Multi-beam tilt error synchronous detection and correction method and system

Abstract

The application provides a multi-beam tilt error synchronous detection and correction method and system, in which, in a multi-beam common-aperture system, a sinusoidal intensity modulation with different frequencies is applied to each light beam to give each light beam a unique frequency domain identity tag. After the light beams are combined, a single four-quadrant detector receives and directly outputs a transverse differential signal, a longitudinal differential signal and a total light intensity signal; the three signals are fed into corresponding decoupling channels in parallel, in each channel, the three signals are sequentially subjected to band-pass filtering with the target frequency as the center, coherent demodulation with the same frequency reference signal and low-pass filtering to obtain a direct current component proportional to the tilt error of the corresponding light beam, then, the division normalization mechanism is combined, and the tilt angle of each light beam is reconstructed according to a linear mapping model to generate a tilt correction signal of each light beam to drive a corresponding tilt angle correction execution element, thereby realizing parallel closed-loop correction of multi-beam pointing.

Description

Technical Field

[0001] This invention relates to the field of beam combining and tilt control technology, and in particular to a method and system for synchronous detection and correction of multi-beam tilt errors. Background Technology

[0002] Multi-beam coaxial combining is a revolutionary paradigm that breaks through the physical limitations of single-aperture optical components and expands the brightness and power scale of laser beams. In cutting-edge fields such as space optical communication and directional energy transmission, the far-field focusing characteristics of the combined beam directly determine the final performance of the system. However, limited by platform mechanical chatter, thermal drift of optical components, and the thermal effects of high-power lasers themselves, dynamic spatiotemporal distortions inevitably accumulate during the transmission and spatial superposition of the various sub-beams. Among these, low-frequency dynamic tilt distortion (T-tilt) is the most significant factor leading to energy dispersion in the far-field combined beam and affecting the equivalent beam quality. The dominant factor causing severe degradation is the lack of a high-fidelity, disturbance-resistant multi-beam pointing closed-loop feedback system. Therefore, establishing a high-fidelity, disturbance-resistant multi-beam pointing closed-loop feedback system is the core foundation for supporting the practical application of multi-wavelength coaxial synthesis architecture.

[0003] Achieving high-precision pointing closed-loop in multi-beam systems hinges on the accurate sensing and separation of tilt distortion in each sub-beam. Traditional multi-wavelength combining systems typically rely on spatial physical isolation for channel splitting: cascading beam-splitting prisms or dichroic mirror arrays at the receiver separate spatially overlapping aliased beams by wavelength and feed them into independent detectors (such as quadrant detectors, QPDs) for individual measurement. While this physical beam-splitting architecture is intuitive, the number of optical components and detectors required at the receiver increases linearly with the number of combined beams, resulting in an extremely bulky optical system and extremely stringent alignment tolerances. More critically, physical separation disrupts the geometric symmetry of common-aperture detection, inevitably introducing non-common path errors (NCPE) and additional optical insertion loss. In real-world high-power operation or complex platform environments, even minute thermal deformations or mechanical drifts of the beam-splitting elements can translate into system-level static pointing deviations. Since this deviation is outside the closed-loop feedback loop, the system cannot effectively observe and compensate for it, thus limiting further improvement in the accuracy of multi-beam coaxial synthesis at the physical level.

[0004] To overcome the curse of dimensionality and non-co-path errors caused by physical isolation, co-aperture multiplexing sensing technology has gradually become a research hotspot for multi-beam pointing control. Wavefront-free sensing algorithms such as Stochastic Parallel Gradient Descent (SPGD) can achieve co-aperture optimization in a single-detector architecture. However, limited by the blind search mechanism and iterative convergence process of these algorithms, the error suppression bandwidth of such control systems is usually restricted to a low level, making it difficult to cope with typical platform mechanical flutter and sudden high-frequency disturbances in real-time engineering. In contrast, Frequency-division multiplexing (FDM, or LOCSET) provides a deterministic physical channel for spatiotemporal decoupling by mapping spatial or phase distortions to non-overlapping electrical carrier frequency bands. However, existing multi-channel FDM demodulation architectures heavily rely on high-frequency analog-to-digital converters (ADCs) and field-programmable gate arrays (FPGAs) for pure digital signal processing (such as digital quadrature demodulation or FFT filtering). Under such a system, high-frequency digital sampling and large-point digital filtering inevitably introduce significant pure computational delay. This pure delay erodes the phase margin of the servo control loop, which not only severely restricts the expansion of the system's closed-loop bandwidth, but also easily induces the "waterbed effect" of high-frequency noise amplification at the frequency band edge, thereby threatening the long-term dynamic stability of the synthesized beam pointing. Summary of the Invention

[0005] Multi-beam coaxial combining is a revolutionary paradigm for breaking through the brightness limit of single-aperture lasers, with high-fidelity tip-tilt control as its core foundation. However, traditional physical beam splitting architectures face limitations due to bloated optical links when the system is expanded, while co-aperture detection can cause severe spatial aliasing, resulting in the loss of intrinsic observability of tip-tilt errors. To address this underdetermined inversion problem, this invention provides a method and system for synchronous detection and correction of multi-beam tip-tilt errors.

[0006] The technical solution adopted in this invention is as follows: On the one hand, the present invention provides a method for synchronous detection and correction of multi-beam tilt error, comprising the following steps: emission Road beam, for the first The frequency of the road beam is applied. The intensity is modulated, and the intensity modulation frequencies of different beams are different, giving each beam a unique frequency domain identity label. ; Intensity modulated After beam combining, the beams are transmitted through a common aperture and received in the far field by a single four-quadrant detector. The transverse differential signal, longitudinal differential signal, and total light intensity signal are directly output through the four-quadrant detector. The transverse differential signal, longitudinal differential signal, and total light intensity signal are fed in parallel. The decoupling channel, the first The decoupling channel and the first Corresponding to the beam of light, in the first Within each decoupling channel, the transverse differential signal, longitudinal differential signal, and total light intensity signal are respectively processed at frequencies... Bandpass filtering is performed on the center; the three bandpass-filtered signals are multiplied by a reference signal with the same frequency as its intensity modulation to achieve coherent demodulation; low-pass filtering is then performed on the three coherently demodulated signals to extract the baseband components, thereby obtaining the signals corresponding to the first three signals. The beam's lateral tilt error, longitudinal tilt error, and the total light intensity are proportional to the lateral differential DC component, longitudinal differential DC component, and total DC component. Based on the transverse differential DC component, longitudinal differential DC component, and sum DC component corresponding to each beam, the tilt angle of each beam is reconstructed according to the linear mapping model; Based on the angle error between the tilt angle of each beam obtained from reconstruction and the target tilt angle, tilt correction signals for each beam are generated, driving the corresponding tilt angle correction actuators for each beam to achieve parallel closed-loop correction of the direction of each beam.

[0007] On the other hand, a multi-beam tilt error synchronous detection and correction system is provided, including: Light source module, emission road beam; Transmit modulation module, used for the first The frequency of the road beam is applied. The intensity is modulated, and the intensity modulation frequencies of different beams are different, giving each beam a unique frequency domain identity label. ; The beam combining and detection module includes a beam combiner and a four-quadrant detector. The beam combiner combines the intensity-modulated beams... After beam combining, the beams are transmitted through a common aperture and received by a four-quadrant detector in the far field. The transverse differential signal, longitudinal differential signal, and total light intensity signal are directly output through the four-quadrant detector. Parallel decoupling module, including A parallel decoupled channel feeds in parallel the lateral differential signal, the longitudinal differential signal, and the total optical intensity signal. The decoupling channel, the first The decoupling channel and the first Corresponding to the beam of light, among which the first The decoupling channels include: Three parallel bandpass filters are used to filter the transverse differential signal, longitudinal differential signal, and total light intensity signal by frequency. Perform bandpass filtering around the center; Three parallel multipliers are used to multiply the three bandpass filtered signals by their respective intensity-modulated reference signals; Three parallel low-pass filters are used to perform low-pass filtering on the signals output by the corresponding multipliers, extracting the baseband components, thereby obtaining the signals corresponding to the first multiplier. The beam's lateral tilt error, longitudinal tilt error, and the total light intensity are proportional to the lateral differential DC component, longitudinal differential DC component, and total DC component. The tilt reconstruction module is used to reconstruct the tilt angle of each beam based on the transverse differential DC component, longitudinal differential DC component, and sum DC component corresponding to each beam, and according to the linear mapping model. The closed-loop control module is used to generate tilt correction signals for each beam based on the angle error between the tilt angle of each beam obtained from reconstruction and the target tilt angle, and drive the corresponding tilt angle correction actuators for each beam to achieve parallel closed-loop correction of the direction of each beam.

[0008] Furthermore, the maximum number of beam paths that the system can support is:

[0009] in , , The detection bandwidth of the four-quadrant detector, the bandwidth of the tilt error signal, and the transition band width of the low-pass filter are respectively defined.

[0010] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method and system for synchronous detection and correction of multi-beam tilt errors. In a multi-beam shared-aperture system, sinusoidal intensity modulation with different frequencies is applied to each beam, assigning each beam a unique frequency domain identifier. After beam combining, a single four-quadrant detector (QPD) receives and directly outputs transverse differential signals, longitudinal differential signals, and a total intensity signal. These three signals are fed in parallel into corresponding decoupled channels. In each channel, the three signals are sequentially bandpass filtered around the target frequency, coherently demodulated with a reference signal of the same frequency, and low-pass filtered to obtain a DC component proportional to the tilt error of the corresponding beam. This is then combined with a division normalization mechanism and the tilt angle of each beam is reconstructed according to a linear mapping model to generate tilt correction signals for each beam, driving the corresponding tilt angle correction actuator to achieve parallel closed-loop correction of multi-beam pointing.

[0011] This invention can recover the independent tilt error of each beam with high fidelity from the composite signal output by a single four-quadrant detector and achieve disturbance suppression, thus significantly improving the quality of the synthesized beam. Attached Figure Description

[0012] 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.

[0013] Figure 1 This is a flowchart of a method for synchronous detection and correction of multi-beam tilt error provided in one embodiment; Figure 2 This is a schematic diagram of the structure of a multi-beam tilt error synchronous detection and correction system provided in one embodiment; Figure 3 This is a schematic diagram of the laser structure in one embodiment; Explanation of the labels in the diagram: 1. First laser; 2. Second laser; 3. First tilt angle correction actuator; 4. Second tilt angle correction actuator; 5. First high-reflection mirror; 6. Second high-reflection mirror; 7. Third high-reflection mirror; 8. Dichroic mirror; 9. Beam splitter; 10. Fourth high-reflection mirror; 11. Attenuating lens; 12. Four-quadrant detector; 13. Parallel decoupling module; 14. Closed-loop control module; 2-1 Seed source; 2-2 Modulation broadening device; 2-3 First stage amplification module; 2-4 Signal generator; 2-5 Transmit modulation module; 2-6 Second stage amplification module; 2-7 Third stage amplification module; 2-8 Forward pump source; 2-9 Forward pump combiner; 2-10 Master oscillator; 2-11 Backward pump combiner; 2-12 Backward pump source; 2-13 Collimator. Detailed Implementation

[0014] The technical solution of the present invention will now be clearly and completely described through specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0015] Reference Figure 1 A method for synchronous detection and correction of multi-beam tilt error includes the following steps: For common aperture transmission Each path in the beam is subjected to a sinusoidal intensity modulation with a unique modulation frequency, giving each beam a unique frequency domain identity label; Intensity modulated After beam combining, the beams are emitted through a common aperture and received in the far field by a single four-quadrant detector. The transverse differential signal, longitudinal differential signal, and total light intensity signal are directly output through the front-end hardware conditioning circuit of the four-quadrant detector. The transverse differential signal, longitudinal differential signal, and total light intensity signal are fed in parallel. The decoupling channel, the first The decoupling channel and the first Corresponding to the beam of light, in the first Within each decoupling channel, the transverse differential signal, longitudinal differential signal, and total intensity signal are sequentially subjected to bandpass filtering centered at their corresponding modulation frequencies, multiplication with a reference signal of the same frequency as their intensity modulation, and baseband component extraction, thereby obtaining the signals corresponding to the first, second, and third intensity signals. The beam's lateral tilt error, longitudinal tilt error, and the total light intensity are proportional to the lateral differential DC component, longitudinal differential DC component, and total DC component. Based on the transverse differential DC component, longitudinal differential DC component, and sum DC component corresponding to each beam, the tilt angle of each beam is reconstructed according to the linear mapping model; Based on the angle error between the tilt angle of each beam obtained from reconstruction and the target tilt angle, tilt correction signals for each beam are generated, driving the corresponding tilt angle correction actuators for each beam to achieve parallel closed-loop correction of the direction of each beam.

[0016] In the above embodiments, in a multi-beam common aperture system, it can be achieved by... Independent laser emission Road beam. Considering Each beam shares a common aperture and is incident on a single four-quadrant detector. To ensure that each beam possesses independent and distinguishable characteristics, different orthogonal high-frequency carrier waves are applied to each beam. Specifically, for the first... The beam is applied at a frequency of through an intensity modulator. The intensity is modulated, and the intensity modulation frequencies of different beams are different, giving each beam a unique frequency domain identity label. Specifically, regarding the first The frequency of the road beam is applied. Sinusoidal intensity modulation, the modulated light intensity signal The format is:

[0017] in, For the first The beam of light is The baseband light intensity distribution at any given time; For the first The modulation depth of the beam path satisfies ; For the first The modulation angular frequency of the beams is determined, and the modulation angular frequencies of different beams are different to ensure that the channels do not overlap in the frequency domain. Since the spectrum of physical tilt error is concentrated in the low-frequency region, this modulation mechanism is equivalent to orthogonally shifting the baseband spatial pose information to a frequency range where the baseband spatial pose information is at a lower frequency. A narrowband high-frequency channel centered on [the target audience].

[0018] Since the output current of the four-quadrant detector is proportional to the light intensity, the fourth... The beam path in the four-quadrant detector Quadrant ( The generated photocurrent can be strictly decomposed into a DC baseband component and a high-frequency modulation component:

[0019] in, Therefore, the output signal of the four-quadrant detector simultaneously contains two types of information in the time domain: the pure additive aliasing of the DC components of multiple beams, which remains an unsolvable coupled state after spatial computation; and information located at different modulation frequencies. The AC components at each frequency uniquely correspond to a specific beam. Thus, the tilt characteristics of each path are naturally separable in the spectrum.

[0020] Theoretically, the current in the four quadrants of a four-quadrant detector can be controlled. Channel separation is achieved by demodulating each signal separately. However, this architecture leads to cross-quadrant spread of thermal noise and shot noise during subsequent linear combination, exacerbating computational latency. To address this, this invention proposes an optimized decoupling architecture that directly performs coherent down-conversion on the three raw signals output from the four-quadrant detector's pre-amplifier hardware conditioning circuit: the lateral differential signal, the longitudinal differential signal, and the total optical intensity signal.

[0021] Under common aperture aliasing, the transverse differential signal Longitudinal differential signal and total light intensity signal They are respectively:

[0022]

[0023] in, For the first The beam of light is The absolute difference component of the transverse difference when time exists alone; For the first The beam of light is The absolute difference component of the longitudinal difference when time exists alone; For the first The beam of light is Total baseband power when it exists alone at a given moment.

[0024] As can be seen from the above expression, the original output signal of the four-quadrant detector contains two types of information: DC component: a weighted superposition of tilt errors of multiple beams, which cannot directly distinguish individual beams; AC modulation component: located at their respective modulation frequencies. Nearby, with the The tilt error of each beam corresponds one-to-one. Since the modulation frequencies of different beams are different, selective demodulation in the frequency domain can be used to convert the first beam into the second beam. The modulation component corresponding to the beam is separated from the mixed signal.

[0025] Next, the transverse differential signal Longitudinal differential signal and total light intensity signal Parallel feed The decoupling channel, the first The decoupling channel and the first The beam of light corresponds to the road beam. In the first... Within each decoupling channel, to achieve distortion-free signal separation, the transverse differential signal... Longitudinal differential signal and total light intensity signal By frequency Bandpass filtering is performed on the center; the three bandpass-filtered signals are multiplied by a reference signal with the same frequency as its intensity modulation to achieve coherent demodulation; low-pass filtering is then performed on the three coherently demodulated signals to extract the baseband components, thereby obtaining the signals corresponding to the first three signals. The beam's lateral tilt error, longitudinal tilt error, and the lateral differential DC component, longitudinal differential DC component, and total DC component are proportional to the total light intensity.

[0026] Specifically, within each decoupling channel, the transverse differential signal is first processed. Longitudinal differential signal and total light intensity signal By frequency Bandpass filtering centered on the target beam improves the signal-to-noise ratio (SNR) and suppresses DC coupling and inter-frequency interference from non-target beams, resulting in an output signal modulated only by the tilt of the target beam. The transverse differential signal, longitudinal differential signal, and total intensity signal obtained after bandpass filtering are as follows:

[0027] Suppose and the The reference signal for beam intensity modulation at the same frequency is ,in, For reference signal and the first Phase difference between the beam intensity modulation signals. Reference signal. With the first The intensity modulation signal applied by the beam is synchronously output by the same source waveform generator to achieve strict in-phase locking, so that the demodulation output and the tilt error satisfy a linear proportional relationship.

[0028] The transverse differential signal, longitudinal differential signal, and total light intensity signal obtained after bandpass filtering are multiplied by the reference signal, respectively. After multiplication, the spectrum is decomposed into DC component, second harmonic component, and higher harmonic component. Only the modulation component with the same frequency as the fundamental frequency of the reference signal produces a stable DC term after multiplication. The resulting transverse differential mixer signal is obtained. Longitudinal differential mixer signal and sum of mixed signals as follows:

[0029] Expanding the multiplied transverse differential mixer signal, longitudinal differential mixer signal, and summation mixer signal using trigonometric identities yields:

[0030] A cutoff frequency of is applied to the transverse differential mixer signal, the longitudinal differential mixer signal, and the summation mixer signal. Low-pass filtering to obtain the same as the first The beam tilt error is proportional to the lateral differential DC component. Longitudinal differential DC component Total DC component ,as follows:

[0031] Cutoff frequency satisfy , This represents the bandwidth of the tilt error signal. Therefore, components generated by other beams at different modulation frequencies and high-frequency terms are effectively filtered out during the low-pass filtering process, leaving only the target baseband coherent terms as output.

[0032] In one embodiment, the tilt angle of each beam is reconstructed based on the transverse differential DC component, longitudinal differential DC component, and summed DC component corresponding to each beam, according to a linear mapping model. Specifically, this includes: To eliminate the impact of light intensity fluctuations and channel gain fluctuations on measurement accuracy, the transverse and longitudinal differential DC components are normalized using the summed DC component. The modulation depth is used as a common multiplier to cancel each other out in the division operation, resulting in the transverse and longitudinal normalized error signals, as follows:

[0033] in , The first The beam of light is The transverse and longitudinal normalized error signals at each moment. The division normalization process has completely eliminated the influence of light intensity fluctuations and modulation depth differences at the physical level, and the error reconstruction signals of each beam have a high degree of linear consistency in terms of dimensions and response amplitude.

[0034] The tilt angles of each beam are reconstructed based on the linear mapping model, as follows:

[0035] in and These are the pre-calibrated horizontal and vertical calibration coefficients, respectively. , The first The beam of light is The method determines the lateral and longitudinal tilt angles at any given time. It avoids noise propagation caused by independent demodulation in a single quadrant and achieves high-fidelity reconstruction of multi-beam spatial pose signals.

[0036] There is a strict linear mapping relationship between the lateral normalized error signal and the lateral tilt angle, and between the longitudinal normalized error signal and the longitudinal tilt angle. By pre-calibrating, that is, applying a precisely known calibration tilt angle (lateral calibration tilt angle and longitudinal calibration tilt angle) to each beam in the system, and measuring the corresponding normalized error signal (lateral normalized error signal and longitudinal normalized error signal) after decoupling and normalization, the corresponding calibration coefficients, including the lateral calibration coefficient and the longitudinal calibration coefficient, can be calculated by linearly fitting the normalized error signals under multiple sets of different calibration tilt angles.

[0037] After completing the frequency domain decoupling and reconstruction of the multi-beam tilt error signal, the tilt angle error of each channel needs to be further introduced into the feedback loop to achieve synchronous stabilization of the multi-beam optical axis. Based on the angle error between the tilt angle of each beam and the target tilt angle obtained from the reconstruction, a tilt correction signal for each beam is generated, driving the corresponding tilt angle correction actuator for each beam to achieve parallel closed-loop correction of the beam direction. The type of tilt angle correction actuator described in this invention is not limited, and a tilting mirror can be used without loss of generality. This invention achieves parallel closed-loop correction of the beam direction by establishing independent tilt correction loops for each beam, wherein the independent tilt correction loops for each beam include, but are not limited to, generating tilt correction signals for each beam according to proportional-integral control algorithms and proportional-integral-derivative control algorithms respectively.

[0038] In another embodiment, a multi-beam tilt error synchronous detection and correction system is provided, comprising: Light source module, emission road beam; Transmit modulation module, used for the first The frequency of the road beam is applied. The intensity is modulated, and the intensity modulation frequencies of different beams are different, giving each beam a unique frequency domain identity label. ; The beam combining and detection module includes a beam combiner and a four-quadrant detector. The beam combiner combines the intensity-modulated beams... After beam combining, the beams are transmitted through a common aperture and received by a four-quadrant detector in the far field. The transverse differential signal, longitudinal differential signal, and total light intensity signal are directly output through the four-quadrant detector. Parallel decoupling module, including A parallel decoupled channel feeds in parallel the lateral differential signal, the longitudinal differential signal, and the total optical intensity signal. The decoupling channel, the first The decoupling channel and the first Corresponding to the beam of light, among which the first The decoupling channels include: Three parallel bandpass filters are used to filter the transverse differential signal, longitudinal differential signal, and total light intensity signal by frequency. Perform bandpass filtering around the center; Three parallel multipliers are used to multiply the three bandpass filtered signals by their respective intensity-modulated reference signals; Three parallel low-pass filters are used to perform low-pass filtering on the signals output by the corresponding multipliers, extracting the baseband components, thereby obtaining the signal with the same characteristics as the first multiplier. The beam tilt error is proportional to the transverse differential DC component, the longitudinal differential DC component, and the summation DC component; The tilt reconstruction module is used to reconstruct the tilt angle of each beam based on the transverse differential DC component, longitudinal differential DC component, and sum DC component corresponding to each beam, and according to the linear mapping model. The closed-loop control module is used to generate tilt correction signals for each beam based on the angle error between the tilt angle of each beam obtained from reconstruction and the target tilt angle, and drive the corresponding tilt angle correction actuators for each beam to achieve parallel closed-loop correction of the direction of each beam.

[0039] The choice of modulation frequency is the primary factor determining the orthogonal decoupling performance of multi-channel systems. To ensure crosstalk-free separation of tilt error signals in the frequency domain, the following constraints must be met: First, bandwidth constraints. Second, the modulation frequency spacing between each beam. It must be greater than the bandwidth of the tilt error signal. The transition band width of the pass filter The sum of .in Determined by the characteristics of the disturbance spectrum. This depends on the order and cutoff characteristics of the low-pass filter. Secondly, the bandwidth constraint of the four-quadrant detector must be considered. All modulation frequencies must be within the detection bandwidth of the four-quadrant detector. Within, i.e., the highest modulation frequency ,in The optical frequency of the first beam. For the first The optical frequency of the beam path. Finally, consider the channel capacity. Under the above constraints, the maximum number of beam paths the system can support is:

[0040] in , , The detection bandwidth of the four-quadrant detector, the bandwidth of the tilt error signal, and the transition band width of the low-pass filter are respectively considered. In a typical embodiment... kHz, kHz, At kHz, the system theoretically supports parallel detection of dozens of beams.

[0041] The expansion of the decoupling dimension of this system depends solely on the allocation of frequency domain bandwidth resources, without increasing the physical number of QPD detector arrays, demonstrating excellent architectural scalability and array adaptability.

[0042] Modulation depth This is a core parameter that determines the decoupling performance and operational stability of the system. According to the signal transmission model of the demodulation link, the estimated variance of the target channel tilt angle satisfies... From the perspective of suppressing high-frequency thermal noise, improve This can increase the proportion of carrier energy, thereby reducing measurement variance. However, in real physical systems, The selection is constrained by a dual boundary constraint: firstly, it must be strictly controlled. To ensure the linear response of electro-optic devices and detectors and avoid waveform distortion and harmonic crosstalk caused by overmodulation; secondly, excessive modulation can cause severe oscillations in baseband optical power. Therefore, in practical applications, a smaller modulation depth (such as within the range of 10% to 20%) is usually selected to achieve high-precision spatiotemporal decoupling while maintaining the stability of the baseband energy output of the main beam.

[0043] The closed-loop control module includes One controller and Each controller generates a tilt correction signal for the corresponding beam based on the angle error between the tilt angle of the corresponding beam obtained from reconstruction and the target tilt angle. This signal drives the tilt angle correction actuator corresponding to the beam, thereby achieving parallel closed-loop correction of the direction of each beam. The controller may include, but is not limited to, a proportional-integral linear controller.

[0044] Reference Figure 2 One embodiment provides a multi-beam tilt error synchronous detection and correction system, comprising: The light source module includes two lasers, namely the first laser 1 and the second laser 2, which are used to emit two beams. In this embodiment, only N=2 is used as an example for illustration, and the range of N is not limited thereto.

[0045] Each laser is equipped with an emission modulation module for controlling the emission of the first laser. The frequency of the road beam is applied. The intensity is modulated, and the intensity modulation frequencies of different beams are different, giving each beam a unique frequency domain identity label. Specifically, such as Figure 3 As shown, Figure 3 This is a schematic diagram of the optical path structure of a laser. Note that... Figure 3 This is an example of a laser structure. In practical applications, the specific structure of the laser is not limited; it can employ forward-pumped, backward-pumped, or bidirectional-pumped structures. The specific amplification cascade structure is also unrestricted, as long as it contains an emission modulation module. (Refer to...) Figure 3 Its laser includes a seed source 2-1, a modulation broadening device 2-2, a first-stage amplification module 2-3, a signal generator 2-4, an emission modulation module 2-5, a second-stage amplification module 2-6, a third-stage amplification module 2-7, a forward pump source 2-8, a forward pump combiner 2-9, a master oscillator 2-10, a backward pump combiner 2-11, a backward pump source 2-12, and a collimator 2-13. The seed light generated by seed source 2-1 is pre-amplified by modulation and broadening device 2-2 and then by first-stage amplification module 2-3. Under the control of signal generator 2-4, emission modulation module 2-5 applies intensity modulation of the beam at a set frequency. After intensity modulation, the beam passes through second-stage amplification module 2-6 and third-stage amplification module 2-7 and then enters main oscillator 2-10 through forward pump combiner 2-9. Main oscillator 2-10 is a bidirectional pumping structure, including forward pump source 2-8, forward pump combiner 2-9, backward pump combiner 2-11, and backward pump source 2-12. The output beam of main oscillator 2-10 is output after collimation 2-13.

[0046] The beam combining and detection module includes a beam combiner and a four-quadrant detector 12. The beam combiner combines the intensity-modulated beams... After beam combining, the beams are transmitted through a common aperture and received in the far field by a four-quadrant detector 12. The four-quadrant detector 12 directly outputs the transverse differential signal, the longitudinal differential signal, and the total light intensity signal.

[0047] Reference Figure 2In this embodiment, the beams output by the first laser 1 and the second laser 2 correspond to the first tilt angle correction actuator 3 and the second tilt angle correction actuator 4, respectively. The beam output by the first laser 1 passes through the first tilt angle correction actuator 3, the first high-reflection mirror 5, and the third high-reflection mirror 7 before being incident on the dichroic mirror 8. The beam output by the second laser 2 passes through the first tilt angle correction actuator 4 and the second high-reflection mirror 6 before being incident on the dichroic mirror 8. The dichroic mirror 8 combines the two beams and then incident them on the beam splitter 9. Most of the laser power is reflected by the beam splitter and output as the main beam, while the remaining small portion of the laser power is reflected by the fourth high-reflection mirror 10 and then incident on the four-quadrant detector 12 after passing through the attenuation lens 11.

[0048] Parallel decoupling module 13 includes two parallel decoupling channels. The lateral differential signal, longitudinal differential signal, and total light intensity signal are fed into the two decoupling channels in parallel. The decoupling channel and the first Corresponding to the beam of light, among which the first The decoupling channels include: Three parallel bandpass filters are used to filter the transverse differential signal, longitudinal differential signal, and total light intensity signal by frequency. Perform bandpass filtering around the center; Three parallel multipliers are used to multiply the three bandpass filtered signals by their respective intensity-modulated reference signals; Three parallel low-pass filters are used to perform low-pass filtering on the signals output by the corresponding multipliers, extracting the baseband components, thereby obtaining the signal with the same characteristics as the first multiplier. The beam tilt error is proportional to the transverse differential DC component, the longitudinal differential DC component, and the summation DC component; The tilt reconstruction module is used to reconstruct the tilt angle of each beam based on the transverse differential DC component, longitudinal differential DC component, and sum DC component corresponding to each beam, and according to the linear mapping model. The closed-loop control module 14 is used to generate tilt correction signals for each beam based on the angle error between the tilt angle of each beam obtained by reconstruction and the target tilt angle, drive the tilt angle correction actuator corresponding to each beam, and realize parallel closed-loop correction of the direction of each beam.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for synchronous detection and correction of multi-beam tilt error, characterized in that, Includes the following steps: emission Road beam, for the first The frequency of the road beam is applied. The intensity is modulated, and the intensity modulation frequencies of different beams are different, giving each beam a unique frequency domain identity label. ; Intensity modulated After beam combining, the beams are transmitted through a common aperture and received in the far field by a single four-quadrant detector. The transverse differential signal, longitudinal differential signal, and total light intensity signal are directly output through the four-quadrant detector. The transverse differential signal, longitudinal differential signal, and total light intensity signal are fed in parallel. The decoupling channel, the first The decoupling channel and the first Corresponding to the beam of light, in the first Within each decoupling channel, the transverse differential signal, longitudinal differential signal, and total light intensity signal are respectively processed at frequencies... Bandpass filtering is performed on the center; the three bandpass-filtered signals are multiplied by a reference signal with the same frequency as its intensity modulation to achieve coherent demodulation; low-pass filtering is then performed on the three coherently demodulated signals to extract the baseband components, thereby obtaining the signals corresponding to the first three signals. The beam's lateral tilt error, longitudinal tilt error, and the total light intensity are proportional to the lateral differential DC component, longitudinal differential DC component, and total DC component. Based on the transverse differential DC component, longitudinal differential DC component, and sum DC component corresponding to each beam, the tilt angle of each beam is reconstructed according to the linear mapping model; Based on the angle error between the tilt angle of each beam obtained from reconstruction and the target tilt angle, tilt correction signals for each beam are generated, driving the corresponding tilt angle correction actuators for each beam to achieve parallel closed-loop correction of the direction of each beam.

2. The method for synchronous detection and correction of multi-beam tilt error according to claim 1, characterized in that, For the The frequency of the road beam is applied. Sinusoidal intensity modulation, the modulated light intensity signal The format is: in, For the first The beam of light is The baseband light intensity distribution at any given time; For the first The modulation depth of the beam path satisfies ; For the first The modulation angular frequency of the beam, and the modulation angular frequencies of different beams are different.

3. The method for synchronous detection and correction of multi-beam tilt error according to claim 2, characterized in that, Lateral differential signal Longitudinal differential signal and total light intensity signal They are respectively: in, For the first The beam of light is The absolute difference component of the transverse difference when time exists alone; For the first The beam of light is The absolute difference component of the longitudinal difference when time exists alone; For the first The beam of light is Total baseband power when it exists alone at a given moment.

4. The method for synchronous detection and correction of multi-beam tilt error according to claim 3, characterized in that, Coherent demodulation is achieved by multiplying the three bandpass filtered signals respectively by a reference signal modulated at the same frequency as its intensity modulation, including: The transverse differential signal, longitudinal differential signal, and total light intensity signal obtained after bandpass filtering are as follows: Suppose and the The reference signal for beam intensity modulation at the same frequency is ,in, For reference signal and the first The phase difference between the beam intensity modulation signals; The transverse differential signal, longitudinal differential signal, and total light intensity signal obtained after bandpass filtering are multiplied by the reference signal, and the three multiplied signals are expanded using trigonometric identities to obtain the transverse differential mixing signal. Longitudinal differential mixer signal and sum of mixed signals .

5. The method for synchronous detection and correction of multi-beam tilt error according to claim 4, characterized in that, Reference signal With the first The intensity modulation signal applied by the beam is synchronously output by the same source waveform generator to achieve strict in-phase locking, so that the demodulation output and the tilt error satisfy a linear proportional relationship.

6. The method for synchronous detection and correction of multi-beam tilt error according to claim 4, characterized in that, A cutoff frequency of is applied to the transverse differential mixer signal, the longitudinal differential mixer signal, and the summation mixer signal. Low-pass filtering to obtain the same as the first The beam tilt error is proportional to the lateral differential DC component. Longitudinal differential DC component Total DC component ,as follows: Cutoff frequency satisfy , This represents the bandwidth of the tilt error signal.

7. The method for synchronous detection and correction of multi-beam tilt error according to claim 4, characterized in that, Based on the transverse differential DC component, longitudinal differential DC component, and summed DC component corresponding to each beam, and reconstructing the tilt angle of each beam according to the linear mapping model, including: The transverse and longitudinal differential DC components are normalized using the summed DC component to obtain the transverse normalized error signal and the longitudinal normalized error signal, as follows: in , The first The beam of light is The horizontal normalized error signal and the vertical normalized error signal at time t; The tilt angles of each beam are reconstructed based on the linear mapping model, as follows: in and These are the pre-calibrated horizontal and vertical calibration coefficients, respectively. , The first The beam of light is The horizontal tilt angle and the vertical tilt angle at any given moment.

8. The method for synchronous detection and correction of multi-beam tilt error according to claim 4, characterized in that, The tilt angle correction actuator is a tilt mirror.

9. A multi-beam tilt error synchronous detection and correction system, characterized in that, include: Light source module, emission road beam; Transmit modulation module, used for the first The frequency of the road beam is applied. The intensity is modulated, and the intensity modulation frequencies of different beams are different, giving each beam a unique frequency domain identity label. ; The beam combining and detection module includes a beam combiner and a four-quadrant detector. The beam combiner combines the intensity-modulated beams... After beam combining, the beams are transmitted through a common aperture and received by a four-quadrant detector in the far field. The transverse differential signal, longitudinal differential signal, and total light intensity signal are directly output through the four-quadrant detector. Parallel decoupling module, including A parallel decoupled channel feeds in parallel the lateral differential signal, the longitudinal differential signal, and the total optical intensity signal. The decoupling channel, the first The decoupling channel and the first Corresponding to the beam of light, among which the first The decoupling channels include: Three parallel bandpass filters are used to filter the transverse differential signal, longitudinal differential signal, and total light intensity signal by frequency. Perform bandpass filtering around the center; Three parallel multipliers are used to multiply the three bandpass filtered signals by their respective intensity-modulated reference signals; Three parallel low-pass filters are used to perform low-pass filtering on the signals output by the corresponding multipliers, extracting the baseband components, thereby obtaining the signals corresponding to the first multiplier. The beam's lateral tilt error, longitudinal tilt error, and the total light intensity are proportional to the lateral differential DC component, longitudinal differential DC component, and total DC component. The tilt reconstruction module is used to reconstruct the tilt angle of each beam based on the transverse differential DC component, longitudinal differential DC component, and sum DC component corresponding to each beam, and according to the linear mapping model. The closed-loop control module is used to generate tilt correction signals for each beam based on the angle error between the tilt angle of each beam obtained from reconstruction and the target tilt angle, and drive the corresponding tilt angle correction actuators for each beam to achieve parallel closed-loop correction of the direction of each beam.

10. The multi-beam tilt error synchronous detection and correction system according to claim 9, characterized in that, The maximum number of beam paths that the system can support is: in , , The detection bandwidth of the four-quadrant detector, the bandwidth of the tilt error signal, and the transition band width of the low-pass filter are respectively defined.

Images