A laser and long-wave infrared dual-band common-aperture optical system

Abstract

The application discloses a dual-waveband common-aperture optical system, and particularly discloses a laser and long-wave infrared dual-waveband common-aperture optical system, which solves the problem that an existing composite detection system is difficult to simultaneously meet high sensitivity and light weight, small size. The system comprises a common-aperture objective assembly, a long-wave infrared imaging optical assembly and a laser ranging receiving optical assembly; the common-aperture objective assembly comprises a primary mirror and a secondary mirror; long-wave infrared light and laser from a target are reflected by the primary mirror and then enter the secondary mirror, and after color separation of the secondary mirror, the long-wave infrared light is reflected and the laser is transmitted; the long-wave infrared imaging optical assembly is arranged on a reflection light path of the secondary mirror, and comprises three reflecting mirrors, four reflecting mirrors, a Dewar window and a cold filter; the long-wave infrared light reflected by the secondary mirror forms an intermediate real image and then enters the three reflecting mirrors, and after sequentially passing through the three reflecting mirrors, the four reflecting mirrors, the Dewar window and the cold filter, the long-wave infrared light is converged to a long-wave infrared image surface; the laser ranging receiving optical assembly is arranged on a transmission light path of the secondary mirror.

Description

Technical Field

[0001] This invention relates to a dual-band common aperture optical system, specifically a dual-band common aperture optical system for laser and long-wave infrared. Background Technology

[0002] In modern optical imaging technology, visible light imaging relies on the reflection of ambient light (mainly sunlight) by objects, and its imaging quality is significantly affected by ambient light. In contrast, infrared imaging is based on the infrared light emitted by the object itself, so it can still effectively image at night or under adverse conditions such as smoke and fog, breaking through the dependence of imaging technology on lighting conditions and greatly expanding its application range in time and space.

[0003] Laser ranging technology, with its excellent anti-interference capabilities and high precision, enables rapid and accurate distance measurement of distant targets. Therefore, combining infrared imaging with laser ranging technology results in a composite detection system that can not only acquire the target's shape features and outline, but also track its movement trajectory, capturing the target's distance, orientation, and dynamic changes from all angles, providing comprehensive and reliable data for subsequent decision-making and actions.

[0004] However, achieving high-sensitivity detection in infrared imaging optical systems within composite detection systems faces significant challenges. The primary limiting factor is background thermal radiation, particularly the thermal radiation from the optomechanical system itself. In the long-wave infrared band, the radiation generated by the heat generated by optical elements, lens barrels, and other structures often reaches the detector at intensities several orders of magnitude higher than the signal strength of distant, weak targets, becoming a significant noise source. In the extremely low temperatures of deep space exploration, the space background thermal radiation is extremely weak, making the thermal radiation from the optomechanical system itself the primary background noise encountered by the detector. This significantly reduces the target signal-to-noise ratio and image contrast, leading to reduced image detail, compressed dynamic range, and uneven grayscale. In severe cases, the target signal may be completely overwhelmed, or false alarms may occur, causing detection failure.

[0005] To address these issues, existing composite detection systems typically employ a multi-aperture design with multiple independent optical systems, which significantly increases the system's weight, size, and complexity, making it difficult to integrate or apply to systems with strict weight and size requirements. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problem that existing composite detection systems cannot simultaneously meet the requirements of high sensitivity, lightweight and miniaturization, and to provide a dual-band co-aperture optical system for laser and long-wave infrared.

[0007] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0008] A dual-band co-aperture optical system for laser and long-wave infrared wavelengths is characterized by:

[0009] This includes a common aperture objective lens assembly, a long-wave infrared imaging optical assembly, and a laser ranging and receiving optical assembly.

[0010] The common aperture objective lens assembly includes a primary mirror and a secondary mirror arranged coaxially.

[0011] The primary mirror is a ring-shaped reflector with positive optical power; the secondary mirror is a lens with positive optical power, and the surface of the mirror closest to the primary mirror is coated with a dichroic film, and when this surface is used as a reflective surface, the optical power of this surface is negative.

[0012] Long-wave infrared light radiated from the target itself and reflected laser light are incident on the primary mirror. After being reflected by the primary mirror, they are incident on the secondary mirror. After being separated by color by the secondary mirror, the long-wave infrared light is reflected and the laser light is transmitted.

[0013] The long-wave infrared imaging optical component is disposed in the reflected light path of the secondary mirror to realize long-wave infrared imaging. It includes a three-mirror, a four-mirror, a Dewar window, and a cold filter.

[0014] The three reflecting mirrors are coaxial with the primary mirror and are disposed on the side of the primary mirror away from the secondary mirror; the four reflecting mirrors are coaxially disposed between the primary mirror and the three reflecting mirrors; both the three reflecting mirrors and the four reflecting mirrors are annular reflecting mirrors with positive optical power; the Dewar window and the cold filter are coaxially disposed in the central through-hole of the three reflecting mirrors;

[0015] After the long-wave infrared light reflected by the secondary mirror forms an intermediate real image, it diverges and is incident on the third reflecting mirror, reflected by the third reflecting mirror to the fourth reflecting mirror, and then reflected by the fourth reflecting mirror to the Dewar window. After passing through the Dewar window and the cold filter in sequence, it converges onto the long-wave infrared image plane for docking with the cooled long-wave infrared detector for imaging. Both the Dewar window and the cold filter are matched with the cooled long-wave infrared detector.

[0016] The laser ranging receiving optical component is disposed in the transmission optical path of the secondary mirror and is used to receive laser echoes to realize laser ranging imaging.

[0017] Furthermore, the wavelength of the long-wave infrared light is 7.7μm to 10.5μm;

[0018] The long-wave infrared imaging optical system formed by the common aperture objective lens assembly and the long-wave infrared imaging optical assembly has a focal length of 100mm to 200mm and an F number of 1 to 3.

[0019] Furthermore, in order to make the long-wave infrared imaging optical system have higher transmittance and a more compact structure, the axial spacing between the primary mirror and the secondary mirror is -50mm to -20mm.

[0020] The reflective surface of the primary mirror and the surface of the secondary mirror near the primary mirror are both hyperboloids.

[0021] The radius of curvature of the vertex of the reflecting surface of the primary mirror is -120mm to -90mm; the radius of curvature of the vertex of the secondary mirror on the side closer to the primary mirror is -100mm to -30mm.

[0022] The axial spacings between the secondary mirror and the third mirror, the third mirror and the fourth mirror, the fourth mirror and the Dewar window, the Dewar window and the cold filter, and the cold filter and the long-wave infrared image plane are 80mm~150mm, -80mm~-50mm, 50mm~80mm, 2mm~4mm, and 17mm~23mm, respectively.

[0023] The reflecting surfaces of both the three-reflecting mirror and the four-reflecting mirror are even-order aspherical surfaces.

[0024] The radii of curvature at the vertex of the reflecting surfaces of the three-reflecting mirror and the four-reflecting mirror are 2800mm~4000mm and 50mm~150mm, respectively.

[0025] Furthermore, it also includes the supporting structure;

[0026] Each optical element in the common aperture objective lens assembly, the long-wave infrared imaging optical assembly, and the laser ranging and receiving optical assembly is installed and connected through the support structure.

[0027] The primary mirror, three reflecting mirrors, and four reflecting mirrors are all made of the same material as the supporting structure. This design avoids thermal defocusing and optical axis drift caused by inconsistent material expansion coefficients, thus ensuring the high performance and high reliability of the optical system in complex and wide-temperature environments.

[0028] Furthermore, in order to suppress stray light noise, the long-wave infrared imaging optical component also includes a first field-of-view aperture;

[0029] The first field stop is located at the intermediate real image position and is coaxial with the secondary mirror; the long-wave infrared light reflected by the secondary mirror forms an intermediate real image at the first field stop position, then passes through the first field stop and diverges into the three reflecting mirrors.

[0030] The first field stop is made of the same material as the supporting structure;

[0031] The inner surfaces of the central through-holes of the primary mirror, the three reflecting mirrors, and the four reflecting mirrors are all coated with matte paint with an absorption rate of ≥99%.

[0032] Furthermore, in order to make the optical system more reliable in low-temperature and variable-temperature environments and lighter in weight, the primary mirror, the first field stop, the three reflecting mirrors, the four reflecting mirrors, and the supporting structure are all made of aluminum alloy.

[0033] The secondary mirror is made of optical glass HZLAF96, optical glass HK9L, or quartz.

[0034] The four reflecting mirrors are located on the back of the main mirror, and the main mirror and the four reflecting mirrors are an integral structure.

[0035] Furthermore, the wavelength of the laser is 0.8μm to 2μm;

[0036] The focal length of the laser ranging and receiving optical system formed by the common aperture objective lens assembly and the laser ranging and receiving optical assembly is 100mm to 300mm, and the F number is 1 to 3.

[0037] Furthermore, to simplify the optical system structure and reduce its size, the laser ranging receiving optical component includes, sequentially arranged along the optical path, a first meniscus negative lens bent towards the image side, a second meniscus negative lens bent towards the image side, a first plane mirror, a second plane mirror, a first meniscus positive lens bent towards the image side, a third meniscus negative lens bent towards the image side, a first biconcave negative lens, a first biconvex positive lens, and a second meniscus positive lens bent towards the image side; the image side corresponding to each lens refers to the side of the outgoing light ray corresponding to each lens in the optical path.

[0038] The optical axes of both the first meniscus negative lens and the second meniscus negative lens are coaxial with the optical axis of the secondary lens;

[0039] The laser transmitted through the secondary mirror is diverged sequentially by the first meniscus negative lens and the second meniscus negative lens and then emitted in parallel, and enters the first plane mirror.

[0040] The reflecting surface of the second planar reflector is opposite to and perpendicular to the reflecting surface of the first planar reflector, for folding the optical path by 180°;

[0041] The first meniscus positive lens, the third meniscus negative lens, the first biconcave negative lens, the first biconvex positive lens, and the second meniscus positive lens are sequentially and coaxially arranged in the output light path of the second plane reflector. After the output laser beam is diverged by the third meniscus negative lens and formed into an image, it is then diverged and incident on the first biconcave negative lens. After passing through the first biconcave negative lens, the first biconvex positive lens, and the second meniscus positive lens in sequence, the beam converges onto the laser ranging receiving image plane.

[0042] Furthermore, in order to suppress stray light noise, the laser ranging receiving optical component also includes a second field of view aperture;

[0043] The second field stop is positioned at the primary imaging position and is coaxial with the third meniscus negative lens.

[0044] Furthermore, the center thickness of the secondary mirror is -8mm to -2mm;

[0045] The center thickness of the first meniscus negative lens, the second meniscus negative lens, the first meniscus positive lens, the third meniscus negative lens, the first biconcave negative lens, the first biconvex positive lens, and the second meniscus positive lens is between -5mm and -2mm.

[0046] The axial intervals between the secondary mirror and the first meniscus negative lens, the first meniscus negative lens and the second meniscus negative lens, the first meniscus positive lens and the third meniscus negative lens, the third meniscus negative lens and the first biconcave negative lens, the first biconcave negative lens and the first biconvex positive lens, the first biconvex positive lens and the second meniscus positive lens, the second meniscus positive lens and the laser ranging receiving image plane are -2mm to -0.5mm, -5mm to -1mm, -2mm to -0.2mm, -80mm to -40mm, -3mm to -0.5mm, -8mm to -2mm, and -25mm to -10mm, respectively.

[0047] The first meniscus negative lens has an object-side vertex curvature radius of -50mm to -5mm and an image-side vertex curvature radius of -30mm to -2mm; the second meniscus negative lens has an object-side vertex curvature radius of -100mm to -5mm and an image-side vertex curvature radius of -50mm to -2mm; the first meniscus positive lens has an object-side vertex curvature radius of -50mm to -5mm and an image-side vertex curvature radius of -100mm to -20mm; the third meniscus negative lens has an object-side vertex curvature radius of -2mm. The object-side surface vertex curvature radius of the first biconcave negative lens is 5mm to 20mm, and the image-side surface vertex curvature radius is -50mm to -5mm; the object-side surface vertex curvature radius of the first biconvex positive lens is -100mm to -50mm, and the image-side surface vertex curvature radius is 5mm to 50mm; the object-side surface vertex curvature radius of the second meniscus positive lens is -20mm to -5mm, and the image-side surface vertex curvature radius is -30mm to -8mm.

[0048] The first meniscus negative lens is made of optical glass HZLAF96 or HZLAF92; the second meniscus negative lens is made of optical glass HZLAF96 or HZLAF92; the first plane mirror is made of optical glass HK9L, quartz, or microcrystalline; the second plane mirror is made of optical glass HK9L, quartz, or microcrystalline; the first meniscus positive lens is made of optical glass HQK1 or HQK3L; the third meniscus negative lens is made of optical glass HQK1 or HQK3L; the first biconcave negative lens is made of optical glass HK11 or HK10; the first biconvex positive lens is made of optical glass HZLAF92 or HZLAF96; and the second meniscus positive lens is made of optical glass HZF3 or HZF6.

[0049] Compared with the prior art, the present invention has the following beneficial technical effects:

[0050] 1. The laser and long-wave infrared dual-band co-aperture optical system of the present invention comprises a primary mirror, a secondary mirror, a third mirror, and a fourth mirror, all coaxially arranged to form a coaxial four-reflection structure. During beam splitting, a dichroic film is deposited on the surface of the secondary mirror closest to the primary mirror to achieve beam splitting. After beam splitting, the long-wave infrared light reflected by the secondary mirror forms an intermediate real image and then diverges and is incident on the third mirror. Furthermore, a Dewar window and a cold filter are sequentially located after the fourth mirror and coaxially arranged in the central aperture of the third mirror, and both are matched with the cooled long-wave infrared detector that is connected to them for imaging. Through the combined effect of these arrangements, the long-wave infrared imaging optical system of the present invention achieves 100% cold aperture efficiency, effectively suppresses the influence of stray radiation and background thermal radiation from the optomechanical system itself on the performance of the optical system, and achieves high transmittance and high sensitivity in the long-wave infrared imaging optical system.

[0051] On the other hand, the common-aperture objective lens assembly shared by the long-wave infrared imaging optical component and the laser ranging and receiving optical component in this invention has a simpler optical path and reduces size and weight compared to the aperture-splitting design of multiple independent optical systems used in existing composite detection systems. Furthermore, in this invention, dichroism is achieved by coating a dichroic film on the surface of the secondary mirror near the primary mirror. Compared to dichroism using a beam splitter prism, this method results in a simpler structure, higher integration, reduced volume, and lighter weight for the beam splitting element. In addition, this invention coaxially arranges the primary mirror, secondary mirror, three-mirror, and four-mirror to form a coaxial four-reflection structure, which not only effectively suppresses the influence of background thermal radiation on the performance of the optical system but also makes the structure of the optical system more compact and smaller. Therefore, this invention achieves miniaturization and weight reduction.

[0052] In summary, this invention solves the technical problem that existing composite detection systems cannot simultaneously meet the requirements of high sensitivity, lightweight design, and miniaturization.

[0053] 2. In the laser and long-wave infrared dual-band co-aperture optical system of the present invention, the surface shapes of the primary mirror's reflecting surface, the secondary mirror's surface near the primary mirror, the third mirror's reflecting surface, and the fourth mirror's reflecting surface are preferably designed with aspherical surfaces and the curvature radius of each surface vertex is reasonably allocated. This makes the long-wave infrared imaging optical system structure more compact, avoids secondary obstruction, ensures high system transmittance, and further improves its sensitivity.

[0054] 3. In the laser and long-wave infrared dual-band co-aperture optical system of the present invention, the primary mirror, the first field stop, the three reflecting mirrors, the four reflecting mirrors, and the support structure are preferably all made of the same aluminum alloy material. By using aluminum alloy material, the wide temperature adaptability of the optical system in the space environment is improved. The fact that the reflecting mirrors and the support structure for their installation and connection are made of the same aluminum alloy material can avoid thermal defocusing and optical axis drift of the optical system caused by inconsistent material expansion coefficients, thereby ensuring the high performance and high reliability of the optical system in complex wide temperature environments.

[0055] 4. In the laser and long-wave infrared dual-band co-aperture optical system of the present invention, the laser ranging and receiving optical component preferably includes a first plane mirror and a second plane mirror, and the reflecting surface of the second plane mirror is opposite to and perpendicular to the reflecting surface of the first plane mirror. This allows the optical path of the laser ranging and receiving optical component to be folded 180°, which greatly reduces the volume of the optical system and enables the optical system to be miniaturized.

[0056] 5. In the laser and long-wave infrared dual-band co-aperture optical system of the present invention, the imaging quality of both the long-wave infrared imaging optical system and the laser ranging and receiving optical system is close to the diffraction limit, and the imaging performance is excellent. Therefore, the laser and long-wave infrared dual-band co-aperture optical system of the present invention can meet the high-precision detection requirements of distant targets. In addition, due to its light weight and small size, it can also be integrated into or applied to systems with strict requirements on weight and size. Attached Figure Description

[0057] Figure 1 This is an optical path diagram of an embodiment of the laser and long-wave infrared dual-band co-aperture optical system of the present invention.

[0058] Figure 2 This is a dot plot of the full field of view of the long-wave infrared imaging optical system in an embodiment of the laser and long-wave infrared dual-band co-aperture optical system of the present invention.

[0059] Figure 3 This is a distortion diagram of the long-wave infrared imaging optical system in an embodiment of the laser and long-wave infrared dual-band co-aperture optical system of the present invention.

[0060] Figure 4 This is an example of the energy map of the enclosed circle of the long-wave infrared imaging optical system in an embodiment of the laser and long-wave infrared dual-band co-aperture optical system of the present invention.

[0061] Figure 5 This is a full field-of-view point diagram of the laser ranging and receiving optical system in an embodiment of the laser and long-wave infrared dual-band co-aperture optical system of the present invention.

[0062] Figure 6 This is an example of the energy diagram of the enclosed circle of the laser ranging and receiving optical system in an embodiment of the dual-band laser and long-wave infrared co-aperture optical system of the present invention.

[0063] Figure 7 This is a modulation transfer function diagram of the laser ranging and receiving optical system in an embodiment of the dual-band co-aperture optical system for laser and long-wave infrared of the present invention.

[0064] The annotations in the attached figures are explained as follows:

[0065] 1-Primary mirror, 2-Secondary mirror, 31-Three-reflector mirror, 32-Four-reflector mirror, 33-Dewar window, 34-Cold filter, 35-Long-wave infrared image plane, 36-First field stop, 41-First meniscus negative lens, 42-Second meniscus negative lens, 43-First plane mirror, 44-Second plane mirror, 45-First meniscus positive lens, 46-Third meniscus negative lens, 47-First biconcave negative lens, 48-First biconvex positive lens, 49-Second meniscus positive lens, 410-Laser rangefinder receiving image plane, 411-Second field stop. Detailed Implementation

[0066] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0067] like Figure 1 As shown, the present invention provides a laser and long-wave infrared dual-band co-aperture optical system, comprising a co-aperture objective lens assembly, a long-wave infrared imaging optical assembly, and a laser ranging and receiving optical assembly.

[0068] The aforementioned common-aperture objective lens assembly includes a primary mirror 1 and a secondary mirror 2 arranged coaxially. The primary mirror 1 is a positive optical power annular reflector; the secondary mirror 2 is a positive optical power lens, and the surface of its mirror closest to the primary mirror 1 is coated with a dichroic film, and when this surface is used as a reflective surface, its optical power is negative. To better achieve dichroism separation between laser and long-wave infrared light, in this embodiment, the material of the secondary mirror 2 is preferably optical glass HZLAF96. In addition to optical glass HZLAF96, optical glass HK9L or quartz and other optical materials can also be used. Glass material; long-wave infrared light radiated from the target itself and reflected laser light are incident on the primary mirror 1, reflected by the primary mirror 1 and then incident on the secondary mirror 2. After color separation by the secondary mirror 2, the long-wave infrared light is reflected and the laser light is transmitted; in this invention, the wavelength of the long-wave infrared light is 7.7μm to 10.5μm, and the wavelength of the laser light is 0.8μm to 2μm. That is, the working wavelength of the laser and long-wave infrared dual-band co-aperture optical system of this invention is the long-wave infrared band of 7.7μm to 10.5μm and the laser band of 0.8μm to 2μm.

[0069] The aforementioned long-wave infrared imaging optical components are disposed on the reflected light path of the secondary mirror 2 to achieve long-wave infrared imaging. These components include a three-reflector mirror 31, a four-reflector mirror 32, a Dewar window 33, and a cold filter 34. The three-reflector mirror 31 is coaxial with the primary mirror 1 and is disposed on the side of the primary mirror 1 facing away from the secondary mirror 2. The four-reflector mirror 32 is coaxially disposed between the primary mirror 1 and the three-reflector mirror 31. Both the three-reflector mirror 31 and the four-reflector mirror 32 are annular mirrors with positive optical power. The primary mirror 1 and the four-reflector mirror 32 can be a separate structure as shown in this embodiment, or they can be an integrated structure. The Dewar window 33 and the cold filter 34 are coaxially disposed in the central through-hole of the three-reflector mirror 31. After the long-wave infrared light reflected by the secondary mirror 2 forms an intermediate real image, it diverges and is incident on the three-reflector mirror 31, reflected by the three-reflector mirror 31 to the four-reflector mirror 32, and then reflected by the four-reflector mirror 32 to... The Dewar window 33, after passing through the cold filter 34 in sequence, converges to the long-wave infrared image plane 35 for imaging with the cooled long-wave infrared detector. Both the Dewar window 33 and the cold filter 34 are matched with the cooled long-wave infrared detector. In this embodiment, the operating wavelength of the cooled long-wave infrared detector is 7.7μm to 10.5μm, the pixel size is 30μm, and the number of pixels is 256×256. The Dewar window 33 is a cooled long-wave infrared detector Dewar window, and the cold filter 34 is a cooled long-wave infrared detector cold filter. Both are made of germanium material that matches the material of the cooled long-wave infrared detector. In this invention, the focal length of the long-wave infrared imaging optical system formed by the common aperture objective lens assembly and the long-wave infrared imaging optical assembly is 100mm to 200mm, and the F number is 1 to 3.

[0070] To achieve higher transmittance and a more compact structure in the long-wave infrared imaging optical system formed by the aforementioned common-aperture objective lens assembly and long-wave infrared imaging optical assembly, the axial spacing between the primary mirror 1 and the secondary mirror 2 is preferably -50mm to -20mm; the surface shape of both the reflecting surface of the primary mirror 1 and the mirror surface of the secondary mirror 2 near the primary mirror 1 is preferably a hyperboloid; the radius of curvature at the vertex of the reflecting surface of the primary mirror 1 is preferably -120mm to -90mm; the secondary mirror 2 near the primary mirror 1... The radius of curvature at the vertex of the mirror is preferably -100mm to -30mm; the axial spacing between the secondary mirror 2 and the three-reflecting mirror 31, the three-reflecting mirror 31 and the four-reflecting mirror 32, the four-reflecting mirror 32 and the Dewar window 33, the Dewar window 33 and the cold filter 34, and the cold filter 34 and the long-wave infrared image plane 35 are preferably 80mm to 150mm, -80mm to -50mm, 50mm to 80mm, 2mm to 4mm, and 17mm to 23mm, respectively. m; the reflective surfaces of the three-reflecting mirror 31 and the four-reflecting mirror 32 are preferably even-order aspherical surfaces; the vertex radii of curvature of the reflective surfaces of the three-reflecting mirror 31 and the four-reflecting mirror 32 are preferably 2800mm~4000mm and 50mm~150mm, respectively; in this embodiment, the reflective surfaces of the primary mirror 1, the three-reflecting mirror 31, the four-reflecting mirror 32, and the surface of the secondary mirror 2 near the primary mirror 1, the vertex radius of curvature, the aspherical coefficient, the axial spacing between the four optical elements and the next optical element along the optical path (the optical system corresponding to Table 1 does not yet include the first field stop 36 described below, that is, the axial spacing between the secondary mirror 2 and the next optical element along the optical path, which is the axial spacing between the secondary mirror 2 and the three-reflecting mirror 31), and the materials of the four optical elements are shown in Table 1; in this embodiment, the focal length of the long-wave infrared imaging optical system formed by the above-mentioned common aperture objective lens assembly and the long-wave infrared imaging optical assembly is 146mm, and the F number is 2.

[0071] Table 1: Specific parameters of primary mirror 1, secondary mirror 2, three-mirror 31 and four-mirror 32 in this embodiment

[0072]

[0073] Note: The sign of the value in the "vertex curvature radius" column in Table 1 is related to the sign of the paraxial curvature radius of the corresponding surface of the optical element and the number of times the light is reflected (N) when the light propagates from the entrance of the optical system to the optical element (including the optical element); when N is odd, the sign of its value is opposite to the sign of the paraxial curvature radius of the corresponding surface of the optical element; when N is even, the sign of its value is the same as the sign of the paraxial curvature radius of the corresponding surface of the optical element; when the corresponding surface of the optical element is a sphere, its paraxial curvature radius is equal to the curvature radius of the vertex of the surface; when the corresponding surface of the optical element is an aspherical surface, its paraxial curvature radius is calculated using formula [1]; the above-mentioned curvature radius of the vertex of the corresponding surface of the optical element refers to the light passing through the optical element in the direction of light propagation along the optical element in this invention and assuming that there is only the optical element in the light path. When determining the optical element, the radius of curvature of the vertex of the corresponding optical element is determined; in the column "Axial distance between the optical element and the next optical element along the optical path", the absolute value of the value represents the distance on the optical axis between the surface of the optical element on the side of the light emitting the light and the surface of the next optical element along the optical path on the side of the light incident the light; the sign of the value is related to the number of times N the light is reflected when the light propagates from the entrance of the optical system to the optical element (including the optical element); when N is odd, it is negative; when N is even, it is positive; the value in the column "Axial distance between the optical element and the next optical element along the optical path" corresponding to the four reflecting mirrors 32 represents the axial distance between the four reflecting mirrors 32 and the Dewar window 33; the expressions for the hyperboloid and the even-order aspherical surface of order 6 in the "Surface Shape" column of Table 1 are Equation [2];

[0074] [1];

[0075] In formula [1]: The paraxial radius of curvature; The radius of curvature of the vertex itself; The aspheric coefficients of the quadratic term;

[0076] [2];

[0077] In formula [2]: For an aspherical surface along the optical axis at a height of The sag of the point; For height; Let be the curvature of the vertex, and be the reciprocal of the radius of curvature of the vertex itself; The conic coefficient; The aspheric coefficients of the quadratic term; The aspherical coefficients of the quartic term; is the aspherical coefficient of the sixth-order term.

[0078] To suppress stray light noise, such as Figure 1As shown, the long-wave infrared imaging optical component in this embodiment preferably further includes a first field-of-view aperture 36; the first field-of-view aperture 36 is located at the intermediate real image position and is coaxial with the secondary mirror 2; after the long-wave infrared light reflected by the secondary mirror 2 forms an intermediate real image at the first field-of-view aperture 36, it passes through the first field-of-view aperture 36 and diverges into the three-reflector mirror 31; in order to suppress stray light, in this embodiment, it is preferable to spray a matte paint with an absorptivity of 99% onto the inner surface of the central through-hole of the primary mirror 1, the three-reflector mirror 31 and the four-reflector mirror 32; in addition to spraying a matte paint with an absorptivity of 99% as shown in this embodiment, a matte paint with an absorptivity greater than 99% can also be sprayed.

[0079] like Figure 1 As shown, the laser ranging receiving optical component is disposed in the transmission optical path of the secondary mirror 2 to receive laser echoes and realize laser ranging imaging. The center thickness of the secondary mirror 2 is preferably -8mm to -2mm, and in this embodiment, it is -5mm. The focal length of the laser ranging receiving optical system formed by the common aperture objective lens assembly and the laser ranging receiving optical component in this invention is 100mm to 300mm, and the F-number is 1 to 3.

[0080] To simplify the optical system structure and reduce its size, the laser ranging and receiving optical component in this embodiment preferably includes, sequentially arranged along the optical path, a first meniscus negative lens 41 bent towards the image side, a second meniscus negative lens 42 bent towards the image side, a first plane mirror 43, a second plane mirror 44, a first meniscus positive lens 45 bent towards the image side, a third meniscus negative lens 46 bent towards the image side, a first biconcave negative lens 47, a first biconvex positive lens 48, and a second meniscus positive lens 49 bent towards the image side; the image side of each lens refers to the side of the outgoing light ray corresponding to each lens in the optical path; the optical axes of the first meniscus negative lens 41 and the second meniscus negative lens 42 are both coaxial with the optical axis of the secondary mirror 2; the laser transmitted by the secondary mirror 2 is diverged sequentially by the first meniscus negative lens 41 and the second meniscus negative lens 42 and then emitted in parallel. The light is incident on the first plane mirror 43; in this embodiment, preferably, the angle between the reflecting surface of the first plane mirror 43 and the optical axis of the second meniscus negative lens 42 is 45°; the reflecting surface of the second plane mirror 44 is opposite to and perpendicular to the reflecting surface of the first plane mirror 43, for 180° folding of the optical path; the first meniscus positive lens 45, the third meniscus negative lens 46, the first biconcave negative lens 47, the first biconvex positive lens 48, and the second meniscus positive lens 49 are sequentially and coaxially arranged on the output optical path of the second plane mirror 44, and after the output laser diverges through the third meniscus negative lens 46 to form a single image, it is then diverged and incident on the first biconcave negative lens 47, and after passing through the first biconcave negative lens 47, the first biconvex positive lens 48, and the second meniscus positive lens 49 in sequence, it converges to the laser ranging receiving image plane 410. In order to suppress stray light noise, such as Figure 1 As shown, the laser ranging receiving optical component in this embodiment preferably further includes a second field stop 411; the second field stop 411 is disposed at the primary imaging position and is coaxial with the third meniscus negative lens 46.

[0081] In practical operation, the laser and long-wave infrared dual-band co-aperture optical system of this invention configures each optical element in the laser ranging and receiving optical assembly with reference to the following parameters to achieve better results:

[0082] The center thickness of the first meniscus negative lens 41, the second meniscus negative lens 42, the first meniscus positive lens 45, the third meniscus negative lens 46, the first biconcave negative lens 47, the first biconvex positive lens 48, and the second meniscus positive lens 49 is preferably between -5mm and -2mm; the center thickness of each optical element in the laser ranging receiving optical assembly in this embodiment is shown in Table 2.

[0083] The axial spacing between the aforementioned secondary mirror 2 and the first meniscus negative lens 41, the first meniscus negative lens 41 and the second meniscus negative lens 42, the second meniscus negative lens 42 and the first plane mirror 43, the first plane mirror 43 and the second plane mirror 44, the second plane mirror 44 and the first meniscus positive lens 45, the first meniscus positive lens 45 and the third meniscus negative lens 46, the third meniscus negative lens 46 and the first biconcave negative lens 47, the first biconcave negative lens 47 and the first biconvex positive lens 48, the first biconvex positive lens 48 and the second meniscus positive lens 49, and the second meniscus positive lens 49 and the laser ranging receiving image plane 410 are preferably -2mm to -0.5mm, -5mm to -1mm, and -20mm, respectively. ~-5mm, 50mm~80mm, -30mm~-5mm, -2mm~-0.2mm, -80mm~-40mm, -3mm~-0.5mm, -8mm~-2mm, -25mm~-10mm; In this embodiment, the axial distance between the secondary mirror 2 and the first meniscus negative lens 41 is -1mm. The axial distances between each optical element in the laser ranging receiving optical assembly and the next optical element along the optical path are shown in Table 2 (the optical system corresponding to Table 2 does not yet include the above-mentioned second field stop 411, that is, the axial distance between the third meniscus negative lens 46 and the next optical element along the optical path is the axial distance between the third meniscus negative lens 46 and the first biconcave negative lens 47).

[0084] The object-side vertex radius of curvature of the first meniscus negative lens 41 is preferably -50mm to -5mm, and the image-side vertex radius of curvature is preferably -30mm to -2mm; the object-side vertex radius of curvature of the second meniscus negative lens 42 is preferably -100mm to -5mm, and the image-side vertex radius of curvature is preferably -50mm to -2mm; the object-side vertex radius of curvature of the first meniscus positive lens 45 is preferably -50mm to -5mm, and the image-side vertex radius of curvature is preferably -100mm to -20mm; the object-side vertex radius of curvature of the third meniscus negative lens 46 is preferably -20mm to -3mm, and the image-side vertex radius of curvature is preferably... -10mm to -2mm; the object-side vertex curvature radius of the first biconcave negative lens 47 is preferably 5mm to 20mm, and the image-side vertex curvature radius is preferably -50mm to -5mm; the object-side vertex curvature radius of the first biconvex positive lens 48 is preferably -100mm to -50mm, and the image-side vertex curvature radius is preferably 5mm to 50mm; the object-side vertex curvature radius of the second meniscus positive lens 49 is preferably -20mm to -5mm, and the image-side vertex curvature radius is preferably -30mm to -8mm; the object-side vertex curvature radius and image-side vertex curvature radius of each optical element in the laser ranging receiving optical assembly in this embodiment are shown in Table 2.

[0085] The material of the first meniscus negative lens 41 is preferably optical glass HZLAF96 or HZLAF92; the material of the second meniscus negative lens 42 is preferably optical glass HZLAF96 or HZLAF92; the material of the first plane mirror 43 is preferably optical glass HK9L, quartz, or microcrystalline; the material of the second plane mirror 44 is preferably optical glass HK9L, quartz, or microcrystalline; the material of the first meniscus positive lens 45 is preferably optical glass HQK1 or HQK3L; the material of the third meniscus negative lens 46 is preferably optical glass HQK1 or HQK3L; the material of the first biconcave negative lens 47 is preferably optical glass HK11 or HK10; the material of the first biconvex positive lens 48 is preferably optical glass HZLAF92 or HZLAF96; the material of the second meniscus positive lens 49 is preferably optical glass HZF3 or HZF6; the materials of each optical element in the laser ranging receiving optical assembly in this embodiment are shown in Table 2.

[0086] In this embodiment, the focal length of the laser ranging and receiving optical system formed by the above-mentioned common aperture objective lens assembly and the laser ranging and receiving optical assembly is 180mm, and the F number is 1.92.

[0087] Table 2: Specific parameters of each optical element in the laser ranging and receiving optical assembly in this embodiment.

[0088]

[0089] Note: The meanings of the positive and negative values ​​in the "Object-side surface vertex curvature radius" and "Image-side surface vertex curvature radius" columns in Table 2 are the same as those in the "Vertex curvature radius" column in Table 1 above; the positive and negative values ​​in the "Center thickness" column are related to the number of times N the light is reflected when it propagates from the entrance of the optical system to the optical element (including the optical element); when N is odd, it is negative; when N is even, it is positive; the " / " in the "Center thickness" columns corresponding to the first plane mirror 43 and the second plane mirror 44 respectively indicates that there are no requirements for the absolute value of their center thickness from an optical perspective, and it can be determined according to the structure; "and the next optical element along the light path" The meaning of the positive and negative values ​​in the "Axial Spacing" column is the same as that in Table 1 above. Although specific values ​​are given in the "Axial Spacing with the Next Optical Element Along the Optical Path" columns corresponding to the second meniscus negative lens 42, the first plane mirror 43, and the second plane mirror 44, these values ​​only reflect the specific values ​​in the structure of this embodiment. From an optical point of view, there is no requirement for the absolute value of these values; they can be determined according to the structure. The value in the "Axial Spacing with the Next Optical Element Along the Optical Path" column corresponding to the second meniscus positive lens 49 represents the axial spacing between the second meniscus positive lens 49 and the laser ranging receiving image plane 410.

[0090] This embodiment of the laser and long-wave infrared dual-band co-aperture optical system preferably also includes a support structure ( Figure 1 (The supporting structure is not shown in the diagram). The optical elements in the above-mentioned common aperture objective lens assembly, long-wave infrared imaging optical assembly, and laser ranging receiving optical assembly are installed and connected through the above-mentioned supporting structure. In order to reduce the influence of the mismatch of the expansion coefficients and avoid thermal defocusing and optical axis drift of the optical system caused by the inconsistency of the material expansion coefficients, thereby ensuring the high performance and high reliability of the optical system in complex wide temperature environments, the above-mentioned primary mirror 1, first field stop 36, three reflecting mirrors 31, and four reflecting mirrors 32 are preferably made of the same material as the above-mentioned supporting structure. In this embodiment, the materials of the above-mentioned primary mirror 1, first field stop 36, three reflecting mirrors 31, four reflecting mirrors 32, and the above-mentioned supporting structure are all aluminum alloy materials. In addition to using the aluminum alloy material used in this embodiment, other lightweight materials can also be used to reduce weight.

[0091] The following is an evaluation of the laser and long-wave infrared dual-band co-aperture optical system of this embodiment using various evaluation methods:

[0092] 1. Evaluation of the RMS radius (root mean square radius) of a point-to-point plot

[0093] A dot plot comprehensively describes the imaging quality of an optical system and is an important indicator for evaluating its imaging quality. The dot plot is formed by the phenomenon where, due to aberrations, the intersection of a beam of light emanating from a single point on the image plane is no longer a perfect image point, but rather a diffuse pattern scattered over a certain area. The dot plot ignores diffraction effects; therefore, its density reflects the magnitude of lateral aberrations and, to some extent, the energy distribution of the image. Furthermore, the compactness of the diffuse pattern distribution is used to judge the imaging quality of the optical system. In this embodiment, the full-field dot plot of the long-wave infrared imaging optical system formed by the aforementioned common-aperture objective lens assembly and the long-wave infrared imaging optical assembly is shown below. Figure 2 As shown, the RMS radius value of the dot plot is less than 10 micrometers; in this embodiment, the full field-of-view dot plot of the laser ranging and receiving optical system formed by the above-mentioned common aperture objective lens assembly and the laser ranging and receiving optical assembly is shown below. Figure 5 As shown, the RMS radius of the dot matrix is ​​less than 10 micrometers; its imaging quality can ensure the system's energy concentration requirements, thus meeting the needs of long-distance target detection.

[0094] 2. Distortion assessment

[0095] Distortion refers to the phenomenon where the actual angular magnification of the principal ray is not equal to +1, i.e., when the image-side principal ray is not parallel to the object-side principal ray, and the intersection point of the image-side principal ray and the ideal image plane does not coincide with the ideal image point. In the case of distortion alone, these points fall on a plane perpendicular to the optical axis, but there is a deviation in distance from the optical axis. That is, the presence of distortion does not affect image sharpness, but there is misalignment. The distortion diagram of the long-wave infrared imaging optical system formed by the above-mentioned common-aperture objective lens assembly and the long-wave infrared imaging optical assembly in this embodiment is shown below. Figure 3 As shown, the maximum distortion percentage varies with the field of view, which is -2.85%.

[0096] 3. Evaluation of the energy diagram of the surrounding circle

[0097] The bounding circle energy map, based on a circle centered on a Gaussian image point, is a parameter reflecting the change in energy magnitude of the image points contained within the circle as the circle's radius changes. In optical design software, a certain number of rays are used to trace rays from different fields of view, ultimately producing a blur spot on the image plane. The centroid of the blur spot is the centroid of the point map. The bounding circle energy map represents the energy distribution within a certain distance from the centroid of the point map, and the energy concentration is represented by the ratio of the energy falling within the circle to the total energy. Figure 4 The energy diagram of the enclosed circle of the long-wave infrared imaging optical system formed by the above-mentioned common aperture objective lens assembly and long-wave infrared imaging optical assembly in this embodiment is given. It can be seen from the figure that more than 70% of the energy is concentrated in the 45-micrometer radius diffusion spot, and the energy concentration of the optical system is good. Figure 6The energy diagram of the circle enclosed by the laser ranging and receiving optical system formed by the above-mentioned common aperture objective lens assembly and laser ranging and receiving optical assembly in this embodiment is given. It can be seen from the figure that more than 90% of the energy is concentrated in the 12.5-micrometer radius diffusion spot, and the energy concentration of the optical system is good.

[0098] 4. Modulation transfer function diagram

[0099] The modulation transfer function (MTF) is a key physical quantity for evaluating the performance of an imaging system. It quantitatively describes the imaging system's ability to transfer sinusoidal grating signals of different spatial frequencies through frequency domain analysis. Figure 7 The modulation transfer function diagram of the laser ranging and receiving optical system formed by the above-mentioned common aperture objective lens assembly and laser ranging and receiving optical assembly in this embodiment is given. It can be seen from the figure that the performance of the optical system is close to the theoretical diffraction limit within the cutoff frequency.

[0100] In summary, in the laser and long-wave infrared dual-band co-aperture optical system of the present invention, the imaging quality of both the long-wave infrared imaging optical system and the laser ranging and receiving optical system is close to the diffraction limit, enabling clear imaging. Therefore, the laser and long-wave infrared dual-band co-aperture optical system of the present invention can meet the high-precision detection requirements of distant targets. Furthermore, due to its light weight and small size, it can also be integrated into or applied to systems with strict requirements on weight and size.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A dual-band co-aperture optical system for laser and long-wave infrared wavelengths, characterized in that: This includes a common aperture objective lens assembly, a long-wave infrared imaging optical assembly, and a laser ranging and receiving optical assembly. The common aperture objective lens assembly includes a primary mirror (1) and a secondary mirror (2) arranged coaxially. The primary mirror (1) is a ring-shaped reflecting mirror with positive optical power; the secondary mirror (2) is a lens with positive optical power, and a dichroic film is coated on the surface of the mirror near the primary mirror (1), and when this surface is used as a reflecting surface, the optical power of this surface is negative. Long-wave infrared light radiated from the target itself and reflected laser light are incident on the main mirror (1), and after being reflected by the main mirror (1), they are incident on the secondary mirror (2). After being separated by the secondary mirror (2), the long-wave infrared light is reflected and the laser light is transmitted. The long-wave infrared imaging optical component is disposed on the reflected light path of the secondary mirror (2) to realize long-wave infrared imaging. It includes a three-reflecting mirror (31), a four-reflecting mirror (32), a Dewar window (33), and a cold filter (34). The three reflecting mirrors (31) are coaxial with the primary mirror (1) and are disposed on the side of the primary mirror (1) away from the secondary mirror (2); the four reflecting mirrors (32) are coaxially disposed between the primary mirror (1) and the three reflecting mirrors (31); both the three reflecting mirrors (31) and the four reflecting mirrors (32) are annular reflecting mirrors with positive optical power; the Dewar window (33) and the cold filter (34) are coaxially disposed in the central through hole of the three reflecting mirrors (31); After the long-wave infrared light reflected by the secondary mirror (2) forms an intermediate real image, it diverges and is incident on the three-reflector mirror (31), reflected by the three-reflector mirror (31) to the four-reflector mirror (32), and then reflected by the four-reflector mirror (32) to the Dewar window (33). After passing through the Dewar window (33) and the cold filter (34) in sequence, it converges to the long-wave infrared image plane (35) for docking with the cooled long-wave infrared detector for imaging. The Dewar window (33) and the cold filter (34) are both matched with the cooled long-wave infrared detector. The laser ranging receiving optical component is disposed on the transmission optical path of the secondary mirror (2) and is used to receive laser echoes to realize laser ranging imaging. It includes a first meniscus negative lens (41) bent towards the image side, a second meniscus negative lens (42) bent towards the image side, a first plane mirror (43) and a second plane mirror (44) bent towards the image side, a first meniscus positive lens (45) bent towards the image side, a third meniscus negative lens (46) bent towards the image side, a first biconcave negative lens (47), a first biconvex positive lens (48) and a second meniscus positive lens (49) bent towards the image side; the image side corresponding to each lens refers to the side of the outgoing light ray corresponding to each lens in the optical path. The optical axes of the first meniscus negative lens (41) and the second meniscus negative lens (42) are both coaxial with the optical axis of the secondary lens (2); The laser transmitted through the secondary mirror (2) is dispersed sequentially by the first meniscus negative lens (41) and the second meniscus negative lens (42) and then emitted in parallel, and enters the first plane mirror (43). The reflecting surface of the second plane mirror (44) is opposite to and perpendicular to the reflecting surface of the first plane mirror (43) for folding the optical path by 180°; The first meniscus positive lens (45), the third meniscus negative lens (46), the first biconcave negative lens (47), the first biconvex positive lens (48), and the second meniscus positive lens (49) are coaxially arranged in the output light path of the second plane mirror (44). After the output laser beam is diverged by the third meniscus negative lens (46) and formed into an image, it is then diverged and incident on the first biconcave negative lens (47). After passing through the first biconcave negative lens (47), the first biconvex positive lens (48), and the second meniscus positive lens (49) in sequence, it converges to the laser ranging receiving image plane (410). The wavelength of the laser is 0.8μm to 2μm; The focal length of the laser ranging and receiving optical system formed by the common aperture objective lens assembly and the laser ranging and receiving optical assembly is 100mm to 300mm, and the F number is 1 to 3.

2. The dual-band co-aperture optical system for laser and long-wave infrared as described in claim 1, characterized in that: The wavelength range of the long-wave infrared light is 7.7μm to 10.5μm; The long-wave infrared imaging optical system formed by the common aperture objective lens assembly and the long-wave infrared imaging optical assembly has a focal length of 100mm to 200mm and an F number of 1 to 3.

3. The dual-band co-aperture optical system for laser and long-wave infrared as described in claim 2, characterized in that: The axial distance between the primary mirror (1) and the secondary mirror (2) is -50mm to -20mm; The reflective surface of the primary mirror (1) and the surface of the secondary mirror (2) near the primary mirror (1) are both hyperboloids. The radius of curvature of the vertex of the reflecting surface of the primary mirror (1) is -120mm to -90mm; the radius of curvature of the vertex of the secondary mirror (2) on the side closer to the primary mirror (1) is -100mm to -30mm. The axial spacings between the secondary mirror (2) and the three-reflector mirror (31), the three-reflector mirror (31) and the four-reflector mirror (32), the four-reflector mirror (32) and the Dewar window (33), the Dewar window (33) and the cold filter (34), and the cold filter (34) and the long-wave infrared image plane (35) are 80mm~150mm, -80mm~-50mm, 50mm~80mm, 2mm~4mm, and 17mm~23mm, respectively. The reflecting surfaces of the three-reflecting mirror (31) and the four-reflecting mirror (32) are both even-order aspherical surfaces; The radii of curvature of the vertex of the reflecting surfaces of the three-reflecting mirror (31) and the four-reflecting mirror (32) are 2800mm to 4000mm and 50mm to 150mm, respectively.

4. The dual-band co-aperture optical system for laser and long-wave infrared as described in claim 3, characterized in that: It also includes the supporting structure; Each optical element in the common aperture objective lens assembly, the long-wave infrared imaging optical assembly, and the laser ranging and receiving optical assembly is installed and connected through the support structure. The primary mirror (1), the three reflecting mirrors (31) and the four reflecting mirrors (32) are all made of the same material as the supporting structure.

5. The dual-band co-aperture optical system for laser and long-wave infrared as described in claim 4, characterized in that: The long-wave infrared imaging optical component also includes a first field stop (36). The first field stop (36) is located at the intermediate real image position and is coaxial with the secondary mirror (2); the long-wave infrared light reflected by the secondary mirror (2) forms an intermediate real image at the first field stop (36) position and then passes through the first field stop (36) and diverges into the three reflecting mirrors (31). The first field stop (36) is made of the same material as the supporting structure; The inner surfaces of the central through holes of the main mirror (1), the three reflecting mirrors (31) and the four reflecting mirrors (32) are all coated with matte paint with an absorption rate of greater than or equal to 99%.

6. The dual-band co-aperture optical system for laser and long-wave infrared as described in claim 5, characterized in that: The primary mirror (1), the first field stop (36), the three reflecting mirrors (31), the four reflecting mirrors (32), and the supporting structure are all made of aluminum alloy. The secondary mirror (2) is made of optical glass HZLAF96, optical glass HK9L, or quartz. The four reflecting mirrors (32) are located on the back of the main mirror (1), and the main mirror (1) and the four reflecting mirrors (32) are an integral structure.

7. The laser and long-wave infrared dual-band co-aperture optical system according to any one of claims 1 to 6, characterized in that: The laser ranging receiver optical component also includes a second field stop (411). The second field stop (411) is located at the primary imaging position and is coaxial with the third meniscus negative lens (46).

8. The dual-band co-aperture optical system for laser and long-wave infrared as described in claim 7, characterized in that: The center thickness of the secondary mirror (2) is -8mm to -2mm; The center thickness of the first meniscus negative lens (41), the second meniscus negative lens (42), the first meniscus positive lens (45), the third meniscus negative lens (46), the first biconcave negative lens (47), the first biconvex positive lens (48), and the second meniscus positive lens (49) is between -5mm and -2mm. The axial intervals between the secondary mirror (2) and the first meniscus negative lens (41), the first meniscus negative lens (41) and the second meniscus negative lens (42), the first meniscus positive lens (45) and the third meniscus negative lens (46), the third meniscus negative lens (46) and the first biconcave negative lens (47), the first biconcave negative lens (47) and the first biconvex positive lens (48), the first biconvex positive lens (48) and the second meniscus positive lens (49), and the second meniscus positive lens (49) and the laser ranging receiving image plane (410) are -2mm to -0.5mm, -5mm to -1mm, -2mm to -0.2mm, -80mm to -40mm, -3mm to -0.5mm, -8mm to -2mm, and -25mm to -10mm, respectively. The object-side vertex radius of curvature of the first meniscus negative lens (41) is -50mm to -5mm, and the image-side vertex radius of curvature is -30mm to -2mm; the object-side vertex radius of curvature of the second meniscus negative lens (42) is -100mm to -5mm, and the image-side vertex radius of curvature is -50mm to -2mm; the object-side vertex radius of curvature of the first meniscus positive lens (45) is -50mm to -5mm, and the image-side vertex radius of curvature is -100mm to -20mm; the object-side vertex radius of curvature of the third meniscus negative lens (46) is... -20mm to -3mm, the vertex curvature radius of the image surface is -10mm to -2mm; the vertex curvature radius of the object surface of the first biconcave negative lens (47) is 5mm to 20mm, and the vertex curvature radius of the image surface is -50mm to -5mm; the vertex curvature radius of the object surface of the first biconvex positive lens (48) is -100mm to -50mm, and the vertex curvature radius of the image surface is 5mm to 50mm; the vertex curvature radius of the object surface of the second crescent positive lens (49) is -20mm to -5mm, and the vertex curvature radius of the image surface is -30mm to -8mm; The material of the first meniscus negative lens (41) is optical glass HZLAF96 or HZLAF92; the material of the second meniscus negative lens (42) is optical glass HZLAF96 or HZLAF92; the material of the first plane mirror (43) is optical glass HK9L, quartz or microcrystalline; the material of the second plane mirror (44) is optical glass HK9L, quartz or microcrystalline; the material of the first meniscus positive lens (45) is optical glass HQK1 or HQK3L; the material of the third meniscus negative lens (46) is optical glass HQK1 or HQK3L; the material of the first biconcave negative lens (47) is optical glass HK11 or HK10; the material of the first biconvex positive lens (48) is optical glass HZLAF92 or HZLAF96; the material of the second meniscus positive lens (49) is optical glass HZF3 or HZF6.

Images