Spaceborne acquisition, tracking and pointing system and free space optical communication link establishment method

Abstract

The present application provides a spaceborne acquisition, tracking and pointing system and a free space optical communication link establishment method. The system comprises: an optical antenna, a laser generation module, a first detector, a light spot position determination module, a first tracking controller, and a first tracking execution mechanism. During terminal link establishment, a first terminal traverses scan points in an initial scan acquisition zone, and emits a first optical beam on the basis of the pointing direction of the currently traversed scan points. When a first feedback optical beam transmitted by a second terminal is received, the first terminal adjusts the boresight direction of the optical antenna. The first terminal emits a second optical beam by means of the optical antenna and receives a second feedback optical beam emitted by the second terminal in response to the second optical beam. When the second feedback optical beam is received, the first terminal emits a third optical beam by means of the optical antenna, so that the second terminal performs tracking processing in response to the third optical beam.

Description

Satellite-borne acquisition tracking and pointing system and free space optical communication link establishment method

[0001] Cross-reference to related applications

[0002] This application claims priority to the Chinese patent application No. 202410444079.0, filed on April 10, 2024, and entitled "Satellite-borne acquisition tracking and pointing system and free space optical communication link establishment method", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] Free space optical communication (FSO) is a communication method that uses free space as a transmission channel, which has the advantages of high code rate, high bandwidth, flexibility, etc. The acquisition, tracking and pointing (ATP) system is the most important subsystem in free space laser communication, which completes the functions of laser scanning acquisition, coarse tracking and fine tracking, and is used for establishing and maintaining the optical communication link.

[0004] The scanning acquisition stage is the initial stage of the establishment of the link between two communication terminals. The current traditional scanning method can be divided into two ways: beacon light scanning and beaconless light scanning. Beacon light scanning is widely used and the technology is relatively mature. However, the divergence angle of the beacon light is usually several times or even dozens of times of the signal light, which requires a large power laser generator. In addition, the beacon light generally uses a different waveband from the signal light, which requires an additional beacon light generating device, increasing the weight and volume of the terminal and the complexity of the optical path, thereby increasing the implementation cost.

[0005] In order to reduce power consumption and achieve the design concept of miniaturization, the beaconless light scanning method is proposed. This method directly uses the signal light for scanning without the need for additional beacon light components, reducing the development and launch costs. However, the divergence angle of the signal light is small, which leads to long scanning time, high probability of missed scanning, and greater sensitivity to satellite attitude changes and platform vibration.

[0006] Therefore, how to improve the scanning acquisition accuracy of the ATP system while considering low power consumption, low cost and miniaturization of the ATP system is a technical problem that needs to be solved. SUMMARY

[0007] Embodiments of the present application provide a satellite-borne acquisition tracking and pointing system and a free space optical communication link establishment method.

[0008] In a first aspect, the embodiments of the present application provide a spaceborne acquisition tracking and pointing system, comprising: an optical antenna, a laser generating module, a first detector, a spot position extraction module, a first tracking controller and a first tracking execution mechanism; the optical antenna is configured to transmit or receive a light beam; the laser generating module is configured to output the light beam to the optical antenna for transmission, and further configured to adjust a divergence angle of the output light beam; the first detector is configured to form an image according to the received light beam, determine whether the image contains a spot, and in the case that the image contains the spot, output a first spot image to the spot position extraction module; the spot position extraction module is configured to determine a first spot centroid offset according to the first spot image; and the first tracking controller is configured to control the first tracking execution mechanism to adjust a boresight direction of the optical antenna according to the first spot centroid offset.

[0009] In a second aspect, the embodiments of the present application provide a free space optical communication link establishment method, applied to a first terminal, comprising: determining an initial scanning acquisition area, wherein the initial scanning acquisition area comprises a plurality of scanning points; traversing the scanning points in the initial scanning acquisition area, and transmitting a first light beam through an optical antenna according to a pointing direction of a currently traversed scanning point; in the case that a first feedback light beam transmitted by a second terminal according to the first light beam is received, ending the traversal of the scanning points in the initial scanning acquisition area; forming a local first image according to the first feedback light beam, adjusting a boresight direction of the optical antenna according to a first spot centroid offset corresponding to the local first image, and transmitting a second light beam through the optical antenna, so that the second terminal transmits a second feedback light beam according to the second light beam; in the case that the second feedback light beam is received, transmitting a third light beam through the optical antenna, so that the second terminal performs tracking processing according to the third light beam, wherein a divergence angle of the third light beam is smaller than divergence angles of the first light beam and the second light beam.

[0010] In a third aspect, the embodiments of the present application provide a free space optical communication link establishment method, applied to a second terminal, and the method comprises the following steps: receiving a first light beam from a first terminal through an optical antenna; forming a local first image according to the first light beam; in the case that the local first image contains a light spot, adjusting the pointing direction of the visual axis of the optical antenna according to the first light spot centroid offset corresponding to the local first image; emitting a first feedback light beam through the optical antenna, so that the first terminal emits a second light beam according to the first feedback light beam; receiving the second light beam through the optical antenna, forming a local second image according to the second light beam, and adjusting the pointing direction of the visual axis of the optical antenna, so that the second light spot centroid offset corresponding to the local second image is less than a preset first light spot centroid offset threshold; emitting a second feedback light beam through the optical antenna, so that the first terminal emits a third light beam according to the second feedback light beam, wherein the divergence angle of the third light beam is smaller than the divergence angles of the first light beam and the second light beam; receiving the third light beam through the optical antenna, and performing tracking processing according to the third light beam.

[0011] In a fourth aspect, the embodiments of the present application provide an electronic device, comprising: one or more processors; a memory having one or more programs stored thereon, when the one or more programs are executed by the one or more processors, the one or more processors implement the free space optical communication link establishment method of the second aspect or the third aspect.

[0012] In a fifth aspect, the embodiments of the present application provide a computer readable storage medium having a computer program stored thereon, when the computer program is executed by a processor, the free space optical communication link establishment method of the second aspect or the third aspect is implemented.

[0013] In a sixth aspect, the embodiments of the present application provide a computer program product comprising a computer program, when the computer program is executed by a processor, the free space optical communication link establishment method of the second aspect or the third aspect is implemented. BRIEF DESCRIPTION OF DRAWINGS

[0014] FIG. 1 is a structural schematic diagram of an ATP system provided by the embodiments of the present application;

[0015] FIG. 2 is a working principle schematic diagram of an image compensation module provided by the embodiments of the present application;

[0016] FIG. 3 is a structural schematic diagram of an ATP system provided by the embodiments of the present application;

[0017] FIG. 4 is a working principle diagram of an ATP system provided by the embodiments of the present application;

[0018] FIG. 5 is a flow schematic diagram of a free space optical communication link establishment method provided by the embodiments of the present application;

[0019] FIG. 6 is a flow diagram of another free space optical communication link establishment method according to an embodiment of the present application;

[0020] FIG. 7 is a flow diagram of a free space optical communication link establishment method according to an embodiment of the present application;

[0021] FIG. 8 is a comparison diagram of a first light spot image and a second light spot image according to an embodiment of the present application;

[0022] FIG. 9 is a structural diagram of an electronic device according to an embodiment of the present application.

[0023] Reference signs explanation 1-optical antenna, 2-biaxial piezoelectric fast mirror, 3-first beam splitter, 4-second beam splitter, 5-beam receiver, 6-first detector, 7-second detector, 8-angular displacement sensor, 9-accelerometer, 10-gimbal. DETAILED DESCRIPTION

[0024] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions provided by the present application will be described in detail below with reference to the drawings.

[0025] In the following, example embodiments will be described more fully with reference to the accompanying drawings, in which example embodiments can be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided as a full and enabling disclosure of the application, and to fully convey the scope of the application to the skilled person. Example embodiments are described herein with reference to the accompanying drawings, in which:

[0026] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0028] In the following description, reference is made to the "some embodiments" which describe a subset of all possible embodiments, but it is to be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments and can be combined with each other as long as there is no conflict.

[0029] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present application, and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0030] To facilitate better understanding of the scheme of the embodiments of the present application, the related art is first introduced as follows.

[0031] In free space optical communication, the spaceborne acquisition, tracking and pointing system is a key technical system for ensuring the accurate pointing and stable tracking of the optical beams at both ends of the laser communication transceiver. The spaceborne acquisition, tracking and pointing system mainly consists of three subsystems of acquisition, tracking and pointing. The acquisition system is responsible for acquiring the target within a larger field of view, ensuring the initial establishment of the communication link; the tracking system is responsible for adjusting the pointing of the optical beam in real time after acquiring the target, ensuring that the optical beam can stably track the target; the pointing system further accurately controls the divergence angle and direction of the optical beam to achieve efficient and accurate transmission of the optical beam. This system plays a crucial role in free space laser communication and has important significance for realizing high-speed, long-distance and high-precision laser communication.

[0032] Beacon light scanning is a key technology in laser communication terminals, which is used to realize the acquisition and stable tracking of the communication link. The basic principle of beacon light scanning is that the laser communication terminal transmits a wide-beam beacon light with a large divergence angle, which is scanned over an uncertain area to acquire and track the target. When the target is scanned, the laser communication terminal will perform accurate pointing and tracking according to the received signal, thereby establishing a stable communication link. It can improve the speed and success rate of establishing the communication link, especially in the case of uncertain target position or complex space environment, the beacon light scanning technology can ensure the stable transmission of the optical beam, reduce the risk of communication link interruption, has certain anti-interference ability, and can maintain the stability of the communication link in complex space environment.

[0033] However, the use of beacon light scanning requires a large amount of power during scanning due to the large divergence angle, and the beacon light generally uses a different wavelength band from the signal light, requiring additional beacon light generating devices, increasing the weight and volume of the terminal and the complexity of the optical path, thereby increasing the implementation cost.

[0034] In order to reduce power consumption and realize the design concept of light and small, a beacon-free optical scanning method is proposed. This method directly uses signal light for scanning, without additional beacon light components, reducing the development and launch costs, but the divergence angle of the signal light is small, there are problems such as long scanning time and large missing scanning probability, and it is more sensitive to satellite attitude changes and platform vibration. At present, the beacon-free scanning method has only a few on-orbit scanning and capture verification experiments.

[0035] The research on the scanning and capture method is mainly focused on the improvement of the scanning method, such as using a combination of an advanced aiming mechanism and a finite state machine (FSM) as the scanning and capture execution mechanism, improving the scanning frequency and scanning range, reducing the scanning time, using a composite spiral scanning method to improve the coverage, and using a master-slave scanning and capture method to complete the fast scanning. These methods all directly use signal light with a small divergence angle for scanning, only consider the influence of satellite platform vibration and attitude drift on scanning and capture error, and do not consider the centroid calculation error caused by the movement of the image point affected by the satellite platform vibration and attitude drift of the receiver, resulting in insufficient scanning accuracy.

[0036] In order to reduce power consumption, improve communication link establishment efficiency and ensure the stability of the line after establishment, the embodiment of the application provides a satellite-based capture tracking and aiming system and a free space optical communication link establishment method.

[0037] Please refer to FIG. 1, which is a structural schematic diagram of a satellite-based capture tracking and aiming system (hereinafter referred to as ATP system) provided by the embodiment of the application, as shown in FIG. 1, in the embodiment of the application, the ATP system includes but is not limited to: an optical antenna, a laser generating module, a first detector, a spot position determination module, a first tracking controller and a first tracking execution mechanism.

[0038] The optical antenna is used for transmitting or receiving a light beam; the laser generating module is used for outputting a light beam to the optical antenna for transmission, and is also used for adjusting the divergence angle of the output light beam; the first detector is used for forming an image according to the received light beam, determining whether the image contains a light spot, and outputting a first light spot image to the spot position determination module in the case that the image contains a light spot; the spot position determination module is used for determining a first light spot centroid offset according to the first light spot image; and the first tracking controller is used for controlling the first tracking execution mechanism to adjust the boresight direction of the optical antenna according to the first light spot centroid offset.

[0039] It can be understood that the laser generating module can output a light beam and adjust the divergence angle of the output light beam, and the laser generating module sends the light beam with adjustable divergence angle to the optical antenna for transmission, so that the ATP system has the technical effect of adjustable size of the divergence angle of the transmitted light beam.

[0040] It should be noted that in the embodiments of the present application, the laser generating module and the optical antenna constitute a transmitting light path, the first detector, the spot position determining module, the first tracking controller, the first tracking execution mechanism and the optical antenna constitute a receiving light path, the transmitting light path and the receiving light path are separated, but the transmitting light path and the receiving light path share the optical antenna, that is, the optical antenna can complete the operation of the transmitting light beam and the operation of the receiving light beam. In the embodiments of the present application, the ATP system composed of the optical antenna, the laser generating module, the first detector, the spot position determining module and the first tracking controller can be used as a transmitting terminal and a receiving terminal.

[0041] For example, when the ATP system is used as a transmitting terminal, the laser generating module is connected to the optical antenna, when the transmitting terminal needs to transmit a light beam, a light beam with a specific divergence angle is output by the laser generating module to the optical antenna, and then the light beam is transmitted by the optical antenna. When the ATP system is used as a receiving terminal, when the optical antenna receives a light beam, the first detector forms an image according to the received light beam, and judges whether there is a light spot in the image. If there is a light spot, the first spot position determining module sends a first light spot image formed according to the received light beam to the first spot position determining module. The first spot position determining module determines the first light spot centroid offset according to the first light spot image. Then, the first tracking controller controls the first tracking execution mechanism to adjust the pointing direction of the optical antenna according to the first light spot centroid offset, so as to track the opposite terminal.

[0042] By using the ATP system provided in the embodiments of the present application, the signal light with adjustable divergence angle is output to perform communication link establishment. On the one hand, the signal light with large divergence angle can be used to replace the beacon light scanning method to reduce the volume and development cost of the laser communication terminal, realize fast positioning, and shorten the link establishment time. On the other hand, the signal light with small divergence angle can be used for high-precision link establishment to ensure the stability after the line is established.

[0043] It should be noted that the large divergence angle and the small divergence angle described in the embodiments of the present application refer to the divergence angle of the signal light transmitted by the optical antenna. In the process of free space optical communication link establishment, the divergence angle is relatively large (generally more than tens of micro-radians), which is called large divergence angle. The divergence angle is relatively small (generally a few micro-radians), which is called small divergence angle.

[0044] In the embodiments of the present application, in order to improve the calculation accuracy of the spot position, an image compensation module is further arranged in the ATP system. The image compensation module is used for performing motion compensation on the first light spot image according to the motion information of the first detector and the satellite attitude adjustment information, so as to output a second light spot image to the spot position determining module. The spot position determining module determines the first light spot centroid offset according to the second light spot image, and the first tracking controller controls the first tracking execution mechanism to adjust the optical antenna according to the first light spot centroid offset.

[0045] For example, referring to FIG. 2, a schematic diagram of the working principle of the image compensation module provided in the embodiment of the present application is shown in FIG. 2. The image compensation module functions as follows: fusing the motion information of the first detector and the satellite attitude adjustment information to obtain N motion data points, where N is an integer greater than 1; inputting the N motion data points into an imaging solution model to obtain a motion trajectory containing N sampling points; and performing motion compensation on the first light spot image according to the motion trajectory to obtain a second light spot image.

[0046] When the image compensation module is added, the first light spot centroid shift is determined by the second light spot image generated by the image compensation module, the system can compensate for the light spot image degradation caused by the motion of the optical axis, compensate for the influence of the platform vibration at the receiving end, and improve the light spot detection accuracy.

[0047] It should be noted that the motion information of the first detector in the embodiment of the present application includes linear displacement information and angular displacement information.

[0048] The ATP system further includes an accelerometer and an angular displacement sensor. The accelerometer is used to detect the linear displacement information of the first detector; and the angular displacement sensor is used to detect the angular displacement information of the first detector.

[0049] For example, in an embodiment of the present application, the image compensation module can be implemented by using a field programmable gate array (FPGA), the motion information of the first detector in the imaging process can be obtained by using three high-precision angular displacement sensors and three high-precision accelerometers, the angular displacement sensors are mutually orthogonal and fixed to the first detector to measure the angular displacement of the space pitch, yaw and roll; and the three accelerometers are mutually orthogonal and installed on the gimbal to measure the linear displacement in the three-axis direction of the space.

[0050] In the embodiment of the present application, the attitude adjustment of the optical antenna is realized by using the gimbal, so that the optical axis of the optical antenna is aligned with the transmitting terminal.

[0051] It can be understood that the image compensation module is added before the extraction of the light spot image centroid in the present application, in order to compensate for the light spot image smearing or ghosting phenomenon caused by the displacement of the image point due to the optical axis jitter, remove the interference of the vibration of the terminal on the light spot image during imaging, and make the subsequent light spot position extraction have higher accuracy.

[0052] It should be noted that the terminal boresight jitter information (containing N motion data points, the larger N is, the more accurate the jitter information obtained is, and the value of N needs to be considered comprehensively in terms of actual computing power and allowed calculation time) is obtained by fusing the satellite attitude adjustment information and the motion information of the first probe. The imaging calculation model is combined with the N motion data points to calculate the moving track of the image point on the image plane of the first probe, and then the point spread function is further established. The imaging calculation model can be calibrated in advance on the ground.

[0053] For example, in an embodiment of the present application, the establishment process of the point spread function is as follows:

[0054] Suppose the exposure time of the first probe is T, and an ideal light point in a certain three-dimensional space passes through the imaging point of the optical antenna on the first probe in an ideal case, but the terminal boresight jitter causes the image point to be "blurred" on the image plane, and the imaging quality is reduced. After fusing the satellite and platform sensor data, N motion data points of the light point relative to the boresight within the exposure time are obtained, and after calculation by the imaging calculation model, the moving track of the image point on the image plane is obtained, and there are also N sampling points on the moving track.

[0055] Suppose the energy left by the light point on the image plane is E, and the image point is considered to move at a constant speed between adjacent sampling points. The light energy obtained by each pixel on the moving track is proportional to the residence time of the image point on the pixel, and the number of sampling points on each pixel can be approximately used instead of the residence time. For example, n1 sampling points fall on a certain pixel on the track, and the light energy ΔE obtained by the pixel is:

[0056] The light energy obtained by each pixel on the track is calculated in turn, and the light energy of the pixel with coordinates (i, j) on the track is ΔE(i, j). The energy of each pixel is normalized to obtain the point spread function:

[0057] After obtaining the point spread function, a non-blind image restoration algorithm can be selected to solve the optimal clear image. The classical non-blind image restoration algorithms include Wiener filtering, Richardson-Lucy regularization algorithm, total variation (TV) regularization algorithm, etc. In addition, neural network algorithms have achieved good results in the field of image restoration, but they require a large amount of training data and are not suitable for the aerospace field. The selection of the algorithm for solving the optimal clear image in the embodiments of the present application is not limited.

[0058] The TV regularization algorithm has better restoration effect on the vibration-degraded image than the other two algorithms. Considering the sparsity of the spot image, an anisotropic TV / L2 model can be used for prior constraint, and the point spread function and the clear spot image are estimated alternately to improve the restoration effect.

[0059] The second light spot image obtained after the algorithm compensation has obvious noise suppression compared with the first light spot image, and the visual axis jitter is compensated, as shown in FIG. 8, a is the first light spot image, and b is the second light spot image. It can be seen that the second light spot image after the algorithm compensation is clearer than the first light spot image.

[0060] When the second light spot image is obtained, the second light spot image is sent to a light spot position determination module. The light spot position determination module determines the first light spot centroid offset according to the second light spot image, and the light spot position determination module has the following specific effects:

[0061] All target pixel points with a gray value lower than a preset gray threshold in the second light spot image are obtained, and the gray value of the target pixel point is set to 0 to obtain a third light spot image. The first initial centroid position is determined according to the gray value of each pixel point in the third light spot image. The pixels in a preset range centered on the first initial centroid position are interpolated to obtain a plurality of sub-pixel points corresponding to the third light spot image. The target centroid position is determined according to the gray value of each sub-pixel point corresponding to the third light spot image. The first light spot centroid offset is determined according to the target centroid position.

[0062] In a specific embodiment of the present application, the light spot position determination module determines the first light spot centroid offset as follows:

[0063] After the light spot position determination module obtains the second light spot image, the second light spot image is preprocessed, a preset gray threshold T is set, the gray value lower than T in the second light spot image is set to 0, the interference is reduced, and a third light spot image is obtained, as follows:

[0064] Where (m, n) represents the gray value of the mth row and nth column of the second light spot image, and the preset gray threshold T can be 1 / 2 of the maximum value of the light spot pixel gray value.

[0065] The light spot center extraction algorithm includes a boundary fitting Gaussian fitting algorithm, a circle fitting algorithm, a Hough algorithm, and a peak value method, a centroid method, a centroid method, and a gray gravity center method. For diffuse and broken light spots, the circle fitting method has poor accuracy; the Hough algorithm has high reliability, and has good adaptability to noise, deformation, partial area defects, and edge discontinuity, but has large calculation amount and slow speed. The Gaussian fitting algorithm and the centroid algorithm are more suitable for wireless laser communication, and one of them can be selected as the first initial centroid position extraction algorithm. The specific selection of the first initial centroid position algorithm is not limited in the present application.

[0066] Taking the first initial centroid position extracted by using the centroid algorithm as an example, the centroid algorithm is to use the gray value of a pixel as a weight to calculate the centroid of a light spot, so as to improve the calculation speed. Assuming that the picture size is MxN, and the gray value of each pixel is f(m, n), the calculation formula of the first initial centroid position (m', n') is:

[0067] After obtaining the first initial centroid position (m', n'), the pixels in the preset range centered on the first initial centroid position (m', n') are interpolated to obtain a plurality of sub-pixel points corresponding to the third light spot image. The sub-pixel points after interpolation are used to recalculate the centroid position by formula 4 to obtain the first target centroid position. It should be understood that the light spot position determination module calculates the light spot centroid position by using the above method, which can improve the detection accuracy of the light spot centroid position.

[0068] After the first target centroid position is determined, the first light spot centroid offset can be calculated according to the first target centroid position.

[0069] The first light spot centroid offset is determined by the light spot position determination module, and the first tracking controller can control the first tracking execution mechanism to adjust the boresight direction of the optical antenna according to the obtained first light spot centroid offset to establish a communication link. Exemplarily, the first tracking execution mechanism is a gimbal.

[0070] It can be understood that the first tracking controller controls the first tracking execution mechanism to adjust the boresight direction of the optical antenna according to the first light spot centroid offset, aiming to make the light spot of the received light beam image on the center of the first detector as much as possible.

[0071] It should be noted that the ATP system provided by the embodiment of the application further includes a biaxial piezoelectric fast mirror, a first beam splitter, a second beam splitter, a second detector, a light beam receiver and a second tracking controller.

[0072] The biaxial piezoelectric fast mirror is used to transmit the light beam received by the optical antenna to the first beam splitter.

[0073] The first beam splitter is used to split the received light beam into two light beams, the first light beam is transmitted to the first detector, and the second light beam is transmitted to the second beam splitter.

[0074] The second beam splitter is used to split the received light beam into two light beams, the first light beam is transmitted to the light beam receiver, and the second light beam is transmitted to the second detector.

[0075] a second detector configured to be turned on when the first spot centroid offset is less than a third spot centroid offset threshold, form an image based on the received light beam, determine whether the image contains a spot, and output a fourth spot image to a spot position determination module in a case where it is determined that the image contains a spot.

[0076] The spot position determination module is further configured to determine a second spot centroid offset based on the fourth spot image.

[0077] A second tracking controller configured to control the biaxial piezoelectric fast steering mirror to deflect to adjust a path of the received light beam based on the second spot centroid offset.

[0078] It should be noted that in the embodiments of the present application, the light beam passes through the biaxial piezoelectric fast steering mirror into the first beam splitter, and is split into two light beams after passing through the first beam splitter and is transmitted to the first detector and the second beam splitter respectively. The second beam splitter splits the received light beam into two light beams after receiving the light beam and transmits them to the light beam receiver and the second detector respectively. The light beam position satisfies the opening communication condition through the cooperation of the second detector, the spot position determination module and the second tracking controller, and communication is performed through the light beam receiver.

[0079] For example, referring to FIG. 3, an ATP system provided by the embodiments of the present application is shown in the figure. As shown in FIG. 3, 1 is an optical antenna, 2 is a biaxial piezoelectric fast steering mirror, 3 is a first beam splitter, 4 is a second beam splitter, 5 is a light beam receiver, 6 is a first detector, 7 is a second detector, 8 is an angular displacement sensor, 9 is an accelerometer, and 10 is a gimbal table.

[0080] After the light beam is received by the optical antenna 1, it is transmitted to the biaxial piezoelectric fast steering mirror 2 and then to the first beam splitter 3. The first beam splitter 3 splits the received light beam into two light beams, one of which is transmitted to the first detector 6 and the other of which is transmitted to the second beam splitter 4. The second beam splitter 4 splits the received light beam into two light beams, one of which is transmitted to the light beam receiver 5 and the other of which is transmitted to the second detector 7.

[0081] The first detector 6 forms an image based on the received light beam, determines whether the image contains a spot, and outputs a first spot image to the image compensation module in a case where it is determined that the image contains a spot. The image compensation module performs motion compensation on the first spot image and outputs a second spot image to the spot position determination module, so that the spot position determination module determines a first spot centroid offset based on the second spot image.

[0082] The second detector 7 is turned on when the first light spot centroid offset is less than the third light spot centroid offset threshold, forms an image according to the received light beam, determines whether the image contains a light spot, and outputs a fourth light spot image to the light spot position determination module in the case where it is determined that the image contains a light spot. The received light beam is transmitted to the second detector 7 through the first beam splitter 3 and the second beam splitter 4 to further control the alignment of the receiving end and the transmitting end, perfect the communication link, and enable wireless communication when the communication start condition is reached.

[0083] The light spot position determination module of the embodiment of the application further has the following effects: obtaining all target pixel points in the fourth light spot image whose gray scale values are lower than a preset gray scale threshold, and setting the gray scale values of the target pixel points to 0 to obtain a fifth light spot image; determining a second initial centroid position according to the gray scale values of the pixel points in the fifth light spot image; performing interpolation on the pixels in a preset range centered on the second initial centroid position to obtain a plurality of sub-pixel points of the fifth light spot image; determining a second target centroid position according to the gray scale values of the respective sub-pixel points corresponding to the fifth light spot image; and determining a second light spot centroid offset according to the second target centroid position.

[0084] For example, in an embodiment of the application, the light spot position determination module determines the second light spot centroid offset as follows:

[0085] After obtaining the fourth light spot image, the fourth light spot image is preprocessed first, a preset gray scale threshold T is set, the gray scale values lower than T in the fourth light spot image are set to 0 to reduce interference, and a fifth light spot image is obtained, and the formula is as follows:

[0086] Where (m, n) represents the gray scale value of the fourth light spot image at the mth row and the nth column, and the preset gray scale threshold T can be 1 / 2 of the maximum value of the gray scale of the light spot pixels.

[0087] One of the Gaussian fitting algorithm and the centroid algorithm is selected as the second initial centroid position extraction algorithm, and the specific selection of the second initial centroid position algorithm is not limited in the application.

[0088] Taking the centroid algorithm as an example for extracting the second initial centroid position, the gray scale value of the pixel is used as the weight to calculate the centroid of the light spot, and the calculation speed is improved. Assuming that the picture size is MxN, and the gray scale value of each pixel point is f(m, n), the calculation formula of the second initial centroid position (m', n') is as follows:

[0089] After obtaining the second initial centroid position (m', n'), the pixels in a preset range centered on the second initial centroid position (m', n') are interpolated to obtain a plurality of sub-pixel points corresponding to the fifth light spot image, and the centroid position is recalculated using the interpolated sub-pixel points to determine a second target centroid position according to formula 6, and the second light spot centroid offset can be determined by the second target centroid position.

[0090] The second tracking controller controls the deflection of the biaxial piezoelectric fast steering mirror according to the second light spot centroid offset to adjust the path of the received light beam, further controls the alignment of the receiving end and the transmitting end, perfects the communication link, and performs wireless communication when the communication opening condition is reached.

[0091] The first detector and the second detector are different in that the first detector is used to process a large divergence angle light beam, and the second detector is used to process a small divergence angle light beam.

[0092] It can be understood that the image compensation module can assist in processing the light beam, which can increase the signal-to-noise ratio of the detector, appropriately increase the exposure time of the detector, and overcome the problem of degradation of the light spot image caused by the jitter of the line-of-sight caused by the motion and attitude drift of the satellite platform after increasing the exposure time. The growth of the exposure time can help quickly complete positioning, and can be applied when a long exposure time is required to receive a large divergence angle light beam and a small divergence angle light beam. When applied to a short exposure time of light beam imaging and a high loop bandwidth, after fast positioning, high-precision communication can be performed, and the second detector can be directly operated without the need to add the image compensation module.

[0093] Please refer to FIG. 4, which is a working principle diagram of an ATP system provided by an embodiment of the present application. As shown in FIG. 4, the laser generation module and the optical antenna are connected to form a transmitting optical path of the embodiment of the present application. The laser generation module includes a laser emission control unit, a laser generator, and a pre-aiming mechanism. The laser generator supports changing the divergence angle size through a control circuit. The laser emission control unit is used to control the laser emission and the divergence angle change. The pre-aiming mechanism realizes aiming before emission. The optical antenna transmits light beams with different divergence angles.

[0094] The optical antenna, the biaxial piezoelectric fast steering mirror, the first beam splitter, the second beam splitter, the first detector, the image compensation module, the light spot position determination module, the first tracking controller, the first tracking control execution mechanism, the second detector, the second tracking controller, and the second tracking execution mechanism form a receiving optical path of the embodiment of the present application. When the optical antenna receives a light beam, the light beam is transmitted to the biaxial piezoelectric fast steering mirror and then incident on the first beam splitter. The first beam splitter divides the light beam into a first light beam transmitted to the first detector and a second light beam transmitted to the second beam splitter. The second beam splitter receives the light beam and divides it into a first light beam transmitted to the light beam receiver and a second light beam transmitted to the second detector.

[0095] When the light beam needs to be processed by increasing the exposure time, the first detector operates, and the received light beam is transmitted to the first detector after being split by the first beam splitter. The first detector generates a first light spot image, and after image compensation processing, a second light spot image is generated and transmitted to the light spot position determination module to determine the light spot centroid position and determine the first light spot centroid offset. Then, the receiving light path is controlled by the first tracking controller to control the first tracking execution mechanism to adjust the boresight of the optical antenna, reduce the first light spot centroid offset, and make the light spot centroid position image as much as possible in the center of the first detector.

[0096] When the first light spot centroid offset is less than the third light spot centroid offset threshold, the emitted light beam is converted into a small divergence angle light beam, the imaging time of the received light beam can be shortened, and the second detector is turned on. The second detector generates a fourth light spot image and directly transmits it to the light spot position determination module to determine the light spot centroid position and determine the second light spot centroid offset. Then, the second tracking controller controls the second tracking execution mechanism to deflect the two-axis piezoelectric fast mirror to adjust the reflection angle of the incident light to reduce the second light spot centroid offset and adjust the path of the received light beam until the communication condition is met.

[0097] The ATP system provided in the embodiments of the present application reduces the volume and development cost of the laser communication terminal, realizes control of the divergence angle of the emitted light beam, and on the other hand, realizes high-precision chain establishment and guarantees the stability after the line is established.

[0098] The ATP system in the above embodiments of the present application is used for establishing a communication link and performing free space optical communication. Next, the free space optical communication chain establishment method provided by the ATP system of the embodiments of the present application will be described.

[0099] Please refer to FIG. 5, which is a flowchart of a free space optical communication chain establishment method provided by the embodiments of the present application. As shown in FIG. 5, the free space optical communication chain establishment method in FIG. 5 is applied to a first terminal, which can also be referred to as a transmitting terminal. When applied to the first terminal, the free space optical communication chain establishment method provided by the embodiments of the present application includes but is not limited to steps S110 to S150:

[0100] Step S110, determining an initial scanning capture area, wherein the initial scanning capture area includes a plurality of scanning points.

[0101] Step S120, traversing the scanning points in the initial scanning capture area, and emitting a first light beam through an optical antenna according to the pointing of the currently traversed scanning point.

[0102] Step S130, ending the traversal of the scanning points in the initial scanning capture area when a first feedback light beam emitted by the second terminal according to the first light beam is received.

[0103] Step S140, forming a local first image according to the first feedback light beam, adjusting the optical antenna visual axis pointing according to the first light spot centroid offset corresponding to the local first image, and emitting a second light beam through the optical antenna, so that the second terminal emits a second feedback light beam according to the second light beam.

[0104] Step S150, in the case of receiving the second feedback light beam, emitting a third light beam through the optical antenna, so that the second terminal performs tracking processing according to the third light beam, wherein the divergence angle of the third light beam is smaller than the divergence angles of the first light beam and the second light beam.

[0105] The first terminal adopts the ATP system for satellite acquisition tracking and aiming provided by the embodiments of the present application, and completes optical communication link establishment by emitting three light beams with different divergence angles, wherein the first light beam has the largest divergence angle and is used for preliminary scanning and capturing the second terminal, i.e., the receiving end, and when the first feedback light beam emitted by the second terminal is received, it means that the second terminal has been captured; after capturing the second terminal, the second light beam with a large divergence angle is emitted again, and the second terminal receives the second light beam and feeds back the second feedback light beam to confirm that it can enter the tracking stage; after emitting the second light beam, the first terminal remains staring, and the second light beam is maintained during this process; when entering the tracking stage, the emitted light beam is switched to the third light beam with a small divergence angle for tracking.

[0106] In the establishment of the optical communication link, the embodiments of the present application switch the output light beams with different divergence angles for communication link establishment according to needs, which can achieve the technical effects of reducing power consumption and improving communication link establishment efficiency.

[0107] It should be noted that the first light beam is emitted according to the pointing of the currently traversed scanning point, including: staying at the currently traversed scanning point according to a preset dwell time; and emitting the first light beam towards the pointing of the currently traversed scanning point within the dwell time.

[0108] For example, terminal A as the first terminal, i.e., the emitting terminal, initiates scanning, the first tracking execution mechanism controls the deflection of the optical antenna, so that the large-divergence-angle scanning light beam starts from the center position of the uncertain region (FOU) and performs point-by-point scanning on the FOU region. The scanning mode can adopt spiral scanning with equal pitch and constant linear velocity, or can adopt raster scanning, raster spiral scanning and the like. The present application does not limit the selection of the scanning mode. The present application adopts a step-by-step scanning mode, which requires terminal A to traverse the uncertain region point by point and stay at each scanning point for a sufficient time. Terminal B as the second terminal, i.e., the receiving terminal, remains staring and waits for the light beam to be imaged. The dwell time is preset by both parties.

[0109] According to the agreed scanning speed, the first detector of the terminal B images in each period of residence time and judges whether a light spot image is detected, and if so, a first feedback light beam is transmitted to the terminal A. If the terminal A does not detect the feedback signal after the end of the residence time, the next point is continuously scanned, and if the feedback signal is not received after scanning all points, the initial position is returned for cyclic scanning.

[0110] It should be noted that before the scanning starts, the first terminal and the second terminal estimate the positions of each other according to ephemeris information and attitude measurement data, and the two terminals point to each other according to the estimated positions to complete the initial pointing operation. During the initial pointing process, due to the ephemeris accuracy and attitude measurement error and satellite vibration and other factors, the initial pointing has an error, and the size of the error directly determines the size of the initial capture FOU. Generally, the size of the initial capture uncertainty is 6 times the size of the initial pointing error.

[0111] The scanning capture can preliminarily lock the positions of the first terminal and the second terminal to facilitate subsequent operations.

[0112] The first detector in the first terminal is configured to form a local first image according to the first feedback light beam.

[0113] The first light spot centroid offset corresponding to the local first image is obtained by the following steps: motion compensation is performed on the local first image according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated local first image; and the first light spot centroid offset is determined according to the gray values of the pixel points in the compensated local first image.

[0114] The motion compensation process of the local first image can be as follows: the motion information of the first detector is detected by an accelerometer and an angular displacement sensor, the motion information of the first detector is fused with the satellite attitude adjustment information to obtain N motion data points, where N is an integer greater than 1; the N motion data points are input into an imaging solution model to obtain a motion trajectory containing N sampling points; and the motion trajectory is used to perform motion compensation on the local first image to obtain a compensated local first image.

[0115] The process of determining the first light spot centroid offset according to the gray values of the pixel points in the compensated local first image can be as follows: an initial centroid position is determined according to the gray values of the pixel points in the compensated local first image; the pixels in a preset range centered on the initial centroid position are interpolated to obtain a plurality of sub-pixel points corresponding to the compensated local first image; a target centroid position is determined according to the gray values of the sub-pixel points corresponding to the compensated local first image; and the first light spot centroid offset is determined according to the target centroid position.

[0116] It can be understood that, by compensating the received first image by using the image compensation module, image blur caused by the need to increase the exposure time during capturing can be reduced, and the subsequent first spot centroid offset is used to assist the two terminals to align, so as to facilitate subsequent operations.

[0117] Thanks to the spaceborne capturing, tracking and aiming system provided in the embodiments of the present application, the first terminal can capture and track the second terminal by adjusting the divergence angle of the emitted light beam, which can not only achieve the effect of fast link establishment, but also does not need to use a different waveband from the signal light like the beacon light scanning, and does not need an additional beacon light generating device, thereby reducing the weight and volume of the terminal and the complexity of the optical path. Meanwhile, the switching of the small divergence angle light beam during tracking ensures high-precision tracking, and avoids the problems of long scanning time and high missing scanning probability caused by directly using the small divergence angle light beam.

[0118] Please refer to FIG. 6, which is a flowchart of another free space optical communication link establishment method provided in the embodiments of the present application. As shown in FIG. 6, the free space optical communication link establishment method in FIG. 6 is applied to a second terminal, which can also be referred to as a receiving terminal. When applied to the second terminal, the free space optical communication link establishment method provided in the embodiments of the present application includes but is not limited to steps S210 to S270:

[0119] In step S210, a first light beam from a first terminal is received by an optical antenna.

[0120] In step S220, a local first image is formed according to the first light beam.

[0121] In step S230, when the local first image contains a spot, the pointing direction of the optical antenna of the second terminal is adjusted according to the first spot centroid offset corresponding to the local first image.

[0122] In step S240, a first feedback light beam is emitted by the optical antenna, so that the first terminal emits a second light beam according to the first feedback light beam.

[0123] In step S250, the second light beam is received by the optical antenna, a local second image is formed according to the second light beam, and the pointing direction of the optical antenna is adjusted, so that the second spot centroid offset corresponding to the local second image is less than a preset first spot centroid offset threshold.

[0124] In step S260, a second feedback light beam is emitted by the optical antenna, so that the first terminal emits a third light beam according to the second feedback light beam, wherein the divergence angle of the third light beam is smaller than the divergence angles of the first light beam and the second light beam.

[0125] In step S270, the third light beam is received by the optical antenna, and tracking processing is performed according to the third light beam.

[0126] The second terminal adopts a spaceborne acquisition tracking and pointing system provided in the embodiments of the present application, when receiving the light beam transmitted by the first terminal, different operations are performed according to different light beams to complete the link establishment.

[0127] For example, when the second terminal receives the first light beam, a local first image is generated according to the first light beam, if it is detected that the local first image contains a light spot, the boresight of the optical antenna is adjusted to align with the first terminal, and a first feedback light beam is transmitted to the first terminal; the second terminal transmits the first feedback light beam, so that the first terminal transmits a second light beam according to the first feedback light beam, the second terminal receives the second light beam and generates a second local image according to the second light beam, the generated second local image helps the second terminal to adjust the boresight of the optical antenna to further align with the first terminal, so that the second light spot corresponding to the local second image has a centroid offset less than a preset first light spot centroid offset threshold, when the condition is met, a second feedback light beam is transmitted to the first terminal, indicating that the acquisition has been completed and the condition of entering the tracking state is reached; when the first terminal receives the second feedback light beam, a third light beam can be transmitted to the second terminal according to the second feedback light beam, and the second terminal enters the tracking state and performs tracking processing, and the divergence angle of the third light beam used is smaller than that of the first light beam and the second light beam.

[0128] It can be understood that in the embodiments of the present application, the first light beam and the second light beam with large divergence angle enable the first terminal to quickly acquire the second terminal, and the second terminal transmits two feedback signals in the acquisition stage, which are the first feedback light beam and the second feedback light beam, to ensure the accuracy of acquisition, so that the spaceborne ATP system provided in the embodiments of the present application can appropriately increase the exposure time in the acquisition stage, while avoiding adding additional beacon light devices and simplifying the terminal structure volume; after the acquisition is completed, the third light beam with small divergence angle is switched to perform tracking processing, and there is no need to use the light beam with small divergence angle in the acquisition stage, which avoids the problem of long scanning time and large missing scanning probability when directly using the light beam with small divergence angle, and improves the tracking processing precision.

[0129] It can be understood that when the first terminal receives the second feedback light beam, it can be considered that the coarse tracking start condition is reached, the first terminal transmits a third light beam to the second terminal, and correspondingly, the second terminal receives the third light beam from the first terminal and enters the coarse tracking process.

[0130] It should be noted that, in the embodiments of the present application, receiving the third light beam and performing tracking processing according to the third light beam includes but is not limited to: forming a local third image according to the third light beam, adjusting the pointing direction of the optical antenna to make the third spot centroid offset corresponding to the local third image less than a preset second spot centroid offset threshold, and the second spot centroid offset threshold is less than the first spot centroid offset threshold; forming a local fourth image according to the third light beam, and in the case that the local fourth image contains a spot, adjusting the deflection angle of the biaxial piezoelectric fast mirror to make the fourth spot centroid offset corresponding to the local fourth image less than a preset third spot centroid offset threshold, and the third spot centroid offset threshold is less than the second spot centroid offset threshold.

[0131] It should be noted that, in order to ensure the link establishment accuracy before starting communication, the tracking stage is divided into a coarse tracking stage and a fine tracking stage in the embodiments of the present application.

[0132] In the coarse tracking stage, the second terminal forms a local third image according to the third light beam, and adjusts the pointing direction of the optical antenna to make the third spot centroid offset corresponding to the local third image less than a preset second spot centroid offset threshold. At this time, it can be considered that the fine tracking start condition is reached, and the second detector is started to increase the extraction accuracy.

[0133] In the fine tracking stage, the second terminal forms a local fourth image according to the third light beam, and in the case that the local fourth image contains a spot, adjusts the deflection angle of the biaxial piezoelectric fast mirror to make the fourth spot centroid offset corresponding to the local fourth image less than a preset third spot centroid offset threshold. At this time, the exposure time is short, the fine tracking loop bandwidth is high, and the image compensation module is no longer needed to be added. When the fourth spot centroid offset is less than the preset third spot centroid offset threshold, the communication is started.

[0134] It should be noted that, in the fine tracking stage, there may be a case that the platform vibration and satellite attitude adjustment make the fine tracking detector unable to detect the spot. At this time, the fine tracking stage needs to be exited first, and the third light beam is tracked again in the coarse tracking stage. After the fine tracking start condition is reached, i.e., the third spot centroid offset is less than the preset second spot centroid offset threshold, the fine tracking is started again to avoid interference between the coarse tracking and the fine tracking. At the same time, when the spot position is detected in each fine tracking stage, it is also necessary to judge whether the current spot position meets the communication start condition. If not, it is further judged whether the fine tracking start condition is met. If not, the coarse tracking is started again.

[0135] It can be understood that, in the embodiments of the present application, the second terminal includes a first detector and a second detector; the first detector is used to form a local first image according to the first light beam, form a local second image according to the second light beam, and form a local third image according to the third light beam.

[0136] The first spot centroid offset corresponding to the local first image is obtained by the following steps: performing motion compensation on the local first image according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated local first image; and determining the first spot centroid offset according to the gray values of the pixel points in the compensated local first image.

[0137] The process of performing motion compensation on the local first image can be as follows: detecting the motion information of the first detector through an accelerometer and an angular displacement sensor, fusing the motion information of the first detector and the satellite attitude adjustment information to obtain N motion data points, wherein N is an integer greater than 1; inputting the N motion data points into an imaging solution model to obtain a motion trajectory containing N sampling points; and performing motion compensation on the local first image according to the motion trajectory to obtain a compensated local first image.

[0138] The process of determining the first spot centroid offset according to the gray values of the pixel points in the compensated local first image can be as follows: determining an initial centroid position according to the gray values of the pixel points in the compensated local first image; performing interpolation on the pixels in a preset range centered on the initial centroid position to obtain a plurality of sub-pixel points corresponding to the compensated local first image; determining a target centroid position according to the gray values of the sub-pixel points corresponding to the compensated local first image; and determining the first spot centroid offset according to the target centroid position.

[0139] The second spot centroid offset corresponding to the local second image is obtained by the following steps:

[0140] The second spot centroid offset corresponding to the local second image is obtained by the following steps:

[0141] The process of performing motion compensation on the local second image can be as follows: detecting the motion information of the first detector through an accelerometer and an angular displacement sensor, fusing the motion information of the first detector and the satellite attitude adjustment information to obtain N motion data points, wherein N is an integer greater than 1; inputting the N motion data points into an imaging solution model to obtain a motion trajectory containing N sampling points; and performing motion compensation on the local second image according to the motion trajectory to obtain a compensated local second image.

[0142] The process of determining the second light spot centroid offset according to the gray scale values of the pixels in the compensated local second image can be as follows: determining an initial centroid position according to the gray scale values of the pixels in the compensated local second image; performing interpolation on the pixels in a preset range centered on the initial centroid position to obtain a plurality of sub-pixels corresponding to the compensated local second image; determining a target centroid position according to the gray scale values of the sub-pixels corresponding to the compensated local second image; and determining the second light spot centroid offset according to the target centroid position.

[0143] The third light spot centroid offset corresponding to the local third image is obtained through the following steps:

[0144] The local third image is compensated according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated local third image; and the third light spot centroid offset is determined according to the gray scale values of the pixels in the compensated local third image.

[0145] The process of compensating the local third image can be as follows: the motion information of the first detector is detected through an accelerometer and an angular displacement sensor; the motion information of the first detector is fused with the satellite attitude adjustment information to obtain N motion data points, where N is an integer greater than 1; the N motion data points are input into an imaging solution model to obtain a motion trajectory containing N sampling points; and the local third image is compensated according to the motion trajectory to obtain a compensated local third image.

[0146] The process of determining the third light spot centroid offset according to the gray scale values of the pixels in the compensated local third image can be as follows: determining an initial centroid position according to the gray scale values of the pixels in the compensated local third image; performing interpolation on the pixels in a preset range centered on the initial centroid position to obtain a plurality of sub-pixels corresponding to the compensated local third image; determining a target centroid position according to the gray scale values of the sub-pixels corresponding to the compensated local third image; and determining the third light spot centroid offset according to the target centroid position.

[0147] When the local first image, the local second image and the local third image are formed, the exposure time needs to be increased to increase the signal-to-noise ratio of the detector, at which time the participation of the image compensation module is required, and therefore the first detector connected with the image compensation module is used to complete the formation of the local first image, the local second image and the local third image.

[0148] The second detector is configured to form a local fourth image according to the third light beam.

[0149] The fourth light spot centroid offset corresponding to the local fourth image is obtained through the following steps:

[0150] The fourth light spot centroid offset is determined according to the gray scale values of the pixels in the local fourth image.

[0151] The process of motion compensation for the local fourth image can be as follows: detecting motion information of the first detector by the accelerometer and the angular displacement sensor, fusing the motion information of the first detector and satellite attitude adjustment information to obtain N motion data points, wherein N is an integer greater than 1; inputting the N motion data points into an imaging solution model to obtain a motion trajectory containing N sampling points; and performing motion compensation on the local fourth image according to the motion trajectory to obtain a compensated local fourth image.

[0152] The process of determining the fourth light spot centroid offset according to the gray value of the pixel point in the compensated local fourth image can be as follows: determining an initial centroid position according to the gray value of each pixel point in the compensated local fourth image; performing interpolation on the pixels in a preset range centered on the initial centroid position to obtain a plurality of sub-pixel points corresponding to the compensated local fourth image; determining a target centroid position according to the gray value of each of the sub-pixel points corresponding to the compensated local fourth image; and determining the fourth light spot centroid offset according to the target centroid position.

[0153] As shown in FIG. 3, the first detector is connected with the image compensation module, the image compensation module is connected with the light spot position determination module, and the second detector is directly connected with the light spot position determination module. In the case that the third light spot centroid offset corresponding to the local third image is less than a preset second light spot centroid offset threshold, the tracking is performed through the second detector at this time because the exposure time is short and the bandwidth of the fine tracking loop is high, and the image compensation module is no longer needed to participate.

[0154] Please refer to FIG. 7, which is a flowchart of a free space optical communication link establishment method provided by the embodiment of the present application. As shown in FIG. 7, when the communication link establishment is needed, the following steps are completed: the first terminal and the second terminal complete the initial pointing to an uncertain area, the initial scanning and capturing area includes a plurality of scanning points, the first terminal serves as a transmitting terminal, and the second terminal serves as a receiving terminal; the first terminal first transmits a first light beam through its own optical antenna, and scans the uncertain area through the first light beam standing point, at this time, the first light beam used is a large divergence angle light beam; the second terminal receives the first light beam through its own optical antenna, and detects the light spot image through its own first detector, that is, detects whether the imaging of the first light beam contains a light spot, if it contains a light spot, outputs a local first image containing a light spot (denoted as image b1); the second terminal performs motion compensation on the image b1 according to the motion information of its own first detector and the satellite attitude adjustment information, obtains a compensated image b1, determines a light spot centroid offset S b1 according to the gray value of the pixel point in the compensated image b1, and adjusts the boresight pointing of its own optical antenna according to S b1 The second terminal transmits a first feedback light beam to the first terminal through its own optical antenna.

[0155] It should be noted that if the second terminal does not detect the spot image, the first feedback light beam is not emitted; if the first terminal still does not receive the first feedback light beam after the residence time of the current scanning point reaches the preset time, the next scanning point is traversed.

[0156] After the first terminal receives the first feedback light beam, the scanning of the uncertain area is stopped, a local first image (denoted as image a1) is formed by the first detector of the first terminal according to the first feedback light beam, the first terminal performs motion compensation on the image a1 according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated image a1, and the spot centroid offset S a1 is determined according to the gray value of each pixel point in the compensated image a1. a1 The boresight direction of the optical antenna of the first terminal is adjusted, and the second light beam with a large divergence angle is maintained to be emitted through the optical antenna, and the first terminal is gazed at this time.

[0157] The second light beam is received by the optical antenna of the second terminal, and a local second image (denoted as image b2) is formed by the first detector of the second terminal according to the second light beam, and the image b2 is motion compensated according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated image b2; the spot centroid offset S b2 is determined according to the gray value of each pixel point in the compensated image b2. b2 The boresight direction of the optical antenna of the second terminal is adjusted so that the spot centroid offset S b2 is less than a preset first spot centroid offset threshold.

[0158] When the spot centroid offset S b2 is less than the preset first spot centroid offset threshold, it is determined that the coarse tracking opening condition is met, and the second terminal sends a second feedback light beam to the first terminal.

[0159] After the first terminal receives the second feedback light beam, it is determined that the acquisition is completed, and the coarse tracking stage can be entered.

[0160] After the acquisition is completed, the first terminal emits a third light beam with a small divergence angle to the second terminal to start the coarse tracking.

[0161] The third light beam is received by the optical antenna of the second terminal, a local third image (denoted as image b3) is formed by the first detector of the second terminal according to the third light beam, and the boresight direction of the optical antenna of the second terminal is adjusted so that the spot centroid offset S b3 corresponding to the image b3 is less than a preset second spot centroid offset threshold, at this time, the image compensation module can be opened to perform motion compensation on the image b3 to increase the extraction accuracy. b3If the second spot centroid offset is less than a preset second spot centroid offset threshold, it is determined that the fine tracking opening condition is met, and if the fine tracking opening condition is not met, the second terminal optical antenna visual axis direction is continuously adjusted.

[0162] After the fine tracking opening condition is met, the second terminal forms a local fourth image (denoted as image b4) according to the third light beam. If the image b4 contains a spot, the deflection angle of the biaxial piezoelectric fast mirror is adjusted so that the spot centroid offset S b4 If the third spot centroid offset is less than a preset third spot centroid offset threshold, the exposure time is short, the fine tracking loop bandwidth is high, and the image compensation module no longer needs to be added. When the spot centroid offset S b4 If the third spot centroid offset is less than a preset third spot centroid offset threshold, it is considered that the communication condition is met, the optical communication link is established, and communication is started.

[0163] If the communication condition is not met, it is detected again whether the image b4 contains a spot. When the spot image cannot be detected, the fine tracking stage is exited and the visual axis direction is adjusted again in the coarse tracking stage.

[0164] Through the flow of FIG. 7, the technical effects of reducing power consumption, improving communication link establishment efficiency, and ensuring stability after the line is established can be achieved by using a light beam with an adjustable divergence angle to establish a communication link.

[0165] The embodiment of the present application also provides an electronic device, as shown in FIG. 9, the electronic device 1400 includes:

[0166] One or more processors 1410; a memory 1420, on which one or more programs are stored, when the one or more programs are executed by the one or more processors 1410, the one or more processors 1410 implement the application embodiment provided application for the first terminal free space optical communication link establishment method, or, application for the second terminal free space optical communication link establishment method.

[0167] The memory 1420 as a kind of non-transient network system, it can be used to store non-transient software programs and non-transient computer executable programs.In addition, the memory 1420 can include high-speed random access memory, and can also include non-transient memory, such as at least one magnetic disk storage device, flash memory device or other non-transient solid-state memory device.In some embodiments, the memory 1420 can optionally include a memory 1420 remotely arranged relative to the processor 1410, and these remote memories 1420 can be connected to the processor 1410 through a network.The above-mentioned network examples include but are not limited to the Internet, intranet, local area network, mobile communication network and combination thereof.

[0168] The memory 1420 can be implemented in the form of a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM), etc. The memory 1420 can store an operating system and other application programs. When the technical solutions provided in the embodiments of the present specification are implemented by software or firmware, the related program codes are stored in the memory 1420 and are invoked and executed by the processor 1410 to implement the method of the embodiments of the present application.

[0169] The processor 1410 can be implemented in the form of a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, etc., for executing related programs to implement the technical solutions provided in the embodiments of the present application.

[0170] In some embodiments, the electronic device further includes an input / output interface for realizing information input and output, a communication interface for realizing communication interaction between the device and other devices, which can realize communication through wired means (such as USB, network cable, etc.) or through wireless means (such as mobile network, WIFI, Bluetooth, etc.), a bus for transmitting information between various components (such as the processor 1410, the memory 1420, the input / output interface, and the communication interface) of the device, and wherein the processor 1410, the memory 1420, the input / output interface, and the communication interface can realize communication connection between each other inside the device through the bus.

[0171] An embodiment of the present application further provides a computer readable storage medium storing computer executable instructions for implementing the free space optical communication link establishment method applied to the first terminal or the free space optical communication link establishment method applied to the second terminal provided in the embodiments of the present application.

[0172] An embodiment of the present application further provides a computer program product including a computer program or computer instructions stored in a computer readable storage medium, wherein a processor of a computer device reads the computer program or computer instructions from the computer readable storage medium, and the processor executes the computer program or computer instructions to enable the computer device to implement the free space optical communication link establishment method applied to the first terminal or the free space optical communication link establishment method applied to the second terminal provided in the embodiments of the present application.

[0173] The system architecture and application scenarios described in the embodiments of the present application are for more clearly illustrating the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. Those skilled in the art can know that, with the evolution of system architecture and the appearance of new application scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0174] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer readable storage medium, and when the computer program is executed, the computer program can include the processes of the above-mentioned embodiments. In the embodiments of the present application, any reference to memory, storage, database or other medium can include non-volatile and / or volatile memory. The non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. The volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not as a limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0175] Those of ordinary skill in the art will appreciate that all or some steps, systems of the above-disclosed methods can be implemented as software, firmware, hardware, or any suitable combination thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or as hardware, or as an integrated circuit, such as an application- specific integrated circuit. Such software can be distributed on computer readable media, which can comprise computer storage media (or non-transitory media) and communication media (or transitory media). As is well known to those of ordinary skill in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Further, it should be appreciated by those skilled in the art that computer storage media generally can embody computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media.

[0176] It should be understood that, in this application, "at least one" means one or more, "multiple" means two or more. "And / or" is used to describe the association relationship of the associated objects, which means that there can be three relationships, for example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally represents that the associated objects before and after are in an "or" relationship. "At least one of the following" or the like means any combination of these items, including single item or any combination of multiple items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0177] The above describes some embodiments of the present application with reference to the accompanying drawings, but does not limit the scope of the present application. Any modifications, equivalent replacements and improvements made by those skilled in the art without departing from the scope and essence of the present application shall be within the scope of the present application.

Claims

1. A spaceborne acquisition, tracking and targeting system, wherein: include: An optical antenna, a laser generating module, a first detector, a light spot position extraction module, a first tracking controller and a first tracking actuator; The optical antenna is used to transmit or receive a light beam; The laser generating module is used to output a light beam to the optical antenna for transmission, and is also used to adjust the divergence angle of the output light beam; The first detector is configured to form an image based on the received light beam, determine whether the image contains a light spot, and output a first light spot image to the light spot position determination module if it is determined that the image contains a light spot; The light spot position determination module is configured to determine a first light spot centroid offset according to the first light spot image; The first tracking controller is used to control the first tracking actuator to adjust the visual axis direction of the optical antenna according to the first light spot centroid offset.

2. The system according to claim 1, wherein: Also included is an image compensation module; The image compensation module is used to perform motion compensation on the first light spot image according to the motion information of the first detector and the satellite attitude adjustment information, and output a second light spot image to the light spot position determination module, so that the light spot position determination module determines the first light spot centroid offset according to the second light spot image.

3. The system according to claim 2, wherein: The image compensation module is specifically used for: Fusing the motion information of the first detector and the satellite attitude adjustment information to obtain N motion data points, where N is an integer greater than 1; Inputting the N motion data points into an imaging solution model to obtain a motion trajectory containing N sampling points; Motion compensation is performed on the first light spot image according to the motion trajectory to obtain the second light spot image.

4. The system according to claim 2, wherein: Also includes accelerometers and angular displacement sensors; The accelerometer is used to detect acceleration information of the first detector; The angular displacement sensor is used to detect the angular displacement information of the first detector; The motion information of the first detector includes the acceleration information and the angular displacement information.

5. The system according to claim 3, wherein: The light spot position determination module is specifically used for: Acquire all target pixels whose grayscale values ​​are lower than a preset grayscale threshold in the second light spot image, and set the grayscale values ​​of the target pixels to 0, to obtain a third light spot image; Determining a first initial centroid position according to the grayscale value of each pixel in the third light spot image; Interpolating pixels within a preset range centered at the first initial centroid position to obtain a plurality of sub-pixel points corresponding to the third light spot image; Determining a first target centroid position according to the grayscale values ​​of each of the sub-pixel points corresponding to the third light spot image; The first light spot center of mass offset is determined according to the first target center of mass position.

6. The system according to claim 1, wherein: The system further includes a biaxial piezoelectric fast reflector, a first beam splitter, a second beam splitter, a second detector, a beam receiver, and a second tracking controller; The dual-axis piezoelectric fast-reflecting mirror is used to transmit the light beam received by the optical antenna to the first beam splitter; The first beam splitter is used to split the received light beam into two light beams, the first light beam is transmitted to the first detector, and the second light beam is transmitted to the second beam splitter; The second beam splitter is used to split the received light beam into two light beams, the first light beam is transmitted to the light beam receiver, and the second light beam is transmitted to the second detector; the second detector is configured to be turned on when the first light spot centroid offset is less than a third light spot centroid offset threshold, form an image based on the received light beam, determine whether the image contains a light spot, and output a fourth light spot image to the light spot position determination module if it is determined that the image contains a light spot; The light spot position determination module is further configured to determine a centroid offset of the second light spot according to the fourth light spot image; The second tracking controller is used to control the deflection of the dual-axis piezoelectric fast reflection mirror to adjust the path of the received light beam according to the offset of the center of mass of the second light spot.

7. The system according to claim 6, wherein: The light spot position determination module is specifically used for: Acquire all target pixel points whose grayscale values ​​are lower than a preset grayscale threshold in the fourth light spot image, and set the grayscale values ​​of the target pixel points to 0, to obtain a fifth light spot image; determining a second initial centroid position according to the grayscale value of each pixel in the fifth light spot image; interpolating pixels within a preset range centered at the second initial centroid position to obtain a plurality of sub-pixel points of the fifth light spot image; determining a second target centroid position according to the grayscale values ​​of the sub-pixel points corresponding to the fifth light spot image; The second light spot center of mass offset is determined according to the second target center of mass position.

8. A free-space optical communication link establishment method, applied to a first terminal, the method comprising: Determining an initial scanning capture area, wherein the initial scanning capture area includes a plurality of scanning points; Traversing scanning points in the initial scanning capture area, and emitting a first light beam through an optical antenna according to the direction of the currently traversed scanning point; upon receiving a first feedback light beam emitted by a second terminal according to the first light beam, ending the traversal of scanning points in the initial scanning capture area; forming a local first image according to the first feedback beam, adjusting the optical antenna line of sight direction according to the first light spot centroid offset corresponding to the local first image, and emitting a second light beam through the optical antenna, so that the second terminal emits a second feedback beam according to the second light beam; When the second feedback beam is received, a third beam is emitted through the optical antenna so that the second terminal performs tracking processing according to the third beam, wherein the divergence angle of the third beam is smaller than the divergence angles of the first beam and the second beam.

9. The method according to claim 8, wherein The first terminal includes a first detector, which is used to form the local first image according to the first feedback light beam; the first light spot centroid offset corresponding to the local first image is obtained by the following steps: performing motion compensation on the local first image according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated local first image; The first light spot centroid offset is determined according to the grayscale value of the pixel in the compensated local first image.

10. The method according to claim 8, wherein The emitting a first light beam according to the direction of the currently traversed scanning point includes: Stay at the currently traversed scanning point according to a preset dwell time; During the dwell time, the first light beam is emitted toward the direction of the scanning point currently traversed.

11. A free-space optical communication link establishment method, applied to a second terminal, the method comprising: receiving a first light beam from a first terminal via an optical antenna; forming a local first image according to the first light beam; In a case where the local first image contains a light spot, adjusting the visual axis direction of the own optical antenna according to the centroid offset of the first light spot corresponding to the local first image; emitting a first feedback light beam through the optical antenna, so that the first terminal emits a second light beam according to the first feedback light beam; receiving the second light beam through the optical antenna, forming a local second image according to the second light beam, and adjusting the visual axis direction of the optical antenna so that the centroid offset of the second light spot corresponding to the local second image is less than a preset centroid offset threshold of the first light spot; emitting a second feedback light beam through the optical antenna, so that the first terminal emits a third light beam according to the second feedback light beam, wherein a divergence angle of the third light beam is smaller than divergence angles of the first light beam and the second light beam; The third light beam is received by the optical antenna, and tracking processing is performed according to the third light beam.

12. The method according to claim 11, wherein The tracking process according to the third light beam includes: Forming a local third image according to the third light beam, adjusting the direction of the optical antenna's own optical axis so that a third light spot centroid offset corresponding to the local third image is less than a preset second light spot centroid offset threshold, and the second light spot centroid offset threshold is less than the first light spot centroid offset threshold; A local fourth image is formed according to the third light beam. When the local fourth image contains a light spot, the deflection angle of the dual-axis piezoelectric fast-reflection mirror is adjusted so that the center-of-mass offset of the fourth light spot corresponding to the local fourth image is less than a preset third light spot center-of-mass offset threshold, and the third light spot center-of-mass offset threshold is less than the second light spot center-of-mass offset threshold.

13. The method according to claim 11, wherein: The second terminal includes a first detector; The first detector is configured to form the local first image according to the first light beam; The first detector is further configured to form the local second image according to the second light beam; The first detector is further configured to form a local third image according to the third light beam.

14. The method according to claim 13, wherein The first light spot centroid offset corresponding to the local first image is obtained by the following steps: performing motion compensation on the local first image according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated local first image; and determining the first light spot centroid offset according to the grayscale value of the pixel point in the compensated local first image; The second light spot centroid offset corresponding to the local second image is obtained by the following steps: performing motion compensation on the local second image according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated local second image; and determining the second light spot centroid offset according to the grayscale value of the pixel point in the compensated local second image; The centroid offset of the third light spot corresponding to the local third image is obtained by the following steps: performing motion compensation on the local third image according to the motion information of the first detector and the satellite attitude adjustment information to obtain a compensated local third image; and determining the centroid offset of the third light spot according to the grayscale value of the pixel point in the compensated local third image.

15. The method according to claim 12, wherein: The second terminal includes a second detector; the second detector is configured to form the local fourth image according to the third light beam; The fourth light spot centroid offset corresponding to the local fourth image is obtained by the following steps: determining the fourth light spot centroid offset according to the grayscale value of the pixel point in the local fourth image.

16. The method according to claim 15, wherein The second detector is turned on when the third light spot centroid offset corresponding to the local third image is less than a preset second light spot centroid offset threshold.

17. An electronic device comprising: one or more processors; A memory having one or more programs stored thereon, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement: the method according to any one of claims 8 to 10, or the method according to any one of claims 11 to 16.

18. A computer-readable storage medium having a computer program stored thereon, wherein when the program is executed by a processor, the method according to any one of claims 8 to 10 is implemented, or the method according to any one of claims 11 to 16 is implemented.

19. A computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the computer program implements: the method according to any one of claims 8 to 10, or the method according to any one of claims 11 to 16.

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