Large-aperture wide-angle space-based laser perception optical system

Abstract

This invention provides a large-aperture, wide-angle laser sensing optical system, solving the problems of small sensing space and small aperture in existing space-based laser sensing systems. The optical system includes, from left to right, a first lens, a second lens, a third lens, a light-diffusing plate, a fourth lens, a fifth lens, and an uncooled long-wave infrared detector. The left side of the first lens is the object plane, and the right side of the fifth lens is the long-wave infrared detector. The first lens is a meniscus negative lens curved towards the image side, the second lens is a meniscus positive lens curved towards the image side, the third lens is a meniscus positive lens curved towards the object side, the light-diffusing plate is a parallel plate, the fourth lens is a meniscus negative lens curved towards the image side, and the fifth lens is a biconvex positive lens. This invention is compact, has superior imaging performance, and good image plane illumination uniformity, thus improving the field of view and sensitivity of space-based laser sensing systems.

Description

Technical Field

[0001] This invention belongs to the field of laser sensing optical design, specifically relating to a large-aperture wide-angle laser sensing optical system. Background Technology

[0002] With the rapid development of ground-based laser weapon technology, high-energy lasers emitted from the ground can directly destroy low-Earth orbit (LEO) satellites or dazzle or blind the optical payloads carried on these satellites, rendering them ineffective. Military powers such as the United States and Russia have already acquired the capability to use laser weapons to strike LEO satellites. Due to their fixed orbits and easily identifiable target characteristics, my country's LEO satellites face a serious threat from laser weapons. Therefore, research into space-based laser sensing technology is urgently needed to promptly detect high-energy laser threats, buying valuable time for LEO satellites to take evasive action. This will effectively protect the satellite body and optical payloads from laser weapon damage, thereby improving the survivability of my country's satellites.

[0003] Laser sensing technology, as a core component of space-based laser countermeasures, can quickly and accurately detect the location and other information of incoming lasers. Its typical requirements are a large sensing range and long sensing distance. According to basic optical principles, large-aperture optical systems are beneficial for improving system detection capabilities. However, as the optical aperture and detection field of view increase, the structural complexity of the optical system increases, along with its size and weight. For resource-constrained satellite platforms, lightweight and miniaturized payloads are more advantageous for equipment use. Therefore, it is necessary to design a large relative aperture, large field of view, and lightweight miniaturized optical system for space-based laser sensing systems to improve sensing sensitivity.

[0004] Currently, most laser sensing optical systems are based on airborne and ground-based platforms. Patent CN112180588A discloses a design method for a large field-of-view laser sensing lens, but this system can only achieve single-band laser sensing, limiting its applicability. Patent CN 112180548A discloses a near-infrared fisheye optical system for airborne laser sensing, which uses 10 lenses with a maximum aperture of 65mm, resulting in a relatively large overall size. In summary, there are currently few optical systems suitable for space-based laser sensing systems, and the published patents cannot meet the requirements for miniaturization. Therefore, researching how to realize a large-aperture, wide-angle space-based laser sensing optical system is a crucial problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention proposes a large-aperture, wide-angle space-based laser sensing optical system that can detect and sense long-wave infrared high-energy lasers, while simultaneously achieving a lightweight and miniaturized optical system design.

[0006] The technical solution for realizing the present invention is as follows: a large aperture wide-angle laser sensing optical system, comprising a first lens, a second lens, a third lens, a light decay plate, a fourth lens, a fifth lens, and an uncooled long-wave infrared detector arranged coaxially from left to right; the left side of the first lens is the object plane, and the right side of the fifth lens is the uncooled long-wave infrared detector.

[0007] Compared with the prior art, the significant advantages of this invention are:

[0008] (1) The laser sensing optical system of the present invention uses 5 optical lenses. By selecting optical structure, selecting optical materials and using high-order aspherical surfaces, the field of view of the optical system reaches 90°×90°, the relative aperture of the system reaches 1 / 0.87, and the f-Theta distortion of the optical system is ≤0.1%, which greatly improves the detection field of view and relative aperture of the optical system, and improves the angle measurement accuracy and detection sensitivity of the system.

[0009] (2) The laser sensing optical system of the present invention, through the selection of lens shape and the reasonable allocation of lens power, makes the incident angle of the light beam of the light decay plate less than ±8°, which greatly ensures the consistency of light decay of the light beam in the field of view.

[0010] (3) The laser sensing optical system of the present invention uses only one 6th order aspherical lens and one 10th order aspherical lens, making the total length of the optical system less than 65mm and the maximum aperture less than 27mm. Compared with the global surface design optical system, it is easier to achieve a lightweight and miniaturized structure, and requires fewer lenses, resulting in lower cost and making it more suitable for mass production and mass production on satellite platforms.

[0011] (4) The laser sensing optical system of this invention can be used in defocus mode. By defocusing, the radius of the light spot is increased, reducing the energy density of the light spot on the detector surface, thereby protecting the detector from laser damage. This invention adopts an image-side telecentric optical path to ensure that the incident height of the principal ray on the image surface remains unchanged under different defocusing amounts, thus ensuring that the angle measurement accuracy remains basically unchanged under different defocusing amounts. In addition, the use of an image-side telecentric optical path also effectively reduces the difficulty of image-side docking and assembly of the optical system. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the optical system according to an embodiment of the present invention.

[0013] Figure 2 This is a dot diagram of the optical system according to an embodiment of the present invention.

[0014] Figure 3 This is the MTF curve of the optical system in an embodiment of the present invention.

[0015] Figure 4This is the f-Theta curve of the optical system in this embodiment of the invention.

[0016] Figure 5 This is the relative illumination curve of the optical system in an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached diagram: 1-First lens, 2-Second lens, 3-Third lens, 4-Fourth lens, 5-Fifth lens, 6-Attenuator, 7-Uncooled long-wave infrared detector, 701-Detector protection window, STOP-Aperture stop, IMA-Image plane. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0020] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly and specifically defined.

[0021] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; "connection" can mean a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible to those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0023] The following section will further introduce the specific implementation method, as well as the technical difficulties and inventive points of this invention, using this design example as an example.

[0024] Combination Figure 1 The present invention discloses a large-aperture wide-angle space-based laser sensing optical system, comprising a first lens, a second lens, a third lens, a light-diffusing plate, a fourth lens, a fifth lens, and an uncooled long-wave infrared detector, arranged coaxially from left to right along the incident light direction. The left side of the first lens is the object plane, and the right side of the fifth lens is the uncooled long-wave infrared detector. An aperture stop is disposed between the second lens and the third lens. The uncooled long-wave infrared detector includes a detector protective window and an image plane.

[0025] The first lens is a meniscus negative lens bent towards the image side, the second lens is a meniscus positive lens bent towards the image side, the third lens is a meniscus positive lens bent towards the object side, the attenuator is a parallel plate, the fourth lens is a meniscus negative lens bent towards the image side, and the fifth lens is a biconvex positive lens.

[0026] The first lens, second lens, third lens, fourth lens, and fifth lens satisfy the following relationships: -2.5≤f1 / f≤-2.1, 3.5≤f2 / f≤4.1, 11.6≤f3 / f≤11.9, -14.6≤f4 / f≤-14.0, 1.9≤f5 / f≤2.6; where f is the focal length of the optical system, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens.

[0027] Further, the center thickness of the first lens is 3.0mm to 3.7mm, and its front surface (i.e., the left surface) and rear surface (i.e., the right surface) are spherical; the center thickness of the second lens is 3.0mm to 4.2mm, its front surface is aspherical, and its rear surface is spherical; the center thickness of the third lens is 2.2mm to 3.5mm, its front surface is aspherical, and its rear surface is spherical; the center thickness of the attenuator is 2.0mm to 4.0mm, its front surface is planar, and its rear surface is planar; the center thickness of the fourth lens is 2.5mm to 3.4mm, its front surface is spherical, and its rear surface is spherical; the center thickness of the fifth lens is 3.3mm to 4.0mm, its front surface is spherical, and its rear surface is spherical.

[0028] Further, the air gap between the first lens and the second lens is 23.0 mm to 25.0 mm, the air gap between the second lens and the aperture is 2.5 mm to 3.1 mm, the air gap between the aperture and the third lens is 3.0 mm to 4.2 mm, the distance between the third lens and the attenuator is 0.1 mm to 3.0 mm, the distance between the attenuator and the fourth lens is 1.0 mm to 2.0 mm, and the distance between the fourth lens and the fifth lens is 2.8 mm to 4.0 mm.

[0029] Furthermore, the center thickness of the first lens is 3.4 mm; the center thickness of the second lens is 3.5 mm; the center thickness of the third lens is 2.8 mm; the center thickness of the light-diffusing film is 3.0 mm; the center thickness of the fourth lens is 3.0 mm; and the center thickness of the fifth lens is 3.6 mm.

[0030] Furthermore, the air gap between the first lens and the second lens is 24.1 mm, the air gap between the second lens and the aperture is 2.7 mm, the air gap between the aperture and the third lens is 3.8 mm, the distance between the third lens and the light decay plate is 1.5 mm, the distance between the light decay plate and the fourth lens is 1.5 mm, and the distance between the fourth lens and the fifth lens is 3.4 mm.

[0031] Furthermore, the optical system operates in the long-wave infrared band; a detector protective glass is provided on the right side of the fifth lens, and the protective glass is made of single-crystal germanium material.

[0032] Furthermore, the f-theta distortion of the optical system is ≤0.1%.

[0033] Furthermore, the first lens is made of monocrystalline silicon, the second lens is made of monocrystalline silicon, the third lens is made of monocrystalline silicon, the substrate material of the degrading film is made of monocrystalline silicon, the fourth lens is made of zinc selenide, and the fifth lens is made of monocrystalline germanium.

[0034] Furthermore, the first lens, second lens, third lens, fourth lens, and fifth lens are all coated with anti-reflection films to reduce the absorption of strong laser light by the optical glass.

[0035] Furthermore, the front surface of the first lens is coated with a bandpass filter to ensure that strong laser light outside the working band is reflected and does not enter the optical system, thus preventing a decrease in sensing performance.

[0036] Furthermore, the surface of the light-attenuating plate is coated with an absorption film, and its edge field transmittance is 5 to 10 times that of the center field transmittance, so as to ensure that the incident light response intensity of different fields of view on the detector surface is basically the same.

[0037] Example 1

[0038] This invention provides a large-aperture wide-angle space-based laser sensing optical system, comprising a first lens 1, a second lens 2, a third lens 3, a light-diffusing filter 6, a fourth lens 4, a fifth lens 5, and an uncooled long-wave infrared detector 7, coaxially arranged from left to right along the incident light direction. The left side of the first lens 1 is the object plane, and the right side of the fifth lens 5 is the uncooled long-wave infrared detector 7. An aperture stop (STOP) is placed between the second lens 2 and the third lens 3. The light-diffusing filter 6 is placed between the third lens 3 and the fourth lens 4. The uncooled long-wave infrared detector 7 includes a detector protective window 701 and an image plane (IMA).

[0039] The first lens 1 is a meniscus negative lens bent towards the image side, made of monocrystalline silicon; the second lens 2 is a meniscus positive lens bent towards the image side, made of monocrystalline silicon; the third lens 3 is a meniscus positive lens bent towards the object side, made of monocrystalline silicon; the attenuator 6 is a parallel plate, with monocrystalline silicon as the substrate material; the fourth lens 4 is a meniscus negative lens bent towards the image side, made of zinc selenide; and the fifth lens 5 is a biconvex positive lens, made of monocrystalline germanium.

[0040] The first lens 1, the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5 satisfy the following relationship: -2.5≤f1 / f≤-2.1, 3.5≤f2 / f≤4.1, 11.6≤f3 / f≤11.9, -14.6≤f4 / f≤-14.0, 1.9≤f5 / f≤2.6; where f is the focal length of the optical system, f1 is the focal length of the first lens 1, f2 is the focal length of the second lens 2, f3 is the focal length of the third lens 3, f4 is the focal length of the fourth lens 4, and f5 is the focal length of the fifth lens 5.

[0041] The large-aperture wide-angle space-based laser sensing optical system of this invention achieves a large aperture, large field of view, and miniaturization by using non-high-order spherical surfaces. Specifically, the center thickness of the first lens 1 is 3.0mm to 3.7mm, and its front surface (i.e., the left surface) and rear surface (i.e., the right surface) are spherical; the center thickness of the second lens 2 is 3.0mm to 4.2mm, and its front surface is a sixth-order aspherical surface and its rear surface is spherical; the center thickness of the third lens 3 is 2.2mm to 3.5mm, and its front surface is a twelfth-order aspherical surface and its rear surface is spherical; the center thickness of the light-diffusing plate 6 is 2.0mm to 4.0mm, and its front surface and rear surface are both planar; the center thickness of the fourth lens 4 is 2.5mm to 3.4mm, and its front surface and rear surface are both spherical; the center thickness of the fifth lens 5 is 3.3mm to 4.0mm, and its front surface and rear surface are both spherical.

[0042] The air gap between the first lens 1 and the second lens 2 is 23.0 mm to 25.0 mm; the air gap between the second lens 2 and the stop aperture is 2.5 mm to 3.1 mm; the air gap between the stop aperture and the third lens 3 is 3.0 mm to 4.2 mm; the distance between the third lens 3 and the attenuator 6 is 0.1 mm to 3.0 mm; the distance between the attenuator 6 and the fourth lens 4 is 1.0 mm to 2.0 mm; and the distance between the fourth lens 4 and the fifth lens 5 is 2.8 mm to 4.0 mm. The distance between the fifth lens 5 and the detector protective window 701 is 5.5 mm.

[0043] In this embodiment of the invention, the center thickness of the first lens 1 is 3.4 mm; the center thickness of the second lens 2 is 3.5 mm; the center thickness of the third lens 3 is 2.8 mm; the center thickness of the light decay plate 6 is 3.0 mm; the center thickness of the fourth lens 4 is 3.0 mm; the center thickness of the fifth lens 5 is 3.6 mm; and the thickness of the detector protective window 701 is 1 mm.

[0044] The air gap between the first lens 1 and the second lens 2 is 24.1 mm, the air gap between the second lens 2 and the stop is 2.7 mm, the air gap between the stop and the third lens 3 is 3.8 mm, the distance between the third lens 3 and the attenuator 6 is 1.5 mm, the distance between the attenuator 6 and the fourth lens 4 is 1.5 mm, the distance between the fourth lens 4 and the fifth lens 5 is 3.4 mm, the distance between the fifth lens 5 and the detector protection window 701 is 5.5 mm, and the distance between the detector protection window 701 and the image plane IMA behind it is 2.13 mm.

[0045] The first lens 1, the second lens 2, the third lens 3, the fourth lens 4, and the fifth lens 5 are all coated with anti-reflection coatings to reduce the absorption of strong laser light by the optical glass.

[0046] The front surface of the first lens 1 is coated with a bandpass filter to ensure that strong lasers outside the working band are reflected and do not enter the optical system, thus preventing a decrease in sensing performance.

[0047] The surface of the light decay plate 6 is coated with an absorption film, and its edge field transmittance is 5 to 10 times that of the center field transmittance, so as to ensure that the incident light response intensity of different fields on the detector surface is basically the same.

[0048] The various numerical data related to the large-aperture wide-angle space-based laser sensing optical system involved in this embodiment are shown in Tables 1 and 2:

[0049] Table 1. Specific parameters of each lens in the optical system of this embodiment (unit: mm)

[0050]

[0051] Table 2 Aspheric Coefficients of the Optical System in the Example Implementation

[0052] Aspheric coefficient Second lens Third lens A4 2.57E-06 -5.66E-05 A6 4.59E-08 1.25E-07 A8 0 -4.94E-09 A10 0 2.34E-11

[0053] like Figure 2 As shown, the RMS radius of the imaging spot in different fields of view ranges from 4.4 μm to 5.6 μm, which is less than half the size of a single pixel (8.5 μm), and the spot radius is relatively uniform, indicating that the spot quality is similar across the entire field of view. Figure 3 As shown, the transfer functions for different fields of view are all greater than 0.57, close to the diffraction limit, indicating that the system has good imaging quality. Figure 4 As shown, the illuminance at the edge of the optical system's field of view is 85% of that at the center field of view, indicating that the system has good image plane illuminance consistency. Figure 5 As shown, the maximum f-Theta distortion of this system is only 0.065%, indicating that the system has high angle measurement accuracy.

[0054] This invention discloses a large-aperture, wide-angle space-based laser sensing optical system with advantages such as a large field of view, large relative aperture, high optical transfer function, good in-plane illumination uniformity, and minimal f-Theta distortion. The alarm field of view reaches 90°×90°, the system's relative aperture reaches 1 / 0.87, and the maximum f-Theta distortion is only 0.065%, achieving high angle measurement accuracy and detection sensitivity. The laser sensing optical system of this invention employs a design combining three spherical surfaces and two high-order aspherical surfaces, resulting in an optical envelope size no larger than Φ27mm×65mm. This facilitates structural miniaturization, requires fewer lenses, lowers costs, and is more conducive to mass production, making it suitable for mass deployment on satellite platforms. Furthermore, this invention uses an image-side telecentric structure, allowing for defocusing while maintaining angle measurement accuracy, thereby reducing the energy density of the light spot on the detector surface and protecting the detector from laser damage.

[0055] Analysis of the embodiments shows that the optical system is compact and has good imaging capabilities, meeting the requirements of space-based laser sensing systems for large sensing range, long sensing distance, and miniaturization.

Claims

1. A large-aperture wide-angle laser sensing optical system, characterized in that: It includes a first lens, a second lens, a third lens, a light-diffusing plate, a fourth lens, a fifth lens, and an uncooled long-wave infrared detector arranged coaxially from left to right; the left side of the first lens is the object plane, and the right side of the fifth lens is the uncooled long-wave infrared detector; The optical system further includes an aperture stop disposed between the second lens and the third lens; The first lens is a meniscus negative lens bent towards the image side, the second lens is a meniscus positive lens bent towards the image side, the third lens is a meniscus positive lens bent towards the object side, the attenuator is a parallel plate, the fourth lens is a meniscus negative lens bent towards the image side, and the fifth lens is a biconvex positive lens. The first lens, second lens, third lens, fourth lens, and fifth lens satisfy the following relationships: -2.5≤f1 / f≤-2.1, 3.5≤f2 / f≤4.1, 11.6≤f3 / f≤11.9, -14.6≤f4 / f≤-14.0, 1.9≤f5 / f≤2.6; where f is the focal length of the optical system, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens.

2. The large-aperture wide-angle laser sensing optical system as described in claim 1, characterized in that: The first lens has a center thickness of 3.0mm to 3.7mm, and its front and rear surfaces are spherical; the second lens has a center thickness of 3.0mm to 4.2mm, and its front and rear surfaces are aspherical; the third lens has a center thickness of 2.2mm to 3.5mm, and its front and rear surfaces are aspherical; the light-diffusing filter has a center thickness of 2.0mm to 4.0mm, and its front and rear surfaces are planar; the fourth lens has a center thickness of 2.5mm to 3.4mm, and its front and rear surfaces are spherical; the fifth lens has a center thickness of 3.3mm to 4.0mm, and its front and rear surfaces are spherical.

3. The large-aperture wide-angle laser sensing optical system as described in claim 2, characterized in that: The air gap between the first lens and the second lens is 23.0 mm to 25.0 mm, the air gap between the second lens and the aperture is 2.5 mm to 3.1 mm, the air gap between the aperture and the third lens is 3.0 mm to 4.2 mm, the distance between the third lens and the light decay plate is 0.1 mm to 3.0 mm, the distance between the light decay plate and the fourth lens is 1.0 mm to 2.0 mm, and the distance between the fourth lens and the fifth lens is 2.8 mm to 4.0 mm.

4. The large-aperture wide-angle laser sensing optical system as described in claim 3, characterized in that: The air gap between the first lens and the second lens is 24.1 mm, the air gap between the second lens and the aperture is 2.7 mm, the air gap between the aperture and the third lens is 3.8 mm, the distance between the third lens and the light decay plate is 1.5 mm, the distance between the light decay plate and the fourth lens is 1.5 mm, and the distance between the fourth lens and the fifth lens is 3.4 mm.

5. A large-aperture wide-angle laser sensing optical system as described in any one of claims 1 to 4, characterized in that: The optical system operates in the long-wave infrared band; a detector protective glass is provided on the right side of the fifth lens, and the protective glass is made of single-crystal germanium material.

6. The large-aperture wide-angle laser sensing optical system as described in claim 5, characterized in that: The optical system has an f-theta distortion of ≤0.1%.

7. The large-aperture wide-angle laser sensing optical system as described in claim 6, characterized in that: The first lens is made of monocrystalline silicon, the second lens is made of monocrystalline silicon, the third lens is made of monocrystalline silicon, the substrate material of the attenuator is made of monocrystalline silicon, the fourth lens is made of zinc selenide, and the fifth lens is made of monocrystalline germanium.

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