A laser tracking and ranging device for measuring the flatness of synthetic aperture radar antennas.

Abstract

This invention provides a laser tracking and ranging device for measuring the flatness of a synthetic aperture radar antenna, comprising a high-precision laser rangefinder and a target. The high-precision laser rangefinder consists of a power supply module, a laser modulation module, an optomechanical module, a tracking module, and a data processing module. The power supply module receives external power and converts it into a secondary power supply usable by each module. The laser modulation module generates and modulates a laser beam, mixes the local oscillator laser and the echo laser, and performs photoelectric conversion. The optomechanical module shapes, expands, and emits the laser beam, receives the laser echo signal, and captures images of the target. The data processing module calculates the target distance information based on the ranging and mixing signal and identifies the target position information based on the target image. The tracking module controls the deflection of the optomechanical module to track the target. The target is a corner reflector device mounted on the antenna under test to reflect the laser beam emitted by the optomechanical module.

Description

Technical Field

[0001] This invention relates to the field of precision opto-electro-mechanical products technology, and in particular to a laser tracking and ranging device for measuring the flatness of synthetic aperture radar antennas. Background Technology

[0002] Antenna flatness measurement errors are a major cause of decreased measurement accuracy in synthetic aperture radar (SAR). Non-contact flatness measurements of antennas often employ photogrammetry, currently limited to satellite ground testing. Multiple cameras work together to perform photogrammetry, employing complex image processing algorithms to achieve high measurement accuracy. However, photogrammetry is highly demanding in terms of the testing environment, requiring precise calibration of the measurement system after each measurement, making the results heavily dependent on calibration errors. Design flaws such as aberrations in the camera's optical lenses also contribute to measurement errors; therefore, customized high-performance optical lenses are necessary. In the space environment, photogrammetry is affected by temperature, vibration, and other environmental factors, causing changes in system performance and leading to decreased on-orbit measurement accuracy. Therefore, using photogrammetry alone for on-orbit measurement of SAR antennas is difficult, prone to large errors, and unsuitable for achieving high-precision measurements.

[0003] Taking a stereo vision-based coordinate measurement method as an example, the flatness measurement accuracy using binocular photography is 1.26 mm (3σ). To achieve the accuracy of laser tracking ranging, up to 16 cameras need to work simultaneously, and high baseline accuracy is required. Applying this to space-based platforms for measuring synthetic aperture radar (SAR) is costly, technically complex, and difficult to guarantee in terms of measurement accuracy. Severe flatness errors can lead to a decline in the electrical performance of SAR antennas, such as gain loss, beam pointing deviation, or increased sidelobe density, ultimately affecting the radar's imaging quality and accuracy, thus negating the advantages of SAR over conventional radar in ranging accuracy and other aspects. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a laser tracking and ranging device for measuring the flatness of synthetic aperture radar antennas. It can directly measure the distance between multiple points of the antenna, thereby achieving high-precision measurement of the flatness of the deployed antenna. This effectively reduces the complexity of the measurement system, improves the system reliability, and has value for spaceborne applications.

[0005] This invention provides a laser tracking and ranging device for measuring the flatness of a synthetic aperture radar antenna, comprising a high-precision laser rangefinder and a target. The high-precision laser rangefinder consists of a power supply module, a laser modulation module, an optomechanical module, a tracking module, and a data processing module.

[0006] The power supply module is used to receive external power and convert it into a secondary power supply usable by the data processing module, tracking module, laser modulation module and optomechanical module;

[0007] The laser modulation module is used to generate and modulate a laser beam, mix the local oscillator laser and the echo laser, and photoelectrically convert the mixed laser signal into a ranging mixed signal.

[0008] The optomechanical module is used for shaping, expanding, and emitting the laser beam, receiving the laser echo signal, and capturing images of the target.

[0009] The data processing module is used to receive the ranging mixing signal generated by the laser modulation module and the target image captured by the optomechanical module, calculate the target distance information based on the ranging mixing signal, and identify the target position information based on the target image.

[0010] The tracking module is used to control the deflection of the optomechanical module according to the target position information to track the target;

[0011] The target is a corner reflector device, installed on the antenna under test, used to reflect the laser beam emitted by the optomechanical module.

[0012] Optionally, the laser modulation module includes a narrow linewidth laser, an electro-optic modulator, a radio frequency signal source, a laser amplifier, and a mixer;

[0013] The narrow linewidth laser is used to generate laser light;

[0014] The electro-optic modulator is used to modulate the laser frequency;

[0015] The radio frequency signal source is used to generate frequency-modulated electric drive signals;

[0016] The laser amplifier is used to amplify the modulated laser signal;

[0017] The mixer is used to mix the local oscillator laser and the echo laser and to perform photoelectric conversion on the mixed laser signal.

[0018] Optionally, the optomechanical module comprises a three-branch relay optical system consisting of a long-focal-length camera, a short-focal-length camera, a laser emission / reception coupling lens, a folding mirror, a beam splitter, a telescope group, and a fast-reflecting mirror. The three-branch relay optical system includes a laser emission and echo reception branch, a long-focal-length camera imaging branch, and a short-focal-length camera imaging branch. The laser emission and echo reception branch adopts a common optical path design for laser emission and echo reception. The laser emission and echo reception branch, the long-focal-length camera imaging branch, and the short-focal-length camera imaging branch achieve a common aperture design through a fast-reflecting mirror.

[0019] The laser emission and echo reception branch is used for laser beam shaping and expansion emission and laser echo signal reception.

[0020] The telephoto camera imaging branch is used for long-distance detection and imaging of the target area;

[0021] The short-focus camera imaging branch is used for short-range target identification and tracking.

[0022] Optionally, the data processing module uses FPGA-built-in image processing software, target tracking algorithm software, and ranging and mixing signal processing software to perform target image processing, target position positioning and precise tracking, and high-precision distance information calculation, respectively.

[0023] Optionally, the tracking module controls the deflection angle of the fast-reflecting mirror to change the direction of the camera's line of sight and the direction of the laser beam.

[0024] Optionally, the laser tracking ranging configuration has three operating modes: standby mode, detection mode, and ranging mode. Depending on the ranging task flow, it enters different operating modes:

[0025] After power-on, the high-precision laser rangefinder is in standby mode, the laser modulation module does not emit light, and the fast-reflecting mirror is locked in the initial position;

[0026] After receiving the command, the high-precision laser rangefinder enters the detection mode. After the optomechanical module works, the telephoto and short-focus cameras begin to detect and capture images of the target. The data processing module calculates the miss distance based on the target image, and the tracking module controls the deflection of the fast-reflecting mirror based on the miss distance to keep the target within the field of view.

[0027] After receiving the command, the high-precision laser rangefinder enters the ranging mode. The tracking module controls the optomechanical module to adjust multiple targets to the center of the field of view in sequence according to the miss distance. The laser modulation module emits a laser beam, and the data processing module performs ranging on multiple targets based on the ranging mixing signal generated by the laser modulation module.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention adopts a common optical path and common aperture design, which takes into account target imaging, target recognition and tracking and high-precision laser ranging functions. It overcomes the shortcomings of traditional non-common aperture common optical path laser tracking and ranging equipment that uses multiple channels to achieve tracking and aiming, reduces system complexity and improves the integration of integrated design.

[0030] 2. This invention controls the deflection angle of the fast-reflecting mirror to change the direction of the camera's line of sight and the direction of the laser beam. By switching between long-focus and short-focus cameras, it can perform imaging and tracking of the target at different distances, directly providing target position information for laser ranging. This avoids the need for an additional scanning compensation mirror and has the capability of "aiming and firing". Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is an architectural diagram of a laser tracking and ranging device for measuring the flatness of a synthetic aperture radar antenna;

[0033] Figure 2 This is a schematic diagram of the components of a high-precision laser rangefinder;

[0034] Figure 3 This is a schematic diagram of the working principle of the laser modulation module;

[0035] Figure 4 This is a schematic diagram of the working principle of the optomechanical module;

[0036] Figure 5 This is a graph showing the measurement error distribution of the target distance measurement results in the experimental flatness measurement of a synthetic aperture radar antenna. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention provides a laser tracking and ranging device for measuring the flatness of synthetic aperture radar antennas, comprising a high-precision laser rangefinder and a target, such as... Figure 1 As shown, the high-precision laser rangefinder is located at a specific position on the surface of the satellite's main structure, while the target is located at different positions on the synthetic aperture radar antenna (placed as needed). The high-precision laser rangefinder consists of a power supply module, a laser modulation module, an optomechanical module, a tracking module, and a data processing module. The power supply module, data processing module, tracking module, laser modulation module, and optomechanical module are all designed separately, such as... Figure 2 As shown, the modules are connected by electrical signal connectors and optical fibers, adopting an integrated design that integrates power supply, data processing, target tracking and laser modulation functions, and has the advantages of miniaturized and highly integrated design.

[0039] The power supply module receives external power and converts it into a secondary power supply usable by the data processing module, tracking module, laser modulation module, and optomechanical module.

[0040] The laser modulation module is used to generate and modulate a laser beam, mix the local oscillator laser and the echo laser, and photoelectrically convert the mixed laser signal into a ranging mixed signal.

[0041] Specifically, such as Figure 3 As shown, the laser modulation module includes a narrow-linewidth laser, an electro-optic modulator, an RF signal source, a laser amplifier, and a mixer. It has the capability of high bandwidth, high linearity laser frequency modulation, and high-energy laser emission. The narrow-linewidth laser is used to generate laser light, the electro-optic modulator is used to modulate the laser frequency, the RF signal source is used to generate a frequency-modulated electrical drive signal, the laser amplifier is used to amplify the modulated laser signal, and the mixer is used to mix the local oscillator laser and the echo laser and perform photoelectric conversion on the mixed laser signal.

[0042] The laser modulation module employs double-sideband modulated laser frequency sweep ranging technology. By generating two scanning signals with opposite frequencies, it eliminates ranging errors caused by target motion, effectively improving the accuracy of laser interferometric ranging, with a maximum ranging rate of 1kHz. It also uses optical frequency scanning nonlinearity suppression technology to construct a frequency source with high bandwidth, high frequency resolution, and fast linear frequency sweeping, effectively suppressing measurement errors caused by optical frequency scanning nonlinearity and improving the stability and accuracy of interference signals.

[0043] The optomechanical module is used for shaping, expanding, and transmitting the laser beam, receiving the laser echo signal, and capturing images of the target.

[0044] Specifically, such as Figure 4 As shown, the optomechanical module consists of a long-focal-length camera, a short-focal-length camera, a laser emission / reception coupling lens, a folding mirror 1 / 2, a beam splitter 1 / 2, a telescope group 1 / 2, and a fast-reflecting mirror, forming a three-branch relay optical system. This three-branch relay optical system includes laser emission and echo reception branches (such as...). Figure 4 (as shown by the green line in the middle), the imaging branch of the telephoto camera and the imaging branch of the short-focal-length camera (such as...) Figure 4 As shown by the red line, the incident light from the target is split into two beams by beam splitter 2, which then enter the telephoto and short-focus cameras respectively. The laser emission and echo reception branches adopt a common optical path design for laser emission and echo reception (e.g., Figure 4 (As shown by the blue line in the middle) The laser emission and echo reception branch, the telephoto camera imaging branch, and the short-focus camera imaging branch are designed with a common aperture through a fast-reflecting mirror. The fast-reflecting mirror provides angular variation in two degrees of freedom, X and Y, and can achieve spatial pointing variation of ±1.5° for each degree of freedom. It can cover multiple targets within a certain distance range. The laser emission and echo reception branch is used for laser beam shaping, beam expansion, emission, and laser echo signal reception. The telephoto camera imaging branch is used for long-range detection and imaging of the target area. The short-focus camera imaging branch is used for short-range identification and tracking of the target.

[0045] The data processing module is used to receive the ranging mixing signal generated by the laser modulation module and the target image captured by the optomechanical module, calculate the target distance information based on the ranging mixing signal, and identify the target position information based on the target image.

[0046] Specifically, the data processing module processes data from the FPGA and peripheral circuits. The FPGA controls the ADC to acquire ranging and mixing signals. The FPGA receives and stores target images captured by the camera. The FPGA has built-in image processing software, target tracking algorithm software, and ranging and mixing signal processing software, which are used for target image processing, target position positioning and accurate tracking, and high-precision distance information calculation, respectively.

[0047] The tracking module is used to control the deflection of the optomechanical module based on the target position information to track the target.

[0048] Specifically, the tracking module controls the deflection angle of the fast-reflecting mirror to change the camera's line of sight, ensuring that the camera's line of sight always points to the target position. It also changes the laser beam's direction to ensure that the laser beam is aimed at the target and to generate a laser echo.

[0049] The target is a corner reflector device, mounted on the antenna under test, used to reflect the laser beam emitted by the optomechanical module.

[0050] The laser tracking ranging system has three operating modes: standby mode, detection mode, and ranging mode. It enters the appropriate operating mode based on the ranging task flow.

[0051] After power-on, the high-precision laser rangefinder is in standby mode, the laser modulation module does not emit light, and the fast-reflecting mirror is locked in the initial position;

[0052] After receiving the command, the high-precision laser rangefinder enters the detection mode. After the optomechanical module works, the telephoto and short-focus cameras begin to detect and capture images of the target. The data processing module calculates the miss distance based on the target image, and the tracking module controls the deflection of the fast-reflecting mirror based on the miss distance to keep the target within the field of view.

[0053] After receiving the command, the high-precision laser rangefinder enters the ranging mode. The tracking module controls the optomechanical module to adjust multiple targets to the center of the field of view in sequence according to the miss distance. The laser modulation module emits a laser beam, and the data processing module performs ranging on multiple targets based on the ranging mixing signal generated by the laser modulation module.

[0054] The performance of the present invention was analyzed through simulation experiments, as follows:

[0055] refer to Figure 2The system architecture diagram illustrates the construction of an experimental testing system. A planarity measurement experiment of a synthetic aperture radar antenna was conducted. Within the tracking field of view (±1.5°), measurements were performed on multiple targets located at different positions on the antenna. The measurement error from 100 measurements was statistically analyzed. Figure 5 As shown, the statistical results of the measurement error have a mean of 95.52 μm and a standard deviation of 3.10 μm. In 100 experiments, the measurement error exceeded 100 μm in 3 of the measurements, with the maximum error being 101.47 μm and the minimum error being 90.01 μm.

[0056] The present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A laser tracking and ranging device for measuring the flatness of a synthetic aperture radar antenna, characterized in that, It includes a high-precision laser rangefinder and a target. The high-precision laser rangefinder consists of a power supply module, a laser modulation module, an optomechanical module, a tracking module, and a data processing module. The power supply module is used to receive external power and convert it into a secondary power supply usable by the data processing module, tracking module, laser modulation module and optomechanical module; The laser modulation module is used to generate and modulate a laser beam, mix the local oscillator laser and the echo laser, and photoelectrically convert the mixed laser signal into a ranging mixed signal. The optomechanical module is used for shaping, expanding, and emitting the laser beam, receiving the laser echo signal, and capturing images of the target. The data processing module is used to receive the ranging mixing signal generated by the laser modulation module and the target image captured by the optomechanical module, calculate the target distance information based on the ranging mixing signal, and identify the target position information based on the target image. The tracking module is used to control the deflection of the optomechanical module according to the target position information to track the target; The target is a corner reflector device, which is installed on the antenna under test and is used to reflect the laser beam emitted by the optomechanical module; The laser modulation module includes a narrow linewidth laser, an electro-optic modulator, a radio frequency signal source, a laser amplifier, and a mixer; The narrow linewidth laser is used to generate laser light; The electro-optic modulator is used to modulate the laser frequency; The radio frequency signal source is used to generate frequency-modulated electric drive signals; The laser amplifier is used to amplify the modulated laser signal; The mixer is used to mix the local oscillator laser and the echo laser and to perform photoelectric conversion on the mixed laser signal. The optomechanical module consists of a long-focal-length camera, a short-focal-length camera, a laser emission / reception coupling lens, a folding mirror, a beam splitter, a telescope group, and a fast-reflecting mirror, forming a three-branch relay optical system. The three-branch relay optical system includes a laser emission and echo reception branch, a long-focal-length camera imaging branch, and a short-focal-length camera imaging branch. The laser emission and echo reception branch adopts a common optical path design for laser emission and echo reception. The laser emission and echo reception branch, the long-focal-length camera imaging branch, and the short-focal-length camera imaging branch achieve a common aperture design through a fast-reflecting mirror. The laser emission and echo reception branch is used for laser beam shaping and expansion emission and laser echo signal reception. The telephoto camera imaging branch is used for long-distance detection and imaging of the target area; The short-focal-length camera imaging branch is used for short-range detection and imaging of the target area.

2. The laser tracking and ranging device for measuring the flatness of a synthetic aperture radar antenna according to claim 1, characterized in that, The data processing module uses FPGA-built-in image processing software, target tracking algorithm software, and ranging and mixing signal processing software to process target images, locate and accurately track target positions, and calculate high-precision distance information, respectively.

3. The laser tracking and ranging device for measuring the flatness of a synthetic aperture radar antenna according to claim 2, characterized in that, The tracking module controls the deflection angle of the fast-reflecting mirror to change the direction of the camera's line of sight and the laser beam.

4. The laser tracking and ranging device for measuring the flatness of a synthetic aperture radar antenna according to claim 3, characterized in that, The laser tracking and ranging configuration has three operating modes: standby mode, detection mode, and ranging mode. It enters different operating modes according to the ranging task flow: After power-on, the high-precision laser rangefinder is in standby mode, the laser modulation module does not emit light, and the fast-reflecting mirror is locked in the initial position; After receiving the command, the high-precision laser rangefinder enters the detection mode. After the optomechanical module works, the telephoto and short-focus cameras begin to detect and capture images of the target. The data processing module calculates the miss distance based on the target image, and the tracking module controls the deflection of the fast-reflecting mirror based on the miss distance to keep the target within the field of view. After receiving the command, the high-precision laser rangefinder enters the ranging mode. The tracking module controls the optomechanical module to adjust multiple targets to the center of the field of view in sequence according to the miss distance. The laser modulation module emits a laser beam, and the data processing module performs ranging on multiple targets based on the ranging mixing signal generated by the laser modulation module.

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