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

Abstract

The invention provides a large-aperture wide-angle laser sensing optical system, which solves the problems of small sensing airspace and small aperture of the existing space-based laser sensing system, and comprises a first lens, a second lens, a third lens, a light attenuation sheet, a fourth lens, a fifth lens and an uncooled long-wave infrared detector which are arranged from left to right, the left side of the first lens is an object plane, and the right side of the fifth lens is a long-wave infrared detector. The first lens is a negative meniscus lens bent towards the image space, the second lens is a positive meniscus lens bent towards the image space, the third lens is a positive meniscus lens bent towards the object space, the light attenuation sheet is a parallel flat plate, the fourth lens is a negative meniscus lens bent towards the image space, and the fifth lens is a biconvex positive lens. The space-based laser sensing system is compact in size, excellent in imaging performance and good in image surface illumination uniformity, and the view field and the sensitivity of the space-based laser sensing system can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of laser sensing optical design, and in particular relates to a large-aperture wide-angle laser sensing optical system. Background Art

[0002] With the rapid development of ground-based laser weapon technology, high-energy lasers launched from the ground can directly damage low-orbit satellites or dazzle or blind the optical payloads on low-orbit satellites and render them ineffective. Military powers such as the United States and Russia already have the combat capability to use laser weapons to attack low-orbit satellites. Due to the fixed orbits and obvious target characteristics of my country's low-orbit satellites, they face serious threats from laser weapons. Therefore, it is urgent to study space-based laser sensing technology to detect high-energy laser threats in a timely manner and buy precious time for low-orbit satellites to make evasive actions, so as to effectively protect the satellite body and optical payloads from damage by laser weapons, thereby improving the survivability of my country's satellites.

[0003] As a core component of space laser countermeasure technology, laser sensing technology can quickly and accurately detect the direction of incoming lasers and other information. Its typical requirements are large sensing range and long sensing distance. According to the basic principles of optics, large-aperture optical systems are conducive to improving the detection capability of the system. However, as the optical aperture and detection field of view increase, the structural complexity of the optical system increases, and the volume and weight increase accordingly. For satellite platforms with limited resources, light and miniaturized payloads are more conducive to equipment use. Therefore, it is necessary to design a large relative aperture, large field of view, light and miniaturized optical system for the space-based platform laser sensing system to improve the sensing sensitivity.

[0004] At present, most laser sensing optical systems are based on airborne and ground-based platforms. Patent CN112180588A discloses a method for designing a large-field-of-view laser sensing lens, but the system can only achieve single-band laser sensing, and its scope of application is limited. Patent CN 112180548A discloses a near-infrared fisheye optical system for airborne laser sensing, which uses 10 lenses with a maximum lens aperture of 65mm and a large overall size. In summary, there are currently few optical systems suitable for space-based laser sensing systems, and the disclosed patents cannot meet the needs of lightweight and miniaturization. Therefore, studying how to realize a large-aperture, wide-angle space-based laser sensing optical system is an important issue that technicians in this field need to solve urgently. Summary of the invention

[0005] The present invention proposes a large-aperture, wide-angle space-based laser sensing optical system, which can detect and sense long-wave infrared high-energy lasers while realizing a lightweight and miniaturized design of the optical system.

[0006] The technical solution to implement the present invention is: a large-aperture wide-angle laser sensing optical system, including a first lens, a second lens, a third lens, a light attenuation plate, a fourth lens, a fifth lens, and an uncooled long-wave infrared detector coaxially arranged 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 present invention has the following significant advantages:

[0008] (1) The laser sensing optical system of the present invention adopts 5 optical lenses. Through the selection of optical structure, optical material and the use of high-order aspheric 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 angular measurement accuracy and detection sensitivity of the system.

[0009] (2) The laser sensing optical system of the present invention makes the incident angle of the light beam of the attenuation plate less than ±8° through the selection of lens shape and the reasonable distribution of lens optical power, thereby ensuring the attenuation consistency of the light beam in the field of view of the attenuation plate to a great extent.

[0010] (3) The laser sensing optical system of the present invention uses only one 6th-order aspheric lens and one 10th-order aspheric lens, so that the total length of the optical system is less than 65 mm and the maximum aperture is less than 27 mm. Compared with the optical system with a spherical design, it is easier to achieve a lightweight and miniaturized structure, and the number of lenses required is less, the cost is lower, and it is more conducive to mass production, and is suitable for mass equipment of satellite platforms.

[0011] (4) The laser sensing optical system of the present invention can be used in a defocused manner. By defocusing, the spot radius is increased, and the spot energy density on the detector surface is reduced, thereby protecting the detector from laser damage. The present invention adopts an image-side telecentric optical path to ensure that the incident height of the principal ray on the image plane remains unchanged under different defocus amounts, thereby ensuring that the angle measurement accuracy does not change substantially under different defocus 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the structure of an optical system according to an embodiment of the present invention.

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

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

[0015] Figure 4: is the f-Theta curve of the optical system of the embodiment of the present invention.

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

[0017] Explanation of the reference numerals: 1-first lens, 2-second lens, 3-third lens, 4-fourth lens, 5-fifth lens, 6-attenuation plate, 7-uncooled long-wave infrared detector, 701-detector protection window, STOP-aperture, IMA-image plane. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0020] In addition, in the present invention, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0021] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation" and the like should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; "connection" can be a mechanical connection or an electrical connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

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

[0024] Combination Figure 1 The large-aperture wide-angle space-based laser sensing optical system described in the present invention comprises 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 coaxially arranged from left to right along the incident direction of light; 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 arranged between the second lens and the third lens. The uncooled long-wave infrared detector comprises a detector protection window and an image plane.

[0025] The first lens is a negative meniscus lens bent toward the image side, the second lens is a positive meniscus lens bent toward the image side, the third lens is a positive meniscus lens bent toward the object side, the attenuation plate is a parallel flat plate, the fourth lens is a negative meniscus lens bent toward the image side, and the fifth lens is a double convex positive lens.

[0026] The first lens, the second lens, the third lens, the fourth lens, and the fifth lens 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; wherein 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] Furthermore, the center thickness of the first lens is 3.0mm~3.7mm, its front surface (i.e., the left surface) is spherical, and the rear surface (i.e., the right surface) is spherical; the center thickness of the second lens is 3.0mm~4.2mm, its front surface is aspherical, and the rear surface is spherical; the center thickness of the third lens is 2.2mm~3.5mm, its front surface is aspherical, and the rear surface is spherical; the center thickness of the attenuation plate is 2.0mm~4.0mm, its front surface is flat, and the rear surface is flat; the center thickness of the fourth lens is 2.5mm~3.4mm, its front surface is spherical, and the rear surface is spherical; the center thickness of the fifth lens is 3.3mm~4.0mm, its front surface is spherical, and the rear surface is spherical.

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

[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 attenuation plate 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 attenuation plate is 1.5 mm, the distance between the attenuation 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 protection glass is arranged on the right side of the fifth lens, and the protection 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 single crystal silicon material, the second lens is made of single crystal silicon material, the third lens is made of single crystal silicon material, the attenuation film substrate material is made of single crystal silicon material, the fourth lens is made of zinc selenide, and the fifth lens is made of single crystal germanium material.

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

[0035] Furthermore, a bandpass filter film is coated on the front surface of the first lens to ensure that strong laser light outside the working band is reflected and does not enter the optical system, thereby preventing the perception efficiency from being reduced.

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

[0037] Example 1

[0038] The present 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 decay plate 6, a fourth lens 4, a fifth lens 5, and an uncooled long-wave infrared detector 7, which are coaxially arranged in sequence from left to right along the incident direction of light; the left side of the first lens 1 is an object plane, and the right side of the fifth lens 5 is an uncooled long-wave infrared detector 7. An aperture stop STOP is arranged between the second lens 2 and the third lens 3. A light decay plate 6 is arranged between the third lens 3 and the fourth lens 4. The uncooled long-wave infrared detector 7 includes a detector protection window 701 and an image plane IMA.

[0039] The first lens 1 is a negative meniscus lens bent toward the image side, and is made of single crystal silicon; the second lens 2 is a positive meniscus lens bent toward the image side, and is made of single crystal silicon; the third lens 3 is a positive meniscus lens bent toward the object side, and is made of single crystal silicon; the attenuation plate 6 is a parallel plate, and the base material is single crystal silicon; the fourth lens 4 is a negative meniscus lens bent toward the image side, and is made of zinc selenide; the fifth lens 5 is a double convex positive lens, and is made of single crystal 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; wherein f is the focal length value of the optical system, f1 is the focal length value of the first lens 1, f2 is the focal length value of the second lens 2, f3 is the focal length value of the third lens 3, f4 is the focal length value of the fourth lens 4, and f5 is the focal length value of the fifth lens 5.

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

[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 aperture STOP is 2.5 mm to 3.1 mm, the air gap between the aperture STOP and the third lens 3 is 3.0 mm to 4.2 mm, the distance between the third lens 3 and the light decay plate 6 is 0.1 mm to 3.0 mm, the distance between the light decay plate 6 and the fourth lens 4 is 1.0 mm to 2.0 mm, 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 protection window 701 is 5.5 mm.

[0043] In the embodiment of the present 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 attenuation 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 protection 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 aperture STOP is 2.7 mm, the air gap between the aperture STOP and the third lens 3 is 3.8 mm, the distance between the third lens 3 and the light decay plate 6 is 1.5 mm, the distance between the light decay plate 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 films to reduce the absorption of strong laser by the optical glass.

[0046] The front surface of the first lens 1 is coated with a bandpass filter film to ensure that strong laser light outside the working band is reflected and does not enter the optical system, thereby preventing the perception efficiency from being reduced.

[0047] The surface of the attenuation sheet 6 is coated with an absorption film, and the transmittance of the edge field of view is 5 to 10 times that of the central field of view, so as to ensure that the incident light response intensity of different fields of view on the detector surface is basically consistent.

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

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

[0050]

[0051] Table 2 Aspheric coefficients of the optical system of the embodiment

[0052] Aspheric coefficient Second lens The 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 in the figure, the RMS radius of the imaging spot in different fields of view is in the range of 4.4μm to 5.6μm, which is less than half of the size of a single pixel, 8.5μm, and the spot radius is relatively uniform, indicating that the quality of the spot in the entire field of view is similar. Figure 3 As shown in Figure 1, the transfer functions of different fields of view are all greater than 0.57, close to the diffraction limit, indicating that the imaging quality of the system is good. Figure 4 As shown in the figure, the illumination of the edge field of view of the optical system is 85% of the illumination of the central field of view, indicating that the illumination consistency of the image plane of the system is good. Figure 5 As shown, the maximum f-Theta distortion of the system is only 0.065%, indicating that the system has high angle measurement accuracy.

[0054] The present invention discloses a large-aperture, wide-angle space-based laser sensing optical system with the advantages of large field of view, large relative aperture, high optical transfer function, good uniformity of illumination in the image plane, and extremely small f-Theta distortion. The warning field of view reaches 90°×90°, the relative aperture of the system reaches 1 / 0.87, and the maximum f-Theta distortion of the system is only 0.065%, which can achieve higher angle measurement accuracy and detection sensitivity. The laser sensing optical system of the present invention adopts a design method combining three spherical surfaces with two high-order aspherical surfaces, so that the optical envelope size is no more than Φ27mm×65mm, which makes it easier to achieve lightweight and miniaturized structure, and the number of lenses required is less, the cost is lower, and it is more conducive to mass production, which is suitable for mass equipment of satellite platforms. In addition, the present invention adopts an image-side telecentric structure, which can be used in a defocused manner while ensuring the angle measurement accuracy, thereby reducing the energy density of the spot on the detector surface, thereby protecting the detector from laser damage.

[0055] The analysis of the examples shows that the optical system is compact and has good imaging performance, which meets the requirements of the space-based laser sensing system for a large sensing range, a long sensing distance, and light weight 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 attenuation plate, a fourth lens, a fifth lens, and an uncooled long-wave infrared detector which are coaxially arranged from left to right; the left side of the first lens is an object plane, and the right side of the fifth lens is an uncooled long-wave infrared detector.

2. A large-aperture wide-angle laser sensing optical system according to claim 1, characterized in that: The optical system also includes an aperture stop disposed between the second lens and the third lens.

3. A large aperture wide angle laser sensing optical system as claimed in claim 1, characterized in that: The first lens is a negative meniscus lens bent toward the image side, the second lens is a positive meniscus lens bent toward the image side, the third lens is a positive meniscus lens bent toward the object side, the attenuation plate is a parallel flat plate, the fourth lens is a negative meniscus lens bent toward the image side, and the fifth lens is a double convex positive lens.

4. A large aperture wide angle laser sensing optical system as claimed in claim 3, characterized in that: The first lens, the second lens, the third lens, the fourth lens, and the fifth lens 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; wherein 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.

5. The large-aperture wide-angle laser sensing optical system according to claim 1, characterized in that: The center thickness of the first lens is 3.0mm~3.7mm, its front surface is spherical, and the rear surface is spherical; the center thickness of the second lens is 3.0mm~4.2mm, its front surface is aspherical, and the rear surface is spherical; the center thickness of the third lens is 2.2mm~3.5mm, its front surface is aspherical, and the rear surface is spherical; the center thickness of the attenuation plate is 2.0mm~4.0mm, its front surface is flat, and the rear surface is flat; the center thickness of the fourth lens is 2.5mm~3.4mm, its front surface is spherical, and the rear surface is spherical; the center thickness of the fifth lens is 3.3mm~4.0mm, its front surface is spherical, and the rear surface is spherical.

6. A large aperture wide angle laser sensing optical system as claimed in claim 5, characterized in that: The air gap between the first lens and the second lens is 23.0mm~25.0mm, the air gap between the second lens and the aperture is 2.5mm~3.1mm, the air gap between the aperture and the third lens is 3.0mm~4.2mm, the distance between the third lens and the attenuation plate is 0.1mm~3.0mm, the distance between the attenuation plate and the fourth lens is 1.0mm~2.0mm, and the distance between the fourth lens and the fifth lens is 2.8mm~4.0mm.

7. A large aperture wide angle laser sensing optical system as claimed in claim 6, 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 attenuation plate is 1.5 mm, the distance between the attenuation plate and the fourth lens is 1.5 mm, and the distance between the fourth lens and the fifth lens is 3.4 mm.

8. A large aperture wide angle laser sensing optical system according to any one of claims 1 to 6, characterized in that: The optical system works in the long-wave infrared band; a detector protection glass is arranged on the right side of the fifth lens, and the protection glass is made of single crystal germanium material.

9. A large aperture wide angle laser sensing optical system as claimed in claim 8, characterized in that: The f-theta distortion of the optical system is ≤0.1%.

10. A large aperture wide angle laser sensing optical system as claimed in claim 9, characterized in that: The first lens is made of single crystal silicon material, the second lens is made of single crystal silicon material, the third lens is made of single crystal silicon material, the attenuation film substrate material is made of single crystal silicon material, the fourth lens is made of zinc selenide material, and the fifth lens is made of single crystal germanium material.

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