Lightweight waterproof reference plate for airborne hyperspectral imager

Abstract

The utility model discloses an airborne hyperspectral imager light weight waterproof reference board relates to hyperspectral imager reference board technical field, this airborne hyperspectral imager light weight waterproof reference board, including from top to bottom sequentially layering setting's substrate, gradient honeycomb sandwich structure and backboard, substrate, gradient honeycomb sandwich structure and backboard form reference board, substrate upside is provided vacuum aluminizing reflection layer and diamond -like carbon protection layer in proper order, gradient honeycomb sandwich structure is embedded in the substrate inside, and its honeycomb unit aperture gradient reduces from center to edge, and wall thickness gradient increases from center to edge. The utility model integrates gradient honeycomb sandwich and carbon fiber sandwich structure and realizes light weight high stiffness, combines compound sealing and initiative air pressure balance technology and promotes environmental adaptability, adopts mechanical guide and quick positioning installation system and super -hydrophobic surface design of magnetic attraction cooperation simultaneously, ensures that reference board has high stability, high repeatability installation accuracy under complex working condition.

Description

Technical Field

[0001] This utility model relates to the field of reference plate technology for hyperspectral imagers, and in particular to a lightweight and waterproof reference plate for airborne hyperspectral imagers. Background Technology

[0002] In hyperspectral remote sensing applications, the accurate inversion of ground reflectance relies on a stable, uniform, and high-reflectance reference surface provided by a calibration reference plate. As a key component of radiometric calibration, the surface optical properties, geometric stability, and environmental adaptability of the reference plate directly affect the calibration accuracy and data reliability. Traditional reference plates often use aluminum alloy substrates sprayed with diffuse reflective coatings (such as Spectralon®) or anodized to achieve high diffuse reflectance performance, but they suffer from problems such as heavy weight, easy deformation, and poor weather resistance, making it difficult to meet the dual requirements of lightweight payload and high stability for small and light aircraft such as UAVs.

[0003] With the development of composite material technology, carbon fiber reinforced composite materials have been gradually applied to optical platform structures due to their high specific stiffness, low coefficient of thermal expansion and excellent fatigue resistance. However, it is still difficult to meet the requirements of lightweight and bending stiffness by simply using carbon fiber flat plates. Especially under complex working conditions such as flight vibration and temperature difference, micro-deformation is prone to occur, which leads to the inaccuracy of the reflective surface. Some solutions introduce honeycomb sandwich structures to improve the stiffness-to-weight ratio, but conventional uniform cross-section honeycomb cores have insufficient support in the edge area, which is prone to local collapse or stress concentration, affecting the overall flatness.

[0004] Furthermore, existing reference boards generally lack effective environmental protection designs. When used outdoors in rainy, humid, and dusty environments, moisture can easily penetrate the sealed cavity, causing internal condensation, moisture absorption and expansion of honeycomb channels, or corrosion of metal components. This can lead to increased weight, structural deformation, and even degradation of optical performance. Although some products use O-ring seals, the completely sealed cavity can generate internal and external pressure differences when the temperature changes. Long-term use can easily cause seal failure or panel bulging. At the same time, traditional installation methods rely on screws or clamps for fixing, which is cumbersome, has poor installation repeatability, and often results in angular deviations exceeding 1°, seriously affecting the consistency of calibration data over multiple time periods.

[0005] Although existing technologies have attempted to introduce magnetic mounting or hydrophobic coatings to improve convenience and anti-fouling capabilities, most of them are single-function superpositions and lack systematic integrated design. How to achieve lightweight, high rigidity, and high sealing performance while taking into account active air pressure regulation, rapid and accurate positioning, and all-weather protection functions remains a technical challenge for current airborne hyperspectral calibration reference boards. Utility Model Content

[0006] This utility model provides a lightweight waterproof reference plate for an airborne hyperspectral imager, comprising a substrate, a gradient honeycomb sandwich structure, and a back plate stacked sequentially from top to bottom. The substrate, gradient honeycomb sandwich structure, and back plate form the reference plate. A vacuum-plated aluminum reflective layer and a diamond-like carbon protective layer are sequentially disposed on the upper side of the substrate. The gradient honeycomb sandwich structure is embedded inside the substrate, and the honeycomb unit aperture decreases from the center to the edge, while the wall thickness increases from the center to the edge.

[0007] Preferably, the back plate and the edge of the substrate are sealed together by a fluororubber O-ring to form a closed cavity. The fluororubber O-ring is embedded in the annular groove at the edge of the carbon fiber substrate and is pressed together with the back plate to form a static seal between the optical panel and the back plate.

[0008] Preferably, a through hole is provided on the circumferential sidewall of the reference plate, on the radially outer side of the fluororubber O-ring sealing area, and a waterproof and breathable membrane is embedded in the through hole.

[0009] Preferably, the waterproof and breathable membrane is a circular polytetrafluoroethylene membrane embedded in a stepped hole structure with through holes in the side wall. Its outer side is limited by a metal protective mesh, its inner side is pressed by a pressure ring, and the circumferential edge of the waterproof and breathable membrane is sealed with sealant.

[0010] Preferably, the upper surface, sidewalls and outer surface of the back plate of the substrate are all provided with a nano-hydrophobic coating.

[0011] Preferably, a waterproof chamber is provided on one side of the back plate, and a miniature air pump is provided inside the waterproof chamber. The air outlet of the miniature air pump is connected to the sealed cavity of the reference plate through a flexible conduit, and a one-way valve is provided on the flexible conduit.

[0012] Preferably, the pressure sensor probe extends into the sealed cavity to monitor the internal air pressure in real time and control the micro air pump to maintain the internal air pressure higher than the external environment.

[0013] Preferably, the back plate has grooves at the four corners of its bottom, and neodymium iron boron magnets are installed in the grooves with the magnets facing downwards and a single magnetic attraction force greater than N, which is used to attach to the metal mounting platform to achieve tool-free and rapid fixation.

[0014] Preferably, the bottom of the back plate is provided with a set of opposing V-shaped grooves, which cooperate with the conical guide holes on the mounting platform.

[0015] Preferably, the bottom of the back plate is provided with a set of oppositely arranged conical positioning pins, the roots of which are fixed to the carbon fiber substrate by interference fit and structural adhesive, and the conical positioning pins are engaged with the grooves on the mounting platform.

[0016] The lightweight waterproof reference plate for airborne hyperspectral imagers provided in this embodiment of the invention, compared with the prior art:

[0017] 1. This utility model integrates a gradient honeycomb sandwich structure inside the substrate and combines it with a carbon fiber reinforced composite substrate and a back plate to form a lightweight and high-rigidity sandwich structure, which reduces the overall weight of the reference plate while ensuring surface flatness. This effectively suppresses the influence of flight vibration and temperature difference deformation on optical performance. Combined with a composite sealing system formed by fluororubber O-rings and waterproof and breathable membranes embedded in the stepped holes of the side walls, it achieves IP68-level liquid waterproof sealing and allows gas exchange between the inside and outside of the sealed cavity, avoiding structural deformation or condensation accumulation due to pressure imbalance. This improves the long-term stability and reliability of the reference plate in complex weather environments.

[0018] 2. This utility model features a rapid and precise positioning system consisting of a conical positioning pin, a V-groove, and a magnetic installation component working together. Through a tolerance-fitted mechanical guiding structure, it achieves highly repeatable installation with an angle deviation of less than 0.5°. Combined with four sets of N52-grade neodymium iron boron magnets providing a total magnetic attraction force greater than 20N, it enables tool-free rapid fixation, allowing the reference plate to be quickly and precisely installed and removed from UAV platforms or ground supports. Simultaneously, the fully covered nano-hydrophobic coating and diamond-like carbon protective layer work synergistically to give the reference plate superhydrophobic properties, effectively preventing the adhesion of rainwater, dew, and dust, ensuring the accuracy and consistency of reflectivity data during hyperspectral imager calibration, and improving field operation efficiency and remote sensing data quality. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present utility model;

[0021] Figure 2 This is a schematic diagram showing the overall structure of an embodiment of the present utility model.

[0022] Figure 3 This is a schematic diagram of the waterproof and breathable membrane structure according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the gradient honeycomb sandwich structure according to an embodiment of the present invention;

[0024] Figure 5 This is a cross-sectional view of the overall structure of an embodiment of the present utility model;

[0025] Figure 6This is a schematic diagram of the backplate structure of an embodiment of the present utility model;

[0026] Figure 7 This is a cross-sectional view of the substrate and other structures in an embodiment of the present invention.

[0027] Figure label:

[0028] 1. Substrate; 2. Gradient honeycomb sandwich structure; 3. Back plate; 4. Fluororubber O-ring; 5. Waterproof and breathable membrane; 6. Waterproof chamber; 7. Miniature air pump; 8. Flexible conduit; 9. One-way valve; 10. Pressure sensor; 11. V-groove; 12. Neodymium iron boron magnet; 13. Conical positioning pin; 14. Vacuum-plated aluminum reflective layer; 15. Diamond-like carbon protective layer; 16. Nano-hydrophobic coating. Detailed Implementation

[0029] The following detailed description, in conjunction with the accompanying drawings, outlines some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] Please refer to Figures 1-7 This utility model embodiment provides a lightweight waterproof reference plate for an airborne hyperspectral imager, comprising a substrate 1, a gradient honeycomb sandwich structure 2, and a back plate 3 stacked sequentially from top to bottom. The substrate 1 is made of carbon fiber reinforced composite material with a density of 1.6 g / cm³. 3 With a thickness of only 0.8mm, it combines high specific strength and excellent thermal stability. Its upper surface is sequentially provided with a vacuum-plated aluminum reflective layer 14 and a diamond-like carbon protective layer 15 to achieve high reflectivity and wear resistance.

[0031] The vacuum-plated aluminum reflective layer 14 is deposited using a vacuum coating process to deposit a high-reflectivity aluminum film with a reflectivity of up to 99% and a film thickness of 80nm±5nm, ensuring high reflectivity across a wide wavelength range.

[0032] The diamond-like carbon protective layer 15 has a thickness of 2μm and a hardness >20GPa, effectively preventing scratches and environmental corrosion.

[0033] The gradient honeycomb sandwich structure 2 is embedded inside the substrate 1. The gradient honeycomb sandwich structure 2 adopts a gradient distribution aperture design, so that the density of the core area is 0.8 g / cm³. 3 The density in the edge region is 1.2 g / cm³. 3 Achieving a balance between lightweight and impact resistance, the gradient honeycomb sandwich structure features a gradient wall thickness, transitioning from 50μm at the center to 100μm at the edges, thereby increasing the overall structural bending stiffness to 2.1×10⁻⁶. 4 N·m 2 While maintaining extremely low quality, it ensures surface flatness and resistance to deformation.

[0034] The backplate 3 is also made of carbon fiber reinforced composite material, which together with the substrate 1 forms a lightweight and high-rigidity sandwich structure.

[0035] To achieve good sealing performance, the back plate 3 and the edge of the substrate 1 are sealed together by a fluororubber O-ring 4 to form a closed cavity. The fluororubber O-ring 4 is embedded in the annular groove on the edge of the carbon fiber substrate 1 and is compressed by 25%±3% when the back plate 3 is pressed together to form a static mechanical seal, which effectively prevents the leakage of liquid and gas.

[0036] like Figure 3 As shown, a through hole is provided on the radially outer side of the circumferential sidewall of the reference plate, located in the sealing area of ​​the fluororubber O-ring 4. A waterproof and breathable membrane 5 is embedded in the through hole. The waterproof and breathable membrane 5 is a circular polytetrafluoroethylene membrane, which is embedded in the stepped hole structure of the through hole in the sidewall. Its outer side is limited by a metal protective mesh, and its inner side is pressed by a pressure ring. The circumferential edge of the waterproof and breathable membrane 5 is sealed with sealant to prevent leakage along the edge. This design achieves IP68-level liquid waterproof sealing and allows gas exchange between the inside and outside of the sealed cavity, avoiding structural deformation or condensation accumulation due to pressure imbalance.

[0037] The upper surface, sidewalls and outer surface of the backplate 3 of the substrate 1 are all provided with a nano-hydrophobic coating 16. The nano-hydrophobic coating 16 is directly coated on the upper surface of the diamond-like carbon protective layer 15 and is bonded to the diamond-like carbon protective layer 15 by chemical bonding. The thickness is 5–20 μm.

[0038] The nano-hydrophobic coating 16 is composed of fluorinated silane-modified silica nanoparticles, forming a superhydrophobic surface with a micro-nano composite structure. The static contact angle is greater than 150°, effectively preventing the adhesion of rainwater, dew, and dust, and ensuring the accuracy and consistency of reflectance data during the calibration of the hyperspectral imager.

[0039] like Figure 5 As shown, a waterproof chamber 6 is provided on one side of the back plate 3. A miniature air pump 7 is provided inside the waterproof chamber 6. The air outlet of the miniature air pump 7 is connected to the sealed cavity of the reference plate through a flexible conduit 8. A one-way valve 9 is provided on the flexible conduit 8 to prevent gas backflow. The pressure sensor 10 probe extends into the sealed cavity to monitor the air pressure inside the cavity in real time and control the miniature air pump 7 to maintain the internal air pressure 50Pa higher than the external environment to prevent moisture penetration.

[0040] like Figure 6 As shown, grooves are provided at the four corners of the bottom of the back plate 3, and neodymium iron boron magnets 12 are installed in the grooves. The magnets are all facing downwards with the same polarity. The magnetic attraction force of a single set is greater than 5N, which is used to attach to the metal mounting platform to achieve tool-free quick fixation. A set of V-shaped grooves 11 are also provided at the bottom of the back plate 3. The V-shaped grooves 11 cooperate with the conical guide holes on the mounting platform to ensure that the installation angle deviation is less than 0.5°.

[0041] In addition, a set of oppositely positioned conical positioning pins 13 are provided at the bottom of the back plate 3. The base of the pins is fixed to the carbon fiber substrate 1 by interference fit and structural adhesive. The conical positioning pins 13 fit with the groove on the mounting platform to further improve the installation accuracy and repeatability.

[0042] In summary, the reference plate is attached to the metal platform by the neodymium iron boron magnet 12 at the bottom of the back plate 3. The conical positioning pin 13 and the V-groove 11 cooperate to achieve guidance and positioning, ensuring that the installation angle deviation is <0.5°. The pressure sensor 10 monitors the air pressure in the sealed cavity. When it is lower than the set value, it controls the micro air pump 7 to start and replenish air into the cavity through the flexible conduit 8 and the one-way valve 9 to maintain the internal pressure 50Pa higher than the external pressure. The waterproof and breathable membrane 5 balances the internal and external air pressure. The nano hydrophobic coating 16 is anti-fouling and waterproof, ensuring stable reflectivity, and is suitable for UAV hyperspectral calibration operations.

[0043] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A lightweight waterproof reference plate for an airborne hyperspectral imager, characterized in that: The substrate (1), gradient honeycomb sandwich structure (2) and back plate (3) are stacked sequentially from top to bottom. The substrate (1), gradient honeycomb sandwich structure (2) and back plate (3) form a reference plate. A vacuum-plated aluminum reflective layer (14) and a diamond-like carbon protective layer (15) are sequentially disposed on the upper side of the substrate (1). The gradient honeycomb sandwich structure (2) is embedded inside the substrate (1). The pore size of its honeycomb unit decreases from the center to the edge, and the wall thickness increases from the center to the edge.

2. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 1, characterized in that: The back plate (3) and the edge of the substrate (1) are sealed together by a fluororubber O-ring (4) to form a closed cavity. The fluororubber O-ring (4) is embedded in the annular groove on the edge of the carbon fiber substrate (1) and pressed together with the back plate (3) to form a static seal between the optical panel and the back plate (3).

3. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 2, characterized in that: On the circumferential sidewall of the reference plate, on the radial outer side of the sealing area of ​​the fluororubber O-ring (4), there is a through hole penetrating the sidewall, and a waterproof and breathable membrane (5) is embedded in the through hole.

4. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 3, characterized in that: The waterproof and breathable membrane (5) is a circular polytetrafluoroethylene membrane embedded in the stepped hole structure of the side wall through hole. Its outer side is limited by a metal protective mesh, and its inner side is pressed by a pressure ring. The circumferential edge of the waterproof and breathable membrane (5) is sealed with sealant.

5. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 1, characterized in that: The substrate (1) has a nano-hydrophobic coating (16) on its upper surface, sidewalls and the outer surface of its back plate (3).

6. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 5, characterized in that: A waterproof chamber (6) is provided on one side of the back plate (3). A micro air pump (7) is provided inside the waterproof chamber (6). The air outlet of the micro air pump (7) is connected to the sealed cavity of the reference plate through a flexible conduit (8). A one-way valve (9) is provided on the flexible conduit (8).

7. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 6, characterized in that: The pressure sensor (10) probe extends into the sealed cavity to monitor the air pressure inside the cavity in real time and control the micro air pump (7) to maintain the internal air pressure higher than the external environment.

8. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 1, characterized in that: The back plate (3) has grooves at the four corners of its bottom, and neodymium iron boron magnets (12) are installed in the grooves. The magnets are all facing downwards with the same polarity. The magnetic attraction force of a single magnet is greater than 5N, which is used to attach to the metal mounting platform to achieve tool-free quick fixation.

9. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 8, characterized in that: The bottom of the back plate (3) is provided with a set of opposing V-shaped grooves (11), which are engaged with the tapered guide holes on the mounting platform.

10. The lightweight waterproof reference plate for an airborne hyperspectral imager according to claim 9, characterized in that: The bottom of the back plate (3) is provided with a set of oppositely arranged conical positioning pins (13), the root of which is fixed in the carbon fiber substrate (1) by interference fit and structural adhesive, and the conical positioning pins (13) are engaged with the groove on the mounting platform.

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