Low-stress mounting structure of optical window

Abstract

The invention discloses a low-stress mounting structure of an optical window. The low-stress mounting structure comprises the optical window, a window inner frame, a window ring, a transition frame and a window outer frame, the lower end of the optical window is hermetically welded with the window inner frame; the upper end of the window is welded with the window ring; the transition frame is welded with the window outer frame and then is in airtight welding with the window inner frame. The stress balance of the upper end face and the lower end face in the optical window welding process guarantees the shape quality of the window after welding, the thin-wall structure of the transition frame is used for conducting physical isolation on the light-weight material of the window outer frame in thermal expansion and cold contraction and structural deformation, and the stress isolation effect of the optical window is achieved.

Description

Technical Field

[0001] This invention relates to the field of vacuum packaging technology for infrared detectors, specifically a low-stress mounting structure for an optical window. Background Technology

[0002] Infrared cameras are the core components of infrared remote sensing instruments, and the fabrication technology of infrared detector components is of great significance in the fields of aerospace and aviation infrared remote sensing. In the development of large-scale infrared detector components, the surface quality of the infrared optical window after hermetically sealed welding is a crucial factor affecting the infrared imaging results. As the scale of infrared detectors increases, the focal plane size of infrared detectors also increases accordingly, leading to a corresponding increase in the optical aperture of infrared components. This poses challenges to controlling the surface quality of the optical window after welding.

[0003] Traditional optical windows typically employ a metal frame structure, embedding the optical window within a metal frame and then achieving hermetic welding using methods such as eutectic bonding or soft metal bonding. However, this approach faces several drawbacks. Firstly, the expansion coefficients of the optical window material and the metal frame material cannot perfectly match. During hermetic welding, residual stress in the frame structure and the optical window will negatively impact the window's shape, leading to increased surface deterioration as the window diameter increases. Secondly, to ensure compatibility with the window material's expansion coefficient, lightweight materials cannot be used for the window frame, affecting the lightweight design of the infrared detector assembly. Considering the high optical imaging quality requirements of infrared detectors for space applications, stringent requirements are placed on the optical specifications of all optical components involved in the infrared camera's optical path. Therefore, the infrared detector assembly requires a low-stress, hermetic welding structure and implementation method for optical windows. This method should satisfy the hermetic sealing requirements of the infrared optical window while reducing residual stress after welding, ensuring the surface quality of the optical window in the infrared detector assembly. Furthermore, stress isolation structures within the window structure allow for the composite application of different materials in the optical window structure, achieving a lightweight design for the infrared detector assembly. Summary of the Invention

[0004] The purpose of this invention is to provide a low-stress mounting structure for an optical window, solving the problems in the prior art where, on the one hand, the expansion coefficients of the optical window material and the metal frame material cannot be perfectly matched, and the residual welding stress between the frame structure and the optical window will have a certain impact on the optical window, with the degree of deterioration of the window surface increasing as the window diameter increases; on the other hand, in order to consider the matching of the expansion coefficients with the window material, lightweight materials cannot be used for the window frame in the component development, making it difficult to achieve lightweight infrared detector components.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A low-stress mounting structure for an optical window includes an inner window frame, a window ring, a transition frame, and an outer window frame that are adapted to the shape of the optical window and are disposed at the edge of the optical window; both the inner window frame and the window ring are provided with openings for the optical window.

[0007] The inner frame of the window includes a vertical frame wall and an inwardly facing mounting platform at the bottom of the frame wall. Its cross-section is L-shaped. The lower edge of the optical window is welded and fixed to the mounting platform. The window ring corresponds to the mounting platform. The window ring is welded and fixed to the upper end of the frame wall of the inner frame of the window and to the upper edge of the optical window. The window ring and the mounting platform clamp and fix the optical window.

[0008] The transition frame is set between the inner frame and the outer frame of the window. The inner side of the transition frame is welded and fixed to the inner frame of the window, and a gap is left between the inner side of the transition frame and the inner frame of the window; the outer side of the transition frame is welded and fixed to the outer frame of the window, and a gap is left between the outer side of the transition frame and the outer frame of the window.

[0009] The transition frame includes an interconnected ring wall, an upper edge, and a lower edge. The upper edge is located at the top of the ring wall and protrudes inward from the ring wall. It is welded and fixed to the upper end of the frame wall of the inner window frame, with a gap between the frame wall and the ring wall. The lower edge is located at the bottom of the ring wall and protrudes outward from the ring wall. It is welded and fixed to the bottom inner side of the outer window frame, with a gap between the ring wall and the outer window frame.

[0010] The wall thickness of the transition frame is 0.1 mm to 0.2 mm.

[0011] The width of the gap between the inner frame wall and the ring wall of the window is 0.5mm to 1mm.

[0012] The material of the inner frame of the window matches the material expansion coefficient of the optical window.

[0013] The material of the window ring is the same as the material of the inner frame of the window.

[0014] The thickness and opening size of the window ring are consistent with the thickness and opening size of the mounting platform.

[0015] The material of the transition frame is the same as the material of the inner window frame, or the material of the transition frame is a material that is well weldable to the inner window frame.

[0016] The outer frame of the window is made of titanium alloy or aluminum alloy.

[0017] The edges of the optical window and the welding area between the window ring and the mounting platform are provided with a surface metallization layer.

[0018] In view of the above technical features, the present invention has the following beneficial effects: 1. The optical window is welded and fixed inside the inner frame of the window. The inner frame of the window is made of a material with a coefficient of thermal expansion similar to that of the optical window material. The window ring is welded and fixed to the upper end face of the optical window, balancing the stress on the upper and lower end faces of the optical window after welding and ensuring the surface quality of the optical window after welding; 2. The ring wall of the transition frame is a thin-walled structure. The gap between the inner frame of the window and the transition frame constitutes a low-stress installation structure for the optical window, effectively reducing the stress during window welding and the stress influence of external structures on the window; 3. By utilizing the thin-walled structure of the ring wall of the transition frame, and the gap between the transition frame and the outer frame and inner frame of the window, the lightweight material of the outer frame of the window is physically isolated from thermal expansion and contraction and structural deformation, achieving the stress isolation effect of the optical window; 4. The setting of the outer frame of the window and the application of lightweight material for the outer frame of the window effectively improve the lightweight effect of the infrared detector assembly. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the optical window structure of the present invention;

[0020] Figure 2 This is a schematic diagram of the welding of the inner frame of the window in this invention;

[0021] Figure 3 This is a schematic diagram of the welding of the window outer frame of the present invention;

[0022] In the diagram: 1-Optical window; 2-Inner frame of the window; 21-Frame wall; 22-Mounting platform; 3-Window ring; 4-Transition frame; 41-Ring wall; 42-Upper edge; 43-Lower edge; 5-Outer frame of the window. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that some components well-known to those skilled in the art but not related to the main content of the present invention may be omitted in the drawings or description. Additionally, for ease of description, some components in the drawings may be omitted, enlarged, or reduced, but this does not represent the actual size or complete structure of the product.

[0024] A low-stress mounting structure for an optical window, such as Figure 1-3 As shown, it includes an inner window frame 2, a window ring 3, a transition frame 4, and an outer window frame 5, which are disposed at the edge of the optical window 1 and are adapted to the shape of the optical window 1. Both the inner window frame 2 and the window ring 3 are provided with openings for the optical window 1.

[0025] like Figure 2As shown, the inner frame 2 of the window includes a vertical frame wall 21 and an inwardly facing mounting platform 22 at the bottom of the frame wall. Its cross-section is L-shaped. The lower edge of the optical window 1 is welded and fixed to the mounting platform 22. A window ring 3 is provided corresponding to the mounting platform 22. The window ring 3 is welded and fixed to the upper end of the frame wall of the inner frame 2 of the window and to the upper edge of the optical window 1. The window ring 3 and the mounting platform 22 clamp and fix the optical window 1, balancing the force on the upper and lower end faces of the optical window 1 after welding, and ensuring the surface quality of the optical window 1 after welding.

[0026] Preferably, the material of the inner window frame 2 matches the coefficient of thermal expansion of the material of the optical window 1. The material of the window ring 3 is the same as that of the inner window frame 2. The materials of the inner window frame 2 and the window ring 3 are selected from metal materials with coefficients of thermal expansion matching those of the optical window 1, such as Kovar, Invar, TC4, etc.

[0027] The edge of the optical window 1 and the welding area between the window ring 3 and the mounting platform 22 are provided with a surface metallization layer.

[0028] Furthermore, the thickness and opening size of the window ring 3 are consistent with the thickness and opening size of the mounting platform 22.

[0029] like Figure 1 , Figure 3 As shown, the transition frame 4 is positioned between the inner window frame 2 and the outer window frame 5. The inner side of the transition frame 4 is welded and fixed to the inner window frame 2, with a gap between the inner side of the transition frame 4 and the inner window frame 2. The outer side of the transition frame 4 is welded and fixed to the outer window frame 5, with a gap between the outer side of the transition frame 4 and the outer window frame 5. These two gaps physically isolate the lightweight material of the outer window frame 5 from thermal expansion and contraction and structural deformation, achieving stress isolation for the optical window 1.

[0030] Preferably, such as Figure 3 As shown, the transition frame 4 includes an interconnected ring wall 41, an upper edge 42, and a lower edge 43. The upper edge 42 is located at the top of the ring wall 41 and protrudes inward from the ring wall 41. It is welded and fixed to the upper end of the frame wall 21 of the inner frame 2 of the window. A gap is left between the frame wall 21 and the ring wall 41. The lower edge 43 is located at the bottom of the ring wall 41 and protrudes outward from the ring wall 41. It is welded and fixed to the bottom inner side of the outer frame 5 of the window. A gap is left between the ring wall 41 and the outer frame 5 of the window.

[0031] The material of the transition frame 4 is the same as the material of the inner window frame 2, or the material of the transition frame 4 is a material that is well weldable to the inner window frame 2.

[0032] The thin-walled structure of the ring wall 41 of the transition frame 4, as well as the gap between the ring wall 41 and the frame wall 21 and the gap between the ring wall 41 and the outer frame of the window 5, provides the entire device with a margin of elasticity. It effectively isolates the stress of the lightweight material of the outer frame of the window 5 from thermal expansion and contraction and structural deformation, and effectively eliminates the adverse effects of stress on the optical window 1.

[0033] Furthermore, the wall thickness of the annular wall 41 of the transition frame is 0.1 mm to 0.2 mm.

[0034] The width of the gap between the frame wall 21 and the ring wall 41 of the inner frame 2 of the window is 0.5mm to 1mm.

[0035] The outer frame 5 of the window is made of lightweight titanium alloy or aluminum alloy, which makes the entire device lightweight.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. A low-stress mounting structure for an optical window, characterized in that: It includes an inner window frame (2), a window ring (3), a transition frame (4), and an outer window frame (5) that are adapted to the shape of the optical window (1) and are located at the edge of the optical window (1); the inner window frame (2) and the window ring (3) are both provided with openings for the optical window (1); The inner frame (2) of the window includes a vertical frame wall (21) and a mounting platform (22) protruding inward from the bottom of the frame wall (21). Its cross-section is L-shaped. The lower edge of the optical window (1) is welded and fixed to the mounting platform (22). The window ring (3) corresponds to the mounting platform (22). The window ring (3) is welded and fixed to the upper end of the frame wall (21) of the inner frame (2) of the window and welded and fixed to the upper edge of the optical window (1). The window ring (3) and the mounting platform (22) clamp and fix the optical window (1). The transition frame (4) is set between the inner frame (2) and the outer frame (5) of the window. The inner side of the transition frame (4) is welded and fixed to the inner frame (2) of the window, and a gap is left between the inner side of the transition frame (4) and the inner frame (2) of the window; the outer side of the transition frame (4) is welded and fixed to the outer frame (5) of the window, and a gap is left between the outer side of the transition frame (4) and the outer frame (5) of the window.

2. The low-stress installation structure as described in claim 1, characterized in that: The transition frame (4) includes an interconnected ring wall (41), upper edge (42) and lower edge (43). The upper edge (42) is located at the top of the ring wall (41) and protrudes to the inside of the ring wall (41). It is welded and fixed to the upper end of the frame wall (21) of the inner frame of the window (2). A gap is left between the frame wall (21) and the ring wall (41). The lower edge (43) is located at the bottom of the ring wall (41) and protrudes to the outside of the ring wall (41). It is welded and fixed to the bottom of the inner side of the outer frame of the window (5). A gap is left between the ring wall (41) and the outer frame of the window (5).

3. The low-stress installation structure as described in claim 2, characterized in that: The wall thickness of the ring wall (41) of the transition frame is 0.1 mm to 0.2 mm.

4. The low-stress installation structure as described in claim 2, characterized in that: The width of the gap between the frame wall (21) and the ring wall (41) of the inner frame (2) of the window is 0.5 mm to 1 mm.

5. The low-stress installation structure as described in claim 1, characterized in that: The material of the inner frame (2) of the window matches the material expansion coefficient of the optical window (1).

6. The low-stress installation structure as described in claim 1, characterized in that: The material of the window ring (3) is the same as the material of the inner window frame (2).

7. The low-stress installation structure as described in claim 6, characterized in that: The thickness and opening size of the window ring (3) are the same as the thickness and opening size of the mounting platform (22).

8. The low-stress installation structure as described in claim 1, characterized in that: The material of the transition frame (4) is the same as that of the inner window frame (2), or the material of the transition frame (4) is a material that is well weldable to the inner window frame (2).

9. The low-stress installation structure as described in claim 1, characterized in that: The material of the window frame (5) is titanium alloy or aluminum alloy.

10. The low-stress installation structure as described in claim 1, characterized in that: The edge of the optical window (1) and the welding area of ​​the window ring (3) and the mounting platform (22) are provided with a surface metallization layer.

Images