZnSe, and the third lens K3 is made of multispectral zinc sulfide. Using a combination of materials for each lens minimizes the overall length of the optical system and enhances the achromatic and thermal correction capabilities of long-wave infrared light at high and low temperatures. Simultaneously, it avoids the excessive use of aspherical surfaces due to a single material, which could lead to excessively small tolerances in the overall optical system during processing and assembly. This indirectly reduces the processing and assembly requirements of product components and improves the product's economic efficiency.

[0025] To further ensure imaging quality, the radius of curvature of the object-side surface of the shared spherical cover QZ is 45±0.005mm, and the radius of curvature of the image-side surface of the shared spherical cover QZ is 42±0.005mm; the radius of curvature of the object-side surface of the first lens K1 is 33.258±0.005mm, and the radius of curvature of the image-side surface of the first lens K1 is 58.135±0.005mm; the radius of curvature of the object-side surface of the second lens K2 is -119.8545±0.005mm, and the radius of curvature of the image-side surface of the second lens K2 is 69.24±0.005mm; the radius of curvature of the object-side surface of the third lens K3 is 47.7566±0.005mm, and the radius of curvature of the image-side surface of the third lens K3 is an infinitely large plane.

[0026] To further ensure imaging quality, the center-to-center distance between the shared dome QZ and the first lens K1 is 2.5 ± 0.005 mm; to allow installation space for the reflector, the center-to-center distance between the first lens K1 and the second lens K2 is 16 ± 0.005 mm; the center-to-center distance between the second lens K2 and the third lens K3 is 9.744 ± 0.005 mm. The center-to-center distance between the third lens K3 and the 1 mm thick germanium protective window of the detector is 10.057 ± 0.005 mm, and the center-to-center distance from the detector to the protective window is 1 mm.

[0027] To further ensure imaging stability and quality, the center thickness of the common spherical cover QZ is 3.00±0.02mm, the center thickness of the first lens K1 is 8.00±0.02mm, the center thickness of the second lens K2 is 2.5±0.02mm, and the center thickness of the third lens K3 is 2.9±0.02mm.

[0028] To balance image quality and lens size, the outer diameter of the common dome QZ is 66~70mm, the outer diameter of the first lens K1 is 47~50mm, the outer diameter of the second lens K2 is 26~28mm, and the outer diameter of the third lens K3 is 21±0.1mm.

[0029] A filter film is deposited on the object side of the first lens K1 in the long-wavelength optical system. Ge film is used as an adhesive layer to bond with the chalcogenide glass substrate to solve the problem of poor adhesion between the film and the substrate. The film material has a good lattice match with the chalcogenide glass material. In order to obtain a wider cutoff range and lower reflectivity in the long-wavelength band, YbF3 is selected as a low refractive index film material. ZnS is selected as a medium refractive index material to connect YbF3 and Ge. This film structure can effectively reduce the residual stress of the film system. At the same time, ZnS can also serve as the outermost protective film material. Based on the above ideas, after designing and optimizing different film systems, a 12-layer film system structure of chalcogenide glass substrate / Ge / ZnS / YbF3 / ZnS / Ge / ZnS / YbF3 / ZnS / Ge / ZnS / YbF3 / ZnS / Air was obtained. The specific film layers and thicknesses are: Sub / aHbMcLdMeHfMgLhMiHjMkLlM / A, where Sub represents chalcogenide glass substrate, A represents air, H represents Ge, L represents YbF3, and M represents ZnS; the physical thicknesses of each layer corresponding to a1 are 150±20nm, 50±30nm, 170±30nm, 50±30nm, 180±20nm, 50±30nm, 200±20nm, 50±30nm, 260±30nm, 50±30nm, 900±50nm, and 400±50nm, respectively.

[0030] During the preparation of the above-mentioned filter film, the initial vacuum degree is better than 5.0 × 10⁻⁶. -4 The baking temperature was 80-150℃. Ion source parameters were set as follows: cathode voltage 100-300V, ion beam current 1-4A. Before evaporation, the substrate was bombarded with ions for 3-10 minutes to clean it and improve film adhesion. During film deposition, ion source-assisted deposition was used to increase film density and improve stress matching. All film materials were thermally evaporated using an electron gun. The evaporation rate for ZnS was controlled at 0.2-1.5 nm / s, for YbF3 at 0.2-1 nm / s, and for Ge at 0.2-0.8 nm / s.

[0031] Any techniques not mentioned in this invention are based on existing technologies.

[0032] This invention is applicable to coaxial optical lenses for visible near-infrared light and long-wave infrared light, and has the following beneficial effects:

[0033] 1. Applicable to both visible and near-infrared optical mechanisms and long-wave infrared detectors respectively, with an overall combined optical path of 56.7mm, small combined size, minimal obstruction of long-wave infrared light by the visible and near-infrared optical system, and high reliability;

[0034] 2. Large imaging area and high resolution. Visible and near-infrared lenses can be used with 1280*1024 camera modules with a pixel size of up to 2.7um, while long-wave infrared lenses can be used with 640*512 camera modules with a pixel size of up to 12um.

[0035] 3. The visible near-infrared optical system has an F-number of 4.0, a small overall optical lens aperture, and a wide response band of 420-1100nm, which can save costs to the greatest extent and reduce the mounting volume. The long-wave infrared optical system has an F-number of 1.0, which can effectively improve the long-distance detection of long-wave infrared.

[0036] 4. The visible near-infrared light system uses multiple spherical and cemented lenses, which can effectively reduce the number of lenses and reduce product costs. The long-wave infrared light system uses multiple aspherical lenses, which can effectively correct the aberrations generated by the system. Both optical systems have good imaging quality and transfer functions that reach or approach the diffraction limit.

[0037] 5. The long-wave infrared optical system adopts a variety of materials design, which shortens the overall optical path and has the function of high and low temperature thermal difference elimination. It can adapt to temperature changes from -40 degrees to +80 degrees without producing obvious image quality changes.

[0038] 6. By using a long-wave infrared lens with an opening, light can be embedded in the center of the long-wave infrared and the focused image plane can be reflected to the side of the infrared optical system. This can effectively improve the overall coaxial stability of the optical axis, reduce the overall weight of the guidance system, and significantly reduce the difficulty of overall assembly and adjustment.

[0039] 7. Coating a filter film on the surface of the first lens of the long-wavelength optical system can effectively prevent other light rays from the visible to near-infrared range from passing through the lens of the infrared optical system and falling onto the reflector of the visible to near-infrared optical system, thus preventing stray light. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of an optical system for a coaxial optical lens that can transmit near-infrared and long-wave infrared light.

[0041] Figure 2 This is a schematic diagram of the visible and near-infrared light optical path of the coaxial optical lens applicable to visible and near-infrared light and long-wave infrared light as described in this invention.

[0042] Figure 3 The specific embodiment shows the optical transfer function curve of the near-infrared optical system at 200 lp / mm in the 400-1100 nm range;

[0043] Figure 4 The specific embodiment shows the light spot pattern of the near-infrared optical system in the 400-1100nm range;

[0044] Figure 5 The field curvature and distortion patterns of the near-infrared optical system in the 400-1100nm range are visible in the specific embodiments.

[0045] Figure 6 The specific embodiment shows the relative illumination diagram of the near-infrared optical system in the 400-1100nm range;

[0046] Figure 7 This is a schematic diagram of the long-wave infrared optical path of the coaxial optical lens applicable to visible near-infrared light and long-wave infrared light as described in this invention;

[0047] Figure 8 This is a graph showing the optical transfer function (42 lp / mm) of a specific embodiment of a long-wave infrared optical system in a 20-degree environment at 8-12 μm.

[0048] Figure 9 This is a graph showing the optical transfer function (42 lp / mm) of a specific embodiment of the long-wave infrared optical system in a -40 degree environment at 8-12 μm.

[0049] Figure 10 This is a graph showing the optical transfer function (42 lp / mm) of a specific embodiment of the long-wave infrared optical system in an environment of +80 degrees Celsius at 8-12 μm.

[0050] Figure 11 This is a specific embodiment of the long-wave infrared optical system with a light spot pattern of 8-12µm;

[0051] Figure 12 These are field curvature and distortion diagrams of a specific embodiment of a long-wave infrared optical system in the 8-12µm range;

[0052] Figure 13 This is a relative illumination diagram of a long-wave infrared optical system in the 8-12µm range in a specific embodiment;

[0053] Figure 14 This is an overall assembly diagram of the coaxial optical lens belt structure that can display near-infrared and long-wave infrared light.

[0054] Figure 15 This is an exploded view of the overall structure of the coaxial optical lens belt that can be seen in near-infrared and long-wave infrared light.

[0055] Figure 16 This is a schematic diagram of the object-side filter film of the first lens K1 in a long-wavelength optical system.

[0056] Figure 17Simulated transmittance of the object-side filter film of the first lens K1 in a long-wavelength optical system (I).

[0057] Figure 18 Simulated transmittance of the filter film on the object side of the first lens K1 in a long-wavelength optical system (II). Detailed Implementation

[0058] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0059] Figure 1 shows a schematic diagram of the optical system layout of a novel coaxial optical lens for visible light to near-infrared light and long-wave infrared light, including a visible light to near-infrared light optical system and a long-wave infrared light optical system.

[0060] like Figure 2 The diagram shows a schematic of the visible-to-near-infrared optical system layout of a novel visible-to-near-infrared and long-wave infrared coaxial optical lens in this embodiment. The visible-to-near-infrared optical system layout includes the following components arranged sequentially from the object side to the image side along the optical axis: a common dome QZ with negative optical power, a first lens L1 with negative optical power, a second cemented lens L2 with positive optical power, a third lens L3 (reflector) with near-zero optical power, and a visible light image plane.

[0061] From the object side to the image side, the two sides of the shared spherical dome QZ are, in sequence, the first object-side surface S1 and the first image-side surface S2; the two sides of the first lens L1 are, in sequence, the second object-side surface S3 and the second image-side surface S4; the two sides of the second cemented lens are, in sequence, the third object-side surface S5 and the third image-side surface S8; the second cemented lens L2 is composed of cemented lens A, cemented lens B, and cemented lens C cemented sequentially from the object side to the image side, as shown below. Figure 2 As shown, the formed curved surfaces are S5~8 in sequence; the third lens is a reflecting plane S9 with a 45-degree angle to the object side and the image side; the first object side S1, the first image side S2, the second object side S3, the second image side S4, the third object side S5, and the third image side S8 are all spherical lenses, with the aperture stop on the third object side S5.

[0062] The shared dome QZ is made of multispectral zinc sulfide, which has high abrasion resistance, hardness, and chemical stability, effectively protecting the internal optical lens assembly. It also exhibits very high transmittance from 0.35µm to 12µm, making it an ideal front-end protection window for broadband imaging. Both the first lens L1 and the second cemented lens L2 use spherical mirror surfaces. To achieve a shorter compression length, reduce the optical volume of the lens assembly, and maximize image quality under these constraints, the second cemented lens L2 employs a triple-cementing process, which helps correct aberrations in the optical system.

[0063] Table 1 Technical parameters of the visible light to near-infrared optical system of the present invention embodiment

[0064]

[0065] Table 2 Specific parameters of the visible light to near-infrared optical system of the present invention embodiment.

[0066]

[0067] Figures 3 to 6 The optical transfer function curve, spot pattern, field curvature and distortion diagram, and relative illumination diagram of the visible-to-near-infrared optical system at +20°C in this embodiment represent the overall resolution level of the optical system and the resolution of the image. Combined with a 1280*1024-12μm detector, a resolution of 185 line pairs is required. Figure 3 It can be seen that the optical transfer function of this system has good contrast across the entire field of view, resulting in excellent image resolution and contrast, and clear imaging from visible light to near-infrared. Figure 4 It can be seen that the system's speckle is very small, and the system has a very strong ability to recognize fine objects; from Figure 5 It can be seen that the system distortion is ≤0.2%, and the distortion from the visible light to the near-infrared light spectrum does not require software correction; Figure 6 It can be seen that when the relative illumination of the system is above 0.9, it can greatly reduce the grayscale error at the center and edge of the image and reduce the occurrence of weak edge field energy.

[0068] like Figure 7 The diagram shows a schematic layout of the long-wave infrared optical system of a novel coaxial optical lens for visible light to near-infrared light and long-wave infrared light in this embodiment. The long-wave infrared optical system includes the following components arranged sequentially from the object side to the image side along the optical axis: a common dome QZ with negative optical power, a first lens K1 with positive optical power, a second lens K2 with negative optical power, a third lens K3 with positive optical power, a long-wave infrared window, and a long-wave infrared image plane.

[0069] In this embodiment, from the object side to the image side, the two sides QZ of the shared spherical cover are sequentially the first object side surface S1 and the first image side surface S2. The two sides of the first lens K1 are sequentially the second object side surface M1 and the second image side surface M2. The two sides of the second lens K2 are sequentially the third object side surface M3 and the third image side surface M4. The two sides of the third lens K2 are sequentially the fourth object side surface M5 and the fourth image side surface M6. The first object side surface S1, the first image side surface S2, the second object side surface M1, the second image side surface M2, and the third image side surface M4 are all spherical surfaces. The third object side surface M3 is a binary surface. The fourth object side surface M5 is an aspherical surface. The fourth image side surface is an M-plane surface, wherein the aperture stop is on the second object side surface M1.

[0070] The shared dome QZ is made of multispectral zinc sulfide, which has high abrasion resistance, hardness, and chemical stability, effectively protecting the internal optical lens assembly. It also exhibits very high transmittance from 0.35µm to 12µm, making it an ideal front-end protection window for broadband imaging. The first lens K1 is made of chalcogenide glass 206, effectively reducing material costs. The second lens K2 is made of ZnSe, and its lens surface M3 uses a binary surface, effectively correcting optical aberrations in long-wave infrared optics. The third lens K3 is made of multispectral zinc sulfide. This combination of materials for each lens minimizes the overall length of the optical system and enhances the achromatic and thermal correction capabilities of long-wave infrared at high and low temperatures. Simultaneously, it avoids the excessive use of aspherical surfaces due to a single material, which could lead to excessively small tolerances in the overall optical system during processing and assembly, indirectly reducing the processing and assembly requirements of product components and improving product economy.

[0071] Table 3 Technical parameters of the long-wave infrared optical system in the embodiments of the present invention

[0072]

[0073] Table 4 Specific parameters of the long-wave infrared optical system in the embodiments of the present invention

[0074]

[0075] The aspherical equations used in Table 4 are:

[0076]

[0077] The meanings of each quantity are as follows:

[0078] ZA: The lens sagitta along the optical axis of the aspherical surface;

[0079] R: Radius of curvature at the intersection of the surface and the optical axis;

[0080] Y: Half-aperture of the lens perpendicular to the optical axis;

[0081] k: Conic coefficient;

[0082] Coefficients for surfaces A, B, C, D, and E; see Table 5 for specific coefficients.

[0083] Table 5

[0084]

[0085] The two-dimensional surface equations used in Table 4 are as follows:

[0086]

[0087] in:

[0088] Φ: Phase of the diffraction plane;

[0089] Y: Half-aperture of the lens perpendicular to the optical axis;

[0090] Phase coefficients of diffraction planes A1, A2, and A3.

[0091] The specific coefficients for the binary surface are shown in Table 6.

[0092] Table 6

[0093]

[0094] Figures 8 to 13 As an example, optical transfer function (OPF) curves at +20°C, -40°C, and +80°C, along with spot patterns, field curvature and distortion diagrams, and relative illumination diagrams, represent the overall resolution level of the optical system and its ability to resolve images. This is designed to achieve a 42-line-pair resolution when used with a 640x512 12μm detector. Figures 8 to 10 It can be seen that the optical transfer function of this system is close to the diffraction limit, resulting in excellent image resolution and contrast, while also exhibiting good imaging performance at both high and low temperatures; Figure 11 It can be seen that the system's speckle is very small, and the system has a very strong ability to recognize fine objects; from Figure 12 It can be seen that the system distortion is ≤2%, the overall image plane distortion is small, and it can effectively avoid obvious image distortion; from Figure 13 It can be seen that the system's relative illumination is above 0.89, which can greatly reduce the grayscale error at the center and edge of the image and reduce the occurrence of the "pot lid" phenomenon in image quality.

[0095] like Figure 14-15 The diagram shows the overall assembly drawing and exploded view of the visible-to-near-infrared and long-wave infrared coaxial optical lens in this embodiment. To ensure the coaxiality of the visible-to-near-infrared and long-wave infrared optical paths in this novel visible-to-near-infrared and long-wave infrared coaxial optical lens, the first lens K1, the second lens K2, and the third lens K3 in the long-wave infrared optical system need to be assembled using a cap N3, a retaining ring N4, a retaining ring N5, and a sealing ring N6, respectively. Figure 14The first step is to install the visible-to-near-infrared (VNIIR) lens module N7 in the long-wavelength primary lens mount N8. The second step is to install the reflector onto the VNIIR mount N2 using silicone rubber. Then, install the pre-assembled VNIIR lens module N1 (including the first lens L1 and the second cemented lens L2) onto the VNIIR mount N2, and roughly confirm the height of N1 within N2 using a height gauge. The fourth step is to use a separate flip-up fixture to fix the shared dome QZ on the guide housing, as it is mounted on the front of the overall optical system, facilitating the coaxial adjustment of the VNIIR and long-wavelength infrared optical paths. The fifth step is to adjust the front-to-back position of N1 within N2 and the rotational position of N2 within K1 to align the focal plane of the VNIIR optical system with the image plane of the VNIIR lens module N7, achieving optimal overall imaging clarity. Finally, use UV adhesive to fix the position of N1 within N2 and the rotational position of N2 within K1. The sixth step involves using the thin shims and the waist-shaped slots on the primary lens mount to align the center point of the infrared long-wavelength optical module with the imaging optical axis of the visible to near-infrared optical module, aligning them with the collimator or distant target. This method effectively reduces the difficulty of coaxial assembly and adjustment in traditional multi-optical systems and significantly improves the reliability of the final product.

[0096] Figure 16 This is a schematic diagram of the filter film on the object side of the first lens K1 in a long-wavelength optical system. The filter film structure is: first lens K1 / Ge / ZnS / YbF3 / ZnS / Ge / ZnS / YbF3 / ZnS / Ge / ZnS / YbF3 / ZnS / Air, which is a 12-layer film structure. Starting from the first lens K1, the physical thicknesses of each layer are 150nm, 50nm, 170nm, 50nm, 180nm, 50nm, 200nm, 50nm, 260nm, 50nm, 900nm, and 400nm, respectively.

[0097] This example uses a Cathay 1150 fully automatic one-button infrared coating machine. Crystal control employs a Membrane Technology MXC-3B quartz crystal film thickness controller, which measures film thickness by utilizing changes in the oscillation frequency of a quartz crystal. The ion source is a hollow cathode Hall-type ion source; by rationally controlling the ion energy, the density of the deposited film can be improved, enhancing its optical and mechanical properties. The vacuum chamber uses a combination of a dry pump and a molecular pump system to achieve the required vacuum level, which is measured using a thermocouple.

[0098] After multiple experimental verifications and optimizations, the preparation process and process parameters were determined. The initial vacuum degree was better than 5.0 × 10⁻⁶. -4The baking temperature was 120℃. Ion source parameters were set as follows: cathode voltage 200V, ion beam current 3A. Before evaporation, the substrate was bombarded with ions for 5 minutes to clean it and improve film adhesion. During film deposition, ion source-assisted deposition was used to increase film density and improve stress matching. All film materials were thermally evaporated using an electron gun. The evaporation rates for ZnS, YbF3, and Ge were controlled at 0.6 nm / s, 0.6 nm / s, and 0.5 nm / s, respectively.

[0099] Spectral performance testing: The transmittance of the thin film was tested using a Thermo Fisher Scientific IS50 Fourier transform infrared spectrometer. The obtained spectral curve met the requirements of the infrared detection system. The test results are as follows: Figure 17-18 As shown, this coating method can prevent other visible to near-infrared light from falling onto the L3 reflector through K1, thus avoiding stray light phenomena in the visible to near-infrared imaging mechanism.

[0100] Environmental performance testing:

[0101] (1) Adhesion test: 3M tape with a width of 1cm was used to stick firmly to the surface of the film. After the tape was quickly pulled up from the edge of the part in the vertical direction towards the surface, the film did not fall off or get damaged.

[0102] (2) Immersion test: The sample was completely immersed in distilled water or deionized water. After 96 hours, the membrane layer showed no abnormalities.

[0103] (3) High and low temperature test: The sample was placed in a high and low temperature test chamber and kept at -40℃ for half an hour. Then, the temperature was quickly switched from -40℃ to 90℃ for half an hour, and then quickly switched from 90℃ to -40℃ for half an hour. The cycle was repeated 12 times. The film layer showed no abnormalities.

[0104] (4) Constant temperature and humidity test: The sample was placed in a constant temperature and humidity test chamber, the temperature was set to 85℃ and the humidity to 85%RH, and the test was continuously verified for 12 hours. No abnormalities were found in the film layer.

[0105] (5) Salt spray test: The temperature is 35±2℃ and the concentration is 4.9%~5.1% NaCl solution. Spray continuously for 72 hours. No abnormality is found in the film layer.

[0106] (6) Boiling test: After heating in boiling water for 6 hours, the film layer showed no abnormalities.

Claims

1. A coaxial optical system for visible near-infrared light and long-wave infrared light, characterized in that: This includes a coaxially configured visible to near-infrared optical system and a long-wave infrared optical system; The visible light to near-infrared optical system includes, from the object side to the image side, a common spherical dome QZ, a first lens L1, a second cemented lens L2, and a third lens L3; wherein, the first lens L1 is a concave-convex lens with negative refractive power; the second cemented lens L2 is a convex-convex lens with positive refractive power; and the third lens L3 is a plane reflecting lens with zero refractive power. The long-wave infrared optical system includes, from the object side to the image side, a common spherical dome QZ, a first lens K1, a second lens K2, and a third lens K3; wherein, the first lens K1 is a convex-concave lens with positive refractive power; the second lens K2 is a concave-concave lens with negative refractive power; and the third lens K3 is a convex-planar lens with positive refractive power. The shared spherical cover QZ is shared by the visible to near-infrared optical system and the long-wave infrared optical system; the shared spherical cover QZ is a convex-concave lens with negative refractive power; The first lens M1 has a mounting hole at its center. The first lens L1 and the second cemented lens L2 are mounted in the mounting hole. The third lens L3 is located between the first lens M1 and the second lens M2.

2. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1, characterized in that: The detector adapted for the visible to near-infrared optical system is 1280*1024-2.7um; the detector adapted for the long-wave infrared optical system is 640*512-12um.

3. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1 or 2, characterized in that: The combined focal length f' of the visible to near-infrared optical system is 26.4 mm, the system F number is 4.0, the diagonal imaging plane is 4.43 mm, the horizontal field of view is 7.5°, and the response band is 420-1100 nm. The combined focal length f' of the long-wave infrared optical system is 50mm, the system F number is 1.0, the diagonal imaging plane is 9.84mm, the horizontal field of view is 8.68°, and the response band is 8-12um.

4. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1 or 2, characterized in that: In the visible light to near-infrared optical system, the first lens L1, the second cemented lens L2, and the third lens L3 are all made of glass; the shared spherical cover QZ is made of multispectral zinc sulfide; and the shared spherical cover QZ, the first lens L1, and the second cemented lens L2 are all spherical mirrors.

5. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1 or 2, characterized in that: In the visible light to near-infrared optical system, the radius of curvature of the side of the shared dome is 45±0.005mm, and the radius of curvature of the side of the shared dome is 42±0.005mm. The radius of curvature of the object side of the first lens L1 is -6.446±0.005mm, and the radius of curvature of the image side of the first lens L1 is -7.4±0.005mm. The second cemented lens L2 is formed by cementing a lens A, a lens B, and a lens C together from the object side to the image side. The radius of curvature of the object side of the cemented lens A is 12.8±0.005mm, and the radius of curvature of the image side of the cemented lens A is 44.34±0.005mm. The radius of curvature of the object side of the cemented lens B is 44.34±0.005mm, and the radius of curvature of the image side of the cemented lens B is 7.37±0.005mm. The radius of curvature of the object side of the cemented lens C is 7.37±0.005mm, and the radius of curvature of the image side of the cemented lens C is -28.43±0.005mm.

6. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1 or 2, characterized in that: In the visible to near-infrared optical system, the center distance between the shared dome QZ and the first lens L1 is 4.67±0.005mm, the center distance between the first lens L1 and the second cemented lens L2 is 0.406±0.005mm, the center distance between the second cemented lens L2 and the third lens L3 is 7.44±0.005mm, and the center distance from the third lens L3 to the image plane is 18.326±0.005mm.

7. The visible near-infrared and long-wave infrared coaxial optical system according to claim 1 or 2, characterized in that: In the visible to near-infrared optical system, the center thickness of the shared dome QZ is 3.00±0.02mm; the center thickness of the first lens L1 is 1.9±0.02mm; the center thickness of the second cemented lens L2 is 6.25±0.02mm, and the second cemented lens L2 is formed by cementing a cemented A lens, a cemented B lens, and a cemented C lens from the object side to the image side, wherein the center thickness of the cemented A lens is 2.50±0.02mm, the center thickness of the cemented B lens is 1.25±0.02mm, and the center thickness of the cemented C lens is 2.50±0.02mm; the center thickness of the third lens L3 is 1.000±0.05mm, and the third lens L3 is a single-sided reflecting mirror.

8. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1 or 2, characterized in that: The outer diameter of the common dome QZ is 66~70mm, the outer diameter of the first lens L1 is 7~8.5mm, the outer diameter of the second cemented lens L2 is 8.5±0.1mm, and the outer diameter of the third lens L3 is 9mm-12mm.

9. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1 or 2, characterized in that: In the long-wave infrared optical system, the shared dome QZ and the first lens K1 are both spherical mirrors; the object side of the second lens K2 is a binary surface type, and the image side of the second lens K2 is a spherical surface type; the object side of the third lens K3 is an aspherical surface type, and the image side of the third lens K3 is a planar surface type.

10. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1 or 2, characterized in that: The first lens K1 is made of chalcogenide glass 206, the second lens K2 is made of ZnSe, and the third lens K3 is made of multispectral zinc sulfide.

11. The visible near-infrared and long-wave infrared coaxial optical system according to claim 1 or 2, characterized in that: In the long-wave infrared optical system, the radius of curvature of the object-side surface of the shared spherical cover QZ is 45±0.005mm, and the radius of curvature of the image-side surface of the shared spherical cover QZ is 42±0.005mm; the radius of curvature of the object-side surface of the first lens K1 is 33.258±0.005mm, and the radius of curvature of the image-side surface of the first lens K1 is 58.135±0.005mm; the radius of curvature of the object-side surface of the second lens K2 is -119.8545±0.005mm, and the radius of curvature of the image-side surface of the second lens K2 is 69.24±0.005mm; the radius of curvature of the object-side surface of the third lens K3 is 47.7566±0.005mm, and the radius of curvature of the image-side surface of the third lens K3 is an infinitely large plane.

12. The visible near-infrared and long-wave infrared coaxial optical system according to claim 1 or 2, characterized in that: In the long-wave infrared optical system, the center distance between the shared dome QZ and the first lens K1 is 2.5±0.005mm; the center distance between the first lens K1 and the second lens K2 is 16±0.005mm; and the center distance between the second lens K2 and the third lens K3 is 9.744±0.005mm.

13. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 1 or 2, characterized in that: The center thickness of the common dome cover QZ is 3.00±0.02mm, the center thickness of the first lens K1 is 8.00±0.02mm, the center thickness of the second lens K2 is 2.5±0.02mm, and the center thickness of the third lens K3 is 2.9±0.02mm.

14. The visible near-infrared and long-wave infrared coaxial optical system according to claim 1 or 2, characterized in that: The outer diameter of the common dome QZ is 66~70mm, the outer diameter of the first lens K1 is 47~50mm, the outer diameter of the second lens K2 is 26~28mm, and the outer diameter of the third lens K3 is 21±0.1mm.

15. The visible near-infrared and long-wave infrared coaxial optical system according to claim 1 or 2, characterized in that: The object side of the first lens K1 is coated with a filter film, which is a 12-layer film structure, specifically: first lens K1 / Ge / ZnS / YbF3 / ZnS / Ge / ZnS / YbF3 / ZnS / Ge / ZnS / YbF3 / ZnS / Air. Starting from the first lens K1, the physical thicknesses of each layer are 150±20nm, 50±30nm, 170±30nm, 50±30nm, 180±20nm, 50±30nm, 200±20nm, 50±30nm, 260±30nm, 50±30nm, 900±50nm, and 400±50nm.

16. The coaxial optical system for visible near-infrared light and long-wave infrared light according to claim 15, characterized in that: During the preparation of the filter film, all film materials were thermally evaporated using an electron gun. The evaporation rate of ZnS was controlled at 0.2-1.5 nm / s, the evaporation rate of YbF3 was controlled at 0.2-1 nm / s, and the evaporation rate of Ge was controlled at 0.2-0.8 nm / s.

Images