A long focal length short wave infrared imaging lens assembly

Abstract

This invention relates to the field of optical lens technology, specifically disclosing a long focal length short-wave infrared imaging lens assembly. The lens, along its optical axis, sequentially comprises a first positive lens, a second positive lens, a first negative lens, an aperture stop, a third positive lens, a second negative lens, a fourth positive lens, and a filter. The first positive lens is a biconvex lens, the second positive lens is a meniscus positive lens, the first negative lens is a meniscus negative lens, the third positive lens is a meniscus positive lens, the second negative lens is a meniscus negative lens, and the fourth positive lens is a biconvex lens. This invention achieves achromatic aberration across a wide wavelength range of 900nm-1700nm through a precise combination of all ordinary glass materials. Combined with a matching design of thermal expansion coefficients, it achieves passive calorimetry over a wide temperature range of -40℃ to +60℃, while also possessing a 200mm long focal length, a large F2.0 aperture, and a compact size. It exhibits significant advantages such as high light transmission, stable imaging at high and low temperatures, low cost, and ease of mass production.

Description

Technical Field

[0001] This invention relates to the field of optical lens technology, and specifically discloses a long focal length short-wave infrared imaging lens assembly. Background Technology

[0002] Short-wave infrared (SWIR, wavelengths typically covering 900nm-1700nm) imaging technology plays an increasingly important role in military reconnaissance, border monitoring, forest fire prevention, and industrial inspection due to its unique capabilities in penetrating smoke, identifying camouflage, and night vision. With the increasing maturity of high-resolution short-wave infrared focal plane array detector technology, the market demand for high-performance short-wave infrared imaging systems has surged. Current short-wave infrared imaging lenses mainly focus on the development of short focal length, wide-angle lenses. While these lenses offer a large field of view, they are only suitable for close-range night vision imaging or large-area searches, failing to meet the requirements for clear identification and precise tracking of distant targets. Therefore, developing short-wave infrared lenses with long focal lengths (e.g., 200mm and above) has become an urgent need for the industry.

[0003] However, designing a high-performance long-focal-length short-wave infrared lens faces numerous technical challenges:

[0004] First, the short-wave infrared band has a wide range (900nm-1700nm). Under conditions of long focal length and large aperture (such as F2.0), the secondary spectrum and chromatic aberration of the system are extremely difficult to correct. To eliminate chromatic aberration, existing long-focal-length short-wave infrared lenses typically use a large amount of special crystal materials such as calcium fluoride (CaF2) and zinc selenide (ZnSe). Although these crystal materials have low dispersion characteristics, they are often physically and chemically unstable, brittle, and prone to breakage during processing and assembly. They are also sensitive to thermal shock, resulting in low lens yield and extremely high manufacturing costs, making large-scale mass production difficult.

[0005] Secondly, infrared optical systems typically operate in outdoor environments with a wide temperature range (e.g., -40°C to +60°C). The refractive index and dimensions of optical materials and mechanical structures drift with temperature changes, causing focal plane shift (thermal defocusing), which severely affects image sharpness. Many existing short-wave infrared lenses lack effective calorimetric design or rely solely on complex electromechanical active focusing mechanisms to compensate for thermal defocusing. This not only increases the system's size and weight but also reduces its reliability.

[0006] In conclusion, designing a long-focal-length short-wave infrared lens that simultaneously possesses a large relative aperture, excellent chromatic aberration correction capabilities, and passive optical calorimetry is a pressing technical challenge that needs to be addressed in the field of optical design. Summary of the Invention

[0007] The purpose of this invention is to provide a long focal length short-wave infrared imaging lens assembly to at least solve one of the aforementioned problems in the prior art.

[0008] Specifically, the present invention is achieved through the following technical solution:

[0009] A long focal length short-wave infrared imaging lens assembly includes a lens assembly, which consists of a first positive lens, a second positive lens, a first negative lens, an aperture stop, a third positive lens, a second negative lens, a fourth positive lens, and a filter, arranged sequentially from the light incident direction to the light exit direction.

[0010] The first positive lens is a biconvex lens, which satisfies the following:

[0011] ,in, These are the refractive index and Abbe number of the first positive lens, respectively;

[0012] The second positive lens is a meniscus lens, which satisfies:

[0013] ,in, These are the refractive index and Abbe number of the second positive lens, respectively.

[0014] The first negative lens is a biconcave lens, which satisfies the following:

[0015] ,in, These are the refractive index and Abbe number of the first negative lens, respectively;

[0016] The third positive lens is a meniscus positive lens, which satisfies the following:

[0017] ,in, These are the refractive index and Abbe number of the third positive lens, respectively.

[0018] The second negative lens is a meniscus negative lens, which satisfies:

[0019] ,in, These are the refractive index and Abbe number of the second negative lens, respectively.

[0020] The fourth positive lens is a biconvex lens, which satisfies the following:

[0021] ,in, These are the refractive index and Abbe number of the fourth positive lens, respectively.

[0022] Furthermore, the coefficients of thermal expansion of the first positive lens, the second positive lens, the first negative lens, the third positive lens, the second negative lens, and the fourth positive lens satisfy the following conditions within the temperature range of -40℃ to +60℃:

[0023] The coefficient of thermal expansion of the first positive lens is ;

[0024] The coefficient of thermal expansion of the second positive lens is ;

[0025] The coefficient of thermal expansion of the first negative lens is ;

[0026] The coefficient of thermal expansion of the third positive lens is: ;

[0027] The coefficient of thermal expansion of the second negative lens is ;

[0028] The coefficient of thermal expansion of the fourth positive lens is: .

[0029] Furthermore, it also includes a lens barrel located outside the lens assembly, the lens barrel being adapted to the lens assembly, and the coefficient of thermal expansion of the lens barrel satisfying the following conditions within the range of -40℃ to +60℃:

[0030] The coefficient of thermal expansion of the lens barrel is: .

[0031] Furthermore, the center thickness of each lens in the lens assembly satisfies:

[0032] The center thickness of the first positive lens is ,in, The center thickness of the first positive lens;

[0033] The center thickness of the second positive lens is ,in, The center thickness of the second positive lens;

[0034] The center thickness of the first negative lens is ,in, The center thickness of the first negative lens;

[0035] The center thickness of the third positive lens is ,in, The center thickness of the third positive lens;

[0036] The center thickness of the second negative lens is ,in, The center thickness of the second negative lens;

[0037] The center thickness of the fourth positive lens is ,in, The center thickness of the fourth positive lens.

[0038] Furthermore, the aperture of each lens in the lens assembly satisfies:

[0039] The aperture of the first positive lens is ,in, The aperture of the first positive lens;

[0040] The aperture of the second positive lens is ,in, This is the aperture of the second positive lens;

[0041] The aperture of the first negative lens is ,in, The aperture of the first negative lens;

[0042] The aperture of the third positive lens is ,in, The aperture of the third positive lens;

[0043] The aperture of the second negative lens is ,in, This is the aperture of the second negative lens;

[0044] The aperture of the fourth positive lens is ,in, The aperture of the fourth positive lens is denoted as .

[0045] Furthermore, the center thickness, aperture, and back focal length of the filter in the lens assembly satisfy the following:

[0046] ,

[0047] ,

[0048] ;

[0049] in, These are the center thickness, aperture, and back focal length of the filter, respectively.

[0050] Furthermore, the focal length, aperture number, and total optical length of the lens assembly satisfy the following:

[0051] ;

[0052] in, These are the focal length, aperture number, and total optical length of the lens assembly, respectively.

[0053] Compared with the prior art, the present invention has at least the following advantages and beneficial effects:

[0054] 1. This invention employs a combination of six ordinary glass lenses and a specific high-low combination strategy for the refractive index and Abbe number of each lens. In particular, it uses a special high-dispersion glass with a refractive index greater than 1.9 and an Abbe number less than 20 to make the first negative lens, which strongly compensates for the chromatic aberration generated by the positive lens group. This solves the technical problems of the difficulty in correcting the secondary spectrum and chromatic aberration of long focal length short-wave infrared lenses in the 900nm-1700nm wide band, as well as the high cost, unstable physical properties, and brittle processing of existing technologies that generally rely on crystal materials such as calcium fluoride and zinc selenide. This invention achieves excellent wide-spectrum imaging quality by using only low-cost, high-stability all-glass materials without completely abandoning expensive crystal materials, significantly improving the yield and mass production capability of the lens.

[0055] 2. This invention, based on the principle of passive calorimetry in optics, strictly selects and limits the thermal expansion coefficients of each lens material in the lens assembly, utilizes the difference in temperature sensitivity between the positive and negative lens groups for self-compensation, and introduces a lens barrel structure with an adapted thermal expansion coefficient. This solves the problem of focal plane shift (i.e., thermal defocusing) caused by the temperature drift of material refractive index and surface shape in infrared optical systems within a wide temperature range of -40℃ to +60℃ in the field. It achieves the effect of maintaining a stable focal length and clear imaging in extreme temperature environments without relying on a complex electromechanical active focusing mechanism, effectively reducing the size and weight of the system and improving the overall reliability.

[0056] 3. This invention solves the problems of insufficient light intake and low image signal-to-noise ratio of telephoto lenses in long-distance detection, especially in low-light environments such as night or haze, by designing the light intake of the first lens to be 103mm-104mm. It achieves high light intake and high contrast long-distance detection capability, and significantly improves the system's performance in identifying and tracking weak targets.

[0057] 4. This invention solves the problem of traditional long focal length optical systems being bulky and difficult to integrate by using a compact telephoto optical power distribution architecture. It achieves a compact structure with the total optical length controlled within 210mm. At the same time, combined with the optimized design of optical back focal length and image plane size, it can be perfectly adapted to mainstream high-resolution short-wave infrared detectors, taking into account the application requirements of high performance and miniaturization. Attached Figure Description

[0058] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0059] Figure 1 This is a diagram of the lens optical system of Embodiment 1 of the present invention;

[0060] Figure 2 This is a dot plot of the first embodiment in Example 2 of the present invention at a normal temperature of 20°C;

[0061] Figure 3 This is a dot plot of the first embodiment in Example 2 of the present invention at a low temperature of -40°C.

[0062] Figure 4 This is a dot plot of the first embodiment in Example 2 of the present invention under a high temperature of 60°C.

[0063] Figure 5 The image shows the optical modulation transfer function (MTF) of the first embodiment in Example 2 of this invention at a normal temperature of 20°C.

[0064] Figure 6 The image shows the optical modulation transfer function (MTF) of the first embodiment in Example 2 of this invention at a low temperature of -40°C.

[0065] Figure 7 The image shows the optical modulation transfer function (MTF) of the first embodiment in Example 2 of this invention under a high temperature environment of 60°C.

[0066] Figure 8 This is a distorted image of the first embodiment in Example 2 of the present invention;

[0067] Figure 9 This is a relative illumination diagram of the first embodiment in Example 2 of the present invention;

[0068] Figure 10 This is a diagram of the lens optical system in the second embodiment of Example 2 of the present invention;

[0069] Figure 11 This is a dot plot of the second embodiment in Example 2 of the present invention at a normal temperature of 20°C;

[0070] Figure 12 This is a dot plot of the second embodiment in Example 2 of the present invention at a low temperature of -40°C.

[0071] Figure 13 This is a dot plot of the second embodiment in Example 2 of the present invention under a high temperature of 60°C.

[0072] Figure 14 The image shows the optical modulation transfer function (MTF) of the second embodiment in Example 2 of this invention at a normal temperature of 20°C.

[0073] Figure 15The image shows the optical modulation transfer function (MTF) of the second embodiment in Example 2 of this invention at a low temperature of -40°C.

[0074] Figure 16 The image shows the optical modulation transfer function (MTF) of the second embodiment in Example 2 of this invention under a high temperature environment of 60°C.

[0075] Figure 17 This is a distorted image of the second embodiment in Example 2 of the present invention;

[0076] Figure 18 This is a relative illumination diagram of the second embodiment in Example 2 of the present invention.

[0077] In the above figures, the reference numerals represent: 1, first positive lens; 2, second positive lens; 3, first negative lens; 4, aperture stop; 5, third positive lens; 6, second negative lens; 7, fourth positive lens; 8, filter. Detailed Implementation

[0078] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The illustrative embodiments and descriptions of this invention are for illustrative purposes only and are not intended to limit the invention. The embodiments described below are some, but not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0079] In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, materials, or methods are not specifically described to avoid obscuring the invention. Unless otherwise specified, the materials, instruments, and reagents used in the following embodiments are commercially available. Unless otherwise specified, the techniques used in the embodiments are conventional methods well known to those skilled in the art.

[0080] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0081] Example 1:

[0082] Please refer to the following: Figure 1As shown, this embodiment discloses a long focal length short-wave infrared imaging lens assembly, including a lens assembly. The lens assembly consists of a first positive lens 1, a second positive lens 2, a first negative lens 3, an aperture 4, a third positive lens 5, a second negative lens 6, a fourth positive lens 7, and a filter 8, arranged sequentially from the light incident direction to the light exit direction.

[0083] The first positive lens 1 is a biconvex lens, which satisfies the following:

[0084] ,in, These are the refractive index and Abbe number of the first positive lens, respectively;

[0085] The second positive lens 2 is a meniscus positive lens, which satisfies:

[0086] ,in, These are the refractive index and Abbe number of the second positive lens, respectively.

[0087] The first negative lens 3 is a meniscus negative lens, which satisfies the following:

[0088] ,in, These are the refractive index and Abbe number of the first negative lens, respectively;

[0089] The third positive lens 5 is a meniscus positive lens, which satisfies the following:

[0090] ,in, These are the refractive index and Abbe number of the third positive lens, respectively.

[0091] The second negative lens 6 is a meniscus negative lens, which satisfies the following:

[0092] ,in, These are the refractive index and Abbe number of the second negative lens, respectively.

[0093] The fourth positive lens 7 is a biconvex lens, which satisfies the following:

[0094] ,in, These are the refractive index and Abbe number of the fourth positive lens, respectively.

[0095] The coefficients of thermal expansion of the first positive lens 1, the second positive lens 2, the first negative lens 3, the third positive lens 5, the second negative lens 6, and the fourth positive lens 7 satisfy the following conditions at -40℃ to +60℃:

[0096] The coefficient of thermal expansion of the first positive lens 1 is ;

[0097] The coefficient of thermal expansion of the second positive lens 2 is ;

[0098] The coefficient of thermal expansion of the first negative lens 3 is ;

[0099] The coefficient of thermal expansion of the third positive lens 5 is: ;

[0100] The coefficient of thermal expansion of the second negative lens 6 is ;

[0101] The coefficient of thermal expansion of the fourth positive lens 7 is: .

[0102] It also includes a lens barrel located outside the lens assembly, the lens barrel being adapted to the lens assembly, and the coefficient of thermal expansion of the lens barrel satisfying the following conditions within the range of -40℃ to +60℃:

[0103] The coefficient of thermal expansion of the lens barrel is: .

[0104] The center thickness of each lens in the lens assembly satisfies:

[0105] The center thickness of the first positive lens 1 is ,in, The center thickness of the first positive lens;

[0106] The center thickness of the second positive lens 2 is ,in, The center thickness of the second positive lens;

[0107] The center thickness of the first negative lens 3 is ,in, The center thickness of the first negative lens;

[0108] The center thickness of the third positive lens 5 is ,in, The center thickness of the third positive lens;

[0109] The center thickness of the second negative lens 6 is ,in, The center thickness of the second negative lens;

[0110] The center thickness of the fourth positive lens 7 is ,in, The center thickness of the fourth positive lens.

[0111] The aperture of each lens in the lens assembly satisfies:

[0112] The aperture of the first positive lens 1 is ,in, The aperture of the first positive lens;

[0113] The aperture of the second positive lens 2 is ,in, This is the aperture of the second positive lens;

[0114] The aperture of the first negative lens 3 is ,in, The aperture of the first negative lens;

[0115] The aperture of the third positive lens 5 is ,in, The aperture of the third positive lens;

[0116] The aperture of the second negative lens 6 is ,in, This is the aperture of the second negative lens;

[0117] The aperture of the fourth positive lens 7 is ,in, The aperture of the fourth positive lens is denoted as .

[0118] The center thickness, aperture, and back focal length of the filter 8 in the lens assembly satisfy the following:

[0119] ,

[0120] ,

[0121] ;

[0122] in, These are the center thickness, aperture, and back focal length of the filter 8, respectively.

[0123] The focal length, aperture number, and total optical length of the lens assembly satisfy the following:

[0124] ;

[0125] in, These are the focal length, aperture number, and total optical length of the lens assembly, respectively.

[0126] The lens assembly has a wavelength range of 900nm-1700nm, a field of view of 0°-3.5°, a total target length of 24.6mm, and can be adapted to a 1280*1024 pixel detector with a 15um pixel size.

[0127] To facilitate a deeper understanding of the technical solutions in this embodiment, the key optical parameter symbols involved in this application and their physical meanings and mechanisms of action in this invention are first uniformly explained:

[0128] (Refractive index) represents the refractive index of an optical material for the d-line of the helium atom spectrum (wavelength 587.6 nm). In this invention, by selecting a high refractive index ( Using materials to make positive lenses can significantly increase the radius of curvature of the lens surface while providing sufficient optical power, making the optical surface smoother, thereby effectively reducing the incident angle of light at the interface and greatly reducing spherical aberration.

[0129] The Abbe number represents the dispersion coefficient of an optical material. Its value is inversely proportional to the degree of dispersion of the material. To address the difficulty in correcting chromatic aberration in the short-wave infrared broadband band, this invention employs a high-low combination strategy: using a high Abbe number (low dispersion) material to fabricate a positive lens, while simultaneously introducing a very small Abbe number (e.g., The special high-dispersion negative lens utilizes the extremely strong dispersion capability of the negative lens to generate reverse chromatic aberration, thereby accurately offsetting the axial chromatic aberration and magnification chromatic aberration accumulated by the positive lens group.

[0130] (Coefficient of thermal expansion) represents the linear coefficient of thermal expansion of a material within the range of -40℃ to +60℃. This invention achieves passive calorimetry by precisely matching the coefficients of thermal expansion of the lens and the lens barrel material, utilizing the deformation difference caused by thermal expansion and contraction to offset the refractive index temperature drift.

[0131] (Focal length) represents the effective focal length of the lens group; this scheme is set to 200mm, which aims to achieve the observation and identification of distant targets.

[0132] (Aperture number) represents the ratio of effective focal length to entrance pupil diameter. In this invention, it is set to F2.0, representing a large aperture, which aims to improve the signal-to-noise ratio in low-light environments.

[0133] (Total optical length) represents the axial distance from the incident surface of the first lens to the image plane. This invention controls it to 210mm, achieving a compact telephoto ratio.

[0134] (Optical back focal length) represents the distance from the rear surface of the final lens (or filter) to the image plane. This invention provides sufficient back focal length (BFL) to accommodate the detector's optical window and cooling structure.

[0135] Based on the above embodiments, it can be understood that this solution provides a long-focal-length short-wave infrared imaging lens assembly specifically designed for long-range detection and possessing passive, thermal-free characteristics. For example... Figure 1 As shown, the main optical path architecture of this lens assembly consists of six coaxially arranged lenses, arranged sequentially along the optical axis from the incident side to the exit side: a first positive lens, a second positive lens, a first negative lens, an aperture stop, a third positive lens, a second negative lens, a fourth positive lens, and a filter. The core design of this embodiment lies in solving the challenges of wide-spectrum achromaticity, passive calorimetry over a wide temperature range, and high-quality imaging under a large aperture by precisely combining ordinary glass materials, while completely abandoning expensive and fragile crystal materials (such as CaF2 and ZnSe).

[0136] First, addressing the technical challenges of a wide short-wave infrared (900nm-1700nm) band and difficulties in chromatic aberration correction, this embodiment does not employ traditional crystal material solutions. Instead, it creatively modifies the optical parameters (refractive index) of the six lenses. and Abbe number A specific high-low combination strategy was adopted.

[0137] Specifically, the first positive lens 1, located at the very front of the optical path, is designed as a biconvex lens, using a high-refractive-index material with a refractive index greater than 1.7 and an Abbe number between 43 and 45. The second positive lens 2 is designed as a meniscus lens, using a low-dispersion material with an Abbe number greater than 45. These two positive lenses at the front of the optical path undertake the main task of converging light rays. The choice of high refractive index makes the curvature of the lens surface more gentle, thus effectively controlling spherical aberration while providing high optical power. More importantly, the first negative lens 3 following behind is designed as a meniscus negative lens, and a special high-dispersion glass with a refractive index of over 1.9 and an Abbe number less than 20 is specially selected. This lens utilizes its extremely high dispersion characteristics (low Abbe number) to strongly compensate for axial chromatic aberration and magnification chromatic aberration generated by the preceding positive lens group.

[0138] Subsequently, the third positive lens 5, the second negative lens 6, and the fourth positive lens 7 are each made of specific high-refractive-index (refractive-index greater than 1.7) materials. Through the alternating arrangement of positive and negative optical powers, the remaining transverse chromatic aberration and higher-order aberrations are further corrected. Through this specific combination of optical parameters, this lens group can ensure that light rays of different wavelengths highly coincide on the image plane within a wide spectral range of 900nm to 1700nm, significantly eliminating secondary spectral density, thus achieving high-resolution imaging with a low-cost all-glass configuration.

[0139] Secondly, addressing the issue of focal plane drift (thermal defocusing) caused by material thermal expansion and contraction in outdoor environments ranging from -40℃ to +60℃, this embodiment employs a dual passive calorimetric strategy combining lens self-compensation and structural-assisted compensation. At the lens material level, this scheme rigorously selects and limits the coefficient of thermal expansion (CTE) of each lens within its operating temperature range. Specifically, the first positive lens 1 provides the primary positive optical power. The first negative lens 3CTE, which provides the main negative optical power, is set to [left and right]. By utilizing the difference in temperature sensitivity between the positive and negative lens groups, the positive thermal defocusing caused by temperature rise in the positive lens group is roughly canceled out by the negative thermal defocusing caused by the negative lens group.

[0140] At the mechanical structure level, in order to eliminate the residual thermal difference after lens self-compensation, this embodiment introduces a coefficient of thermal expansion as high as [insert value here]. The lens barrel (compatible with aluminum alloy materials) features a significantly higher CTE (Coefficient of Thermal Expansion) than the lens glass. When ambient temperature rises, the axial elongation of the lens barrel exceeds the thickness expansion of the lens glass, thus widening the air gap between the lenses. This change in air gap caused by thermal deformation of the mechanical structure generates a precise reverse defocus, further offsetting the optical focus shift caused by temperature drift of the glass refractive index. Through this complete optomechanical-thermal coupling design, this lens assembly maintains a stable focal length under extreme temperature conditions without relying on complex electromechanical active focusing devices, ensuring clear imaging in all weather conditions.

[0141] Furthermore, to meet the high signal-to-noise ratio requirements for long-distance detection, this embodiment constructs the lens as an ultra-large aperture system with an F2.0 aperture. To ensure sufficient light transmission through the entrance pupil, the aperture of the first positive lens 1 is designed to be an ultra-large aperture of 103mm to 104mm, which can maximize the collection of weak target reflected light. Subsequently, the apertures of each lens are gradually reduced until the fourth positive lens 7 reaches 40mm-41mm, forming an optimized light cone channel that effectively avoids the interception (vignetting) of edge light.

[0142] Meanwhile, considering the manufacturing difficulty and structural strength of large-aperture lenses, this embodiment features a targeted design in terms of structural dimensions. The center thickness of the large-sized first positive lens 1 and third positive lens 5 is set within a relatively thick range of 15mm to 16mm. This not only provides the lenses with sufficient mechanical strength to prevent surface collapse and breakage, but also facilitates the optimization of optical path to assist in correcting field curvature. On the other hand, the smaller-aperture second negative lens 6 is controlled within a relatively thin range of 4mm to 5mm to reduce the system weight.

[0143] Finally, based on the above design, this embodiment ultimately achieves excellent system performance indicators: the lens focal length reaches 200mm, coupled with a large aperture of F2.0, providing extremely strong long-distance low-light detection capabilities; at the same time, through the compact layout of the optical focal length, the total optical length ( With a focal length controlled at 210mm and a telephoto ratio close to 1:1, it successfully solves the technical pain point of telephoto lenses being typically bulky and inconvenient to integrate. At the same time, its maximum field of view (3.5 degrees) corresponds to an image field that can cover a diagonal length of 24.6mm. Furthermore, the filter aperture (28-29mm) and optical back focal length (11.8-13mm) have been optimized, leaving ample space for safe assembly. It can perfectly adapt to mainstream large-area array short-wave infrared detectors with a pixel size of 15 micrometers and a resolution of 1280×1024.

[0144] In summary, this embodiment successfully constructed a high-performance long-focal-length and short-wave infrared lens that combines low cost, wide temperature range without pyrolysis, large aperture, and high resolution adaptability by precisely combining six ordinary glass lenses under specific refractive index / dispersion matching, thermal expansion coefficient matching, and structural size control.

[0145] Example 2:

[0146] To further verify the feasibility of the long focal length short-wave infrared imaging lens group proposed in this invention in practical engineering applications, and to corroborate the rationality of the numerical ranges defined in the claims, this embodiment provides a preferred specific design scheme of this solution, namely, a first embodiment and a second embodiment, wherein the optical parameters of the two embodiments are shown in Table 1 below:

[0147] Table 1: Light parameters of the two implementation methods in Example 2

[0148]

[0149] For a detailed description of the first embodiment, further detailed optical data are shown in Table 2 below:

[0150] Table 2: Detailed Optical Data Sheet for the First Embodiment

[0151]

[0152] As shown in Table 2 above, in the first embodiment, the focal length of the shortwave infrared imaging lens group ( The aperture is 200mm, and the f / 1.00 is ( ). The target has a length of 2, a field of view of 3.5°, a total target length of 24.6 mm, and a total optical length of ( ). The diameter is 210mm.

[0153] Reference Figure 2The diagram shows the dot plot of the first embodiment at a normal temperature of 20°C. It can be seen that the RMS radius of the blur spot is less than 9μm at each field of view, indicating that the optical system aberrations have been well corrected and the imaging quality is good.

[0154] Reference Figure 3 The diagram shows the dot plot of the first embodiment at a low temperature of -40℃. It can be seen that the RMS radius of the blur spot is less than 7μm at each field of view, indicating that the optical system aberrations have been well corrected and the imaging quality is good.

[0155] Reference Figure 4 The diagram shows the first embodiment under a high temperature of 60°C. It can be seen that the RMS radius of the blur spot is less than 8μm at each field of view, indicating that the optical system aberrations have been well corrected and the imaging quality is good.

[0156] Reference Figure 5 The first embodiment is shown in the optical modulation transfer function (MTF) diagram at room temperature (20°C). It can be seen that the MTF of each field of view at 33 lp / mm is greater than 0.7, indicating that this embodiment has high resolution and clear imaging in the 900-1700nm short-wave infrared band.

[0157] Reference Figure 6 The image shows the optical modulation transfer function (MTF) of the first embodiment under a low temperature environment of -40°C. It can be seen that the MTF of each field of view at 33 lp / mm is greater than 0.5, and the imaging is clear.

[0158] Reference Figure 7 The first embodiment is shown in the optical modulation transfer function (MTF) diagram at a high temperature of 60°C. It can be seen that the MTF of each field of view at 33 lp / mm is greater than 0.5, and the imaging is clear.

[0159] Reference Figure 8 The distortion map of the first embodiment under the full field of view shows that the maximum distortion is less than 1%, the imaging deformation is small, the reproduction is high, and the imaging effect is good.

[0160] Reference Figure 9 The image shows the relative illumination of the first embodiment. It can be seen that at the center wavelength of 1300nm, the relative illumination of the entire field of view is greater than 95%, and the imaging quality is good.

[0161] For a detailed description of the second embodiment, further detailed optical data are shown in Table 3 below:

[0162] Table 3: Detailed optical data for the second embodiment:

[0163]

[0164] As shown in Table 3 above, in the second embodiment, the focal length of the shortwave infrared lens group ( The aperture is 200mm, and the f / 1.00 is ( ). The target has a length of 2, a field of view of 3.5°, a total target length of 24.6 mm, and a total optical length of ( ). The diameter is 210mm.

[0165] Reference Figure 11 The diagram shows the dot plot of the second embodiment at a normal temperature of 20°C. It can be seen that the RMS radius of the blur spot is less than 9μm at each field of view, indicating that the optical system aberrations have been well corrected and the imaging quality is good.

[0166] Reference Figure 12 The diagram shows the dot plot of the second embodiment at a low temperature of -40℃. It can be seen that the RMS radius of the blur spot is less than 7μm at each field of view, indicating that the optical system aberrations have been well corrected and the imaging quality is good.

[0167] Reference Figure 13 The diagram shows the dot plot of the second embodiment under a high temperature of 60°C. It can be seen that the RMS radius of the blur spot is less than 8μm at each field of view, indicating that the optical system aberrations have been well corrected and the imaging quality is good.

[0168] Reference Figure 14 The image shows the optical modulation transfer function (MTF) of the second embodiment at a normal temperature of 20°C. It can be seen that the MTF of each field of view at 33 lp / mm is greater than 0.7, indicating that this embodiment has high resolution and clear imaging in the 900-1700nm short-wave infrared band.

[0169] Reference Figure 15 The image shows the optical modulation transfer function (MTF) of the second embodiment under a low temperature environment of -40°C. It can be seen that the MTF of each field of view at 33 lp / mm is greater than 0.5, and the imaging is clear.

[0170] Reference Figure 16 The image shows the optical modulation transfer function (MTF) of the second embodiment under a high temperature of 60°C. It can be seen that the MTF of each field of view at 33 lp / mm is greater than 0.5, and the imaging is clear.

[0171] Reference Figure 17 The distortion map of the second embodiment under the full field of view shows that the maximum distortion is less than 1%, the imaging deformation is small, the reproduction is high, and the imaging effect is good.

[0172] Reference Figure 18 The image shows the relative illumination of the second embodiment. It can be seen that at the center wavelength of 1300nm, the relative illumination of the entire field of view is greater than 95%, and the imaging quality is good.

[0173] Therefore, through detailed numerical data and multi-dimensional performance charts (dot plot, MTF, distortion, illuminance), it is fully demonstrated that the long focal length short-wave infrared imaging lens group described in the claims of this invention can achieve excellent imaging quality under conditions of large aperture, long focal length, and a wide temperature range of -40℃ to +60℃, ensuring the technical advantages of this solution in terms of achromaticity and thermalization.

[0174] The sequence numbers of the embodiments in this application are merely for descriptive purposes. Furthermore, the structures, proportions, sizes, etc., illustrated in the accompanying drawings are all schematic diagrams, intended only to complement the content disclosed in the specification and to facilitate understanding and reading by those skilled in the art. They are not intended to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the present invention, should still fall within the scope of the technical content disclosed in this invention.

[0175] Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

Claims

1. A long focal length short-wave infrared imaging lens assembly, comprising a lens component, characterized in that, The lens assembly consists of a first positive lens, a second positive lens, a first negative lens, an aperture stop, a third positive lens, a second negative lens, a fourth positive lens, and a filter, in sequence from the light incident direction to the light exit direction. The first positive lens is a biconvex lens, which satisfies the following: ,in, These are the refractive index and Abbe number of the first positive lens, respectively; The second positive lens is a meniscus lens, which satisfies: ,in, These are the refractive index and Abbe number of the second positive lens, respectively. The first negative lens is a biconcave lens, which satisfies the following: ,in, These are the refractive index and Abbe number of the first negative lens, respectively; The third positive lens is a meniscus positive lens, which satisfies the following: ,in, These are the refractive index and Abbe number of the third positive lens, respectively. The second negative lens is a meniscus negative lens, which satisfies: ,in, These are the refractive index and Abbe number of the second negative lens, respectively. The fourth positive lens is a biconvex lens, which satisfies the following: ,in, These are the refractive index and Abbe number of the fourth positive lens, respectively.

2. The long focal length short-wave infrared imaging lens assembly according to claim 1, characterized in that, The coefficients of thermal expansion of the first positive lens, the second positive lens, the first negative lens, the third positive lens, the second negative lens, and the fourth positive lens satisfy the following conditions within the temperature range of -40℃ to +60℃: The coefficient of thermal expansion of the first positive lens is ; The coefficient of thermal expansion of the second positive lens is ; The coefficient of thermal expansion of the first negative lens is ; The coefficient of thermal expansion of the third positive lens is: ; The coefficient of thermal expansion of the second negative lens is ; The coefficient of thermal expansion of the fourth positive lens is: .

3. A long focal length short-wave infrared imaging lens assembly according to claim 2, characterized in that, It also includes a lens barrel located outside the lens assembly, the lens barrel being adapted to the lens assembly, and the coefficient of thermal expansion of the lens barrel satisfying the following conditions within the range of -40℃ to +60℃: The coefficient of thermal expansion of the lens barrel is: .

4. A long focal length short-wave infrared imaging lens assembly according to claim 3, characterized in that, The center thickness of each lens in the lens assembly satisfies: The center thickness of the first positive lens is ,in, The center thickness of the first positive lens; The center thickness of the second positive lens is ,in, The center thickness of the second positive lens; The center thickness of the first negative lens is ,in, The center thickness of the first negative lens; The center thickness of the third positive lens is ,in, The center thickness of the third positive lens; The center thickness of the second negative lens is ,in, The center thickness of the second negative lens; The center thickness of the fourth positive lens is ,in, The center thickness of the fourth positive lens.

5. A long focal length short-wave infrared imaging lens assembly according to claim 4, characterized in that, The aperture of each lens in the lens assembly satisfies: The aperture of the first positive lens is ,in, The aperture of the first positive lens; The aperture of the second positive lens is ,in, This is the aperture of the second positive lens; The aperture of the first negative lens is ,in, The aperture of the first negative lens; The aperture of the third positive lens is ,in, The aperture of the third positive lens; The aperture of the second negative lens is ,in, This is the aperture of the second negative lens; The aperture of the fourth positive lens is ,in, The aperture of the fourth positive lens is denoted as .

6. A long focal length short-wave infrared imaging lens assembly according to claim 1, characterized in that, The center thickness, aperture, and back focal length of the filter in the lens assembly satisfy the following: ， ， ； in, These are the center thickness, aperture, and back focal length of the filter, respectively.

7. A long focal length short-wave infrared imaging lens assembly according to claim 1, characterized in that, The focal length, aperture number, and total optical length of the lens assembly satisfy the following: ； in, These are the focal length, aperture number, and total optical length of the lens assembly, respectively.

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