Lightweight calibration integrating sphere for spaceflight

Abstract

The invention discloses a lightweight calibration integrating sphere for spaceflight, which relates to the field of structural design of space on-orbit optical calibration integrating spheres and comprises a lightweight shell, an optical diffuse reflection sphere, a calibration lamp, a calibration lamp detector and a light outlet. The light-weight shell comprises an upper part and a lower part, the lower part is provided with four through hole interfaces connected with the platform, the upper part and the lower part are in butt joint through six flange interfaces turned out from the edges, the upper shell and the lower shell are in light-weight design, and about 50% of structural weight is saved. The optical diffuse reflection sphere is provided with an upper part and a lower part which are respectively made of 10mm polytetrafluoroethylene materials, and the surface of the optical diffuse reflection sphere needs to be polished to the smoothness required by optical calibration. The calibration lamp comprises three independent lamp holder combinations, and one lamp group is arranged in a radial area of a light-emitting opening at an interval of 120 degrees. The calibration lamp detector comprises two single detector interfaces and two double detector structures. The structural design is obvious in lightweight effect, reasonable in structural distribution and low in space occupancy rate.

Description

Technical Field

[0001] This invention relates to the field of space on-orbit optical calibration integrating sphere structure design, specifically to a lightweight calibration integrating sphere for aerospace applications. Background Technology

[0002] Optical calibration integrating spheres, as crucial products for spaceborne calibration, play a vital role in the on-orbit calibration of optical instruments. Their structural design requires consideration of numerous factors, among which lightweight design and stability are essential performance characteristics for aerospace products and must be balanced. Currently, because aerospace integrating spheres are typically small in size and weight, given the optical input specifications, minimal sacrifices are made in the structural design to prioritize structural stability and optical efficiency. However, with the advancement of aerospace technology and the increasing emphasis on launch cost as a critical control factor, the weight of products often needs to be minimized. Therefore, achieving a balance between lightweight design and stability for aerospace calibration integrating spheres has become a pressing issue that needs to be addressed. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a lightweight calibration integrating sphere for aerospace applications. It possesses on-orbit operational capability, exhibits significant lightweighting, a rational structural distribution, and low space occupancy. Both the calibration lamps and detector mounting structures can withstand aerospace-grade vibrations, ensuring structural and functional integrity. This provides an effective and feasible implementation scheme for on-orbit optical calibration integrating sphere structures. This invention effectively couples multiple calibration lamps, multiple detectors, a lightweight structure, and a polytetrafluoroethylene sphere to achieve a calibration integrating sphere that meets the various requirements of stability, lightweighting, and vibration resistance in aerospace applications.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A lightweight calibration integrating sphere for aerospace applications includes a lightweight outer shell, an optical diffuse reflection sphere, a calibration lamp assembly, a calibration lamp detector, and a light outlet. The lightweight outer shell is formed by connecting an upper spherical shell and a lower spherical shell via a flange interface, and the lower spherical shell has a through-hole interface for connecting to a platform. The optical diffuse reflection sphere is composed of an upper sphere and a lower sphere, which are fixed to the upper and lower spherical shells respectively via a threaded pin positioning structure and silicone rubber. The calibration lamp assembly is radially distributed along the light outlet and fixed to the upper spherical shell. The calibration lamp detector includes a dual calibration lamp detector and a single calibration lamp detector, which are fixed to the upper spherical shell respectively via a base, a fixing pressure member, and a wire cover. The light outlet is located on the upper spherical shell and communicates with the interior of the optical diffuse reflection sphere. The characteristic wall thickness of the upper and lower spherical shells is reduced from 4.5 mm to 2 mm. The inner wall of the lightweight outer shell is not coated.

[0006] Furthermore, both the upper and lower spherical shells are provided with planetary orbit-shaped reinforcing ribs.

[0007] Furthermore, both the upper and lower spheres are made of 10 mm thick polytetrafluoroethylene, with polished inner and outer surfaces and no reflective coating.

[0008] Furthermore, the lower end of the threaded pin positioning structure is a 4 mm pin shaft, and the upper end is an M4 thread, which mates with the pre-reserved pin hole on the spherical shell and the spherical body.

[0009] Furthermore, there are three sets of calibration lamp assemblies, which are fixed to the upper spherical shell at 120° intervals along the central axis of the light outlet, with the lamp axis pointing towards the center of the sphere.

[0010] Furthermore, the dual detectors of the calibration lamp are sequentially fastened to the upper spherical shell by screws, consisting of a large detector, a large detector base, two large detector fixing components, and a large detector wire cover.

[0011] Furthermore, the calibration lamp single detector consists of a small detector, a small detector base, a small detector fixing clamp, and a small detector wire cover, which are sequentially fastened to the upper spherical shell with screws.

[0012] Furthermore, the flange interface is evenly distributed at six points along the flanges of the upper and lower spherical shells, and is secured with M4 screws.

[0013] Furthermore, the light outlet is trumpet-shaped and can be detachably connected to the upper spherical shell via threads or flange.

[0014] Furthermore, silicone rubber is coated between the outer surfaces of the upper and lower spheres and the corresponding inner surfaces of the shells, and forms an adhesive layer after curing.

[0015] Beneficial effects:

[0016] 1. The present invention has a compact structure design that takes into account the requirements of lightweight, stability and adjustable optical energy level; both the upper and lower shells are designed to be lightweight, saving about 50% of the structural weight;

[0017] 2. This invention creatively utilizes different combinations of detector structure and lamp holder structure to achieve the layout of multiple light sources in a compact space and to achieve full monitoring.

[0018] 3. This invention redefines the lightweight integrating sphere shell form used in aerospace, and combines pin hole positioning and silicone rubber bonding methods to develop a new method for assembling the integrating sphere inner liner, which has passed the test of aerospace-grade vibration.

[0019] 4. The spherical shell of this invention does not have an internal coating, directly reducing the overall weight of the sphere; and the coating in the prior art requires multiple processes; if any one process fails, rework is necessary. Removing the coating shortens the development cycle and eliminates the risk of on-orbit contamination caused by film peeling and flaking; in addition, the coating is extremely prone to cracking in deep space cycles at -100℃ to +80℃, and the cracks become stray light particles; after removing the coating, the sphere and shell are only flexibly bonded by silicone rubber, and the expansion difference is absorbed by the adhesive layer, eliminating the cracking problem; on-orbit maintainability is better, and if the coating decays (ultraviolet radiation, atomic oxygen ablation) and the reflectivity decreases, it cannot be repainted on-orbit.

[0020] 5. This invention has strong engineering feasibility and provides ideas for lightweight design of aerospace integrating sphere structures. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the lightweight calibration integrating sphere for aerospace applications according to the present invention.

[0022] Figure 2 This diagram illustrates the relationship between the polytetrafluoroethylene inner liner and the outer spherical shell, as well as the dual-detector structure and the cross-sectional view of the single detector.

[0023] Figure 3a This is a schematic diagram of the dual detector structure for a calibration lamp.

[0024] Figure 3b This is a schematic diagram of a single detector structure for a calibration lamp.

[0025] Figure 4a This is a comparison chart of current data before and after vibration.

[0026] Figure 4b This is a comparison chart of radiance data before and after vibration. The figures are labeled as follows: 1. Lightweight small calibration integrating sphere for aerospace applications; 2. Upper sphere shell; 3. Lower sphere shell; 4. Upper sphere; 5. Lower sphere; 6. Calibration lamp assembly; 7. Dual calibration lamp detectors; 8. Single calibration lamp detector; 9. Threaded pin positioning structure; 10. Light outlet; 11. Through-hole interface; 12. Flange interface; 13. Small detector base; 14. Small detector; 15. Small detector fixing component; 16. Large detector base; 17. Large detector; 18. Large detector fixing component; 19. Small detector wire cover; 20. Large detector wire cover. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] like Figures 1-2 As shown, the lightweight miniature calibration integrating sphere 1 for aerospace applications of the present invention includes a lightweight shell, an optical diffuse reflection sphere, a calibration lamp assembly 6, a calibration lamp detector, a threaded pin positioning structure 9, and a light outlet 10, etc.

[0029] The lightweight outer shell is divided into an upper spherical shell 2 and a lower spherical shell 3.

[0030] The optical diffuse reflection sphere is divided into an upper sphere 4 and a lower sphere 5.

[0031] The calibration lamp detector includes two dual calibration lamp detectors 7 and two single calibration lamp detectors 8. The dual calibration lamp detectors 7 serve as the primary backup, ensuring that the other can still function normally if one fails. The single calibration lamp detectors 8 are detectors designed for different energy levels and wavelengths. The purpose of having two is to compare irradiance at different locations inside the sphere, ensuring the accuracy of the detector's readings.

[0032] The calibration lamp assembly 6, the calibration lamp dual detector 7, the calibration lamp single detector 8, and the light outlet 10 are all mounted on the upper spherical shell 2 with screws. The upper sphere 4 and the lower sphere 5 are fixed to the upper spherical shell 2 and the lower spherical shell 3 respectively by the threaded pin positioning structure 9 and silicone rubber. The upper spherical shell 2 and the lower spherical shell 3 are fixed with screws through 6 flange interfaces 12.

[0033] The lower spherical shell 3 has four through-hole interfaces 11 that connect to the on-orbit calibration platform for the load. The upper spherical shell 2 and the lower spherical shell 3 are connected by six flange interfaces 12 with the edges turned out. Both the upper spherical shell 2 and the lower spherical shell 3 are designed with a "planetary orbit" lightweight design. The so-called planetary orbit design means that one of the reinforcing ribs strictly passes through the "north and south poles" of the sphere, and the other reinforcing rib is arranged parallel to the "flange equatorial plane" steps like the latitude lines of the earth. This appearance and structural feature reduces the original wall thickness of the upper spherical shell 2 and the lower spherical shell 3 from 4.5 mm to a wall thickness of 2 mm, saving about 50% of the structural weight.

[0034] like Figure 2 As shown, the upper sphere 4 and lower sphere 5 are both made of 10mm thick polytetrafluoroethylene (PTFE) material, and their surfaces need to be polished to the smoothness required for optical calibration. During the assembly of the optical diffuse reflection sphere, the positions of the calibration lamp dual detector 7, calibration lamp single detector 8, and calibration lamp assembly 6 are aligned, and the sphere is finally positioned with the upper spherical shell 2 using the threaded pin positioning structure 9. After uniformly coating the outer surface of the PTFE with silicone rubber, it is fixed to the lightweight outer shell.

[0035] like Figure 1As shown, the calibration lamp assembly 6 comprises three independent lamp holder combinations, with one calibration lamp assembly 6 arranged every 120° in the radial region of the light outlet 10. All calibration lamps in the calibration lamp assemblies are designed to be precisely pointed towards the centroid of the calibration integrating sphere, ensuring that when the light source is turned on, the energy can be fully reflected inside the integrating sphere to achieve uniformity. During use, different energy levels required for calibration can be achieved by turning on one, two, or three calibration lamp assemblies 6.

[0036] like Figure 3a As shown, the calibration lamp dual detector 7 includes a large detector base 16, a large detector 17, two large detector fixing clips 18, and a large detector wire cover 20. The large detector 17 is fitted into the large detector fixing clip 18 with a tight fit and a single-sided gap of 0.1mm. The large detector fixing clip 18 is fixed to the large detector base 16 by two M2.5 screws. The large detector wire cover 20 and the large detector base 16 are connected and fixed to the upper spherical shell 2 by concentric through-hole interface screws.

[0037] like Figure 3b As shown, the calibration lamp single detector 8 includes a small detector base 13, a small detector 14, a small detector fixing member 15, and a small detector wire cover 19. The small detector 14 is fitted into the small detector fixing member 15 with a tight fit and a single-sided gap of 0.1mm. The small detector fixing member is fixed to the small detector base 16 by two M2.5 screws. The small detector wire cover 19 and the small detector base 13 are connected and fixed to the upper spherical shell 2 by concentric through-hole interface screws.

[0038] Preferably, the threaded pin positioning structure 9 is designed as an M4 threaded pin structure with a lower diameter of 4mm (negative tolerance 0.05mm), a length of 5mm, and an upper diameter of 10mm. It is positioned by using the threads and 4mm (positive tolerance 0.05mm) pin holes reserved in the upper spherical shell 2 and lower spherical shell 3 of the lightweight outer shell and the upper spherical shell 4 and lower spherical shell 5 of the optical diffuse reflection sphere.

[0039] Preferably, the light outlet 10 is a horn-shaped light outlet. In order to meet the optical requirements for stray light, light outlet structures with different aperture specifications but compatible interfaces can be designed.

[0040] The installation process of the lightweight miniature calibration integrating sphere of the present invention is as follows:

[0041] Step 1: Prepare the lower spherical shell 3 and the lower sphere 5 of the optical diffuse reflection sphere. Since the lower spherical shell 3 and the lower sphere 5 do not have detector holes or calibration lamp assembly mounting holes, after uniformly applying silicone rubber to the outer surface of the lower sphere 5, the sphere is positioned and assembled using the threaded pin positioning structure 9 through the pre-made pin holes of the shell and the sphere.

[0042] Step 2: After uniformly coating the outer surface of the upper sphere 4 of the optical diffuse reflection sphere with silicone rubber, it is roughly positioned with the upper sphere shell 2 through the detector hole and the calibration lamp assembly hole. Then, the pre-made pin holes of the sphere shell and the sphere are used to perform positioning and assembly with the threaded pin positioning structure 9.

[0043] In steps 1 and 2, the threaded pin positioning structure 9 should be tightened by hand until it cannot be tightened further, and silicone rubber should be applied around the threaded pin.

[0044] Step 3: Install and fix the upper sphere 4 and upper sphere shell 2 to the lower sphere shell 3 and lower sphere 5 using six M4 screws via the flange interface 12 of the sphere shell flange, forming a combined structure. After assembling and fixing the combined structure, let it stand for 24 hours to allow the silicone rubber to dry before proceeding with subsequent operations.

[0045] Step 4: Fix the assembled dual detector 7 and single detector 8 of the calibration lamp to the interface position designed for the upper spherical shell 2 with 4 M3 screws. After the detector leads are processed, connect the large detector wire cover 20 and the small detector wire cover 19 to the concentric interfaces of the large detector base 16 and the small detector base 13 respectively and fix them with screws.

[0046] Step 5: Secure the assembled three calibration lamp assemblies 6 to the interface positions designed for the upper spherical shell 3 using four M3 screws.

[0047] In addition, this invention redefines the lightweight integrating sphere shell form used in aerospace, and combines pin hole positioning method and silicone rubber bonding method to develop a new method for assembling the integrating sphere inner liner, which has passed the test of aerospace-grade vibration test. Figure 4a , Figure 4b This invention demonstrates its successful aerospace-grade vibration testing, based on a fundamental frequency sweep of the integrating sphere before and after vibration, achieving a stable frequency of 230Hz ± 1Hz. The photoelectric properties of the integrating sphere are primarily determined by monitoring the emissivity of the light source and the stability of the current. Figure 4a and Figure 4b It can be seen that, before and after vibration, the calibration lamp assembly 6, the dual calibration lamp detector 7, and the single calibration lamp detector 8 in the integrating sphere structure disclosed in this invention all exhibited stable performance and met the usage requirements.

[0048] The working principle of this invention is as follows: A standard multi-level calibration integrating sphere light source is provided in orbit to calibrate the product's optical system specifications, ensuring the accuracy of the data transmitted from the product. Three sets of calibration lamp components 6 are used to calibrate the optical system at different energy levels and input magnitudes. The dual-detector 7 and single-detector 8 of the calibration lamps are used to monitor the input energy level and compare it with the product's output energy, ensuring first-hand data monitoring at both the "source" and "sink" of the optics. The performance of the detectors themselves also needs to be monitored in orbit, requiring self-testing and mutual calibration of different detector control groups to ensure the authenticity of the "source" data of the in-orbit optics.

[0049] The core task of the calibration integrating sphere is to generate a uniform beam of standard brightness in orbit, serving as a scale for onboard optical instruments. The entire process can be divided into generating standard light, homogenizing light, monitoring, and comparison.

[0050] 1. Standard light generation: Three sets of calibration lamps are evenly distributed at 120°, and can be turned on individually, in pairs, or all at once, providing low, medium, and high energy levels. The light first shines onto the 10 mm thick PTFE sphere wall, and after multiple diffuse reflections, a uniform brightness field is formed inside the sphere.

[0051] 2. Uniform light, i.e., forming uniform exit light: A uniform light field is output outward through a trumpet-shaped light outlet, forming a parallel beam that enters the inlet of the optical instrument being calibrated. The exit brightness is the standard scale value.

[0052] 3. Monitoring, i.e., real-time reading of standard values:

[0053] The dual-detector system employs a master-backup mode, using two identical large detectors for simultaneous sampling, with hardware parallel connection and software averaging. If the current / radiance drift of one channel exceeds the threshold, the system immediately alarms and switches to the other data channel to ensure uninterrupted standard value measurement. It is primarily used for the main reference function.

[0054] The single-detector system employs a cross-comparison mode, with two small detectors located at different positions within the sphere (equatorial + polar regions), simultaneously collecting irradiance data at their respective locations. A "two-point colorimetric" algorithm is used to check the spatial uniformity within the sphere in real time; if the difference between the two readings exceeds 2%, it is considered sphere wall contamination or lamp attenuation, triggering a compensation coefficient correction. Primarily used for low and medium energy levels, it can also be used for cross-validation with dual detectors to prevent single-level "drifting."

[0055] 4. Comparison, i.e., calibration: The ground pre-stores the "detector reading - exit radiance" curve. In orbit, the current detector reading is substituted into the curve to obtain the real-time standard radiance. The instrument being calibrated simultaneously measures the exit beam to obtain the measured radiance. The real-time standard radiance is divided by the measured radiance to obtain the correction coefficient, which is then transmitted for subsequent radiometric calibration of scientific data.

[0056] Furthermore, the multi-level energy light source provided by the calibration integrating sphere is diffusely reflected and uniformly incident into the product instrument in parallel. By comparing the initial energy of the light source detected by the calibration integrating sphere with the energy data detected by the optical product instrument, the performance indicators of the optical product instrument are judged, and the reliability and quality of the integrated optical product instrument are verified.

[0057] Furthermore, Figure 4b The mid-spectral radiance index is an important indicator for verifying whether the detector has physical damage before and after vibration. When the spectral radiance before and after vibration eventually becomes consistent under the same light source, it can be considered that the detector's fixing method and the structure of the calibration integrating sphere have passed the test of aerospace-grade vibration.

[0058] Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention discloses a lightweight integrating sphere structure with multi-level energy tunable on-orbit operation capability, which satisfies the requirements of multi-level tunable optical radiation energy, uniform light, lightweight structural design, and mechanical vibration resistance.

Claims

1. A lightweight calibration integrating sphere for aerospace applications, characterized by, The light-weight shell is formed by the upper and lower spherical shells through flange interface butt joint, the lower spherical shell is provided with a through-hole interface connected with the platform; the optical diffuse reflection sphere is composed of the upper and lower spheres, and is fixed with the upper and lower spherical shells through the threaded pin positioning structure and the silicone rubber; the calibration lamp assembly is evenly distributed along the light outlet and is fixed on the upper spherical shell, the calibration lamp detector includes calibration lamp double detector and calibration lamp single detector, which are fixed on the upper spherical shell through the base, fixed pressing piece and wire cover; the light outlet is arranged on the upper spherical shell and is in communication with the inside of the optical diffuse reflection sphere; the characteristic wall thickness of the upper and lower spherical shells is reduced from 4.5 mm to 2 mm; the inner wall of the light-weight shell is not provided with a coating.

2. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The upper and lower spherical shells are both provided with planet orbit-shaped reinforcing ribs.

3. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The upper and lower spheres are both made of 10 mm thick polytetrafluoroethylene, the inner and outer surfaces are polished, and there is no reflective coating.

4. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The lower end of the threaded pin positioning structure is a 4 mm pin shaft, and the upper end is an M4 thread, which cooperates with the pin hole reserved in the spherical shell and the sphere.

5. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The calibration lamp assembly has three groups, which are fixed on the upper spherical shell along the center axis of the light outlet every 120°, and the lamp shaft points to the sphere center.

6. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The calibration lamp double detector is sequentially fastened to the upper spherical shell by screws through the large detector, large detector base, two large detector fixed pressing pieces and large detector wire cover.

7. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The calibration lamp single detector is sequentially fastened to the upper spherical shell by screws through the small detector, small detector base, small detector fixed pressing piece and small detector wire cover.

8. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The flange interface is evenly distributed in six places along the upper and lower spherical shell flanging, and is locked by M4 screws.

9. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The light outlet is horn-shaped and can be detachably connected with the upper spherical shell through threads or flange.

10. The lightweight calibration integrating sphere for aerospace applications of claim 1, wherein, The silicone rubber is coated between the outer surfaces of the upper and lower spheres and the inner surfaces of the corresponding spherical shells, and forms an adhesive layer after curing.

Images