A support structure between a primary mirror and a secondary mirror

Abstract

This invention proposes a support structure between a primary mirror and a secondary mirror, belonging to the technical field of optical-mechanical structures for space remote sensing cameras. This structure, referred to as a central cylinder, has one end connected to the secondary mirror and the other end passing through the central hole of the primary mirror and connected to the main support structure of the camera. The central cylinder includes a secondary mirror connecting ring, a support rod, a cylindrical portion, and another support ring connected in sequence. The secondary mirror connecting ring connects to the secondary mirror. The support rod extends along the axis of the secondary mirror connecting ring and connects the secondary mirror connecting ring and the cylindrical portion. The support ring passes through the central hole of the primary mirror and connects to the main support structure of the camera. This structure simplifies the structural form and organically combines the support structure with the thermal control structure and the stray light elimination structure. It solves the technical problems of high temperature gradient requirements, large size, heavy weight, high thermal control resource consumption, and difficulty in stray light elimination in the support structure between the primary and secondary mirrors.

Description

Technical Field

[0001] This invention belongs to the technical field of optical-mechanical structures for space remote sensing cameras. Using this structure can effectively reduce the connection weight between the primary and secondary mirrors, achieving the goals of stray light elimination, ultra-lightweight design, and ultra-stability design. Background Technology

[0002] Space optical cameras typically employ a three-mirror aberration-correcting optical system. Light first enters the primary mirror 11, then reflects onto the secondary mirror 12, and finally reflects again onto the third mirror. After reflection by the three mirrors, the light converges to the focal plane. The positional accuracy and temperature stability requirements between the primary mirror 11 and the secondary mirror 12 of a space remote sensing camera are extremely high. Traditionally, a structural cylinder 1 with a diameter larger than that of the primary mirror 11 is used between the primary mirror 11 and the secondary mirror 12. The secondary mirror 12 is connected to the outside of the structural cylinder 1 via three radially supporting rods 13. Figure 1 As shown.

[0003] The support structure employing a cylindrical structure and three radial support rods minimizes the obstruction of incident light. To ensure temperature stability between the primary and secondary mirrors, precise temperature control is typically applied to the cylindrical structure and the three radial support rods. While this structure reduces obstruction, it results in a large space and weight for the support structure between the primary and secondary mirrors, requires significant thermal control resources, and exhibits a large temperature gradient, leading to structural instability. If external heat pipes and multi-layered thermal control are added to the three support rods of the secondary mirror, the overall size of the support structure will increase exponentially, and the optical obstruction will also increase significantly. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of existing technologies and provide a support structure between the primary and secondary mirrors, simplifying the structural form and organically combining the support structure with the thermal control structure. This will solve the technical problems of high stability, large size, heavy weight, and high thermal control resource consumption in the support structure between the primary and secondary mirrors.

[0005] The technical solution of this invention is:

[0006] A support structure between a primary mirror and a secondary mirror includes a central tube, one end of which is connected to the secondary mirror, and the other end of which is connected to the main support structure of the camera through a central hole passing through the primary mirror.

[0007] The central cylinder includes a secondary mirror connecting ring, a support rod, a cylindrical part, and a support ring connected in sequence. The secondary mirror connecting ring is used to connect the secondary mirror. The support rod extends along the axis of the secondary mirror connecting ring and connects the secondary mirror connecting ring and the cylindrical part. The support ring passes through the central hole of the primary mirror and connects to the main support structure of the camera.

[0008] Three support rods are provided, and the three support rods are evenly distributed at 120° around the circumference of the support ring.

[0009] The support rod, the secondary mirror connecting ring, the cylindrical part, and the support ring are all provided with interconnected capillary channels. The capillary channels are filled with liquid ammonia and the ends of the capillary channels are sealed.

[0010] The capillary channels are distributed along the axial direction of the cylindrical portion.

[0011] The inner wall of the cylindrical part is connected to a light barrier, which is circular and used to block stray light outside the field of view.

[0012] The secondary mirror connecting ring includes a circular ring portion and a conical cylindrical portion. The smaller diameter end of the conical cylindrical portion is connected to the outer edge of the circular ring portion, and the larger diameter end of the conical cylindrical portion is located on the side of the circular ring portion facing the cylindrical portion. One end of the support rod is connected to both the circular ring portion and the side of the conical cylindrical portion facing the cylindrical portion, and the other end of the support rod is connected to the outer wall of the cylindrical portion. Along the direction close to the support ring, the outer side of the end of the support rod gradually approaches the outer surface of the cylindrical portion.

[0013] The central cylinder is formed by integral 3D printing.

[0014] The central cylinder is made of SiC, invar, aluminum alloy, or titanium alloy.

[0015] The maximum outer diameter of the rotating body formed by the support rod of the central cylinder is D3, the outer diameter of the cylindrical part is D2, the distance between the cylindrical part and the secondary mirror connecting ring is L, and the thickness of the support rod is t. D3, D2, L, and t satisfy the following relationship:

[0016] t≤μπr / 3

[0017]

[0018] The inner diameter of the cylindrical part is D1, which should be greater than the maximum radius of the light cone reflected back by the secondary mirror, and D2 should not block the light rays reflected by the primary mirror to reach the secondary mirror.

[0019] In summary, this application includes at least the following beneficial technical effects:

[0020] This invention simplifies the support structure between primary and secondary mirrors, achieving an organic integration of the support and thermal control structures, reducing structural weight and thermal control design power consumption. It has wide applications in the connection between primary and secondary mirrors in space optical remote sensors. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a traditional support structure in the background art;

[0022] Figure 2 This is a schematic diagram of the structure of the central cylinder in an embodiment of this application, wherein... Figure 2 a is an external view of the central cylinder. Figure 2 b is a sectional view of the central cylinder;

[0023] Figure 3 Here is a structural diagram of the central cylinder;

[0024] Figure 4 Determining the main dimensions of the central cylinder;

[0025] Figure 5 These are the design parameters for the central cylinder.

[0026] Explanation of reference numerals in the attached drawings: 1. Structural tube; 11. Primary mirror; 12. Secondary mirror; 13. Three radial support rods;

[0027] 2. Secondary lens connecting ring; 21. Circular ring part; 22. Conical part; 3. Support rod; 31. Capillary channel; 4. Circular part; 41. Aperture stop; 5. Support ring; 6. Camera main support structure. Detailed Implementation

[0028] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0029] This application discloses a support structure between a primary mirror and a secondary mirror, such as... Figure 2 As shown in Figure a, the camera includes a central tube, with the primary mirror 11 and secondary mirror 12 supported by the central tube. The central tube passes through the central hole of the primary mirror 11 and is connected to the main support structure 6 of the camera.

[0030] The central tube structure is as follows: Figure 2 As shown in a and b, the central cylinder includes a secondary mirror connecting ring 2, a support rod 3, a cylindrical portion 4, and a support ring 5. All parts of the central cylinder are integrally 3D printed. The secondary mirror connecting ring 2 is used to connect to the secondary mirror 12 and provide support for it. The support rod 3 connects the secondary mirror connecting ring 2 to the cylindrical portion 4, extending along the axial direction of the secondary mirror connecting ring 2. The support ring 5 is connected to the end of the cylindrical portion 4 away from the secondary mirror connecting ring 2, and passes through the central hole of the primary mirror 11 to connect to the camera's main support structure 6. Three support rods 3 are provided, connecting the support ring 5 and the secondary mirror connecting ring 2. The three support rods 3 are evenly distributed at 120° intervals around the circumference of the support ring 5. The central cylinder is integrally printed. Connecting capillary channels 31 are printed inside the support rod 3, secondary mirror connecting ring 2, cylindrical section 4, and support ring 5. These capillary channels 31 are distributed along the axial direction of the cylindrical section 4. Liquid ammonia is filled inside the capillary channels 31, and the ends of the capillary channels 31 are sealed to form capillary tubes. When there is a temperature difference at different locations within the central cylinder, the internal capillary tubes will activate, maintaining the central cylinder temperature at a uniform level. An aperture stop 41, which is annular, is connected to the inner wall of the cylindrical section 4 to block stray light outside the field of view.

[0031] Compared to the traditional three-bar support scheme of the front mirror barrel and secondary mirror 12, where the radial support rods 13 block light before it enters the primary mirror 11, the central tube of this application blocks the light converging from the primary mirror 11 to the secondary mirror 12. The blocking position is after the light is reflected by the primary mirror 11. The central tube is generally made of SiC, Invar, aluminum alloy, or titanium alloy. The heat pipe is pre-embedded inside the support structure through 3D printing, reducing the size and weight of the thermal control system of the support structure, lowering the temperature gradient of the support structure, and achieving better thermal stability.

[0032] With the above structure, the main functions of the central tube are as follows: 1) to provide support for the secondary mirror 12; 2) to maintain thermal stability between the primary and secondary mirrors 12; and 3) to eliminate stray light outside the field of view.

[0033] The secondary mirror connecting ring 2 includes a circular ring portion 21 and a conical portion 22. The smaller diameter end of the conical portion is connected to the outer edge of the circular ring portion, and the larger diameter end of the conical portion is located on the side of the circular ring portion facing the cylindrical portion 4. One end of the support rod 3 is connected to both the circular ring portion and the side of the conical portion facing the cylindrical portion 4, and the other end of the support rod 3 is connected to the outer wall of the cylindrical portion 4. Along the direction close to the support ring 5, the outer side of the end of the support rod 3 gradually approaches the outer surface of the cylindrical portion 4. The provision of the secondary mirror connecting ring 2 improves the stability of the connection between the support rod 3 and the secondary mirror connecting ring 2.

[0034] The supporting structure between the primary and secondary mirrors 12 has the following main innovations:

[0035] 1) The secondary mirror 12 support structure (center tube) is connected to the main camera structure through the center hole of the primary mirror 11, thus supporting and fixing the secondary mirror 12 structure. The structure is small in size, simple in form, lightweight, high in frequency, and has good structural rigidity.

[0036] 2) The internal support structure (central cylinder) of secondary mirror 12 incorporates 3D-printed pre-embedded heat pipes, achieving an organic integration between the heat pipes and the support structure. This saves weight on thermal control components, reduces the temperature gradient at the center, and achieves high structural stability.

[0037] 3) The secondary mirror 12 support structure (center tube) is equipped with a stray light blocking aperture 41 to block stray light outside the field of view.

[0038] The structure between the primary lens 11 and the secondary lens 12 has a significant impact on the stability and rigidity of the camera, and is a key structure in the camera.

[0039] The installation and connection method of the center cylinder is as follows: Figure 3As shown. The secondary mirror 12 is mounted on the secondary mirror connecting ring 2 of the central tube. The secondary mirror connecting ring 2 not only provides support but also blocks stray light from other fields of view. The support ring 5 of the central tube passes through the central hole of the primary mirror 11 and connects to the main structure of the camera. Light rays reaching the primary mirror 11 from the light entrance are reflected and pass through the gap between the three support rods 3 of the central tube to reach the secondary mirror 12. The light rays reflected from the secondary mirror 12 pass through the cylindrical part 4 of the central tube and the support ring 5 to reach other reflecting mirrors or image planes connected to the main support structure 6 of the camera.

[0040] like Figure 4 and Figure 5 a, Figure 5 b, the mass of the secondary mirror 12 is m, the radius of the secondary mirror 12 is r, the required support frequency is f, the required blocking ratio is μ, and the design of the central tube mainly involves five parameters: D1, D2, D3, L, and t. D3 is the maximum outer diameter of the rotating body formed by the three support rods 3 of the central tube; D2 is the outer diameter of the cylindrical part 4; D1 is the inner diameter of the cylindrical part 4; L is the distance between the cylindrical part 4 and the secondary mirror connecting ring 2; t is the thickness of the support rod 3; D1 + thickness of the cylindrical part 4 = D2. Among them, D1, D2, and L depend on the optical system, L should be as long as possible, and D1 should be greater than the maximum light cone radius reflected back into the cylindrical part (4) by the secondary mirror 12. Figure 4 Ray 1 refers to the ray that enters from the edge of the primary mirror, is reflected by the primary mirror to the secondary mirror, and then reflected again by the secondary mirror into the cylindrical section. Specifically, this refers to the third section of pipe 1 – the ray reflected by the secondary mirror into the cylindrical section. D2 should not block the ray emanating from the edge of D3 (ray 2 refers to the ray that enters from the outside of support rod 3, is reflected by the primary mirror to reach secondary mirror 12). Figure 4 As shown. Under the premise that the mass of mirror 12 is m, the required support frequency is f, and the obstruction ratio is not less than μ.

[0041] D3, D2, L, and t should satisfy the following relationship

[0042] t≤μπr / 3 (1)

[0043]

[0044] After determining the parameters, a capillary tube is printed inside the central cylinder using 3D printing. The inside is filled with ammonia working fluid and sealed. The size of the internal aperture is determined according to the position of the incident light.

[0045] The characteristics of the central tube are:

[0046] The center tube passes through the center hole of the primary lens to support the camera;

[0047] The central cylinder adopts a three-support rod structure along the axis, with the three support rods distributed at 120°.

[0048] The parameters of the central cylinder are designed to meet the requirements of equations (1) and (2);

[0049] The inner part of the central cylinder is 3D printed with interconnected capillaries and filled with working fluid to ensure temperature uniformity.

[0050] An anti-stray light baffle is installed inside the central tube to block stray light from outside the field of view.

[0051] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A support structure between a primary mirror and a secondary mirror, characterized in that: It includes a central tube, one end of which is connected to the secondary mirror (12), and the other end is connected to the camera main support structure (6) through the central hole of the primary mirror (11); The central cylinder includes a secondary mirror connecting ring (2), a support rod (3), a cylindrical part (4), and a support ring (5) connected in sequence. The secondary mirror connecting ring (2) is used to connect the secondary mirror (12). The support rod (3) extends along the axial direction of the secondary mirror connecting ring (2) and connects the secondary mirror connecting ring (2) and the cylindrical part (4). The support ring (5) passes through the central hole of the primary mirror (11) and connects to the main support structure (6) of the camera. The maximum outer diameter of the rotating body formed by the support rod (3) of the central cylinder is D3, the outer diameter of the cylindrical part (4) is D2, the distance between the cylindrical part (4) and the secondary mirror connecting ring (2) is L, and the thickness of the support rod (3) is t. D3, D2, L and t satisfy the following relationship t≤μπr / 3 ≥f In the formula, m is the mass of the secondary mirror (12), r is the radius of the secondary mirror (12), f is the required support frequency, and μ is the required blocking ratio; The inner diameter of the cylindrical part (4) is D1, which should be greater than the radius of the light cone reflected back by the secondary mirror (12) when entering the cylindrical part (4), and D2 should not block the light rays reflected by the primary mirror (11) to reach the secondary mirror (12).

2. The support structure between the primary mirror and the secondary mirror according to claim 1, characterized in that: The support rods (3) are provided in three positions, and the three support rods (3) are evenly distributed at 120° around the circumference of the support ring (5).

3. The support structure between the primary mirror and the secondary mirror according to claim 1, characterized in that: The support rod (3), the secondary mirror connecting ring (2), the cylindrical part (4) and the support ring (5) are all provided with a connected capillary channel (31). The capillary channel (31) is filled with liquid ammonia and the end of the capillary channel (31) is sealed.

4. The support structure between the primary mirror and the secondary mirror according to claim 3, characterized in that: The capillary channels (31) are distributed along the axial direction of the cylindrical portion (4).

5. The support structure between the primary mirror and the secondary mirror according to claim 1, characterized in that: The inner wall of the cylindrical part (4) is connected to a light barrier (41), which is annular and used to block stray light outside the field of view.

6. The support structure between the primary mirror and the secondary mirror according to claim 1, characterized in that: The secondary mirror connecting ring (2) includes a circular ring and a conical cylinder. The small-diameter end of the conical cylinder is connected to the outer edge of the circular ring, and the large-diameter end of the conical cylinder is located on the side of the circular ring facing the cylindrical cylinder (4). One end of the support rod (3) is connected to the side of the circular ring and the conical cylinder facing the cylindrical cylinder (4), and the other end of the support rod (3) is connected to the outer wall of the cylindrical cylinder (4). Along the direction close to the support ring (5), the outer side of the end of the support rod (3) gradually approaches the outer surface of the cylindrical cylinder (4).

7. The support structure between the primary mirror and the secondary mirror according to claim 1, characterized in that: The central cylinder is formed by integral 3D printing.

8. The support structure between the primary mirror and the secondary mirror according to claim 1, characterized in that: The central cylinder is made of SiC, invar, aluminum alloy, or titanium alloy.

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