All-silicon carbide cryogenic lens and method of manufacture and application to coaxial four-mirror optical infrared camera

Abstract

The present application relates to a kind of full silicon carbide low temperature lens and manufacturing method and application on coaxial four-reflection optical infrared camera.The full silicon carbide low temperature lens includes primary mirror, secondary mirror, three mirrors, four mirrors;Primary mirror and four mirrors are back-to-back layout and form primary mirror and four mirror structure in structure, namely main four mirrors;Main four mirrors and three mirrors are respectively connected at the two ends of a lens force cylinder, and secondary mirror is connected with the one end of lens force cylinder by secondary mirror support rod assembly;Main four mirrors, secondary mirror, three mirrors, secondary mirror support rod assembly and lens force cylinder adopt silicon carbide material.Full silicon carbide lens structure is overall shrinked in low temperature environment, realizes the athermal design of lens optical machine, improves the low temperature stability and adaptability of lens.Lens force cylinder improves the rigidity and stability of lens structure, as low temperature cold screen, suppresses external stray light, improves the signal-to-noise ratio of lens.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-temperature infrared camera, in particular to a full silicon carbide low-temperature lens, a manufacturing method and an application in a coaxial four-mirror optical infrared camera. BACKGROUND

[0002] With the continuous development of science and technology, there are more and more demands for high-sensitivity infrared imaging in the fields of national defense and military, weather observation, commercial remote sensing, etc. In order to realize high-sensitivity detection, reducing the temperature of the lens is one of the important technical means. In the low-temperature lens, the coaxial four-mirror optical system has the advantages of structural symmetry, compact structure, large field of view of the optical system, no chromatic aberration, refractive index influence, and multiple design parameters. The athermal design of the low-temperature lens can reduce the complexity of the system. It avoids the lens from being adjusted at room temperature, and the performance of the low-temperature environment system changes greatly. In addition, the maturity of the silicon carbide 3D printing technology provides support for efficient manufacturing of complex silicon carbide structures.

[0003] At present, the Chinese patent application publication (publication number: CN102338922A) discloses a full aluminum low-temperature full reflection lens. In order to solve the problem of image quality degradation caused by the difference between the environment during lens processing and adjustment and the working environment during use, the lens adopts a full reflection optical system, and the optical system and the support frame supporting the optical system adopt 6061 aluminum. As the lens mirror material, the specific stiffness of aluminum material is small, and in order to ensure the mirror surface accuracy and the structural stiffness of the lens, it is difficult to realize the high lightweight of the lens. The aluminum material is relatively soft, and it is difficult to realize high-precision machining of large-aperture mirrors. As a structural material, its material stiffness is low, the thermal expansion coefficient is large, and the structural thermal deformation is large. In order to ensure the relative position of the mirror, it is difficult to realize a high lightweight structure. The primary mirror, the secondary mirror, the third mirror and the fourth mirror are connected with the primary support frame, the secondary mirror support frame and the third mirror support frame by bolts. This rigid connection has very high requirements for the interface flatness. The assembly stress caused by the size accuracy and the shape and position tolerance of the mounting interface is easy to cause the mirror surface accuracy to degrade. The lens structure requires high temperature uniformity, and the thermal stress caused by the temperature difference of the lens will also cause the mirror surface accuracy to degrade and the lens optical performance to decline. SUMMARY

[0004] The purpose of the present application is to provide a full silicon carbide low-temperature lens, a manufacturing method and an application in a coaxial four-mirror optical infrared camera, which mainly solves the technical problems of the current low-temperature aluminum lens, such as low structural stiffness, difficulty in realizing high-precision large-aperture mirror surface, large structural deformation, high requirements for temperature uniformity and mounting precision, and unsuitable for batch processing.

[0005] In order to achieve the above purpose, the technical scheme of the present application is:

[0006] The application discloses a full-carbon-silicon low-temperature lens which comprises a primary mirror, a secondary mirror, a third mirror and a fourth mirror.

[0007] The full-carbon-silicon low-temperature lens comprises

[0008] a primary mirror, a fourth mirror, a primary-four-mirror common support ring and a primary-four-mirror support;

[0009] a secondary mirror assembly which comprises a secondary mirror, a secondary mirror support ring and a secondary mirror adapter;

[0010] a third mirror assembly which comprises a third mirror and a third mirror support ring;

[0011] a secondary mirror support rod assembly which comprises a secondary mirror mounting flange, a secondary mirror support rod and a support rod joint;

[0012] a lens force-bearing cylinder assembly which comprises a lens force-bearing cylinder and a force-bearing cylinder support;

[0013] The primary mirror, the secondary mirror, the third mirror, the fourth mirror, the secondary mirror mounting flange, the secondary mirror support rod, the support rod joint and the lens force-bearing cylinder are all made of carbonized silicon, and the mirrors and structural parts made of carbonized silicon are all subjected to lightweight treatment; the primary-four-mirror common support ring, the secondary mirror support ring and the third mirror support ring are made of invar steel which matches the thermal expansion coefficient of carbonized silicon.

[0014] The primary-four-mirror common support ring has three support mirror surfaces which are evenly distributed at the periphery of the primary-four-mirror common support ring at an angle of 120 degrees; the primary-four-mirror common support ring has three flexible support structures which are evenly distributed at the inner side of the primary-four-mirror common support ring at an angle of 120 degrees; the outer side of the primary-four-mirror common support ring has three mounting surfaces which are evenly distributed at the outer side of the primary-four-mirror common support ring at an angle of 120 degrees; the flexible support structures and the primary-four-mirror common support mirror surfaces are cemented by epoxy glue; the primary-four-mirror common support mounting surfaces and the primary-four-mirror support are connected by bolts; the included angle between the primary-four-mirror common support ring mounting surface and the adjacent flexible support structure is 60 degrees; and the primary-four-mirror support and the lens force-bearing cylinder are connected by bolts.

[0015] The full silicon carbide low-temperature lens, characterized in that: the inner side of the secondary mirror support ring in the secondary mirror assembly has a flexible support structure, and the three flexible support structures are evenly distributed at an interval of 120 degrees on the inner side of the secondary mirror support ring; the upper surface of the secondary mirror support ring has three secondary mirror support ring mounting surfaces for bolt connection with the secondary mirror adapter, and the three secondary mirror support ring mounting surfaces are evenly distributed at an interval of 120 degrees on the upper surface of the secondary mirror support ring; the lower surface of the secondary mirror adapter has three adapter mounting surfaces for bolt connection with the secondary mirror support ring; the upper surface of the secondary mirror adapter is bolted to the secondary mirror mounting flange through a pressing block, and the pressing block is evenly distributed at an interval of 120 degrees on the secondary mirror adapter; the secondary mirror mounting flange further comprises a secondary mirror mounting flange cementing surface, and the secondary mirror mounting flange cementing surface is cemented with the upper end of the secondary mirror support rod by using epoxy glue; the secondary mirror support ring flexible support structure is cemented with the secondary mirror by using epoxy glue; and the bolt connection parts in the secondary mirror assembly are connected by bolts.

[0016] The full silicon carbide low-temperature lens, characterized in that: the three support rod joints in the secondary mirror support rod assembly are evenly distributed at an interval of 120 degrees on the lens force bearing cylinder; the support rod joint comprises a support rod joint mounting surface and a support rod joint cementing surface; the support rod joint mounting surface is connected to the lens force bearing cylinder by a bolt; and the support rod joint cementing surface is cemented with the lower end of the secondary mirror support rod by using epoxy glue.

[0017] The full silicon carbide low-temperature lens, characterized in that: the three mirror support ring comprises three three mirror support ring flexible support structures and three three mirror support ring mounting surfaces; the three three mirror support ring flexible support structures are evenly distributed at an interval of 120 degrees on the inner side of the three mirror support ring; the three three mirror support ring mounting surfaces are evenly distributed at an interval of 120 degrees on the outer side of the three mirror support ring; the included angle between the three mirror support ring flexible support structure and the adjacent three mirror support ring mounting surface is 60 degrees; the three mirror support ring flexible support structure is cemented with the three mirror by using epoxy glue; and the three mirror support ring mounting surface is bolted to the bearing cylinder mounting surface by a bolt.

[0018] The full silicon carbide low-temperature lens, characterized in that: the lens force bearing cylinder comprises a first mounting surface connected to the main four mirror support, a second mounting surface connected to the support rod joint, a third mounting surface connected to the three mirror support ring, and a fourth mounting surface connected to the force bearing cylinder support; and the fourth mounting surface is connected to the force bearing cylinder support by a bolt.

[0019] A manufacturing method of the full silicon carbide low-temperature lens, characterized in that: the main four mirror, the secondary mirror, the three mirror, the secondary mirror support rod assembly, and the lens force bearing cylinder are made by 3D printing of silicon carbide.

[0020] The full silicon carbide low-temperature lens is applied to a coaxial four-mirror optical infrared camera.

[0021] In view of the above technical features, the present application has the following advantages:

[0022] 1、The present application adopts low-density, high-modulus, low-expansion coefficient and high-thermal-conductivity silicon carbide material for the mirror and lens structure, which improves the rigidity and lightweight ratio of the lens, reduces the structural thermal deformation and improves the structural temperature uniformity while realizing the athermalization of the optical system.

[0023] 2、The main four mirrors in the present application adopt a double-sided common body structure and a common support mode, which reduces the number of mirror supports, improves the compactness of the structure and reduces the weight of the lens.

[0024] 3、In the present application, the main four mirrors, the secondary mirror and the three mirrors are all supported by a support ring in the circumferential direction, which reduces the length of the lens in the direction and improves the compactness of the structure. The flexible support structure of the support ring reduces the influence of assembly stress and thermal stress on the mirror surface and improves the adaptability of the lens.

[0025] 4、In the present application, the mirror and the support ring are glued together by epoxy glue, which reduces the requirement for the installation plane precision between the mirror and the mirror support, improves the assembly efficiency and is suitable for mass assembly.

[0026] 6、In the present application, the main load-bearing structure of the lens adopts a load-bearing cylinder configuration, which improves the stability and rigidity of the lens structure. At the same time, the load-bearing cylinder acts as a cold screen, and the inside can be designed with a stray light suppression structure to avoid stray light entering the inside of the optical path through the three mirrors and the four mirrors, and the stray light suppression effect is good.

[0027] 7、In the present application, the silicon carbide structure of the lens is processed by 3D printing, which can adapt to more complex part structure forms. It realizes higher lightweight ratio and higher structural rigidity of the lens, improves the production efficiency and is suitable for mass processing. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the overall structure schematic diagram of the full-silicon carbide low-temperature lens of the coaxial four-mirror optical infrared camera of the present application.

[0029] Figure 2 is the structure schematic diagram of the main four mirrors in the present application.

[0030] Figure 3 is the structure schematic diagram of the main four mirror assembly in the present application.

[0031] Figure 4 is the structure schematic diagram of the secondary mirror assembly in the present application.

[0032] Figure 5 is the structure schematic diagram of the three-mirror assembly in the present application.

[0033] Figure 6It is a connection structure diagram of the lens force cylinder in the application.

[0034] Figure 7 It is a light path structure diagram of the full carbonized silicon low temperature lens of the coaxial four-mirror optical infrared camera in the application. DETAILED DESCRIPTION

[0035] The application will be further described below in connection with specific embodiments. It should be understood that these embodiments are only used to explain the application and not used to limit the scope of the application. Furthermore, it should be understood that after reading the content of the application, those skilled in the art can make various modifications or changes to the application, and these equivalent forms also fall within the scope of the appended claims of the application.

[0036] Please refer to Figures 1-7 The application discloses a preferred embodiment of a full carbonized silicon low temperature lens of a coaxial four-mirror optical infrared camera. As shown in the figure, it comprises:

[0037] A main four-mirror assembly, the main four-mirror assembly comprising a main mirror 1, a four-mirror 4, a main four-mirror common support ring 5, a main four-mirror support 9;

[0038] A secondary mirror assembly, the secondary mirror assembly comprising a secondary mirror 2, a secondary mirror support ring 6, a secondary mirror adapter 15;

[0039] A three-mirror assembly, the three-mirror assembly comprising a three-mirror 3, a three-mirror support ring 7;

[0040] A secondary mirror support rod assembly, the secondary mirror support rod assembly comprising a secondary mirror mounting flange 10, a secondary mirror support rod 11, a support rod joint 12;

[0041] A lens force cylinder assembly, the lens force cylinder assembly comprising a lens force cylinder 8, a force cylinder support 13.

[0042] Among them, the main mirror 1, the secondary mirror 2, the three-mirror 3, the four-mirror 4, the secondary mirror support rod assembly (that is, the secondary mirror mounting flange 10, the secondary mirror support rod 11, the support rod joint 12), and the lens force cylinder 8 are all made of silicon carbide material, and the mirrors and structural parts made of silicon carbide are all subjected to lightweight treatment; each mirror body support ring (that is, the main four-mirror common support ring 5, the secondary mirror support ring 6, and the three-mirror support ring 7) is made of a steel material matched with the thermal expansion coefficient of silicon carbide.

[0043] As a further introduction of the embodiment, as Figure 2 The main mirror 1 and the four-mirror 4 in the main four-mirror assembly adopt a back-to-back layout, and are designed as a common body structure in structure, and are combined into a main four-mirror 14; the periphery of the main four-mirror 14 is provided with a main four-mirror common support mirror surface 1401 for connection, and three support mirror surfaces 1401 are evenly distributed at 120° on the periphery of the main four-mirror 14. As Figure 3The main four-mirror common support ring 5 has flexible support structures 501 on the inner side, and the three flexible support structures 501 are evenly distributed on the inner side of the main four-mirror common support ring 5 at an angle of 120°. The main four-mirror common support ring 5 has three mounting surfaces 502 on the outer side, which are bolted to the main four-mirror support 9, and the three mounting surfaces 502 are evenly distributed on the outer side of the main four-mirror common support ring 5 at an angle of 120°. The flexible support structures 501 and the main four-mirror common support mirror surface 1401 are glued together using epoxy glue, and the thickness of the epoxy glue is 0.15 mm. The main four-mirror common support mounting surface 502 and the main four-mirror support 9 are connected by M5 bolts, and the angle between the main four-mirror common support ring mounting surface 502 and the adjacent flexible support structure 501 is 60°. The main four-mirror support 9 and the lens force cylinder 801 are connected by four M5 bolts.

[0044] As a further introduction to this embodiment, as shown in Figure 4 , the secondary mirror support ring 6 has flexible support structures 601 on the inner side, and the three flexible support structures 601 are evenly distributed on the inner side of the secondary mirror support ring 6 at an angle of 120°. The upper surface of the secondary mirror support ring 6 has three secondary mirror support ring mounting surfaces 602, which are bolted to the secondary mirror adapter 15, and the three secondary mirror support ring mounting surfaces 602 are evenly distributed on the upper surface of the secondary mirror support ring 6 at an angle of 120°. The lower surface of the secondary mirror adapter 15 has three adapter mounting surfaces 1502, which are bolted to the secondary mirror support ring 6; the upper surface of the secondary mirror adapter 15 is bolted to the secondary mirror mounting flange 10 through a pressing block 1501, and the pressing block 1501 is evenly distributed on the secondary mirror adapter 15 at an angle of 120°. The secondary mirror mounting flange 10 also includes a secondary mirror mounting flange gluing surface 1001, which is glued to the upper end of the secondary mirror support rod 11 using epoxy glue. The secondary mirror support ring flexible support structure 601 and the secondary mirror 2 are glued together using epoxy glue, and the thickness of the epoxy glue is 0.15 mm; the bolted parts in the secondary mirror assembly are connected by M4 bolts.

[0045] As a further introduction to this embodiment, as shown in Figure 1 , the three support rod joints 12 are evenly distributed on the lens force cylinder 8 at an angle of 120°; the support rod joint 12 includes a support rod joint mounting surface 1201 and a support rod joint gluing surface 1202. The support rod joint mounting surface 1201 and the lens force cylinder 8 are connected by two M5 bolts; the support rod joint gluing surface 1202 and the lower end of the secondary mirror support rod are glued together using epoxy glue.

[0046] As a further introduction to this embodiment, as shown in Figure 5 , the three-mirror support ring 7 includes three three-mirror support ring flexible support structures 701 and three three-mirror support ring mounting surfaces 702.

[0047] The three three-mirror support ring flexible support structures 701 are evenly distributed at 120° inside the three-mirror support ring 7; the three three-mirror support ring mounting surfaces 702 are evenly distributed at 120° outside the three-mirror support ring; the included angle between the support structure 701 and the adjacent mounting surface 702 is 60°;

[0048] The three-mirror support ring flexible support structure 701 is glued with the three-mirror 3 by using epoxy glue; the thickness of the epoxy glue is 0.15 mm; the three-mirror support ring mounting surface 702 is bolted with the force cylinder mounting surface 803 by using M5 bolts.

[0049] As a further introduction of the present embodiment, as Figure 6 The lens force cylinder 8 comprises a first mounting surface 801 connected with the main four-mirror support 9; a second mounting surface 802 connected with the support rod joint 12; a third mounting surface 803 connected with the three-mirror support ring 7; a fourth mounting surface 804 connected with the force cylinder support 13; the fourth mounting surface 804 is connected with the force cylinder support 13 by using four M5 bolts;

[0050] In the above technical solution, the present application provides a non-thermal full-carbide silicon low-temperature lens for a coaxial four-mirror optical infrared camera, which has the following beneficial effects:

[0051] The full-carbide silicon lens structure can be contracted as a whole in a low-temperature environment, realizes the non-thermal design of the lens optical machine, and improves the low-temperature stability and adaptability of the lens. In a 150K environment, the deformation RMS value of each mirror surface is better than 6nm.

[0052] The low-temperature lens of the present application, the mirrors, the secondary mirror support rod assembly for controlling the distance between the mirrors, and the lens force cylinder assembly are all made of lightweight, low-expansion coefficient, high-rigidity, and high-thermal-conductivity carbide silicon material. Each carbide silicon structure is made by using carbide silicon 3D printing, which reduces the manufacturing difficulty of complex structures and improves the production efficiency, and is suitable for mass production. Higher structural rigidity and lightweight rate, better temperature uniformity, and larger aperture mirror surface precision are realized. The flexible support structure of the support ring reduces the influence of assembly stress and thermal stress on the mirror surface, improves the lens adaptability, and in the gravity working condition, the deformation RMS of each mirror surface in the radial and axial directions is better than 3nm. Compared with the commonly used aluminum material, the full-carbide silicon lens can realize higher structural rigidity and lightweight rate, better temperature uniformity, and larger aperture mirror surface precision. The full-carbide silicon lens structure can be contracted as a whole in a low-temperature environment, realizes the non-thermal design of the lens optical machine, and improves the low-temperature stability and adaptability of the lens. The lens force cylinder improves the structural rigidity and stability of the lens, suppresses external stray light as a low-temperature cold screen, and improves the signal-to-noise ratio of the lens.

[0053] The above merely describes preferred embodiments of the present application, and is not intended to limit the patent scope of the present application, and any equivalent structure or equivalent process conversion made by using the content of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A cryogenic lens made entirely of silicon carbide, comprising a primary lens, a secondary lens, a tertiary lens, and a fourth lens; characterized in that: The primary lens and four lenses are arranged back-to-back and structurally form a common structure of the primary lens and four lenses, namely the primary four lenses; the primary four lenses and the three lenses are respectively connected to both ends of a lens support cylinder, and the secondary lens is connected to the end of the lens support cylinder on which the primary four lenses are set through the secondary lens support rod assembly; the primary four lenses, secondary lenses, three lenses, secondary lens support rod assembly and lens support cylinder are made of silicon carbide material; The all-silicon carbide cryogenic lens includes The main four-lens assembly includes a main lens, four lenses, a common support ring for the main four lenses, and a support member for the main four lenses; The secondary mirror assembly includes a secondary mirror, a secondary mirror support ring, and a secondary mirror adapter. The three-mirror assembly includes three mirrors and a three-mirror support ring. The secondary mirror support rod assembly includes a secondary mirror mounting flange, a secondary mirror support rod, and a support rod connector. A lens support cylinder assembly, comprising a lens support cylinder and a support cylinder component; Among them, the primary mirror, secondary mirror, tertiary mirror, quaternary mirror, secondary mirror mounting flange, secondary mirror support rod, support rod joint, and lens bearing cylinder are all made of silicon carbide. All silicon carbide-manufactured mirrors and structural parts have undergone lightweight treatment. The primary four-mirror common support ring, secondary mirror support ring, and tertiary mirror support ring are made of Invar steel material that matches the thermal expansion coefficient of silicon carbide.

2. The all-silicon carbide low-temperature lens according to claim 1, characterized in that: The periphery of the four main mirrors is provided with a common support mirror surface for connection, with three support mirror surfaces evenly distributed at 120° around the periphery of the four main mirrors; the inner side of the common support ring of the four main mirrors has a flexible support structure, with three flexible support structures evenly distributed at 120° on the inner side of the common support ring of the four main mirrors; the outer side of the common support ring of the four main mirrors has three mounting surfaces that are bolted to the support components of the four main mirrors, with the three mounting surfaces evenly distributed at 120° on the outer side of the common support ring of the four main mirrors; the flexible support structure and the common support mirror surface of the four main mirrors are bonded with epoxy adhesive; The main four-lens common support mounting surface is connected to the main four-lens support component by bolts, and the angle between the main four-lens common support ring mounting surface and the adjacent flexible support structure is 60°; the main four-lens support component is connected to the lens load-bearing cylinder by bolts.

3. The all-silicon carbide low-temperature lens according to claim 1, characterized in that: The secondary mirror assembly has a flexible support structure on the inner side of the secondary mirror support ring, with three flexible support structures evenly distributed at 120° intervals on the inner side of the secondary mirror support ring. The upper surface of the secondary mirror support ring has three mounting surfaces that are bolted to the secondary mirror adapter, and these three mounting surfaces are evenly distributed at 120° intervals on the upper surface of the secondary mirror support ring. The lower surface of the secondary mirror adapter has three mounting surfaces that are bolted to the secondary mirror support ring. The upper surface of the secondary mirror adapter is bolted to the secondary mirror mounting flange via pressure blocks, which are evenly distributed at 120° intervals on the secondary mirror adapter. The secondary mirror mounting flange also includes a secondary mirror mounting flange adhesive surface, which is bonded to the upper end of the secondary mirror support rod with epoxy adhesive. The flexible support structure of the secondary mirror support ring is bonded to the secondary mirror with epoxy adhesive. All bolted connections in the secondary mirror assembly are made using bolts.

4. The all-silicon carbide low-temperature lens according to claim 1, characterized in that: In the secondary lens support rod assembly, three support rod joints are evenly distributed at 120° on the lens support cylinder; each support rod joint includes a support rod joint mounting surface and a support rod joint bonding surface; the support rod joint mounting surface is connected to the lens support cylinder by bolts; and the support rod joint bonding surface is bonded to the lower end of the secondary lens support rod with epoxy adhesive.

5. The all-silicon carbide low-temperature lens according to claim 1, characterized in that: The three-mirror support ring includes three flexible support structures and three mounting surfaces. The three flexible support structures are evenly distributed at 120° intervals on the inner side of the three-mirror support ring. The three mounting surfaces are evenly distributed at 120° intervals on the outer side of the three-mirror support ring. The angle between the flexible support structure and the adjacent mounting surface is 60°. The flexible support structure is bonded to the three mirrors with epoxy adhesive. The mounting surfaces are bolted to the mounting surfaces of the load-bearing cylinder.

6. The all-silicon carbide low-temperature lens according to claim 1, characterized in that: The lens support cylinder includes a first mounting surface connected to the main four-lens support component; a second mounting surface connected to the support rod connector; and a third mounting surface connected to the three-lens support ring. A fourth mounting surface connected to the load-bearing cylinder support; the fourth mounting surface is connected to the load-bearing cylinder support by bolts.

7. A method for manufacturing an all-silicon carbide cryogenic lens as described in claim 1, 2, 3, 4, 5, or 6, characterized in that: The main four-lens, secondary lens, third lens, secondary lens support rod assembly, and lens support cylinder are manufactured using silicon carbide 3D printing.

8. A fully silicon carbide cryogenic lens as described in claim 1, 2, 3, 4, 5, or 6, applied to a coaxial quad-reflector optical infrared camera.

Images