Satellite-borne capturing, tracking and aiming system and free space optical communication link establishing method

Abstract

The invention provides a satellite-borne capturing, tracking and aiming system and a free space optical communication link establishing method. The system comprises an optical antenna, a laser generating module, a first detector, a light spot position extracting module, a first tracking controller and a first tracking executing mechanism. And when the terminal establishes a link, the first terminal traverses the scanning points in the initial scanning capture area, and emits a first light beam according to the direction of the currently traversed scanning points. And when the first feedback light beam emitted by the second terminal is received, the first terminal adjusts the direction of the optical axis of the optical antenna. And the first terminal transmits a second beam through the optical antenna and receives a second feedback beam transmitted by the second terminal according to the second beam. And when the second feedback light beam is received, the first terminal transmits a third light beam through the optical antenna, so that the second terminal performs tracking processing according to the third light beam. According to the embodiment of the invention, a scanning capture mode based on the signal light with the adjustable divergence angle is adopted, the size and development cost of the laser communication terminal are reduced, and the link establishment time is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, and in particular to a spaceborne acquisition, tracking and pointing system and a free space optical communication link establishment method. BACKGROUND

[0002] Free space optical communication (FSO) is a communication mode taking free space as a transmission channel, and has the advantages of high code rate, high bandwidth and flexibility. An acquisition, tracking and pointing (ATP) system is the most important subsystem in free space laser communication, and completes functions of laser scanning acquisition, coarse tracking and fine tracking, and is used for establishing and maintaining an optical communication link.

[0003] The scanning acquisition stage is an initial stage of establishing a link between two communication terminals. Currently, a traditional scanning method can be divided into two modes: beacon light scanning and beaconless light scanning. The beacon light scanning is used more frequently, 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, and a laser generator with large power is required. In addition, the beacon light generally uses a different waveband from the signal light, and an additional beacon light generating device is required, which increases the weight and volume of the terminal and the complexity of the optical path, thereby increasing the implementation cost.

[0004] In order to reduce power consumption and realize the design concept of miniaturization, the beaconless light scanning method is proposed. This method directly uses the signal light for scanning, and does not require an additional beacon light component, thereby reducing the development and launch cost. However, the divergence angle of the signal light is small, and there are problems of long scanning time and high probability of missing scanning, and the satellite attitude change and platform vibration are more sensitive.

[0005] How to improve the scanning acquisition precision of the ATP system under the premise of considering low power consumption, low cost and miniaturization of the ATP system is a technical problem to be solved. SUMMARY

[0006] Embodiments of the present application provide a spaceborne acquisition, tracking and pointing system and a free space optical communication link establishment method, and are used for solving the technical problem of how to improve the scanning acquisition precision of the ATP system under the premise of considering low power consumption, low cost and miniaturization of the ATP system.

[0007] In a first aspect, the embodiments of the present application provide a spaceborne acquisition, tracking and pointing system, which comprises an optical antenna, a laser generating module, a first detector, a light spot position extraction module, a first tracking controller and a first tracking execution mechanism.

[0008] The optical antenna is configured to transmit or receive a light beam.

[0009] The laser generating module is configured to output a light beam to the optical antenna for emission and to adjust a divergence angle of the output light beam.

[0010] The first detector is configured to form an image according to the received light beam, to determine whether the image contains a light spot, and to output a first light spot image to the light spot position determination module if the image contains the light spot.

[0011] The light spot position determination module is configured to determine a first light spot centroid offset according to the first light spot image.

[0012] 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 light spot centroid offset.

[0013] In a second aspect, an embodiment of the present application provides a free space optical communication link establishment method, applied to a first terminal, and the method comprises the following steps.

[0014] Determining an initial scanning and capturing area, wherein the initial scanning and capturing area comprises a plurality of scanning points.

[0015] Traversing the scanning points in the initial scanning and capturing area, and emitting a first light beam through an optical antenna according to a pointing direction of a currently traversed scanning point.

[0016] Ending the traversal of the scanning points in the initial scanning and capturing area if a first feedback light beam emitted by a second terminal according to the first light beam is received.

[0017] Forming a local first image according to the first feedback light beam, adjusting a boresight direction of the optical antenna according to a 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.

[0018] Receiving the second feedback light beam, and emitting 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.

[0019] In a third aspect, an embodiment of the present application provides a free space optical communication link establishment method, applied to a second terminal, and the method comprises the following steps.

[0020] Receiving a first light beam from a first terminal through an optical antenna.

[0021] Forming a local first image according to the first light beam.

[0022] In a case where the local first image contains a light spot, the optical antenna adjusts the pointing direction of the optical antenna according to a first light spot centroid offset corresponding to the local first image;

[0023] The optical antenna transmits a first feedback light beam, so that the first terminal transmits a second light beam according to the first feedback light beam;

[0024] The optical antenna receives the second light beam, forms a local second image according to the second light beam, and adjusts the pointing direction of the optical antenna, so that a second light spot centroid offset corresponding to the local second image is less than a preset first light spot centroid offset threshold;

[0025] The optical antenna transmits a second feedback light beam, so that the first terminal transmits a third light beam according to the second feedback light beam, where a divergence angle of the third light beam is less than divergence angles of the first light beam and the second light beam;

[0026] The optical antenna receives the third light beam and performs tracking processing according to the third light beam.

[0027] In a fourth aspect, an electronic device is provided, and the electronic device includes:

[0028] One or more processors;

[0029] 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 according to the second aspect or the third aspect.

[0030] In a fifth aspect, a computer readable storage medium is provided, and the computer readable storage medium has a computer program stored thereon, when the computer program is executed by a processor, the computer program implements the free space optical communication link establishment method according to the second aspect or the third aspect.

[0031] In a sixth aspect, a computer program product is provided, and the computer program product includes a computer program, when the computer program is executed by a processor, the computer program implements the free space optical communication link establishment method according to the second aspect or the third aspect.

[0032] The embodiment of the application provides a spaceborne ATP system and a free space optical communication link establishment method, wherein the ATP system comprises an optical antenna, a laser generating module, a first detector, a light spot position extraction module, a first tracking controller and a first tracking execution mechanism. When a terminal establishes a link, a first terminal first determines an initial scanning and capturing area, traverses a scanning point in the initial scanning and capturing area, and emits a first light beam according to the pointing of the scanning point currently traversed. When a first feedback light beam emitted by a second terminal is received, the first terminal ends the traversal of the scanning point, forms a local first image according to the first feedback light beam, adjusts the pointing of the optical antenna visual axis according to a first light spot centroid offset corresponding to the local first image, so as to complete preliminary scanning and capturing confirmation and align the pointing of the optical antenna visual axis of the first terminal to the second terminal on the receiving side. The first terminal emits a second light beam through the optical antenna, receives a second feedback light beam emitted by the second terminal according to the second light beam, and completes further scanning and capturing confirmation based on the second feedback light beam. When the second feedback light beam is received, the first terminal emits a third light beam through the optical antenna, so that the second terminal performs tracking processing according to the third light beam, and improves the detection accuracy of the light spot of the terminal on the receiving side. The embodiment of the application adopts a scanning and capturing mode based on a signal light with adjustable divergence angle, the first light beam and the second light beam are large-divergence-angle signal lights, and the third light beam is a small-divergence-angle signal light. The scanning is performed by using the large-divergence-angle signal light instead of the beacon light, the volume and development cost of the laser communication terminal are reduced, and the link establishment time is shortened. Meanwhile, the terminal positioning is performed by using twice feedback light in the scanning process, the visual axis is further aligned, and the coarse tracking time is reduced. The embodiment of the application improves the scanning and capturing accuracy of the ATP system while taking into account the low power consumption, low cost and miniaturization of the ATP system. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A structural schematic diagram of an ATP system provided by the embodiment of the application is provided.

[0034] Figure 2 A working principle schematic diagram of an image compensation module provided by the embodiment of the application is provided.

[0035] Figure 3 A structural schematic diagram of an ATP system provided by the embodiment of the application is provided.

[0036] Figure 4 A working principle diagram of an ATP system provided by the embodiment of the application is provided.

[0037] Figure 5 A flowchart of a free space optical communication link establishment method provided by the embodiment of the application is provided.

[0038] Figure 6 A flowchart of another free space optical communication link establishment method provided by the embodiment of the application is provided.

[0039] Figure 7 A flowchart of a free space optical communication link establishment method provided by an embodiment of the present application is shown in FIG. 1.

[0040] Figure 8 A comparison diagram of a first light spot image and a second light spot image provided by an embodiment of the present application is shown in FIG. 2.

[0041] Figure 9 A structural diagram of an electronic device provided by an embodiment of the present application is shown in FIG. 3.

[0042] Explanation of reference signs

[0043] 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 - gimbals. DETAILED DESCRIPTION

[0044] In order to enable 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.

[0045] 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 being 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 in the art.

[0046] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] To facilitate better understanding of the solutions of the embodiments of the present application, the related art will be introduced first as follows.

[0051] 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.

[0052] 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 establishment speed and success rate of 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.

[0053] 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.

[0054] 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.

[0055] 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 terminal, resulting in insufficient scanning accuracy.

[0056] In order to provide a spaceborne capture tracking and aiming system and a free space optical communication link establishment method that reduces power consumption, improves communication link establishment efficiency, and ensures stability after the link is established, the embodiments of the present application provide a spaceborne capture tracking and aiming system (hereinafter referred to as ATP system) and a free space optical communication link establishment method.

[0057] Please refer to Figure 1 The structure diagram of a spaceborne capture tracking and aiming system (hereinafter referred to as ATP system) provided by the embodiments of the present application is shown in Figure 1 In the embodiments of the present 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.

[0058] The optical antenna is used to transmit or receive a light beam.

[0059] 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.

[0060] The first detector is used to form an image according to the received light beam, determine whether the image contains a spot, and output a first spot image to the spot position determination module in the case that the image contains a spot.

[0061] The spot position determination module is used to determine a first spot centroid offset amount according to the first spot image.

[0062] The first tracking controller is used to control the first tracking execution mechanism to adjust the boresight direction of the optical antenna according to the first spot centroid offset amount.

[0063] It can be understood that the laser generating module can output a light beam, and the divergence angle of the output light beam can be adjusted, and the laser generating module sends the light beam with adjustable divergence angle to the optical antenna for emission, so that the ATP system has the technical effect that the divergence angle of the emitted light beam is adjustable.

[0064] 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, and 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, and 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, i.e. 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.

[0065] For example, when the ATP system is used as a transmitting terminal, the laser generating module is connected to the optical antenna, and when the transmitting terminal needs to emit a light beam, the laser generating module outputs a light beam with a specific divergence angle to the optical antenna, and then the optical antenna emits the light beam. When the ATP system is used as a receiving terminal, the first detector forms an image according to the received light beam and determines whether there is a light spot in the image when the optical antenna receives a light beam, and if there is a light spot, the first detector sends a first light spot image formed according to the received light beam to the spot position determining module, and the spot position determining module determines a first light spot centroid offset according to the first light spot image, and 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 to track the opposite terminal.

[0066] The ATP system provided by the embodiments of the present application outputs signal light with adjustable divergence angle for communication link establishment, which can use signal light with large divergence angle 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, and on the other hand, can use signal light with small divergence angle for scanning to realize high-precision link establishment and ensure the stability after the line is established.

[0067] 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 emitted by the optical antenna. In the process of free space optical communication link establishment, a larger divergence angle (generally more than tens of micro-radians) is referred to as a large divergence angle, and a smaller divergence angle (generally a few micro-radians) is referred to as a small divergence angle.

[0068] In the embodiment 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 configured to perform motion compensation on the first spot image according to the motion information of the first detector and the satellite attitude adjustment information, so as to output a second spot image to the spot position determination module. The spot position determination module determines the first spot centroid offset amount according to the second spot image, and the first tracking controller controls the first tracking actuator to adjust the optical antenna boresight by referring to the first spot centroid offset amount.

[0069] For example, refer to Figure 2 The working principle of the image compensation module provided in the embodiment of the present application is shown in FIG. 2. Figure 2 As shown in FIG. 2, the image compensation module works as follows:

[0070] Fusing the motion information of the first detector and the satellite attitude adjustment information, N motion data points are obtained, wherein N is an integer greater than 1.

[0071] The N motion data points are input into an imaging calculation model to obtain a motion trajectory containing N sampling points.

[0072] The first spot image is motion compensated according to the motion trajectory to obtain a second spot image.

[0073] When the image compensation module is added, the first spot centroid offset amount is determined by the second spot image generated by the image compensation module. The system can compensate for the spot image degradation caused by the motion of the boresight, compensate for the influence of the platform vibration at the receiving end, and improve the spot detection accuracy.

[0074] 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.

[0075] The ATP system further includes an accelerometer and an angular displacement sensor. The accelerometer is configured to detect the linear displacement information of the first detector, and the angular displacement sensor is configured to detect the angular displacement information of the first detector.

[0076] 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. The three accelerometers are mutually orthogonal and installed on the gimbal to measure the linear displacement in the three-axis direction of the space.

[0077] In the embodiment of the present application, the attitude adjustment of the optical antenna is realized by using the gimbal, so that the optical antenna boresight is aligned with the transmitting terminal.

[0078] It can be understood that the present application adds an image compensation module before extracting the centroid of the spot image in order to compensate for the spot image tailing or ghosting phenomenon caused by the image point displacement caused by the visual axis jitter, remove the interference of the terminal vibration on the spot image during imaging, and make the subsequent spot position extraction have higher accuracy.

[0079] It should be noted that after fusing the satellite attitude adjustment information with the motion information of the first detector, the terminal's line of sight jitter information is obtained (containing N motion data points. The larger N is, the more accurate the jitter information is obtained. The value of N needs to take into account the actual computing power and the allowable solution time). The imaging solution model is combined with N motion data points to solve the movement trajectory of the image points on the first detector's image plane, and then further establish the point spread function. The imaging solution model can be calibrated in advance on the ground.

[0080] For example, in one embodiment of the present application, the process of establishing the point spread function is as follows:

[0081] Assume the exposure time of the first detector is T. Under ideal circumstances, an ideal light point in three-dimensional space passes through the optical antenna and forms an image at the first detector point. However, the terminal's line of sight jitter causes this image point to be "smeared" on the image plane, degrading image quality. Data from the satellite and platform sensors are fused to obtain N data points of the light point's motion relative to the line of sight during the exposure time. After applying the imaging solution model, the image point's trajectory on the image plane is obtained, which also has N sampling points.

[0082] Assume that the energy left by the light point on the image plane is E. The image point is considered to move at a constant speed between adjacent sampling points. Then the photon energy obtained by a certain pixel on the moving trajectory is proportional to the time the image point stays at that pixel. The number of sampling points on each pixel can be used to approximately replace the residence time. For example, if n1 sampling points fall on a certain pixel on the trajectory, the light energy ΔE obtained by the pixel is:

[0083]

[0084] Calculate the light energy obtained by each pixel on the trajectory in turn. Let the light energy of the pixel with coordinates (i, j) on the trajectory be ΔE(i, J). Normalize the energy on each pixel to obtain the point spread function:

[0085]

[0086] After obtaining the point spread function, a non-blind image restoration algorithm can be further selected to solve the optimal clear image. Classic non-blind image restoration algorithms include Wiener filtering, Richardson-Lucy regularization algorithm, total variation (TV) regularization algorithm, etc. In addition, neural network algorithms have also achieved good results in the field of image restoration, but require a large amount of training data and are not suitable for the aerospace field. The embodiment of the present application does not limit the choice of algorithm for solving the optimal clear image.

[0087] The TV regularization algorithm has better restoration effect on vibration-degraded images than the other two algorithms. Considering the sparsity of the spot image, the anisotropic TV / L2 model can be used for prior constraints, and the point spread function and the clear spot image can be estimated alternately to improve the restoration effect.

[0088] Compared with the first spot image, the noise of the second spot image obtained after algorithm compensation is significantly suppressed and the visual axis jitter is compensated. Figure 8 As shown, a is the first spot image, and b is the second spot image. It can be clearly seen that the second spot image after algorithm compensation is clearer than the first spot image.

[0089] After the second spot image is obtained, the second spot image is sent to the spot position determination module. The spot position determination module determines the centroid offset of the first spot according to the second spot image. The specific functions of the spot position determination module are as follows:

[0090] Obtain all target pixel points whose grayscale values ​​are lower than a preset grayscale threshold in the second light spot image, and set the grayscale values ​​of the target pixel points to 0 to obtain a third light spot image;

[0091] Determining a first initial centroid position according to the grayscale value of each pixel in the third light spot image;

[0092] Interpolate 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;

[0093] Determine the target centroid position according to the grayscale value of each sub-pixel point corresponding to the third light spot image;

[0094] According to the target centroid position, the centroid offset of the first light spot is determined.

[0095] In a specific embodiment of the present application, the process of determining the first light spot centroid offset by the light spot position determination module is as follows:

[0096] After the light spot position determination module obtains the second light spot image, it first pre-processes the second light spot image, sets a preset grayscale threshold T, sets the grayscale values ​​below T in the second light spot image to 0, reduces interference, and obtains the third light spot image. The formula is as follows:

[0097]

[0098] wherein (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.

[0099] 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 barycenter method, and the like. For a diffused and broken light spot, the circle fitting method has poor accuracy; the Hough algorithm has high reliability and 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 barycenter method are more suitable for the case of wireless laser communication, and one of them can be selected as the first initial barycenter position extraction algorithm, and the specific selection of the first initial barycenter position algorithm is not limited in the present application.

[0100] Taking the barycenter method for extracting the first initial barycenter position as an example, the barycenter method is to use the gray value of a pixel as a weight to calculate the barycenter of the light spot, so as to improve the calculation speed. Assuming that the picture size is M x N, and the gray value of each pixel point is f(m, n), the calculation formula of the first initial barycenter position (m', n') is as follows:

[0101]

[0102] After obtaining the first initial barycenter position (m', n'), the pixels in a preset range centered on the first initial barycenter position (m', n') are interpolated to obtain a plurality of sub-pixel points corresponding to the third light spot image. The barycenter position is recalculated by using the interpolated sub-pixel points through formula 4 to obtain the first target barycenter position. It should be understood that the light spot position determination module uses the above method to calculate the barycenter position of the light spot, which can improve the detection accuracy of the barycenter position of the light spot.

[0103] After the first target barycenter position is determined, the first light spot barycenter offset can be calculated according to the first target barycenter position.

[0104] The first light spot barycenter 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 barycenter offset to establish a communication link. Exemplarily, the first tracking execution mechanism is a gimbal.

[0105] 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 barycenter offset, aiming to make the light spot of the received light beam image on the center of the first detector as much as possible.

[0106] It should be noted that the ATP system provided in the embodiments of the present application further comprises a biaxial piezoelectric fast mirror, a first beam splitter, a second beam splitter, a second detector, a beam receiver and a second tracking controller.

[0107] The biaxial piezoelectric fast mirror is configured to transmit the light beam received by the optical antenna to the first beam splitter.

[0108] The first beam splitter is configured to split the received light beam into two light beams, a first light beam is transmitted to the first detector, and a second light beam is transmitted to the second beam splitter.

[0109] The second beam splitter is configured to split the received light beam into two light beams, a first light beam is transmitted to the beam receiver, and a second light beam is transmitted to the second detector.

[0110] The second detector is configured to be turned on when the first spot centroid offset is less than the third spot centroid offset threshold, form an image according to the received light beam, determine whether the image contains a spot, and output a fourth spot image to the spot position determination module in the case that the image contains a spot.

[0111] The spot position determination module is further configured to determine the second spot centroid offset according to the fourth spot image.

[0112] The second tracking controller is configured to control the biaxial piezoelectric fast mirror to deflect to adjust the path of the received light beam according to the second spot centroid offset.

[0113] It should be noted that in the embodiments of the present application, the light beam enters the first beam splitter through the biaxial piezoelectric fast mirror, and is split into two light beams after being split by 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 beam receiver and the second detector respectively, the light beam position meets 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 beam receiver.

[0114] For example, refer to Figure 3 FIG. 1 is a schematic diagram of an ATP system provided in the embodiments of the present application, as Figure 3 shown, in the figure, 1 is an optical antenna, 2 is a biaxial piezoelectric fast mirror, 3 is a first beam splitter, 4 is a second beam splitter, 5 is a 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.

[0115] After the light beam is received by the optical antenna 1, it is transmitted to the biaxial piezoelectric fast mirror 2, and then transmitted to the first beam splitter 3 by the biaxial piezoelectric fast mirror 2; the first beam splitter 3 divides the received light beam into two paths, one of which is transmitted to the first detector 6, and the other is transmitted to the second beam splitter 4; the second beam splitter 4 divides the received light beam into two paths, one of which is transmitted to the light beam receiver 5, and the other is transmitted to the second detector 7.

[0116] The first detector 6 forms an image according to the received light beam, determines whether the image contains a light spot, and outputs a first light spot image to the image compensation module in the case where it is determined that the image contains a light spot; the image compensation module performs motion compensation on the first light spot image and outputs 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 shift amount according to the second light spot image.

[0117] The second detector 7 is turned on when the first light spot centroid shift amount is less than a third light spot centroid shift 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 opening condition is reached.

[0118] The light spot position determination module of the embodiment of the present application also has the following effects:

[0119] All target pixel points with a gray value lower than a preset gray threshold in the fourth light spot image are obtained, and the gray value of the target pixel point is set to 0 to obtain a fifth light spot image;

[0120] A second initial centroid position is determined according to the gray values of the pixel points in the fifth light spot image;

[0121] A plurality of sub-pixel points of the fifth light spot image are obtained by interpolating the pixels in a preset range centered on the second initial centroid position;

[0122] A second target centroid position is determined according to the gray values of the respective sub-pixel points corresponding to the fifth light spot image;

[0123] A second light spot centroid shift amount is determined according to the second target centroid position.

[0124] For example, in an embodiment of the present application, the light spot position determination module determines the second light spot centroid shift amount as follows:

[0125] After the fourth light spot image is obtained, the fourth light spot image is preprocessed first, a preset gray threshold T is set, the gray values lower than T in the fourth light spot image are set to 0, the interference is reduced, and a fifth light spot image is obtained, and the formula is as follows:

[0126]

[0127] Wherein, (m, n) represents the gray value of the fourth light spot image mth row, n column, the preset gray threshold T can be 1 / 2 of the maximum value of the light spot pixel gray.

[0128] Select one of the Gaussian fitting algorithm and the centroid algorithm as the second initial centroid position extraction algorithm, the specific selection of the second initial centroid position algorithm is not limited in the application.

[0129] Taking the centroid algorithm for extracting the second initial centroid position as an example, the gray value of the pixel is used as the weight to calculate the centroid of the light spot, the calculation speed is improved, assuming that the picture size is MxN, the gray value of each pixel point is f(m, n), and the calculation formula of the second initial centroid position (m', n') is:

[0130]

[0131] After obtaining the second initial centroid position (m', n'), the pixels in the preset range centered on the second initial centroid position (m', n') are interpolated to obtain a plurality of sub-pixels corresponding to the fifth light spot image, the centroid position is recalculated using the interpolated sub-pixels by formula 6 to determine the second target centroid position, and the second light spot centroid offset can be determined by the second target centroid position.

[0132] The second tracking controller controls the deflection of the two-axis piezoelectric fast mirror to adjust the path of the received light beam according to the second light spot centroid offset, further controls the alignment of the receiving end and the transmitting end, perfects the communication link, and can perform wireless communication when the communication opening condition is reached.

[0133] The first detector and the second detector are different, the first detector is used to process large divergence angle light beams, and the second detector is used to process small divergence angle light beams.

[0134] 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 visual axis caused by the motion and attitude drift of the receiving satellite platform after increasing the exposure time. The growth of exposure time can help quickly complete positioning, and can be applied to the case of receiving large divergence angle light beams and small divergence angle light beams for a long time; while in the case of short exposure time of light beam imaging and high loop bandwidth, after fast positioning, high-precision communication can be performed, the second detector can be directly operated, and the image compensation module does not need to be added.

[0135] Please refer to Figure 4 The working principle diagram of an ATP system provided by the embodiment of the application is as follows:Figure 4 As shown, the laser generating module and the optical antenna constitute the transmitting light path of the application, the laser generating module includes a laser transmitting 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 transmitting control unit is used to control the laser transmission and the divergence angle change, the pre-aiming mechanism realizes the aiming before transmission, and the optical antenna transmits the light beams with different divergence angles.

[0136] The optical antenna, the biaxial piezoelectric fast mirror, the first beam splitter, the second beam splitter, the first detector, the image compensation module, the 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 constitute the receiving light path of the application, when the optical antenna receives the light beam, the light beam is transmitted to the biaxial piezoelectric fast mirror and then is incident on the first beam splitter, and 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, and the second beam splitter divides the light beam into a first light beam transmitted to the light beam receiver and a second light beam transmitted to the second detector.

[0137] When it is needed to process the light beam by increasing the exposure time, the first detector operates, the received light beam is divided by the first beam splitter and then is transmitted to the first detector, the first detector generates a first spot image, and after image compensation processing, a second spot image is generated and is transmitted to the spot position determination module to determine the spot centroid position and determine the first spot centroid offset, and then the receiving light path controls the optical antenna to adjust the visual axis through the first tracking controller and the first tracking execution mechanism, reduces the first spot centroid offset, and makes the spot centroid position image on the center of the first detector as much as possible.

[0138] When the first spot centroid offset is less than the third spot centroid offset threshold, the transmitting 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 started, the second detector generates a fourth spot image and directly transmits the fourth spot image to the spot position determination module to determine the spot centroid position and determine the second spot centroid offset, and then the biaxial piezoelectric fast mirror is deflected through the second tracking controller and the second tracking execution mechanism to adjust the reflection angle of the incident light, to reduce the second spot centroid offset, and to adjust the path of the received light beam until the communication condition is met.

[0139] The ATP system provided by the application reduces the volume and development cost of the laser communication terminal, realizes the control of the divergence angle of the transmitting light beam, and on the other hand, realizes the high-precision chain building and guarantees the stability after the line is established.

[0140] The ATP system in the above embodiments of the application is used to establish a communication link and perform free space optical communication. Next, the free space optical communication link establishment method provided by the application will be described in combination with the ATP system provided by the application.

[0141] Please refer to Figure 5 , a flowchart of a free space optical communication link establishment method provided by the application is shown as follows, Figure 5 Figure 5 The free space optical communication link establishment method in the application 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 link establishment method provided by the application includes but is not limited to steps S110 to S150.

[0142] Step S110, determining an initial scanning and capturing area, wherein the initial scanning and capturing area includes a plurality of scanning points.

[0143] Step S120, traversing the scanning points in the initial scanning and capturing area, and transmitting a first light beam through an optical antenna according to a pointing direction of a currently traversed scanning point.

[0144] Step S130, ending the traversal of the scanning points in the initial scanning and capturing area in a case where a first feedback light beam transmitted by a second terminal according to the first light beam is received.

[0145] Step S140, forming a local first image according to the first feedback light beam, adjusting an optical antenna boresight pointing direction according to a first light spot centroid offset of 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.

[0146] Step S150, transmitting a third light beam through the optical antenna in a case where the second feedback light beam is received, 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.

[0147] The first terminal adopts a spaceborne ATP system provided by the application, and completes optical communication link establishment by transmitting three light beams with different divergence angles. The first light beam with the largest divergence angle is used to preliminarily scan and capture a second terminal, i.e., a receiving terminal. When the first feedback light beam transmitted 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 transmitted 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 transmitting the second light beam, the first terminal remains staring. In this process, the second light beam is continuously transmitted. When entering the tracking stage, the light beam to be transmitted is switched to the third light beam with a small divergence angle for tracking.

[0148] ​The embodiment of the application can switch to use output light beams with different divergence angles to establish a communication link according to needs when the optical communication link is established, so that the technical effects of reducing power consumption and improving the efficiency of communication link establishment can be achieved.

[0149] It should be noted that the first light beam is emitted according to the pointing of the current scanned point, including:

[0150] Residing at the current scanned point according to a preset residence time;

[0151] Within the residence time, the first light beam is emitted towards the pointing of the current scanned point.

[0152] For example, the terminal A as the first terminal, i.e., the transmitting terminal, initiates scanning, and the first tracking execution mechanism controls the deflection of the optical antenna, so as to control the large-divergence-angle scanning light beam to start from the center position of the uncertain region (FOU) and perform point-by-point scanning on the FOU region. The scanning mode can adopt a spiral scanning with equal pitch, a grating scanning, a grating spiral scanning, etc. The application does not limit the selection of the scanning mode. The application adopts a step-by-step scanning mode, which requires the terminal A to traverse the uncertain region point by point and reside at each scanned point for a sufficient time. The terminal B as the second terminal, i.e., the receiving terminal, keeps staring and waits for the light beam to be imaged. The residence time is preset by the two terminals.

[0153] According to the agreed scanning speed, the first detector of the terminal B images within each residence time and judges whether the light spot image is detected. If the light spot image is detected, the first feedback light beam is emitted to the terminal A. If the terminal A does not detect the feedback signal after the residence time ends, the next point is continuously scanned. If the feedback signal is not received after all points are scanned, the initial position is returned for cyclic scanning.

[0154] 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, attitude measurement error, satellite vibration and other factors, the initial pointing has an error. The size of the error directly determines the size of the initial capture FOU. Generally, the size of the initial capture uncertain region is 6 times the initial pointing error.

[0155] Through the scanning capture, the first terminal and the second terminal can preliminarily lock the positions of each other, so as to facilitate subsequent operations.

[0156] The first terminal includes a first detector, which is used to form a local first image according to the first feedback light beam.

[0157] The first spot centroid offset corresponding to the local first image is obtained by the following steps:

[0158] 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.

[0159] The first spot centroid offset is determined according to the gray value of the pixel points in the compensated local first image.

[0160] The process of performing motion compensation on 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; motion compensation is performed on the local first image according to the motion trajectory to obtain a compensated local first image.

[0161] The process of determining the first spot centroid offset according to the gray value of the pixel points in the compensated local first image can be as follows: the initial centroid position is determined according to the gray value of each pixel point 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; the target centroid position is determined according to the gray value of each of the sub-pixel points corresponding to the compensated local first image; and the first spot centroid offset is determined according to the target centroid position.

[0162] It can be understood that the image compensation module is used to compensate the received first image, which can reduce the image blur caused by the need to increase the exposure time during capture, and the first spot centroid offset obtained subsequently is used to assist the alignment of the two terminals for subsequent operations.

[0163] The spaceborne capture tracking and aiming system provided by the embodiments of the present application can be used for the first terminal to scan, capture and track the second terminal by adjusting the divergence angle of the emitted light beam, which can achieve the effect of rapid link establishment, does not need to use different wavebands from the signal light like beacon light scanning, does not need additional beacon light generating devices, and thus reduces the weight and volume of the terminal and the complexity of the optical path, and ensures high-precision tracking when switching to a small divergence angle light beam, and avoids the problems of long scanning time and high missing scanning probability when directly using a small divergence angle light beam.

[0164] Please refer to Figure 6 , another free space optical communication link establishment method provided by the embodiments of the present application is shown in the flowchart as Figure 6 , and the process of the method is as follows: Figure 6The free space optical communication link building method in the method is applied to the second terminal, which can also be referred to as a receiving terminal. When applied to the second terminal, the free space optical communication link building method provided by the embodiments of the present application includes but is not limited to steps S210 to S270.

[0165] Step S210, receiving a first light beam from the first terminal through an optical antenna.

[0166] Step S220, forming a local first image according to the first light beam.

[0167] Step S230, in the case that the local first image contains a light spot, adjusting the pointing direction of the optical antenna according to the first light spot centroid shift corresponding to the local first image.

[0168] Step S240, 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.

[0169] Step S250, 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 optical antenna, so that the second light spot centroid shift corresponding to the local second image is less than a preset first light spot centroid shift threshold.

[0170] Step S260, 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.

[0171] Step S270, receiving the third light beam through the optical antenna, and performing tracking processing according to the third light beam.

[0172] The second terminal adopts a satellite-borne acquisition tracking and aiming system provided by the embodiments of the present application. When receiving the light beam emitted by the first terminal, different operations are performed according to different light beams to complete the link building.

[0173] Exemplarily, when the second terminal receives the first light beam, a local first image is generated based on the first light beam. If it is detected that the local first image contains a light spot, the optical antenna's line of sight is adjusted to align it with the first terminal, and a first feedback beam is emitted to the first terminal; the second terminal emits the first feedback beam, so that the first terminal emits the second light beam based on the first feedback beam. The second terminal receives the second light beam and generates a second local image based on the second light beam. The generated second local image helps the second terminal adjust the optical antenna's line of sight direction and further aligns it with the first terminal, so that the second light spot center of mass offset corresponding to the local second image is less than the preset first light spot center of mass offset threshold. When this condition is met, a second feedback beam is sent to the first terminal, indicating that the capture has been completed and the conditions for entering the tracking state are met; when the first terminal receives the second feedback beam, a third light beam can be emitted to the second terminal based on the second feedback beam. When the second terminal receives the third beam, it enters the tracking state and performs tracking processing. The divergence angle of the third light beam used is smaller than the divergence angles of the first and second light beams.

[0174] It can be understood that in the embodiment of the present application, the first terminal can quickly capture the second terminal through the first light beam and the second light beam with large divergence angles. During the capture phase, the second terminal transmits two feedback signals, namely the first feedback light beam and the second feedback light beam, to ensure the accuracy of the capture. Therefore, using the satellite-borne ATP system provided in the embodiment of the present application, the exposure time of the capture phase can be appropriately increased, while avoiding the addition of additional beacon light devices and simplifying the terminal structure volume; when the capture is completed, it switches to the third light beam with a small divergence angle for tracking processing, and there is no need to use a small divergence angle light beam in the capture phase, which avoids the problems of long scanning time and high probability of missed scans when directly using a small divergence angle light beam, and improves the tracking processing accuracy.

[0175] It can be understood that when the first terminal receives the second feedback beam, it can be considered that the coarse tracking start condition is met, the first terminal transmits the third beam to the second terminal, and correspondingly, the second terminal receives the third beam from the first terminal and enters the coarse tracking process.

[0176] It should be noted that, in the embodiment of the present application, receiving the third light beam and performing tracking processing according to the third light beam include but are not limited to:

[0177] Forming a local third image according to the third light beam, adjusting the direction of the optical antenna's own optical axis so that the 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;

[0178] According to the third light beam, a local fourth image is formed, in the case that the local fourth image contains a light spot, by adjusting the deflection angle of the biaxial piezoelectric fast mirror, so that the fourth light spot centroid offset corresponding to the local fourth image is less than a preset third light spot centroid offset threshold, and the third light spot centroid offset threshold is less than the second light spot centroid offset threshold.

[0179] It should be noted that, in order to ensure the link establishment accuracy before the communication is started, the tracking stage is divided into a coarse tracking stage and a fine tracking stage in the embodiments of the present application.

[0180] 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 boresight itself, so that the third light spot centroid offset corresponding to the local third image is less than a preset second light 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.

[0181] In the fine tracking stage, the second terminal forms a local fourth image according to the third light beam, in the case that the local fourth image contains a light spot, by adjusting the deflection angle of the biaxial piezoelectric fast mirror, so that the fourth light spot centroid offset corresponding to the local fourth image is less than a preset third light 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, and when the fourth light spot centroid offset is less than the preset third light spot centroid offset threshold, the communication is started.

[0182] It should be noted that, in the fine tracking stage, there may be a situation that the platform vibration and satellite attitude adjustment make the fine tracking detector unable to detect the light 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, and the fine tracking is started again after the third light spot centroid offset is less than the preset second light spot centroid offset threshold, so as to avoid the interference between the coarse tracking and the fine tracking. At the same time, when the light spot position is detected in each fine tracking stage, it should also be judged whether the current light 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.

[0183] It can be understood that, in the embodiments of the present application, the second terminal includes a first detector and a second detector;

[0184] 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.

[0185] The first light spot centroid offset corresponding to the local first image is obtained by the following steps:

[0186] According to the motion information of the first detector and the satellite attitude adjustment information, the local first image is motion compensated to obtain a compensated local first image; and according to the gray values of the pixel points in the compensated local first image, the first light spot centroid offset is determined.

[0187] The process of motion compensating the local first image can be as follows: the motion information of the first detector is detected through the accelerometer and the angular displacement sensor, the motion information of the first detector is fused with the satellite attitude adjustment information to obtain N motion data points, wherein 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 first image is motion compensated according to the motion trajectory to obtain a compensated local first image.

[0188] 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: the 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; the 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.

[0189] The second light spot centroid offset corresponding to the local second image is obtained through the following steps:

[0190] According to the motion information of the first detector and the satellite attitude adjustment information, the local second image is motion compensated to obtain a compensated local second image; and according to the gray values of the pixel points in the compensated local second image, the second light spot centroid offset is determined.

[0191] The process of motion compensating the local second image can be as follows: the motion information of the first detector is detected through the accelerometer and the angular displacement sensor, the motion information of the first detector is fused with the satellite attitude adjustment information to obtain N motion data points, wherein 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 second image is motion compensated according to the motion trajectory to obtain a compensated local second image.

[0192] The process of determining the centroid offset of the second light spot based on the grayscale values ​​of the pixel points in the compensated local second image can be as follows: determine the initial centroid position based on the grayscale values ​​of each pixel point in the compensated local second image; interpolate the pixels within a preset range centered on the initial centroid position to obtain multiple sub-pixel points corresponding to the compensated local second image; determine the target centroid position based on the grayscale values ​​of each of the sub-pixel points corresponding to the compensated local second image; and determine the centroid offset of the second light spot based on the target centroid position.

[0193] The centroid offset of the third light spot corresponding to the local third image is obtained by the following steps:

[0194] Motion compensation is performed 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 a centroid offset of the third light spot is determined according to the grayscale values ​​of pixels in the compensated local third image.

[0195] The process of motion compensating the local third 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 with 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 local third image according to the motion trajectory to obtain a compensated local third image.

[0196] The process of determining the centroid offset of the third light spot based on the grayscale values ​​of the pixel points in the compensated local third image can be as follows: determine the initial centroid position based on the grayscale values ​​of each pixel point in the compensated local third image; interpolate the pixels within a preset range centered on the initial centroid position to obtain multiple sub-pixel points corresponding to the compensated local third image; determine the target centroid position based on the grayscale values ​​of each of the sub-pixel points corresponding to the compensated local third image; and determine the centroid offset of the third light spot based on the target centroid position.

[0197] When forming the local first image, the local second image and the local third image, the exposure time needs to be increased to increase the detector signal-to-noise ratio. At this time, the image compensation module needs to be involved, so it is completed through the first detector connected to the image compensation module.

[0198] The second detector is configured to form a local fourth image according to the third light beam.

[0199] The centroid offset of the fourth light spot corresponding to the local fourth image is obtained by the following steps:

[0200] The centroid offset of the fourth light spot is determined according to the grayscale value of the pixel in the local fourth image.

[0201] 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 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 fourth image according to the motion trajectory to obtain a compensated local fourth image.

[0202] 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.

[0203] As shown in Figure 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.

[0204] Please refer to Figure 7 , the free space optical communication link establishment method provided by the embodiment of the present application completes the flowchart as shown in Figure 7 , when the communication link establishment is needed, the following steps are completed:

[0205] The first terminal and the second terminal complete the initial pointing to an uncertain area, and the initial scanning capture area includes a plurality of scanning points. The first terminal serves as a transmitting terminal, and the second terminal serves as a receiving terminal.

[0206] The first terminal first transmits a first light beam through its own optical antenna, and scans the uncertain area through the first light beam stationary point. At this time, the first light beam used is a large divergence angle light beam.

[0207] 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, a local first image containing a light spot (denoted as image b1) is output.

[0208] The second terminal performs motion compensation on the image b1 based on the motion information of its own first detector and the satellite attitude adjustment information to obtain the compensated image b1. According to the grayscale value of the pixel point of the compensated image b1, the light spot centroid offset S is determined. b1 , and according to S b1 Adjust the boresight direction of its own optical antenna;

[0209] The second terminal transmits a first feedback beam to the first terminal through its own optical antenna;

[0210] It should be noted that if the second terminal does not detect the spot image, it will not emit the first feedback beam; if the first terminal still does not receive the first feedback beam after the dwell time at the current scanning point reaches the preset time, it will continue to traverse the next scanning point;

[0211] After receiving the first feedback beam, the first terminal stops scanning the uncertain area and forms a local first image (referred to as image a1) based on the first feedback beam through its own first detector. The first terminal performs motion compensation on image a1 based on the motion information of its own first detector and the satellite attitude adjustment information to obtain the compensated image a1. According to the grayscale value of the pixel point in the compensated image a1, the center of mass offset S of the light spot is determined. a1 , according to the spot centroid offset S a1 Adjust the boresight direction of its own optical antenna and keep emitting the second light beam with a large divergence angle through the optical antenna, while the first terminal is staring;

[0212] The second terminal receives the second light beam through its own optical antenna, and forms a local second image (referred to as image b2) based on the second light beam through its own first detector. The image b2 is motion compensated based on the motion information of its own first detector and the satellite attitude adjustment information to obtain the compensated image b2. The light spot centroid offset S is determined based on the grayscale value of the pixel point in the compensated image b2. b2 , and according to the spot centroid offset S b2 Adjust the optical antenna's boresight direction so that the center of mass of the light spot is offset by S b2 Less than a preset first spot centroid offset threshold;

[0213] When the center of mass offset of the spot S b2 When the value is less than a preset first light spot centroid offset threshold, it is determined that the coarse tracking start condition is met, and the second terminal sends a second feedback beam to the first terminal;

[0214] After receiving the second feedback beam, the first terminal determines that the capture is complete and can enter the coarse tracking phase;

[0215] After completing the acquisition, the first terminal will transmit a third beam with a small divergence angle to the second terminal to start coarse tracking;

[0216] The second terminal receives the third light beam through its optical antenna, forms a local third image (denoted as image b3) according to the third light beam through its first detector, and adjusts the pointing direction of the optical antenna of the second terminal so that the spot centroid offset S b3 is less than a preset second spot centroid offset threshold, at which time the image compensation module can be started to perform motion compensation on the image b3 to increase the extraction accuracy, and when the S b3 is less than the preset second spot centroid offset threshold, it is determined that the fine tracking start condition is met, and if the fine tracking start condition is not met, the pointing direction of the optical antenna of the second terminal is continuously adjusted;

[0217] After the fine tracking start condition is met, the second terminal forms a local fourth image (denoted as image b4) according to the third light beam, and in the case that 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 is less than a preset third spot centroid offset threshold, at which time the exposure time is short and the bandwidth of the fine tracking loop is high, and the image compensation module no longer needs to be added, and when the S b4 is less than the preset third spot centroid offset threshold, it is considered that the communication condition is met, the optical communication link is established, and the communication is started;

[0218] If the communication condition is not met, it is detected again whether the image b4 contains a spot, and when the spot image cannot be detected, the fine tracking stage is exited and the coarse tracking stage is re-entered to adjust the pointing direction.

[0219] Through the above Figure 7 flow, the technical effects of reducing power consumption, improving the efficiency of establishing a communication link, and ensuring the stability of the line after the link is established can be achieved through the communication link establishment of the light beam with the adjustable divergence angle.

[0220] Embodiments of the present application also provide an electronic device, as shown in Figure 9 , the electronic device 1400 includes:

[0221] one or more processors 1410;

[0222] a memory 1420 having one or more programs stored thereon, when the one or more programs are executed by the one or more processors 1410, the one or more processors 1410 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 by the embodiments of the present application.

[0223] The memory 1420, as a non-transitory network system, can be used to store non-transitory software programs and non-transitory computer executable programs. In addition, the memory 1420 can include a high-speed random access memory, and can also include a non-transitory memory, such as at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state memory device. In some embodiments, the memory 1420 can optionally include a memory 1420 disposed remotely with respect to the processor 1410, which can be connected to the processor 1410 through a network. Examples of the above-mentioned network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0224] 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). The memory 1420 can store an operating system and other application programs. When the technical solutions provided by the embodiments of the present specification are implemented by software or firmware, the related program codes are stored in the memory 1420 and are called and executed by the processor 1410 to implement the method of the embodiments of the present application.

[0225] 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 by the embodiments of the present application.

[0226] In some embodiments, the electronic device further includes:

[0227] An input / output interface for realizing information input and output;

[0228] 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 wireless means (such as mobile network, WIFI, Bluetooth, etc.);

[0229] 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;

[0230] 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.

[0231] An embodiment of the present application further provides a computer readable storage medium, which stores 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.

[0232] An embodiment of the present application further provides a computer program product, which comprises a computer program or computer instructions stored in a computer readable storage medium, and 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, so that the computer device implements 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.

[0233] The system architecture and application scenarios described in the embodiments of the present application are used to more clearly illustrate 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. It can be understood by those skilled in the art that, as the system architecture evolves and new application scenarios appear, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0234] It can be understood by those skilled in the art that all or part of the processes in the above-mentioned embodiments can be completed by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer readable storage medium. When the computer program is executed, the processes of the above-mentioned embodiments can be included. Any reference to memory, storage, database or other medium used in the embodiments provided by the present application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not 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).

[0235] 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.

[0236] 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, only B, 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 similar expressions means any combination of these items, including any combination of single or 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.

[0237] 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, characterized in that: 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, characterized in that 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 centroid offset is determined according to the first target centroid 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, characterized in that 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, characterized in that 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, characterized in that 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, characterized in that 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, characterized in that 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, characterized in that 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, characterized in that 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, characterized in that 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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