Passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling

Abstract

This invention relates to the field of coherent wind lidar technology, and discloses a passive solid-state beam scanning system based on wavelength tuning and dispersive grating coupling. A tunable laser unit outputs multiple narrow-linewidth lasers of different wavelengths; a beam-splitting modulation unit divides them into emitted light and local oscillator light, and pulse-modulates the emitted light; a dispersive grating scanning unit forms scanning beams with different exit directions from the emitted light of different wavelengths; a wavelength monitoring unit acquires the actual wavelength of the emitted light, and a grating state monitoring unit acquires the grating state parameters; a joint calibration and compensation unit determines the actual exit angle based on the actual wavelength of the emitted light and the grating state parameters, and determines the Doppler velocity conversion coefficient based on the actual wavelength of the emitted light; a coherent receiving and solving unit calculates the radial wind speed, and a wind parameter inversion unit inverts the wind parameter information. This invention can jointly correct the scanning direction and velocity conversion, improving the accuracy of wind parameter information inversion and long-term wind measurement stability.

Description

Technical Field

[0001] This invention relates to the field of coherent wind lidar technology, specifically a passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling. Background Technology

[0002] Coherent wind lidar typically uses a narrow-linewidth laser to emit a probe beam into the atmosphere and receives the atmospheric backscattered echo signal generated by aerosols. The Doppler frequency shift is obtained by measuring the coherent beat frequency between the echo signal and the local oscillator beam, and then the radial wind speed in the corresponding probe direction is calculated. To obtain wind speed, wind direction, or three-dimensional wind field information, wind lidar usually needs to point the probe beam in multiple different directions. Existing technologies mainly include mechanical mirror scanning, rotating prism scanning, optical phased array scanning, and solid-state scanning based on wavelength tuning and dispersion gratings. Among these, the solid-state scanning method based on wavelength tuning and dispersion gratings can change the laser wavelength to form different exit directions after the beam passes through the grating, thus achieving beam scanning without mechanical rotating parts.

[0003] However, existing solid-state scanning technologies based on wavelength tuning and dispersive gratings primarily focus on the theoretical correspondence between wavelength and scanning direction, typically using them as beam deflection mechanisms in ordinary lidar systems. They fail to adequately consider the velocity coupling problem when applied to coherent wind lidar. In coherent wind lidar, the actual wavelength of the emitted light not only affects the actual exit angle of the scanning beam after passing through the dispersive grating but also participates in Doppler velocity conversion. Furthermore, the operating state of the dispersive grating can change due to temperature drift, assembly deviations, or long-term operational stress. If the scanning direction and radial wind speed calculation are still performed according to the commanded wavelength, theoretical grating parameters, and a fixed center wavelength, it is easy for scanning direction errors and velocity conversion errors to overlap, thereby reducing the accuracy of wind speed, wind direction, or three-dimensional wind field information retrieval. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling. This system solves the problem that when existing wavelength-tuned dispersion grating scanning technology is applied to coherent wind lidar, the scanning direction and velocity conversion are not jointly corrected by combining the actual wavelength of the emitted light and the grating state parameters, resulting in reduced accuracy of wind parameter information inversion.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling, comprising: A tunable laser unit is used to output multiple narrow-linewidth lasers of different wavelengths; The beam splitting modulation unit is used to split the narrow linewidth laser into emitted light and local oscillator light, and to pulse modulate the emitted light; A dispersive grating scanning unit is used to receive the pulse-modulated emitted light and to make the emitted light of different wavelengths form scanning beams with different emission directions; The wavelength monitoring unit is used to obtain the actual wavelength of the emitted light before it enters the dispersive grating scanning unit; A grating state monitoring unit is used to acquire the grating state parameters of the dispersive grating scanning unit; The joint calibration and compensation unit is used to determine the actual emission angle of the scanning beam based on the actual wavelength of the emitted light and the grating state parameters, and to determine the Doppler velocity conversion coefficient corresponding to the scanning beam based on the actual wavelength of the emitted light. The coherent receiving and processing unit is used to receive the atmospheric backscattered echo signal corresponding to the scanning beam, perform beat frequency processing on the atmospheric backscattered echo signal and the local oscillator light to obtain the beat frequency, and calculate the radial wind speed in the current scanning direction based on the Doppler velocity conversion coefficient and the beat frequency. The wind parameter inversion unit is used to invert wind parameter information based on the actual emission angle and radial wind speed corresponding to multiple current scanning directions.

[0006] Preferably, the tunable laser unit includes a narrow linewidth tunable laser and a wavelength controller; The wavelength controller is used to send wavelength tuning commands to the narrow linewidth tunable laser according to a preset scanning sequence. The narrow linewidth tunable laser is used to output the plurality of narrow linewidth lasers of different wavelengths according to the wavelength tuning command.

[0007] Preferably, the beam splitting and modulation unit includes an optical fiber beam splitter and an acousto-optic modulator; The fiber optic beam splitter is used to split the narrow linewidth laser into the emitted light and the local oscillator light; The acousto-optic modulator is used to pulse-modulate the emitted light and provide the acousto-optic frequency shift to the coherent receiving and processing unit.

[0008] Preferably, the dispersive grating scanning unit includes a collimating optical component, a dispersive grating, and an emitting optical component; The collimating optical component is used to collimate the pulse-modulated emitted light. The dispersion grating is used to perform dispersion deflection on the aligned emitted light; The emission optical component is used to shape the dispersion-deflected emitted light into the scanning beam. The dispersive grating scanning unit does not have any mechanical rotating parts.

[0009] Preferably, the wavelength monitoring unit includes a sampling spectrometer and a wavelength measuring device; The sampling beam splitter is disposed between the beam splitting modulation unit and the dispersion grating scanning unit, and is used to separate the sample light from the emitted light before it enters the dispersion grating scanning unit; The wavelength measuring device is used to obtain the actual wavelength of the emitted light based on the sampled light.

[0010] Preferably, the grating status monitoring unit includes a temperature sensor; The temperature sensor is used to obtain the grating temperature of the dispersive grating scanning unit; The grating state parameters include the grating temperature; The joint calibration compensation unit is used to perform temperature correction on the grating period of the dispersive grating scanning unit according to the grating temperature, so as to obtain the temperature-corrected grating period.

[0011] Preferably, the joint calibration compensation unit stores a joint calibration table; The joint calibration table includes the correspondence between the preset wavelength, the actual wavelength of the emitted light, the grating state parameters, the actual emission angle, the unit vector of the emission direction, and the Doppler velocity conversion coefficient; The joint calibration compensation unit is used to query the joint calibration table based on the actual wavelength of the emitted light and the grating state parameters to obtain the actual emission angle, the unit vector of the emission direction, and the Doppler velocity conversion coefficient.

[0012] Preferably, the joint calibration compensation unit is further configured to determine the diffraction direction of the scanning beam according to the grating diffraction relationship based on the actual wavelength of the emitted light, the period of the temperature correction grating, the incident angle and the diffraction order, and to use the angle corresponding to the diffraction direction as the actual exit angle.

[0013] Preferably, the coherent receiving and processing unit is used to determine the Doppler frequency shift based on the beat frequency and the acousto-optic frequency shift. The coherent receiving and solving unit is also used to determine the Doppler velocity conversion factor based on the actual wavelength of the emitted light, and to use the Doppler velocity conversion factor to convert the Doppler frequency shift to obtain the radial wind speed.

[0014] Preferably, the wind parameter inversion unit is used to obtain at least three radial wind velocities and emission direction unit vectors corresponding to the current scanning direction; The wind parameter inversion unit is also used to establish a wind vector observation relationship based on the radial wind speed and the unit vector of the launch direction, and to solve for the wind vector to be inverted based on multiple wind vector observation relationships; The wind parameter information includes at least one of wind speed, wind direction, and three-dimensional wind field information.

[0015] This invention provides a passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling. It offers the following advantages: 1. This invention obtains the actual wavelength of the emitted light before entering the dispersive grating scanning unit through a wavelength monitoring unit, acquires the grating state parameters of the dispersive grating scanning unit through a grating state monitoring unit, and determines the actual exit angle of the scanning beam based on the actual wavelength of the emitted light and the grating state parameters through a joint calibration and compensation unit. Simultaneously, it determines the Doppler velocity conversion coefficient based on the actual wavelength of the emitted light, enabling scanning direction compensation and velocity conversion compensation to be completed collaboratively. Therefore, it avoids the superposition of scanning direction errors and radial wind speed conversion errors that occur when calculating solely based on the command wavelength, theoretical grating parameters, or a fixed center wavelength, thus improving the accuracy of wind parameter information inversion.

[0016] 2. This invention directly obtains the actual wavelength of the emitted light through a wavelength monitoring unit, so that the system no longer equates the wavelength tuning command with the actual working wavelength. Even if the tunable laser unit has tuning lag, temperature drift, or wavelength locking deviation, the actual wavelength of the emitted light entering the dispersive grating scanning unit can be used as the basis for compensation, thereby improving the consistency of scanning direction determination and radial wind speed calculation.

[0017] 3. This invention acquires the grating state parameters of the dispersive grating scanning unit through a grating state monitoring unit, and the joint calibration and compensation unit corrects the actual emission angle based on the grating state parameters. This reduces the scanning beam direction deviation caused by temperature changes, assembly deviations, or long-term operating stress of the dispersive grating, improving the angular reliability of each current scanning direction and the long-term wind measurement stability. Attached Figure Description

[0018] Figure 1 This is a system structure block diagram of the passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling of the present invention. Figure 2 This is a flowchart illustrating the adaptive scanning control of the passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will now be clearly and completely described 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.

[0020] This invention provides a passive solid-state beam scanning system based on wavelength tuning and dispersive grating coupling, suitable for coherent wind lidar scenarios. Narrow-linewidth lasers of different wavelengths are used to form scanning beams with different exit directions after passing through a dispersive grating scanning unit. During wind measurement calculations, instead of directly using wavelength tuning commands or theoretical scanning angles, the actual wavelength of the emitted light is obtained through a wavelength monitoring unit, and grating state parameters are obtained through a grating state monitoring unit. A joint calibration and compensation unit simultaneously corrects the actual exit angle of the scanning beam and the Doppler velocity conversion coefficient, enabling the wind parameter inversion unit to invert wind parameter information based on the actual exit angle and radial wind speed.

[0021] This invention addresses the coupling error problem arising when wavelength-tuned grating scanning is applied to wind measurement lidar. Specifically, in conventional lidar scanning, wavelength tuning primarily affects the scanning direction; however, in coherent wind measurement lidar, the actual wavelength of the emitted light not only affects the actual exit angle of the dispersive grating scanning unit but also participates in the radial wind speed calculation. When the actual wavelength of the emitted light deviates from the wavelength tuning command, or when the grating period of the dispersive grating scanning unit drifts due to temperature changes, if the theoretical wavelength and theoretical exit angle are still used for wind measurement calculation, the errors in judging the current scanning direction and the radial wind speed calculation will be superimposed, thus affecting the accuracy of wind speed, wind direction, or three-dimensional wind field information.

[0022] Reference Figure 1 In one embodiment, this invention provides a passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling, comprising: A tunable laser unit is used to output multiple narrow-linewidth lasers of different wavelengths; The beam splitting modulation unit is used to split the narrow linewidth laser into emitted light and local oscillator light, and to pulse modulate the emitted light; A dispersive grating scanning unit is used to receive the pulse-modulated emitted light and to make the emitted light of different wavelengths form scanning beams with different emission directions; The wavelength monitoring unit is used to obtain the actual wavelength of the emitted light before it enters the dispersive grating scanning unit; A grating state monitoring unit is used to acquire the grating state parameters of the dispersive grating scanning unit; The joint calibration and compensation unit is used to determine the actual emission angle of the scanning beam based on the actual wavelength of the emitted light and the grating state parameters, and to determine the Doppler velocity conversion coefficient corresponding to the scanning beam based on the actual wavelength of the emitted light. The coherent receiving and processing unit is used to receive the atmospheric backscattered echo signal corresponding to the scanning beam, perform beat frequency processing on the atmospheric backscattered echo signal and the local oscillator light to obtain the beat frequency, and calculate the radial wind speed in the current scanning direction based on the Doppler velocity conversion coefficient and the beat frequency. The wind parameter inversion unit is used to invert wind parameter information based on the actual emission angle and radial wind speed corresponding to multiple current scanning directions.

[0023] Specifically, wind parameter information includes at least one of wind speed, wind direction, and three-dimensional wind field information. When multiple current scanning directions meet the conditions for three-dimensional wind vector inversion, the wind parameter inversion unit outputs three-dimensional wind field information; when multiple current scanning directions are located on the same scanning plane or the measurement mode only requires a planar wind field, the wind parameter inversion unit outputs the wind speed and wind direction within that scanning plane.

[0024] The tunable laser unit includes a narrow-linewidth tunable laser and a wavelength controller. The narrow-linewidth tunable laser can be a narrow-linewidth fiber laser, a narrow-linewidth semiconductor laser, or an external cavity tunable laser. Preferably, the narrow-linewidth laser output by the narrow-linewidth tunable laser is located in the near-infrared band suitable for atmospheric coherent wind measurement, such as the 1550 nm band.

[0025] The wavelength controller sends wavelength tuning commands to the narrow-linewidth tunable laser according to a preset scanning sequence. The preset scanning sequence includes multiple preset wavelengths and the corresponding dwell time for each preset wavelength. Each preset wavelength corresponds to a current scanning direction. The wavelength controller can scan according to an equally spaced wavelength sequence, or it can perform non-equally spaced wavelength scans according to the wind measurement line of sight required by the wind parameter inversion unit.

[0026] In a preferred embodiment, the preset scanning sequence is arranged according to the directional combination required for the wind measurement task. For example, when performing multi-line-of-sight wind measurement, the wavelength controller is preferentially tuned to multiple current scanning directions that meet the requirements of the current wind parameter inversion; when the atmospheric backscattered echo signal in a certain direction is weak, the wavelength controller extends the dwell time corresponding to the preset wavelength to improve the radial wind speed stability of the current scanning direction.

[0027] The beam splitting and modulation unit includes an optical fiber beam splitter and an acousto-optic modulator. The optical fiber beam splitter splits the narrow-linewidth laser into emitted light and local oscillator light. The emitted light enters the acousto-optic modulator, which pulses the emitted light to form pulsed light for atmospheric detection. The acousto-optic modulator also provides an acousto-optic frequency shift to the coherent receiving and processing unit.

[0028] The local oscillator light does not pass through the dispersive grating scanning unit, but remains from the same source as the emitted light. Since the local oscillator light and the emitted light originate from the same narrow-linewidth laser, the impact of phase noise on beat frequency extraction can be reduced during coherent reception. When calculating radial wind speed, the coherent receiving and processing unit determines the Doppler frequency shift from the beat frequency by combining the acousto-optic frequency shift, and then uses the Doppler velocimetry conversion factor to convert the Doppler frequency shift into radial wind speed.

[0029] It should be noted that the specific frequency shifting method, pulse modulation method, and coherent beat frequency principle of the acousto-optic modulator can all be implemented using conventional methods in this field, and this embodiment will not elaborate on their formulas.

[0030] The dispersion grating scanning unit includes a collimating optical component, a dispersion grating, and an emission optical component. The collimating optical component collimates the pulse-modulated emitted light, ensuring it enters the dispersion grating at a stable angle. The dispersion grating deflects the collimated emitted light. The emission optical component shapes the deflected emitted light into a scanning beam and emits it into the atmospheric detection area.

[0031] Dispersion gratings can be transmission-type, reflection-type, blazed, or volume Bragg gratings. The type of dispersion grating can be selected based on the scanning range, beam efficiency, system size, and operating wavelength. The dispersion grating scanning unit has no mechanical rotating parts; the exit direction of the scanning beam is determined by the actual wavelength of the emitted light and the dispersion characteristics of the dispersion grating.

[0032] In practical applications, the actual exit angle of the dispersive grating scanning unit is affected not only by the actual wavelength of the emitted light but also by the grating state parameters. These parameters may include at least one of the following: grating temperature, grating mounting condition, and grating base thermal deformation condition. In a preferred embodiment, the grating state parameters include at least the grating temperature. The joint calibration and compensation unit performs temperature correction on the grating period of the dispersive grating scanning unit based on the grating temperature, obtaining a temperature-corrected grating period. Then, based on the actual wavelength of the emitted light, the temperature-corrected grating period, the incident angle, and the diffraction order, it determines the actual exit angle of the scanning beam according to the grating diffraction relationship.

[0033] The grating diffraction relationship is a conventional optical calculation method in this field. This embodiment only describes its calculation logic and does not list the conventional formula here.

[0034] The wavelength monitoring unit includes a sampling beam splitter and a wavelength measuring device. The sampling beam splitter is located between the beam splitting modulation unit and the dispersion grating scanning unit, and is used to separate the sample light from the emitted light before it enters the dispersion grating scanning unit. The wavelength measuring device is used to obtain the actual wavelength of the emitted light based on the sample light.

[0035] The wavelength measuring device can be a wavelength meter, a Fabry-Perot etalon, a fiber Bragg grating wavelength detection structure, or an array spectral detection structure. The actual wavelength of the emitted light output by the wavelength measuring device is sent to the joint calibration and compensation unit. The joint calibration and compensation unit does not use the wavelength tuning command as the final calculation basis, but uses the actual wavelength of the emitted light as the basis for calculating the actual emission angle and the Doppler velocity conversion factor.

[0036] By using the above settings, the actual wavelength deviation caused by tuning lag, temperature drift, or driving current fluctuations in narrow-linewidth tunable lasers can be avoided from being directly included in the wind measurement calculation, thereby improving the accuracy of the correspondence between the current scanning direction and radial wind speed.

[0037] The grating status monitoring unit includes a temperature sensor. The temperature sensor is used to acquire the grating temperature of the dispersive grating scanning unit. The temperature sensor can be located on the back of the dispersive grating, on the grating mounting base, or in a heat-sensitive area near the dispersive grating. The grating temperature output by the temperature sensor is sent as a grating status parameter to the joint calibration and compensation unit.

[0038] In one extended embodiment, the grating state monitoring unit further includes an attitude sensor or a strain sensor. The attitude sensor is used to detect changes in the mounting angle of the dispersive grating scanning unit, and the strain sensor is used to detect the thermal deformation state of the dispersive grating mount. When the grating state parameters include the grating mounting state or the thermal deformation state of the grating base, the joint calibration and compensation unit further corrects the actual emission angle by incorporating these grating state parameters.

[0039] The joint calibration and compensation unit stores a joint calibration table. The joint calibration table includes the correspondence between the preset wavelength, the actual wavelength of the emitted light, the grating state parameters, the actual emission angle, the unit vector of the emission direction, and the Doppler velocity conversion coefficient.

[0040] The joint calibration table can be obtained through factory calibration, field calibration, or self-updating calibration during operation. During factory calibration, the system sequentially outputs multiple preset wavelengths and measures the actual emission angle of the scanning beam at different grating temperatures, obtaining the correspondence between the actual wavelength of the emitted light, grating state parameters, and the actual emission angle. Simultaneously, the joint calibration compensation unit determines the Doppler velocimetry conversion coefficient corresponding to the scanning beam based on the actual wavelength of the emitted light and writes it, along with the actual emission angle and the unit vector of the emission direction, into the joint calibration table.

[0041] During system operation, the joint calibration and compensation unit receives the actual wavelength of the emitted light output by the wavelength monitoring unit and the grating state parameters output by the grating state monitoring unit. The joint calibration and compensation unit first queries the joint calibration table based on the actual wavelength of the emitted light and the grating state parameters. If a matching item exists in the joint calibration table, the actual emission angle, emission direction unit vector, and Doppler velocity conversion coefficient are directly obtained. If no matching item exists in the joint calibration table, the joint calibration and compensation unit performs interpolation compensation between adjacent calibration points to obtain the actual emission angle, emission direction unit vector, and Doppler velocity conversion coefficient corresponding to the current scanning direction.

[0042] The emission direction unit vector is determined based on the actual emission angle and the installation orientation of the dispersive grating scanning unit in the system coordinate system. The actual emission angle describes the angle of the scanning beam relative to the optical axis of the dispersive grating scanning unit, while the emission direction unit vector describes the three-dimensional direction cosine of the scanning beam in the system coordinate system. The wind parameter inversion unit uses the emission direction unit vector to establish the wind vector observation relationship.

[0043] In a preferred embodiment, the joint calibration compensation unit further calculates the joint effective weight for each current scanning direction. The joint effective weight is used to characterize whether the actual emission angle and radial wind speed corresponding to the current scanning direction are suitable for participation in wind parameter inversion. The joint effective weight is calculated as follows: ; in, This represents the joint effective weight for the i-th current scan direction; This represents the wavelength locking quality corresponding to the i-th current scanning direction; This represents the quality of the frame rate corresponding to the i-th current scanning direction; This represents the normalized deviation of the actual wavelength of the emitted light corresponding to the i-th current scanning direction from the wavelength matched in the joint calibration table; This represents the normalized deviation of the grating state parameters corresponding to the i-th current scanning direction relative to the matching state of the joint calibration table; This indicates the radial wind speed consistency deviation in the i-th current scanning direction during repeated scans; , and These represent the weighting coefficients for the corresponding deviation terms.

[0044] The aforementioned joint effective weight does not evaluate the actual wavelength of the emitted light, grating state parameters, or beat spectrum quality separately. Instead, it combines the evaluation of scanning angle reliability and velocity measurement reliability, enabling the wind parameter inversion unit to prioritize the current scanning direction for inversion, given that both angle and velocity measurement are reliable. When the joint effective weight is lower than a preset weight threshold, the wind parameter inversion unit can reduce the weight of the current scanning direction in the wind parameter inversion, or mark the radial wind speed corresponding to the current scanning direction as data to be remeasured.

[0045] The coherent receiving and processing unit includes a receiving optical component, a photodetector, and a frequency calculation module. The receiving optical component receives the atmospheric backscattered echo signal corresponding to the scanning beam and guides it to the photodetector. The photodetector performs beat frequency processing on the atmospheric backscattered echo signal and the local oscillator light to obtain an electrical signal. The frequency calculation module extracts the beat frequency from the electrical signal.

[0046] The coherent receiving and processing unit determines the Doppler frequency shift based on the beat frequency and the acousto-optic frequency shift. The coherent receiving and processing unit also determines the Doppler velocity conversion factor based on the actual wavelength of the emitted light, and uses the Doppler velocity conversion factor to convert the Doppler frequency shift to obtain the radial wind speed.

[0047] Unlike traditional fixed-wavelength wind measurement, this invention uses a different actual wavelength for each current scanning direction. Therefore, the Doppler velocity conversion factor varies with the actual wavelength of the emitted light. When calculating radial wind speed, the coherent receiving and processing unit calls upon the corresponding Doppler velocity conversion factor for each current scanning direction, instead of using a uniform conversion factor corresponding to a fixed center wavelength.

[0048] It should be noted that the basic physical relationships of coherent beat frequency, Doppler frequency shift extraction, and radial wind speed conversion are conventional technologies in the field of coherent wind measurement radar. This implementation method is explained by calculation logic and does not list conventional formulas.

[0049] The wind parameter inversion unit receives the actual emission angle, emission direction unit vector, and joint effective weight output by the joint calibration and compensation unit, and the radial wind speed output by the coherent receiving and solving unit. The wind parameter inversion unit acquires the radial wind speed and emission direction unit vector corresponding to at least three current scanning directions, establishes wind vector observation relationships based on the radial wind speed and emission direction unit vector, and solves for the wind vector to be inverted based on multiple wind vector observation relationships.

[0050] In one implementation, the wind parameter inversion unit uses a least squares approach to solve for the wind vector to be inverted. In another implementation, the wind parameter inversion unit uses a weighted least squares approach to solve for the wind vector to be inverted, where the weight of each current scanning direction is determined by a joint effective weight. For current scanning directions with higher joint effective weights, the corresponding radial wind speed has a greater impact on the wind parameter inversion; for current scanning directions with lower joint effective weights, the corresponding radial wind speed has a smaller impact on the wind parameter inversion.

[0051] The wind parameter inversion unit can also select different inversion outputs according to the wind measurement mode. When the combination of scanning directions meets the three-dimensional inversion conditions, the wind parameter inversion unit outputs three-dimensional wind field information; when the combination of scanning directions only meets the planar inversion conditions, the wind parameter inversion unit outputs wind speed and wind direction; when the system only measures a single current scanning direction, the wind parameter inversion unit outputs the radial wind speed of that current scanning direction.

[0052] In one specific workflow, a passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling operates according to the following steps.

[0053] The wavelength controller reads the preset scan sequence and sends the first wavelength tuning command to the narrow-linewidth tunable laser. The narrow-linewidth tunable laser then outputs a narrow-linewidth laser beam at the corresponding wavelength.

[0054] The fiber optic beam splitter splits the narrow-linewidth laser into emitted light and local oscillator light. The acousto-optic modulator pulses the emitted light and provides the acousto-optic frequency shift to the coherent receiving and processing unit.

[0055] The sampling beam splitter separates the sampled light from the emitted light before it enters the dispersive grating scanning unit, and the wavelength measuring device obtains the actual wavelength of the emitted light based on the sampled light. At the same time, the temperature sensor obtains the grating temperature of the dispersive grating scanning unit and sends the grating temperature as a grating state parameter to the joint calibration and compensation unit.

[0056] The joint calibration and compensation unit queries the joint calibration table based on the actual wavelength of the emitted light and the grating state parameters, or determines the actual emission angle according to the grating diffraction relationship, and further determines the unit vector of the emission direction and the Doppler velocity conversion factor.

[0057] The pulse-modulated emitted light enters the collimating optical component, and after collimation, it is incident on the dispersion grating. The dispersion grating deflects the emitted light, and the emission optical component shapes the dispersion-deflected emitted light into a scanning beam and emits it into the atmospheric detection area.

[0058] When the scanning beam encounters atmospheric aerosols, it generates atmospheric backscattered echo signals. The receiving optics receive these backscattered echo signals and, along with the local oscillator beam, send them to a photodetector for beat frequency processing. The frequency calculation module extracts the beat frequency from the beat frequency signal.

[0059] The coherent receiving and processing unit determines the Doppler frequency shift based on the beat frequency and the acousto-optic frequency shift, and calculates the radial wind speed based on the Doppler velocity conversion factor corresponding to the current scanning direction.

[0060] The wavelength controller switches to the next wavelength tuning command, repeating the above process until the actual emission angle, emission direction unit vector, and radial wind speed corresponding to multiple current scanning directions are obtained. The wind parameter inversion unit inverts the wind parameter information based on the actual emission angle and radial wind speed corresponding to multiple current scanning directions.

[0061] In a preferred embodiment, refer to Figure 2 The wind parameter inversion unit feeds back the joint effective weights to the wavelength controller. The wavelength controller adjusts the dwell time in the preset scan sequence based on the joint effective weights. For the current scan direction with a low joint effective weight, it indicates that there may be a problem such as a weak atmospheric backscattered echo signal, a large deviation in the actual wavelength of the emitted light, or a deviation of the grating state parameters from the calibration state. The wavelength controller can extend the dwell time corresponding to the current scan direction or repeat the current scan direction in the next scan.

[0062] The adaptive dwell time can be determined as follows: ; in, This indicates the dwell time of the i-th current scan direction in the next scan round; Indicates the baseline dwell time; This represents the joint effective weight for the i-th current scan direction; This represents the radial wind speed fluctuation in the i-th current scanning direction during continuous scanning; and These represent the adjustment coefficients corresponding to the joint effective weight and radial wind speed fluctuation, respectively. Indicates the minimum stay time; Indicates the maximum length of stay; This means that the calculation results will be limited to between the minimum and maximum dwell times.

[0063] In this way, the system can dynamically adjust the sampling resources of each current scanning direction according to the actual wind measurement quality without adding a mechanical scanning mechanism, thereby improving the reliability of radial wind speed in the direction of weak echo or strong turbulence.

[0064] In one implementation, the joint calibration table is established at the factory. The establishment process includes: placing the dispersive grating scanning unit in a reference mounting state; controlling the narrow-linewidth tunable laser to sequentially output multiple preset wavelengths; measuring the actual emission angle corresponding to each preset wavelength using an external angle measuring device; simultaneously recording the actual wavelength of the emitted light output by the wavelength monitoring unit and the grating state parameters output by the grating state monitoring unit; calculating the unit vector of the emission direction based on the actual emission angle; determining the Doppler velocimetry conversion factor based on the actual wavelength of the emitted light; and finally forming the joint calibration table.

[0065] In another implementation, the joint calibration table can be calibrated a second time after on-site installation. During on-site calibration, a fixed reflecting target or a reference scattering area with a known direction can be set, the system can output multiple preset wavelengths, and the actual emission angle in the joint calibration table can be corrected according to the actual echo direction or the direction of the reference target.

[0066] In another implementation, the joint calibration table can be self-updated during operation. When a current scanning direction consistently has a high joint effective weight across multiple scans, and its radial wind speed meets a preset consistency condition with the inversion results of adjacent current scanning directions, the joint calibration compensation unit uses the actual wavelength of the emitted light, grating state parameters, actual emission angle, unit vector of the emission direction, and Doppler velocimetry conversion coefficient corresponding to that current scanning direction as candidate update data. After multiple accumulations and stability checks, the candidate update data is written into the joint calibration table or used to correct the interpolation parameters in the joint calibration table.

[0067] By updating the joint calibration table, the system can adapt to the slow thermal drift, installation stress changes, and optical component aging generated by the dispersive grating scanning unit during long-term operation, thereby improving the long-term wind measurement stability.

[0068] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling, characterized in that, include: A tunable laser unit is used to output multiple narrow-linewidth lasers of different wavelengths; The beam splitting modulation unit is used to split the narrow linewidth laser into emitted light and local oscillator light, and to pulse modulate the emitted light; A dispersive grating scanning unit is used to receive the pulse-modulated emitted light and to make the emitted light of different wavelengths form scanning beams with different emission directions; The wavelength monitoring unit is used to obtain the actual wavelength of the emitted light before it enters the dispersive grating scanning unit; A grating state monitoring unit is used to acquire the grating state parameters of the dispersive grating scanning unit; The joint calibration and compensation unit is used to determine the actual emission angle of the scanning beam based on the actual wavelength of the emitted light and the grating state parameters, and to determine the Doppler velocity conversion coefficient corresponding to the scanning beam based on the actual wavelength of the emitted light. The coherent receiving and processing unit is used to receive the atmospheric backscattered echo signal corresponding to the scanning beam, perform beat frequency processing on the atmospheric backscattered echo signal and the local oscillator light to obtain the beat frequency, and calculate the radial wind speed in the current scanning direction based on the Doppler velocity conversion coefficient and the beat frequency. The wind parameter inversion unit is used to invert wind parameter information based on the actual emission angle and radial wind speed corresponding to multiple current scanning directions.

2. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 1, characterized in that, The tunable laser unit includes a narrow linewidth tunable laser and a wavelength controller; The wavelength controller is used to send wavelength tuning commands to the narrow linewidth tunable laser according to a preset scanning sequence. The narrow linewidth tunable laser is used to output the plurality of narrow linewidth lasers of different wavelengths according to the wavelength tuning command.

3. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 1, characterized in that, The beam splitting and modulation unit includes an optical fiber beam splitter and an acousto-optic modulator; The fiber optic beam splitter is used to split the narrow linewidth laser into the emitted light and the local oscillator light; The acousto-optic modulator is used to pulse-modulate the emitted light and provide the acousto-optic frequency shift to the coherent receiving and processing unit.

4. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 1, characterized in that, The dispersive grating scanning unit includes a collimating optical component, a dispersive grating, and an emitting optical component; The collimating optical component is used to collimate the pulse-modulated emitted light. The dispersion grating is used to perform dispersion deflection on the aligned emitted light; The emission optical component is used to shape the dispersion-deflected emitted light into the scanning beam. The dispersive grating scanning unit does not have any mechanical rotating parts.

5. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 1, characterized in that, The wavelength monitoring unit includes a sampling spectrometer and a wavelength measuring device; The sampling beam splitter is disposed between the beam splitting modulation unit and the dispersion grating scanning unit, and is used to separate the sample light from the emitted light before it enters the dispersion grating scanning unit; The wavelength measuring device is used to obtain the actual wavelength of the emitted light based on the sampled light.

6. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 1, characterized in that, The grating status monitoring unit includes a temperature sensor; The temperature sensor is used to obtain the grating temperature of the dispersive grating scanning unit; The grating state parameters include the grating temperature; The joint calibration compensation unit is used to perform temperature correction on the grating period of the dispersive grating scanning unit according to the grating temperature, so as to obtain the temperature-corrected grating period.

7. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 6, characterized in that, The joint calibration compensation unit stores a joint calibration table; The joint calibration table includes the correspondence between the preset wavelength, the actual wavelength of the emitted light, the grating state parameters, the actual emission angle, the unit vector of the emission direction, and the Doppler velocity conversion coefficient; The joint calibration compensation unit is used to query the joint calibration table based on the actual wavelength of the emitted light and the grating state parameters to obtain the actual emission angle, the unit vector of the emission direction, and the Doppler velocity conversion coefficient.

8. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 6, characterized in that, The joint calibration and compensation unit is also used to determine the diffraction direction of the scanning beam according to the grating diffraction relationship based on the actual wavelength of the emitted light, the period of the temperature correction grating, the incident angle and the diffraction order, and to take the angle corresponding to the diffraction direction as the actual exit angle.

9. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 3, characterized in that, The coherent receiving and processing unit is used to determine the Doppler frequency shift based on the beat frequency and the acousto-optic frequency shift. The coherent receiving and solving unit is also used to determine the Doppler velocity conversion factor based on the actual wavelength of the emitted light, and to use the Doppler velocity conversion factor to convert the Doppler frequency shift to obtain the radial wind speed.

10. The passive solid-state beam scanning system based on wavelength tuning and dispersion grating coupling according to claim 7, characterized in that, The wind parameter inversion unit is used to obtain at least three radial wind velocities and the unit vector of the emission direction corresponding to the current scanning direction; The wind parameter inversion unit is also used to establish a wind vector observation relationship based on the radial wind speed and the unit vector of the launch direction, and to solve for the wind vector to be inverted based on multiple wind vector observation relationships; The wind parameter information includes at least one of wind speed, wind direction, and three-dimensional wind field information.

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