Spaceborne Omnidirectional Staring Imaging System and Method

Abstract

The present invention relates to a spaceborne omnidirectional staring imaging system and method for space target surveillance. The system includes a long-wave infrared panoramic annular optical system, an electric intelligent light shield, an annular heterogeneous long-wave infrared detector, and a back-end signal processing circuit. The optical system adopts a cryogenic athermal design and combines with the electric light shield to dynamically suppress stray light, realizing the detection of the panoramic field of view at the earth's limb. The annular detector matches the panoramic field of view, simplifies the optical design, improves the imaging performance of the large field of view, and ensures seamless time domain and non-blind spatial domain. The back-end signal processing circuit is composed of FPGA, DSP, CPU, NPU, etc., realizing real-time space situation awareness and on-orbit adaptive adjustment of the payload. This system realizes the omnidirectional coverage of space target detection and improves the surveillance efficiency.

Description

Technical Field

[0001] The present invention relates to the field of optical remote sensing technology, and in particular to a satellite-borne omnidirectional staring imaging system and method. Background Art

[0002] Optical imaging systems are widely used for target detection and tracking, among which infrared detection systems complete target detection and tracking based on the difference between the heat energy radiated or reflected by the object and the background energy. Infrared detection systems are now widely used in night vision, detection, tracking, search and rescue, non-destructive evaluation, gas analysis and condition monitoring and other fields.

[0003] When space targets are in orbit, they will emit thermal radiation into space while reflecting the radiation from the sun and the earth. Due to their low temperature, the energy of spontaneous radiation is mainly concentrated in the long-wave infrared band. Satellites need to use long-wave infrared detection systems to monitor space targets. However, in order to achieve omnidirectional monitoring of space targets near the edge of the earth, existing satellite-borne monitoring systems usually rely on complex mechanical rotating imaging components. This detection method is not only unable to monitor wide-area space targets in real time, but also difficult to achieve accurate positioning of space targets. Summary of the invention

[0004] The present invention aims to provide a satellite-borne omnidirectional staring imaging system and method to solve the problem that the existing detection methods are not only unable to monitor wide-area space targets in real time, but also difficult to achieve accurate positioning of space targets.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a satellite-borne omnidirectional staring imaging system, comprising a long-wave infrared panoramic annular optical system, an electric intelligent sunshade, an annular heterogeneous long-wave infrared detector and a back-end signal processing circuit; the long-wave infrared panoramic annular optical system can obtain a panoramic field of view of the earth's limb centered on the satellite; the electric intelligent sunshade can dynamically suppress stray light; the annular heterogeneous long-wave infrared detector has an annular pixel layout matching the panoramic annular field of view, and can receive and image long-wave infrared radiation; the back-end signal processing circuit includes FPGA, DSP, CPU, and NPU chips, which can extract the position information and trajectory information of space targets in the panoramic image in real time, and control the electric intelligent sunshade to achieve on-orbit fine-tuning of the shading angle.

[0006] Specifically, the long-wave infrared panoramic annular optical system includes a panoramic surround reflector system and a refracting rear optical path; the panoramic surround reflector system can receive the long-wave infrared radiation of space targets in the annular field of view at the earth's limb, and reflect it to the refracting rear optical path; the refracting rear optical path has a zoom feature, which changes the total optical focal length of the entire optical system by changing the interval between lens groups, and uses a compensating optical group to compensate for image plane drift to maintain good imaging quality and contrast.

[0007] Specifically, the long-wave infrared panoramic annular optical system adopts cryogenic optics for athermalization design. Through an optical + structural composite passive athermalization design, combined with a modular topology optimization design method, the ultra-lightweight opto-mechanical structure self-compensating athermalization performance is achieved through opto-mechanical material matching design and additive manufacturing technology.

[0008] Specifically, the electric intelligent light-shield uses a parallel electric push rod array combined with a backend information processing circuit to realize the unfolding and folding of the upper and lower circles of the folding light-shield, so as to realize the on-orbit fine-tuning of the light-shielding angle.

[0009] Specifically, the annular heterogeneous long-wave infrared detector focal plane array has high dynamic range performance, can cope with the detection of small and weak targets under strong background radiation, and adopts a high-speed and low-noise readout circuit design to support high-speed data acquisition to complete the real-time perception of the space situation.

[0010] Specifically, the working process of the backend signal processing circuit includes:

[0011] Step 1: The FPGA performs analog-to-digital conversion, data packing, caching, and simple preprocessing on the analog signals output by the annular heterogeneous long-wave infrared detector;

[0012] Step 2: Transmit the preprocessed data to the DSP and NPU. Among them, the DSP is responsible for complex signal processing tasks such as FFT, convolution, and filtering, and the NPU is responsible for advanced pattern recognition or classification, such as target detection and recognition in images;

[0013] Step 3: Finally, transmit the processed data to the external system through the communication interface or output device for real-time feedback control.

[0014] A spaceborne omnidirectional staring imaging method includes the following steps:

[0015] Step 1: Use the long-wave infrared panoramic annular optical system to receive the long-wave infrared radiation of space targets in the earth limb panoramic field of view centered on the satellite and image it onto the annular heterogeneous long-wave infrared detector;

[0016] Step 2: Initially complete the extraction of the position information and trajectory information of space targets in the panoramic image through the backend signal processing circuit;

[0017] Step 3: Adjust the focal length of the optical system to further improve the signal-to-noise ratio and position information accuracy of the target.

[0018] Specifically, the long-wave infrared panoramic annular optical system realizes dynamic stray light suppression through the electric intelligent light-shield.

[0019] Specifically, the backend signal processing circuit outputs a trigger signal according to the change of the attitude information of the camera in orbit to control the electric intelligent light-shielding cover to realize the on-orbit fine adjustment of the light-shielding angle.

[0020] Principle and beneficial effects of the present technical solution:

[0021] (1) The spaceborne omnidirectional staring imaging system does not require a complex mechanical scanning structure and can monitor space targets moving at high speeds in the panoramic field of view of the earth's limb in real time.

[0022] (2) The long-wave infrared annular heterogeneous detector used in the spaceborne omnidirectional staring imaging system has an annular pixel layout that matches the panoramic annular field of view. Compared with the photosensitive pixel layout of traditional detectors, this structure simplifies the optical system design, improves the imaging performance in the panoramic field of view, and realizes seamless time domain and non-blind spatial domain for space surveillance.

[0023] (3) The spaceborne omnidirectional staring imaging system can operate in a low-earth orbit, which enables a smaller optical system to achieve the same detection effect as that in a geosynchronous orbit, thus significantly reducing the size and cost of the satellite. Brief Description of the Drawings

[0024] Figure 1 It is an exemplary operation diagram of the spaceborne omnidirectional staring imaging system for space target detection;

[0025] Figure 2 It is a schematic diagram of the long-wave infrared panoramic annular optical system of the embodiment;

[0026] Figure 3 It is a mapping diagram of the panoramic annular infrared optical system and the long-wave infrared annular heterogeneous focal plane array of the embodiment;

[0027] Figure 4 It is a working mode diagram of the electronically controlled intelligent light-shielding cover of the embodiment;

[0028] Figure 5 It is a hardware architecture diagram of the backend signal processing circuit of the embodiment;

[0029] In the figure: 1. Spaceborne omnidirectional staring imaging system; 2. Space target; 3. Annular field of view; 4. Free-form surface mirror; 5. Front fixed group; 6. Zoom group; 7. Fixed group; 8. Compensation group; 9. Annular heterogeneous long-wave infrared detector; 10. Upper ring of the light-shielding cover; 11. Lower ring of the light-shielding cover; 12. Parallel type electric push rod array; 13. Sun blocker; 14. Blocker along the annular slide rail; 15. Sunlight; 16. Rear optical path. Specific Embodiments

[0030] The present invention will be further described in detail below with reference to the drawings and embodiments:

[0031] Embodiment:

[0032] As Figure 1 shown, an example of the spaceborne omnidirectional staring imaging system 1 in the detection application of space target 2 is presented. This system has a 360° annular field of view 3 in this embodiment and observes the annular area in space above the Earth's surface. Once the space target 2 appears in the annular field of view 3, the spaceborne omnidirectional staring imaging system 1 can detect the long-wave infrared radiation of the space target 2 and then display it on a display device, an alarm system, or any device that emits a detection system. By combining the target detection and tracking algorithm, the system can extract the position information and trajectory information of the space target 2 in real time.

[0033] As Figure 2 shown, the long-wave infrared panoramic annular optical system includes a free-form mirror 4 and a refractive-diffractive rear optical path 16 composed of a front fixed group 5, a zoom group 6, a fixed group 7, and a compensation group 8. The long-wave infrared panoramic annular optical system is an optical system with a large field of view, a large aperture, a small F-number, a wide spectral band, and variable focal length. Spherical aberration, off-axis aberration, and chromatic aberration have a greater impact on the imaging quality of the optical system. The system uses a variety of materials such as germanium, zinc selenide, and chalcogenide glass to correct the chromatic aberration of the system, and uses free-form surfaces and high-order aspheric technologies to correct the aberration of the system. Through reasonable power distribution of various materials and lens curvature control, a large field of view, a large aperture, a small F-number, a wide spectral band, and variable focal length long-wave infrared panoramic annular optical system under athermal conditions is realized.

[0034] The three-dimensional panoramic field of view in the Earth's limb airspace is reflected by the free-form mirror 4 to obtain an annular outgoing infrared radiation beam with a smaller aperture and refraction angle. The long-wave infrared radiation then propagates through multiple lens groups of the refractive-diffractive rear optical path 16 and is finally mapped onto the focal plane array of the annular heterogeneous long-wave infrared detector 9. In order to avoid the energy outside the field of view, a Lyot stop can be used in some embodiments. The Lyot stop is located at the exit pupil, which can reduce the background radiation of the system structure and reduce stray light.

[0035] The long-wave infrared panoramic annular optical system is a zoom optical system. The total optical power of the entire optical system can be changed by changing the interval between the lens groups, and the relative aperture is basically kept unchanged during the zoom process, so that the imaging height remains unchanged and the imaging quality is clear. The optical system uses a moving compensation optical group to compensate for the image plane drift.

[0036] The long-wave infrared panoramic annular optical system has athermalized infrared opto-mechanical performance in an ultra-low temperature working environment and can adapt to the interference of external heat flux changes on the satellite platform. An optical-structural composite passive athermalization design is adopted, combined with a modular topology optimization design method. Through the matching design of opto-mechanical materials and additive manufacturing technology, an ultra-lightweight opto-mechanical structure with self-compensated athermalization performance is realized. In terms of optics, the stability of the focal plane during temperature change is mainly achieved by optimizing and distributing the focal lengths of each lens so that the defocus generated by the optical element compensates for the defocus generated by the mechanical structure. In terms of structure, a lightweight opto-mechanical structure design is mainly carried out based on the modular topology optimization design method, and the opto-mechanical structure topology optimization design is carried out by combining multi-parameter and multi-objective control constraints such as precision control, stiffness control, and strength control. The parts are manufactured by 3D printing additive manufacturing for the topology optimization design structure, avoiding the limitation of the traditional material processing technology on the topology optimization structure configuration, and realizing the ultra-lightweight structure design. Through the intelligent temperature control of the core optical components, the corresponding relationship between image quality and temperature is analyzed, and an intelligent temperature control adaptive model of the image plane and temperature is established. The active self-compensation ability of the image plane is realized through the model.

[0037] As Figure 3 shown, it shows the mapping of the limb omnidirectional annular field of view 3 to the long-wave infrared annular heterogeneous focal plane array. Figure 3 The long-wave infrared annular heterogeneous detector shown in A in has the characteristic of an adaptive pixel layout and can match the annular field of view 3 of the panoramic annular infrared optical imaging system. In addition, the detector has a high dynamic range performance, can detect weak targets under strong background radiation, and adopts a high-speed and low-noise readout circuit design, supports high-speed data acquisition, and can complete the real-time perception of the space situation. Figure 3 The upper field of view of the limb annular airspace shown in B is mapped to Figure 3 the outer ring of the annular heterogeneous focal plane shown in A in, and the lower field of view is mapped to Figure 3 the inner ring of the annular heterogeneous focal plane shown in A in. Figure 3 C in shows the imaging field of view of the long-wave infrared panoramic annular optical system after zooming in a certain embodiment. At this time, the zoom ratio is 2 times, the resolution is doubled, and the imaging field of view is Figure 3 the middle shaded area of the annular field of view 3 shown in C in.

[0038] As Figure 4The working mode of the shown electronically controlled intelligent light shield is that the upper ring 10 of the light shield, the lower ring 11 of the light shield and the parallel electric push rod array 12 are connected and are controlled by the rear-end information processing circuit of the camera to realize the unfolding and folding of the upper and lower rings of the folding light shield. Inside the fairing before the camera is launched, the control signal drives the parallel electric push rod array 12 to fold, so that the whole camera shrinks to the minimum volume; when the camera is deployed after being put into orbit, the parallel electric push rods receive the unfolding signal from the rear-end information processing circuit and quickly and accurately unfold the light shield in place, and can output control signals according to the change of the attitude information of the camera in orbit to realize the on-orbit fine adjustment of the light shielding angle.

[0039] The solar shutter 13 of the electronically controlled intelligent light shield can obtain the azimuth angle of the midnight sun on the horizon online and in real time from the rear-end information processing circuit, and control the solar shutter 13 to accurately move along the annular slide rail 14 to the solar azimuth angle, automatically unfold the shutter to block the sunlight 15, and avoid the damage of the midnight sunlight 15 directly shining on the detector. In the case of non-midnight sunlight 15 directly shining, the intelligent shutter retracts the shutter under the control of the rear-end information processing circuit without affecting the observation of the earth.

[0040] As Figure 5 shown, the hardware architecture of the rear-end signal processing circuit. The hardware deployment of the rear-end signal processing circuit adopts the architecture of FPGA+DSP+CPU+NPU to realize the hardware design of a high-performance processing platform to meet the requirements of real-time detection and tracking of space targets 2 by the space-based panoramic annular optical imaging system, and to control the electronically controlled intelligent light shield to realize the on-orbit fine adjustment of the light shielding angle.

[0041] The working process of the rear-end signal processing circuit can be described as follows: The CPU is responsible for the coordination of the whole system, manages the communication between chips, task scheduling and low-speed data processing. First, the FPGA performs analog-to-digital conversion, data packing, caching and other simple preprocessing on the analog signals output by the annular heterogeneous long-wave infrared detector 9; then when a frame buffer is full, the preprocessed data is transmitted to the DSP and NPU. Among them, the DSP is responsible for complex signal processing tasks such as FFT, convolution and filtering, and the processed data can be transmitted to the CPU for further processing or transmitted to the NPU for inference; the NPU is responsible for advanced pattern recognition or classification of data, such as target detection and recognition in images. Finally, the processed data is transmitted to the external system through the communication interface or output device, or used for real-time feedback control. The above data flow and communication mechanism can flexibly realize the orderly execution of multiple devices and multiple tasks, reduce the CPU processing time consumed by device-to-device communication, avoid conflicts caused by bus resource competition, and the architecture of the combination of FPGA, DSP, CPU and NPU can be flexibly expanded according to the application scenario to process different types of signals and realize the intelligent monitoring of space targets 2 in complex scenarios.

[0042] Although specific embodiments and aspects of the present disclosure have been illustrated and described herein, various other changes and modifications can be made without departing from the scope of the present disclosure. In addition, although various aspects have been described herein, these aspects need not be used in combination. Accordingly, the appended claims are intended to cover all such changes and modifications that fall within the scope of the embodiments of the present disclosure.

[0043] It should now be understood that embodiments of the present disclosure include an infrared detection system, a method, and a non-transitory computer-readable medium for space target 2 detection, and these infrared detection systems have a 360-degree panoramic field of view. It should also be understood that these embodiments are merely examples and are not intended to limit the scope of the present disclosure.

[0044] The above are only examples of the present invention, and common general knowledge such as specific technical solutions or characteristics known in the solutions is not described in detail herein. For those skilled in the art, without departing from the technical solutions of the present invention, several variations and improvements can be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope claimed in this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. An on-board omnidirectional staring imaging system, characterized in that: It includes a long-wave infrared panoramic annular optical system, an electric intelligent sunshade, an annular heterogeneous long-wave infrared detector and a back-end signal processing circuit; the long-wave infrared panoramic annular optical system can obtain a panoramic field of view of the earth's limb centered on the satellite; the electric intelligent sunshade can dynamically suppress stray light; the annular heterogeneous long-wave infrared detector has an annular pixel layout that matches the panoramic annular field of view, and can receive and image long-wave infrared radiation; the back-end signal processing circuit includes FPGA, DSP, CPU, and NPU chips, which can extract the position information and trajectory information of space targets in the panoramic image in real time, and control the electric intelligent sunshade to achieve on-orbit fine-tuning of the shading angle; The electric intelligent sunshade includes an upper sunshade circle, a lower sunshade circle and a parallel electric push rod array, which are connected to each other and controlled by the camera's back-end information processing circuit to achieve the expansion and contraction of the upper sunshade circle and the lower sunshade circle; the electric intelligent sunshade also includes a sun blocker, which can obtain the azimuth of the midnight sun on the horizon online and in real time from the back-end information processing circuit, and control the sun blocker to move accurately to the sun's azimuth along the annular slide rail, automatically expanding the shielding plate to block the sunlight.

2. The spaceborne omnidirectional staring imaging system according to claim 1, wherein: The long-wave infrared panoramic annular optical system comprises a panoramic surround reflector system and a refracting diffractive rear optical path; the panoramic surround reflector system can receive the long-wave infrared radiation of space targets in the annular field of view at the earth's limb and reflect it to the refracting diffractive rear optical path; the refracting diffractive rear optical path has a zoom feature, which changes the total optical focal length of the entire optical system by changing the interval between lens groups, and adopts a compensating optical group to compensate for image plane drift, so as to maintain good imaging quality and contrast.

3. The spaceborne omnidirectional staring imaging system according to claim 2, wherein: The long-wave infrared panoramic annular optical system adopts low-temperature optics for athermal design, and realizes ultra-lightweight optomechanical structure self-compensation athermal performance through optical-structural composite passive athermal design combined with modular topological optimization design method through optomechanical material matching design and additive manufacturing technology.

4. The spaceborne omnidirectional staring imaging system according to claim 1, wherein: The electric intelligent sunshade utilizes a parallel electric push rod array in combination with a back-end information processing circuit to realize the unfolding and folding of the upper and lower circles of the foldable sunshade, so as to achieve on-track fine adjustment of the shading angle.

5. The spaceborne omnidirectional staring imaging system according to claim 1, wherein: The annular heterogeneous long-wave infrared detector focal plane array has high dynamic range performance, can cope with weak target detection under strong background radiation, and adopts high-speed low-noise readout circuit design to support high-speed data acquisition to complete real-time perception of space situation.

6. The spaceborne omnidirectional staring imaging system according to claim 1, characterized in that, The workflow of the back-end signal processing circuit includes: Step 1: FPGA performs analog-to-digital conversion, data packaging, caching and simple preprocessing on the analog signal output by the annular heterogeneous long-wave infrared detector; Step 2: The pre-processed data is transmitted to the DSP and NPU, where the DSP is responsible for complex signal processing tasks and the NPU is responsible for advanced pattern recognition or classification; Step 3: Finally, the processed data is transmitted to the external system through the communication interface or output device for real-time feedback control.

7. A method for using the spaceborne omnidirectional staring imaging system according to claim 1, characterized in that, The following steps are involved: Step 1: Use the long-wave infrared panoramic annular optical system to receive the long-wave infrared radiation of space targets in the earth limb panoramic field of view centered on the satellite, and image it onto the annular heterogeneous long-wave infrared detector; Step 2: Initially extract the position information and trajectory information of space targets in the panoramic image through the backend signal processing circuit; Step 3: Adjust the focal length of the optical system to further improve the signal-to-noise ratio and position information accuracy of the target.

8. The method for using the spaceborne omnidirectional staring imaging system according to claim 7, characterized in that: The long-wave infrared panoramic annular optical system realizes dynamic stray light suppression through an electric intelligent light shield.

9. The method for using the spaceborne omnidirectional staring imaging system according to claim 8, characterized in that: The backend signal processing circuit outputs a trigger signal according to the change of the camera's on-orbit attitude information to control the electric intelligent light shield to realize on-orbit fine-tuning of the light-shielding angle.

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