Self-calibrating time synchronization device and method for spaceborne high-resolution imaging systems

Abstract

This invention discloses a self-calibrating time synchronization device and method for a spaceborne high-resolution imaging system, relating to the field of data transmission technology. Its main objective is to solve the problem of low time synchronization accuracy in spaceborne high-resolution imaging systems. It mainly includes: a crystal oscillator, a timestamp module, a timestamp packing module, an imaging trigger module, and a camera positioning and timing module. The camera positioning and timing module sends whole-second timestamps to the timestamp packing module in real time and sends a second pulse signal to the timestamp module at each whole-second time node. The timestamp module performs intra-second timing based on the received clock signal and second pulse signal to obtain a real-time count value, and corrects the real-time count value to obtain the intra-second timestamp. The imaging trigger module sends a timestamp packing request to the timestamp packing module. The timestamp packing module reads the intra-second timestamps from the timestamp module and concatenates the intra-second timestamps and whole-second timestamps to form the imaging timestamp. It is mainly used for self-calibration of time synchronization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of data transmission, and relates to the fields of space optical imaging and detection, in particular to a self-correcting time synchronization device and method for a spaceborne high-resolution imaging system. BACKGROUND

[0002] In the field of space optical imaging, the time stamp of an image is the accurate time of camera imaging, which is used for time labeling of targets in the image, and the accuracy of time labeling directly affects the positioning accuracy. By using the image time stamp, the imaging time of each imaging device in the spaceborne imaging system can be time-synchronized, and the time of each frame of image imaging can be recorded. If the time synchronization accuracy is insufficient, the images captured by each device cannot be accurately aligned in time, resulting in misalignment or blurring when the images are spliced, which seriously affects the imaging quality.

[0003] The existing time synchronization of spaceborne devices usually relies on internal clock sources to generate time stamps. However, these clock sources can be affected by environmental factors such as temperature changes and radiation, causing their frequency to drift, which directly leads to inaccurate time synchronization. SUMMARY

[0004] Therefore, the present application provides a self-correcting time synchronization device and method for a spaceborne high-resolution imaging system, which mainly aims to solve the problem of low time synchronization accuracy of each imaging device in the existing spaceborne high-resolution imaging system.

[0005] According to one aspect of the present application, a self-correcting time synchronization device for a spaceborne high-resolution imaging system is provided, which is deployed in any imaging device in the spaceborne high-resolution imaging system and comprises a crystal oscillator, a time stamp module, a time stamp packaging module, an imaging trigger module and a camera positioning and timing module.

[0006] The camera positioning and timing module is connected with the time stamp module and the time stamp packaging module respectively, and is used to send an integral second time stamp to the time stamp packaging module in real time, and send a second pulse signal to the time stamp module at each integral second time node;

[0007] The crystal oscillator is connected with the time stamp module, and is used to send a clock signal to the time stamp module;

[0008] The time stamp module is used to perform intra-second timing according to the received clock signal and second pulse signal, obtain a real-time count value, and correct the real-time count value to obtain an intra-second time stamp;

[0009] The imaging trigger module is connected with the time stamp packaging module, and is used to send a time stamp packaging request to the time stamp packaging module in response to an imaging exposure instruction;

[0010] The timestamp packaging module is connected with the timestamp module, and is configured to read the intra-second timestamp from the timestamp module in response to a timestamp packaging request, and splice the intra-second timestamp and the whole-second timestamp into an imaging timestamp, so as to mark a remote sensing image collected under the imaging exposure instruction based on the imaging timestamp.

[0011] Further, the timestamp module comprises a timing self-correction unit.

[0012] The timing self-correction unit is configured to construct a first relationship vector of historical count values and time in a first historical time period and a second relationship vector of historical count values and time in a second historical time period according to historical intra-second count data received in the historical time period;

[0013] Second central moments of the first relationship vector and the second relationship vector are calculated, and a first correction coefficient is calculated according to the second central moments and a preset amplification factor;

[0014] An estimated value is calculated according to a mean value of the first relationship vector and the second relationship vector and the first correction coefficient, and after replacing a last intra-second count number in the second relationship vector with the estimated value to update the second relationship vector, iterative calculation of the estimated value is performed based on the updated second relationship vector until a target estimated value is obtained when a number of iterations reaches a preset iteration order;

[0015] A second correction coefficient is calculated according to the target estimated value, and a real-time count value is corrected according to the second correction coefficient to obtain the intra-second timestamp.

[0016] Further, the device further comprises a second pulse interface, and the timestamp module further comprises a second pulse input unit, a second pulse judgment unit and a reference clock unit;

[0017] The second pulse interface, the second pulse input unit, the second pulse judgment unit, the reference clock unit and the timing self-correction unit are sequentially connected;

[0018] The second pulse interface is configured to receive a second pulse signal from the camera positioning and timing-providing module, and transmit the second pulse signal to the second pulse input unit;

[0019] The second pulse input unit is configured to convert the second pulse signal into a digital level signal, and forward the digital level signal to the second pulse judgment unit;

[0020] The second pulse judgment unit is used for detecting a second pulse signal according to the digital level signal, and when the rising edge of the second pulse signal is detected, a synchronous trigger pulse is generated and sent to the reference clock unit to trigger the timer in the reference clock unit to reset and perform the second-in-second timing according to the clock signal again, and the real-time counting value is sent to the timing self-correction unit.

[0021] Further, the time stamp module further comprises a time register and a register read-write arbitration unit.

[0022] The input end of the time register is connected with the timing self-correction unit, and the output end is connected with the register read-write arbitration unit.

[0023] The timing self-correction unit is further used for sending the generated second-in-second time stamp to the time register for storage.

[0024] The time stamp packaging module is connected with the register read-write arbitration unit, and is used for sending a time register read request to the register read-write arbitration unit to read the second-in-second time stamp in response to a time stamp packaging instruction.

[0025] The register read-write arbitration unit is connected with the time register, and is used for continuously monitoring the read request from the time stamp packaging module and the write operation from the timing self-correction unit, and when the read request and the write operation conflict, the read request is responded preferentially, and the write operation of the timing self-correction unit is temporarily stored or delayed.

[0026] Further, the time stamp module further comprises a clock input unit and a clock phase-locked loop unit.

[0027] The crystal oscillator is connected with the clock input unit, and is used for generating a clock signal and sending the clock signal to the clock input unit.

[0028] The clock input unit is connected with the clock phase-locked loop unit, and is used for forwarding the clock signal to the clock phase-locked loop unit.

[0029] The clock phase-locked loop unit is connected with the reference clock unit, and is used for performing phase-locked and frequency multiplication processing on the clock signal, and inputting the processed clock signal into the reference clock unit, so that the counter in the reference clock unit performs the second-in-second timing according to the clock signal.

[0030] According to another aspect of the present application, a self-correction time synchronization method of a spaceborne high-resolution imaging system is provided, comprising:

[0031] The camera positioning time-providing module sends the whole-second time stamp to the time stamp packaging module, and sends the second pulse signal to the time stamp module at each whole-second time node.

[0032] sending a clock signal to the timestamp module through the crystal oscillator;

[0033] performing intra-second timing according to the received clock signal and the second pulse signal through the timestamp module to obtain a real-time count value, and correcting the real-time count value to obtain an intra-second timestamp;

[0034] sending a timestamp packaging request to the timestamp packaging module in response to an imaging exposure instruction through the imaging trigger module;

[0035] reading the intra-second timestamp from the timestamp module in response to the timestamp packaging request through the timestamp packaging module, and splicing the intra-second timestamp and the whole-second timestamp into an imaging timestamp to mark a remote sensing image collected under the imaging exposure instruction based on the imaging timestamp.

[0036] Further, the correcting the real-time count value to obtain an intra-second timestamp comprises:

[0037] constructing a first relationship vector of historical count values and time in a first historical time period and a second relationship vector of historical count values and time in a second historical time period according to historical intra-second count data received in the historical time period through the timing self-correction unit;

[0038] calculating a second-order central moment of the first relationship vector and the second relationship vector, and calculating a first correction coefficient according to the second-order central moment and a preset amplification factor;

[0039] calculating an estimated value according to the mean of the first relationship vector and the second relationship vector and the first correction coefficient, and performing iterative calculation of the estimated value based on the updated second relationship vector after replacing the last intra-second count number in the second relationship vector with the estimated value to update the second relationship vector, until the number of iterations reaches a preset iteration order to obtain a target estimated value;

[0040] calculating a second correction coefficient according to the target estimated value, and correcting the real-time count value according to the second correction coefficient to obtain an intra-second timestamp.

[0041] Further, the performing intra-second timing according to the received clock signal and the second pulse signal comprises:

[0042] receiving a second pulse signal from the camera positioning and timing module through the second pulse interface, and transmitting the second pulse signal to the second pulse input unit;

[0043] The second pulse signal is converted into a digital level signal by a second pulse input unit, and the digital level signal is forwarded to a second pulse judgment unit;

[0044] The second pulse judgment unit detects the second pulse signal according to the digital level signal, and generates and sends a synchronization trigger pulse to the reference clock unit when the rising edge of the second pulse signal is detected, so as to trigger the timer in the reference clock unit to reset and perform the second-in-second timing according to the clock signal again, and send the real-time count value to the timing self-correction unit.

[0045] Further, the method further comprises:

[0046] The generated second-in-second timestamp is sent to a time register by the timing self-correction unit for storage.

[0047] The time register read request is sent to the register read-write arbitration unit to read the second-in-second timestamp in response to the timestamp packaging instruction by the timestamp packaging module.

[0048] The register read-write arbitration unit continuously monitors the read request from the timestamp packaging module and the write operation from the timing self-correction unit, and when the read request and the write operation conflict, the read request is responded preferentially, and the write operation of the timing self-correction unit is temporarily stored or delayed.

[0049] Further, the method further comprises:

[0050] The clock signal is generated by the crystal oscillator and sent to the clock input unit.

[0051] The clock signal is forwarded to the clock phase-locked loop unit by the clock input unit.

[0052] The clock signal is phase-locked and frequency-multiplied by the clock phase-locked loop unit, and the processed clock signal is input to the reference clock unit, so that the counter in the reference clock unit performs second-in-second timing according to the clock signal.

[0053] By the above technical solutions, the technical solutions provided by the embodiments of the present application have at least the following advantages:

[0054] The application provides a self-correcting time synchronization device and method of a spaceborne high-resolution imaging system. The camera positioning time-providing module provides the whole-second timestamp and the second pulse, the second-in-second timing is triggered by the second pulse, and the second-in-second timing is corrected by the timestamp module, so that the time synchronization deviation caused by environmental interference and hardware error is greatly reduced, meanwhile, the real-time, accurate and stable time synchronization of the imaging devices in a complex space environment is ensured, and therefore the time synchronization accuracy of the spaceborne high-resolution imaging system is greatly improved.

[0055] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, the application can be implemented according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the application more obvious and easy to understand, the specific embodiments of the application are described below. BRIEF DESCRIPTION OF DRAWINGS

[0056] Various other advantages and benefits will become apparent to those of ordinary skill in the art, upon reading the following detailed description of the preferred embodiments. The accompanying drawings are intended to depict only preferred embodiments of the application, and therefore should not be considered to narrow the scope of the present application. Additionally, like reference numerals are intended to denote like parts throughout the various figures. In the drawings:

[0057] Figure 1 A self-correcting time synchronization device of a spaceborne high-resolution imaging system provided by the embodiment of the application is shown in a component block diagram;

[0058] Figure 2 Another self-correcting time synchronization device of a spaceborne high-resolution imaging system provided by the embodiment of the application is shown in a component block diagram;

[0059] Figure 3 A timing effect comparison diagram under a correction parameter provided by the embodiment of the application is shown;

[0060] Figure 4This invention provides a timekeeping performance comparison chart under another calibration parameter.

[0061] Figure 5 This invention provides a comparison chart of timing performance under another set of calibration parameters.

[0062] Figure 6 This invention provides a structural block diagram illustrating an application example of self-calibrating time synchronization in a spaceborne high-resolution imaging system.

[0063] Figure 7 A flowchart of a self-calibration time synchronization method for a spaceborne high-resolution imaging system provided by an embodiment of the present invention is shown. Detailed Implementation

[0064] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0065] To address the problem of low time synchronization accuracy in existing spaceborne high-resolution imaging systems, this invention provides a self-calibrating time synchronization device for spaceborne high-resolution imaging systems, such as... Figure 1 As shown, the device includes: a crystal oscillator 100, a timestamp module 200, a timestamp packaging module 300, an imaging trigger module 400, and a camera positioning and timing module 500. The camera positioning and timing module 500 is connected to both the timestamp module 200 and the timestamp packaging module 300; the crystal oscillator 100 is connected to the timestamp module 200; the timestamp packaging module 300 is connected to the timestamp module 200; and the imaging trigger module 400 is connected to the timestamp packaging module 300. This device is deployed in any imaging device within a spaceborne high-resolution imaging system; that is, this device is configured in every imaging device within the spaceborne high-resolution imaging system, and it enables time self-correction and time synchronization with other imaging devices.

[0066] In the embodiment of the present application, the camera positioning and timing module 500 comprises a GPS positioning and timing module and a Beidou positioning and timing module. It is mainly used for measuring the orbit and position of the load and generating a time reference signal (whole second time and second pulse signal). The camera positioning and timing module 500 sends the whole second time stamp to the time stamp packaging module 300 in real time and sends the second pulse signal to the time stamp module 200 at each whole second time node. The crystal oscillator 100 sends the clock signal to the time stamp module 200. The time stamp module 200 continuously counts according to the clock signal and, after receiving the second pulse signal, clears the clock according to the second pulse signal and re-counts the real-time count value according to the clock signal within a second to obtain the time stamp within a second. This time stamp within a second is continuously generated and stored in the time stamp module 200 in real time. When the imaging trigger module 400 is triggered by the imaging exposure instruction, it generates and sends a time stamp packaging request to the time stamp packaging module 300. After receiving the request, the time stamp packaging module 300 reads the latest time stamp within a second from the time stamp module 200 and splices the time stamp within a second with the latest whole second time stamp received from the camera positioning and timing module 500 to generate an imaging time stamp. The imaging exposure instruction is a synchronization signal sent to the imaging trigger module 400 at the same time of camera exposure (imaging each frame) of each imaging device to read the accurate time value. The whole second time stamp is used to represent the whole second time information of the current system to provide a reference of the current absolute time for the generation of the imaging time stamp. The time stamp within a second is used to represent the specific nanosecond time at the whole second time. The splicing result of the whole second time stamp and the time stamp within a second can provide a time mark accurate to the order of seconds. Thus, without using high-precision timing components, high-precision and accurate timing can be realized by designing simple and low-cost components to meet the precision requirements of the time of the satellite-borne imaging. The camera positioning and timing module is connected with the positioning system (GPS or Beidou) of the satellite-borne high-resolution imaging system and obtains the whole second time and the high-precision PPS reference time pulse signal generated based on the reference source. That is, each imaging device in the system obtains the current accurate time information and accurate second pulse through communication with the camera positioning and timing module to ensure the consistency of the imaging time of the device and other devices. On the basis of the time synchronization among the imaging devices, the time deviation caused by factors such as hardware aging and environmental changes can be overcome through the correction of the time stamp module. For example, even if the timing chip in the time stamp module has a certain frequency drift due to long-time operation, the time deviation can be controlled in a very small range through the correction of the time stamp module to ensure the accuracy of the time of the single imaging device.

[0067] It is to be noted that the camera positioning and timing module is connected with the positioning system (GPS or Beidou) of the satellite-borne high-resolution imaging system and obtains the whole second time and the high-precision PPS reference time pulse signal generated based on the reference source. That is, each imaging device in the system obtains the current accurate time information and accurate second pulse through communication with the camera positioning and timing module to ensure the consistency of the imaging time of the device and other devices. On the basis of the time synchronization among the imaging devices, the time deviation caused by factors such as hardware aging and environmental changes can be overcome through the correction of the time stamp module. For example, even if the timing chip in the time stamp module has a certain frequency drift due to long-time operation, the time deviation can be controlled in a very small range through the correction of the time stamp module to ensure the accuracy of the time of the single imaging device.

[0068] In one embodiment of the present application, for further illustration and definition, as shown in Figure 2 The device further comprises a second pulse interface 600, and the timestamp module further comprises a second pulse input unit 201, a second pulse judgment unit 202, a reference clock unit 203 and a timing self-correction unit 204; the second pulse interface 600, the second pulse input unit 201, the second pulse judgment unit 202, the reference clock unit 203 and the timing self-correction unit 204 are sequentially connected.

[0069] In one embodiment of the present application, the second pulse signal is received from the camera positioning and timing module 500 through the second pulse interface 600 (which can be an RS-422 physical interface), and the second pulse signal is transmitted to the second pulse interface 600 to transmit the second pulse information to the second pulse input unit 201 through the second pulse interface 600. Through the second pulse input unit 201, the second pulse signal is converted into a digital level signal to detect the second pulse signal, and when the rising edge of the second pulse signal is detected, a synchronization trigger pulse is generated and sent to the reference clock unit 203 to trigger the timer in the reference clock unit 203 to reset and restart the second-in-second timing according to the clock signal, and the real-time count value is sent to the timing self-correction unit 204. That is, after the judgment module confirms the signal, the reference clock unit is activated, the current counter is reset to zero, and the timing is restarted from zero, and the current count value is transmitted to the subsequent timing self-correction unit 204.

[0070] Further, as shown in Figure 2 The device further comprises a crystal oscillator, and the timestamp module further comprises a clock input unit 205 and a clock phase-locked loop unit 206; the crystal oscillator 100 is connected to the clock input unit 205, the clock input unit 205 is connected to the clock phase-locked loop unit 206, and the clock phase-locked loop unit 206 is connected to the reference clock unit 203 in the timestamp module.

[0071] In one embodiment of the present application, the clock signal is generated by the crystal oscillator 100 and sent to the clock input unit 205. A 40MHz crystal oscillator can be used as the clock source. The clock signal is forwarded to the clock phase-locked loop unit 206 through the clock input unit 205. The clock signal is phase-locked and frequency-multiplied by the clock phase-locked loop unit, and the clock signal is input to the reference clock unit, so that the counter in the reference clock unit counts according to the clock signal. By configuring the clock phase-locked loop unit 206 between the clock input unit 205 and the reference clock unit 203, a stable high-speed clock signal used in the FPGA can be generated by the phase-locked loop to provide accurate frequency support for the subsequent reference clock unit.

[0072] The reference clock unit receives a clock signal from the clock phase-locked loop unit and a second pulse signal from the second pulse module. The clock signal is used to control the counting frequency, for example, the counting frequency is 50MHz, and the reference clock unit counts once every 20ns clock signal. The second pulse signal is used to reset the count to ensure that the starting time of the count is aligned with the starting time of the whole second, thereby realizing the effect of representing the second time by the count value.

[0073] Further, the timestamp module further comprises a timing self-correction unit.

[0074] In the embodiment of the present application, the timing self-correction unit constructs a first relationship vector of historical count value and time in a first historical period and a second relationship vector of historical count value and time in a second historical period according to historical second-in-time count data received in the historical period; calculates the second central moment of the first relationship vector and the second relationship vector, and calculates a first correction coefficient according to the second central moment and a preset amplification factor; calculates an estimated value according to the mean of the first relationship vector and the second relationship vector and the first correction coefficient, and after replacing the last second-in-time count in the second relationship vector with the estimated value to update the second relationship vector, iteratively calculates the estimated value based on the updated second relationship vector until the number of iterations reaches a preset iteration order to obtain a target estimated value; calculates a second correction coefficient according to the target estimated value, and corrects the real-time count value according to the second correction coefficient to generate the second-in-time timestamp. The historical second-in-time count data is the count number per second in the historical period. The first relationship vector is a sequence of count number per second in the first historical period, and the second relationship vector is a sequence of count number per second in the second historical period. The first historical period is a historical period far from the current time, and the second historical period is a historical period containing the current time and a preset number of seconds before the current time.

[0075] Specifically, the first relationship vector is set as , and the second relationship vector is set as , The last measurement time of , The second central moment of the first relationship vector and the second relationship vector is respectively represented as follows: ;

[0076] ;

[0077] Wherein, represents the mean of , ; represents the mean of , , This represents the number of counts within each second from the 1st second to the ith second prior to the current time. This represents the number of counts within each second from the (i+1)th second to the (i+j)th second prior to the current time.

[0078] Then calculate the first correction factor. The formula is expressed as: ;

[0079] Where f is the amplification factor in the internal calculation process, generally selected from 0.1 to 2 based on experience, preferably 1. The estimated value is calculated based on the mean of the first and second relation vectors and the first correction coefficient, expressed by the formula: ;

[0080] in, This represents the estimated value. After obtaining the estimated value, the count of the last second in the second relation vector is replaced with the estimated value to update the second relation vector. Then, the estimated value is iteratively calculated based on the updated second relation vector until the number of iterations reaches a preset iteration order to obtain the target estimated value. The preset iteration order can be an integer from 1 to n; a larger value results in better convergence, but also increases the computational load and time. If k equals 1, the target estimated value is... If k is greater than 1, then... The counts in the vector closest to the current time (the last count in the last second) are updated to estimated values. The result is then substituted into the formula for calculating the second-order central moment for iterative calculation. The initial value of the count in the last second can be an estimated value of the count in the current second (the count in the current second has not ended, so the accurate count in the current second cannot be obtained).

[0081] If the target estimate is used as the count count within the current second, then the estimated period corresponding to the clock frequency is: (ns); Further calculation of the difference between the estimated period and the standard period value at the current frequency yields the second correction coefficient: (ns); where F is the counter frequency per second. Further, the real-time count value is corrected, and the formula for calculating the time within a second is obtained: Where cnt is the real-time count value. It represents time within seconds, and its unit is nanosecond (ns).

[0082] According to the base clock module frequency 50MHz, 20ns counts once. The base second pulse signal is simulated by a common computer, and the self-correction effect of the time stamp is tested by using the above embodiment. In the case of correction parameters i=3, j=3, k=2, f=1, the comparison effect of the original timing and the last output result after correction based on the embodiment is shown in Figure 3 . In the case of correction parameters i=5, j=3, k=2, f=1, the comparison effect of the original timing and the last output result after correction based on the embodiment is shown in Figure 4 . In the case of correction parameters i=5, j=3, k=3, f=1, the comparison effect of the original timing and the last output result after correction based on the embodiment is shown in Figure 5 .

[0083] Further, as shown in Figure 2 , the time stamp module further comprises a time register 207 and a register read-write arbitration unit 208; wherein the input end of the time register 207 is connected with the timing self-correction unit, and the output end is connected with the register read-write arbitration unit 208; the time stamp packaging module is connected with the register read-write arbitration unit 208; and the register read-write arbitration unit 208 is connected with the time register 207.

[0084] In the embodiment of the application, the generated second-in-time time stamp is sent to the time register 207 for storage by the timing self-correction unit. The time stamp packaging module sends a time register 207 read request to the register read-write arbitration unit 208 to read the real-time count value in response to a time stamp packaging instruction. By continuously monitoring the read request from the time stamp packaging module and the write operation from the timing self-correction unit through the register read-write arbitration unit 208, when the read request and the write operation conflict, the read priority of the time stamp packaging module is set to the highest, the read request is responded preferentially, and the write operation of the timing self-correction unit is temporarily stored or delayed. Thus, the real-time performance of the time stamp acquisition is ensured.

[0085] It should be noted that the timestamp packaging module and the imaging triggering module can also be connected via a triggering mechanism arbitration module. The triggering mechanism arbitration module is used to switch imaging triggering modes according to instructions. These modes include autonomous imaging triggering mode and timed triggering mode. In autonomous imaging triggering mode, for each frame of imaging, the precise time value from the timestamp packaging module is read and used as the timestamp of the current frame. In timed triggering mode, the triggering mechanism arbitration module cyclically reads the time value from the timestamp packaging module and triggers the imaging triggering module at the time intervals set by the instructions. In autonomous imaging triggering mode, the detector image control module images according to the set parameters, transmitting a synchronization pulse signal to the imaging triggering module during each frame's exposure. The imaging triggering module forwards this signal to the triggering mechanism arbitration module, which then sends a timestamp packaging instruction to the timestamp packaging module. The timestamp packaging module obtains the imaging timestamp according to this instruction signal, thus achieving synchronization between the timestamp and the imaging time.

[0086] In an application example of a spaceborne high-resolution imaging system, such as Figure 6 As shown, the hardware of this device can be built around a Field Programmable Gate Array (FPGA) as its core, supplemented by peripheral components. The FPGA communicates with the peripheral components via a 422 interface. The software within the FPGA, in addition to the second pulse module, timestamp module, timestamp packaging module, and imaging trigger module, can also include a detector image control module, instruction decoding module, image data packaging module, auxiliary data packaging module, and data output module. The detector image control module adapts to different detectors, providing timing drive, parameter configuration, and format encoding of output image data according to a preset imaging trigger sequence, and then transmits the encoded image data to the image data packaging module. The image data packaging module packages the format-encoded image data according to the output protocol, generating a complete packet format with output status for transmission to the data output module. The auxiliary data packaging module packages the imaging device's configuration parameters, imaging timestamps (from the timestamp packaging module), and attitude data (from the star sensor) according to a format including frame header, data type flag, valid data (configuration parameters, timestamps, attitude information), checksum, and frame tail, and transmits this data to the data output module. The data output module transmits image data and auxiliary data to the on-board storage device in the order of image data first, followed by auxiliary data.

[0087] Peripheral components include, but are not limited to, a camera positioning and timing module, a crystal oscillator (providing clock signals to the FPGA), a star sensor (measuring the camera's attitude and transmitting the attitude data to the auxiliary data packaging module), an on-board storage unit (used to receive and store image data, imaging timestamps, camera attitude data, etc., output by the aforementioned data output module), and satellite commands (sending commands to the command parsing module via the 422 interface).

[0088] This invention provides a self-calibrating time synchronization device for a spaceborne high-resolution imaging system, comprising a crystal oscillator, a timestamp module, a timestamp packing module, an imaging trigger module, and a camera positioning and timing module. In this embodiment, the camera positioning and timing module sends whole-second timestamps to the timestamp packing module and sends second pulse signals to the timestamp module at each whole-second time node. The crystal oscillator sends a clock signal to the timestamp module. The timestamp module performs intra-second timing based on the received clock signal and second pulse signal to obtain a real-time count value, and corrects the real-time count value to obtain an intra-second timestamp. The imaging trigger module, in response to an imaging exposure command, sends a timestamp packing request to the timestamp packing module. The timestamp packing module, in response to the timestamp packing request, reads the intra-second timestamp from the timestamp module and concatenates the intra-second timestamp with the whole-second timestamp to form an imaging timestamp, thereby marking the remote sensing image acquired under the imaging exposure command based on the imaging timestamp. The camera positioning and timing module provides whole-second timestamps and second pulses, with the second pulses triggering the timing within the second. The timestamp module corrects the timing within the second, greatly reducing time synchronization deviations caused by environmental interference and hardware errors. At the same time, it ensures that each imaging device can achieve real-time, accurate and stable time synchronization in complex space environments, thereby greatly improving the time synchronization accuracy of the spaceborne high-resolution imaging system.

[0089] Furthermore, as a response to the above Figure 1 The software execution process of the device shown in this invention provides a self-calibrating time synchronization method for a spaceborne high-resolution imaging system, such as... Figure 7 As shown, the method includes:

[0090] 101. The camera positioning and timing module sends whole-second timestamps to the timestamp packaging module and sends second pulse signals to the second pulse module at each whole-second time node.

[0091] 102. A clock signal is sent to the timestamp module via the crystal oscillator.

[0092] 103. Using the timestamp module, the real-time count value is obtained by timing within seconds based on the received clock signal and the second pulse signal, and the real-time count value is corrected to obtain the timestamp within seconds.

[0093] 104、by imaging trigger module, in response to imaging exposure instruction, to the timestamp packaging module sends timestamp packaging request.

[0094] 105、by timestamp packaging module, in response to timestamp packaging request, from the timestamp module reads the second time stamp, and the second time stamp and the whole second time stamp are spliced into imaging time stamp, to mark the remote sensing image collected under the imaging exposure instruction based on the imaging time stamp.

[0095] Further, the correction of the real-time count value obtains the second time stamp, comprising:

[0096] By timing self-correction unit, according to the historical second count data received in the historical period, the first relationship vector of historical count value and time in the first historical period and the second relationship vector of historical count value and time in the second historical period are constructed;

[0097] The second central moment of the first relationship vector and the second relationship vector is calculated, and the first correction coefficient is calculated according to the second central moment and the preset amplification factor;

[0098] According to the mean of the first relationship vector and the second relationship vector and the first correction coefficient, an estimated value is calculated, and after replacing the last second count in the second relationship vector with the estimated value to update the second relationship vector, the iterative calculation of the estimated value is carried out based on the updated second relationship vector, until the number of iterations reaches the preset iteration order to obtain the target estimated value;

[0099] According to the target estimated value, a second correction coefficient is calculated, and the real-time count value is corrected according to the second correction coefficient to obtain the second time stamp.

[0100] Further, the second time stamp obtained by correcting the real-time count value, comprising:

[0101] Through the second pulse interface, the second pulse signal is received from the camera positioning time module, and the second pulse signal is transmitted to the second pulse input unit;

[0102] Through the second pulse input unit, the second pulse signal is converted into a digital level signal, and the digital level signal is forwarded to the second pulse judgment unit;

[0103] Through the pulse judgment unit, the second pulse signal is detected according to the digital level signal, when the rising edge of the second pulse signal is detected, the synchronization trigger pulse is generated and sent to the reference clock unit to trigger the timer in the reference clock unit to zero and re-count the second time according to the clock signal, so as to send the real-time count value to the timing self-correction unit.

[0104] Further, the method further comprises:

[0105] The timing self-correction unit sends the generated intra-second time stamp to the time register for storage;

[0106] Through the register read-write arbitration unit, the read request from the time stamp packaging module and the write operation from the timing self-correction unit are continuously monitored, when the read request and the write operation conflict, the read request is responded preferentially, and the write operation of the timing self-correction unit is temporarily stored or delayed.

[0107] Further, the method further comprises:

[0108] Through the crystal oscillator, a clock signal is generated, and the clock signal is sent to the clock input unit;

[0109] Through the clock input unit, the clock signal is forwarded to the clock phase-locked loop unit;

[0110] Through the clock phase-locked loop unit, the clock signal is phase-locked and frequency-multiplied, and the processed clock signal is input to the reference clock unit, so that the counter in the reference clock unit performs intra-second timing according to the clock signal.

[0111] The application provides a self-correction time synchronization method of a satellite-borne high-resolution imaging system, the camera positioning time-providing module sends a whole-second time stamp to the time stamp packaging module, and sends a second pulse signal to the time stamp module at each whole-second time node; the crystal oscillator sends a clock signal to the time stamp module; the time stamp module performs intra-second timing according to the received clock signal and second pulse signal, obtains a real-time count value, and corrects the real-time count value to obtain an intra-second time stamp; the imaging trigger module sends a time stamp packaging request to the time stamp packaging module in response to an imaging exposure instruction; the time stamp packaging module reads the intra-second time stamp from the time stamp module in response to the time stamp packaging request, splices the intra-second time stamp and the whole-second time stamp into an imaging time stamp, and marks a remote sensing image collected under the imaging exposure instruction based on the imaging time stamp. The camera positioning time-providing module provides a whole-second time stamp and a second pulse, the second pulse triggers intra-second timing, and the time stamp module corrects the intra-second timing, which greatly reduces the time synchronization deviation caused by environmental interference and hardware errors, and ensures that each imaging device can realize real-time, accurate and stable time synchronization in a complex space environment, thereby greatly improving the time synchronization accuracy of the satellite-borne high-resolution imaging system.

[0112] It should be apparent to those skilled in the art that the modules or steps of the application described above can be implemented with a general purpose computing device, which can be centralized on a single computing device or distributed over a network of multiple computing devices, and optionally implemented with program code executable by a computing device, which can be stored in a storage device and executed by a computing device, and in some cases, the steps shown or described can be performed in a different order than shown, or made into individual integrated circuit modules, or multiple modules or steps made into a single integrated circuit module. Thus, the application is not limited to any particular combination of hardware and software.

[0113] The preferred embodiments of the application described above are intended to be merely exemplary and those skilled in the art will recognize that changes can be made to the above-described embodiments without departing from the spirit and scope of the application. What is desired to be protected by letters patent is set forth in the appended claims.

Claims

1. A self-correcting time synchronization apparatus for a space-borne high resolution imaging system, characterized by, The device is arranged in any imaging equipment of a spaceborne high-resolution imaging system, and comprises a crystal oscillator, a timestamp module, a timestamp packaging module, an imaging trigger module and a camera positioning and timing module; The camera positioning and timing module is connected with the timestamp module and the timestamp packaging module respectively, and is configured to send an integral second timestamp to the timestamp packaging module in real time and send a second pulse signal to the timestamp module at each integral second time node; The crystal oscillator is connected with the timestamp module, and is configured to send a clock signal to the timestamp module; The timestamp module is used to perform intra-second timing based on the received clock signal and the second pulse signal to obtain a real-time count value, and to correct the real-time count value to obtain an intra-second timestamp. The timestamp module includes a timing self-correction unit. The timing self-correction unit is used to construct a first relationship vector between historical count values ​​and time in a first historical period and a second relationship vector between historical count values ​​and time in a second historical period based on historical intra-second count data received in a historical period; calculate the second-order central moments of the first relationship vector and the second relationship vector, and calculate a first correction coefficient based on the second-order central moments and a preset amplification factor; calculate an estimated value based on the mean of the first relationship vector and the second relationship vector and the first correction coefficient, and after replacing the last intra-second count in the second relationship vector with the estimated value to update the second relationship vector, iteratively calculate the estimated value based on the updated second relationship vector until the number of iterations reaches a preset iteration order to obtain a target estimated value; calculate a second correction coefficient based on the target estimated value, and correct the real-time count value based on the second correction coefficient to obtain an intra-second timestamp, wherein the first relationship vector... Second central moments Represented as ; the second relation vector Second central moments Represented as: ; wherein, represents the mean of ; represents the mean of , represents the count number in each second from the first to the i-th second forward from the current time; represents the count number in each second from the i+1 to the i+j second forward from the current time; the first correction coefficient , the formula is: ; wherein, f is the amplification factor in the internal calculation process; the estimated value the formula is: ; the target estimated value is obtained as the count number in the second at the current time, and the period estimated value corresponding to the clock frequency is: ; the second correction coefficient formula is ; wherein, F is the counter frequency per second; the calculation formula of the time in the second is: ; wherein, cnt is the real-time count value, is the time stamp in the second; The imaging trigger module is connected with the timestamp packaging module, and is configured to send a timestamp packaging request to the timestamp packaging module in response to an imaging exposure instruction; The timestamp packaging module is connected with the timestamp module, and is configured to read an intra-second timestamp from the timestamp module in response to the timestamp packaging request, and splice the intra-second timestamp and the integral second timestamp into an imaging timestamp, so as to mark a remote sensing image collected under the imaging exposure instruction based on the imaging timestamp.

2. The self-correcting time synchronization apparatus for a space-borne high resolution imaging system of claim 1, wherein, The device further comprises a second pulse interface, and the timestamp module further comprises a second pulse input unit, a second pulse judgment unit and a reference clock unit; The second pulse interface, the second pulse input unit, the second pulse judgment unit, the reference clock unit and the timing self-correction unit are sequentially connected; The second pulse interface is configured to receive a second pulse signal from the camera positioning and timing module and transmit the second pulse signal to the second pulse input unit; The second pulse input unit is configured to convert the second pulse signal into a digital level signal and forward the digital level signal to the second pulse judgment unit; The second pulse judgment unit is configured to detect the second pulse signal according to the digital level signal, generate and send a synchronization trigger pulse to the reference clock unit when the rising edge of the second pulse signal is detected, so as to trigger the timer in the reference clock unit to reset and perform intra-second timing again according to the clock signal, and send a real-time count value to the timing self-correction unit.

3. The self-correcting time synchronization apparatus for a space-borne high resolution imaging system of claim 1, wherein, The timestamp module further comprises a time register and a register read-write arbitration unit; The input end of the time register is connected with the timing self-correction unit, and the output end is connected with the register read-write arbitration unit; The timing self-correction unit is further configured to send the generated intra-second timestamp to the time register for storage; The timestamp packaging module is connected with the register read-write arbitration unit, and is configured to send a time register read request to the register read-write arbitration unit to read the intra-second timestamp in response to a timestamp packaging instruction; The register read-write arbitration unit is connected with the time register, and is configured to continuously monitor the read request from the timestamp packaging module and the write operation from the timing self-correction unit, and when the read request and the write operation conflict, the read request is responded preferentially, and the write operation of the timing self-correction unit is temporarily stored or delayed.

4. The self-correcting time synchronization apparatus of a space-borne high resolution imaging system according to any one of claims 1-3, characterized in that, The timestamp module further comprises a clock input unit and a clock phase-locked loop unit; The crystal oscillator is connected with the clock input unit, and is used for generating a clock signal and sending the clock signal to the clock input unit; The clock input unit is connected with the clock phase-locked loop unit, and is used for forwarding the clock signal to the clock phase-locked loop unit; The clock phase-locked loop unit is connected with the reference clock unit, and is used for phase-locked and frequency multiplication processing of the clock signal, and inputting the processed clock signal into the reference clock unit, so that a counter in the reference clock unit performs second-in-second timing according to the clock signal.

5. A self-correcting time synchronization method for a space-borne high resolution imaging system, characterized in that, Comprise: Through the camera positioning time service module, send the whole second timestamp to the timestamp packaging module, and send the second pulse signal to the timestamp module at each whole second time node; Through the crystal oscillator, send the clock signal to the timestamp module; Through the timestamp module, perform second-in-second timing according to the received clock signal and second pulse signal, obtain a real-time count value, and correct the real-time count value to obtain a second-in-second timestamp, comprising: Through the timing self-correction unit, construct a first relationship vector of historical count value and time in a first historical period and a second relationship vector of historical count value and time in a second historical period according to historical second-in-second count data received in the historical period; Calculate the second central moment of the first relationship vector and the second relationship vector, and calculate a first correction coefficient according to the second central moment and a preset amplification factor; Calculate an estimated value according to the mean of the first relationship vector and the second relationship vector and the first correction coefficient, and after replacing the last second-in-second count number in the second relationship vector with the estimated value to update the second relationship vector, perform iterative calculation of the estimated value based on the updated second relationship vector until the number of iterations reaches a preset iteration order to obtain a target estimated value; A second correction coefficient is calculated based on the target estimate, and the real-time count value is corrected based on the second correction coefficient to obtain a timestamp within seconds, wherein the first relation vector Second central moments Represented as ; the second relation vector Second central moments Represented as: ; wherein, represents the mean of ; represents the mean of , represents the count number in each second from the first to the i-th second forward from the current time; represents the count number in each second from the i+1 to the i+j second forward from the current time; the first correction coefficient , the formula is: ; wherein, f is the amplification factor in the internal calculation process; the estimated value the formula is: ; the target estimated value is obtained as the count number in the second at the current time, and the period estimated value corresponding to the clock frequency is: ; the second correction coefficient formula is ; wherein, F is the counter frequency per second; the calculation formula of the time in the second is: ; wherein, cnt is the real-time count value, the time stamp in the second; Through the imaging trigger module, send a timestamp packaging request to the timestamp packaging module in response to an imaging exposure instruction; Through the timestamp packaging module, read the second-in-second timestamp from the timestamp module in response to the timestamp packaging request, and splice the second-in-second timestamp and the whole second timestamp into an imaging timestamp, so as to mark a remote sensing image collected under the imaging exposure instruction based on the imaging timestamp.

6. The self-correcting time synchronization method for a space-borne high resolution imaging system of claim 5, wherein, According to the received clock signal and the second pulse signal, comprising: Through the second pulse interface, receive the second pulse signal from the camera positioning time service module, and transmit the second pulse signal to the second pulse input unit; Through the second pulse input unit, convert the second pulse signal into a digital level signal, and forward the digital level signal to the second pulse judgment unit; Through the second pulse judgment unit, detect the second pulse signal according to the digital level signal, generate and send a synchronization trigger pulse to the reference clock unit when the rising edge of the second pulse signal is detected, so as to trigger the timer in the reference clock unit to reset and perform second-in-second timing according to the clock signal again, so as to send the real-time count value to the timing self-correction unit.

7. The self-correcting time synchronization method for a space-borne high resolution imaging system of claim 6, wherein, The method further comprises: The generated sub-second time stamp is sent to a time register for storage by the timing self-correction unit; In response to a time stamp packaging instruction, the time stamp packaging module sends a time register read request to the register read-write arbitration unit to read the sub-second time stamp; The register read-write arbitration unit continuously monitors the read request from the time stamp packaging module and the write operation from the timing self-correction unit, and when the read request and the write operation conflict, the read request is responded to preferentially, and the write operation of the timing self-correction unit is temporarily stored or delayed.

8. The self-correcting time synchronization method of a space-borne high resolution imaging system according to any one of claims 5-7, characterized in that, The method further comprises: A crystal oscillator generates a clock signal and sends the clock signal to a clock input unit; The clock input unit forwards the clock signal to a clock phase-locked loop unit; The clock phase-locked loop unit performs phase locking and frequency multiplication processing on the clock signal and inputs the processed clock signal to a reference clock unit, so that the counter in the reference clock unit performs sub-second timing according to the clock signal.

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