Precision calibration system and method of free space laser communication distance measuring device
By using a measurement system consisting of a total station, a reflecting prism, and a displacement stage, the ranging accuracy of the free-space laser communication ranging device was calibrated. This solved the problem of insufficient accuracy in existing technologies, improved the accuracy and stability of the ranging device, and promoted its application in high-precision applications such as satellite orbit determination and navigation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-27
AI Technical Summary
Existing free-space laser communication ranging devices lack consideration for accuracy when evaluating ranging precision, which affects their reliability in high-precision applications such as satellite orbit determination and navigation.
A total station and a reflecting prism, along with a displacement stage, were used to obtain the first and second distances through multiple measurements. The difference and standard deviation were calculated to compensate for the fixed delay. Linear fitting and data filtering were performed to calibrate the distance measurement accuracy.
This improves the ranging accuracy and stability of free-space laser communication ranging devices, promoting their application in high-precision scenarios such as satellite orbit determination and navigation.
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Figure CN121741707A_ABST
Abstract
Description
Technical Field
[0001] At least one embodiment of this disclosure relates to the field of laser communication and ranging technology, and in particular to an accuracy calibration system and method for a free-space laser communication ranging device. Background Technology
[0002] With the development of space laser communication technology, space laser communication terminals have gradually become a standard configuration for satellite payloads. Utilizing laser communication terminals for ranging can further expand their application value and improve ranging accuracy between satellites or between satellites and the ground, as well as satellite orbit determination accuracy. Currently, laser ranging schemes mainly include pulsed laser ranging, continuous wave laser ranging, and triangulation. Space laser communication-based ranging methods, such as Satellite Laser Ranging (SLR) and lidar, offer advantages over pulsed laser ranging in terms of longer range and higher accuracy, and have broad application prospects in satellite navigation and satellite orbit determination.
[0003] However, in free-space laser communication ranging devices of related technologies, the standard deviation or half-width at half-maximum of the ranging results is used to evaluate the ranging accuracy, and accuracy is rarely considered, which affects the reliable application of space laser communication ranging in scenarios such as satellite orbit determination and navigation. Summary of the Invention
[0004] In view of this, this disclosure provides a precision calibration system for a free-space laser communication ranging device, which can provide quantitative indicators for the ranging accuracy of the laser communication ranging device in long-distance free-space link scenarios, and realize the effective calibration of the ranging accuracy of the laser communication ranging device.
[0005] As a first aspect of the present disclosure, an accuracy calibration system for a free-space laser communication ranging device is provided, comprising two displacement stages spaced apart in a first direction, a total station, a reflecting prism, and a controller. At least one of the two displacement stages is configured to translate in the first direction, wherein two ranging terminals of the free-space laser communication ranging device are respectively disposed on the two displacement stages, and the two ranging terminals are configured to acquire a first measurement distance between the two ranging terminals. The total station is disposed on one of the two displacement stages. The reflecting prism is disposed on the other of the two displacement stages and is adapted to cooperate with the total station to obtain a second measurement distance between the total station and the reflecting prism. The controller is configured to control the movement of at least one of the two displacement stages to change the distance between the two displacement stages, so as to calibrate the ranging accuracy of the free-space laser communication ranging device based on a plurality of first measurement distances and a plurality of second measurement distances.
[0006] According to an embodiment of this disclosure, a ranging terminal and a total station are configured to be spaced apart on a displacement stage along a second direction. Another ranging terminal and a reflecting prism are configured to be spaced apart on another displacement stage along the second direction. The two ranging terminals face each other in a first direction, the total station and the reflecting prism face each other in a first direction, and the second direction is orthogonal to the first direction.
[0007] According to embodiments of this disclosure, when the two displacement stages are at a preset distance, the controller is configured to: repeatedly switch the total station and the free-space laser communication ranging device on and off, acquiring multiple first measurement distances and multiple second measurement distances respectively. Multiple differences are determined based on the multiple first measurement distances and multiple second measurement distances, and the average of the multiple differences is used as the systematic error of the free-space laser communication ranging device to compensate for the fixed delay in the laser communication ranging device. Multiple standard deviations are determined based on the multiple first measurement distances and multiple second measurement distances to determine the repeatability accuracy in the ranging accuracy.
[0008] According to embodiments of the present disclosure, the controller is further configured to: control at least one of the two displacement stages to move to a target distance multiple times to obtain multiple new first measurement distances and multiple new second measurement distances, and determine linearity in the ranging accuracy based on the multiple new first measurement distances and multiple new second measurement distances.
[0009] According to embodiments of the present disclosure, the controller is configured to: perform linear fitting on a plurality of new first measurement distances and a plurality of new second measurement distances, and determine linearity based on the deviation of the slope of the fitted line from the ideal slope.
[0010] According to embodiments of this disclosure, the controller is configured to: filter data from a plurality of first measured distances and remove abnormal data points that exceed a preset threshold.
[0011] As a second aspect of the present disclosure, a method for calibrating a free-space laser communication ranging device using a precision calibration system is provided. The method includes: repeatedly switching a total station and the free-space laser communication ranging device at a preset distance to acquire multiple first measurement distances and multiple second measurement distances, respectively; determining multiple differences based on the multiple first measurement distances and multiple second measurement distances; using the average of the multiple differences as the system error of the free-space laser communication ranging device to compensate for a fixed delay in the laser communication ranging device; and determining multiple standard deviations based on the multiple first measurement distances and multiple second measurement distances to determine the repeatability accuracy of the free-space laser communication ranging device based on the multiple standard deviations.
[0012] According to embodiments of this disclosure, the method for calibrating a free-space laser communication ranging device further includes: repeatedly controlling the moving target distance of at least one of two displacement stages to obtain multiple new first measurement distances through two ranging terminals, and obtaining multiple new second measurement distances through a total station. The linearity of the free-space laser communication ranging device is determined based on the multiple new first measurement distances and the multiple new second measurement distances.
[0013] According to embodiments of this disclosure, determining linearity includes: performing linear fitting on a plurality of new first measured distances and a plurality of new second measured distances, and determining linearity based on the deviation of the slope of the fitted line from the ideal slope.
[0014] According to embodiments of this disclosure, the method for calibrating a free-space laser communication ranging device further includes: filtering data from a plurality of first measurement distances and removing abnormal data points that exceed a preset threshold.
[0015] According to the accuracy calibration system of the free-space laser communication ranging device according to the embodiments of this disclosure, two ranging terminals are respectively set on two displacement stages spaced apart in a first direction. This facilitates the establishment of a stable free-space laser communication link between the two ranging terminals. The two ranging terminals are configured to acquire a first measurement distance between them, which serves as a data sample for calibrating the ranging accuracy of the free-space laser communication ranging device. Furthermore, compared to the first measurement distance, a second measurement distance is obtained by setting a total station on one of the two displacement stages and a reflecting prism on the other. Since the total station is a dedicated high-precision measuring device, the second measurement distance between the total station and the reflecting prism provides a reliable reference for the first measurement distance. Then, by configuring at least one of the two displacement stages to translate in the first direction under the control of the controller, the distance between the two displacement stages can be controlled and adjusted. Since the ranging terminal, total station and reflecting prism all move synchronously with the displacement stages, it is convenient to obtain multiple sets of first and second measurement distances at different intervals and compare and analyze them. This helps to calibrate the ranging accuracy of the free space laser communication ranging device based on multiple first and second measurement distances, and helps to better utilize the laser communication terminal for ranging. It also promotes the application and development of laser communication ranging devices in high-precision scenarios such as satellite orbit determination and navigation, so as to meet the application needs of integrated communication and ranging as much as possible. Attached Figure Description
[0016] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:
[0017] Figure 1 The diagram schematically illustrates the composition of an accuracy calibration system for a free-space laser communication ranging device according to an embodiment of the present disclosure.
[0018] Figure 2 Schematic illustration Figure 1 The diagram shows the composition of the electronics and optoelectronic modules.
[0019] Figure 3 Schematic illustration Figure 2 The diagram shown is a schematic of the ranging terminal.
[0020] Figure 4 Schematic illustration Figure 1 The graph shows the variation of the difference between multiple tests when the distance between the two displacement stages is fixed.
[0021] Figure 5 Schematic illustration Figure 1 The graph shows the change in the second measured distance during multiple tests when the distance between the two displacement stages changes.
[0022] Figure 6 Schematic illustration Figure 1 The diagram shows the probability distribution of the first measured distance in multiple tests when the distance between the two displacement stages changes.
[0023] Figure 7 The flowchart illustrates a method for calibrating a free-space laser communication ranging device using an accuracy calibration system according to an embodiment of the present disclosure.
[0024] In the accompanying drawings, the meanings of the reference numerals are as follows:
[0025] 1-Displacement stage;
[0026] 2-Distance measuring terminal. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.
[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.
[0029] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.
[0030] When using expressions such as "at least one of A, B, and C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C. Similarly, when using expressions such as "at least one of A, B, or C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C.
[0031] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding this disclosure.
[0032] Free space, as an application scenario for laser communication ranging, differs from wired transmission environments such as fiber optics and waveguides. It refers to unobstructed space where air or vacuum serves as the transmission medium, such as the space between a satellite and a ground station, or between two satellites. In related free-space laser communication ranging devices, the standard deviation or half-width at half-maximum (HWHM) of the ranging results is used to evaluate ranging accuracy. The standard deviation is a statistical measure of the deviation of multiple ranging values from the average value, while HWHM refers to the width of the curve at half the peak value on the probability distribution curve (such as a normal distribution curve) of the ranging results. These indicators reflect the dispersion of multiple ranging values.
[0033] However, in high-precision applications such as satellite orbit determination and navigation, the impact of accuracy and dispersion must be considered. Satellite orbit determination, also known as satellite orbit determination, calculates the satellite's position, velocity, and other parameters in space by measuring distance data between the satellite and ground stations, and between satellites themselves, combined with orbital mechanics models. This is fundamental to satellite navigation, deep space exploration, and other fields. Accuracy reflects the deviation of the average value of the measurement results from the true value. Specifically, it refers to the deviation between the average value of multiple distance measurements within a short period and the actual physical distance. If the average value of the distance measurement results deviates from the actual distance, even with a low degree of dispersion, it will lead to problems such as orbit calculation errors and inaccurate navigation and positioning, adversely affecting the reliable application of free-space laser communication ranging devices in satellite orbit determination and navigation scenarios.
[0034] Figure 1The diagram schematically illustrates the composition of an accuracy calibration system for a free-space laser communication ranging device according to an embodiment of the present disclosure.
[0035] like Figure 1 As shown, as a first aspect of the embodiments of this disclosure, a precision calibration system for a free-space laser communication ranging device is provided. The precision calibration system includes two displacement stages 1 spaced apart in a first direction, a total station, a reflecting prism, and a controller (not shown in the figure). At least one of the two displacement stages 1 is configured to be calibrated in the first direction ( Figure 1 The device translates along direction A (as shown in the diagram), wherein two ranging terminals 2 of the free-space laser communication ranging device are respectively disposed on two displacement stages 1, and the two ranging terminals 2 are configured to acquire a first measuring distance between the two ranging terminals 2. A total station is disposed on one of the two displacement stages 1. A reflecting prism is disposed on the other of the two displacement stages 1, suitable for cooperating with the total station to obtain a second measuring distance between the total station and the reflecting prism. A controller is configured to control the movement of at least one of the two displacement stages 1 to change the distance between the two displacement stages 1, so as to calibrate the ranging accuracy of the free-space laser communication ranging device based on multiple first measuring distances and multiple second measuring distances.
[0036] In some exemplary embodiments, both ranging terminals 2 are equipped with optical transceiver modules ( Figure 1 The optical transceiver modules A and B are shown in the diagram. Each optical transceiver module includes a telescope and an optical fiber. The telescope has dual functions of transmitting and receiving optical signals. For example, the optical transceiver module of one ranging terminal 2 transmits a laser signal carrying a ranging pulse through the telescope. This laser signal propagates in free space and is received by the telescope of another ranging terminal 2, and vice versa, thus establishing a bidirectional free-space laser communication link.
[0037] The first direction is, for example, Figure 1 In the direction marked A, the optical signal propagates in the first direction after the free-space laser communication link is established. The first measured distance can refer to the straight-line distance between the transmitting or receiving ports of the telescopes of the two ranging terminals 2. Since the optical transceiver module is set on the displacement stage 1, the first measured distance will also change when the displacement stage 1 moves in the first direction. Theoretically, the change value is the distance the displacement stage 1 moves.
[0038] The basic principle of total station distance measurement is to calculate the distance by measuring the time difference between the emission of a laser pulse and its reflection back from the target. For example, when a total station emits a laser pulse, the pulse reaches a reflecting prism and is reflected back to the total station. The equipment records the round-trip time of the laser pulse. Combined with the known speed of light in air, the straight-line distance between the total station and the reflecting prism can be calculated. This distance is the second measurement distance.
[0039] Since the total station and an optical transceiver module are both mounted on a displacement stage 1, and the reflecting prism and another optical transceiver module are both mounted on another displacement stage 1, when the displacement stage 1 moves in the first direction, the second measurement distance will also change. The change in the second measurement distance is theoretically the same as the distance the displacement stage 1 moves.
[0040] On the one hand, compared to the free-space laser communication ranging device whose accuracy needs to be calibrated, the total station and reflecting prism, with their millimeter-level ranging accuracy, can provide reliable reference data closer to the true distance value. Therefore, the second measured distance obtained using the total station and reflecting prism can provide a precise benchmark for evaluating the accuracy of the first measured distance. On the other hand, in scenarios such as satellite orbit determination and navigation, the large size and power consumption of the total station make it difficult to integrate into the free-space laser communication system. Therefore, it is difficult to directly use the total station as a ranging tool. The free-space laser communication ranging device to be calibrated, however, is more likely to simultaneously complete ranging while performing long-distance communication. Therefore, using the high-precision benchmark value of the total station as a reference to quantify the ranging deviation of the ranging terminal 2 helps to calibrate and improve the ranging accuracy of the free-space laser communication ranging device, ensuring that the device can stably output accurate and reliable ranging data in the communication link. This achieves the calibration of the free-space laser communication ranging device on the ground before application.
[0041] In addition, the ranging terminal 2 also includes an electronics and optoelectronic module ( Figure 1 The electronics and optoelectronic modules A and B shown are used to realize the electronic and optoelectronic conversion functions required for communication and ranging. The optical transceiver module and the electronics and optoelectronic modules are integrated and installed in the same sealed housing and fixed as a whole to the reserved installation position of the displacement stage 1. The telescope, for example, uses a large-aperture reflective structure (aperture ≥150mm) to realize the transmission and reception of optical signals in long-distance free space links. The optical fiber, for example, uses single-mode polarization-maintaining fiber to connect the telescope and subsequent optoelectronic components, reducing polarization distortion and loss during optical signal transmission. The displacement stage 1 is, for example, a high-precision displacement stage 1 that can realize millimeter-level (e.g., ±0.01mm-level) movement, and the displacement dimension is one-dimensional (i.e., translation in the first direction). The displacement stage 1 uses, for example, a ball screw drive structure, in conjunction with a stepper motor drive, to achieve stable translation.
[0042] According to the accuracy calibration system of the free-space laser communication ranging device according to the embodiments of this disclosure, two ranging terminals 2 are respectively set on two displacement stages 1 spaced apart in a first direction, enabling a stable free-space laser communication link to be established between the two ranging terminals 2. The two ranging terminals 2 are configured to acquire a first measurement distance between them, which serves as a data sample for calibrating the ranging accuracy of the free-space laser communication ranging device. Furthermore, compared to the first measurement distance, a second measurement distance is obtained by setting a total station on one of the two displacement stages 1 and a reflecting prism on the other. Since the total station is a dedicated high-precision measuring device, the second measurement distance between the total station and the reflecting prism provides a reliable reference for the first measurement distance. Then, by configuring at least one of the two displacement stages 1 to translate in the first direction under the control of the controller, the distance between the two displacement stages 1 can be controlled and adjusted. Since the ranging terminal 2, the total station and the reflecting prism all move synchronously with the displacement stage 1, it is convenient to obtain multiple sets of first and second measurement distances in batches at different intervals and to compare and analyze them. This helps to calibrate the ranging accuracy of the free space laser communication ranging device based on multiple first and second measurement distances, and can better utilize the laser communication terminal for ranging, thus promoting the application and development of laser communication ranging devices in high-precision scenarios such as satellite orbit determination and navigation.
[0043] According to an embodiment of this disclosure, a ranging terminal 2 and a total station are configured to be spaced apart on a displacement stage 1 along a second direction. Another ranging terminal 2 and a reflecting prism are configured to be spaced apart on another displacement stage 1 along the second direction. The two ranging terminals 2 face each other in the first direction, the total station and the reflecting prism face each other in the first direction, and the second direction is orthogonal to the first direction.
[0044] With the two displacement stages 1 at a preset distance, the controller is configured to: repeatedly switch the total station and the free-space laser communication ranging device on and off, acquiring multiple first measurement distances and multiple second measurement distances respectively. Multiple differences are determined based on the multiple first measurement distances and multiple second measurement distances, and the average of these differences is used as the systematic error of the free-space laser communication ranging device to compensate for the fixed delay in the laser communication ranging device. Multiple standard deviations are determined based on the multiple first measurement distances and multiple second measurement distances to determine the repeatability accuracy in the ranging accuracy.
[0045] Figure 2 Schematic illustration Figure 1 The diagram shows the composition of the electronics and optoelectronic modules.
[0046] In some exemplary embodiments, such as Figure 2As shown, the electronics and optoelectronics module includes a laser, an electronics unit, a modulator, an optical amplifier, an optical beamsplitter, a low-noise optical amplifier, a filter, a detector, and a data recovery unit. The laser provides a continuous optical carrier. The modulator loads the electrical signal generated by the electronics unit onto the optical carrier to form a ranging optical pulse. The optical amplifier amplifies the power of the ranging optical pulse to meet the requirements of long-distance transmission. Then, the optical beamsplitter allows the transmitted and received light to share the same fiber optic link and telescope port. The low-noise optical amplifier and filter suppress background and stray light interference, improving the signal-to-noise ratio of the received signal. The detector converts the weak received optical signal into an electrical signal, ensuring effective detection of weak signals after long-distance transmission. Finally, the data recovery unit extracts clock information from the received optical signal to synchronize the received time with the local clock.
[0047] The electronics and optoelectronics module also includes a time-to-digital converter, which records the transmission or reception time of the ranging optical pulse.
[0048] Figure 3 Schematic illustration Figure 2 The diagram shown is a schematic of the ranging terminal.
[0049] In some exemplary embodiments, such as Figure 3 As shown, the two ranging terminals 2 include ranging terminal A (hereinafter referred to as A-end) and ranging terminal B (hereinafter referred to as B-end). After A-end and B-end establish a laser communication link, the ranging light pulse generated by A-end through the electronics and optoelectronic module A is transmitted through the optical transceiver module A. At the same time, the time-to-digital converter of A-end records the transmission time of the ranging light pulse. B-end receives this ranging light pulse and decodes it through the electronics and optoelectronic module B. The time-to-digital converter of B-end records the reception time of this ranging light pulse. Simultaneously, B-end also generates a ranging light pulse and transmits it to A-end, recording its own transmission time. After receiving the ranging light pulse from B-end, A-end also decodes it through its own electronics and optoelectronic module A, and the time-to-digital converter records the reception time. The transmission times of A and B-ends are, for example, directly generated by the electronics unit based on the local clock.
[0050] Ignoring atmospheric delay and relativistic effects, the first measurement distance is calculated based on the two-way asynchronous ranging formula, i.e., through... , , , The first measured distance is calculated using these four data points, as shown in the following formula:
[0051] (1);
[0052] in, The first measured distance, At the speed of light, For the receiving time of the B end, The time when terminal A sends the message. For the receiving time at end A, This refers to the time when the message is sent by the B-end.
[0053] In some exemplary embodiments, the preset distance between the two displacement stages 1 ranges from 0.8 to 1.5 km, for example, set to 1 km or 1.3 km. With the two displacement stages 1 at a fixed preset distance, the total station and the free-space laser communication ranging device simultaneously conducted multiple tests.
[0054] Because the components of electronic and optoelectronic modules generate fixed delays during signal transmission and conversion, these fixed delays refer to unavoidable time delays in the ranging link, such as optical modulation or amplification delays and detector response delays. These delays are relatively stable, do not fluctuate randomly with the measurement scenario, and do not change with the number of measurements or distance variations, making them difficult to completely eliminate through hardware design. This fixed delay leads to… , , , The discrepancies in these four data points lead to inaccuracies in the first measured distance calculated using the bidirectional asynchronous ranging formula. The actual testing process was as follows: before each test, the total station and the free-space laser communication ranging device were restarted. The test interval was set to, for example, 30 seconds. The specific results of the nine tests are shown in Table 1.
[0055] Table 1
[0056]
[0057] Figure 4 Schematic illustration Figure 1 The graph shows the variation of the difference between multiple tests when the distance between the two displacement stages is fixed.
[0058] like Figure 4 As shown, the horizontal axis represents the number of tests, and the vertical axis represents the difference between the first and second measured distances. When the number of tests is 9, the difference between the 9 tests varies within the range of 90.157-90.167 m. Furthermore, for example, the average value of the difference between the 9 tests can be calculated as the systematic error of the free-space laser communication ranging device.
[0059] According to the above embodiments of this disclosure, on the one hand, for the same preset distance, multiple sets of first and second measurement distances are collected, the difference between each set of data is calculated, and the average of multiple differences is taken as the final systematic error. This helps to compensate for the fixed delay based on this systematic error, thereby improving the accuracy of the first measurement distance. On the other hand, based on multiple sets of first and second measurement distances, the standard deviation of the two sets of data is calculated to reflect the dispersion of the multiple measurement results. This standard deviation is used as the repeatability accuracy in the ranging accuracy, which helps to evaluate the stability of the free-space laser communication ranging device under the same conditions for multiple measurements.
[0060] According to an embodiment of the present disclosure, the controller is further configured to: control at least one of the two displacement stages 1 to move to a target distance multiple times to obtain a plurality of new first measurement distances and a plurality of new second measurement distances, and determine the linearity in the ranging accuracy based on the plurality of new first measurement distances and the plurality of new second measurement distances.
[0061] According to embodiments of the present disclosure, the controller is configured to: perform linear fitting on a plurality of new first measurement distances and a plurality of new second measurement distances, and determine linearity based on the deviation of the slope of the fitted line from the ideal slope.
[0062] According to an embodiment of this disclosure, the controller is configured to: filter data on a first measured distance and remove abnormal data points that exceed a preset threshold.
[0063] In some exemplary embodiments, during each test, the distance between the two displacement stages 1 reaches the target distance by moving at least one of the displacement stages 1.
[0064] Figure 5 Schematic illustration Figure 1 The graph shows the change in the second measured distance during multiple tests when the distance between the two displacement stages changes.
[0065] like Figure 5 As shown, when the number of tests is 11, the target distance increases continuously during the 11 tests. For every 1cm increase in the target distance relative to the preset distance, the corresponding second measurement distance (the new second measurement distance) is obtained. Figure 5 The horizontal axis represents the increase in target distance relative to preset distance (in cm), and the vertical axis represents the second measured distance.
[0066] Among them, compared with the first measured distance, Figure 5The error between the second measured distance and the true value is smaller, for example, the maximum error range is 1-5mm. For example, when the target distance is 1km, the maximum error corresponding to the second measured distance is 4mm. Therefore, using a total station and a reflecting prism to measure different target distances is convenient for providing verification indicators for the ranging accuracy of free space laser communication ranging devices.
[0067] Figure 6 Schematic illustration Figure 1 The diagram shows the probability distribution of the first measured distance in multiple tests when the distance between the two displacement stages changes.
[0068] like Figure 6 As shown, when the number of tests is greater than 11, as the target distance increases, the corresponding first measurement distance (new first measurement distance) is continuously tested and obtained. Figure 6 The horizontal axis represents the first measured distance, and the vertical axis represents the probability distribution corresponding to the first measured distance. For example, first count the frequency of the first measured distance obtained from multiple tests, and then normalize the frequency to a probability (the sum of the probabilities of all measured values is 1), thus obtaining the probability distribution corresponding to the vertical axis.
[0069] Among them, through the Figure 6 The first measurement distances on the horizontal axis are filtered out, that is, abnormal data points that exceed the preset threshold are removed. Abnormal data points refer to data points that deviate significantly from most of the adjacent data (e.g., more than 2-3 times the standard deviation). Finally, the change curve of the first measurement distance is obtained.
[0070] In some exemplary embodiments, a result graph for evaluating the accuracy of the first measurement distance can be plotted based on the change curves of the first measurement distance and the second measurement distance. The horizontal axis represents, for example, the new second measurement distance, the vertical axis represents, for example, the new first measurement distance, and the ideal slope is defined as 1, meaning the free-space laser communication ranging device is in an ideal state (its ranging results are equivalent to the true values as those obtained using a total station).
[0071] According to the above embodiments of this disclosure, by continuously changing the distance between the two displacement stages 1, new first measurement distances and new second measurement distances are continuously obtained. Since the error corresponding to the second measurement distance is smaller, that is, the result obtained by using the total station and reflecting prism for distance measurement is closer to the true value, it is convenient to fit the slope of the straight line based on the new first measurement distance and the new second measurement distance. By combining the deviation of this slope from the ideal slope (i.e., linearity), a quantitative index of the accuracy of the free-space laser communication distance measuring device is given. In addition, by combining the evaluation of the distance dispersion of the free-space laser communication distance measuring device, it is beneficial to fully realize the calibration of the distance measuring accuracy of the free-space laser communication distance measuring device.
[0072] Figure 7 The flowchart illustrates a method for calibrating a free-space laser communication ranging device using an accuracy calibration system according to an embodiment of the present disclosure.
[0073] like Figure 7 As shown, as a second aspect of the present disclosure, a method for calibrating a free-space laser communication ranging device using the above-described accuracy calibration system is provided, including operations S710 to S730.
[0074] When operating the S710, with the two displacement stages at a preset distance, the total station and the free-space laser communication ranging device are switched on and off multiple times to obtain multiple first measurement distances and multiple second measurement distances.
[0075] In operation S720, multiple differences are determined based on multiple first measurement distances and multiple second measurement distances respectively. The average value of the multiple differences is used as the system error of the free space laser communication ranging device to compensate for the fixed delay in the laser communication ranging device.
[0076] In operation S730, multiple standard deviations are determined based on multiple first measurement distances and multiple second measurement distances, in order to determine the repeatability accuracy of the free-space laser communication ranging device based on the multiple standard deviations.
[0077] In some exemplary embodiments, the preset distance between the two displacement stages 1 ranges from 0.8 to 1.5 km, for example, set to 1 km or 1.3 km. With the two displacement stages 1 at a fixed preset distance, the total station and the free-space laser communication ranging device simultaneously conducted multiple tests.
[0078] According to the method for calibrating a free-space laser communication ranging device according to embodiments of this disclosure, on the one hand, for the same preset distance, a first measurement distance and a second measurement distance are collected multiple times, the difference between each set of data is calculated, and the average of multiple differences is taken as the final systematic error. This helps to achieve compensation for a fixed delay based on this systematic error, thereby improving the accuracy of the first measurement distance. On the other hand, the first measurement distance is used as a data sample for calibrating the ranging accuracy of the free-space laser communication ranging device, while the second measurement distance provides a reliable benchmark for the first measurement distance. Based on multiple sets of first and second measurement distances, the standard deviation of the two sets of data is calculated to reflect the dispersion of multiple measurement results. This standard deviation is used as the repeatability accuracy in the ranging accuracy, which helps to evaluate the stability of the free-space laser communication ranging device under the same conditions for multiple measurements.
[0079] According to embodiments of this disclosure, the method for calibrating a free-space laser communication ranging device further includes: repeatedly controlling the moving target distance of at least one of the two displacement stages 1 to obtain a plurality of new first measurement distances through two ranging terminals 2, and obtaining a plurality of new second measurement distances through a total station. The linearity of the free-space laser communication ranging device is determined based on the plurality of new first measurement distances and the plurality of new second measurement distances.
[0080] According to embodiments of this disclosure, determining linearity includes: performing linear fitting on a plurality of new first measured distances and a plurality of new second measured distances, and determining linearity based on the deviation of the slope of the fitted line from the ideal slope.
[0081] According to embodiments of this disclosure, the method for calibrating a free-space laser communication ranging device further includes: filtering data from a plurality of first measurement distances and removing abnormal data points that exceed a preset threshold.
[0082] In some exemplary embodiments, the change curves of the first measurement distance and the second measurement distance are first acquired, respectively. Then, the data are integrated and a final result graph is plotted to evaluate the accuracy of the first measurement distance. The horizontal axis represents, for example, the new second measurement distance, and the vertical axis represents, for example, the new first measurement distance. The ideal slope is defined as, for example, 1. The final determined linearity can serve as a quantitative indicator of the accuracy of the free-space laser communication ranging device.
[0083] According to the above embodiments of this disclosure, since the results obtained by using a total station and a reflecting prism for ranging are closer to the true values, comparing multiple new first measurement distances and multiple new second measurement distances helps to evaluate the ranging accuracy of the free-space laser communication ranging device. Combined with the evaluation of the ranging dispersion of the free-space laser communication ranging device, it is beneficial to fully realize the calibration of the ranging accuracy of the free-space laser communication ranging device, which helps to better utilize laser communication terminals for ranging, promotes the application and development of laser communication ranging devices in high-precision scenarios such as satellite orbit determination and navigation, and meets the application needs of integrated communication and ranging as much as possible.
[0084] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.
Claims
1. A precision calibration system for a free-space laser communication ranging device, characterized in that, include: Two displacement stages are spaced apart in a first direction, at least one of the two displacement stages is configured to translate in the first direction, wherein two ranging terminals of the free space laser communication ranging device are respectively disposed on the two displacement stages, and the two ranging terminals are configured to acquire a first measuring distance between the two ranging terminals; A total station, set on one of the two displacement stages; A reflecting prism, disposed on the other of the two displacement stages, is adapted to cooperate with the total station to obtain a second measuring distance between the total station and the reflecting prism; The controller is configured to control the movement of at least one of the two displacement stages to change the distance between the two displacement stages in order to calibrate the ranging accuracy of the free-space laser communication ranging device based on a plurality of first measured distances and a plurality of second measured distances.
2. The accuracy calibration system according to claim 1, characterized in that, One of the ranging terminals and the total station are configured to be spaced apart on one of the displacement stages along a second direction; another ranging terminal and the reflecting prism are configured to be spaced apart on another of the displacement stages along a second direction; and the two ranging terminals face each other in a first direction, the total station and the reflecting prism face each other in the first direction, and the second direction is orthogonal to the first direction.
3. The accuracy calibration system according to claim 2, characterized in that, When the two displacement stages are at a preset distance, the controller is configured to: By repeatedly switching the total station and the free-space laser communication ranging device on and off, multiple first measurement distances and multiple second measurement distances are obtained respectively; Multiple differences are determined based on multiple first measurement distances and multiple second measurement distances, and the average value of the multiple differences is used as the system error of the free space laser communication ranging device to compensate for the fixed delay in the laser communication ranging device. Multiple standard deviations are determined based on multiple first measurement distances and multiple second measurement distances, in order to determine the repeatability accuracy in the ranging accuracy based on the multiple said standard deviations.
4. The accuracy calibration system according to claim 3, characterized in that, The controller is also configured to: The distance measuring accuracy is determined by repeatedly controlling at least one of the two displacement stages to move to the target distance to obtain multiple new first measurement distances and multiple new second measurement distances, and by determining the linearity of the distance measuring accuracy based on the multiple new first measurement distances and multiple new second measurement distances.
5. The accuracy calibration system according to claim 4, characterized in that, The controller is configured to perform linear fitting on a plurality of the new first measurement distances and a plurality of the new second measurement distances, and determine the linearity based on the deviation of the slope of the fitted line from the ideal slope.
6. The accuracy calibration system according to claim 5, characterized in that, The controller is configured to filter data from multiple first measured distances and remove abnormal data points that exceed a preset threshold.
7. A method for calibrating a free-space laser communication ranging device using the accuracy calibration system according to any one of claims 1-6, characterized in that, include: With the two displacement stages at a preset distance, the total station and the free space laser communication ranging device are switched on and off multiple times to obtain multiple first measurement distances and multiple second measurement distances respectively. Multiple differences are determined based on multiple first measurement distances and multiple second measurement distances, and the average value of the multiple differences is used as the system error of the free space laser communication ranging device to compensate for the fixed delay in the laser communication ranging device. Multiple standard deviations are determined based on multiple first measurement distances and multiple second measurement distances to determine the repeatability accuracy of the free-space laser communication ranging device based on the multiple standard deviations.
8. The method according to claim 7, characterized in that, Also includes: The distance of at least one of the two displacement stages is controlled multiple times to move the target distance, so as to obtain multiple new first measurement distances through the two ranging terminals and multiple new second measurement distances through the total station; The linearity of the free-space laser communication ranging device is determined based on a plurality of the new first measurement distances and a plurality of the new second measurement distances.
9. The method according to claim 8, characterized in that, The determination of linearity includes: Linear fitting is performed on a plurality of the new first measurement distances and a plurality of the new second measurement distances, and the linearity is determined based on the deviation of the slope of the fitted line from the ideal slope.
10. The method according to claim 9, characterized in that, Also includes: Data filtering is performed on multiple first measured distances to remove abnormal data points that exceed a preset threshold.